KR20020041323A - OADM System and Method for protecting and recovering optical signal in ring shape WDM network - Google Patents

Abstract

PURPOSE: An OADM(Optical Add-Drop Multiplexing) system in a ring-type WDM(Wavelength Division Multiplexing) network and a method for protecting/recovering optical signals are provided to divide WDM optical signals into a working channel group and a protection channel group using optical splitters having a channel selection characteristic and to connect the two group using a pair of optical switches so that each channel group can execute an optical switching function independently in the event of network failure. CONSTITUTION: An OADM system consists of optical splitters(21,30), wide-area multiplexing parts(22,31), optical multiplexing parts(26,35), and optical couplers(29,38). The optical splitters(21,30) divide a ring-type WDM optical signal, inputted through an optical line, into a working channel group and a protection channel group. Each wide-area multiplexing part(22,31) separates the optical channels of each channel group individually. The optical multiplexing parts(26,35) binds the passed and added individual optical channels into the working channel group and the protection channel group again. The optical couplers(29,38) combine the bound channel groups into one WDM optical signal again and outputs it through the other optical line. Each wide-area multiplexing part(22,31) is composed of an optical switch(23,32) and a wide-area multiplexing element(24,33). Each optical multiplexing part(26,35) is composed of an optical multiplexing element(27,36) and an optical switch(28,37).

Description

OAM system and method for protecting and recovering optical signal in ring shape WDM network

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OMD system and an optical signal protection / recovery method in an annular wavelength division multiplexing network. The present invention relates to a wavelength division multiplexing (WDM) optical signal using an optical splitter having channel selection characteristics (or channel group selection characteristics). After dividing the (N channels) into a working channel group (N / 2 channel) and a protection channel group (N / 2 channel), each of the separated operating channel groups and protected channel groups is paired. By connecting the optical switch, each channel group can perform the optical switching function independently in the event of a network failure, thereby ensuring the scalability and reliability of the WDM system and also the survivability of the optical channels in the event of a unit failure. And a computer-readable recording medium recording an OMD system and an optical signal protection / recovery method in an annular wavelength division multiple network and a program for realizing the method. It is about.

Recently, due to the explosive increase in data-driven traffic, the introduction of WDM technology that can rapidly expand the capacity of the transmission network at low cost is in full swing.

A conventional WDM system is simply composed of point-to-point, and optically-to-electrical or electrical-to-electric devices are connected to subordinate devices by connecting conventional synchronous digital hierarchy (SDH) devices. After optical) conversion, it performs protection and recovery function to secure network survivability required in transmission network.

Advances in optical technology have resulted in the development of network components such as optical add-drop multiplexing (OADM) and optical cross connect (OXC), as well as various networks such as WDM-based ring networks without going through expensive SDH devices. As efforts are made to construct a network, there is a demand for developing an essential protection and recovery function in a transmission network.

In the conventional WDM network recovery technology, the concept of a unidirectional path switched ring (UPSR) or a bi-directional line switched ring (BLSR) developed in a conventional SDH network is adopted as it is.

These protection switching methods have been modified and supplemented for several years in the SDH network, which ensures excellent network survival in terms of protection and recovery.

In particular, BLSR is divided into 4f-BLSR composed of four optical fibers and 2f-BLSR composed of two optical fibers, which is advantageous not only in terms of economic efficiency but also in terms of bandwidth efficiency.

However, due to technical differences between SDH and WDM, there is a problem that it is not easy to apply 2f-BLSR protection switching to a WDM network in various aspects. That is, the application to the WDM is very complicated in terms of system configuration, and even if applied, there is a problem that a very high cost is required.

The 2f-BLSR protection switching method consists of two optical paths, a transmission channel divided into an operation channel and a protection channel, and then simultaneously transmits an operation channel and a protection channel to each optical path. Therefore, when a failure occurs in the optical fiber, the operating channel of the optical fiber is transferred to the protection channel of the other optical fiber and transmitted.

1A and 1B are conceptual diagrams illustrating protection and recovery of an annular optical transmission network connected by two optical fibers, and a method of protecting and recovering an annular optical transmission network connecting two optical fibers between two OADM nodes. .

Figure 1a shows a steady state of the annular optical transmission network, Figure 1b shows a failure state of the annular optical transmission network.

In the event of a failure in the line between OADM Node B and OADM Node C, the optical signal is transferred at Node B and Node C, respectively, as shown in FIG. 1B. This configuration is called 2f-OBLSR (Optical BLSR). The general OADM node configuration is shown in FIG. 2.

