JP2010206625A - Optical transmission apparatus and optical transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission apparatus capable of performing transparent transmission for client signals of OC3/STM-1 and OC12/STM-4 with low transmission bit rate. <P>SOLUTION: The optical transmission apparatus 100 includes: a clock data playback unit 20 for extracting data and a clock from a client signal; a first framer unit 31 for establishing frame synchronism of data; a mapper unit 32 for mapping the frame of data to a frame configuration of OC48/STM-16 or OC192/STM-64; a stuff mapping unit 51 for accommodating the mapped frame in an OPU1 payload or OPU2 payload to configure an ODU1 frame or ODU2 frame; and an OTUk mapping/demapping unit 60 for accommodating the multiplexed ODU1 frame or ODU2 frame in an OPU2 payload or OPU3 payload to configure an OTU2 frame or OTU3 frame. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) signals and ITU-T (International Telecommunication Union Telecommunication Standardization Sector). TECHNICAL FIELD The present invention relates to an optical transmission apparatus and an optical transmission method for accommodating a SONET / SDH signal clock and data transparently in an OTUk (Optical Transport Unit: optical transmission unit, k = 2,3) signal standardized by G.709. .

  OTN (Optical Transport Network) is a technology that transfers SONET / SDH signals (hereinafter referred to as client signals) sent from SONET / SDH equipment and transmitted through SONET / SDH networks in the optical core network. is there. OTN is standardized by ITU-T based on a WDM (Wavelength Division Multiplex) transmission method. Further, the OTUk (k = 2, 3) signal transmitted through the WDM network is required to transmit the client signal transparently.

  In other words, when transmitting client signals in OTUk (k = 2,3) signals, overhead and clock transparent transmission is required in addition to the SONET / SDH main signal sent from the SONET / SDH equipment. Become.

  In particular, regarding the overhead, it is necessary to make the communication between the SONET / SDH devices connected transparently through the User's byte defined by SONET / SDH transparent. User's byte is K1 byte or K2 byte used for APS (Automatic Protection Switch) switching, SDCC (Section Data Communication Channel) used for data communication between offices / LDCC (Line Data Communication Channel) bytes.

  As for the clock, for example, as shown in FIG. 15, in a SONET / SDH network connected to a WDM network, in order for a plurality of users (stations) to synchronize with the network, the frequency deviation is set to the opposite SONET / It needs to be transmitted to the SDH device. In FIG. 15, as a station of user A that is connected to the WDM network and has a SONET / SDH synchronization system, station # 1 having a clock source and station # 2 not having a clock source Is illustrated. In addition, as a station of user B, which is connected to the WDM network and has a SONET / SDH synchronization system, # 1 station having no clock source and # 2 station having a clock source are illustrated.

  In contrast, conventional optical transmission equipment accommodates multiple client signals and multiplexes and demultiplexes them to the upper layer, with a SONET / SDH pointer function (H1 byte, H2 byte processing) at the receiver of each port. Use to transfer to the reference clock in the device. Then, the separated paths are multiplexed and separated. At this time, the SONET / SDH section overhead information is terminated by adopting an upper layer mapping method defined by SONET / SDH.

  For this reason, when transmitting overhead transparently, the overhead information is temporarily saved and stored, and reinserted into unused bytes of the overhead of the frame to the upper layer, and the B1 byte and B2 byte are recalculated. It is necessary to perform such processing. With regard to clock transparency, a conventional optical transmission device having a plurality of ports cannot perform a plurality of types of clock transmission, and therefore, it is necessary to perform clock transmission by using a separate line.

  Although not directly related to the present invention, the conventional multiplex relay transmission apparatus includes a two-channel GbE receiving circuit that receives a GbE signal and two independent channels connected to each other. It has a writeable and readable FIFO memory. Further, the conventional multiplexing relay transmission apparatus includes a multiplexing circuit that multiplexes the read two-channel signals, an OTU frame generation circuit that maps the multiplexed two-channel signals to the OTU payload of the OTU frame, and an OTU An optical transmission circuit that transmits a transmission signal having a frame structure is provided (see, for example, Patent Document 1).

  In addition, the conventional digital transmission system sets the bit rate of this client signal to a specific fixed frame for a client signal other than the client signal having the highest bit rate among a plurality of types of client signals having different bit rates. The dummy pattern is inserted into the fixed frame (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2002-247073 JP 2008-177773 A

  In conventional optical transmission equipment, when client signals input to multiple ports are accommodated, all data (overhead, payload) is transmitted transparently by switching to the reference clock in the equipment. To do. In order to transfer to this reference clock, it is necessary to extract the terminated section overhead and insert it again into unused bytes in the higher layer, which causes a problem that the circuit configuration becomes complicated.

  In addition, when a plurality of client signals are multiplexed and separated in an upper layer, client signals are mapped or demapped, so that the clock of each port is temporarily transferred to a reference clock in the apparatus. . For this reason, in the system configuration of the conventional optical transmission apparatus shown in FIG. 16, there is a problem that clock transparency cannot be realized independently for each port.

  On the other hand, as a technique for transparently transmitting a plurality of asynchronous client signals individually, as shown in FIG. 17, a method of performing stuffing or demapping on an OTN frame and mapping or demapping is based on ITU-T G.709. Standardized.

  In this ITU-T G.709, as shown in FIG. 17A, a client signal having a transmission bit rate of 2.48832 Gbps ± 20 ppm (example: OC (Optical Channel: optical channel) 48 / STM (Synchronous Transport Module: Synchronous transfer module) -16) is multiplexed four times. A method of mapping or demapping the four multiplexed client signals to the OTU2 frame having a transmission bit rate of 10.7092253164557 Gbps ± 20 ppm and mapping or demapping is standardized.

  In ITU-T G.709, as shown in FIG. 17B, 16 client signals (eg, OC48 / STM-16) having a transmission bit rate of 2.48832 Gbps ± 20 ppm are multiplexed. A method of mapping or demapping the 16 multiplexed client signals to the OTU3 frame having a transmission bit rate of 43.018413559322 Gbps ± 20 ppm and mapping or demapping is standardized.

