JP4437104B2 - Asynchronous transparent transmission apparatus and method - Google Patents

Description

  The present invention is used for communication using a SONET / SDH (Synchronous Digital Hierarchy) frame. In particular, the present invention relates to a technique for transparently transmitting a signal asynchronous with the SONET / SDH network using the SONET / SDH network.

  FIG. 7 shows a network configured by an asynchronous transparent transmission device having a transparent transmission function. FIG. 7 shows a network configuration example in which a plurality of networks that are operated asynchronously with the SONET / SDH network A and are composed of client devices having different operators and control systems are connected. That is, a network including the client apparatus 11 or 12 corresponding to the part indicated by D in the lower part of FIG. 7, and the SONET / SDH network A and the asynchronous transparent transmission apparatuses B and C corresponding to the part indicated by E in the lower part of FIG. A transparent transmission network corresponding to a portion indicated by F in the lower part of FIG. In this transparent transmission network F, the networks D and E are asynchronous with each other.

  In FIG. 7, the client device 11 includes a transmission unit 111 and a reception unit 112, and is connected to the asynchronous transmission device B through an optical transmission path a and an optical transmission path h. The asynchronous transparent transmission apparatus B includes a transparent transmission package 13 and a SONET / SDH interface package 15. The transparent transmission package 13 includes a transmission unit 131 and a reception unit 132. The SONET / SDH interface package 15 includes a transmission unit 151. A receiving unit 152 is included.

  The asynchronous transmission transmission apparatus B is connected to the optical transmission path b, the optical transmission path c, the optical transmission path f, the optical transmission path g, and the SONET / SDH network A, and the asynchronous transmission transmission apparatus C is connected to the opposite side. ing. Asynchronous transparent transmission device C has SONET / SDH interface package 16 and transparent transmission package 14, as in asynchronous transparent transmission device B. SONET / SDH interface package 16 includes transmission unit 161 and reception unit 162. The transparent transmission package 14 includes a transmission unit 141 and a reception unit 142.

  The asynchronous transmission transmission device C is connected to the client device 12 through an optical transmission line d and an optical transmission channel e, and the client device 12 includes a transmission unit 121 and a reception unit 122, similarly to the client device 11.

  Client signals from the client device 11 and the client device 12 are transparently transmitted in a section including the asynchronous transparent transmission device B, the SONET / SDH network A, and the asynchronous transparent transmission device C.

  A configuration example of a transmission unit as a conventional asynchronous transmission device will be described with reference to FIG. In addition, about the receiving part, the structure in this invention shown in FIG. 2 and the structure in a prior art are the same.

In FIG. 8, the receiving unit 152 of the SONET / SDH interface package 15 converts the received STM (Synchronous Transport Module) optical signal into an optical-electric conversion process, an SOH (Section Overhead) termination process, a virtual concatenation (Virtual
Concatination) path demapping processing is performed, and the virtual concatenation path is passed to the STM path termination unit 1311.

  The STM path termination unit 1311 performs the termination process of the STM path and the phase synchronization process of the virtual concatenation path that has been transmitted through the different paths, whereby the packet signal generated by dividing the client signal is mapped. The phase of each of the paths that are being made is aligned.

  A GFP (Generic Framing Procedure) decapsuling unit 1312 performs GFP decapsulation of the main signal and passes it to the reception clock information extracting unit 1313 at the subsequent stage. The reception clock information extraction unit 1313 extracts the carrier clock information inserted in the GFP frame, and passes the extracted clock information to the clock reproduction unit 1314. The decapsulated packet signal is transmitted to the subsequent transmission signal reproduction unit 1317. To pass. The transmitted signal reproduction unit 1317 reproduces the original client signal from the passed packet signal.

  The clock recovery unit 1314 recovers the carrier clock of the original client signal from the passed clock information, and inputs the recovered clock to the transmission interface unit 1318.

  The clock recovery monitoring unit 1315 monitors whether the clock recovery unit 1314 has normally recovered the original carrier clock, and outputs a control signal to the shutdown control unit 1316 based on the monitoring result. For example, the following binary control signal is input to the shutdown control unit 1316.

When the clock recovery unit 1314 is normally regenerating the clock: 0 is input. Shutdown control to the transmission interface unit 1318 is disabled. When the clock recovery unit 1314 is not normally recovering the clock, 1 is input. Transmission interface unit 1318 The shutdown control unit 1316 performs shutdown control on the transmission interface unit 1318 in accordance with the binary control signal received from the clock regeneration monitoring unit 1315.

  The transmission interface unit 1318 performs electro-optical conversion of the main signal passed from the transmission signal regeneration unit 1317 when the shutdown control is invalid according to the control signal from the shutdown control unit 1316, and is input from the clock regeneration unit 1314. The optical signal is sent to the optical transmission line h using the existing clock as the carrier clock. Conversely, when the shutdown control is valid, the transmitted optical signal is shut down.

