KR20010058245A - Uni-Directional Protection of OCH Signal Layer for the Multi-channel WDM Optical Transmission System - Google Patents

Abstract

PURPOSE: One direction changeover apparatus of optical channel layer to wavelength division multiplex optical transmission system is provided to perform continuously communication service by recovering obstruction of multi-channel WDM(Wave-length Division Multiplex) optical transmission system rapidly. CONSTITUTION: An optical splitter is located at optical channel section and transmits an optical signal to relay station signals dividing the multi-channel which is inputted into two optical signal with same wave-length. An optical switch part is located at optical channel section of reception side and select optical signal of normal state among the two optical signal(A signal, B signal) with same wave-length translated from the relay station. A first photo diode sense obstruction state of the optical signal A. A second photo diode sense obstruction state of the optical signal B. A selection controller output optical switch control signal to select one of the two optical signals according to the obstruction state of the two optical signal. An optical switch(24) output one of the two optical signals according to optical switch control signal which is output by the selection controller(23). A logical OR gate input obstruction state of the optical signal A and reset signal. An input board and S board input obstruction state signal of the signal A. Former optical switch control signal is inputted to input board. A selector outputs to select one of the two input boards according to signal level of the board S. A D-flipflop outputs output-signal of the selector according to clock inputted into the clock board and reset by output signal of the logical OR gate.

Description

Uni-Directional Protection of OCH Signal Layer for the Multi-channel WDM Optical Transmission System}

The present invention relates to a unidirectional switching device for performing a switching function applied to an optical channel (OCH) layer in a multi-channel wavelength division multiplexing (WDM) optical transmission system. In detail, the present invention relates to a switching device that can automatically recover from a network failure.

A multi-channel wavelength division multiplex (WDM) optical transmission system is a technique of multiplexing multiple optical signals into a single light beam without electrical conversion. WDM optical transmission system using this technology transmits hundreds of gigabits per second (Gbps) information in one transmission path, which can cause huge information loss and economic loss in the event of a line or device failure. Therefore, a switchover function for automatically recovering from these obstacles is required, and applying the switchover function to a WDM optical transmission system can improve the reliability and efficiency of the transmission network.

That is, the switching automatically repairs the line failure or the self failure in the transmission system caused by the fiber cable disconnection or the optical transmitter failure in the optical line.

The WDM optical transmission system is divided into three layers for each function, which is standardized in G.872 of ITU-T SG15. That is, it is divided into an optical transmission section, an optical multiplex section, and an optical channel section.

As a typical representative switching method, there is an automatic protection switching (APS) method using K1 and K2 bytes, which are transfer overhead in a synchronous transmission device. However, in this method, the switching is performed by using the overhead in the synchronous signal, and the switching is performed on the synchronous signal frame instead of the switching of the dependent signals to be multiplexed. However, in the present invention, the switching is applied to a plurality of dependent signals individually. In order to optically multiplex the dependent signals, the respective switching signals are individually switched to signals (OCH layer signals) converted to the assigned optical wavelengths. To provide. Therefore, the present invention is different from the existing transfer method, the target of the transfer application, and provides the transfer by each optical signal (or wavelength) to increase the efficiency of the transfer operation.

As another conventional switching method, there is a technique for performing the switching at the electrical digital signal level. However, the application of this technique to optical signals presents a problem: electrical signals, such as digital signals, do not attenuate during the operation of bridges and selectors, but optical signals have 3 dB of attenuation per signal when two signals are made. Occurs. Therefore, the switching technology for the optical signal requires the light output power of the laser diode that can sufficiently overcome this.

In the related art, a number of synchronous switching technologies have been published or patented. However, a switchover for a WDM optical transmission system has not been published. In particular, no prior patent relating to a switchover for a fiber channel section layer is found.

Accordingly, the present invention has been made to solve the problems of the prior art, a wavelength for preventing mass loss of information generated in the transmission network by automatically recovering the failure in the WDM network in a very short time. It is to provide a unidirectional switching device of an optical channel layer in a split multiple optical transmission system.

In addition, the present invention is to provide a unidirectional switching device of the optical channel layer in the wavelength division multiplex optical transmission system that can independently recover the failures generated in the unit of wavelength or the failures generated in the multi-channel optical path because it is configured independently for each wavelength. Do.

1 is a block diagram of a wavelength division multiple optical transmission system to which the present invention is applied;

2 is a structural diagram of an optical splitter and an optical switch in a general unidirectional switching;

3 is a detailed circuit diagram of the unidirectional selection controller of the present invention applied to FIG.

4 is a logic table of a selection controller applied to FIG. 2;

5 is a diagram illustrating a switching structure through a multi-channel wavelength division multiple link;

6 is a detailed configuration diagram of unidirectional switching in a single station WDM network.