  In ITU-T G.709, as shown in FIG. 17C, four client signals (eg, OC192 / STM-256) having a transmission bit rate of 9.95328 Gbps ± 20 ppm are multiplexed. A method of mapping or demapping the four multiplexed client signals to the OTU3 frame having a transmission bit rate of 43.018413559322 Gbps ± 20 ppm and mapping or demapping is standardized.

  However, client signals with a transmission bit rate of 622.08 Mbps ± 20 ppm (for example, OC12 / STM-4) and client signals with 155.52 Mbps ± 20 ppm (for example, OC3 / STM-1) are transferred to OTU2 and OTU3 OTN frames. Bandwidth is insufficient when mapping or demapping is performed in a multiplexed manner. In other words, in ITU-T G.709, when a client signal is accommodated in a payload, a stuff or destuff JC (Justification) with a frequency deviation of ± 20 ppm for one client signal with a transmission bit rate of 2.48832 Gbps. ) Bytes are specified. For this reason, when a client signal with a transmission bit rate of 622.08 Mbps is accommodated in the payload instead of a client signal with 2.48832 Gbps, four client signals can be accommodated. Is insufficient to absorb the frequency deviation. Similarly, client signals with a transmission bit rate of 155.52 Mbps ± 20 ppm lack the JC byte, cannot absorb the frequency deviation, and cannot satisfy the SONET / SDH frequency deviation standard of ± 20 ppm. Therefore, there is a problem that these low-speed (low layer) client signals (OC3 / STM-1 and OC12 / STM-4) cannot be transparently transmitted.

  In addition, in a configuration that uses OTN frame destuffing to regenerate the clock, if a failure occurs on the OTN network where the payload of the OPU (Optical Channel Payload Unit) is broken, There is a problem that the output clock cannot be reproduced and the SONET / SDH frequency deviation standard of ± 20 ppm cannot be satisfied.

  An optical transmission apparatus according to the present invention includes a clock data recovery unit that extracts data and a clock from a client signal, and a first framer unit that performs frame synchronization of the data based on the clock. The optical transmission apparatus further includes a mapper unit that maps the data frame to an OC48 / STM-16 or OC192 / STM-64 frame configuration in synchronization with the frame. In addition, the optical transmission apparatus includes a stuff mapping unit that accommodates the frame mapped by the mapper unit in an OPU1 payload or an OPU2 payload generated by a reference clock to configure an ODU1 frame or an ODU2 frame. Also, the optical transmission apparatus accommodates 4 or 16 ODU1 frames or 1 or 4 ODU2 frames in an OPU2 payload or OPU3 payload generated by a reference clock, and constitutes an OTU2 frame or an OTU3 frame. And a mapping unit.

  The disclosed optical transmission apparatus includes not only OC48 / STM-16 and OC192 / STM-64 client signals, but also OC3 / STM-1 and OC12 / STM-4 client signals with a low transmission bit rate (low layer). However, the present invention has an effect of enabling transparent transmission of data, overhead and clock.

FIG. 1 is a schematic diagram showing the relationship between a SONET / SDH network and a WDM network. It is a block diagram which shows schematic structure of the optical transmission apparatus which concerns on this embodiment. FIG. 3 is a block diagram illustrating an example of an internal configuration of a clock generation unit illustrated in FIG. 2. FIG. 3 is a block diagram illustrating an example of the optical transmission device illustrated in FIG. 2. (A) OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 to OTU2 mapping scheme diagram, (b) OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 It is explanatory drawing for demonstrating the asynchronous multiplexing system to OTU2. It is explanatory drawing for demonstrating the mapping of a frame structure of SONET / SDH, (a) is a frame structure figure for demonstrating the mapping of OPUK CBR2G5, (b) is OC3 frame structure figure, (c) is OC48 of FIG. It is a frame block diagram. (A) is a time chart showing an example of the input pulse waveform to the LPF, (b) is a time chart showing another example of the input pulse waveform to the LPF, and (c) is still another example of the input pulse waveform to the LPF. It is a time chart which shows an example. (A) OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 to OTU3 mapping scheme diagram, (b) OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 It is explanatory drawing for demonstrating the asynchronous multiplexing system to OTU3. (A) OC3 / STM-1, OC12 / STM-4, OC48 / STM-16 or OC192 / STM-64 to OTU2 mapping scheme diagram, (b) OC3 / STM-1, OC12 / STM-4 FIG. 4 is an explanatory diagram for explaining an asynchronous multiplexing scheme to OC48 / STM-16 or OC192 / STM-64 in OTU2. (A) OC3 / STM-1, OC12 / STM-4, OC48 / STM-16 or OC192 / STM-64 to OTU3 mapping scheme diagram, (b) OC3 / STM-1, OC12 / STM-4 FIG. 3 is an explanatory diagram for explaining an asynchronous multiplexing method to OC48 / STM-16 or OC192 / STM-64 in OTU3. FIG. 4 is a block diagram illustrating another example of the internal configuration of the clock generation unit illustrated in FIG. 2. FIG. 10 is a block diagram illustrating still another example of the internal configuration of the clock generation unit illustrated in FIG. 2. (A) is a block diagram which shows an example of the internal structure of the 1st framer part and mapper part which are shown in FIG. 2, (b) is a block diagram which shows an example of the internal structure of a demapper part and a 2nd framer part. (A) is explanatory drawing for demonstrating the reinsertion process of B1 byte and B2 byte in the mapper side, (b) is explanatory drawing for demonstrating the reinsertion process of B1 byte and B2 byte in the demapper side. It is the schematic which shows the relationship between a SONET / SDH network and a WDM network. It is a block diagram which shows schematic structure of the conventional optical transmission apparatus. It is explanatory drawing for demonstrating the asynchronous multiplexing system by ITU.T G709, (a) is explanatory drawing for demonstrating the asynchronous multiplexing system to OTU2 of OC48 / STM-16, (b) is OC48 / STM- 16 is an explanatory diagram for explaining an asynchronous multiplexing system to 16 OTU3, and (c) is an explanatory diagram for explaining an asynchronous multiplexing system to OC192 / STM-64 OTU3.