2 is an exemplary configuration diagram of a conventional OADM node having a 2f-OBLSR function.

In general, an OADM node having a 2f-OBLSR function is separated by a wide multiplexer (1, 9) and a wide multiplexer (1, 9) for separating a WDM optical signal into respective optical channels, as shown in the figure. An OADM unit 4, 12 that drops or adds each optical channel, and an optical multiplexer that binds each of the optical channels that are rearranged after being extracted and inserted by the OADM unit 4, 12 into one; 5, 13) and the like.

The wide multiplexer 1, 9 is composed of a wide multiplexer 3, 11 and an optical switch 2, 10, and the optical multiplexer 5, 13 is an optical multiplexer 6, 14 and an optical switch. It consists of (7, 15).

Here, in order to protect the optical signal in the event of a failure on the optical path, two optical paths (F1 and F2, F3 and F4) at the input terminal and the output terminal of the OADM node, respectively, with optical switches 2 and 15, 7 and 10, FIG. As described above, the light paths 16 and 8 are connected to each other.

Hereinafter, the operation of the 2f-OBLSR OADM node is as follows.

When a failure is detected in the left optical path of the OADM node, the optical path 16 is formed from the optical switch 15 to the optical switch 2, and the WDM optical signal input to F4 is extracted and inserted into the optical channel by the OADM unit 12, Light beam is transmitted to F3 via the light path "16".

On the other hand, if a failure occurs in the right optical path of the node, the optical path 8 is formed from the optical switch "7" to the optical switch "10", and the WDM optical signal inputted to F1 is extracted from the optical channel by the OADM unit 4 and After the insertion is made, it is transmitted in the light path F2 through the optical path "8".

3A to 3C are explanatory diagrams for the configuration and function of the OADM unit in FIG. 2.

FIG. 3A shows a detailed configuration of the OADM units 4 and 12 of FIG. 2, in which, "17" and "20" are the wide multiplexing element and the optical multiplexing element, respectively, and "19" is the input and the output are 2, respectively. Represents a personal optical switch.

The optical switch 19 has two states in which the optical signal can pass through, add and drop, as shown in FIGS. 3B and 3C.

Thus, protection and recovery of all optical channels of the WDM optical signal are achieved in the event of a failure of the optical path.

However, there is a problem that there is no way to recover the optical channels if a failure occurs in any unit in the node.

In addition, in a WDM system, since a large number of optical channels are processed in one unit, and each optical channel has a transmission capacity of several gigabytes, protection and recovery measures for these units are urgently required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and operates wavelength division multiplex (WDM) optical signals (N channels) using an optical splitter having channel selection characteristics (or channel group selection characteristics). After dividing into a group (N / 2 channel) and a protection channel group (N / 2 channel), each of the separated operation channel group and the protection channel group is connected by a pair of optical switches, in case of network failure A computer-readable recording medium recording an OMD system and an optical signal protection / recovery method in an annular wavelength division multiple network and a program for realizing the method, which enable channel groups to independently perform optical switching functions. The purpose is to provide.

1A and 1B are conceptual diagrams illustrating protection and restoration of an annular optical transmission network connected by two optical fibers.

2 is an exemplary configuration diagram of an OADM node having a conventional general 2f-OBLSR function.

3A to 3C are explanatory diagrams for the configuration and function of the OADM unit in FIG.

4 is a diagram illustrating an embodiment of a 2f-OBLSR OADM system for implementing a multi-functional WDM network recovery function according to the present invention.

5 is a flowchart of an optical signal in a normal operation state in a 2f-OBLSR OADM node according to the present invention.

6 is a diagram illustrating an embodiment of a method of protecting and recovering an optical signal when a failure occurs in an optical path according to the present invention.

7 is a diagram illustrating an embodiment of an optical signal protection and recovery method when a unit failure occurs in an OADM node according to the present invention.

8 is a diagram illustrating an embodiment of an optical signal protection and recovery method when a failure occurs in an OADM unit according to the present invention.

