Method for more effective data transmission in an optical telecommunication network in wavelength multiplex operation of optical wavelengths, wherein the optical telecommunication network has one super ordinate network node, a second superordinate network node and a plurality of network elements, optical telecommunication network, computer program and computer program product

State of the art

0001The invention relates to a method for more efficient data transmission in an optical telecommunications network in wavelength division multiplex (WDM) operation of different optical wavelengths, the optical telecommunications network having a first superordinate network node, a second superordinate network node and also a plurality of network elements .

0002The invention also relates to an optical telecommunications network for more efficient data transmission in wavelength division multiplex (WDM) operation of different optical wavelengths, the optical telecommunications network having a first superordinate network node, a second superordinate network node and also a plurality of network elements.

0003The invention also relates to a computer program with program code means and a computer program product with a computer-readable medium and a computer program stored on the computer-readable medium, which are suitable for carrying out all steps of the method according to the invention.

0004Methods for transmitting data using optical fibers, ie using optical telecommunications networks, are generally known. For example, it applies to many broadband telecommunication networks that the majority of the data to be transmitted is transmitted via optical data transmission systems or optical telecommunication networks, in particular using optical waveguides. Such optical telecommunication networks are used, for example, in aggregation networks. Such aggregation networks, for example for private customer traffic, have the task of routing traffic from regional nodes to backbone nodes.

0005It is generally known to use filterless splitters and couplers in an open horseshoe topology (horseshoe topology) on the optical level in aggregation networks according to the state of the art, or to use optical add / drop nodes with fixed spectral settings ( English FOADM, Fixed Optical Add / Drop Multiplexer) with an inherent filter functionality, also in an open horseshoe topology. Both variants can be implemented cost-effectively, the second variant allowing the reuse of a wavelength, but having comparatively little flexibility with regard to changing traffic requirements.

0006The ring closure represents an improvement over the topologies described, because there is then in principle always a path to the destination even in the event of a fault in the optical telecommunications network. The consequence of this, however, is that the ring has to be physically interrupted at at least one point on each wavelength, otherwise a "laser" effect can occur in the ring equipped with amplifiers. Such an interruption can be implemented with highly attenuating filters in reconfigurable optical add / drop nodes (ROADM, Reconfigurable Optical Add / Drop Multiplexer).

0007It is also known when operating such aggregation networks that the backbone network (or core network) is operated in an A&B network structure - or with a duplicated structure. From the point of view of the Internet protocol level or Internet protocol layer, this has significant advantages, because both networks (or Backbone networks) protect each other: the A (backbone) network is located behind a first higher-level network node (of the optical telecommunications network), for example, and the A (backbone network) is located behind a second higher-level network node (of the optical telecommunications network) ) symmetrically structured B (backbone) network.

0008With the present symmetry in the backbone network, it has proven to be useful that any (subordinate) network node of the optical telecommunications network is connected to both the first higher-level network node and the second higher-level network node.

0009An operation of such an aggregation network with the aim of the highest possible failure safety provides that in addition to the operationally used part of the data transmission (between a data sending and a data receiving node) of the ring-shaped fiber optic link (working path) in the event of an error (ie For example, in the event of a fiber break on the operationally used part of the fiber optic ring), the remaining part of the ring-shaped fiber optic link (backup path) is used to transfer the data between the nodes involved.

0010Furthermore, with a view to the highest possible failure safety in the event of the use of a duplicated backbone network (i.e. in comparison to the higher-level network nodes of the optical telecommunications network (or optical ring) further higher-level network nodes) in previously known systems usually required that the first part of the optical telecommunication network (i.e., which is used operationally for data transmission between a (subordinate) network element (of the optical telecommunications network under consideration) on the one hand and the first higher-level network node on the other hand the ring-shaped fiber optic link) for data transmission between the same (subordinate) network element on the one hand and the second higher-level network node on the other hand is not used in normal operational cases (but only in the event of a fault), i.e. in the event of a fiber break, for example, but that on the contrary for data transmission ( user data of the same network element) from resp. to the second superordinate network node, a second part of the optical telecommunications network (ie the ring-shaped fiber optic link) which differs from the first part of the optical telecommunications network or is disjunct from it is normally used for this data transmission.

0011Such an operation of an optical telecommunication network, however, usually leads to insufficient utilization of the available bandwidth of the aggregation network, especially as soon as optical interfaces (transponders, transceivers) are used with a data rate adapted to the length of the route, so-called flex-rate transceivers.

0012Furthermore, from the document <patcit id="pcit0001" dnum="EP2940911A1"><text>EP 2 940 911 A1</text></patcit> a method is known in which higher-level network nodes have wavelength-selective switches. Optical signals are, however, divided into a transit path and a drop path. Furthermore, from the publication<patcit id="pcit0002" dnum="EP0903882A2"><text>EP 0903 882 A2</text></patcit> a WDM ring network with provisions to prevent a ring closure and thus the oscillation caused by the laser effect. The pamphlet<patcit id="pcit0003" dnum="US2004109686A1"><text>US 2004 109 686 A1</text></patcit> discloses a metro optical network.

Disclosure of the invention

0013The invention is based on the object of providing a method and an optical telecommunications network, as well as a computer program and a computer program product, which utilize the bandwidth resources as optimally as possible and thus a higher one under otherwise identical conditions - in particular with regard to the investment required for the components of the optical telecommunications network Performance (in the sense of an overall higher, usable data transport capacity) with at the same time not or only insignificantly reduced failure safety against faults such as fiber breaks or the like.

0014This object is achieved according to the invention by a method for more efficient data transmission in an optical telecommunications network in wavelength division multiplex (WDM) operation of different optical wavelengths according to claim 1 of the present invention.

