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

The invention relates to a method for more efficient data transmission in an optical telecommunications network in wavelength division multiplex mode (WDM, wavelength division multiplex) of different optical wavelengths, the optical telecommunications network having a first higher-level network node, a second higher-level network node and furthermore a plurality of network elements .

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

Furthermore, the 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.

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

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

The ring closure represents an improvement over these described topologies, because there is always a way to the goal in the event of an error in the optical telecommunications network. However, this has the consequence that the ring must be physically interrupted at at least one point on each wavelength, since otherwise a "laser" effect can occur in the ring equipped with amplifiers. Such an interruption can be realized with strongly damping filters in reconfigurable optical add / drop nodes (ROADM, Reconfigurable Optical Add / Drop Multiplexer).

When operating such aggregation networks, it is also known that the backbone network (or core network) is operated in an A&B network structure - or with a double 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: behind a first higher-level network node (the optical telecommunications network) is, for example, the A (backbone) network and behind a second higher-level network node (the optical telecommunications network) there is (to the A backbone network) ) symmetrical B (backbone) network.

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

Operation of such an aggregation network with the aim of ensuring the highest possible level of reliability provides that, in addition to the part used for data transmission (between a node sending and receiving the data), the ring-shaped fiber optic link (working path) for the fault (i.e. For example, in the event of a fiber break on the part of the glass fiber ring used for operational purposes), the remaining part of the ring-shaped glass fiber path (backup path) is used to transfer the data between the nodes involved.

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

However, such an operation of an optical telecommunications network usually leads to inadequate utilization of the available bandwidth of the aggregation network, in particular as soon as optical interfaces (transponders, transceivers) with a data rate adapted to the route length are used, so-called flex-rate transceivers.

Furthermore, from the publication <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. However, optical signals are divided into a transit path and a drop path.

Disclosure of the invention

The invention has for its object a method and an optical telecommunications network and a computer program and

To make available a computer program product that uses the bandwidth resources as optimally as possible and thus, under otherwise identical conditions - in particular with regard to the investment requirement for the components of the optical telecommunications network - higher performance (in the sense of an overall higher, usable data transport capacity) with at the same time not or only insignificantly reduced reliability against failure such as fiber breaks or the like.

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

It is therefore advantageously possible according to the present invention that the normally (ie available data transmission bandwidth without a faulty impairment of the optical telecommunications network can be improved in that both in normal operation and in a fault operating mode (of several fault operating states which relate in particular to fiber breaks), that can occur between two (subordinate) network elements or between a subordinate network element and a superordinate network node or between two superordinate network nodes) the predetermined transmission capacity can be realized between the different network elements or network nodes. In this way, according to the invention, advantages in particular can be realized compared to operating the optical telecommunications network, which requires that the first part of the optical telecommunications network used for the 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 for data transmission between the same (subordinate) network element on the one hand and the second higher-level network node on the other hand not in normal operational cases is being used, but that normally a second part of the optical telecommunications network is used for this data transmission (from or to the second higher-level network node), which differs from the first part of the optical telecommunications network or is disjoint and usually longer and therefore achieves low performance .

According to the invention, it is provided that the optical telecommunications network has an optical transmission link which is closed in a ring (ie in the form of an optical ring or a ring of a glass fiber link or Glass fiber line), wherein the optical telecommunications network has a first higher-level network node, a second higher-level network node and furthermore a plurality of network elements, the plurality of network elements having at least a first network element and a second network element. As a result of the ring closure, it is advantageously possible according to the invention that even in the event of a fault (ie there is always a (non-faulty) way of carrying out the data transmission between the respective source of the data and the respective destination of the data, for example in the case of an optical fiber line interrupted at one point). According to the invention, it must be ensured that the optical ring is physically interrupted at one point on each wavelength, since otherwise there is interference or a “laser” effect in the ring equipped with amplifiers. This interruption is ensured according to the invention in that the first higher-level network node has a first wavelength-selective switch (WSS) and a second wavelength-selective switch, the first and the second wavelength-selective switch in each case next to an input (which is connected to the optical transmission path ) have individual outputs (hereinafter also referred to as first outputs), the outputs of the first and second wavelength-selective switches being coupled to one another. As a result, the ring closure in the optical telecommunications network can be produced in a manner which ensures that on a considered output (the wavelength-selective switch) no wavelength used in the optical telecommunications network is fed in by the first wavelength-selective switch and also by the second wavelength-selective switch or 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 wavelengths present on the input side (at the wavelength-selective switch) (or "colors" used for optical data transmission) this wavelength either at the output under consideration is present 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 in either by the first wavelength-selective switch or by the second wavelength-selective switch - but not by two wavelength-selective switches at the same time. This advantageously makes it possible according to the invention for interference effects or the laser effect to be avoided and nevertheless for the normal operating mode of the optical telecommunications network to ensure that from any point on the optical transmission link (ie from any network element or higher-level network node) any other point of the optical transmission path can be reached using the same wavelength both over the shortest connection path of the optical transmission path and also using the complementary (ie disjoint to the shortest distance) path of the ring-shaped optical transmission path - ie in opposite directions, and that for each failure mode of operation (ie in particular for cases of fiber breakage at any point on the ring-shaped optical transmission link) at least one of these links (ie either the shortest link or the complementary link) can be used.