  Here, the present invention can be implemented in many different forms. Therefore, it should not be interpreted only by the description of the following embodiment. Also, the same reference numerals are given to the same elements throughout the embodiment.

  In the embodiment, the system will be mainly described. However, as will be apparent to those skilled in the art, the present invention can also be implemented as a program and method usable on a computer. In addition, the present invention can be implemented in hardware, software, or software and hardware embodiments. The program can be recorded on any computer-readable medium such as a hard disk, CD-ROM, DVD-ROM, optical storage device, or magnetic storage device. Furthermore, the program can be recorded on another computer via a network.

(First embodiment of the present invention)
FIG. 1 is a schematic diagram showing the relationship between a SONET / SDH network and a WDM network. 2 is a block diagram illustrating a schematic configuration of the optical transmission apparatus according to the present embodiment, FIG. 3 is a block diagram illustrating an example of an internal configuration of the clock generation unit illustrated in FIG. 2, and FIG. 4 is a block diagram illustrating the optical transmission apparatus illustrated in FIG. It is a block diagram which shows an example. FIG. 5 (a) is a mapping scheme diagram from OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 to OTU2, and FIG. 5 (b) is OC3 / STM-1, OC12 / STM-4 or OC48. It is explanatory drawing for demonstrating the asynchronous multiplexing system to OTU2 of / STM-16. 6A is a frame configuration diagram for explaining mapping of OPUK CBR2G5, FIG. 6B is an OC3 frame configuration diagram, and FIG. 6C is a OC48 frame configuration diagram. 7A is a time chart showing an example of an input pulse waveform to the LPF, FIG. 7B is a time chart showing another example of an input pulse waveform to the LPF, and FIG. 7C is an input to the LPF. It is a time chart which shows the other example of a pulse waveform. FIG. 8 (a) is a mapping scheme diagram from OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 to OTU3, and FIG. 8 (b) is OC3 / STM-1, OC12 / STM-4 or OC48. It is explanatory drawing for demonstrating the asynchronous multiplexing system to OTU3 of / STM-16. FIG. 9A shows a mapping scheme from OC3 / STM-1, OC12 / STM-4, OC48 / STM-16 or OC192 / STM-64 to OTU2, and FIG. 9B shows OC3 / STM-1, OC12. It is explanatory drawing for demonstrating the asynchronous multiplexing system to OTU2 of / STM-4, OC48 / STM-16, or OC192 / STM-64. FIG. 10A shows a mapping scheme from OC3 / STM-1, OC12 / STM-4, OC48 / STM-16 or OC192 / STM-64 to OTU3, and FIG. 10B shows OC3 / STM-1, OC12. It is explanatory drawing for demonstrating the asynchronous multiplexing system to OTU3 of / STM-4, OC48 / STM-16, or OC192 / STM-64.

  In FIG. 1, an optical transmission device 100 is arranged at the boundary between a SONET / SDH network and a WDM network, and transmits a client signal in the SONET / SDH network and an OTUk (k = 2, 3) in the WDM network. Convert signals to and from each other. The client signal is an OC3 / STM-1 signal with a transmission bit rate of 155.520 Mbps, an OC12 / STM-4 signal with 622.080 Mbps, an OC48 / STM-16 signal with 2.48832 Gbps, or an OC192 / STM with 9.95328 Gbps. Corresponds to one of -64 signals.

  In FIG. 2, the optical transmission device 100 includes an optical module unit 10, a clock data recovery unit 20, a mapping unit 30, a demapping unit 40, an OPUk mapping / demapping unit 50, an OTUk mapping / demapping unit 60, and a first light. / Electric conversion unit 70 is provided.

  The optical transmission apparatus 100 includes an optical module unit 10, a clock data recovery unit 20, a mapping unit 30, a demapping unit 40, and an OPUk mapping / demapping unit 50 as a pair, and will be described later as ODUk (Optical Channel Data). K = 1, 2) One or a plurality of sets are provided according to the number of multiplexed frames, and a clock generation unit 80 is provided for each set.

Further, the optical transmission device 100 generates an XO (crystal oscillator) 90 that generates and outputs a reference clock in the common device to the staff mapping unit 51 of the OPUk mapping / demapping unit 50 of each set. I have.
The optical module unit 10 includes a second optical / electrical conversion unit 11 and a parallel / serial mutual conversion unit 12.

  The second optical / electrical conversion unit 11 is a part that mutually converts an optical signal and an electrical signal, converts the optical signal of the client signal received from the SONET / SDH network into an electrical signal, and performs parallel / serial mutual conversion. The data is output to the conversion unit 12. The second optical / electrical conversion unit 11 converts the electrical signal from the parallel / serial mutual conversion unit 12 into an optical signal and sends the optical signal to the transmission line of the SONET / SDH network.

  The parallel / serial interconversion unit 12 is a circuit (SerDes: SERializer / DESerializer) that mutually converts parallel data and serial data, and converts an electrical signal from the second optical / electrical conversion unit 11 into serial data. To the clock data recovery unit 20.

The clock data recovery unit 20 is a CDR (Clock and Data Recovery) that extracts data and clock from serial data after conversion of the client signal, and outputs the extracted data and clock to the mapping unit 30.
The mapping unit 30 includes a first framer unit 31 and a mapper unit 32.

  The first framer unit 31 is a part that performs frame synchronization of data based on the clock input from the clock data reproduction unit 20.

  The mapper unit 32 synchronizes the OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 frame corresponding to the data into an OC48 / STM-16 or OC192 / STM-64 frame configuration. The part to be mapped.

If the client signal received by the optical transmission apparatus 100 is OC192 / STM-64, the mapper unit 32 does not map the data to the stuff mapping unit 51 without mapping to the OC192 / STM-64 frame configuration. Forward. Also, if the client signal is set to be mapped to the OC48 / STM-16 frame and the client signal received by the optical transmission apparatus 100 is OC48 / STM-16, the mapper unit 32 may set the OC48 / STM-16 frame. The data and clock are transferred to the staff mapping unit 51 without mapping to the configuration.
The OPUk mapping / demapping unit 50 includes a staff mapping unit 51 and a destuff demapping unit 52.