  In this way, a network configuration in which a network composed of asynchronous transparent transmission devices using a SONET / SDH network is connected to a network composed of client devices operating asynchronously with this network and having different operators and control systems. In this case, a signal can be transmitted transparently between client apparatuses.

  In addition, when the optical input is in the LOS (Loss of Signal) state at the receiving unit 132, ALS control is performed on the transmitted optical signal according to the ALS control signal from the ALS (Automatic Laser Shutdown) control unit 1319 (for example, Patent Document 1). reference). The transmission unit 141 of the transmissive transmission package 14 has a similar configuration.

  Next, FIG. 9 and FIG. 9 show a case where a client device with the ALS function enabled is connected to a SONET / SDH network using a conventional asynchronous transparent transmission device having a transmission unit as described above to operate the transparent transmission network. 10 and will be described with reference to FIG.

  Referring to FIG. 9, the client device 11 and the client device 12 each have an ALS function, and a case where a failure occurs in the optical transmission line h in the transparent transmission network having such a network configuration is considered. (FIG. 11: State A).

  In the receiving unit 112, since there is no optical signal input from the transmitting unit 131, the LOS state is entered (FIG. 11: state Aa), and the ALS function of the client device 11 controls the transmitting unit 111 (FIG. 11: state). A-b). Therefore, the receiving unit 132 detects LOS (FIG. 11: state Ac), and the transmission unit 131 is ALS controlled by the ALS function of the transparent transmission package 13 (FIG. 11: state Ad).

  On the other hand, the receiving unit 132 receives an ALS-controlled client signal and generates clock information from the signal. In this case, since the received signal is an ALS-controlled signal, the generated clock information is clock information that can be generated within the light emission time (M (sec)) by ALS. The main signal into which the generated clock information is inserted is sent to the SONET / SDH network A via the SONET / SDH interface package 15 (FIG. 11: state A-e).

  The main signal transmitted through the SONET / SDH network A reaches the transmission unit 141 of the transparent transmission package 14, and the transmission unit 141 attempts to regenerate the clock based on the transferred clock information.

However, the clock recovery unit 1314 shown in FIG. 8 requires a clock recovery time of several seconds in order to recover the clock from the transferred clock information. When this time is N (sec), the client device 11 and the light emission time M (sec) of the main signal subjected to ALS control at 11,
N> M
When there is a relationship, the time during which the clock information is received is less than the time required for clock recovery, and the clock cannot be normally recovered. In this case, the transmission unit 141 stops (shuts down) light transmission (FIG. 11: state A-f).

  The receiving unit 122 enters the LOS state when the transmitting unit 141 shuts down the optical transmission (FIG. 11: state Ag). Therefore, the transmission unit 121 is ALS-controlled by the ALS function of the client device 12 (FIG. 11: state A-h).

  The receiving unit 142 receives the ALS-controlled client signal, and generates and generates clock information that can be generated within the light emission time (M (sec)) by ALS, as in (FIG. 11: state A-e). The main signal in which the clock information is inserted is transmitted to the SONET / SDH network A via the SONET / SDH interface package 16 (FIG. 11: state A-i).

  The transmitter 131 stops (shuts down) light transmission (FIG. 11: state A-j) for the same reason as in FIG. 11: state A-f.

  With the above operation, when a failure occurs in the optical transmission line h, the transparent transmission network is in the state of FIG. 11: Aa to A-j and the network operation is stopped (FIG. 11: state B).

  Next, consider that the failure of the optical transmission line h has been recovered from this state. However, even if the failure of the optical transmission path h is recovered, the transmission unit 131 of the transparent transmission package 13 remains in the shutdown state. Therefore, the ALS control of the client device 11 is not released even after the recovery of the failure of the optical transmission path h. .

  Accordingly, the shutdown control of the transmission unit 141 of the transparent transmission package 14 is not released, and the ALS control of the client device 12 is not released as with the client device 11. Therefore, in this case, if the ALS function of the client device is not invalidated, the network will be in a so-called deadlock state that is hardened in (FIG. 11: state B). This state is shown in FIG.

In order to operate a transparent transmission network using such a conventional apparatus, the ALS function of the client apparatus must be invalidated in order to avoid a deadlock state that may occur when a network failure occurs.
JP 2000-69115 A

  In the conventional asynchronous transmission device, the clock information of the network D is generated at the reception point from the network D to the E shown in FIG. Based on the transferred clock information, the clock of the network D is reproduced to transmit data.

  Therefore, when the clock information at the transmission point from the networks E to D is lost due to a network failure, the optical output is stopped (shut down).

