Wavelength division multiplex transmission system and communication device

A wavelength division multiplex transmission system with substantial functions for avoidance of defects is provided. The system comprises an optical transmission device and an optical receiving device. The optical transmission device comprises an operating-system optical transmission unit and a standby-system optical transmission unit, and distributes transmission signals to be transmitted among a plurality of wavelength components, converts the signals into WDM signals, and transmits the WDM signals to a WDM transmission network. The optical receiving device comprises an operating-system optical receiving unit and a standby-system optical receiving unit, and restores WDM signals from the WDM transmission network into transmission signals. The operating-system optical transmission unit and/or the standby-system optical transmission unit has optical transmission unit internal defect avoidance means which, upon the occurrence of a prescribed number or fewer of wavelength component transmission defects, avoids defects within the optical transmission unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention concerns a wavelength division multiplex transmission system and communication device, and in particular, concerns defect-avoidance processing.

2. Description of Related Art

The current flow of technology for expansion of the capacity of optical communication systems may be broadly divided into time division multiplex (TDM) methods, and wavelength division multiplex (WDM) methods.

Here, in a WDM method, signals are modulated at, for example, 10 Gbps per channel. In each channel, signals modulated at different wavelengths are superposed by a four-channel WDM optical coupler (wavelength division multiplexer), and through transmission in a single optical fiber, transmission at 40 Gbps can be achieved. Compared with TDM methods, this WDM method has been regarded as superior due to its ease of upgrading, power division costs, ease of maintenance, and service flexibility.

In the case of WDM methods, a transmission signal is distributed among wavelength components for transmission, so that both the optical transmission device and the optical receiving device are provided with processing units accommodating each of the wavelength components. In the event that a defect occurs in any of the processing units accommodating a wavelength component, ordinary transmission will no longer be possible.

For this reason, it has previously been proposed that a redundant configuration of an operating system and standby system be employed, together with an optical transmission device and optical receiving device.

However, even if a redundant configuration is adopted, transmission is not possible when defects occur in both the operating system and the standby system. In order to avoid this phenomenon, provision of a plurality of standby systems is conceivable. However, in this case the equipment size is increased, so that practical accommodation is not possible.

In general, when a defect occurs in the operating system, the standby system is used in transmission, and while this standby system is being used, the operating system is restored to the normal state by replacement of parts or by other means. However, if there is a long length of time from occurrence of the defect until replacement of parts or similar in the operating system, the possibility of a defect occurring in the standby system during this interval is increased. Consequently, shortening of the time until part replacement is desired.

SUMMARY OF THE INVENTION

An object of this invention is to provide a wavelength division multiplex transmission system and communication device with substantial functions for avoiding defects.

In order to solve these problems, according to a first aspect of the invention, a wavelength division multiplex transmission system is provided in which transmission signals to be transmitted are distributed among a plurality of wavelength components, converted into WDM signals and sent to the WDM transmission network, and WDM signals from the WOM transmission network are restored to the above transmission signals. This system comprises an optical transmission device and an optical receiving device. This optical transmission device comprises an operating-system optical transmission unit and a standby-system optical transmission unit; the optical receiving device comprises an operating-system optical receiving unit and a standby-system optical receiving unit. The above operating-system optical transmission unit and/or the above standby-system optical transmission unit have optical transmission unit internal defect avoidance means which, upon the occurrence of a prescribed number or fewer of wavelength component transmission defects, avoids defects within the optical transmission unit.

According to a second aspect of this invention, a communication device used in a wavelength division multiplex transmission system is provided. This communication device has a defect detection means which detects defects in internal constituent members. This communication device further comprises defect occurrence member transmission means; when a defect is detected by the above defect detection means, defect occurrence member information is sent to an external maintenance member management terminal which performs management of maintenance members, supply processing, or similar.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(A) First Embodiment

With reference to the drawings, a detailed description of a first embodiment of the wavelength division multiplex transmission system according to the present invention will be herehinafter given.

It is suitable that the configuration of this first embodiment be the configuration of the operating system and/or standby system in a system adopting a redundant configuration, as in the fifth and sixth aspects described below.

(A-1) Configuration of First Embodiment

Referring toFIG. 1, the wavelength division multiplex transmission system of the first embodiment has a WDM transmission network1; an optical transmission device3which converts transmission signals (electrical signals) from a transmission terminal2into optical signals (WDM signals) and transmits the optical signals over the WDM transmission network; an optical receiving device4which changes WDM signals received from the WDM transmission network1into electrical signals and applies the electrical signals to the receiving terminal5; and a network management device6which is responsible for management functions for the WDM transmission network1, optical transmission device3, optical receiving device4, and similar.

In the WDM transmission network1, a plurality of nodes N are connected in, for example, a mesh shape or a matrix shape. Here, the wavelength components handled by the WDM transmission network1are assumed to be a plurality of discrete wavelengths, λ1to λn, extending from a short-wavelength end to a long-wavelength end. In this first embodiment, the internal configuration of each node N is omitted from the figure, but a WDM signal input from a given node can be exchanged (or switched) and output for each wavelength component.

FIG. 2is an explanatory figure illustrating transmission on different routes according to the wavelength component.

In the configuration example shown inFIG. 2, when a node N1is provided with a WDM signal containing all the wavelength components from λ1to λn from a certain node NS (not shown; this may also be an optical transmission device), a WDM signal containing wavelength components λ1and λ2is applied to node N3, and a WDM signal containing the wavelength components λ3to λn is applied to node N4.

When a WDM signal containing wavelength components λ1and λ2is applied to node N3from node N1, node N3applies a WDM signal containing wavelength components λ1and λ2to node N2. When a WDM signal containing wavelength components λ1and λ2is applied to node N3from a node (not shown) other than node N1, a WDM signal containing wavelength components λ1and/or λ2can be applied to a node (not shown) other than node N2. Explanation of exchange functions for the other wavelength components λ3to λn of node N3is omitted.

Similarly, nodes N4and N5have, at least, the exchange functions shown inFIG. 2with respect to WDM signals containing the wavelength components λ3to λn.

When a WDN signal containing wavelength components λ1and λ2is applied to node2from node N3, node N2applies to node ND (not shown; may also be an optical receiving device) a WDM signal containing wavelength components λ1and λ2, and when a WDM signal containing wavelength components λ3to λn is applied to node2from node N5, node N2applies to node ND a WDM signal containing wavelength components λ3to λn.

That is,FIG. 2shows an example in which, when sending a WDM signal containing all the wavelength components from λ1to λn from the node NS to the node ND, by means of the route exchange functions (exchange functions for each wavelength component) of the WDM transmission network1, the wavelength components λ1and λ2are transmitted via the route RT2, and the wavelength components λ3to λn are transmitted via the route RT1.

The above-described exchange processing for each wavelength component at each node may, for example, rely on labeling information, inserted into the optical signals for each wavelength component (for example, the header part), which indicates routes. Or, exchange processing may rely on control signals from the network management device6.

FIG. 3is a block diagram showing the detailed configuration of the optical transmission device3. InFIG. 3, signal lines for electrical signals are shown as thick lines, and signal lines for optical signals are shown as thin lines.

InFIG. 3, the optical transmission device3has a physical interface unit10, frame termination unit11, signal distributor12, optical channel cards13-1through13-n, wavelength division multiplexer15, transmission-side control signal processing unit17, and other components.

The physical interface unit10is responsible for physical interface functions with the transmission terminal2. The frame termination unit11performs termination processing for transmission signals (transmission frames) from the transmission terminal2.

FIG. 3shows the case in which one transmission terminal2is connected to the optical transmission device3. When there is a plurality of transmission terminals2, a physical interface unit10and frame termination unit11are provided at each transmission terminal2. Selection of transmission signals from each transmission terminal2may be performed by providing selection switches, or the signal distributor12may be endowed with these functions. Here the transmission terminals2need not be ordinary communication terminals, but may also be routers or similar.

The signal distributor12has functions for distributing transmission signals from transmission terminals2to the optical channel cards13-1to13-n, as optical channel units. In the case of a train of packet signals P1to Pn, for n transmission signals from a transmission terminal2, the signal distributor12distributes the packet signal P1to the optical channel card13-1, the packet signal P2to the optical channel card13-2, the packet signal P3to the optical channel card13-3, and so on, until the packet signal Pn is distributed to the optical channel card13-n. A plurality of packet signals may also be distributed to the same channel card. Such a distribution method relies upon control information from the transmission-side control signal processing unit17.

The signal distributor conforms to, for example, IMP (Inverse MUX for Packets (over SONET/SDH)).

The signal distributor12comprises a distribution unit12awhich actually executes distribution of signals, and a distribution control signal receiving unit (omitted inFIG. 3) which receives distribution control signals from the transmission-side control signal processing unit17, and applies the signals to the distribution unit12a. By this means, the signal distributor12distributes and applies to the optical channel cards13-1to13-n the transmission signals from the transmission terminals2, according to distribution control signals from the transmission-side control signal processing unit17.

