Optical switching system.

[Detailed Description of the Invention]

[Industrial Application] The present invention relates to the digital signal systematized by the block of information, and the communication method which uses what is called a packet, and relates especially to an optical exchange method. [Description of the Prior Art] In various art tested towards realization of a broadband communication network now, especially asynchronous time sharing ATD art attracts attention. It is because it sees theoretically at least, is single art, and it is the only net which can unify many communications rather than being able to set at different Noodle speed. Since this art is based on exchange of the packet which has an address label, it is related to "high-speed packet-switching" art or "label address exchange." The very promising net which enables use of label address exchange art, A paper "ATD exchange network", pro Seedings of and GSLB-seminar-on broadband switching (Proceedings of GSLB-Seminar on Broadband Switching)-Portugal, Arve failure, It is indicated to 225th page ~ the 234th page for January, 1987 19~20 days. This net is constituted so that a packet may carry out the self designation of the course within the net. It is based on a small number of exchange elements (typically 2x2). That is, only 1 A bit of a label is investigated in each stage, and it is determined based on the value to which [ of the two outputs ] the packet should progress. Since this type of net is usually blockaded, each connecting point of a net needs a buffer memory, and the packet as which that output course is already grasped by that input stands by within that buffer memory. as a result, a net is not time transparent, and To traffic has been distributed at random since an ON intermediary, and the ratio of signal's existence time and unattended time is small -- that efficiency will become higher if it becomes. According to present technical C-MOS and eight parallel channels, all the throughputs of the net of 128x128 may amount to severalG bit per second. A throughput may be increased by other art. For example, the size may be increased by ECL a single figure. Optical art may be mentioned to others. However, if it sees from a viewpoint of exchange, optical art is adding restriction to the performance rather. For example, although there are few inputs and outputs, the big attenuation (several decibels) and big cross-talk (several +dB) in (it is a result in which even 8x8 is remarkable), the matrix which has rather big size (several centimeters), or an input/output may be mentioned as a problem. The latest available most promising device for optical exchange is usually commercially obtained by diffusing a titanium optical guide in the substrate of lithium niobate. Directive cutlet plastic Also is based on X-connection. The device which has X-connection is indicated to 143rd page ~ the 151st page of a paper "outline of optical exchange", and pro Seadings quoted previously, And it is indicated to 81st page ~ the 88th page for directive cutlet plastic Is a paper "high-speed optical time sharing and space division exchange", pro Seedings of and IOOC-ECOC 85, Venice, and October, 1985 1~four days. These days, the matrix (it is 16x16 by 12x12 and X-connection for example, at directive Kappura) of small capacity which is this type of device is assembled. It seems that it is suitable according to matrix structure since X-connection does not have the loss by crookedness. However, it needs high drive voltage. The performance with these imperfect elements is compensated by very wide bandwidth (several 10 GHz) and very short switching time (number + pico second). These characteristics make interesting use of the optical element in the exchange network with which small size is common and the bandwidth for increasing the ratio of signal's existence time and unattended time may be used. [Problem(s) to be Solved by the Invention] So far, neither the optical (used as object for self-course specification in net) logical device of practical use nor an optical storage cell can be obtained. For this reason, in the near future, an optical exchange element does not consider that it may be used by it like although used in electric art. [Means for Solving the Problem] Therefore, exchange network based on optical asynchronous art needs a system configuration which performs a logic function around a net and does not need a storage cell for an inside of a net. An optical exchange method of the present invention solves the above-mentioned problem, and it makes high-speed packet switching possible with exchange network which consists of an optical device. The negativity cross-talk effect is removed and an assembly of a net is easy. An optical exchange method with which an input channel which transmits data packet-ized according to the present invention is changed at a time to one output channel is provided, and it is the optical exchange method, A packet of an unspecified input channel is compressed with a time compression machine, and is changed into a lightwave signal, and is sent to optical exchange network at a suitable moment, is changed to a desired output channel, and ranks next, It is re-changed into an electric signal, and is elongated to those first time required with a time extension machine, and they are this, An output channel is formed and a change of an input channel to an output channel is characterized by being controlled by a prime controller which controls the optical exchange network via a drive circuit. The feature of the present invention will become clear with the following statement about an example and an accompanying drawing which are given as an un-restrictive example. [Example] in the block diagram of Drawing 1 -- reference marks I1 and I2 and ... Ip ..., In, O1 and O2, and ... Oq ... and On show the input and output of a switchboard, respectively -- the switchboard -- time compression machine TC1 and TC2, ...... TCp ......, TCn, and time extension machine TE1, TE2, and ...... TEq -- it comprises ......, TEn, and optical exchange network RC. Each block is connected to drive circuit LC, and this drive circuit LC is connected to prime controller EL via wire connection C. This prime controller is sent from the circuit which sends out a signal. Information required to control a switchboard comes to hand via wire connection S. It is assumed that it is what is