0015It is thereby advantageously possible according to the present invention that the normal case (ie available data transmission bandwidth can be improved without a faulty impairment of the optical telecommunications network by the fact that both in normal operation and in a fault operating state (of several fault operating states, which relate in particular to fiber breaks, which can occur between two (subordinate) network elements or between a subordinate network element and a higher-level network node or between two higher-level network nodes) the specified transmission capacity between the various network elements or network nodes can be implemented. In this way, according to the invention, advantages can be realized in particular compared to an operation of the optical telecommunication network in which it is required that the first part of the optical telecommunication network, which is operationally used for data transmission between a (subordinate) network element of the optical telecommunication network under consideration on the one hand and the first higher-level network node on the other hand, for data transmission between the same (subordinate) network element on the one hand and the second higher-level network node on the other hand, is not normally operational is being used, but that in the normal case for this data transmission (from or to the second higher-level network node) a second part of the optical telecommunication network is used, which differs from the first part of the optical telecommunication network or is disjoint from it and usually longer and therefore achieves low performance .

0016According to the invention, it is provided that the optical telecommunication network is a ring-shaped closed optical transmission path (ie in the form of an optical ring or a ring of a fiber optic link or Fiber optic line), the optical telecommunications network having a first higher-level network node, a second higher-level network node and also a plurality of network elements, the plurality of network elements having at least a first network element and a second network element. Due to the ring closure, according to the invention it is advantageously possible that even in the event of a fault (ie For example, in the case of a fiber optic line interrupted at one point) there is always a (non-faulty) way to carry out the data transmission between the respective source of the data and the respective destination of the data. According to the invention, it must be ensured that the optical ring is physically interrupted at one point on each wavelength, since otherwise interference or a "laser" effect will occur in the ring equipped with amplifiers. According to the invention, this interruption is ensured in that the first higher-level network node has a first wavelength-selective switch (WSS) and a second wavelength-selective switch, the first and second wavelength-selective switches each next to an input (which is connected to the optical transmission link ) have individual outputs (hereinafter also referred to as first outputs), wherein the outputs of the first and second wavelength selective switches are coupled to one another. As a result, the ring closure in the optical telecommunication network can be established in a way that ensures that no wavelength used in the optical telecommunication network is fed in or out from the first wavelength-selective switch as well as from the second wavelength-selective switch at a considered output (the wavelength-selective switch). is coupled. This is possible because the wavelength-selective switches can be set or configured in such a way that for each of the outputs and each of the input-side (at the wavelength-selective switch) applied wavelengths (or "colors" used for optical data transmission) this wavelength either at the output under consideration applied or not. In other words, this means that the setting of the first and second wavelength-selective switch is carried out according to the invention in such a way that on a coupled output of both wavelength-selective switches each wavelength used is only coupled either from the first wavelength-selective switch or from the second wavelength-selective switch - but not from two wavelength-selective switches simultaneously. In this way, according to the invention, it is advantageously possible that interference effects or the laser effect are avoided and yet it is ensured for the normal operating mode of the optical telecommunications network that from any point on the optical transmission path (ie from any network element or higher-level network node) any other point of the optical transmission link using the same wavelength can be reached both via the shortest connection link of the optical transmission link and using the complementary (i.e. disjoint to the shortest link) link of the ring-shaped optical transmission link - i.e. in opposite directions, and that for each failure mode of operation (ie in particular for cases of a fiber break at any point on the ring-shaped optical transmission path) at least one of these paths (ie either the shortest connection path or the complementary connection path) can be used.

0017According to the invention, it is provided according to an alternative embodiment that the first wavelength-selective switch and the second wavelength-selective switch are implemented (together) as a twin wavelength-selective switch pair in such a way that the first wavelength-selective switch corresponds to the first wavelength-selective switch functionality of the twin wavelength-selective switch pair, while the second wavelength-selective switch corresponds to the second wavelength-selective switch functionality of the twin wavelength-selective switch pair. Correspondingly, according to this alternative embodiment, the first higher-level network node has the first wavelength-selective switch functionality (of the twin wavelength-selective switch pair) with respect to the first and third signal path and the second wavelength-selective switch functionality (of the twin wavelength-selective switch pair) with respect to the second and fourth signal path, wherein the first and second wavelength-selective switch functionalities have first outputs such that each of the first outputs is assigned to one of the plurality of operating modes of the optical telecommunication network. The same applies (with regard to the twin wavelength-selective switch pair) at all points where the first wavelength-selective switch or the second wavelength-selective switch is mentioned in the context of the present patent application.

0018Typically, the optical telecommunications network or the fiber optic ring has a large number of network elements, which are also referred to as so-called R1 routers or (regional) aggregation nodes and, for a specific region, the connection of the network elements arranged below in the (network) hierarchy to the backbone network. The optical telecommunication network also has the first superordinate network node and the second superordinate network node. These network nodes are also referred to as R2 routers or backbone routers. Due to the fact that the first and second higher-level network nodes are part of the optical telecommunications network or part of the optical transmission path, it is advantageously possible according to the invention that the backbone network (or core network) is in an A&amp;B network structure - or with a doubled structure - is operated. From the point of view of the Internet protocol level or Internet protocol layer advantageously allows both networks (or backbone networks) to protect each other: the A (backbone) network and, for example, are located behind a first higher-level network node (of the optical telecommunications network or the optical transmission path) behind a second higher-level network node (of the optical telecommunications network or the optical transmission path) is the symmetrically constructed B (backbone) network (to the A backbone network).

0019This also makes it possible in an advantageous manner that the duplicated connection of the aggregation nodes (ie each of the (plurality or plurality of) R1 routers) to two R2 routers (ie the "dual homing" principle) is not affected. In such a case, traffic relations generally only exist between the aggregation node (or R1 router) under consideration and the first higher-level network node (first R2 router) or the second higher-level network node (second R2 router) on the other hand. In particular, there is no direct relationship between the aggregation nodes (R1 nodes or R1 routers) themselves. The fiber topology of the optical transmission link itself is bidirectional.