The first principal function of each of the optical channel cards13-1, . . . ,13-n is electrical/optical conversion. A different wavelength λ1, . . . , λn is allocated to each of the optical channel cards13-1, . . . ,13-n. Each of the optical channel cards13-1, . . . ,13-n converts electrical signals (distributed transmission signals) applied from the signal distributor12into optical signals for the wavelength component λ1, . . . , λn allocated to that card, and applies the optical signal to the wavelength division multiplexer15via the corresponding optical fiber14-1, . . . ,14-n.

The wavelength division multiplexer15comprises, for example, an n:1 optical coupler; it performs wavelength multiplexing of the optical signals for each of the arriving wavelength components λ1to λn, and sends the WDM signals to an optical fiber16leading to the WDM transmission network1.

As explained above, in the WDM transmission network1, routes can be changed according to the wavelength component λ1, . . . , λn.

The second principal function of each of the optical channel cards13-1, . . . ,13-n is to send evaluation signals to evaluate routes for each wavelength component in the WDM transmission network1. Each of the optical channel cards13-1, . . . ,13-n sends an evaluation signal under the control of the transmission-side control signal processing unit17, notifies the transmission side control signal processing unit17of the timing with which evaluation signals are sent, and performs other operations. Specifically, each of the optical channel cards13-1, . . . ,13-n constitutes an optical channel unit.

The transmission-side control signal processing unit17is connected to the network management device6. This processing unit17has functions for, for example, specifying the details of distribution by the signal distributor12, and controlling the sending of evaluation signals from each of the optical channel cards13-1, . . . ,13-n. While a detailed discussion is omitted, the transmission-side control signal processing unit17is also responsible for monitoring of each of the optical channel cards13-1, . . . ,13-n, and when a malfunction occurs in any of the optical channel cards, notifies the network management device6or similar of this malfunction.

FIG. 4is a block diagram showing the detailed configuration of the optical channel cards13(13-1, . . . ,13n). InFIG. 4also, signal lines for electrical signals are shown as thick lines, and signal lines for optical signals are shown as thin lines.

The optical channel cards13have an LD (laser diode) light source20; an optical modulator21; a modulator driver circuit (inFIG. 4, denoted as a driver circuit)22; a clock control circuit23; a signal selection unit24; and an evaluation signal generator unit25.

Here, the LD light source20, optical modulator21and modulator driver circuit22are configured in order to convert ordinary electrical signals into optical signals. That is, the modulator driver circuit22drives the optical modulator21according to the electrical signal to be transmitted, and based on the clock frequency specified by the clock control circuit23, to modulate (for example, intensity modulation) optical signals (with the wavelength allocated to the optical channel card13) from the LD light source20, to output modulated optical signals. Of course a modulated light source, in which the light source is directly controlled for modulation, can also be employed.

In the case of this first embodiment, the optical channel card13has a clock control circuit23, signal selection unit24, and evaluation signal generator unit25.

The evaluation signal generator unit25generates an evaluation signal (electrical signal) for evaluation of the route and its transmission characteristics of the wavelength component of the optical channel card13in the WDM transmission network1, under the control of the signal selection unit24. The data pattern of evaluation signals is a pattern enabling discrimination from distributed transmission signals. Here the transmission timing is such that evaluation signals and distributed transmission signals are temporally differentiated. Further, the optical channel cards31-1, . . . ,13-n shown inFIG. 3, and more specifically, the evaluation signal generator unit25shown inFIG. 4is a constituent component of the transmission characteristic evaluation means.

Distributed transmission signals (electrical signals) are applied from the signal distributor12to the signal selection unit24, which at the same time is connected to the evaluation signal generator unit25. During intervals in which distributed transmission signals are applied by the signal distributor12according to control signals from the transmission-side control signal processing unit17, the signal selection unit24selects the distributed transmission signal and applies it to the modulator driver circuit22; during intervals in which distributed transmission signals are not applied by the signal distributor12, the signal selection unit24causes the evaluation signal generator25to generate evaluation signals, which are applied to the modulator driver circuit22.

That is, whereas distributed transmission signals (optical signals) having the allocated wavelength components are sometimes sent from the optical channel card13, evaluation signals (optical signals) having the allocated wavelength components are also sometimes sent.

In the case of this first embodiment, the period of the clock signal output by the above-described clock control circuit23of the optical channel card13can be varied by the network management device6(directly by the control signal processing unit17). That is, transmission speeds can be switched.

FIG. 5is a block diagram showing the detailed configuration of the optical receiving device4. InFIG. 5, signal lines for electrical signals are shown as thick lines, and signal lines for optical signals are shown as thin lines.

InFIG. 5, the optical receiving device4has a wavelength division demultiplexer30, optical receiving cards32-1to32-n, delay compensation unit33, multiplexer34, receiving-side control signal processing unit35, and other components.

WDM signals arriving from the WDM transmission network1via the optical fiber36are input to the wavelength division demultiplexer30of the optical receiving device4. The wavelength division demultiplexer30separates the arriving WDM signal into wavelength components λ1, . . . , λn, and applies the optical signals of each of the wavelength components λ1, . . . , λn to corresponding optical receiving cards32-1,32-n, as optical receiving units, via optical fibers31-1,31-n.

The detailed configuration of each of the optical receiving cards32-1, . . . ,32-n is omitted from thefigure; but after converting the optical signals of the wavelength components λ1, . . . , λn allocated to each card into electrical signals, discrimination is performed to determine whether these electrical signals are distributed transmission signals or evaluation signals. When arriving signals are distributed transmission signals, each of the optical receiving cards32-1, . . . ,32-n applies these distributed transmission signals to the delay compensation unit33. When arriving signals are evaluation signals, each of the optical receiving cards32-1, . . . ,32-n obtains evaluation information and applies this information to the receiving-side control signal processing unit35. As evaluation information, for example, the bit error rate (BER) can be employed. This bit error rate indirectly reflects the optical S/N ratio of the WDM transmission network. Instead of using the bit error rate as evaluation information, the evaluation signal may be subjected to waveform analysis in the state of optical signals, to directly obtain the optical S/N ratio. Specifically, each of the optical receiving cards32-1, . . . ,32-n constitutes an optical receiving unit.

Each of the optical receiving cards32-1, . . . ,32-n may also apply the evaluation signals themselves to the receiving-side control signal processing unit35, so that the receiving-side control signal processing unit35obtains evaluation information.

The delay compensation unit33compensates each of the input distributed transmission signals (electrical signals) for transmission delay based on differences in transmission routes in the WDM transmission network1for each wavelength component λ1, . . . , λn, and applies the result to the multiplexer34. Information on the compensated transmission delay time may be obtained from the receiving-side control signal processing unit35, or may be received autonomously by the delay compensation unit33according to header or other information.

The multiplexer34multiplexes the input plurality of distributed transmission signals, and returns these signals to the transmission signal which was to be transmitted by the optical transmission device3. Thereafter, this transmission signal is sent to a receiving terminal5by means of an interface circuit with the receiving terminal5or similar, not shown. Specifically, the optical receiving cards32-1, . . . ,32-n ofFIG. 5, or, the receiving-side control signal processing unit35, are constituent components of the transmission characteristic evaluation means.

The receiving-side control signal processing unit35is connected to the network management device6. This processing unit35provides evaluation information to the network management device6, controls the quantity of delay information for each wavelength component λ1, . . . , λn in the delay compensation unit33based on route setting information from the network management device6, controls the multiplexing method used by the multiplexer34(to accommodate signal distribution on the side of the optical transmission device3), and performs other operations. If there are wavelength components not used in the current communication, operation of the corresponding optical receiving cards may be prohibited, so as to suppress unnecessary power dissipation.

The receiving-side control signal processing unit35also monitors the occurrence of defects in each of the optical receiving cards32-1, . . . ,32-n. If a defect occurs in any of the optical receiving cards, the network management device6is notified of this fact.

FIG. 6is a block diagram showing the functional configuration of the network management device6. The network management device6may, for example, comprise information processing devices centered on a CPU which executes software; but the configuration shown inFIG. 6can also be employed, to implement functions for rerouting based on initial use, an NE malfunction, or at other times. The functions of each part are also clear from an explanation of operation, and so are briefly explained here.

InFIG. 6, the network management device6has, as principal components, information storage means40, optimal route selection means41, transmission efficiency optimization means42, route transmission quality adjustment means43, and communication means44. The network management device6, including, specifically, the principal components, operates as a wavelength component-specific route setting device.

The information storage means40has a transmission network configuration storage unit40a, route usage status storage unit40b, transmission quality information storage unit40c, and defect information storage unit40d, and other components.