According to the invention, it is provided in accordance with an alternative embodiment that the first wavelength-selective switch and the second wavelength-selective switch (together) are implemented as a twin-wavelength-selective switch pair such 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 paths 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 telecommunications network. The same applies (with regard to the twin-wavelength-selective switch pair) at all points where, in the context of the present patent application, the first wavelength-selective switch or the second wavelength-selective switch is mentioned.

Typically, the optical telecommunications network or the glass fiber 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 ensure the backbone network. Furthermore, the optical telecommunications network has the first higher-level network node and the second higher-level network node. These network nodes are also referred to as R2 routers or as backbone routers. Because the first and second higher-level network nodes are part of the optical telecommunications network or part of the optical transmission link, 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 double structure is operated. From the point of view of the Internet protocol level or Internet protocol layer advantageously possible that both networks (or backbone networks) protect each other: Behind a first higher-level network node (the optical telecommunications network or the optical transmission link) there is, for example, the A (backbone) network and behind a second higher-level network node (the optical telecommunications network or the optical transmission link) is the B (backbone) network, which is symmetrical (to the A backbone network).

This also advantageously makes it possible for the double connection of the aggregation nodes (ie each individual one of the (plurality or plurality of) R1 routers) to two R2 routers (ie the "dual homing" principle) not to be affected. In such a case, traffic relationships generally only exist between the aggregation node (or R1 router) in question 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.

According to the invention, the telecommunications network has the optical transmission link as a topologically closed (and bidirectional, ie optical transmission link that can be used bidirectionally on each route section, that the optical transmission link directly or indirectly connects the first higher-level network node and the first network element and the first network element and the second network element and furthermore the second network element and the second higher-level network node, and that the optical transmission link also also connects the first higher-level network node and the second higher-level network node Connects network nodes with each other. As a result, the optical transmission link according to the invention<ul id="ul0001" list-style="none" compact="compact"><li>- defines a first signal path 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 higher-level network node, the second signal path additionally running from the second higher-level network node to the first higher-level network node,</li><li>- Defines a third signal path from the second network element to the first higher-level network node and</li><li>a fourth signal path is defined from the second network element to the second higher-level network node, the fourth signal path additionally running from the second higher-level network node to the first higher-level network node,</li></ul>wherein the first and second signal paths and the third and fourth signal paths on the optical transmission path are each disjoint and complement each other (ie are complementary) to the optical transmission path, and wherein a first optical signal (using a first wavelength or "Color") from the first network element to the first higher-level network node both via the first signal path and via the second signal path and a second optical signal (using a second wavelength or "color") from the second network element to the first higher-level network node both via the third Signal path is also transmitted via the fourth signal path.