  However, if a network failure occurs when a device that enables the ALS function is connected as a client device of the network D, and the optical output is stopped by the transmission function of the asynchronous transmission device, the client of the network D Since the ALS function works, the device stops in a state where no light output is performed unless there is light input.

  On the other hand, in the clock regeneration in the transparent transmission function, even if the failure is recovered, a clock with high accuracy cannot be reproduced from a signal having a short light emission time by the ALS function. As a result of performing the control to maintain the light, the light is not transmitted, so that the entire network is in a so-called deadlock state.

  In order to avoid this, it is necessary to invalidate the ALS function of the device of the network D. However, the network D has a problem that management is difficult because an operator and a control system are different.

Here, the transparent transmission function is
1. 1. A function for performing transparent transmission of the entire SONET / SDH frame including the SOH of the received client signal without terminating / generating the SOH in the asynchronous transparent transmission apparatus. At the function of transferring the carrier clock information of the signal received from the client device and the output point to the opposite client device across the network, the clock is regenerated based on the transferred clock information, and the signal is regenerated with the regenerated clock. Means both functions.

  The ALS function is a function that determines that the operation is stopped when there is no optical input, and stops (shuts down) the optical output of the optical transmitter. When the maintenance person performs network repair or maintenance work, This is intended to prevent the influence (blindness, etc.) of the laser beam from the optical transmitter on the human body, and is a function generally provided in the optical transmission apparatus.

  The present invention has been made under such a background, and eliminates the necessity of disabling the ALS function of the client device and enables asynchronous network operation with the ALS function enabled. It is an object of the present invention to provide a transmission apparatus and method.

  In the present invention, even when a network failure occurs in the network D and / or the network E and the clock of the network D cannot be normally reproduced at the transmission point from the network E to the network D, transmission is performed in the conventional manner. The optical signal is not stopped (shut down), and an AIS signal using the internal clock as a carrier clock is transmitted.

  That is, according to a first aspect of the present invention, a reception clock information extraction unit that extracts reception clock information from a received frame, a clock recovery unit that performs clock recovery based on the reception clock information extracted by the reception clock information extraction unit, A clock recovery monitoring means for monitoring the normality of the clock recovered by the clock recovery means, and the frame is transmitted in synchronization with the destination clock using the recovered clock whose normality is recognized by the clock recovery monitoring means. And an asynchronous transmission device including transmission signal reproducing means.

  Here, a feature of the present invention is that, when the clock recovery monitoring unit determines that the recovered clock is abnormal, a clock selection unit that transmits the frame using its own clock instead of the clock is provided. It is in place.

  Furthermore, when the clock selection means transmits a frame using its own device clock, it can include an AIS signal insertion means for inserting an AIS signal into the frame.

  Thereby, the receiving side of the frame can recognize from the AIS signal that the clock used for sending the frame is not a formal clock but a substitute pseudo clock, and can take appropriate measures.

  The signal to be transmitted transparently by the asynchronous transparent transmission apparatus of the present invention is, for example, a SONET / SDH frame.

  The second aspect of the present invention extracts reception clock information from a received frame, reproduces a clock based on the extracted reception clock information, monitors the normality of the recovered clock, and recognizes normality. This is an asynchronous transparent transmission method applied to an asynchronous transparent transmission device that transmits the frame in synchronization with a destination clock using the recovered clock.

  Here, a feature of the present invention is that when it is determined that the reproduced clock is abnormal, the frame is transmitted using the own device clock instead of the clock.

  Further, when sending a frame using its own device clock, an AIS signal can be inserted into the frame.

  The signal to be transparently transmitted by the asynchronous transparent transmission method of the present invention is, for example, a SONET / SDH frame.

  According to the present invention, in a transparent transmission network configured by connecting a client device having an ALS function to an asynchronous transparent transmission device, a failure occurs in a transmission path between the client device and the ALS function of the client device is activated. Then, in consideration of the situation where the clock cannot be normally reproduced from the clock information generated within the light emission time by ALS at the signal transmission point to the client device, the function of transmitting the AIS signal using the internal clock as the carrier clock is provided. By providing on the transmission side of the asynchronous transparent transmission apparatus, it becomes possible to operate the network in which the ALS function of the client apparatus is valid.

  In addition, the optical transmission path h, the optical transmission path b, the optical transmission path c, the optical transmission path d, the optical transmission path e, and the optical transmission path, not the optical transmission path h shown in FIG. The same effect can be expected when a failure occurs in any of f, optical transmission line g, and SONET / SDH network A.

  The configuration of the asynchronous transmission apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of the asynchronous transmission apparatus according to this embodiment.