The transmission network configuration storage unit40astores information on the configuration itself of the WDM transmission network1. The unit stores information on nodes comprised by the network (including information on exchange functions for each of the wavelength components λ1, . . . , λn), and information on optical fibers (physical paths) connecting nodes.

The route usage status storage unit40bstores information on routes for each wavelength component λ1, . . . , λn currently in use and on empty band capacity and other information for the routes of each wavelength component λ1, . . . , λn, associated with network configurations of the WDM transmission network1.

The transmission quality information storage unit40cstores evaluation information for the routes described above, and other information on transmission quality.

The defect information storage unit40dstores defect information for repeater nodes, optical fibers, and other network elements (NEs) in the WDM transmission network1, as well as defect information for optical channel cards13in the optical transmission device3and optical receiving cards32(32-1to32-n) in the optical receiving device4, and similar information.

The optimal route selection means41has an empty route search unit41aand empty route evaluation unit41b.

The empty route search unit41asearches for an empty route (in actuality, often a plurality exist) for each wavelength component λ1, . . . , λn, connecting the optical transmission device3and optical receiving device4which are the objects of routing. Here, the information stored by the transmission network configuration storage unit40aand route usage status storage unit40b, and other information, is referenced. Routes containing as elements NEs for which defects are stored in the defect information storage unit40dare excluded from the search.

For wavelength components for which not even one empty route is found, the empty route evaluation unit41bnotifies the transmission efficiency optimization means42that there are no optimal routes; for wavelength components for which a single empty route is found, the empty route evaluation unit41bnotifies the transmission efficiency optimization means42that that empty route is the optimal route; and for wavelength components for which two or more empty routes are found, the empty route evaluation unit41bevaluates those empty routes, determines an optimal route, and notifies the transmission efficiency optimization means42.

As necessary, the empty route evaluation unit41balso evaluates optimal routes for each wavelength component.

In order to determine the optimal route from a plurality of empty routes, evaluation signals are transmitted via each of the empty routes, and the optimal route is determined as the route for which the evaluation values, propagation time, and other transmission characteristics captured by the optical receiving device4are best. While differing from the explanation of operation given below, the optimal route may also be determined based on evaluate values captured, propagation times, and other information from the past (as recent as possible). When numerous empty routes have been found, the optimal route may be determined based on evaluation values, propagation times, and other information after first reducing the number of candidates on the basis of transmission distance, number of hops, or other criteria (that is, the transmission distance, number of hops, and other acceptance conditions may be imposed to reduce in advance the number of empty routes found). When there is a plurality of best empty routes, the optimal route may be determined based on the transmission distance, number of hops, or other criteria.

The transmission efficiency optimization means42has a band-transmission efficiency evaluation unit42a, a signal distribution determination unit42b, and other components. The band-transmission efficiency evaluation unit42aand signal distribution determination unit42bcoordinate to constantly revise the details of distribution of transmission signals to each of the optical channel cards13-1, . . . ,13-n. In this embodiment of the invention, as described in the section on operation, the transmission efficiency optimization means42functions during transmission of transmission signals. Prior to the beginning of transmission of transmission signals, the transmission efficiency optimization means42may evaluate the used band capacity and transmission efficiency, and determine the method of distribution of the transmission signals. The transmission efficiency may, for example, be a parameter which is higher when used band capacities are balanced for each route, and lower when used band capacities are in imbalance for each route.

In this first embodiment, in essence the inverse-multiplex method is considered, so that when an optimal route is obtained for wavelength components for the necessary number of channels or greater (if p shows number of channels, then p≦n), the transmission efficiency optimization means42makes a determination such that the transmission signal is distributed to p optical channel cards. In this determination, it is desirable, with respect to the transmission efficiency, that selection be performed from the wavelength components with greater empty band capacity, taking propagation delay into consideration.

The necessary number of channels p is, for example, the value obtained by dividing the amount of data of the transmission signal by the amount of data which can be handled in one transmission operation by each of the optical channel cards13-1, . . . ,13-n (the amount of data that can be accumulated in the buffer (not shown) within the optical channel card).

The route transmission quality adjustment means43mainly monitors the transmission quality (for example, the above-described evaluation information) for each route during transmission of transmission signals, and if the transmission quality drops, lengthens the clock signal period of the optical channel cards13-1, . . . ,13-n and otherwise tries to secure the minimum level of transmission quality. This monitoring of transmission quality is performed for, for example, wavelength components with little empty band capacity. Specifically, the route transmission quality adjustment means43ofFIG. 6constitutes the transmission quality management means.

The communication means44executes communication of control information between the optical transmission device3, optical receiving device4, and other components.

(A-2) Operation of the First Embodiment

Next, each type of operation of the wavelength division multiplex system of the first embodiment of this invention, having the configuration described above, is explained.

(A-2-1) Basic transmission operation

When a transmission signal is input to the optical transmission device3from a transmission terminal2, the transmission signal is distributed among each of the wavelength components λ1, . . . , λn according to the distribution details (distribution method) set by the signal distributor12. The distributed transmission signals (electrical signals) are converted into optical signals at prescribed respective wavelengths λ1, . . . , λn in each of the optical channel cards13-1, . . . ,13-n, and thereafter are wavelength-multiplexed in the wavelength division multiplexer15, and the WDM signal is sent to the WDM transmission network1.

In the WDM transmission network1, the WDM signal output from the optical transmission device3arrives at the opposing optical receiving device4, via the routes set for each of the wavelength components λ1, . . . , λn.

In the optical receiving device4, an arriving WDM signal is demultiplexed into optical signals with the wavelength components λ1, . . . , λn, respectively, by the wavelength division demultiplexer30, and the optical signals of the wavelength components λ1, . . . , λn are applied to the corresponding optical receiving cards32-1, . . . ,32-n, respectively. Each of the optical receiving cards32-1,32-n converts the optical signal for each of the wavelength component λ1, . . . , λn allocated to it into an electrical signal. After conversion, the delay compensation unit33compensates the electrical signals corresponding to each of the wavelength components for propagation delays due to differences in the routes of each of the wavelength components λ1, . . . , λn; the result is then multiplexed by an electrical multiplexer34, and the transmission signal to be transmitted by the optical transmission device3is regenerated and sent to a receiving terminal5.

(A-2-2) Initial route selection operation

Next, the flow chart ofFIG. 7is used to explain initial route selection operation, executed prior to the start of communication of transmission signals by the optical transmission device3and optical receiving device4, to determine which routes to select.

If the optical receiving device4which communicates with the optical transmission device3is fixed, and there are no changes between each communication, then upon introduction into the system of the optical transmission device3and optical receiving device4, the processing ofFIG. 7is executed.

Suppose that a transmission signal is applied from the transmission terminal2, so that the need to start new communication arises. In this case, the signal distributor12in the optical transmission device3divides the transmission signal into unit data amounts which can be handled by each optical channel card13-1, . . . ,13-n in a single transmission operation (limited data amounts at transmission rates corresponding to the existing connected WDM transmission network1), and accumulates the result internally, and at the same time notifies the network management device6of the need to start new communication (step S1).

At this time, the network management device6searches for empty routes for each wavelength component λ1, . . . , λn connecting the optical transmission device3and optical receiving device4which are to communicate, and notifies the optical transmission device3of this empty route information (step S2).

The control signal processing unit17of the optical transmission device3receiving this notification applies the empty route information for each of the wavelength components λ1. . . , λn to the corresponding optical channel cards13-1, . . . ,13-n. Each optical channel card13-1, . . . ,13-n labels the empty routes (one route, or a plurality of routes) such that evaluation signals (optical signals) having that wavelength component are transmitted over these routes, and then each of the optical channel cards13-1, . . . ,13-n transmits evaluation signals to the WDM transmission network (step S3).

In the optical receiving device4upon receiving evaluation signals from the WDM transmission network1via empty routes, each of the optical receiving cards32-1, . . . ,32-n determines the optimal route from among the single empty route or plurality of empty routes for that wavelength component, based on the evaluation signals for its own wavelength component; the network management device6is then notified of these optimal routes and transmission quality information (the evaluation information described above in this first embodiment), via the receiving-side control signal processing unit35(step S4). The network management device6can also be made to determine the optimal route from among one empty route or a plurality of empty routes for the same wavelength component.

The network management device6compares transmission quality information for the optimal routes for each wavelength component; based on the comparison results, determines (that is, specifies) the wavelength components (optimal routes) in the required number for use in transmission; and notifies the optical channel cards for the plurality of wavelength components thus determined of the optimal routes, while at the same time sending notification to instruct switching from the evaluation signal transmission state to the transmission state for transmission signals distributed on optimal routes (steps S5, S6). Instead of instructing direct switching to the transmission state for distributed transmission signals, instructions can instead be issued to switch to a state in which distributed transmission signals can be sent, with transmission of distributed transmission signals performed after the distribution method has been determined. At the time of selection and determination of optimal routes, the band capacity at the time the amount of signal distribution is added to the candidate empty routes is considered. For example, if q wavelength components are set to the same empty route, then if the band capacity for this empty route is exceeded, it is made the optimal route for (q−1) or fewer wavelength components.