According to the invention, it is particularly provided that the optical telecommunications network is symmetrical with respect to the first and second higher-level network node, ie the roles of the first and second higher-level network node can in particular be interchanged or there are - analogous to the first, second, third and fourth signal path - a further first signal path from the first network element to the second higher-level network node, a further second signal path from the first network element to the first higher-level network node, the further second signal path additionally from the first higher-level network node to the second parent network node runs, a further third signal path from the second network element to the second higher-level network node and a further fourth signal path from the second network element to the first higher-level network node, the further fourth signal path additionally running from the first higher-level network node to the second higher-level network node. Also analogous to the first, second, third and fourth signal path or analogous to the first and second optical signals, the further first and further second signal paths and the further third and further fourth signal paths are each disjoint on the optical transmission path and complement each other to form the optical transmission path, wherein a further first optical signal from the first network element to the second higher-level 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 higher-level network node both via the further third signal path and via the further fourth signal path is transmitted and 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, wherein the third and fourth wavelength-selective switch 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, and wherein the method includes the step that, depending on the operating mode of the optical telecommunications network, the second higher-level network node evaluates the second output assigned to the respective operating mode of the optical telecommunications network to receive the further first optical signal and the further second optical signal.

According to the invention, it is provided according to an alternative embodiment that the third wavelength-selective switch and the fourth wavelength-selective switch (together) are implemented 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. Accordingly, in accordance with 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 the second wavelength-selective switch functionality of the further twin-wavelength-selective switch pair with respect to the further second and further fourth signal path, 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.

It is particularly advantageous according to the invention 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 send and receive all the wavelengths used in both transmission directions (which therefore means " colorless "and" directionless "are). According to the invention, a filterless node architecture can be advantageously implemented on all network elements and a passive node architecture in the transit path. According to the invention, it is also particularly advantageous that all error patterns (in particular due to failure of a fiber segment, for example due to fiber breakage) on the ring-shaped optical transmission path can be optically cured, ie it is possible to maintain operation of the optical link for any such fault (regardless of which fiber segment is affected). Fast-acting protection against all failures in the optics is possible, ie in addition to fiber breakage, failure of an amplifier or line-in or line-out modules.

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

According 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 higher-level network node and the first network element in the direction from the first higher-level network node to the first network element,</li><li>a sixth signal path runs between the first higher-level network node and the first network element in the direction from the first higher-level network node via the second higher-level network node to the first network element,</li><li>a seventh signal path runs between the first higher-level network node and the second network element in the direction from the first higher-level network node to the second network element, and</li><li>an eighth signal path runs between the first higher-level network node and the second network element in the direction from the first higher-level network node via the second higher-level network node to the second network element,</li></ul>wherein the fifth and sixth signal paths and the seventh and eighth signal paths are each disjoint on the optical transmission path and complement each other to form the optical transmission path, and wherein a third optical signal from the first higher-level network node to the first network element is via both the fifth signal path and the sixth signal path and a fourth optical signal from the first higher-level network node to the second network element both via the seventh signal path is also transmitted 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 has 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 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 by the second higher-level network node.

According to the invention, the fifth to eighth signal path also guarantees the direction, ie the data transmission from the first higher-level network node to the first or second network element, with transmission for the fifth and seventh signal path directly to the respective network element, for 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 different optical wavelengths or colors are used. Characterized in that for the direction - from the respective higher-level network node to the respective network element and at least for two of the four signal paths - a transmission using a wavelength-selective switch (namely the wavelength-selective switch of the second higher-level network node) depending on the operating mode of the optical telecommunications network used in each case he follows, fast switching and thus healing on the optical level can also be guaranteed in the event of a fiber break.

According to the invention, it is provided in particular that the optical telecommunications network with respect to the first and second higher-level network node is also symmetrical with regard to the direction (ie the data transmission from the higher-level network node to the network elements), ie the roles of the first and second higher-level network node can in particular be interchanged or analog to the fifth, sixth, seventh and eighth signal path, there is a further fifth signal path from the second higher-level network node to the first network element, a further sixth signal path from the second higher-level network node via the first higher-level network node to the first network element, a further seventh signal path from the second higher-level network node to the second network element and a further eighth signal path from the second higher-level network node via the first higher-level network node to the second network element. Again, analogous to the fifth to eighth signal paths, the further fifth and further sixth signal paths and the further seventh and further eighth signal paths are each disjoint on the optical transmission path and complement each other to form the optical transmission path, and there is a further third optical signal from the second higher-level 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 higher-level network node to the second network element both via the seventh signal path and via 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 each of the first outputs is assigned to one of the plurality of operating modes of the optical telecommunications network and 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 by the first higher-level network node.