  In this embodiment, as shown in FIG. 1, a reception clock information extraction unit 2313 that extracts reception clock information from a received frame, and a clock recovery that regenerates a clock based on the reception clock information extracted by the reception clock information extraction unit 2313. Unit 2314, a clock recovery monitoring unit 2315 that monitors the normality of the clock recovered by the clock recovery unit 2314, and the destination of the frame using the recovered clock whose normality is recognized by the clock recovery monitoring unit 2315 This is a transmission unit 131 that constitutes an asynchronous transmission device including a transmission signal reproduction unit 2317 and a transmission interface unit 2319 that are transmitted in synchronization with each other clock.

  Here, the feature of the present embodiment is that when the clock recovery monitoring unit 2315 determines that the recovered clock is abnormal, the own device clock generated by the in-device clock generation unit 2320 is used instead of the clock. And a clock selector 2321 for sending out the frame.

  Further, when the clock selection unit 2321 performs frame transmission using its own device clock, the clock selection unit 2321 includes an AIS signal insertion unit 2318 that inserts an MS-AIS (Multiplex Section AIS) signal into the frame.

  Further, in this embodiment, the received clock information is extracted from the received frame, the clock is recovered based on the extracted received clock information, the normality of the recovered clock is monitored, and the recovered clock whose normality is recognized. Asynchronous transparent transmission method applied to an asynchronous transparent transmission device that transmits the frame in synchronization with a destination clock using the.

  Here, the feature of the present embodiment is that when it is determined that the recovered clock is abnormal, the frame is transmitted using its own clock instead of the clock.

  Furthermore, when sending a frame using its own device clock, an MS-AIS signal is inserted into the frame.

  Hereinafter, this embodiment will be described in more detail.

  Referring to FIG. 7, as one embodiment of the present invention, a network (network E) configured by an asynchronous transparent transmission apparatus using a SONET / SDH network operates asynchronously with this network, and an operator or a control system. A configuration example of a network (transparent transmission network F) to which a SONET / SDH network (network D) composed of different client devices is connected is shown.

  In FIG. 7, the client device 11 includes a transmission unit 111 and a reception unit 112, and is connected to the asynchronous transmission device B through an optical transmission path a and an optical transmission path h. The asynchronous transparent transmission apparatus B includes a transparent transmission package 13 and a SONET / SDH interface package 15. The transparent transmission package 13 includes a transmission unit 131 and a reception unit 132. The SONET / SDH interface package 15 includes a transmission unit 151. A receiving unit 152 is included.

  The asynchronous transmission transmission apparatus B is connected to the optical transmission path b, the optical transmission path c, the optical transmission path f, the optical transmission path g, and the SONET / SDH network A, and the asynchronous transmission transmission apparatus C is connected to the opposite side. ing. Asynchronous transparent transmission device C has SONET / SDH interface package 16 and transparent transmission package 14, as in asynchronous transparent transmission device B. SONET / SDH interface package 16 includes transmission unit 161 and reception unit 162. The transparent transmission package 14 includes a transmission unit 141 and a reception unit 142.

  The asynchronous transmission transmission device C is connected to the client device 12 through an optical transmission line d and an optical transmission channel e, and the client device 12 includes a transmission unit 121 and a reception unit 122, similarly to the client device 11.

  Client signals from the client device 11 and the client device 12 are transparently transmitted in a section including the asynchronous transparent transmission device B, the SONET / SDH network A, and the asynchronous transparent transmission device C.

  Referring to FIG. 2, a detailed configuration of the receiving unit 132 of the transparent transmission package 13 illustrated in FIG. 7 is illustrated. The reception interface unit 1321 receives a client optical signal, which is a SONET / SDH frame asynchronous with the SONET / SDH network A, from the client device 11, and photoelectrically converts the received optical signal to generate reception clock information in the subsequent stage. To part 1322. The reception clock information generation unit 1322 generates information related to the carrier clock of the client signal from the main signal passed from the reception interface unit 1321, and the main signal is sent to the packet signal generation unit 1323 in the subsequent stage. Passed to the GFP encapsulation unit 1324.

  The packet signal generation unit 1323 packetizes the passed main signal and passes it to the GFP encapsulation unit 1324. The GFP encapsulation unit 1324 encapsulates the packetized signal and the clock information passed from the reception clock information generation unit 1322 and passes them to the subsequent STM path generation unit 1325. The STM path generation unit 1325 generates a virtual concatenation path after mapping the signal passed from the GFP encapsulation unit 1324 to the STM path, and passes it to the transmission unit 151 of the SONET / SDH interface package 15. The transmission unit 151 of the SONET / SDH interface unit 15 transmits an optical signal to the SONET / SDH network A connected to the optical transmission line b. The receiving unit 142 of the transparent transmission package 14 shown in FIG. 7 has the same configuration.