Optical channel cards which have completed switching from the evaluation signal transmission state to the state for transmission of distributed transmission signals to optimal routes notify the network management device6of this fact (step S7), and the network management device6waits for notification of the completion of switching from all optical channel cards (step S8).

Having received notification of completion of switching from all optical channel cards, the network management device6or similar begins the signal distribution processing shown inFIG. 8.

When the initial route selection operation described above is completed, transmission signals are, for example, distributed equally among a plurality of wavelength components (optical channel cards) used in transmission.

(A-2-3) Signal distribution operation

Next, the signal distribution operation (signal distribution adjustment operation) is explained, referring to the flow chart ofFIG. 8. Signal distribution operation is executed not only during the start of communication described above, on completion of initial route selection operations in which wavelength components to be used and their optimal routes have been determined, but also upon completion of review of routes at the time of occurrence of NE defects, described below. In addition, this signal distribution operation is also executed periodically.

The network management device6evaluates the used band capacity (in other words, the empty band capacity) and transmission efficiency for all wavelength components (routes) transmitting distributed transmission signals (step S10).

Here, information for all NEs (network elements) existing on a route is managed by the network management device6, so that by evaluating the current state of traffic for each route and comparing the evaluations obtained with evaluations of band capacity allocated to that route, knowledge of empty band capacity can be obtained.

The network management device6constantly evaluates empty band capacity for all wavelength components during transmission, and in addition sends information to the signal distributor12so as to enable optimization of used band capacity and transmission efficiency, to cause revision of the distribution of signals to all wavelength components at which transmission is in progress (step S11). For example, in the case of routes (transmission paths) the transmission bands of which have equivalent capacities, signals are distributed to each wavelength component such that the same information quantities are sent via each route, taking the information transmission efficiency of the network into account.

Thereafter, the network management device6marks wavelength components for which there is sufficient empty band capacity (at or above a threshold value) after review of distribution, and maintains the empty band state for these wavelength components (step S12). Such wavelength components are utilized as wavelength components for switching in the event of occurrence of a defect in an optical channel card, described below.

After distribution review, the network management device6also sets, as objects for transmission quality management, those wavelength components for which there is no empty band capacity, or for which the empty band capacity is below the threshold value (step S13).

Wavelength components which have been set as objects for transmission quality management are subjected to transmission quality evaluation at prescribed intervals and also to transmission speed control, as shown inFIG. 9, explained below.

(A-2-4) Operation for evaluation and control of transmission quality

Next, operation is explained, referring to the flow chart ofFIG. 9, in which transmission quality is evaluated for wavelength components which have been set as the objects for management of transmission quality, and control is performed accordingly.

When setting a prescribed wavelength component as an object for transmission quality management, step S13in the above-describedFIG. 8is used.

At each prescribed period, or when processing by step S23is completed in operations on the occurrence of a defect in an optical channel card, described below, the network management device6begins the processing ofFIG. 9. Then, for wavelength components which are the objects of transmission quality management, the management device6reads transmission quality information from the optical receiving cards of the optical receiving device4(step S15), and makes a pass/fail judgment on the state of the transmission quality (step S16).

For example, a CRC or other error detection code could be inserted into the distributed transmission signal for transmission (with processing performed by the signal distributor12or another component), and based on this, the bit error rate (BER) could be obtained as transmission quality information. Or, an evaluation signal could be added before or after the distributed transmission signal and transmission performed, and the BER could be obtained as transmission quality information based on the result of receiving the evaluation signal. By means of an aspect such as the modification of the first embodiment, described below, transmission quality information can be obtained directly by optical means.

If, for a wavelength component which is an object of transmission quality management, there is leeway in the transmission quality, the network management device6instructs the optical channel card of the optical transmission device3for the wavelength component to raise the clock frequency. On the other hand, if the transmission quality of the wavelength component is degenerated, the management device6instructs the optical channel card of the optical transmission device3for the wavelength component to lower the clock frequency. If the transmission quality is at the standard level, the management device6instructs the optical channel card of the optical transmission device3for the wavelength component to maintain the clock frequency (step S17). In other words, by executing reviews of the transmission speed (clock frequency) in accordance with the transmission quality, the optical channel card is controlled so as to achieve its optimal transmission speed.

(A-2-5) Operation on the occurrence of defects in optical channel cards and optical receiving cards

Next, the operation (rerouting operation) to review the distribution of distributed transmission signals when a defect occurs in any of the optical channel cards of the optical transmission device3, used in transmission of distributed transmission signals, is explained, referring to the flow chart ofFIG. 10. Specifically, constituent members which are the object of malfunction detection, such as for example optical channel cards13, are called as internal constituent members.

Even when a defect occurs in any of the optical receiving cards of the optical receiving device4, the operation shown in thisFIG. 10is executed.

When the network management device6either is notified by the optical transmission device3of the occurrence of a defect in any of the optical channel cards, or recognizes the occurrence of a defect in any of the optical channel cards of the optical transmission device3, after first finding empty band capacity in the wavelength components provided for transmission of distributed transmission signals based on information stored by the management device itself (see step S12inFIG. 8), a judgment is performed as to whether there are wavelength components with empty band capacity (steps S20, S21).

Then, if there is even one wavelength component having empty band capacity, the network management device6instructs the signal distributor12to distribute the transmission signal capacity (data capacity) which had been distributed to the optical channel card in which the defect occurred to all the wavelength components having empty band capacity, and by this means the method of distribution of transmission signals in the signal distributor12is modified (step S22).

After the conclusion of the processing shown inFIG. 10, when the above-described processing ofFIG. 8is begun, the presence or absence of empty band capacity is confirmed for wavelength components for which band capacity (data capacity) have been added, and as a result, wavelength components are set as objects for transmission quality management as necessary. When a wavelength component is set as an object for transmission quality management, the above-described processing shown inFIG. 9is executed.

On the other hand, when there exist no wavelength components having empty band capacity, the network management device6instructs the signal distributor12to distribute transmission signal capacity (data capacity) which had been distributed to an optical channel card (wavelength component) in which a defect has occurred to all wavelength components currently used in transmission other than the wavelength component of the optical channel card in which the defect has occurred. By means of this instruction, the method of distribution of transmission signals in the signal distributor12is changed, and at the same time clock frequencies are lowered to accompany the addition of data capacity (step S23). After this processing, instead of returning to the main routine, the above-described processing ofFIG. 9(processing to control transmission speeds according to transmission quality) is immediately executed. As is easily understood from the above explanation, when a defect occurs in an optical channel card13or optical receiving card32, the network management device6performs a distribution review operation (rerouting operation), and operates to avoid internal defects; hence this network management device6functions as an optical transmission unit internal defect avoidance means.

The reason for lowering clock frequencies as described above is to prevent in advance the possibility that adequate transmission quality cannot be maintained owing to the addition of data quantities in a state in which there is no empty band capacity.

(A-2-6) Operation upon occurrence of defects in network elements (NEs)

Next, operation to review the distribution of distributed transmission signals (rerouting operation) on the occurrence of defects in network elements (NEs) is explained, referring to the flow chart ofFIG. 11.

When notified by the WDM transmission network1that a defect has occurred in one of the NEs, or upon recognizing that a defect has occurred in one of the NEs, the network management device6treats the NE in which the defect has occurred as an element provided on routes, and searches for empty routes for all wavelength components, notifying the optical transmission device3of the information on these empty routes (step S25).

On receiving this notification, the transmission-side control signal processing unit17of the optical transmission device3provides the corresponding optical channel cards with the information on empty routes for each of the respective wavelength components, and after labeling the empty routes (one route, or a plurality of routes) such that evaluation signals (optical signals) having the wavelength components are transmitted on the routes, each optical channel card transmits an evaluation signal to the WDM transmission network1(step S26).

In the optical receiving device4, after being provided with evaluation signals from the WDM transmission network1via empty routes, each optical receiving card determines the optimal route from among one or a plurality of empty routes for that wavelength component, based on the evaluation signal of the wavelength component for that card, and notifies the network management device6of the optimal route and transmission quality information via the receiving-side control signal processing unit35(step S27).

The network management device6compares transmission quality information for the optimal routes for each wavelength component, and for each wavelength component determines the optimal route to replace the route which has until now been used, as well as notifying the optical channel card for the wavelength component responsible for the newly determined optimal route; at the same time, the management device issues an instruction to switch from the transmission state for evaluation signals to the transmission state for distributed transmission signals on optimal routes (steps S28, S29).

Optical channel cards which have completed switching from the transmission state for evaluation signals to the state enabling transmission of distributed transmission signals to new optimal routes notify the network management device6of this fact (step S30), and the network management device6waits for notification of the completion of switching from all optical channel cards instructed to perform switching (step S31).