According to the invention, it is also preferred that the first higher-level network node has a first power monitor and a first optical switch, with the evaluation - for receiving the first optical signal and the second optical signal by the first higher-level network node - of the current operating mode of the optical Output of the first outputs assigned to the telecommunications network 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 telecommunication network is evaluated, an optical signal power parameter of at least one of the first outputs being detected by the first power monitor,</li><li>in a subsequent second sub-step, a decision is made as to whether the value of the optical signal power parameter recorded in the first sub-step indicates a change towards evaluating 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 detected value of the optical signal power parameter does not indicate a change in the output of the first outputs - branching to the first substep.</li></ul>

Due to the fact that, according to the invention, a switch is made between the different operating modes and in particular between the normal operating mode and the particular fault operating mode in each case by actuating the first switch as a function of the optical signal power parameter monitored by the power monitor, it is advantageously possible according to the invention that a fault situation of the optical telecommunications network can be responded to.

With 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 in particular also taking place,</li><li>- Or that (according to a second variant of the present invention) the optical signal power parameters of all first outputs are detected by the first power monitor.</li></ul>

According 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 various) fault operating modes should 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) which 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 relatively little effort depending on the incoming (or non-arriving) wavelengths which output of the first (or the first higher-level network node) at the second higher-level network node second) outputs for the present fault (operating mode) must be selected. As an alternative or in addition, it is also advantageously possible according to the second variant that (in the event of a fault) the optical signal power parameters of all the first outputs are detected by the first power monitor in order to determine the fault mode of operation to be used, for example in the sense of merely summing up all the first outputs or else in the Meaning of an individual evaluation of each of the first outputs that in each case the sum of the incoming optical signals of the different wavelengths is recorded, and in order to determine which output of the (for the first higher-level network node) the first (or for the second higher-level network node second) outputs is to be selected for the present fault (operating mode), the Output is selected which has the strongest signal or which has a signal which (due to a fiber break, for example) has not broken in.

In an analogous manner to that already explained above, the first and second higher-level network nodes are designed according to the invention in particular symmetrically, ie the second higher-level network node also has a second power monitor and a second optical switch, analogous to the first performance monitor of the first higher-level network node, the evaluation - for receiving 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 telecommunications network, the analog substeps (which were mentioned above with regard to the first higher-level network node) includes.

Furthermore, 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 obtained by optical addition of the respective output of the first wavelength-selective switch and the second wavelength-selective switch by means of optical couplers, in particular both the first and the second wavelength selective switches are set such 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 at all first outputs.

This advantageously makes it possible according to the invention for the wavelength-selective switches (both of the first higher-level network node and of the second higher-level network node) to be set more or less statically in order to avoid interference effects or the laser effect, or can be regulated 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 to be used (or evaluated) of the first outputs (with the aid of the first switch of the first higher-level network node) (or a switchover with regard to the to be used (or output) of the second outputs to be evaluated using the second switch of the second higher-level network node).

According 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 or equal to a maximum of 100 milliseconds, preferably less than up to a maximum of 50 milliseconds, particularly preferably less than a maximum of 30 milliseconds.

As a result, it is advantageously possible according to the invention that this error situation can also be compensated for in the event of a serious error on 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).

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

It is hereby advantageously possible according to the invention - also with reference to the optical telecommunications network - that the data transmission bandwidth available in the normal case (ie without a faulty impairment of the optical telecommunications network) can be improved by the fact that the predetermined transmission capacity between normal operation and in the event of an error occurs the different network elements or network nodes can be implemented.

Furthermore, 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 higher-level network node and the first network element in the direction from the first higher-level network node to the first network element,</li><li>a sixth signal path runs between the first higher-level network node and the first network element in the direction from the first higher-level network node via the second higher-level network node to the first network element,</li><li>a seventh signal path runs between the first higher-level network node and the second network element in the direction from the first higher-level network node to the second network element, and</li><li>an eighth signal path runs between the first higher-level network node and the second network element in the direction from the first higher-level network node via the second higher-level network node to the second network element,</li></ul>wherein the fifth and sixth signal paths and the seventh and eighth signal paths on the optical transmission path are each disjoint and in each case complement the optical transmission path and the optical telecommunications network is configured in such a way that a third optical signal is transmitted from the first higher-level network node to the first network element both via the fifth signal path and via the sixth signal path and a fourth optical signal from the first higher-level network node to the second network element both via the seventh signal path and 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 paths, wherein the fourth wavelength-selective switch has second outputs such that each of the second outputs is assigned one of the plurality of operating modes of the optical telecommunication network, and wherein the optical telecommunication network is configured such that the third optical signal and / or the fourth through the second higher-level network node optical signal to the first and / or second network element are forwarded.