* Explanation of symbols on main parts of the drawings

21, 30: optical splitter 22, 31: wide area multiplexing unit

23, 28, 32, 37: optical switch 24, 33: wide multiplexer

25, 34: OADM section 26, 35: optical multiplexing section

27, 36: optical multiplexer 29, 38: optocoupler

39 to 46: optical jumper cord

The present invention for achieving the above object, in the OADM (Optical Add-Drop Multiplexing) system in an annular wavelength division multiplexing (WDM) network, operating a wavelength division multiplexing (WDM) optical signal input through the optical path optical splitting means for separating a channel group from a guard channel group; First wide multiplexing means for separating each operating channel group and the guard channel group separated into the channel groups into individual optical channels; OADM means for extracting, inserting, or passing the respective separated optical channels, respectively; First optical multiplexing means for grouping individual optical channels passed / inserted by said OADM means into operational channel groups or protected channel groups, respectively; And an optical coupling means for combining the operation channel group and the protection channel group grouped into the channel group into one wavelength division multiplex (WDM) optical signal and outputting the same to another optical path.

Meanwhile, the present invention provides an optical signal protection / recovery method applied to an OADM (Optical Add-Drop Multiplexing) system in an annular wavelength division multiplexing (WDM) network. A first step of separating an optical channel from a working channel group and a protection channel group; A second step of dividing each of the operating channel group and the guard channel group separated into the channel groups into individual optical channels, and connecting the operating channel group and the guard channel group to each other for fiber channel switching in response to a failure; A third step of extracting, inserting, or passing the individually separated optical channels, respectively; A fourth step of grouping the individual optical channels passed / inserted by the third step into a management channel group or a protection channel group, respectively, and connecting the operation channel group and the protection channel group to each other for fiber channel switching according to a failure; And a fifth step of combining the operation channel group and the protection channel group grouped into the channel group into one wavelength division multiplex (WDM) optical signal and outputting the same to another optical path.

Meanwhile, the present invention provides an optical add-drop multiplexing (OADM) system having a processor for optical signal protection / recovery in an annular wavelength division multiplexing (WDM) network. (WDM) a first function of separating an optical channel from a working channel group and a protection channel group; A second function of dividing each of the operating channel group and the protected channel group separated into the channel groups into individual optical channels, and connecting the operating channel group and the protected channel group to each other for fiber channel switching according to a failure; A third function of extracting, inserting, or passing the individually separated optical channels, respectively; A fourth function of tying the individual optical channels passed / inserted by the third function back into the operation channel group or the protection channel group, respectively, and connecting the operation channel group and the protection channel group to each other for fiber channel switching according to a failure; And a program for realizing a fifth function of combining the operation channel group and the protection channel group grouped into the channel group into one wavelength division multiplex (WDM) optical signal and outputting the same to another optical path. To provide.

According to the present invention, in a transmission network comprising a Wavelength Division Multiplexing (WDM) transmission system in which a high-speed signal is loaded on each wavelength, the respective wavelengths are bundled together, and transmitted in one optical fiber. A signal protection and recovery technique. In particular, the present invention can protect and recover the optical signal in the event of a line failure, as well as the optical signal in the event of a line failure in a ring WDM transmission network composed of two optical fibers.

In short, the present invention, by using an optical splitter having a channel selection characteristic (or channel group selection characteristic), the working channel group (N / 2) of the large-capacity optical channels (N channels) constituting the 2f-BLSR WDM network Channel) and protection channel groups (N / 2 channels), and each of these separate operating channel groups and protection channel groups are connected by a pair of optical switches, so that each group can be independently switched in case of network failure. By configuring the system to perform a function, it is possible to secure the scalability and reliability of the WDM system, and to ensure the survivability of the optical channels even in the event of a unit failure. will be.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a diagram illustrating an embodiment of a 2f-OBLSR OADM system (node) for implementing a multi-functional WDM network recovery function according to the present invention.

The WDM Optical Add-Drop Multiplexing (WDM OADM) system (node) structure in which 2f-OBLSR (2fiber-Optical Bi-directional Line Switched Ring) protection switching function is introduced in the multi-functional WDM network recovery method of the present invention Same as FIG. 4.

As shown in the figure, an Optical Add-Drop Multiplexing (OADM) system (node) is provided with a working channel group and protection for an annular wavelength division multiple optical signal (large-capacity multi-channel signal) input through an optical path. Optical splitters 21 and 30 for separating the channel groups, the multiplexing units 22 and 31 for separating the optical channels of each operating channel group and the protected channel group, and extracting, inserting, or OADM units 25 and 34 for passing through, optical multiplexers 26 and 37 for tying the pass and inserted individual optical channels back to a management channel group and a protection channel group, and an operation channel group and a protection channel group grouped into a channel group, respectively. It is composed of an optical coupler (29, 38), etc. for outputting to another WDM optical signal by combining again to one WDM optical signal.