Having received notification of completion of switching from all optical channel cards, the network management device6or similar begins the signal distribution routine shown inFIG. 8, described above.

When beginning the processing ofFIG. 8described above, the presence or absence of empty band capacity is confirmed for wavelength components (including other wavelength components) switched to new optimal routes from optimal routes passing through NEs in which defects have occurred. Based on the results of this confirmation, switched wavelength components are, as necessary, set as wavelength components as an object for transmission quality management. If a wavelength component is set as an object for transmission quality management, the processing shown inFIG. 9described above is executed, and the transmission speed is controlled appropriately.

(A-3) Advantageous Results of the First Embodiment

According to the wavelength division multiplex transmission system of the first embodiment of the present invention, optimal routes are selected for each wavelength component, in consideration of transmission characteristics and other information, so that satisfactory transmission characteristics can be achieved compared with conventional configurations.

Further, according to the first embodiment, the band capacity used and transmission efficiency for each wavelength component are judged, and data quantities are distributed dynamically among wavelength components, so that transmission efficiency of routes in use is appropriately divided, and as a result the concentration of data in a given route can be prevented.

According to the first embodiment, transmission quality is monitored for wavelength components with little or no empty band capacity, and clock frequencies are changed according to the transmission quality, so that a minimum transmission quality can be maintained for such wavelength components as well.

According to the first embodiment, even when a defect occurs in a network element, the optimal routes are re-selected, taking optical transmission characteristics into account, for each wavelength component of routes on which the element is provided as a route element, and redistribution of the data quantities for these wavelength components is performed. Hence congestion can be prevented, and compared with conventional configurations, the probability of circuit breaks arising in the event of occurrence of defects in network elements can be lowered.

According to the first embodiment, upon occurrence of a defect in an optical channel card or optical receiving card, data quantities for wavelength components related to the defect are simply redistributed to other wavelength components according to empty band capacity, so that measures can be taken promptly. In such redistribution, the clock frequency is changed appropriately for wavelength components the band capacity of which has become constricted, so that at least a certain degree of transmission quality can be maintained.

(A-4) Modification of the First Embodiment

In the above explanation of the first embodiment, various modified embodiments were also mentioned; in addition, a modified embodiment such as the example indicated below can be cited.

The method used to obtain information for evaluating routes or for determining transmission quality is not limited to that explained in the above first embodiment.

For example, in order to determine transmission quality or evaluate routes, if parameters such as optical power information in each of the wavelength components are necessary at the optical signal stage in the optical transmission device3, the optical transmission device3may be configured such that optical couplers18-1, . . . ,18-n are provided to branch the emitted light output from each of the optical channel cards13-1, . . . ,13-n, as shown inFIG. 12, and branched monitor light from these optical couplers is input to the transmission-side control signal processing unit17. In this case, there must be a photoelectric converter within the transmission-side control signal processing unit17.

Or, for example, in order to determine transmission quality and evaluate routes, if output light power information and other parameters from the optical transmission device3at the WDM signal stage is necessary, the optical transmission device3, as shown inFIG. 13, may be configured such that optical couplers18are provided which branch output light on the back-stage side of the wavelength division multiplexer15, so that branched monitor light from the optical couplers is input to the transmission-side control signal processing unit17. In this case also, there must be a photoelectric converter within the transmission-side control signal processing unit17.

Or, for example, in order to determine transmission quality and evaluate routes, the optical transmission device3may be configured such that an instruction signal or similar to cause the optical channel cards13-1to13-n to output evaluation signals (optical signals) is applied to the optical channel cards13-1to13-n from the transmission-side control signal processing unit17via the signal distributor12, as shown inFIG. 14.

Of course the modified embodiments of the optical transmission device3shown inFIG. 12throughFIG. 14may be combined freely.

For example, in order to determine transmission quality and evaluate routes, if parameters such as optical power information in each of the wavelength components of the received light in the optical receiving device4are necessary at the optical signal stage, the optical receiving device4may be configured such that optical couplers37-1, . . . ,37-n are provided to branch light incident on each of the optical receiving cards32-1, . . . ,32-n as shown inFIG. 15, and branched monitor light from these optical couplers is input to the receiving-side control signal processing unit35. In this case, there must be a photoelectric converter within the receiving-side control signal processing unit35.

Or, for example, in order to determine transmission quality and evaluate routes, if parameters at the WDM signal stage such as optical power information for the light input to the optical receiving device4are necessary, the optical receiving device4may be configured such that on the front-stage side of the wavelength division demultiplexer30is provided an optical coupler37to branch the output light, with branched monitor light from this optical coupler input to the receiving-side control signal processing unit35, as shown inFIG. 16. In this case also, there must be a photoelectric converter within the receiving-side control signal processing unit35.

Or, for example, in order to determine transmission quality and evaluate routes, the method by which the receiving-side control signal processing unit35captures evaluation and other information from the optical receiving cards32-1to32-n may be a method which captures the information via the delay compensation unit33, as shown inFIG. 17.

Of course the modified embodiments of the optical receiving device4shown inFIG. 15throughFIG. 17may be combined freely.

Because the transmission-side control signal processing unit17and receiving-side control signal processing unit35function by means of signals, in some cases they may be omitted.

Evaluation signals are transmitted at times other than when setting initial routes also. Such methods include, in addition to the method of dividing the transmission time for distributed transmission signals and the transmission time for evaluation signals, the method of intermixing distributed transmission signals and evaluation signals; or, after modulation of distributed transmission signals and evaluation signals while varying the method of electrical modulation, they may be superposed and converted into optical signals, and simultaneously transmitted.

(B) Second Embodiment

Next, a second embodiment of the wavelength division multiplex transmission system of this invention is explained in detail, referring to the drawings.

It is suitable that the configuration of this second embodiment be the configuration of the operating system and/or standby system in a system adopting a redundant configuration, as in the fifth and sixth aspects described below.

(B-1) Configuration of the Second Embodiment

FIG. 18is a block diagram showing the configuration of principal components of the optical transmission device3X of the second embodiment; parts which are the same or corresponding inFIG. 3for the first embodiment are assigned corresponding symbols.

In addition to the configuration of the first embodiment, the optical transmission device3X of this second embodiment is provided with an auxiliary optical channel card13-S. The auxiliary optical channel card13-S functions whenever a defect occurs in one of the optical channel cards13-1to13-n or in one of the optical receiving cards32-1to32-n of the opposing optical receiving device4X (seeFIG. 19). A wavelength component λ1, different from the wavelength components λ1to λn of the optical channel cards13-1to13-n, is allocated to the auxiliary optical channel card13-S; except for this fact, the internal configuration is the same as for optical channel cards13-1to13-n.

FIG. 19is a block diagram showing the configuration of principal components of the optical receiving device4X of the second embodiment; parts which are the same or corresponding inFIG. 5for the first embodiment are assigned corresponding symbols.

In addition to the configuration of the first embodiment, the optical receiving device4X of this second embodiment is provided with an auxiliary optical receiving card32-S. The auxiliary optical receiving card32-S functions when the auxiliary optical channel card13-S of the optical transmission device3X is functioning. Of course the auxiliary optical receiving card32-S performs receiving operations for the optical signal of the wavelength component λs; except for this fact, it is similar to the optical receiving cards32-1to32-n.

In the case of this second embodiment, the WDM transmission network1is configured so as to be able to accommodate optical signals with the wavelength component λs.

(B-2) Operation of the Second Embodiment

Next, each type of operation of the wavelength division multiplex system of the second embodiment of the present invention is explained. Operations other than operations when a defect occurs in any of the optical channel cards is similar to the operation of the first embodiment, and so an explanation is omitted.

FIG. 20is a flow chart showing the operations in the event of occurrence of a defect in any of the optical channel cards. Even when a defect occurs in any of the optical receiving cards, the operations ofFIG. 20are executed.

When notified by the optical transmission device3that a defect has occurred in one of the optical channel cards, or upon recognizing that a defect has occurred in one of the optical channel cards of the optical transmission device3, the network management device6sends the various parameters for the optical channel card in which the defect has occurred (for example, route, power, transmission speed) to the auxiliary optical channel card13-S, and by this means the optical channel card13-S is set in a state enabling transmission according to the various parameters (step S35).

Next, upon recognizing that settings have been completed, the network management device6instructs the signal distributor12to send to the auxiliary optical channel card13-S distributed transmission signals which had been distributed to the optical channel card in which the defect occurred (step S36). By this means, the auxiliary optical channel card13-S performs transmission of distributed transmission signals in place of the optical channel card in which the defect occurred (step S37).

If a defect occurs in one of the optical channel cards or optical receiving cards in a state in which the auxiliary optical channel card13-S and auxiliary optical receiving card32-S are already being used, operation similar to the operation in the first embodiment, shown inFIG. 10above, is executed.