In order to achieve the above object, in the wavelength division multiplexing optical transmission system according to the present invention, the unidirectional switching device of the optical channel layer is located in the transmission side optical channel section in the optical channel section hierarchy of the multichannel wavelength division multiplexing optical transmission system. An optical splitter that receives the multi-channel optical signal and divides the same optical signal into two optical signals for each wavelength and transmits the same to the relay station; and two optical signals (A signal and B that are located in the optical channel section on the receiving side and transmitted by the relay station) Signal) to select an optical signal in a steady state.

Preferably, the optical switch unit, the first photodiode for detecting a failure state of the optical signal A, the second photodiode for detecting a failure state of the optical signal B, the failure state of the two optical signals A selection controller for outputting an optical switch control signal for selecting one optical signal among two optical signals, and selecting and outputting one optical signal among the two optical signals according to the optical switch control signal output from the selection controller It characterized by including an optical switch to.

More preferably, the selection controller may include a logic sum gate through which a fault state signal of the B signal and a reset signal are input, a fault state signal of the A signal is input into an input terminal and an S terminal, and a previous optical switch control signal is input. A selector which is input to a terminal and selects and outputs one of two input terminals according to the signal level of the S terminal, and is reset according to an output signal of the logic sum gate, and an output signal of the selector according to a clock input to the clock terminal It characterized in that it comprises a D-flip flop to output.

Hereinafter, with reference to the accompanying drawings will be described in more detail the "unidirectional switching device of the optical channel layer in the wavelength division multiplex optical transmission system" according to an embodiment of the present invention.

1 is a block diagram of a wavelength division multiplexing (WDM) optical transmission system to which the present invention is applied. This is defined in G.872 of ITU-T SG15 and is divided into a single station WDM system (1) and a relay station type WDM system (4). The signal transmitted from the relay station type WDM system 4 is transmitted point-to-point by receiving it from the end station type WDM system 1. The WDM system includes a fiber channel section layer 13 for changing dependent signals to an assigned wavelength, an optical multi-layer layer 12 for multiplexing the dependent signals changed at each wavelength into a single optical path, and long-distance transmission of the multiplexed optical signals. It consists of an optical transmission section layer that is amplified and transmitted to the relay station type WDM system 4 in order to achieve this. The relay station type WDM system 4 has only an optical transmission section layer 41 as a 1-R relay station.

2 is a structural diagram of an optical splitter 2 and an optical switch 3 that perform an optical signal switching function in an optical channel section layer of a WDM transmission system. Each subordinate signal input to the WDM transmission system is converted into an assigned wavelength and then output as two optical signals (A signal, B signal) having the same wavelength through the optical splitter 2, and attenuated by about 3 dB. These two optical signals are transmitted to the optical switch 3 through different multichannel optical paths. The optical splitter 2 performs a permanent bridge function, and the optical switch 3 selects one of these two optical signals according to the fault condition.

That is, the photodiodes 21 and 22 of the optical switch 3 detect the Loss Of Signal (LOS) of the two optical signals received, and the selection controller 23 detects the failure of the two optical signals. Outputs an optical switch control signal for selecting one of the two optical signals according to the state, and the optical switch 24 alternates the optical switch in accordance with the optical switch control signal to select one of the A and B signals. Select and output the optical signal.

FIG. 3 is a detailed circuit diagram of the selection controller 23 shown in FIG. This selection controller generates an optical switch control signal in accordance with the signal disturbance state of the optical signal.

The optical switch 3 is a photodiode 21 for detecting a failure of the A signal and a photodiode 22 for detecting a failure of the B signal converts an input optical signal into an electrical voltage so that this voltage value is a signal failure. If it is lower than the LOS voltage value, it is transmitted to the selection controller 23. In addition, the selection controller 23 is input with a clock signal having an arbitrary frequency (Hz) and a reset signal for determining the initial state of the optical switch control signal in order to know the optical switch control signal in the previous state. Through these signals, the selection controller 23 selects one optical signal of the A signal and the B signal. The selection controller 23 is designed to operate according to the logic table of FIG.

As shown in FIG. 3, operations of the gates 231, 232, and 233 are as follows. Since the signal is initially designed to select the A signal, detailed operation will be described based on the A signal. The photodiode outputs a high logic level when a signal failure occurs, and a low logic level when a signal failure does not occur normally. The selectors 233 and 241 output a low logic level to the S terminal. It outputs the signal connected to the input terminal and when the high logic level is applied to the S terminal, it outputs the signal connected to the B input terminal.

In the detailed circuit diagram of FIG. 3, the failure state signal of the B signal and the reset signal are input to the OR gate 232. When the reset signal reaches a low logic level, the D-flip flop 231 is reset, so that the selection controller 23 outputs a low level optical switch control signal, and the selector 241 of the optical switch 24 outputs an A signal. Choose.

In addition, even if a failure of the B signal in the normal operation state, since the failure does not occur in the selected A signal, it is not switched from the A signal to the B signal.

However, if a failure occurs in the selected A signal, the selector 233 outputs a high logic level signal according to the state of the A signal. As a result, the D-flip-flop 231 outputs a high logic level signal and the selection controller. The optical switch control signal outputted at 23 becomes a high logic level. The selector 241 of the optical switch 24 thus selects the B signal.

As described above, the optical switch 24 has an optical switch control signal, which is an output signal of the selection controller 23, when the failure of the A signal occurs, becomes a high logic level, and is switched to select the B signal from the two signals received.

4 is an operation logic table of the selection controller shown in FIGS. 2 and 3. The conditions of unidirectional transfer are as follows.

First, when A signal is selected (optical switch control signal is low logic level),

-A signal is normal, B signal is normal: Select and maintain A signal.

-A signal is normal, B signal is faulty: Select and maintain A signal.

-A signal fails, B signal is normal: select and maintain B signal. The selection signal is switched from the A signal to the B signal to change to the case where the B signal is selected.

-A signal fails, B signal fails: Select and maintain A signal.

Next, when B signal is selected (optical switch control signal is high logic level)

-B signal is normal, A signal is normal: B signal is selected and maintained.

-B signal is normal, A signal is faulty: Select and maintain B signal.

-B signal is faulty, A signal is normal: Select and maintain A signal. The selection signal is switched from the B signal to the A signal to change to the case where the A signal is selected.

-B signal has failed, A signal has failed: Select and maintain A signal.

In this way, the transfer operation criteria are made so that the transfer can be operated based on the selection signal so that the transfer occurs only when a failure occurs in the current selection signal.

5 is a diagram illustrating a switching structure through a multi-channel wavelength division multiple link. One-way switching method is applied to each wavelength to generate two signals and then transfer them to optical switches through different multi-channel WDM links to select one optical signal of two optical signals. The optical channel transmitter 131 is configured by the optical splitter 2 by the number of wavelengths that can be multiplexed in the WDM transmission system, and the optical channel receiver 132 selects one optical signal of the two optical signals for the same number of wavelengths. And an optical switch 3. The optical channel transmitter 131 generates two optical signals for each of the N wavelengths, and the optical signals are separated for each wavelength, and the optical channel receiver is transmitted through the transmission multichannel optical path 511 and the transmission multichannel optical path 512. 132 is passed. The optical channel receiver 132 selects one of the signals transmitted through different lines with the same wavelength.

6 is a detailed block diagram of a unidirectional switching in a WDM system for a single station according to an embodiment of the present invention. As shown in FIG. 5, in order to switch over in the station A 1, the optical channel transmitter 131 generates two wavelengths identically to N wavelengths and transmits the two wavelengths to two optical multiples 122 to multiplex them into one optical path. And, it is transmitted to the relay station 4 through the optical power amplifier 111 for long-distance transmission, and is amplified by the optical path amplifier 411 of the relay station (4). These two optical signals are received by the optical preamplifier 121 at the station B (1), separated by the respective wavelengths in the multi-region multiple unit 121, and transmitted to the optical channel receiving unit 132, according to the state of the corresponding signal. Perform the transfer in (3).

While the invention has been described above based on the preferred embodiments thereof, these embodiments are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art that various changes, modifications, or adjustments to the above embodiments can be made without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited only by the appended claims, and should be construed as including all such changes, modifications or adjustments.

As described above, according to the present invention, it is possible to quickly recover even in the event of a failure in the multi-channel wavelength division multiple optical transmission system, thereby enabling continuous communication service, and developing an effective WDM optical transmission system having high reliability and stability. There is.

Claims (3)

In the unidirectional switching device of the optical channel section layer of the multi-channel wavelength division multiple optical transmission system, An optical splitter positioned in a transmission side optical channel section and receiving the multi-channel optical signal and splitting the same optical signal into two optical signals for each wavelength and transmitting them to a relay station; In the wavelength division multiplex optical transmission system comprising an optical switch unit located in the optical channel section of the receiving side and selecting the optical signal in the normal state of the same optical signal (A signal, B signal) for each wavelength transmitted from the relay station Unidirectional switching device for optical channel layer. The method of claim 1, wherein the optical switch unit, A first photodiode detecting a failure state of the A optical signal; A second photodiode detecting a failure state of the B optical signal; A selection controller for outputting an optical switch control signal for selecting one of the two optical signals in accordance with the failure states of the two optical signals; And an optical switch for selecting and outputting one optical signal among the two optical signals according to the optical switch control signal output from the selection controller. The method of claim 2, wherein the selection controller, A logic sum gate to which a fault state signal and a reset signal of the B signal are input; A selector for inputting a fault state signal of the A signal to an input terminal and an S terminal and a previous optical switch control signal to an input terminal to select and output one of two input terminals according to the signal level of the S terminal; And a D-flip-flop which is reset according to the output signal of the logic sum gate and outputs an output signal of the selector according to a clock input to the clock terminal. Device