The wide area multiplexing units 22 and 31 may include optical switches 23 and 32 for connecting the operating channel group and the protection channel group to each other for protection switching, and the multiplexing elements 24 and 33 for separately separating the optical channels of each group. ) And the like.

The optical multiplexers 26 and 35 are optical multiplexing elements 27 and 36 that bundle individual optical channels into respective channel groups, and optical switches 28 and 37 which connect the operating channel group and the protection channel group to each other for protection switching. It consists of.

The configuration and function of the OADM units 25 and 34 are composed of optical switches as shown in Figs. 3A to 3C.

Optical switches A1 and A2 are optical jumper codes " 39 " and " 40 ", and optical switches B1 and B2 are optical jumper codes " in the multiplexer 22, 31 and the optical multiplexers 26, 35 in FIG. 41 "and" 42 ", optical switches C1 and C2 are connected by optical jumper codes" 43 "and" 44 ", and optical switches D1 and D2 are connected by optical jumper codes" 45 "and" 46 "respectively. It forms an optical path for protection switching in case of failure.

Meanwhile, operations for 2f-OBLSR protection switching of the OADM node (see FIG. 4) are the same as those of FIGS. 5 to 8.

N optical channels consisting of N / 2 operating channels and N / 2 protective channels travel in different directions in a network composed of two optical paths (F1 and F3, F4 and F2).

In the normal operation state, there are no protection channels in the two optical beams, only the operation channels proceed, and in the event of a failure, the operation channels and the protection channels proceed simultaneously. In other words, the operating channel in the optical path F1-F3 is a protection channel in the optical path F4-F2, the operating channel in the optical path F4-F2 is a protective channel in the optical path F1-F3.

5 is a flowchart of an optical signal in a normal operation state in a 2f-OBLSR OADM node according to the present invention.

In FIG. 5, optical jumper codes 39 to 46 of FIG. 4 are omitted for convenience.

The WDM optical signal E, which is input to the optical path F1 from one optical path F1 and F3, is divided into a management channel group and a protection channel group by the optical splitter 21, and the optical channels of the operating channel group receive the optical path W1. Through the optical channels, the optical channels of the protection channel group are respectively input to the wide multiplexer 22 through the optical path P1. At this time, there are no optical channels in the optical path P1 in the normal state.

The optical channels of the operating channel group input to the wide multiplexer 22 are input to the wide multiplexer "24" through the optical switch "23" (A1) and separated into individual optical channels. At this time, the optical switch "23" (A1) is in a pass through state (see FIG. 3B), and the optical path "39" and the optical path "40" are short-circuited.

Each of the optical channels separated by the wide multiplexer 24 is input to optical switches (" 19 " in FIG. 3A) of the OADM section 25, respectively.

In the OADM unit 25, the desired optical channels Ni and 0 <Ni <N / 2 are dropped, and the desired optical channels Ni and 0 <Nj <N / 2 are added again. Fiber channels that are not dropped are passed through. In this case, the added optical channels should match the wavelength of the dropped optical channels.

As described above, the optical channels that are passed through and added are input to the optical multiplexer 26, and are grouped into a single operating channel group by the optical multiplexer 27 in the optical multiplexer 26. After passing through the optical switch C1 is input to the optical coupler 29 through the optical path W1.

The operational channel group input to the optocoupler " 29 " is grouped together with the optical channels of the protection channel group that have passed through the optical path P1 and transmitted over the optical path F3. However, since there are no optical channels of the protection channel group in the normal operation state, only operating channels are transmitted to the optical fiber F3.

In the same way as the other optical path (F4 and F2), the flow of the optical signal (W) is formed, these constitute a 2f-OBLSR type OADM node proceeding in different directions.

6 is a diagram illustrating an embodiment of a method of protecting and recovering an optical signal when a failure occurs in an optical path according to the present invention.

For convenience, the optical jumper cords 39 to 46 of FIG. 4 are omitted in FIG. 6.

When a failure occurs in the left optical path of the OADM node, since the WDM optical signal W input to the optical path F4 does not proceed to the optical path F2, the optical switch D2 forms an optical path "45" with the optical switch D1. At this time, the optical switch is in a state as shown in FIG. 3C.

That is, the WDM optical signal W input to the optical path F4 is input to the optical multiplexer “35” through the optical splitter “30”, the wide multiplexer “31”, and the OADM unit “34” as described in FIG. 5. , "45-2" of the optical switch D2 is output.

The optical signal outputted by the optical switch D2 to "45-2" is input to the optical switch D1 "45-1" and sent to the optical coupler "29", which is bundled with the operation channel E of another optical beam and transmitted to the optical fiber F3. do.