(B-3) Advantageous Results of the Second Embodiment

According to of the wavelength division multiplex transmission system of the second embodiment of this invention also, advantages similar to those of the first embodiment can be obtained.

Further, according to the second embodiment, even if a defect occurs in one of the optical channel cards or optical receiving cards normally used in transmission, by providing an auxiliary optical channel card13-S and auxiliary optical receiving card32-S on the transmission side and receiving side respectively, transmission (defect recovery) can be performed without reducing the number of channels (number of wavelength components) of transmission signals. Hence a system can be realized which is more robust with respect to congestion than the first embodiment of the invention.

(B-4) Modification of the Second Embodiment

The system which was cited as a modification of the first embodiment also represents a modification of the second embodiment.

In the above explanation, the case in which there is one auxiliary wavelength component (optical channel card and optical receiving card) was described; but a plurality can be prepared as well.

Further, in the above explanation the route of the auxiliary wavelength component was the same as the route of the optical channel card or optical receiving card in which the defect has occurred; but the system may be configured such that a search for the optimal route is performed for the auxiliary wavelength component as well. This search may be performed after a defect has occurred in one of the optical channel cards or optical receiving cards. Or, the optimal route for the auxiliary wavelength component may be determined in advance at the time of determination of optimal routes for all wavelength components.

In the above explanation, the auxiliary wavelength component was fixed; however, the system may be configured such that the auxiliary wavelength component can be selected so that, when determining optimal routes for all wavelength components, the auxiliary wavelength component is, for example, the wavelength component for which the evaluation result was lowest.

Next, a third embodiment of the wavelength division multiplex transmission system of this invention is explained in detail, referring to the drawings.

It is suitable that the configuration of this third embodiment be the configuration of the operating system and/or standby system in a system adopting a redundant configuration, as in the fifth and sixth aspects described below.

(C-1) Configuration of the Third Embodiment

FIG. 21is a block diagram showing the configuration of principal components of the optical transmission device3Y of the third embodiment; parts which are the same or corresponding inFIG. 3for the first embodiment are assigned corresponding symbols.

In addition to the configuration of the first embodiment, the optical transmission device3Y of this third embodiment is provided with an auxiliary optical channel card13-t and optical switch (optical SW)19.

The auxiliary optical channel card13-t functions when a defect occurs in one of the optical channel cards13-1to13-n. This auxiliary optical channel card13-t of the third embodiment can capture, under instructions from outside, wavelengths within the range of the wavelength components λ1to λn for all the optical channel cards13-1to13-n. That is, the auxiliary optical channel card13-t is a variable wave length optical channel card.

FIG. 22is a block diagram showing an example of the detailed configuration of the auxiliary optical channel card13-t (variable-wavelength optical channel card) of the third embodiment; parts which are the same or corresponding inFIG. 4for the first embodiment are assigned corresponding symbols.

In the auxiliary optical channel card13-t ofFIG. 22, a variable-wavelength (tunable) LD light source20Y can be employed as the light source. The auxiliary channel card13-t is configured such that, by applying a wavelength instruction to this variable-wavelength LD light source20Y from the transmission-side control signal processing unit17, an optical signal having the desired wavelength can be sent.

The optical switch19(FIG. 21) selects n optical signals from among the optical signals from the optical channel cards13-1to13-n and the auxiliary optical channel card13-t, for a total of n+1 optical channel cards, and outputs these signals to the wavelength division multiplexer15, according to exchange instructions from the transmission-side control signal processing unit17.

For example, in a state in which no defects have occurred in the optical channel cards13-1to13-n ordinarily used in transmission, the optical switch19selects the optical signals from the optical channel cards13-1to13-n as they are, and applies them to the wavelength division multiplexer15.

Or, for example, in a state in which a defect has occurred in the optical channel card13-1, the optical switch19selects the optical signals from the optical channel cards13-2to13-n and from the auxiliary optical channel card13-t, and applies them to the wavelength division multiplexer15.

In the case of this third embodiment, the configuration of the optical transmission device3Y differs from that of the above-described first embodiment, but the configuration of the optical receiving device4is the same as that of the first embodiment.

(C-2) Operation of the Third Embodiment

Next, operation of the wavelength division multiplex transmission system of the third embodiment is explained. Operations other than operations when a defect occurs in any of the optical channel cards is similar to the operation of the first embodiment, and so an explanation is omitted.

FIG. 23is a flow chart showing operation when a defect occurs in one of the optical channel cards.

On being notified by the optical transmission device3that a defect has occurred in one of the optical channel cards (hereafter assumed to be card13-1), or on recognizing that a defect has occurred in one of the optical channel cards (13-1) of the optical transmission device3, the network management device6sends to an auxiliary variable-wavelength optical channel card13-t the various parameters (for example, wavelength, route, power, transmission speed) of the optical channel card13-1in which the defect has occurred, and by this means the auxiliary variable-wavelength optical channel card13-t is set to a state in which transmission can be performed according to the various parameters (steps S40, S41).

Through these settings, the auxiliary variable-wavelength optical channel card13-t is put into a state in which optical signals with the wavelength component λ1of the optical channel card13-1in which a defect has occurred can be sent. In other words, the auxiliary variable-wavelength optical channel card13-t becomes a pseudo-optical channel card13-1.

The network management device6instructs the optical switch19to perform exchanges such that optical signals from the auxiliary variable-wavelength optical channel card13-t are input to the input point of the wavelength division multiplexer15at which optical signals from the optical channel card13-1in which the defect has occurred had been input; as a result, the optical switch19changes to an exchange state conforming to this instruction (steps S42and S43).

After confirming that the variable-wavelength optical channel card13-t and optical switch19have executed the state changes and other instructions, the network management device6instructs the signal distributor12to apply to the auxiliary variable-wavelength optical channel card13-t the distributed transmission signals which had been distributed to the optical channel card13-t in which the defect had occurred (step S44).

By this means, the variable-wavelength optical channel card13-t behaves as if it were the optical channel card13-1in which the defect has occurred.

If a defect occurs in one of the optical channel cards while in a state in which the auxiliary variable-wavelength optical channel card13-t is already in use, the operation of the above-described first embodiment is executed.

(C-3) Advantageous Results of the Third Embodiment

According to the wavelength division multiplex transmission system of the third embodiment of the present invention also, advantages similar to those of the first embodiment can be obtained. In addition, through the third embodiment, the following advantages can be gained.

Similarly to the second embodiment, the configuration of the third embodiment also has provided an auxiliary optical channel card13-t; but because this auxiliary optical channel card13-t can accommodate variable wavelengths, it can, effectively, operate as an optical channel card in which a defect has occurred, and as a result there is no need to provide an auxiliary configuration in the optical receiving device4, nor is it necessary that the WDM transmission network1accommodate an auxiliary wavelength component.

(C-4) Modification of the Third Embodiment

The system which was cited as a modification of the first embodiment also represents a modification of the third embodiment.

In the above explanation, a configuration in which there is one auxiliary variable-wavelength optical channel card in the optical transmission device was described; but a configuration in which a plurality of auxiliary variable-wavelength optical channel cards are provided is also possible. When providing such a plurality of auxiliary variable-wavelength optical channel cards, these optical channel cards may be configured such that the variable wavelength ranges are different for each. For example, the first auxiliary variable-wavelength optical channel card may accommodate wavelengths from λ1to λm, and the second auxiliary variable-wavelength optical channel card may accommodate wavelengths from λ(m+1) to λn.

In the above, an auxiliary variable-wavelength optical channel card configured so as to employ a light source which itself is of variable wavelength was described; but of course the configuration to achieve variable wavelength is not limited to this. For example, a variable-wavelength optical channel card may be realized by having light sources for each wavelength component, and by selecting a signal from the plurality of light sources.

In the above, a configuration was described in which the optical transmission device is provided with an auxiliary variable-wavelength optical channel card and optical switch; but the optical receiving device may be provided with an optical switch and auxiliary variable-wavelength optical receiving card. That is, an optical signal with the wavelength component of an optical receiving card in which a defect has occurred may be applied to an auxiliary variable-wavelength optical receiving card via an optical switch, and the auxiliary variable-wavelength optical receiving card may receive and process the optical signal with that wavelength component.

Next, a fourth embodiment of the wavelength division multiplex transmission system of the present invention is explained in detail, referring to the drawings.

It is suitable that the configuration of this fourth embodiment be the configuration of the operating system and/or standby system in a system adopting a redundant configuration, as in the fifth and sixth aspects described below.

The configurations of the optical transmission device and optical receiving device in the wavelength division multiplex transmission system of the fourth embodiment can be respectively represented byFIG. 4andFIG. 5of the above-described first embodiment.

However, in this fourth embodiment, the detailed internal configuration of each of the optical channel cards13-1to13-n in the optical transmission device3differs from that of the first embodiment.