denoted by the active state in general input Ip, or diagram Ip in the 2nd figure now. That is, it presupposes that it is a data block which arrives at a random moment and has various Is the time required. In this case, the probability exceeding the value which has the time required, for example decreases exponentially. The function of time compression machine TCp receives a data block, and includes transmitting it in shorter time as shown in diagram I'p=O'q in the 2nd figure. Operation contrary to this is performed with time extension machine TEq, and the input O'q is connected to output I'p of TCp via optical exchange network RC (Drawing 1). Optical exchange network, a time compression machine, and a time extension machine are driven by drive circuit LC controlled by prime controller EL. The data block re-elongated by TEq is shown by diagram Oq in the 2nd figure. When the capacity of optical exchange network RC assumes that time compression / extension is infinitely infinite now, the probability that two packets will pass optical exchange network simultaneously may be decreased at will by increasing time compression. In fact, there is a limit determined as the above-mentioned probability by physical restriction of a device. However, supposing a time compression machine has memory capability temporarily, when optical exchange network is already occupied by the data block, other data blocks may be delayed only to required time. Since time transparent of the system is carried out as for neither a guarantee nor a demand, that does not leave a problem. Under these conditions, optical exchange network does not need memory capability for the exchange element. This type of exchange network may comprise an element which can take two states directed by a sign "X" and "=" all over the 3rd figure. Without colliding mutually, from inputs a and b, it passes to outputs a and b directly, respectively, and two flows go output by "X" state. In the "=" state, an output interchanges mutually and, as a result, inputs a and b are connected to output b' and a', respectively. The exchange network which has n inputs and n outputs (nxn) is shown in Drawing 4. It may comprise two sequences in which each contains n exchange elements. reference mark X11, X12, and ... X1p -- the element of the 1st sequence is shown ... and X1n -- and reference marks X21 and X22 and ... X2q -- the element of the 2nd sequence is shown ... and X2n. n inputs I'1, I'2, and ... I'p ... and I'n are connected to input a of n elements of the 1st sequence -- and n outputs O'1, O'2, and ... O'q ... and O'n are connected to output a' of n elements of the 2nd sequence. While output a' of the element of the 1st sequence is connected to input a of the element to which the 2nd sequence corresponds, each output b' is connected to input b of the next element for every sequence. The element of the 2nd sequence needs to care about that the upper and lower sides become reverse to the element of the 1st sequence. The theoretical capacity of exchange network is the maximum and equal to the capacity of one connection used without playtime. 10G bit per second may be attained by the optical component. With the very simple rule of investigating the input index and output index which are contained in the label of the packet which exists in an input, course specification is performed to one packet at once. Supposing the packet which has an index of output O'q exists in input I'p, a course specification strategy will be extracted only to the following three cases. a p<q : point X1p and X1q are activated; b p>q : point X2p and X2q are activated; c p=q : neither of the points is activated. After an internal circuit is established, high-speed passage of the packet in exchange network is attained. The next connection is investigated after that. Although cocurrent connection is impossible in this example, in order to make it intelligible, two connection between the input and output which have small output ordinal number I'n-O'q from large output ordinal number I'1-O'2 and a large inputting order ordinal number is shown in Drawing 4 from a different ordinal number, i.e., a small inputting order ordinal number. Such exchange network may be carried out by the optical art using the exchange element which consists of X-connection, and as it stands in a line on the same substrate, the exchange element is arranged so that it may be seen in Drawing 5. The parallel optical guide of n book is lithium niobate (LiNbO), for example.₃By diffusing titanium in inside, it is formed on the substrate of a suitable material. A metal electrode for the optical guide of two more to impress the electric field which is formed by the method mentioned above and controls connection by an angle equal to beta and 180-beta on each intersection is formed, and it comes out. If angle beta is small enough, it is L=n-d/beta and, as for the parallel minimum length of an optical guide, and d, those distance and n of L are those numbers, i.e., the number of input/output tracks, here. n is 34 supposing it is L= 100 mm, d= 50 micrometers, and beta= 0.0174 rad (1 degree). A distance required to form a drive electrode between two continuous intersections is 2.8 mm. Supposing it asks for 100-input / output exchange network which has the same physical size about a substrate, the crossing angle of 0.05 rad (2.86 degrees) is required, and the electrode comrade needs to care about being isolated only 1 mm. The above-mentioned value is LiNbO.