In addition, the WDM optical signal E is not input to the optical path F1, and an adjacent OADM node connected to the left optical path of the node transmits the optical signal to the optical path F4 to be transmitted to the optical path F1 in the same manner.

The WDM optical signal E input through the optical path F4 is separated into the optical signal E and the optical signal W by the optical splitter "30", and the optical signal E is again "39-2" of the optical switch A2 for protection switching of the wide area multiplexer. Is output.

The optical signal E outputted to the "39-2" of the optical switch A2 is input to the "39-1" of the optical switch A1 of the wide multiplexer "22", and then the OADM unit "25" and the optical multiplexer "26". Is sent to the optocoupler " 29, "

That is, in the event of failure of the left light path of the node, optical paths "39" and "45" are formed between optical switches A1 and A2 and optical switches D1 and D2, respectively, to protect all optical channels.

On the other hand, when a failure occurs in the right light path of the node, optical paths 42 and 44 are formed between optical switches B1 and B2 and optical switches C1 and C2, respectively, so that all optical channels are protected in the same manner as described above. Here, the operations of the signals in the wide multiplexer 31, the OADM 34 and the optical multiplexer 35 are the same as those described with reference to FIG.

On the other hand, the OADM structure according to the present invention can protect the optical channels even in the event of a unit failure in the node.

7 is a diagram illustrating an embodiment of an optical signal protection and recovery method when a unit failure occurs in an OADM node according to the present invention.

For convenience, the optical jumper cords 39 to 46 of FIG. 4 are omitted in FIG. 7.

Hereinafter, a process in which the optical channels are switched and protected in the event of a failure in the optical splitter 21 or the wide multiplexer 22 will be described.

When the optical splitter "21" or the wide multiplexer "22" fails, the signal input to the optical path F1 cannot be processed. Therefore, in the adjacent OADM node connected to the optical path F1, the same method as described in FIG. WDM optical signal E is transmitted to F4.

Therefore, the operating channels E and W of the respective optical paths are input to the optical path F4, separated by the optical splitter " 30 ", and then through the optical path P1 and the optical path W2, respectively, the multiplexing part 31 and the OADM part. After passing through the 34 and the optical multiplexing section 35, the signals are output to "43-2" of the optical switch C2 and "45-2" of the optical switch D2, respectively.

The optical signals E and W output as "43-2" of optical switch C2 and "45-2" of optical switch D2 are input to "43-1" of optical switch C1 and "45-1" of optical switch D1, respectively. And are bundled together in the optocoupler " 29 " and output to the beam F3.

On the other hand, even when the optical splitter 30 and the multiplexer 31, or the optical couplers 29 and 38 and the optical multiplexer 26 and 35 fail, signal flow is formed in the same manner as described above, so that all optical channels Are protected. Here, the operations of the signals in the wide multiplexer 31, the OADM 34, and the optical multiplexer 35 are the same as those described with reference to FIG.

8 is a diagram illustrating an embodiment of an optical signal protection and recovery method when a failure occurs in an OADM unit according to the present invention.

For convenience, the optical jumper codes (39 to 46 in FIG. 4) are omitted in FIG. 8.

As shown in FIG. 3A, the OADM unit 25, 34 or 18 of FIG. 3A has optical channels processed by individual optical switches 19, and there is a possibility of failure of the OADM unit itself or each optical switch. do.

Each fibre-channel is a gigabit-capacity large-capacity that cannot be ignored. However, since the switching of the optical path in the event of failure of one optical channel puts a heavy burden on the entire network, when the failure of the OADM unit 25 (the failure of the entire OADM unit or the failure of the individual optical switch) occurs, Therefore, the optical channel is protected and recovered without changing the optical path as follows.

When a failure occurs in the OADM unit 25, the WDM optical signal E inputted to the optical path F1 is outputted to the " 40-1 " of the optical switch A1 and input to the " 40-2 " of the optical switch A2. 31), passing through the OADM section 34 and the optical multiplex section 35.

In the optical multiplexer 35, the WDM optical signal E is output to "43-2" of the optical switch C2, input to "43-1" of the optical switch C1, and transmitted to the optical path F3 via the optical coupler 29. Here, the operations of the signals in the wide multiplexer 31, the OADM 34 and the optical multiplexer 35 are the same as those described with reference to FIG.

That is, the WDM optical signal E changes the signal flow inside the node as shown in FIG. 8, but the transmission of the optical signals F1-F3 does not change, and the WDM optical signal W does not change the signal flow. Transmitted to F2, the optical channel is protected without switching the light path.