  The stuff mapping unit 51 accommodates the frame mapped or transferred by the mapper unit 32 in the OPU1 payload or OPU2 payload generated by the reference clock from the XO 90, and configures the ODU1 frame or ODU2 frame.

  The destuffing demapping unit 52 demaps the ODU1 frame or ODU2 frame extracted from the OTUk mapping / demapping unit 60, and generates an OC48 / STM-16 or OC192 / STM-64 frame from the OPU1 payload or OPU2 payload. Extract. The destuff demapping unit 52 includes, for example, an ODUk demapping unit 52a for demapping an ODUk (k = 1, 2) frame and an ES (Elastic Store) unit 52b, as shown in FIG. Yes.

  The OTUk mapping / demapping unit 60 accommodates 4 or 16 ODU1 frames or 1 or 4 ODU2 frames in an OPU2 payload or an OPU3 payload generated by a reference clock from the XO 90 to form an OTU2 frame or an OTU3 frame. . Further, the OTUk mapping / demapping unit 60 demaps the OTU2 frame or OTU3 frame from the WDM network, and extracts 4 or 16 ODU1 frames or 1 or 4 ODU2 frames from the OPU2 payload or OPU3 payload.

  The first optical / electrical converter 70 is a part that converts an optical signal and an electrical signal to each other, and converts an optical signal of an OTUk (k = 2, 3) signal received from the WDM network into an electrical signal. , Output to the OTUk mapping / demapping unit 60. The first optical / electrical converter 70 converts the electrical signal from the OTUk mapping / demapping unit 60 into an optical signal and sends it to the transmission line of the WDM network.

  The clock generation unit 80 generates a clock corresponding to the client signal based on the justification function in the frame extracted by the destuff demapping unit 52. The clock generation unit 80 includes, for example, a PLL including an LPF (low-pass filter) 81 and a VCXO (voltage-controlled crystal oscillator) 82, as shown in FIG. (Phase-locked loop).

The demapping unit 40 includes a demapper unit 41 and a second framer unit 42.
The demapper unit 41 synchronizes with the clock generated by the clock generation unit 80, and the OC3 / STM-1, OC12 / STM-4, or OC48 corresponding to the client signal from the frame extracted by the destuff demapping unit 52. / STM-16 frame overhead and payload are extracted.

  If the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC192 / STM-64, the demapper unit 41 does not extract the overhead and payload of the frame and the second framer unit 42 is extracted. Then, the OC192 / STM-64 frame is transferred to the optical module unit 10. If the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC48 / STM-16 and is not mapped to the OC192 / STM-64 frame, the demapper unit 41 extracts the frame overhead and payload. Without this, the OC192 / STM-64 frame is transferred to the optical module unit 10 via the second framer unit 42.

  The second framer unit 42 configures an OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 frame based on the overhead and payload extracted by the demapper unit 41.

Next, the processing operation of the optical transmission apparatus 100 will be described.
In the following description, the optical transmission apparatus 100 uses the OC48 / STM-16 frame for the client signal that is OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 and the OTU2 signal. The case of mutual conversion will be described with reference to FIGS. In this case, four ODU1 frames are multiplexed, and the optical transmission apparatus 100 includes a pair of the optical module unit 10, the clock data recovery unit 20, the mapping unit 30, the demapping unit 40, and the OPUk mapping / demapping unit 50. 4 sets will be provided. That is, the optical transmission device 100 illustrated in FIG. 2 corresponds to the optical transmission device 100 illustrated in FIG.

  In FIG. 5B, ODU-OH is an abbreviation for optical channel data unit-overhead, and FAS-OH is frame alignment signal-overhead. The abbreviation for “Head”. OTU-OH is an abbreviation for optical channel transport unit-overhead, and OPU-OH is an abbreviation for optical channel payload unit-overhead. is there. OTU-FEC is an abbreviation for Optical Channel Transport Unit-Frame Alignment Signal.

First, a case where a client signal is converted into an OTU2 signal (transmission from a SONET / SDH network to a WDM network) will be described.
When receiving the client signal, the optical transmission device 100 converts the signal into an electric signal by the second optical / electrical conversion unit 11, converts it into serial data by the parallel / serial mutual conversion unit 12, and serializes it to the clock data reproduction unit 20. Output data.
The clock data reproduction unit 20 extracts data and a clock from the serial data and outputs them to the first framer unit 31.

  The first framer unit 31 performs data frame synchronization based on the clock input from the clock data recovery unit 20, and OC3 / STM-1, OC12 / STM-4, or OC48 / STM corresponding to the received client signal. -16 frames are constructed. For example, if the client signal received by the optical transmission apparatus 100 is OC3, the OC3 frame configuration shown in FIG.

  Then, the mapper unit 32 maps the client signal frame to the OC48 / STM-16 frame using the clock extracted by the clock data recovery unit 20 and outputs the OC48 / STM-16 frame to the stuff mapping unit 51. To do. When mapping to the OC48 / STM-16 frame, all of the client signal data, section overhead, path overhead, and payload are mapped to the corresponding columns in the OC48 / STM-16 frame. For example, if the client signal received by the optical transmission apparatus 100 is OC3, the OC3 frame shown in FIG. 6B is mapped to the OC48 frame shown in FIG. 6C.

  If the client signal received by the optical transmission apparatus 100 is OC48 / STM-16, the mapper unit 32 transfers the data and clock to the stuff mapping unit 51 without mapping to the OC48 / STM-16 frame. .

  The stuff mapping unit 51 accommodates the frame mapped or transferred by the mapper unit 32 in an OPU1 payload (ITU-T G.709 OPUk CBR2G5) generated by the reference clock from the XO 90 to form an ODU1 frame (see FIG. 5 (b)), the ODU1 frame is output to the OTU2 mapping / demapping unit 60. The frequency deviation ± 20 ppm of the SONET / SDH signal is absorbed by a JC (Justification) byte defined by ITU-T G.709 shown in FIG.