  Referring to FIG. 1, a detailed configuration of the transmission unit 131 of the transparent transmission package 13 illustrated in FIG. 7 is illustrated. The STM path termination unit 2311 receives the main signal from the reception unit 152 of the SONET / SDH interface package 15, performs phase synchronization of the virtual concatenation path after terminating the passed main signal in the STM path, and transmits the main signal to the subsequent stage. The data is transferred to the GFP decapsulating unit 2312. The GFP decapsulation unit 2312 performs a GFP decapsulation process on the main signal that has been passed. Then, the decapsulated main signal is passed to the reception clock information extraction unit 2313 at the subsequent stage.

  The reception clock information extraction unit 2313 extracts clock information from the passed signal, passes the extracted clock information to the clock reproduction unit 2314, and passes the main signal to the transmission signal reproduction unit 2317. The transmitted signal reproduction unit 2317 reproduces the original client signal from the packetized signal.

  The clock recovery unit 2314 recovers the carrier clock of the client signal based on the clock information passed from the reception clock information extraction unit 2313 and passes the recovered clock to the clock selection unit 2321. The clock recovery monitoring unit 2315 monitors whether the clock recovery unit 2314 has normally recovered the original carrier clock, and outputs a control signal to the AIS / clock selection control unit 2316 based on the monitoring result.

  The AIS / clock selection control unit 2316 controls the AIS signal insertion unit 2318 and the clock selection unit 2321 in accordance with the control signal received from the clock reproduction monitoring unit 2315. The in-device clock generation unit 2320 generates an in-device clock and passes the generated clock to the clock selection unit 2321. The clock selection unit 2321 selects one of the in-device clock and the reproduction clock input to itself in accordance with the control signal input from the AIS / clock selection control unit 2316, and transmits the selected clock to the transmission interface unit. 2319.

  The AIS signal insertion unit 2318 inserts the MS-AIS signal according to the control signal from the AIS / clock selection control unit 2316 and passes the main signal to the transmission interface unit 2319. The transmission interface unit 2319 performs electro-optical conversion on the main signal passed from the AIS signal insertion unit 2318, and sends the original client optical signal to the optical transmission line h using the clock input from the clock selection unit 2321. . When the ALS control signal from the ALS control unit 2322 is input, the transmission optical signal is ALS-controlled. Note that the transmission unit 141 of the transparent transmission package 14 shown in FIG. 7 has the same configuration.

  Although the configuration of the embodiment has been described in detail above, the transmission unit 151 in the SONET / SDH interface package 15 in FIG. 2 maps the STM path to the SONET / SDH frame, performs electro-optical conversion, and then transmits it to the network as an STM optical signal. The receiver 152 in the SONET / SDH interface package 15 in FIG. 3 has a function of demapping the STM path from the SONET / SDH frame after optical-electrical conversion of the received STM optical signal. Since these are well known to those skilled in the art and are not directly related to the present invention, their detailed configurations are omitted.

(Description of operation of the embodiment)
The operation of the receiving unit 132 of the transparent transmission package 13 shown in FIG. 7 will be described with reference to FIG. The reception interface unit 1321 of the reception unit 132 performs optical-electrical conversion on the client optical signal, which is a SONET / SDH frame asynchronous with the SONET / SDH network A, received from the optical transmission path a, and generates a main signal as reception clock information. To part 1322. The reception clock information generation unit 1322 generates clock information necessary for reproducing the carrier clock of the signal transmitted by the transparent transmission package 14 of FIG. For generating clock information, SRTS (Synchronous Residual) used in an ATM (Asynchronous Transfer Mode) transmission system is used.
Time Stamp) method is applied.

  In the SRTS method, information on the carrier clock is generated by observing the number of carrier clocks of the client signal within a certain time by using a reference clock generated in the apparatus. Here, RTS (Residual Time) is used. Only Stamp) is transferred as clock reproduction information. The generated clock information is passed to the GFP encapsulation unit 1324, and the client signal is passed to the subsequent packet signal generation unit 1323.

  The packet signal generation unit 1323 transparently transmits the entire signal including the SOH of the client signal, so that the client signal is packetized from the top, and the packetized signal is transmitted together with the clock information at the GFP encapsulation unit 1324. It is encapsulated in a GFP frame and passed to the STM path generation unit 1325. For GFP treatment, ITU-T G.I. Follow the method recommended in 7041 or ANSI T1X1.5.

  The STM path generation unit 1325 maps the GFP capsule signal to the STM path and generates a virtual concatenation path. For example, when the client signal is a signal in accordance with the STM-16 frame format, 17 virtual concatenation paths are generated in the VC4 path in order to transmit the entire signal including the SOH.