Furthermore, 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 that for evaluating - for receiving the first optical signal and the second optical signal through the first higher-level network node - the output of the first outputs of optical signal power parameters associated with 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 actuating the first switch the output of the first outputs is changed.

Furthermore, the 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.

The present invention furthermore relates to a computer program product having a computer-readable medium and a computer program stored on the computer-readable medium and having program code means which are suitable for carrying out all the steps of the method according to the invention when the computer program is on a programmable device and / or a higher-level network node is performed.

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

Brief description of the drawings

<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 higher-level 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 telecommunications network or the optical transmission link with the first and the second higher-level network node and with the first network element and the second network element, the first higher-level network node and the second higher-level network node being shown in more detail - in the case of Data transmission from the first or second network element to the first higher-level network node.</dd><dt><b>Figure 3</b></dt><dd>shows a further schematic view of the exemplary optical telecommunications network or the optical transmission link with the first and the second higher-level network node and with the first network element and the second network element, the first higher-level network node and the second higher-level network node being shown in more detail - in the case of Data transmission from the first higher-level network node to the first or second network element.</dd><dt><b>Figure 4</b></dt><dd>schematically shows a network element in more detail.</dd></dl>

Embodiments of the invention

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

In <figref idref="f0001">Figure 1</figref> a view of an exemplary optical telecommunications network 100 or an annularly closed optical transmission link 150 with a first higher-level network node R2, a second higher-level network node R2 'and with a first network element R1-1 and a second network element R1-2 is shown schematically.

According to the in <figref idref="f0001">Figure 1</figref> In the exemplary embodiment shown, the first higher-level network node R2 has a first optical network node element 11 and the second higher-level 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 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 flexible data transmission capacity with regard to the reception of data via the optical transmission link or with respect 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 the transmission mode or in the reception mode) or of its modulation method used has flexible transponders.

The schematically illustrated example of the arrangement of the higher-level network nodes R2, R2 'and the network elements R1-1, R1-2 shows 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 that shown in the illustration) <figref idref="f0001">Figure 1</figref> right side of the ring-shaped closed optical transmission path 150) is shorter than via a second signal path 152 (ie over the left side of the ring-shaped closed optical transmission path 150 according to FIG <figref idref="f0001">Figure 1</figref>). Similarly, assume (although this is from the<figref idref="f0001">Figure 1</figref> is not necessarily clearly visible) 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 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 path 150) is shorter than via a fourth signal path 154 (ie over the left side of the ring-shaped closed optical transmission path 150 according to FIG <figref idref="f0001">Figure 1</figref>). The directional arrows of the first, second, third and fourth signal paths 151, 152, 153, 154 each point (from the first and second network element R1-1, R1-2) to the first higher-level network node R2.

In the opposite direction (ie away from the first higher-level network node R2 towards the first or second network element R1-1, R1-2), signal paths are also provided according to the invention, but in <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 referred to below with reference number 155 and running opposite to the first signal path), a sixth signal path runs from the first higher-level network node R2 to the first network element R1-1 (in FIG <figref idref="f0001">Figure 1</figref> not shown, but referred to in the following by reference numeral 156 and running opposite to the second signal path), a seventh signal path (in. from the first higher-level network node R2 via the second higher-level network node R2 'to the first network element R1-1) <figref idref="f0001">Figure 1</figref> not shown, but referred to below with the reference symbol 157 and running opposite to the third signal path) runs from the first higher-level 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 referred to below with reference number 158 and running opposite to the fourth signal path) runs from the first higher-level network node R2 via the second higher-level network node R2 'to the second network element R1-2.

According 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 higher-level network node R2. Furthermore, according to the invention, a second optical signal S2 is transmitted from the second network element R1-2 to the first higher-level network node R2 both via the third and via the fourth signal path 153, 154. In the opposite direction (i.e. 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 via the sixth signal path 155, 156 - and transmit a fourth signal (in <figref idref="f0001">Figure 1</figref> not shown, but referred to 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.