FIG. 24is a block diagram showing the detailed configuration of the optical channel cards13Z (13-1to13-n) of the fourth embodiment; parts which are the same or corresponding inFIG. 4for the first embodiment are assigned corresponding symbols.

In addition to the configuration of the optical channel card13of the first embodiment, the optical channel cards13Z of the fourth embodiment are provided with an auxiliary LD light source20Z and optical coupler26.

Upon the occurrence of a defect in the LD light source20, the auxiliary LD light source20Z emits continuous-wave light at the same wavelength as the LD light source20, in place of the LD light source20. Here, the auxiliary LD light source20Z is configured so as to incorporate functions for detection of the occurrence of defects in the LD light source20. For example, a configuration is assumed in which the interior of the auxiliary LD light source20Z comprises a photosensitive element which monitors light emitted from the LD light source20, so that when the optical power incident on the photosensitive element drops below a threshold value, it is assumed that a defect has occurred in the LD light source20, and emission operation of the auxiliary LD light source20Z is started.

The optical coupler26guides continuous-wave light emitted from the LD light source20, or continuous-wave light emitted from the auxiliary LD light source20Z, to the optical modulator21.

Next, operation in the event that a defect occurs in the LD light source20of an optical channel card13Z is briefly explained.

When a defect occurs in the LD light source20of an optical channel card13Z, switching from the LD light source20to the auxiliary LD light source20Z occurs, by means of the defect evasion function within the optical channel card13Z. Either the transmission-side control signal processing part17or the network management device6is notified of information during the period of this switching to the auxiliary LD light source20Z, and during this switching interval, the signal distributor12is controlled to perform transmission without using the optical channel card13Z. For example, prior to defect occurrence, switching is performed from a state in which a distributed transmission signal with n wavelength components is being sent, to a state in which a distributed transmission signal with n 1 wavelength components is being sent. Rather than redistribute data, for example, output from the signal distributor12to the optical channel card13Z is halted.

Then, after confirming that switching to the auxiliary LD light source20Z is completed, the system returns to the transmission state using the optical channel card13Z. That is, switching is performed from a state in which distributed transmission signals are sent using n−1 wavelength components, to a state in which distributed transmission signals are sent using n wavelength components.

According to the wavelength division multiplex transmission system of the fourth embodiment of this invention also, advantages similar to those of the first embodiment can be obtained. In addition, through the fourth embodiment, the following advantages can be gained.

According to the fourth embodiment, simply by making a slight change to the internal configuration of optical channel cards, defects in optical channel cards can easily be accommodated. In actuality, the LD light source20is a part in the optical channel card which frequently malfunctions; by providing an auxiliary system, a satisfactory effect as a defect-avoidance function is obtained.

Further, through simple control to stop the output of distributed transmission signals from the signal distributor12during the interval of switching from the LD light source20to the auxiliary LD light source20Z, and to resume the output of distributed transmission signals after the completion of switching, defects in light sources can be avoided.

In the above, the provision of LD light sources with an auxiliary system was explained; auxiliary systems may also be provided for the entirety of the optical processing system parts, including the LD light source and optical modulator.

Next, a fifth embodiment of the wavelength division multiplex transmission system of the present invention is explained in detail, referring to the drawings.

(E-1) Configuration of the Fifth Embodiment

FIG. 25is a block diagram showing the configuration of principal components of the wavelength division multiplex transmission system of the fifth embodiment; parts which are the same or corresponding in drawings for previously-described embodiments are assigned corresponding symbols.

InFIG. 25, in the wavelength division multiplex transmission system of the fifth embodiment also, the optical transmission device3W and optical receiving device4W are linked to each other through a WDM transmission network1.

The optical transmission device3W has an operating-system optical transmission unit3WA, a standby-system optical transmission unit3WS, and a system switch7. Though omitted inFIG. 25, the optical transmission device3W also has circuitry for interfaces with transmission terminals (one terminal, or a plurality thereof) at each layer.

The system switch7essentially provides transmission signals to the operating-system optical transmission unit3WA. When a defect occurs in the operating-system optical transmission unit3WA sufficient to necessitate exchange, transmission signals are applied to the standby-system optical transmission unit3WS, based on control information from a defect detection configuration, not shown, within the optical transmission device3W, and the network management device, not shown, and similar.

The operating-system optical transmission unit3WA has a signal distributor (so-called IMP)12A, optical channel cards13-1A to13-nA, wavelength division multiplexer15A, control signal processing unit17A, and other components. In the case of the fifth embodiment, the operating-system optical transmission unit3WA transmits such that all wavelength components pass through the same route, and in this respect the configuration is the same as in the prior art.

A difference between the operating-system optical transmission unit3WA and the prior art is that the control signal processing part17A monitors defects in the optical channel cards13-1A to13-nA, and, for defects in up to a prescribed number (for example, one) of optical channel cards, the signal distributor12A is instructed to distribute the transmission signals distributed [to cards in which] defects have occurred to other optical channel cards. Hence the signal distributor12A also differs from the prior art in that it supports such changes in signal distribution. Specifically, the control signal processing unit17A functions as part of the defect detection means. That is, the control signal processing unit17A monitors defects in the optical channel cards13-1A, . . . ,13-nA, and makes judgments on the presence of defects based on the results of detection by externally provided sensors and other detection means.

On the other hand, the standby-system optical transmission unit3WS functions when there occur defects in a number of optical channel cards in the operating-system optical transmission unit3WA which exceeds the prescribed number.

The standby-system optical transmission unit3WS has a signal distributor12S, optical channel cards13-1S to13-nS, wavelength division multiplexer15S, and other components. In the case of this fifth embodiment, the standby-system optical transmission unit3WS is configured so as to send and process all wavelength components so as to pass through the same route, in a configuration similar to that of conventional optical transmission devices.

The optical receiving device4W has an operating-system optical receiving unit4WA, standby-system optical receiving unit4WS, and system switch8. Though omitted inFIG. 25, the optical receiving device4W also has circuitry for interfaces with receiving terminals (not limited to one terminal) at each layer.

The system switch8selects the transmission signal received from the operating-system optical receiving unit4WA and transmission signal received from the standby-system optical receiving unit4WS, and sends it to the receiving terminal side, not shown; that is, it functions to switch between systems.

The operating-system optical receiving unit4WA and standby-system optical receiving unit4WS each have a wavelength division demultiplexer30A,30S, receiving cards32-1A to32-nA and32-1S to32-nS, and other components; it performs reception processing similar to that of conventional optical receiving devices. In the device shown inFIG. 25, the multiplexer unit34at the electrical signal stage is common to both systems. Of course, both systems may comprise separate multiplexer units as well.

(E-2) Operation of the Fifth Embodiment

In the wavelength division multiplex transmission system of the fifth embodiment, when a defect occurs in any of the optical channel cards of the operating-system optical transmission unit3WA while in the transmission state using the operating-system optical transmission unit3WA, the control signal processing unit17A instructs the signal distributor12A to distribute transmission signals to the other n−1 optical channel cards, and switching to a state of transmission of WDM transmission signals using n−1 wavelength components is performed.

Such processing is nearly the same as the processing shown in the flow chart ofFIG. 10for the first embodiment.

This measure, in which the number of distributed transmission signals is changed, is employed when the number of optical channel cards in which defects have occurred is equal to or less than a prescribed number (for example, one).

When the number of defects in the optical channel cards13-1A to13-nA in the operating-system optical transmission unit3WA exceeds the prescribed number, the system switch7causes transmission signals to be applied to the standby-system optical transmission unit3WS, and switching to a state in which transmission is by the standby-system optical transmission unit3WS is performed.

When the operating-system optical transmission unit3WA is restored to the normal state through replacement of units and parts or similar, the system returns to the state of transmission by the operating-system optical transmission unit3WA.

(E-3) Advantageous Results of the Fifth Embodiment

According to the wavelength division multiplex transmission system of the fifth embodiment of the present invention, even when a defect occurs in an optical channel card or cards in the operating-system optical transmission unit3WA, if the number of defects is equal to or less than a prescribed number, the defects can be avoided without switching systems.

From the absence of a need for system switching, there is the subsidiary advantage that, for example, line breaks and other risks upon malfunction of the system switch can be avoided. Further, restoration to normal is possible through the replacement of the optical channel cards in which defects have occurred, so that only a small quantity of operating system optical transmission units, which are large-size parts, must be stocked in consideration of the occurrence of defects.

In the case of adoption of a simple redundant configuration, if a defect occurs in an operating-system optical channel card, switching to the standby system is immediately performed; but if a defect has also occurred in a standby-system optical channel card (if duplicate defects occur), transmission is no longer possible. However, in the case of this fifth embodiment, even if a defect occurs in optical channel cards of the operating-system optical transmission unit3WA, if the number is within the prescribed number, transmission by the operating system can be continued. In the case of this fifth embodiment, switching to the standby system is performed when a greater number of defects occurs, so that the configuration of this embodiment has a higher degree of redundancy, and satisfactory functions for defect avoidance.

(E-4) Modification of the Fifth Embodiment

In the above explanation, a system was described in which the operating-system optical transmission unit alone can execute transmission operation with a small number of wavelength components (number of channels); as shown inFIG. 26, a control signal processing unit17S may be provided in the auxiliary-system optical transmission unit, enabling internal accommodation even when there are defects in a prescribed number or fewer of the optical channel cards13-lS to13-nS. Upon doing so, the degree of redundancy is further increased.

In the above explanation, a system was described with a configuration in which, at the time of occurrence of a defect in an internal optical channel card, the operating-system optical transmission unit can accommodate without executing system switching; conversely, the standby-system optical transmission unit alone may comprise such a configuration.

Further, in the above explanation a system was described in which all wavelength components pass through the same route between the optical transmission device and optical receiving device; but the technical concept in which routes are determined for each wavelength component, as in the above-described first through fourth embodiments, may also be introduced. In particular, it is desirable that the optical transmission device and optical receiving device of the above-described first through fourth embodiments be applied as the operating-system optical transmission unit and the operating-system optical receiving unit. By so doing, considerable transmission quality can be attained even if defects occur in some of the optical channel cards.

Next, a sixth embodiment of the wavelength division multiplex transmission system of the present invention is explained in detail, referring to the drawings.

(F-1) Configuration of the Sixth Embodiment

FIG. 27is a block diagram showing the configuration of principal components of the wavelength division multiplex transmission system of the sixth embodiment; parts which are the same or corresponding inFIG. 25for the fifth embodiment are assigned corresponding symbols.

Compared with the wavelength division multiplex transmission system of the above-described fifth embodiment, the wavelength division multiplex transmission system of the sixth embodiment differs in the configuration of the operating-system optical transmission unit3WA. The defect alarm population message communication unit50ofFIG. 27constitutes the defect alarm message generation means.

In the case of the sixth embodiment, the operating-system optical transmission unit3WA has, in addition to the configuration of the fifth embodiment, a defect alarm population message communication unit50.

When a defect occurs in any of the optical channel cards13-1A to13-nA in the operating-system optical transmission unit3WA, the defect alarm population message communication unit50sends, to the maintenance member management terminal51, via a prescribed communication network52(which may be leased lines), a defect alarm population message containing specific information on the optical transmission device3W and its optical channel cards.

Here, the defect alarm population message communication unit50may be realized as one function of the signal distributor12A and control signal processing unit17A.

The communication network52used for transmission of defect alarm population messages may be the WDM transmission network1, or may be a communication network different from the WDM transmission network1.

When the communication network52used for transmission of defect alarm population messages is the WDM transmission network1, a dedicated wavelength component used for transmission of defect alarm population messages is established, and optical signals with this wavelength component are used to transmit defect alarm population messages. In this case, the defect alarm population message communication unit50comprises an optical channel card.

The maintenance member management terminal51is provided in, for example, a warehouse which stocks maintenance members, or a so-called vendor company or similar which has delivered the optical transmission device3W. That is, the maintenance member management terminal51is provided in a company, division, or similar which is responsible for replacement of optical channel cards or other members in which defects occur.

The maintenance member management terminal51comprises an information processing device having functions to receive the above-described defect alarm population messages. When the maintenance member management terminal51receives a defect alarm population message, it performs the prescribed replacement processing (an example of replacement processing is explained in the section on operation).

(F-2) Operation of the Sixth Embodiment

In this sixth embodiment also, when a defect occurs in any of the optical channel cards13-1A to13-nA in the operating-system optical transmission unit3WA, transmission signals are redistributed to the other optical channel cards excluding the optical channel card in which the defect has occurred, and are sent to the optical receiving device4W.

By means of this operation, the defect alarm population message communication unit50sends to the maintenance member management terminal51, via the communication network52, a defect alarm population message containing specific information on the optical transmission device3W and the optical channel card in which the defect has occurred.

At this time, the maintenance member management terminal51may perform processing sufficient to sound an alarm and display the defect alarm population message; or, it may confirm inventory of the optical channel card of the defect alarm population message, if there is a card in stock, set a reservation for its use, and if there is no card in stock, issue an instruction to manufacture or to order a card from another warehouse. Further, a maintenance worker may reference schedules or other data and establish a date and time for replacement operation.

Further, the maintenance member management terminal51may transfer the defect alarm population message to another device as necessary.

(F-3) Advantageous Results of the Sixth Embodiment

According to the sixth embodiment also, advantages similar to those of the fifth embodiment are obtained. In addition the following advantages can be obtained.

According to the sixth embodiment, the system is configured such that, upon occurrence of a defect in an optical channel card, the defect alarm population message communication unit50sends a defect alarm population message too the maintenance member management terminal51, so that replacement of the optical channel card can be performed promptly. Further, to the extent that the defect alarm population message is sent in realtime, inventory management and manufacturing management are expedited, and smaller stock quantities can be anticipated.

(F-4) Modification of the Sixth Embodiment

In the above, a system was described in which a defect alarm population message communication unit50is provided in the operating-system optical transmission unit3WA; a configuration may also be adopted in which, in addition to this, or in place of this, a defect alarm population message communication unit is provided in the standby-system optical transmission unit3WS. A configuration may also be adopted in which a defect alarm population message communication unit is provided in the operating-system optical receiving unit4WA and standby-system optical receiving unit4WS. Further, a configuration may be adopted in which, in a system which does not adopt the redundant configuration of an operating system and standby system as in the first through fourth embodiments, a defect alarm population message communication unit is provided in the optical transmission device and optical receiving device. Of course, the member executing communication of defect alarm population messages is not limited to optical channel cards.

In the above, a system was described in which the defect alarm population message communication unit50transmits directly a defect alarm population message to the maintenance member management terminal51; but transmission of the message may also be via the network management device. In this case, the transmission-side control signal processing unit comprises the defect alarm population message communication unit50.

Further, a defect alarm population message communication unit may be provided in the transmission device and receiving device of a transmission system other than a wavelength division multiplex transmission system.

(G) Other Embodiments

In the above explanations of each embodiment of the present invention, a conception was explained in which there is one transmission terminal and one receiving terminal connected to the optical transmission device and the optical receiving device respectively; but a plurality of transmission terminals and receiving terminals may be connected as well. In this case, functions for switching of transmission signals between transmission terminals, and functions for switching received transmission signals between receiving terminals, may be performed by a signal distributor12incorporating buffer memory and a multiplexer34.

If the combination is possible, a wavelength division multiplex transmission system may be constructed by combining the optical transmission device of one embodiment with the optical receiving device of a different embodiment.

In the above, the case of one-to-one communication between an optical transmission device and an optical receiving device was described; but the technical concepts of this invention can also be applied to one-to-N communication.

In the above, it was shown that communication from an optical transmission device to an arbitrary optical receiving device is possible; the technical concepts of the presenst invention can also be applied to cases in which the optical receiving device which engages in communication with the optical transmission device is fixed. In this case, when the optical transmission device and optical receiving device are inserted into a system, searches for optimal routes for each wavelength component and other processing may be performed.

The configuration of the WDM transmission network is arbitrary, and may be a star shape, loop shape, mesh shape, or multiple networks of a plurality of loops. Further, the optical transmission devices and optical receiving devices of each of the above embodiments may be provided at intermediate nodes. For example, the technical concepts of this invention can be applied even when Add/Drop circuits and optical cross-connect (OXC) devices exist at intermediate nodes.

As explained above, with a construction of a wavelength division multiplex transmission system according to the invention, an optical transmission device comprises an operating-system optical transmission unit and a standby-system optical transmission unit; transmission signals to be transmitted are distributed among a plurality of wavelength components, converted into WDM signals, and sent to the WDM transmission network; an optical receiving device comprises an operating-system optical receiving unit and a standby-system optical receiving unit; and WDM signals from the WDM transmission network are restored to the above transmission signals. In this wavelength division multiplex transmission system, the above operating-system optical transmission unit and/or the above standby-system optical transmission unit have optical transmission unit internal defect avoidance means which, upon the occurrence of a prescribed number or fewer of wavelength component transmission defects, avoids defects within the optical transmission unit, so that the equivalent redundant configuration is expanded, and defect avoidance functions can be enhanced.

With a construction of a communication device according to the invention, there are provided defect detection means which detects defects in internal constituent members and defect occurrence member transmission means. The defect occurrence member transmission means, when the above defect detection means detects a defect, sends defect occurrence member information to an external maintenance member management terminal which performs management of maintenance members, supply processing, or similar. Accordingly, shortening of the time from defect occurrence to restoration of the normal state can be expected, and in this respect defect avoidance functions can be enhanced.