On the other hand, in the same way, when the OADM unit "34" is interrupted, the WDM optical signal W input to the optical path F4 is connected to the optical switch B2 to B1, passes through the OADM unit, and then is connected to the optical switch D1 to D2 and then the optical path F2 The WDM optical signal E proceeds through the optical paths F1-F3 without changing the signal flow as in the normal state of FIG. 5.

As described above, the present invention can apply not only UPSR or 4f-BLSR but also 2f-BLSR having high reliability and bandwidth efficiency to WDM, thereby improving network reliability and transmission band efficiency.

The method of the present invention as described above may be implemented in a program and stored in a recording medium (CD-ROM, RAM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

As described above, the present invention has the effect of protecting and recovering an optical channel in the event of a light path failure or a node failure (or an intra-node unit failure).

In addition, the present invention, in the event of a failure of the optical path, or in the case of an optical multiplexing unit or a multiplexing unit for processing multiple optical channels at the same time to switch all the optical channels to protect all optical channels, when the optical switch in the OADM unit or OADM unit In order to protect the optical channel by switching only the unit without switching the optical path, there is an effect that can increase the efficiency of network protection and recovery.

Claims (5)

In an OADM (Optical Add-Drop Multiplexing) system in an annular wavelength division multiplexing (WDM) network, Optical splitting means for separating a working channel group and a protection channel group from a wavelength division multiplex (WDM) optical signal input through an optical path; First wide multiplexing means for separating each operating channel group and the guard channel group separated into the channel groups into individual optical channels; OADM means for extracting, inserting, or passing the individually separated optical channels, respectively; First optical multiplexing means for grouping individual optical channels passed / inserted by said OADM means into operational channel groups or protected channel groups, respectively; And Optical coupling means for combining the operation channel group and the protection channel group grouped by the channel group into one wavelength division multiplex (WDM) optical signal and outputs the other optical path OADM system comprising a. The method of claim 1, The first regional multiplexing means, Optical switching means for connecting the operating channel group and the guard channel group with each other for switching the optical channel in the event of a failure; And Second multiplexing means for separating each operating channel group and the guard channel group separated into the channel groups into individual optical channels; OADM system comprising a. The method according to claim 1 or 2, The first optical multiplexing means, Second optical multiplexing means for grouping individual optical channels passed / inserted by said OADM means into operational channel groups or protected channel groups, respectively; And Optical switching means for connecting the operating channel group and the guard channel group to each other for switching the optical channel in the event of a failure OADM system comprising a. In the optical signal protection / recovery method applied to an OADM (Optical Add-Drop Multiplexing) system in an annular wavelength division multiplexing (WDM) network, Separating a working channel group and a protection channel group from a wavelength division multiplex (WDM) optical signal input through an optical path; A second step of dividing each of the operating channel group and the guard channel group separated into the channel groups into individual optical channels, and connecting the operating channel group and the guard channel group to each other for fiber channel switching in response to a failure; A third step of extracting, inserting, or passing the individually separated optical channels, respectively; A fourth step of grouping the individual optical channels passed / inserted by the third step into a management channel group or a protection channel group, respectively, and connecting the operation channel group and the protection channel group to each other for fiber channel switching according to a failure; And A fifth step of combining the operation channel group and the protection channel group grouped into the channel group into one wavelength division multiplex (WDM) optical signal and outputting the same to another optical path; Optical signal protection / recovery method in an annular wavelength division multiplexing (WDM) network comprising a. In the optical Add-Drop Multiplexing (OADM) system with a processor for protecting / recovering optical signals in an annular wavelength division multiplexing (WDM) network, A first function of separating a working channel group and a protection channel group from a wavelength division multiplex (WDM) optical signal input through an optical path; A second function of dividing each of the operating channel group and the protected channel group separated into the channel groups into individual optical channels, and connecting the operating channel group and the protected channel group to each other for fiber channel switching according to a failure; A third function of extracting, inserting, or passing the respective separated optical channels respectively; A fourth function of tying the individual optical channels passed / inserted by the third function back into the operation channel group or the protection channel group, respectively, and connecting the operation channel group and the protection channel group to each other for fiber channel switching according to a failure; And A fifth function of combining the operation channel group and the protection channel group grouped into the channel group into one wavelength division multiplex (WDM) optical signal and outputting the same to another optical path; A computer-readable recording medium having recorded thereon a program for realizing this.