So far, only the signal paths from or to the second higher-level network node R2 have been considered. However, the optical telecommunications network 100 is preferably provided symmetrically with respect to the first and second higher-level network node, so that in a similar way (for the previous description of a first to eighth signal path from and to the first higher-level 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 higher-level network node R2 'can be considered.

In <figref idref="f0001">Figure 2</figref> a further view of the exemplary optical telecommunications network 100 or the optical transmission link 150 with the first and the second higher-level network node R2, R2 'and with the first network element R1-1 and the second network element R1-2 is schematically shown, the first higher-level 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 higher-level 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 higher-level 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) of the optical transmission link 150) to the first higher-level network node R2. The first optical signal S1 is transmitted via the first signal path 151 (in the illustration 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 higher-level 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 via the second network element R1-2 and the second higher-level network node R2 '. The second optical signal S2 is transmitted via the third signal path 153 (in the illustration in<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 higher-level network node R2) and via the fourth signal path 154 (in the illustration in FIG <figref idref="f0001">Figure 2</figref> proceeding from the second network element R1-2 to the left, the fourth signal path 154 leading via the second higher-level network node R2 '.

In <figref idref="f0002">Figure 3</figref> a further view of the exemplary optical telecommunications network 100 or the optical transmission link 150 with the first and the second higher-level network node R2, R2 'and with the first network element R1-1 and the second network element R1-2 is schematically shown, the first higher-level 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 higher-level 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 a 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 (in the illustration in FIG <figref idref="f0002">Figure 3</figref> starting from the first higher-level 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> proceeding from the first higher-level network node R2 to the left, the sixth signal path 156 leading via the second higher-level 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 higher-level 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> proceeding from the second higher-level network node R2 to the left, the eighth signal path 158 leading via the second higher-level 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 emitted, different signal paths being possible for both signals. Analogously to this, a further third optical signal S3 '(for the first network element R1-1) and a further fourth optical signal S4' (for the second network element R1-2) are emitted by the second higher-level network node R2 ', again different for both other signals further signal paths are possible, but in the <figref idref="f0002">Figure 3</figref> are not shown in detail.

In <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 schematically shown in more detail. 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 from the first higher-level network node R2) or a first network element output 171 (in <figref idref="f0002">Figure 4</figref> also on the right-hand side, going directly (or at most running through another 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 from the second higher-level network node R2 '(or at most running through a further network element R1-2) and a second network element output 172 (in <figref idref="f0002">Figure 4</figref> likewise on the left-hand side, going directly (or at most running through a further network element R1-2) to the second higher-level network node R2 '). The network element R1 has 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 from the second network element splitter 182, the respective optical signals extracted 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 them 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, the optical signal generated in the network element being connected to the first network element coupler 191 by a further network element splitter 190 and split to the second network element coupler 192.

Both from <figref idref="f0001">Figure 2</figref> as well <figref idref="f0002">Figure 3</figref> it can be seen that the first and second higher-level 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 higher-level 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 (each next 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.

With the first optical couplers 121, an output of the first wavelength-selective switch 111 is 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 serve to link optical signals - which are connected 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 higher-level network node R2 to another point within the optical transmission link 150 or the optical telecommunications network 100 or for processing within the first higher-level network node R2. The outputs of the first optical couplers 121 or, respectively, provided for evaluation or processing within the first higher-level network node R2 at least one such output of one of the first optical couplers 121 is (or is) monitored by a first power monitor 131, the first power monitor 131 an optical signal power parameter (of the optical signals on the monitored output or on the monitored outputs of the first optical couplers 121 ) supervised. A first switch 141 of the first higher-level network node R2 selects one of the first outputs 115 and forwards it to the first higher-level network node R2 for processing the optical (input) signal. A first output A1 of the first optical couplers 121, which is provided for forwarding from the first higher-level 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 furthermore also the optical signals originally generated by the first higher-level network node R2 and both in the direction of the first network element R1-1 into the optical transmission path 150 (in <figref idref="f0001">Figure 2</figref> and <figref idref="f0002">3</figref> to the right) and also to a third optical coupler 126 (for feeding, in the direction of the second higher-level network node R2 ′, into the optical transmission link 150). In addition to the optical signals from the first combined splitter coupler 125, the third optical coupler 126 also receives the optical signals from a second output A2 of the first optical coupler 121 and which is provided for forwarding from the first higher-level network node R2 to another point within the optical transmission path 150 feeds these optical signals into the optical transmission link 150 for transmission to the second higher-level network node R2 '(in <figref idref="f0001">Figure 2</figref> and <figref idref="f0002">3</figref> to the left).

With the second optical couplers 122, an output of the third wavelength-selective switch 113 is 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 serve to link optical signals - which are connected to one of the outputs of the third wavelength-selective switch 113 or are present at one of the outputs of the fourth wavelength-selective switch 114 - either for forwarding from the second higher-level network node R2 'to another point within the optical transmission link 150 or the optical telecommunications network 100 or for processing within the second higher-level network node R2'. The for evaluation or Processing provided within the second higher-level network node R2 ′ of outputs of the second optical couplers 122 or at least one such output of one of the second optical couplers 122 are (or will be) monitored by a second power monitor 132, the second power monitor 132 likewise providing an optical signal power parameter ( of the optical signals on the monitored output or on the monitored outputs of the second optical coupler 122) are monitored. A second switch 142 of the second higher-level network node R2 'selects one of the second outputs 116 and forwards it to the second higher-level network node R2' for processing the optical (input) signal. A third output A3 of the second optical couplers 122, which is provided for forwarding from the second higher-level 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 furthermore also the optical signals originally generated by the second higher-level network node R2 'and both in the direction of the second network element R1-2 into the optical transmission path 150 (in <figref idref="f0001">Figure 2</figref> and <figref idref="f0002">3</figref> to the left) as well as to a fourth optical coupler 128 (for feeding, in the direction of the first higher-level network node R2, into the optical transmission link 150). In addition to the optical signals from the second combined splitter coupler 127, the fourth optical coupler 128 also receives the optical signals from a fourth output A4 of the second optical coupler, which is provided for forwarding from the second higher-level network node R2 ′ to another point within the optical transmission path 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).

According to the invention, one of the first outputs 115 (and one of the second outputs 116) is present in particular for each operating mode of the optical telecommunications network 100 to be considered. By means of the first or second switch 141, 142 it is possible to bring about a rapid switchover of the optical connections on the optical transmission link 150. This enables very short switchover times to be achieved to heal the optical connection (which are in particular so short (a few milliseconds to a few 10 milliseconds) that no configuration change on the IP level is absolutely necessary - only the first and second switches may have to be synchronized with one another (or coordinated). The wavelength-selective switches 111, 112, 113, 114 are in particular provided as permanently preset optical filter banks (within the higher-level network nodes R2, R2 ') and hold an optimally filtered WDM spectrum at the output for each fault. The WDM spectra from both directions (ie on the first and on the second wavelength-selective switches 111, 112 and at the third and at the fourth wavelength-selective switch 113, 114) are added in each case with optical couplers - simple optical couplers in particular can be used for this. The first or second switch 141, 142 is designed in particular as a fast optical multiswitch and in the event of a fault - controlled, for example, by a preferably simple multiport power meter or else a spectrally resolving multiport monitor as the power monitor - selects the WDM spectrum that covers all optical transmission channels (ie contains all the wavelengths used on the optical transmission link 150).

The optical filter banks are realized 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 would have the disadvantage, however, that any wavelength assignment or change during the operating phase would not be possible or would only be possible with additional effort.

Since the optical transmission link 150 has a number of n network elements (R1-1, R1-2, ...) <maths id="math0001" num=""><math display="block"><mrow><mi mathvariant="normal">n</mi><mo>+</mo><mn mathvariant="normal">2</mn></mrow></math><img file="EP3242425A1_D0001.tif" /></maths> Has fiber segments, it is advantageous if <maths id="math0002" num=""><math display="block"><mrow><mi mathvariant="normal">n</mi><mo>+</mo><mn mathvariant="normal">3</mn></mrow></math><img file="EP3242425A1_D0002.tif" /></maths> first and second outputs 115, 116 are provided, so that one of the first and one of the second outputs 115, 116 is present for each fault (operating mode) (for example a fiber break on a fiber segment) and additionally also for the normal operating mode.