  For virtual concatenation path generation, see ITU-T G.C. Follow the method recommended in 707. The transmission unit 151 of the SONET / SDH interface package 15 performs SOH generation processing, mapping of virtual concatenation paths to SONET / SDH frames, and electro-optical conversion processing, and then transmits the STM optical signal to the optical transmission line b. Sent out.

  The processing in the transmission unit 151 is well known to those skilled in the art and is not directly related to the present invention, and thus detailed processing is omitted. The receiving unit 142 of the transparent transmission package 14 shown in FIG.

  Next, the operation of the transmission unit 131 of the transparent transmission package 13 in FIG. 7 will be described with reference to FIG. The receiving unit 152 of the SONET / SDH interface package 15 performs optical-electrical conversion processing, SOH termination processing, and virtual concatenation path demapping processing on the received STM optical signal, and the virtual concatenation path is sent to the STM path termination unit 2311. Passed.

  The processing in the receiving unit 152 is well known to those skilled in the art and is not directly related to the present invention, and thus detailed processing is omitted.

  In the STM path termination unit 2311, the termination process of the STM path and the phase synchronization process of the virtual concatenation path that has been transmitted through different paths are performed, and the packet signal generated by dividing the client signal is thereby mapped. The phase of each path is aligned. For the phase synchronization processing of the virtual concatenation path, see ITU-T G.C. Follow the method recommended in 783.

  The GFP decapsulating unit 2312 decapsulates the main signal and passes it to the reception clock information extracting unit 2313 at the subsequent stage. The reception clock information extraction unit 2313 extracts the carrier clock information inserted in the GFP frame by the reception unit 142 of the transparent transmission package 14, passes the extracted clock information to the clock recovery unit 2314, and decapsulates the packet. The signal is passed to the subsequent transmission signal reproduction unit 2317. The transmitted signal reproduction unit 2317 reproduces the original client signal received by the receiving unit 142 of the transparent transmission package 14 from the passed packet signal. The clock recovery unit 2314 recovers the original client signal carrier clock from the received clock information, and passes the recovered clock to the subsequent clock selection unit 2321. The recovered clock is equivalent to the carrier clock of the client optical signal transmitted from the client device 12.

  Here, the clock recovery unit 2314 needs a clock recovery time of several seconds in order to recover the clock from the passed clock information. For example, when the clock information transferred within this recovery time is lost, It becomes impossible to reproduce the clock normally.

  The clock regeneration monitoring unit 2315 monitors whether the clock regeneration unit 2314 is normally regenerating the clock, and inputs the monitoring result to the AIS / clock selection control unit 2316 as a control signal. For example, the following binary control signal is input to the AIS / clock selection control unit 2316.

When the clock recovery unit 2314 is reproducing the clock normally: 0 is input When the clock recovery unit 2314 is not normally recovering the clock: 1 is input The in-device clock generation unit 2320 generates the in-device clock Then, the generated in-device clock is transferred to the clock selection unit 2321 at the subsequent stage.

  The AIS / clock selection control unit 2316 inputs control signals to the AIS signal insertion unit 2318 and the clock selection unit 2321 in accordance with the control signal input from the preceding clock recovery monitoring unit 2315. For example, if 0 is input from the clock regeneration monitoring unit 2315, it means that the clock regeneration unit 2314 is normally regenerating the clock, and therefore the AIS / clock selection control unit 2316 may The insertion unit 2318 is controlled not to insert the MS-AIS signal, and the clock selection unit 2321 is controlled to select the clock reproduced by the clock reproduction unit 2314.

Conversely, when 1 is input from the clock regeneration monitoring unit 2315, the clock regeneration unit 2314 does not normally regenerate the clock, that is, the client device 12 serves as a carrier clock for the client signal to be transmitted. In this case, the AIS / clock selection control unit 2316 inserts the MS-AIS signal into the AIS signal insertion unit 2318 because it means that the client optical signal cannot be transmitted with the carrier clock and the equivalent clock. In addition, the clock selection unit 2321 is controlled to select the in-device clock. For example, the following binary control signals are input as these control signals.
When 0 is input from the clock recovery monitoring unit 2315 No MS-AIS signal insertion: 0 is input Playback clock selection: When 0 is input from the input clock recovery monitoring unit 2315 With MS-AIS signal insertion: 1 is input Internal clock selection: 1 input

  The clock selection unit 2321 selects one of the input reproduction clock and in-device clock in accordance with the control signal from the AIS / clock selection control unit 2316 and passes the selected clock to the transmission interface unit 2319. The AIS signal insertion unit 2318 processes the main signal passed from the previous transmission signal reproduction unit 2317 in accordance with the control signal from the AIS / clock selection control unit 2316 and passes the main signal to the subsequent transmission interface unit 2319.