The OTU2 mapping / demapping unit 60 configures an ODTUG (Optical Channel Tributary Unit Group) 2 by multiplexing four ODU1 frames. Then, the OTU2 mapping / demapping unit 60 accommodates ODTUG2 in the OPU2 payload generated by the reference clock from the XO 90 to form an OTU2 frame (FIG. 5B), and converts the OTU2 frame to the first optical / electrical The data is output to the conversion unit 70.
The first optical / electrical converter 70 converts the OTU2 frame from the OTU2 mapping / demapping unit 60 into an optical signal and sends it to the transmission line of the WDM network.
As described above, a client signal that is OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 can be converted into an OTU2 signal.

Next, a case where the OTU2 signal is converted into a corresponding client signal (transmission from the WDM network to the SONET / SDH network) will be described.
When receiving the OTU2 signal, the optical transmission device 100 converts the OTU2 signal into an electric signal by the first optical / electrical conversion unit 70 and outputs it to the OTU2 mapping / demapping unit 60.

  The OTU2 mapping / demapping unit 60 demaps the OTU2 frame from the WDM network, extracts four multiplexed ODU1 frames from the OPU2 payload, and outputs the separated ODU1 frames to the four destuff demapping units 52, respectively. .

  The ODU1 demapping unit 52a shown in FIG. 3 in each destuffing demapping unit 52 demaps the ODU1 frame input from the OTU2 mapping / demapping unit 60 and extracts the OC48 / STM-16 frame from the OPU1 payload. And output to the ES unit 52b.

  The ES unit 52b calculates a frequency deviation based on the number of JC (Justification) bytes in the OC48 / STM-16 frame, and outputs a phase control signal to the VCXO 82 via the LPF 81. Thus, the ES unit 52 b controls the clock generation unit 80 that is a PLL, generates a clock in the VCXO 82, and outputs the clock to the demapper unit 41.

  For example, as shown in FIG. 7A, when the increase / decrease period in the number of JC bytes is constant, the duty ratio of a pulse (input pulse to the LPF 81) generated for a predetermined threshold is 50. Therefore, the VCXO 82 outputs a clock having a constant frequency. Also, as shown in FIGS. 7B and 7C, when the increase / decrease period in the number of JC bytes changes, a pulse generated for a predetermined threshold (input pulse to the LPF 81) As a result, the output frequency from the VCXO 82 changes.

  The demapper unit 41 reads the OC48 / STM-16 frame extracted by the destuff demapping unit 52 in synchronization with the clock generated by the clock generation unit 80. Then, the demapper unit 41 extracts the overhead and payload of the OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 frame corresponding to the client signal from the OC48 / STM-16 frame. Output to the framer unit 42.

  The second framer unit 42 composes an OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 frame based on the overhead and payload extracted by the demapper unit 41, and the parallel / serial mutual conversion unit 12 And output to the second optical / electrical converter 11.

The second optical / electrical conversion unit 11 converts the electrical signal from the parallel / serial mutual conversion unit 12 into an optical signal and sends it to the transmission line of the SONET / SDH network.
As described above, the OTU2 signal can be converted into a client signal that is OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16.

  In the above description, the OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 client signal and the OTU2 signal are mutually converted using the OC48 / STM-16 frame. As described above, the client signal and the OTU3 signal can be mutually converted. In this case, as shown in FIG. 8, 16 ODU1 frames are multiplexed, and the optical transmission apparatus 100 includes the optical module unit 10, the clock data recovery unit 20, the mapping unit 30, the demapping unit 40, and the OPUk mapping. / 16 sets of demapping units 50 are provided as a pair.

  Further, the optical transmission device 100 uses OC192 / STM-64 frames for client signals and OTU2 signals that are OC3 / STM-1, OC12 / STM-4, OC48 / STM-16, or OC192 / STM-64. It is also possible to convert between them. In this case, as illustrated in FIG. 9, the optical transmission apparatus 100 includes the optical module unit 10, the clock data reproduction unit 20, the mapping unit 30, the demapping unit 40, and the OPUk mapping / decoding without multiplexing the ODU2 frame. One pair of mapping units 50 is provided.

  Further, the optical transmission device 100 uses OC192 / STM-64 frames for client signals and OTU3 signals that are OC3 / STM-1, OC12 / STM-4, OC48 / STM-16 or OC192 / STM-64. It is also possible to convert between them. In this case, as shown in FIG. 10, four ODU2 frames are multiplexed, and the optical transmission apparatus 100 includes the optical module unit 10, the clock data recovery unit 20, the mapping unit 30, the demapping unit 40, and the OPUk mapping. / 4 sets of demapping units 50 are provided as a pair.

  As described above, the optical transmission device 100 according to the present embodiment includes not only OC48 / STM-16 and OC192 / STM-64 client signals, but also OC3 / STM-1 and OC12 / STM-4, which are low layers. There is also an effect of enabling transparent transmission for the client signal.

(Second embodiment of the present invention)
11 is a block diagram showing another example of the internal configuration of the clock generator shown in FIG. 2, and FIG. 12 is a block diagram showing still another example of the internal configuration of the clock generator shown in FIG. 11 and 12, the same reference numerals as those in FIGS. 1 to 10 denote the same or corresponding parts, and the description thereof is omitted.

In FIG. 11, the clock generation unit 80 further includes an XO 83, a clock loss detection unit 84, an OR gate 85, and a SEL (Selector: selector circuit) 86 compared to the clock generation unit 80 shown in FIG. 3.
The XO 83 is a crystal oscillator that generates a reference clock in the apparatus and outputs the reference clock to the SEL 86, and may be shared with the XO 90.

  The clock disconnection detector 84 detects disconnection of the phase control signal from the ES 52 b and outputs a disconnect signal to the OR gate 85.

  The OR gate 85 outputs a control signal to the SEL 86 based on the disconnection signal from the clock disconnection detection unit 84 or the alarm transfer signal from each layer which is an OTUk alarm, ODUk alarm or SONET alarm shown in Table 1 below.

  The SEL 86 changes the clock output to the demapper unit 41 from the clock from the VCXO 82 to the reference clock from the XO 83 based on the control signal from the OR gate 85.