0020According to the invention, the telecommunications network has the optical transmission path as a topologically closed ring (and bidirectional, ie on each route section bi-directionally usable optical transmission path that the optical transmission link directly or indirectly connects the first superordinate network node and the first network element as well as the first network element and the second network element as well as the second network element and the second superordinate network node and that the optical transmission link also the first superordinate network node and the second superordinate Connects network nodes together. This is done according to the invention via the optical transmission link<ul id="ul0001" list-style="none" compact="compact"><li>- A first signal path is defined from the first network element to the first higher-level network node,</li><li>- A second signal path is defined from the first network element to the second superordinate network node, the second signal path additionally running from the second superordinate network node to the first superordinate network node,</li><li>- Defined and a third signal path from the second network element to the first superordinate network node</li><li>- A fourth signal path is defined from the second network element to the second superordinate network node, the fourth signal path additionally running from the second superordinate network node to the first superordinate network node,</li></ul>wherein the first and second signal path as well as the third and fourth signal path are each disjoint on the optical transmission link and each complement one another to form the optical transmission link (ie are complementary) and wherein a first optical signal (using a first wavelength or "Color") from the first network element to the first superordinate network node via the first signal path as well as the second signal path and a second optical signal (using a second wavelength or "color") from the second network element to the first superordinate network node both via the third Signal path and is transmitted via the fourth signal path.

0021According to the invention it is provided in particular that the optical telecommunication network is symmetrical with regard to the first and second superordinate network node, ie the roles of the first and second superordinate network node can in particular be interchanged or Analog to the first, second, third and fourth signal path, another first signal path runs from the first network element to the second superordinate network node, a further second signal path from the first network element to the first superordinate network node, the further second signal path also from the first superordinate network node to the second higher-level network node runs, a further third signal path from the second network element to the second superordinate network node and a further fourth signal path from the second network element to the first superordinate network node, the further fourth signal path additionally running from the first superordinate network node to the second superordinate network node. Also analogous to the first, second, third and fourth signal path or analogous to the first and second optical signal, the further first and further second signal path as well as the further third and further fourth signal path are each disjoint on the optical transmission link and each complement one another to form the optical transmission link, a further first optical signal from the first network element to the second superordinate network node both via the further first signal path and via the further second signal path and a further second optical signal from the second network element to the second superordinate network node both via the further third signal path and via the further fourth signal path is transmitted and wherein the second higher-level network node with respect to the further first and further third Signal path has a third wavelength-selective switch and, with respect to the further second and further fourth signal path, a fourth wavelength-selective switch, the third and fourth wavelength-selective switches having second outputs such that each of the second outputs is assigned to one of the plurality of operating modes of the optical telecommunications network, and wherein the method comprises the step, that depending on the operating mode of the optical telecommunications network, the second higher-level network node evaluates the second outputs assigned to the respective operating mode of the optical telecommunications network for receiving the further first optical signal and the further second optical signal.

0022According to the invention it is provided according to an alternative embodiment that the third wavelength-selective switch and the fourth wavelength-selective switch are implemented (together) as a further twin-wavelength-selective switch pair in such a way that the third wavelength-selective switch corresponds to the first wavelength-selective switch functionality of the further twin-wavelength-selective switch pair, while the second wavelength-selective switch corresponds to the second wavelength-selective switch functionality of the further twin wavelength-selective switch pair. Correspondingly, according to such an alternative embodiment, the second higher-level network node has the first wavelength-selective switch functionality of the further twin wavelength-selective switch pair with respect to the further first and further third signal path and, with regard to the further second and further fourth signal path, the second wavelength-selective switch functionality of the further twin-wavelength-selective switch pair, wherein the first and second wavelength-selective switch functionalities of the further twin wavelength-selective switch pair have second outputs such that each of the second outputs is assigned to one of the plurality of operating modes of the optical telecommunications network. The same applies (with regard to the further twin wavelength-selective switch pair) at all points where, in the context of the present patent application, the third wavelength-selective switch or the fourth wavelength-selective switch is mentioned.

0023According to the invention, it is particularly advantageous that cost-effective add / drop components (add / drop ports) can be used both at all higher-level network nodes and at all network elements, each of which sends or receives all wavelengths used in both transmission directions (i.e. colorless "and" directionless "are). According to the invention, a filterless node architecture can advantageously be implemented on all network elements and a passive node architecture in the transit path. According to the invention, it is also of particular advantage that all error patterns (in particular due to failure of a fiber segment, for example due to fiber breakage) can be optically healed on the ring-shaped optical transmission path, ie it is possible to maintain the operation of the optical transmission link in the event of any such fault (regardless of which fiber segment is affected). Rapid protection against all failures in optics, ie in addition to a broken fiber, failure of an amplifier or of line-in or line-out modules, is possible.

0024Compared to a pure waste and drop architecture, only half of the cost-driving electrical-optical interfaces and router ports are required, so that the overall network costs can be reduced considerably. It is also possible according to the invention to provide protection without interaction with the IP level (ie no multilayer resilience is required).

0025According to the invention it is preferably provided that<ul id="ul0002" list-style="none" compact="compact"><li>- a fifth signal path runs between the first superordinate network node and the first network element in the direction from the first superordinate network node to the first network element,</li><li>- a sixth signal path runs between the first superordinate network node and the first network element in the direction from the first superordinate network node via the second superordinate network node to the first network element,</li><li>a seventh signal path runs between the first superordinate network node and the second network element in the direction from the first superordinate network node to the second network element, and</li><li>- an eighth signal path runs between the first superordinate network node and the second network element in the direction from the first superordinate network node via the second superordinate network node to the second network element,</li></ul>wherein the fifth and sixth signal path and the seventh and eighth signal path are each disjoint on the optical transmission link and each complement each other to form the optical transmission link and a third optical signal from the first superordinate network node to the first network element via the fifth signal path as well as via the sixth signal path and a fourth optical signal from the first superordinate network node to the second network element both via the seventh signal path as well as via the eighth signal path, wherein the second higher-level network node has a fourth wavelength-selective switch with respect to the sixth and eighth signal path, the fourth wavelength-selective switch having second outputs such that one of the plurality of operating modes of the optical telecommunications network is assigned to each of the second outputs, and wherein the method comprises the step , that the third optical signal and / or the fourth optical signal are forwarded to the first and / or second network element through the second superordinate network node.