  In the main signal processing here, for example, when 0 is input as the control signal, the main signal passed from the previous transmission signal reproduction unit 2317 is transmitted as it is, but 1 is input as the control signal. If it is, the main signal passed from the previous transmission signal reproduction unit 2317 is used as the MS-AIS signal.

  The transmission interface unit 2319 performs electro-optical conversion on the main signal passed from the AIS signal insertion unit 2318 in the previous stage, and uses the clock passed from the clock selection unit 2321 as a carrier clock to the original optical transmission line h. Send client optical signal. The ALS control unit 2322 performs ALS control on the transmission interface unit 2319 when there is no input to the reception unit 132 and the LOS state is present. Regarding ALS control, ITU-T G.C. Follow the method recommended in 958. The transmission unit 141 of the transparent transmission package 14 shown in FIG.

  Next, the network operation in the present invention in the entire transparent transmission network constituted by the asynchronous transparent transmission apparatus having the components described above will be described with reference to FIGS. 3, 4, 5, and 6. FIG. Referring to FIG. 3, there is shown a network configuration example as an embodiment of the present invention, which has the same configuration as the network configuration example shown in FIG. Assume that the client device 11 and the client device 12 each have an ALS function.

  Consider the case where a failure occurs in the optical transmission line h in the network configuration shown in FIG. 3 (FIG. 5: state A). In the receiving unit 112, there is no optical signal input from the transmitting unit 131 due to a failure in the transmission path h, and LOS occurs (FIG. 5: state Aa), so that the ALS function of the client device 11 works and the transmitting unit 111. Is ALS-controlled (FIG. 5: state Ab). Therefore, the reception unit 132 detects LOS (FIG. 5: state Ac), and the transmission unit 131 is ALS controlled by the ALS function of the transparent transmission package 13 (FIG. 5: state Ad).

  On the other hand, the receiving unit 132 receives an ALS-controlled client signal and generates clock information from the signal. In this case, since the received signal is an ALS-controlled signal, the generated clock information is clock information that can be generated within the light emission time (M (sec)) by ALS. The main signal into which the generated clock information is inserted is sent to the SONET / SDH network A via the SONET / SDH interface package 15 (FIG. 5: state A-e).

  The main signal transmitted through the SONET / SDH network A reaches the transmission unit 141 of the transparent transmission package 14, and the transmission unit 141 attempts to regenerate the clock based on the transferred clock information.

However, the clock recovery unit 2314 shown in FIG. 1 requires a clock recovery time of several seconds in order to recover the clock from the transferred clock information. When this time is N (sec), the client device 11 and the light emission time M (sec) of the main signal subjected to ALS control at 11,
N> M
When there is a relationship, the time during which the clock information is received is less than the time required for clock recovery, and the clock cannot be normally recovered. In this case, the transmission unit 141 transmits an MS-AIS signal using the internal clock as a carrier clock (FIG. 5: state A-f). The receiving unit 122 of the client device 12 receives the MS-AIS signal from the transmitting unit 141 (FIG. 5: state Ag).

  On the other hand, since the transmission unit 121 transmits a client signal as usual (FIG. 5: state A-h), the reception unit 142 generates and transfers clock information from the received client signal (FIG. 5: state A). -I).

  With the above operation, when a failure occurs in the optical transmission line h, the transparent transmission network is in a state (FIG. 5: Aa to Ai) and moves from the client device 12 to the transparent transmission package 13. In signal transmission, a normal operation state is maintained (FIG. 5: state B).

  Next, it is considered that the failure of the optical transmission line h has been recovered from this state (FIG. 6: state C). When the failure of the optical transmission line h is recovered, the LOS state of the receiving unit 112 is canceled (FIG. 6: state C-a). Therefore, the ALS control of the transmission unit 111 is also autonomously released, and the transmission unit 111 resumes optical transmission (FIG. 6: state Cb). Therefore, the LOS state detected by the receiving unit 132 is also released (FIG. 6: state Cc), and similarly, the ALS control of the transmitting unit 131 is also autonomously released, so that the transmitting unit 131 resumes optical transmission. (FIG. 6: state Cd).

  On the other hand, the receiving unit 132 generates and transfers clock information from the received signal (FIG. 6: state Ce), but as described above, since the ALS control of the transmitting unit 111 has already been released, The generated clock information can be generated in a time longer than the time N (sec) necessary for clock reproduction in the transmission unit 141. Therefore, the transmission unit 141 can reproduce the carrier clock of the client signal, so that the client signal is transmitted using the reproduced clock as the carrier clock (FIG. 6: state Cf), and the reception unit 122 transmits the transmitted signal. (FIG. 6: state C-g).

  With the above operation, the network in the direction from the client device 11 to the client device 12 is autonomously restored.

  On the other hand, as described in FIG. 5, the normal network operation state is maintained from the client device 12 to the transparent transmission package 13 regardless of the presence or absence of a failure in the transmission path h (FIG. 6: state Ch-, FIG. 6: State Ci).

  Therefore, as described above, the entire network is autonomously restored to the normal state before the failure by the failure recovery of the transmission path h, and the operation is resumed (FIG. 6: state D). This state is shown in FIG.

(Other embodiments of the invention)
By replacing the AIS signal insertion unit 2318 of FIG. 1 with a function of inserting a random pattern signal or a 0/1 alternating signal, the previous section where the carrier clock cannot be normally regenerated at the signal transmission point to the client device. In a similar situation, instead of sending the MS-AIS signal using the internal clock as the carrier clock, a random pattern signal using the internal clock as the carrier clock or a 0/1 alternating signal is sent out. In this case, by detecting LOF (Loss of Frame) in the client device, it is possible to detect a failure in the transmission path state without operating the ALS function of the client device, and the same effect can be expected.

  According to the present invention, even when the ALS function of the client device is activated, the deadlock state as described above can be avoided. Therefore, the SONET / SONET having the asynchronous transparent transmission function to which the client device having the ALS function is connected. The operational efficiency of the SDH network can be improved.

The block diagram of the transmission part of a present Example. The block diagram of the receiving part of a present Example. The figure which shows the state which the failure generate | occur | produced in the network of a present Example. The figure which shows the state which the failure of the network of a present Example restored. The flowchart which shows the failure handling procedure of a present Example. The flowchart which shows the failure recovery procedure of a present Example. The network configuration diagram of the present embodiment or the conventional. The block diagram of the transmission part of a prior art example. The figure which shows the state which the failure generate | occur | produced in the conventional network. The figure which shows the state which the deadlock generate | occur | produced in the conventional network. The flowchart which shows the conventional trouble handling procedure.

Explanation of symbols

11, 12 Client device 13, 14 Transparent transmission package 15, 16 SONET / SDH interface package 111, 121, 131, 141, 151, 161 Transmission unit 112, 122, 132, 142, 152, 162 Reception unit 1311, 2311 STM path Terminating units 1312, 2312 GFP decapsulating units 1313, 2313 Receive clock information extracting units 1314, 2314 Clock recovery units 1315, 2315 Clock recovery monitoring unit 1316 Shutdown control units 1317, 2317 Transparent signal recovery units 1318, 2319 Transmission interface units 1319, 2322 ALS control unit 1321 reception interface unit 1322 reception clock information generation unit 1323 packet signal generation unit 1324 GFP encapsulation unit 1325 STM path generation Unit 2316 AIS / clock selection control unit 2318 AIS signal insertion unit 2320 In-device clock generation unit 2321 Clock selection unit A SONET / SDH network B, C Asynchronous transparent transmission device D, E SONET / SDH network F Transparent transmission networks a to h Light Transmission line

Claims (6)

Reception clock information extraction means for extracting reception clock information from the received frame;
Clock recovery means for recovering a clock based on the received clock information extracted by the received clock information extracting means;
Clock recovery monitoring means for monitoring the normality of the clock recovered by the clock recovery means;
In an asynchronous transmission device comprising: transmission signal reproduction means for transmitting the frame in synchronization with a destination clock using a reproduction clock whose normality is recognized by the clock reproduction monitoring means;
An asynchronous transparent transmission device comprising: clock selection means for sending out the frame using its own clock instead of the clock when the clock recovery monitoring means determines that the recovered clock is abnormal.   2. The asynchronous transmission apparatus according to claim 1, further comprising AIS signal insertion means for inserting an AIS (Alarm Indicator Signal) signal into the frame when the clock selection means transmits a frame using its own device clock.   The asynchronous transparent transmission apparatus according to claim 1 or 2, wherein a signal to be transparently transmitted is a SONET / SDH frame. The reception clock information is extracted from the received frame, the clock is recovered based on the extracted reception clock information, the normality of the recovered clock is monitored, and the frame is extracted using the recovered clock with normality. In an asynchronous transparent transmission method applied to an asynchronous transparent transmission device that transmits in synchronization with a destination clock,
An asynchronous transparent transmission method characterized in that, when it is determined that the reproduced clock is abnormal, the frame is transmitted using its own clock instead of the clock.   5. The asynchronous transparent transmission method according to claim 4, wherein when transmitting a frame using its own device clock, an AIS signal is inserted into the frame.   6. The asynchronous transparent transmission method according to claim 4, wherein a signal to be transparently transmitted is a SONET / SDH frame.

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