  The optical transmission apparatus 100 according to the second embodiment is different from the first embodiment only in that the clock generation unit 80 further includes an XO 83, a clock loss detection unit 84, an OR gate 85, and a SEL 86. It is a different place. Except for the operational effects due to this difference, the same operational effects as in the first embodiment are achieved.

  In the optical transmission apparatus 100 according to the first embodiment, when the JC byte in the OPUk frame is destroyed due to a failure in the transmission path of the WDM network, the clock cannot be transmitted, the VCXO 82 is free-running, and the SONET / SDH The frequency deviation (within ± 20ppm) may not be satisfied.

  For this reason, the optical transmission device 100 according to the second embodiment switches the clock output to the demapper unit 41 from the clock of the VCXO 82 to the reference clock of the XO 83 by the SEL 86 when a transmission line failure occurs. As a result, a free run of the VCXO 82 can be avoided. As a result, in the SONET / SDH device facing the optical transmission device 100, detection of LOF (Loss of Frame: frame loss) or the like due to insufficient tolerance of the frequency deviation is detected. There exists an effect that it can prevent.

  As shown in FIG. 11, XO83 using a crystal resonator has high frequency accuracy but cannot change the frequency. Therefore, as shown in FIG. 12, the clock generation unit 80 further includes a frequency divider 87, thereby setting the frequency division number of the frequency divider 87, thereby outputting an arbitrary frequency and high frequency accuracy. There is an effect that a signal can be obtained.

  In particular, the clock generator 80 includes a phase comparator 88 that compares the phase of the clock having the frequency divided by the frequency divider 87 with the phase of the reference clock from the XO 83, as shown in FIG. The VCXO is transmitted by the reference clock on the side. Note that the frequency of the clock generated by the XO 83 shown in FIG. 12 (for example, about 78 MHz) is lower than the frequency of the clock generated by the XO 83 shown in FIG. 11 (for example, about 669 MHz).

(Third embodiment of the present invention)
13A is a block diagram showing an example of the internal configuration of the first framer unit and the mapper unit shown in FIG. 2, and FIG. 13B is a block diagram showing an example of the internal configuration of the demapper unit and the second framer unit. FIG. FIG. 14A is an explanatory diagram for explaining reinsertion processing of B1 bytes and B2 bytes on the mapper side, and FIG. 14B is for explaining reinsertion processing of B1 bytes and B2 bytes on the demapper side. It is explanatory drawing of. 13 and 14, the same reference numerals as those in FIGS. 1 to 12 denote the same or corresponding parts, and the description thereof is omitted.

In FIG. 13A, the first framer unit 31 includes a first frame synchronization unit 31a and a first B1 / B2 result detection unit 31b.
The first frame synchronization unit 31a performs frame synchronization of the data from the clock data reproduction unit 20, and outputs the data to the first B1 / B2 result detection unit 31b.

  The first B1 / B2 result detection unit 31b is OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 (for example, shown in FIG. 14A) corresponding to the data from the clock data recovery unit 20. B1 byte and B2 byte results in the left frame) are detected.

If the client signal received by the optical transmission apparatus 100 is OC192 / STM-64, the first B1 / B2 result detection unit 31b detects the B1 byte and B2 byte results without detecting the B1 byte and B2 byte results. Data and clock are transferred to 51. If the client signal is set to be mapped to the OC48 / STM-16 frame and the client signal received by the optical transmission device 100 is OC48 / STM-16, the first B1 / B2 result detection unit 31b Data and clocks are transferred to the stuff mapping unit 51 without detecting the result of the B1 byte and B2 byte.
The mapper unit 32 includes a time slot mapping unit 32a, a first B1 / B2 calculation unit 32b, and a first B1 / B2 reinsertion unit 32c.

  The time slot mapping unit 32a synchronizes the OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 frame corresponding to the data from the first framer unit 31 with the OC48 / STM-16. Or map to OC192 / STM-64 frame structure.

  If the client signal received by the optical transmission apparatus 100 is OC192 / STM-64, the time slot mapping unit 32a transfers the data and clock to the stuff mapping unit 51 without mapping. If the client signal is set to be mapped to the OC48 / STM-16 frame and the client signal received by the optical transmission device 100 is OC48 / STM-16, the time slot mapping unit 32a does not perform mapping. Data and clock are transferred to the staff mapping unit 51.

  The first B1 / B2 computing unit 32b performs B1 in the OC48 / STM-16 or OC192 / STM-64 frame (for example, the right frame shown in FIG. 14A) mapped by the time slot mapping unit 32a. Byte and B2 bytes are calculated respectively. Note that when calculating the B1 byte and the B2 byte, the calculation range of the B1 byte and the calculation range of the B2 byte are in a predetermined area of the payload and are standardized by ITU-T.

  If the client signal received by the optical transmission apparatus 100 is OC192 / STM-64, the first B1 / B2 calculation unit 32b sends the data to the stuff mapping unit 51 without calculating the B1 byte and the B2 byte. And transfer the clock. If the client signal is set to be mapped to the OC48 / STM-16 frame and the client signal received by the optical transmission apparatus 100 is OC48 / STM-16, the first B1 / B2 operation unit 32b Data and clocks are transferred to the stuff mapping unit 51 without calculating bytes and B2 bytes.

  The first B1 / B2 reinsertion unit 32c is configured to detect the B1 byte detected by the first B1 / B2 result detection unit 31b and the calculation result of the B1 byte calculated by the first B1 / B2 calculation unit 32b. XOR is calculated. The first B1 / B2 reinsertion unit 32c also detects the detection result of the B2 byte detected by the first B1 / B2 result detection unit 31b and the B2 byte calculated by the first B1 / B2 calculation unit 32b. An exclusive OR (XOR) of the calculation results is calculated.

  Then, the first B1 / B2 reinsertion unit 32c performs OC48 / STM-16 or OC192 / STM-64 frame (for example, the right frame shown in FIG. 14A) mapped by the time slot mapping unit 32a. ) Insert the B1 byte operation result into the B1 byte. Further, the first B1 / B2 reinsertion unit 32c performs OC48 / STM-16 or OC192 / STM-64 frame (for example, the right frame shown in FIG. 14A) mapped by the time slot mapping unit 32a. ) Insert the B2 byte operation result into the B2 byte.