0026According to the invention, the fifth to eighth signal path also ensures the reverse direction, ie data transmission from the first superordinate network node to the first or second network element, with transmission being carried out directly to the respective network element for the fifth and seventh signal path, and via the sixth and eighth signal path the second higher-level network node is transmitted to the respective network element and for the third or fourth optical signal, in particular, in turn, use different optical wavelengths or colors. Because a transmission using a wavelength-selective switch (namely the wavelength-selective switch of the second superordinate network node) is also used for the reverse direction - from the respective higher-level network node to the respective network element and at least for two of the four signal paths, depending on the operating mode of the optical telecommunications network used he follows, a quick switchover and thus healing on the optical level can also be guaranteed in the event of a fiber break.

0027According to the invention it is provided in particular that the optical telecommunication network is symmetrical with regard to the first and second superordinate network node also with regard to the reverse direction (ie the data transmission from the superordinate network nodes to the network elements), that is, the roles of the first and second superordinate network nodes can in particular be exchanged or analogous to the fifth, sixth, seventh and eighth signal path, another fifth signal path runs from the second superordinate network node to the first network element, another sixth signal path runs from the second superordinate network node via the first superordinate network node to the first network element, a further seventh signal path from the second superordinate network node to the second network element and a further eighth signal path from the second superordinate network node via the first superordinate network node to the second network element. Again analogous to the fifth to eighth signal path, the further fifth and further sixth signal path as well as the further seventh and further eighth signal path are each disjoint and complement each other to form the optical transmission path, and there is a further third optical signal from the second superordinate network node to the first network element both via the fifth signal path and via the sixth signal path and a further fourth optical signal from the second superordinate network node to the second network element both via the seventh signal path and the eighth signal path is transmitted. Again analogous to the fifth to eighth signal path, the first higher-level network node has the second wavelength-selective switch with respect to the further sixth and further eighth signal path, the second wavelength-selective switch having first outputs such that one of the plurality of operating modes of the optical telecommunications network is assigned to each of the first outputs is, and wherein the method comprises the step, that the further third optical signal and / or the further fourth optical signal are forwarded to the first and / or second network element through the first superordinate network node.

0028According to the invention, it is also preferred that the first higher-level network node has a first performance monitor and a first optical switch, the evaluation - for receiving the first optical signal and the second optical signal by the first higher-level network node - of the respective operating mode of the optical Telecommunications network associated output of the first outputs comprises the following substeps:<ul id="ul0003" list-style="none" compact="compact"><li>- In a first sub-step, a specific output of the first outputs assigned to the present operating mode of the optical telecommunications network is evaluated, with an optical signal power parameter of at least one of the first outputs being recorded by the first power monitor,</li><li>- In a subsequent second sub-step it is decided whether the value of the optical signal power parameter recorded in the first sub-step indicates a change to the evaluation of an output of the first outputs that is different from the specific output,</li><li>- In a subsequent third sub-step - in the event that the detected value of the optical signal power parameter indicates a change in the output of the first outputs - the first switch of the first higher-level network node is actuated to evaluate the other output, or - in the event that the detected value of the optical signal power parameter does not indicate a change in the output of the first outputs - branches to the first substep.</li></ul>

0029The fact that, according to the invention, a switch is made between the various operating modes and in particular between the normal operating mode and the respectively present fault operating mode by actuating the first switch as a function of the optical signal performance parameter monitored by the performance monitor, it is advantageously possible according to the invention that an error situation of the optical telecommunications network can be responded.

0030With regard to the monitoring of the optical signal power parameter, it is particularly preferred according to the invention that<ul id="ul0004" list-style="none" compact="compact"><li>- Either (ie according to a first variant of the present invention) the optical signal power parameter of the output of the first outputs corresponding to the normal operating mode is detected by the first power monitor, with a spectral analysis being performed in addition,</li><li>- or that (according to a second variant of the present invention) the optical signal power parameters of all first outputs are recorded by the first power monitor.</li></ul>

0031According to the first variant, it is possible to monitor only the output of the first outputs corresponding to the normal operating mode or to detect it by the power monitor; In order to obtain information about which (of different) fault operating modes is to be used in the event of a fault, it is advantageously possible to carry out a spectral analysis or spectral analysis (of the different wavelengths (or Colors) that are present or arrive at the output of the first outputs corresponding to the normal operating mode). If such a spectral analysis is carried out, it is advantageously possible to decide with comparatively little effort, depending on the incoming (or non-incoming) wavelengths, which output is the first (or at the second higher-level network node, the second) outputs must be selected in the event of a fault (operating mode). Alternatively or additionally, according to the second variant, it is also advantageously possible that (in the event of an error) to determine the error operating mode to be used, the optical signal power parameters of all the first outputs are recorded by the first power monitor, for example in the sense of merely adding up all the first outputs or in the Meaning an individual evaluation of each of the first outputs to the effect that that in each case the sum of the incoming optical signals of the different wavelengths is recorded, whereby to determine which output of the first (for the first higher-level network node) (or second for the second higher-level network node) outputs is to be selected for the present error case (operating mode), the Output is selected which has the strongest signal or which has a signal which has not collapsed (due to a fiber break, for example).