₃It conflicts with The nature of. However, they may be attained by the technical improvement in the material field. If it assumes that A (l) is a line damping coefficient by an optical guide, and A (x) is the amount of attenuation by the exchange element in the "x" state, and A (=) is the amount of attenuation by the exchange element in the "=" state now, n is the number of an input/outputs, and the amount A of the maximum attenuation which will let exchange network pass if L is the length of an optical guide is equal to A=2 and A(=)+ (n-1) and A(X)+L-A(l). If it assumes that they are A(l) =0.02db/mm, A(x)=0.15db, and A(=) =0.5db to the case (L= 100 mm, n= 30) mentioned above, the amount A of the maximum attenuation will serve as A=2x0.5+29x0.15+100x0.02=7.35db. cross-talk in the output which has the same index as an input originates in the loss by one X-connection in the "=" state, and cross-talk in other outputs depends for it on one connection in the "x" state. cross-talk of 25db easily discriminable from a signal may be technically attained to single connection. The block diagram of the drive circuit which suited especially the above-mentioned exchange network is shown in Drawing 6. It possesses the main block which forms the time compression machine and drive circuit LC of Drawing 1. It enforces the method of preventing the concurrent access of many input signals. To some extent, this method is elaborate, for example, may be collision detection multiple access art or a round priority system. However, the simple scanning method is preferred by speed and the simplicity of composition. The data packet which consists of various numbers of octets reaches general series system input Ip of Drawing 6 from the next to the next. Under control of a prime controller, each octet is written in at the register of FIFO (first-in first-out) memory MEp, and data existence A bit is added to the suitable cell of each register. The cell is denoted by the dashed line all over the figure. the signal on line PR belonging to the last writing, simultaneously wire connection C of a octet of a data packet is activated by a prime controller. Parallel-in-series converter PSp arranged at the output of MEp changes into an in-series signal the parallel octet received from MEp by the high bit rate, and the in-series signal is sent to electric - light converter EOp via line 1. Optical fiber FOp is connected to the output of EOp, and the input to which the optical conversion network mentioned already corresponds. A periodic scanning signal is sent to line SC via wire connection C by a prime controller, and line SC is connected to S input of RS flip-flop SRp via 4-input AND gate ASp. This signal has a cycle depending on a transfer rate of a request which passes exchange network. And a phase is deviated by only time equal to what divided the cycle n by n to a similar scanning signal of other n-1 channel. Line BU common to all the channels carries the signal which means "exchange network in use" in an active state. this signal is inactivity -- if it becomes -- the time of the end of the writing of a packet (signal of an active state on line PR) -- and in accordance with a suitable time phase (scanning signal of an active state on line SC), S input of a flip flop is enabled and that output will be in an active state. R input is enabled, while the signal on line BU will also be in an active state via gate Pp (exchange network in use) and all the S inputs of other n-1 flip flop and the flip flop SRp concerned become inhibit as a result. The signal on line ABp connected to the output of SRp enables electric - light conversion by EOp which emits transmission of the octet from MEp, the parallel-in-series conversion in PSp, and a high bit rate optical packet corresponding after that by the above-mentioned phase. The signal on line ABp also enables the output of register RIp, and the destination address of a channel and 2 A bit in which the active state has a meaning of p>q and p<q are written in by the prime controller in the register RIp. q is an ordinal number of output Oq. Decoder DE common to all the channels reads the destination address supplied by RIp on wire connection 2, and changes the suitable signal of the output lines of n book, and on one corresponding line into an active state. In this case, the line which will be in an active state is the q-th line, and while the combination circuit relevant to an output which consists of ORq, ADq, and ACq is activated by this, it is activated with the signal on line ABp by the combination circuit relevant to an input which consists of ORp, ADp, and ACp. either of the states of p<q, p>q, or p=q in the output of register RIp -- therefore -- or either of gates ADp and ACp on line 3p and 4p is activated -- moreover -- it can also creep -- it is not activated. As a result, each element of optical exchange network is activated via line X1p or X2p. The same thing happens to output gates ADq and ACq activated in alternative by line 3q and the signal on 4q, and, thereby, an output exchange element is activated via line X1q or X2q. If all the octets and corresponding data existence A bit leave memory MEp, the signal on line BPp will be in an inactive state, therefore R input of flip flop SRp will be activated via the signal which shows that the exchange network which exists in gate ARp and line BU is in use. In a block diagram of Drawing 1, block TCp can respond to what consists of block MEp, PSp, EOp, and optical fiber FOp of Drawing 6. On the other hand, all the blocks of everything but Drawing 6 can respond to what is incorporated in drive circuit LC of Drawing 1. Time extension machine TEq is easily made by the circuit which performs operation contrary to the operation performed with a time compression machine. There is optical fiber connected to optical-electric transducer in the output of exchange network, and the serial-parallel converter and the FIFO memory follow this optical - electric transducer, and a FIFO memory supplies again the flow of the packet in an input, and the flow of the packet which has the same characteristic. Flip flop SRp (Drawing 6) outputs an enabling signal again on line ABp. It is clear this example's to be given only as an un-restrictive example. Modification and change are possible, without deviating from the claim of the present invention.

[Brief Description of the Drawings]

Drawing 1 is a block diagram of the optical switchboard which enforces the optical exchange method of the present invention, The top view of the substrate the schematic diagram and Drawing 4 where 1 set of time diagrams of the digital signal with which Drawing 2 exists in some points of an optical switchboard, and Drawing 3 express the state in which an exchange element is possible direct the block diagram of exchange network, and Drawing 5 instructs optical exchange network to be, and Drawing 6 are block diagrams of an exchange network drive circuit. I ...... An input, O ...... An output, TC ...... A time compression machine, TE ...... A time extension machine, RC ...... Optical exchange network, LC ...... A drive circuit, EL ...... [ ...... A decoder, RI / ...... A register, SR / ...... A flip flop, FO / ...... Optical fiber ] A prime controller, a ME......FIFO memory, PS ...... A parallel-in-series converter, EO ...... Electric-light converter, DE