  If the client signal received by the optical transmission apparatus 100 is OC192 / STM-64, the first B1 / B2 reinsertion unit 32c does not calculate and insert the exclusive OR (XOR). Data and clock are transferred to the mapping unit 51. If the client signal is set to be mapped to the OC48 / STM-16 frame and the client signal received by the optical transmission apparatus 100 is OC48 / STM-16, the first B1 / B2 reinsertion unit 32c Data and clocks are transferred to the stuff mapping unit 51 without calculating and inserting an exclusive OR (XOR).

In FIG. 13 (b), the demapper unit 41 includes a second frame synchronization unit 41a, a second B1 / B2 result detection unit 41b, and a time slot demapping unit 41c.
The second frame synchronization unit 41a performs frame synchronization based on the clock generated by the clock generation unit 80, and outputs the frame synchronization to the second B1 / B2 result detection unit 41b.

  The second B1 / B2 result detection unit 41b detects the results of the B1 byte and the B2 byte in the frame (for example, the right frame shown in FIG. 14B) extracted by the destuff demapping unit 52, respectively.

  If the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC192 / STM-64, the second B1 / B2 result detection unit 41b detects the result of the B1 byte and the B2 byte. The OC192 / STM-64 frame is transferred to the optical module unit 10. Further, if the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC48 / STM-16 and is not mapped to the OC192 / STM-64 frame, the result of B1 byte and B2 byte is not detected. The OC48 / STM-16 frame is transferred to the optical module unit 10.

  The time slot demapping unit 41c synchronizes with the clock generated by the clock generation unit 80, and the OC3 / STM-1, OC12 / STM- corresponding to the client signal from the frame extracted by the destuff demapping unit 52. 4 or OC48 / STM-16 frame overhead and payload are extracted.

  If the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC192 / STM-64, the time slot demapping unit 41c does not extract the frame overhead and payload, and the optical module unit 10 Transfer OC192 / STM-64 frames to If the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC48 / STM-16 and is not mapped to the OC192 / STM-64 frame, the time slot demapping unit 41c The OC48 / STM-16 frame is transferred to the optical module unit 10 without extracting the payload.

The second framer unit 42 includes a second B1 / B2 operation unit 42a and a second B1 / B2 reinsertion unit 42b.
The second B1 / B2 calculation unit 42a is configured based on the overhead and payload extracted by the time slot demapping unit 41c, and the OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 frame (for example, The B1 byte and B2 byte in the left frame shown in FIG. Note that when calculating the B1 byte and the B2 byte, the calculation range of the B1 byte and the calculation range of the B2 byte are in a predetermined area of the payload and are standardized by ITU-T.

  If the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC192 / STM-64, the second B1 / B2 operation unit 42a does not calculate the B1 byte and the B2 byte, and the optical signal is received. The OC192 / STM-64 frame is transferred to the module unit 10. If the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC48 / STM-16 and is not mapped to the OC192 / STM-64 frame, the second B1 / B2 computing unit 42a The OC48 / STM-16 frame is transferred to the optical module unit 10 without calculating bytes and B2 bytes.

  The second B1 / B2 reinsertion unit 42b is configured to detect the B1 byte detected by the second B1 / B2 result detection unit 41b and the calculation result of the B1 byte calculated by the second B1 / B2 calculation unit 42a. XOR is calculated. The second B1 / B2 re-insertion unit 42b also detects the B2 byte detection result detected by the second B1 / B2 result detection unit 41b and the B2 byte calculated by the second B1 / B2 calculation unit 42a. An exclusive OR (XOR) of the calculation results is calculated.

  Then, the second B1 / B2 reinsertion unit 42b performs the B1 byte in the OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 frame (for example, the left frame shown in FIG. 14B). Insert the B1 byte operation result into. Further, the second B1 / B2 reinsertion unit 42b is configured to use the B2 byte in the OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 frame (for example, the left frame shown in FIG. 14B). Insert the B2 byte operation result into.

  If the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC192 / STM-64, the second B1 / B2 reinsertion unit 42b calculates and inserts an exclusive OR (XOR). Without this, the OC192 / STM-64 frame is transferred to the optical module unit 10. If the client signal accommodated in the OTUk signal received by the optical transmission apparatus 100 is OC48 / STM-16 and is not mapped to the OC192 / STM-64 frame, the second B1 / B2 reinsertion unit 42b The OC48 / STM-16 frame is transferred to the optical module unit 10 without calculating and inserting an exclusive OR (XOR).

  Note that in the optical transmission apparatus 100 according to the third embodiment, only the B1 byte and B2 byte are calculated by exclusive OR and re-inserted into the B1 byte and B2 byte of the frame. This is different from the embodiment and the second embodiment. Except for the operational effects due to this difference, the same operational effects as the first embodiment and the second embodiment are exhibited.

  The optical transmission apparatus 100 according to the first and second embodiments includes a B1 byte that notifies the number of errors between sections of a SONET / SDH frame in order to terminate and map or demap a frame to be transmitted. As a B2 byte, the result of a new parity operation is transferred. In the operation result of the B1 byte and B2 byte that have been transferred, the error is erased, the error number is transmitted as 0, and an incorrect error number may be transmitted.

  For this reason, the optical transmission device 100 according to the third embodiment is configured to transmit the opposite SONET / SDH device via the WDM network without transmitting an erroneous number of errors with respect to the number of errors of B1 bytes and B2 bytes. The effect is that it can be transmitted transparently.