0032In a manner analogous to that already stated above, the first and second higher-level network nodes are, according to the invention, designed in particular symmetrically, ie The second higher-level network node also has - analogously to the first performance monitor of the first higher-level network node - a second performance monitor and a second optical switch, whereby the evaluation - for the reception of the further first optical signal and the further second optical signal by the second higher-level network node - of the output of the second outputs assigned to the respective operating mode of the optical telecommunication network, the analog sub-steps (which were mentioned above with regard to the first higher-level network node) includes.

0033Furthermore, it is preferably provided according to the invention that the optical signals of the first outputs of the first and second wavelength-selective switch are each effected by optical addition of the respective output of the first wavelength-selective switch and the second wavelength-selective switch by means of optical couplers, with both the first and the second in particular wavelength-selective switches are set so that that a collision of an optical signal transmitted by the first wavelength-selective switch with an optical signal transmitted by the second wavelength-selective switch is avoided on all first outputs.

0034In this way, according to the invention, it is advantageously possible for the wavelength-selective switches (both of the first superordinate network node and of the second superordinate network node) to be more or less statically set or to avoid interference effects or the laser effect. can be adjusted and (in the event of an error, in particular a fiber break at any point in the optical telecommunications network) only a switchover with regard to the output of the first outputs to be used (or evaluated) (with the aid of the first switch of the first higher-level network node) (or . a switch with regard to the to be used (resp. to be evaluated) output of the second outputs using the second switch of the second higher-level network node).

0035According to the invention, it is also preferably provided that the detection and evaluation of the optical signal power parameter and the actuation of the first switch of the first higher-level network node take place within a time interval after the occurrence of the fault, the time interval being less than to a maximum of 100 milliseconds, preferably less than up to a maximum of 50 milliseconds, particularly preferably less than up to a maximum of 30 milliseconds.

0036This advantageously makes it possible according to the invention that this error situation can also be compensated for in the event of a serious error at the level of the optical telecommunications network, such as a fiber break, without this necessarily having adverse consequences for the IP level, in particular a change in routing configurations at the IP level (Internet Protocol level).

0037Another object of the present invention is an optical telecommunication network for more efficient data transmission in wavelength division multiplex operation (WDM) of different optical wavelengths according to claim 7 of the present invention.

0038It is hereby advantageously possible according to the invention - also with regard to the optical telecommunication network - that the data transmission bandwidth available in the normal case (ie without a faulty impairment of the optical telecommunication network) can be improved by using the specified transmission capacity between, both in normal operation and in an error operating state the various network elements or network nodes can be implemented.

0039Furthermore, according to the invention - also with reference to the optical telecommunications network - it is preferably provided that<ul id="ul0005" list-style="none" compact="compact"><li>- a fifth signal path runs between the first superordinate network node and the first network element in the direction from the first superordinate network node to the first network element,</li><li>- a sixth signal path runs between the first superordinate network node and the first network element in the direction from the first superordinate network node via the second superordinate network node to the first network element,</li><li>a seventh signal path runs between the first superordinate network node and the second network element in the direction from the first superordinate network node to the second network element, and</li><li>- an eighth signal path runs between the first superordinate network node and the second network element in the direction from the first superordinate network node via the second superordinate network node to the second network element,</li></ul>wherein the fifth and sixth signal path and the seventh and eighth signal path are each disjoint on the optical transmission path and each complement one another to form the optical transmission path, and the optical telecommunications network is configured in such a way that a third optical signal from the first superordinate network node to the first network element is transmitted both via the fifth signal path and via the sixth signal path and a fourth optical signal from the first superordinate network node to the second network element via both the seventh signal path and the eighth signal path, wherein the second superordinate network node has a fourth wavelength-selective switch with respect to the sixth and eighth signal path, wherein the fourth wavelength-selective switch has second outputs such that one of the plurality of operating modes of the optical telecommunication network is assigned to each of the second outputs, and wherein the optical telecommunication network is configured such that the third optical signal and / or the fourth optical signal to be forwarded to the first and / or second network element.

0040Furthermore, according to the invention - also with reference to the optical telecommunications network - it is preferred that the first higher-level network node has a first power monitor and a first optical switch, the optical telecommunications network being configured in such a way that for evaluation - for receiving the first optical signal and the second optical signal by the first superordinate network node - of the output of the first outputs of optical signal power parameters assigned to the respective operating mode of the optical telecommunications network, at least one of the first outputs is detected by the first power monitor and depending on the detected value of the optical signal power parameter by operating the first switch the output of the first outputs is changed.

0041The present invention also relates to a computer program with program code means with the aid of which all steps of the method according to the invention can be carried out when the computer program is executed on a programmable device and / or a higher-level network node.

0042Furthermore, the subject matter of the present invention is a computer program product with a computer-readable medium and a computer program stored on the computer-readable medium with program code means which are suitable so that all steps of the method according to the invention can be carried out when the computer program is on a programmable device and / or a higher-level network node is performed.

0043Further details, features and advantages of the invention emerge from the drawings and from the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not restrict the essential inventive concept.

Brief description of the drawings

0044<dl id="dl0001"><dt><b>Figure 1</b></dt><dd>shows a schematic view of an exemplary optical telecommunications network or an optical transmission link with a first and a second superordinate network node and with a first network element and a second network element.</dd><dt><b>Figure 2</b></dt><dd>shows a further schematic view of the exemplary optical telecommunication network or the optical transmission path with the first and the second superordinate network node as well as with the first network element and the second network element, the first superordinate network node and the second superordinate network node being shown in more detail - for the case of Data transmission from the first or second network element to the first superordinate network node.</dd><dt><b>Figure 3</b></dt><dd>shows a further schematic view of the exemplary optical telecommunication network or the optical transmission path with the first and the second superordinate network node as well as with the first network element and the second network element, the first superordinate network node and the second superordinate network node being shown in more detail - for the case of Data transmission from the first superordinate network node to the first or second network element.</dd><dt><b>Figure 4</b></dt><dd>shows schematically a network element in more detail.</dd></dl>

Embodiments of the invention

0045In the various figures, the same parts are always provided with the same reference numerals and are therefore usually only named or mentioned once.

0046In <figref idref="f0001">Figure 1</figref> is a schematic view of an exemplary optical telecommunications network 100 or a ring-shaped closed optical transmission link 150 with a first superordinate network node R2, a second superordinate network node R2 'and with a first network element R1-1 and a second network element R1-2.

0047According to the in <figref idref="f0001">Figure 1</figref> In the illustrated embodiment, the first superordinate network node R2 has a first optical network node element 11 and the second superordinate network node R2 ′ has a second optical network node element 12. Furthermore, the first network element R1-1 has a third optical network node element 21 and the second network element R1-2 has a fourth optical network node element 22. It is preferably provided that the first, second, third and fourth optical network node elements 11, 12, 21, 22 each have a flexible data transmission capacity with regard to the reception of data via the optical transmission link 150 and also with regard to the transmission of data via the optical transmission link 150 . An optical network node element 11, 12, 21, 22 has in particular at least one optical transponder and a multiplexer. In the context of the present invention, a network node element 11, 12, 21, 22, which in particular has a flexible data transmission capacity with regard to the reception of data via the optical transmission link or with regard to the transmission of data via the optical transmission link, denotes such an optical network node element 11, 12 , 21, 22, which in particular has a data transmission rate (in transmit mode or in receive mode) or its modulation method used has flexible transponders.

0048From the schematically illustrated example of the arrangement of the higher-level network nodes R2, R2 'and the network elements R1-1, R1-2, it can be seen that the path along the optical transmission link 150 between the first optical network node element 11 (or the first higher-level network node R2) and the third optical network node element 21 (or the first network element R1-1) via a first signal path 151 (ie via the one shown in FIG <figref idref="f0001">Figure 1</figref> right side of the ring-shaped closed optical transmission link 150) is shorter than via a second signal path 152 (ie via the left side of the ring-shaped closed optical transmission link 150 according to FIG <figref idref="f0001">Figure 1</figref>). Similarly, assume (although this from the<figref idref="f0001">Figure 1</figref> not necessarily clearly visible) that the route along the optical transmission link 150 between the first optical network node element 11 (or the first superordinate network node R2) and the fourth optical network node element 22 (or the second network element R1-2) via a third Signal path 153 (ie via the in the pictorial representation according to <figref idref="f0001">Figure 1</figref> right side of the ring-shaped closed optical transmission link 150) is shorter than via a fourth signal path 154 (ie via the left side of the ring-shaped optical transmission link 150 according to FIG <figref idref="f0001">Figure 1</figref>). The directional arrows of the first, second, third and fourth signal path 151, 152, 153, 154 each point (from the first and second network element R1-1, R1-2, respectively) to the first superordinate network node R2.

0049In the opposite direction (ie away from the first superordinate network node R2 in the direction of the first or second network element R1-1, R1-2), signal paths are also provided according to the invention, but in FIG <figref idref="f0001">Figure 1</figref> not shown explicitly for the sake of simplicity and clarity. A fifth signal path (in<figref idref="f0001">Figure 1</figref> not shown, but designated below with the reference number 155 and running opposite to the first signal path) runs from the first superordinate network node R2 to the first network element R1-1, a sixth signal path (in <figref idref="f0001">Figure 1</figref> not shown, but designated below with the reference numeral 156 and running opposite to the second signal path) runs from the first superordinate network node R2 via the second superordinate network node R2 'to the first network element R1-1, a seventh signal path (in <figref idref="f0001">Figure 1</figref> not shown, but designated below with the reference number 157 and running opposite to the third signal path) runs from the first superordinate network node R2 to the second network element R1-2 and an eighth signal path (in <figref idref="f0001">Figure 1</figref> not shown, but designated below with the reference numeral 158 and running opposite to the fourth signal path) runs from the first superordinate network node R2 via the second superordinate network node R2 'to the second network element R1-2.

0050According to the invention, a first optical signal S1 is transmitted from the first network element R1-1 both via the first and also via the second signal path 151, 152 to the first superordinate network node R2. Furthermore, according to the invention, a second optical signal S2 is transmitted from the second network element R1-2 both via the third and also via the fourth signal path 153, 154 to the first superordinate network node R2. In the opposite direction (ie from the first higher-level network node R2, a third signal (in <figref idref="f0001">Figure 1</figref> not shown, but referred to below with the reference symbol S3) to the first network element R1-1 - via the fifth signal path and the sixth signal path 155, 156 - and a fourth signal (in <figref idref="f0001">Figure 1</figref> not shown, but designated below with the reference symbol S4) to the second network element R1-2 - via the seventh signal path and via the eighth signal path 155, 156 -.

0051So far, only the signal paths from or to the second superordinate network node R2 have been considered. The optical telecommunication network 100 is preferably provided symmetrically with respect to the first and second superordinate network node, so that in an analogous manner (to the previous description of a first to eighth signal path from and to the first superordinate network node R2) a further first signal path, a further second signal path, another third signal path, another fourth signal path, another fifth signal path, another sixth signal path, a further seventh signal path and a further eighth signal path from and to the second superordinate network node R2 'can be considered.

0052In <figref idref="f0001">Figure 2</figref> is another view of the exemplary optical telecommunications network 100 or the optical transmission link 150 with the first and the second superordinate network node R2, R2 'and with the first network element R1-1 and the second network element R1-2 shown, the first superordinate network node R2 and the second higher-level network node R2 'are shown in more detail; is emphasized in<figref idref="f0001">Figure 2</figref> the case of data transmission from the first or second network element R1-1, R1-2 to the first superordinate network node R2: The first network element R1-1 sends the first optical signal S1 (using at least a first optical wavelength of the optical transmission link 150) to the first superordinate network node R2 and the second network element R1-2 sends the second optical signal S2 (using at least a second ( from the first optical wavelength different) optical wavelength of the optical transmission link 150) to the first superordinate network node R2. The first optical signal S1 is transmitted via the first signal path 151 (shown in FIG <figref idref="f0001">Figure 2</figref> proceeding from the first network element R1-1 to the right more or less directly to the input (first wavelength-selective switch 111) of the first superordinate network node R2) and via the second signal path 152 (in the illustration in FIG <figref idref="f0001">Figure 2</figref> starting from the first network element R1-1 to the left, the second signal path 152 leading or running via the second network element R1-2 and the second superordinate network node R2 '). The second optical signal S2 is transmitted via the third signal path 153 (shown in FIG<figref idref="f0001">Figure 2</figref> starting from the second network element R1-2 to the right, via the first network element R1-1 to the input (first wavelength-selective switch 111) of the first superordinate network node R2) and via the fourth signal path 154 (in the illustration in FIG <figref idref="f0001">Figure 2</figref> starting from the second network element R1-2 to the left, the fourth signal path 154 leading or running via the second superordinate network node R2 ').

0053In <figref idref="f0002">Figure 3</figref> is another view of the exemplary optical telecommunications network 100 or the optical transmission link 150 with the first and the second superordinate network node R2, R2 'and with the first network element R1-1 and the second network element R1-2 shown, the first superordinate network node R2 and the second higher-level network node R2 'are shown in more detail; is emphasized in<figref idref="f0002">Figure 3</figref> the case of data transmission from the first superordinate network node R2 to the first or Second network element R1-1, R1-2: The first higher-level network node R2 sends the third optical signal S3 (using at least one third optical wavelength of the optical transmission link 150) to the first network element R1-1 and the fourth optical signal S4 (using at least a fourth (different from the third optical wavelength) optical wavelength of the optical transmission link 150) to the second network element R1-2. The third optical signal S3 is transmitted via the fifth signal path 155 (shown in FIG <figref idref="f0002">Figure 3</figref> starting from the first superordinate network node R2 to the right more or less directly to the input of the first network element R1-1) and via the sixth signal path 156 (in the illustration in FIG <figref idref="f0002">Figure 3</figref> starting from the first superordinate network node R2 to the left, the sixth signal path 156 leading or running via the second superordinate network node R2 'and the second network element R1-2). The fourth optical signal S4 is transmitted via the seventh signal path 157 (in the illustration in FIG<figref idref="f0002">Figure 3</figref> starting from the first superordinate network node R2 to the right, via the first network element R1-1 to the input of the second network element R1-2) and via the eighth signal path 158 (in the illustration in FIG <figref idref="f0002">Figure 3</figref> starting from the second superordinate network node R2 to the left, the eighth signal path 158 leading or running via the second superordinate network node R2 '). Finally, both the third optical signal S3 (to the first network element R1-1) and the fourth optical signal S4 (to the second network element R1-2) are sent, with different signal paths being possible for both signals. Analogously to this, a further third optical signal S3 '(to the first network element R1-1) and a further fourth optical signal S4' (to the second network element R1-2) are sent out by the second superordinate network node R2 ', again different signals for the two further further signal paths are possible, but they are in the <figref idref="f0002">Figure 3</figref> are not shown in detail.

0054In <figref idref="f0002">Figure 4</figref> a network element R1 (ie a network element analogous to the first network element R1-1 or the second network element R1-2) is shown schematically in a more detailed representation. The network element R1 has a first network element input 161 (in<figref idref="f0002">Figure 4</figref> on the right-hand side, coming directly (or at most via a further network element R1-1) coming from the first superordinate network node R2) and a first network element output 171 (in <figref idref="f0002">Figure 4</figref> also on the right-hand side, going directly (or at most via a further network element R1-1) to the first higher-level network node R2). The network element R1 also has a second network element input 162 (in<figref idref="f0002">Figure 4</figref> on the left-hand side, coming directly (or at most via a further network element R1-2) coming from the second superordinate network node R2 ') and a second network element output 172 (in <figref idref="f0002">Figure 4</figref> also on the left-hand side, going directly (or at most via a further network element R1-2) to the second superordinate network node R2 '). The network element R1 has inside in particular a first network element splitter 181 for extracting the optical signal arriving at the first network element input 161 and a second network element splitter 182 for extracting the optical signal arriving at the second network element input 162; From the first network element splitter 181 and the second network element splitter 182, the respective extracted optical signals are fed to a network element switch 180, which selects either the optical signal coming from the first network element splitter 181 or the optical signal coming from the second network element splitter 182 and feeds it for further processing within the network element R1. Furthermore, the network element R1 has in particular a first network element coupler 191 and a second network element coupler 192 for adding an optical signal generated by the network element to the respective outputs of the network element R1. The first network element coupler 191 couples the optical signal generated in the network element to the first network element output 171 and the second network element coupler 192 couples the optical signal generated in the network element to the second network element output 172, with the optical signal generated in the network element through a further network element splitter 190 to the first network element coupler 191 and split to the second network element coupler 192.

0055Both off <figref idref="f0001">Figure 2</figref> as well as from <figref idref="f0002">Figure 3</figref> It can be seen that the first and second superordinate network nodes R2, R2 'each have two wavelength-selective switches: the first network node R2 has a first wavelength-selective switch 111 and a second wavelength-selective switch 112 and the second superordinate network node R2' has a third wavelength-selective switch 113 and a fourth wavelength-selective switch 114. All wavelength-selective switches 111, 112, 113, 114 each have outputs (in addition to an input), the outputs of the first and second wavelength-selective switches 111, 112 being coupled by means of first optical couplers 121 and being referred to as first outputs 115, while the Outputs of the third and fourth wavelength-selective switches 113, 114 are also coupled by means of second optical couplers 122 and are referred to as second outputs 116.

0056The first optical couplers 121 each have an output of the first wavelength-selective switch 111 coupled to an output of the second wavelength-selective switch 112 (ie these two outputs form the two inputs of one of the first optical couplers 121). The first optical couplers 121 are used to link optical signals - which are sent to one of the outputs of the first wavelength-selective switch 111 or at one of the outputs of the second wavelength-selective switch 112 - either for forwarding from the first superordinate network node R2 to another point within the optical transmission link 150 or the optical telecommunications network 100 or for processing within the first superordinate network node R2. The outputs of the first optical coupler 121 and / or the provided for evaluation or processing within the first superordinate network node R2. At least one such output of one of the first optical couplers 121 is (or is) monitored by a first performance monitor 131, the first performance monitor 131 having an optical signal performance parameter (of the optical signals on the monitored output or on the monitored outputs of the first optical coupler 121 ) supervised. One of the first outputs 115 is selected by a first switch 141 of the first superordinate network node R2 and forwarded to the first superordinate network node R2 for processing the optical (input) signal. A first output A1 of the first optical coupler 121 provided for forwarding from the first superordinate network node R2 to another point within the optical transmission link 150 is forwarded to a first combined splitter coupler 125, which couples the optical signals of this first output A1 and also the optical signals originally generated by the first superordinate network node R2 and both in the direction of the first network element R1-1 in the optical transmission link 150 (in <figref idref="f0001">Figure 2</figref> and <figref idref="f0002">3</figref> to the right) and to a third optical coupler 126 (for feeding, in the direction of the second superordinate network node R2 ', in the optical transmission link 150). The third optical coupler 126 receives - in addition to the optical signals from the first combined splitter coupler 125 - the optical signals of a second output A2 of the first optical coupler 121 and provided for forwarding from the first superordinate network node R2 to another point within the optical transmission link 150 feeds these optical signals into the optical transmission link 150 for transmission to the second superordinate network node R2 '(in <figref idref="f0001">Figure 2</figref> and <figref idref="f0002">3</figref> to the left).

0057The second optical couplers 122 each have an output of the third wavelength-selective switch 113 coupled to an output of the fourth wavelength-selective switch 114 (ie these two outputs form the two inputs of one of the second optical couplers 122). The second optical couplers 122 are used to link optical signals - which are sent to one of the outputs of the third wavelength-selective switch 113 or at one of the outputs of the fourth wavelength-selective switch 114 - either for forwarding from the second superordinate network node R2 'to another point within the optical transmission link 150 or the optical telecommunications network 100 or for processing within the second superordinate network node R2'. The for evaluation or Processing within the second superordinate network node R2 'provided outputs of the second optical coupler 122 or at least one such output of one of the second optical couplers 122 are (or is) monitored by a second performance monitor 132, the second performance monitor 132 also having an optical signal power parameter ( the optical signals on the monitored output or on the monitored outputs of the second optical coupler 122). One of the second outputs 116 is selected by a second switch 142 of the second superordinate network node R2 'and passed on to the second superordinate network node R2' for processing the optical (input) signal. A third output A3 of the second optical coupler 122 provided for forwarding from the second superordinate network node R2 'to another point within the optical transmission link 150 is forwarded to a second combined splitter coupler 127, which couples the optical signals of this third output A3 and also the optical signals originally generated by the second superordinate network node R2 'and both in the direction of the second network element R1-2 in the optical transmission link 150 (in <figref idref="f0001">Figure 2</figref> and <figref idref="f0002">3</figref> to the left) and to a fourth optical coupler 128 (for feeding, in the direction of the first superordinate network node R2, in the optical transmission link 150). The fourth optical coupler 128 receives - in addition to the optical signals from the second combined splitter coupler 127 - the optical signals of a fourth output A4 of the second optical coupler provided for forwarding from the second superordinate network node R2 'to another point within the optical transmission link 150 122 and feeds these optical signals into the optical transmission link 150 for transmission to the first higher-level network node R2 (in <figref idref="f0001">Figure 2</figref> and <figref idref="f0002">3</figref> to the right).

0058According to the invention, one of the first outputs 115 (and one of the second outputs 116) are present in particular for each operating mode of the optical telecommunication network 100 to be considered. By means of the first and second switch 141, 142, respectively, it is possible to switch over the optical connections on the optical transmission path 150 quickly. This enables very short switching times to heal the optical connection (which are so short in particular (a few milliseconds to a few tens of milliseconds) that no configuration change is absolutely necessary on the IP level - only the first and second switches may need to be synchronized with one another (or coordinated). The wavelength-selective switches 111, 112, 113, 114 are provided in particular as fixed, preset optical filter banks (within the higher-level network nodes R2, R2 ') and each have an optimally filtered WDM spectrum available at the output for every fault. The WDM spectra from both directions (i.e. at the first and second wavelength-selective switches 111, 112 and on the third and on the fourth wavelength-selective switch 113, 114) are added with optical couplers - for this, simple optical couplers can be used in particular. The first resp. Second switch 141, 142 is designed in particular as a fast optical multi-switch and in the event of a fault - controlled by, for example, a preferably simple multiport power meter or a spectrally resolving multiport monitor as a power monitor - selects the WDM spectrum that covers all optical transmission channels (ie all wavelengths used on the optical transmission link 150).

0059The optical filter banks are implemented in particular by two complementary and controllable WSS modules (or wavelength-selective switches). According to the invention, the wavelength-selective switches 111, 112, 113, 114 are suitably set before an error occurs. Alternatively, the wavelength-selective switches could also be replaced by fixed filter structures, which, however, would have the disadvantage that any wavelength assignment or -change during the operating phase would not be possible or would only be possible with additional effort.

0060Since the optical transmission link 150 with a number of n network elements (R1-1, R1-2, ...) n +2 Has fiber segments, it is advantageous if n + 3 First and second outputs 115, 116 are present, so that one of the first and one of the second outputs 115, 116 is present for each error case (operating mode) (e.g. a fiber break on a fiber segment) and additionally also for normal operating mode.