DESCRIPTION OF SYMBOLS 10 Optical module part 11 2nd optical / electrical conversion part 12 Parallel / serial mutual conversion part 20 Clock data reproduction | regeneration part 30 Mapping part 31 1st framer part 31a 1st frame synchronization part 31b 1st B1 / B2 result detection Unit 32 mapper unit 32a time slot mapping unit 32b first B1 / B2 operation unit 32c first B1 / B2 reinsertion unit 40 demapping unit 41 demapper unit 41a second frame synchronization unit 41b second B1 / B2 result Detection unit 41c Time slot demapping unit 42 Second framer unit 42a Second B1 / B2 operation unit 42b Second B1 / B2 reinsertion unit 50 OPUk mapping / demapping unit 51 Staff mapping unit 52 Destuff demapping unit 52a ODUk demapping unit 52b ES unit 60 O TUk mapping / demapping unit 70 First optical / electrical conversion unit 80 Clock generation unit 81 LPF
82 VCXO
84 Clock loss detection unit 85 OR gate 86 SEL
87 frequency divider 88 phase comparator 100 optical transmission device

Claims (6)

An optical transmission apparatus that mutually converts a client signal transmitted in a SONET / SDH network and an OTU2 signal or an OTU3 signal transmitted in a WDM network,
A clock data recovery unit for extracting data and a clock from the client signal;
A first framer unit that performs frame synchronization of the data based on the clock;
A mapper for mapping the frame of data to the frame structure of OC48 / STM-16 or OC192 / STM-64 in synchronization with the frame;
A stuff mapping unit configured to accommodate the frame mapped by the mapper unit in an OPU1 payload or an OPU2 payload generated by a reference clock to form an ODU1 frame or an ODU2 frame;
A mapping / demapping unit that accommodates four or sixteen ODU1 frames or one or four ODU2 frames in an OPU2 payload or an OPU3 payload generated by a reference clock to form an OTU2 frame or an OTU3 frame;
An optical transmission device comprising: The optical transmission apparatus according to claim 1,
The mapping / demapping unit demaps the OTU2 frame or the OTU3 frame from the WDM network, and extracts 4 or 16 ODU1 frames or 1 or 4 ODU2 frames from the OPU2 payload or OPU3 payload;
A destuff demapping unit that demaps the ODU1 frame or ODU2 frame extracted from the mapping / demapping unit and extracts an OC48 / STM-16 or OC192 / STM-64 frame from the OPU1 payload or OPU2 payload;
A clock generation unit that generates a clock corresponding to the client signal based on the justification function in the frame extracted by the destuff demapping unit;
In synchronization with the clock generated by the clock generator, the OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 corresponding to the client signal is extracted from the frame extracted by the destuff demapping unit. A demapper for extracting the overhead and payload of the frame;
A second framer portion constituting an OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 frame based on the overhead and payload extracted by the demapper portion;
An optical transmission device comprising: In the optical transmission device according to claim 1 or 2,
The first framer unit includes a first frame synchronization unit that performs frame synchronization of the data, and a B1 byte in an OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 frame corresponding to the data. And a first B1 / B2 result detection unit for detecting a result of B2 bytes respectively.
The mapper unit synchronizes the OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 frame corresponding to the data with the OC48 / STM-16 or OC192 / STM-64. A time slot mapping unit for mapping to a frame configuration, and a first B1 / B1 byte for calculating B1 byte and B2 byte in the OC48 / STM-16 or OC192 / STM-64 frame mapped by the time slot mapping unit. Calculating the exclusive OR of the detection result detected by the B2 calculation unit and the first B1 / B2 result detection unit and the calculation result calculated by the first B1 / B2 calculation unit; The OC48 / STM-1 mapped by the mapping unit Or optical transmission apparatus characterized by comprising a first B1 / B2 reinsertion section for operation result, respectively inserted into the B1 byte and B2 bytes in OC192 / STM-64 frame. The optical transmission apparatus according to claim 2,
The demapper unit obtains the results of the B1 byte and B2 byte in the frame extracted by the second frame synchronization unit and the destuff demapping unit based on the clock generated by the clock generation unit. The OC3 / STM-1 corresponding to the client signal from the frame extracted by the destuffing demapping unit in synchronization with the second B1 / B2 result detection unit to be detected and the clock generated by the clock generation unit A time slot demapping unit for extracting OC12 / STM-4 or OC48 / STM-16 frame overhead and payload;
The B1 byte and the B2 byte in the OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 frame configured by the second framer unit based on the overhead and payload extracted by the time slot demapping unit Of the second B1 / B2 calculation unit for calculating each of the detection results, the detection result detected by the second B1 / B2 result detection unit, and the exclusive logic of the calculation result calculated by the second B1 / B2 calculation unit A second B1 / B2 re-insertion unit that calculates the sum and inserts the calculation result into the B1 byte and B2 byte in the OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 frame, respectively. An optical transmission device comprising: An optical transmission method for mutually converting a client signal transmitted in a SONET / SDH network and an OTU2 signal or an OTU3 signal transmitted in a WDM network,
A clock data recovery step of extracting data and a clock from the client signal;
A first framer step for frame synchronization of the data based on the clock;
A mapper step for mapping the frame of data to the frame structure of OC48 / STM-16 or OC192 / STM-64 in synchronization with the frame;
A stuff mapping step of accommodating the frame mapped by the mapper step in an OPU1 payload or an OPU2 payload generated by a reference clock to form an ODU1 frame or an ODU2 frame;
A mapping / demapping step of accommodating 4 or 16 ODU1 frames or 1 or 4 ODU2 frames in an OPU2 payload or OPU3 payload generated by a reference clock to constitute an OTU2 frame or an OTU3 frame;
An optical transmission method comprising: In the optical transmission method according to claim 5,
The mapping / demapping step demaps the OTU2 frame or OTU3 frame from the WDM network to extract 4 or 16 ODU1 frames or 1 or 4 ODU2 frames from the OPU2 payload or OPU3 payload;
A destuff demapping step of demapping the ODU1 frame or ODU2 frame extracted from the mapping / demapping step to extract an OC48 / STM-16 or OC192 / STM-64 frame from the OPU1 payload or OPU2 payload;
A clock generation step for generating a clock corresponding to the client signal based on the justification function in the frame extracted by the destuffing demapping step;
In synchronization with the clock generated by the clock generation step, the OC3 / STM-1, OC12 / STM-4, or OC48 / STM-16 corresponding to the client signal is extracted from the frame extracted by the destuff demapping step. A demapper step to extract the overhead and payload of the frame;
A second framer step comprising an OC3 / STM-1, OC12 / STM-4 or OC48 / STM-16 frame based on the overhead and payload extracted by the demapper step;
An optical transmission method comprising: