JP2008054299A - Multiplex transmission apparatus, multiplex transmission system and multiplex transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily manage a clock in a synchronous multiplex transmission system. <P>SOLUTION: A multiplex transmission apparatus 10 multiplexes and transmits a synchronous signal and an asynchronous signal. The multiplex transmission apparatus 10 includes a clock extracting unit 12 that extracts a first clock C1 from the synchronous signal, and a data multiplexing unit 11 that multiplexes the synchronous signal and the asynchronous signal based on the first clock C1. The synchronous signal is, for example, a signal that complies with STM-1 regulated by an SDH. The data multiplexing unit 11 maps the asynchronous signal to a payload part PLD of an SDH frame. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multiplex transmission apparatus, a multiplex transmission system, and a multiplex transmission method. In particular, the present invention relates to a technique for multiplexing and transmitting a synchronous signal and an asynchronous signal.

  “SDH (Synchronous Digital Hierarchy)” is known as a high-speed digital communication method using an optical fiber. SDH is a digital multiplex technology that assumes synchronization across the entire network, and was standardized in 1988 by the International Telecommunications Union. The standard of synchronous multiplex transmission by SDH is defined as “STM-1 (Synchronous Transport Module Level-1)”. According to STM-1, one frame is composed of 9 rows × 270 columns (bytes) of signals. Since the frame period is defined as 125 μs, the reference transmission rate is 155.52 Mbps.

  In synchronous multiplex transmission, clock management is important. Patent Document 1 describes a clock supply method in a transmission system compatible with SDH. In the transmission system, ADMs (Add Drop Multiplexers) are arranged in a ring shape. When the clock cannot be extracted from the signal on one transmission path, the clock extracted on the other transmission path is used. Thereby, network synchronization is maintained.

  In addition, with the recent diversification of networks, a technology capable of transmitting various bit rates and types of signals is required. For example, a signal whose transmission speed is synchronized with the transmission path (hereinafter referred to as “synchronous signal”) and a signal that is not synchronized (hereinafter referred to as “asynchronous signal”). There is a need for techniques that can be transmitted.

  Patent Document 2 describes a time division multiplex transmission system that digitally transmits a synchronous signal and an asynchronous signal. The multiplexing device of the time division multiplex transmission system includes a stuff synchronization unit, a multiplexing unit, and a clock generation unit. The stuff synchronization unit performs stuff processing on the asynchronous signal, and converts the asynchronous signal into a stuff synchronization signal synchronized with the speed of the transmission path. The multiplexing unit time-division multiplexes the stuff synchronization signal and the synchronization signal, and sends the multiplexed signal to the transmission path. The clock generation unit is an oscillator that generates a transmission clock corresponding to the transmission path.

  Patent Document 3 describes a general technique for mapping a synchronous digital signal and an asynchronous digital signal to an SDH frame (STM frame) when multiplexing the synchronous digital signal and the asynchronous digital signal. For example, inside a router having an SDH interface, using Point-to-Point-Protoco 1 (PPP) or the like, a packet in an IP (Internet Protocol) network is mapped in correspondence with a virtual container in the frame format of the SDH network. And the client payload. Further, a path overhead (Path 0verHead: POH) is added to the client payload and stored in the SDH frame. Further, a pointer indicating the top position of the container is inserted into the section overhead (Section 0verHead: SOH). This pointer indicates a frame phase shift.

  In SDH, a staff synchronization function using a pointer is employed. For example, when the frequency of the low-speed digital signal to be multiplexed is slightly lower than the frequency of the payload of the STM frame, the normal stuffing process is performed in which the stuff byte is inserted immediately after the pointer byte of the pointer. Conversely, when the frequency of the low-speed digital signal to be multiplexed is slightly higher than the frequency of the payload of the STM frame, a negative stuffing process is performed in which user information is stored in the last byte of the pointer. If the frequency of the low-speed digital signal to be multiplexed matches the frequency of the payload of the STM frame, the stuff process is not performed. Frequency synchronization is realized by such positive / negative stuff processing, and even when synchronous digital transmission is performed, it is possible to perform transmission by time-division multiplexing asynchronous digital signals with stable communication quality.

  FIG. 15 of Patent Document 3 shows an example of a transmission system. The transmission system includes a multiplexing device and a separation device.

  The multiplexing device includes a receiving unit that receives an optical signal, a frequency synchronization unit, a common control unit, a multiple conversion unit, a transmitting unit that transmits an optical signal, and a clock supply unit. The receiving unit photoelectrically converts a low-speed optical signal and inputs it to the frequency synchronization unit. The frequency synchronization unit detects the phase difference between the recovered clock extracted from the low-speed digital signal and the clock supplied from the network-synchronized oscillator, and executes positive stuff when the magnitude exceeds a certain positive stuff threshold. Then, when it falls below a certain negative stuff threshold, negative stuff is executed to synchronize the low speed digital signal. The overhead is composed of a stuff information transfer area and a negative stuff bit, and information on whether or not stuff processing has been performed is sent to the separation device. The multiplex conversion unit synthesizes the synchronized digital signal and overhead and time-division multiplexes with other low-speed digital signals. The generated high-speed digital signal is converted into an optical signal by the transmission unit and transmitted to the communication path.

  The demultiplexer includes a receiving unit that receives the multiplexed high-speed digital signal, a demultiplexing unit, a frequency restoration unit, a common control unit, and a transmission unit that transmits the restored low-speed digital signal. The receiving unit photoelectrically converts the multiplexed high-speed digital signal and inputs it to the demultiplexing unit. The demultiplexing unit demultiplexes the high-speed digital signal into a plurality of low-speed digital signals and inputs them to the frequency restoration unit. The frequency restoration unit refers to the stuff information transfer area, removes stuff bits when positive stuff processing is performed, reads data from the negative stuff bits when negative stuff processing is performed, and outputs a low-speed digital signal. Restore. The transmission unit transmits the restored low-speed digital signal to the low-speed transmission device.

JP-A-5-227177 Japanese Patent Publication No. 8-13021 JP 2001-177491 A

  In synchronous multiplex transmission, clock management is important. On the other hand, when the clock to be used can be selected from an external clock, an internal clock, an extracted clock extracted from a signal, etc., the operation and maintenance of the system becomes complicated.

  An object of the present invention is to provide a technique capable of reducing the burden of operation and maintenance of a synchronous multiplex transmission system.

  [Means for Solving the Problems] will be described below using the numbers and symbols used in [Best Mode for Carrying Out the Invention]. These numbers and symbols are added in parentheses in order to clarify the correspondence between the description of [Claims] and [Best Mode for Carrying Out the Invention]. However, these numbers and symbols should not be used for the interpretation of the technical scope of the invention described in [Claims].

  According to the present invention, a technique for multiplexing and transmitting a synchronous signal and an asynchronous signal is provided.

  In a first aspect of the present invention, a multiplex transmission device (2, 4) is provided. The multiplex transmission apparatus (2, 4) includes a clock extraction unit (12) that extracts a first clock (C1) from a synchronous signal, and the synchronous signal and an asynchronous signal based on the first clock (C1). And a data multiplexing unit (11) for multiplexing. The synchronous signal is, for example, a signal that conforms to STM-1 defined by SDH. The data multiplexing unit (11) maps the synchronous signal and the asynchronous signal to the payload portion (PLD) of the SDH frame.

  The multiplex transmission apparatus (2, 4) further includes a fixed oscillator (13) that generates a free-run clock (C2), a first clock (C1) and a free-run clock (C2) that are extracted by the clock extraction unit (12). ) May be provided. When the clock extraction by the clock extraction unit (12) is normal, the clock selection unit (14) outputs the first clock (C1) received from the clock extraction unit (12) to the data multiplexing unit (11). When the clock extraction by the clock extraction unit (12) is not normal, the clock selection unit (14) outputs the free-run clock (C2) to the data multiplexing unit (11).

  The data multiplexing unit (11) may generate a multiplexed signal by time-division multiplexing a synchronous signal and an asynchronous signal.

  The multiplex transmission device (4) further includes a plurality of transponders (40-1) and wavelength division multiplexing that performs wavelength division multiplexing on a plurality of signals output from the plurality of transponders (40-1). A part (41) may be provided. In this case, each of the plurality of transponders (40-1) includes the clock extraction unit (12) and the data multiplexing unit (11). Each of the plurality of transponders (40-1) converts the multiplexed signal into the plurality of signals having different wavelengths.

  In a second aspect of the present invention, a multiplex transmission system (1) is provided. The multiplex transmission system (1) includes a transmission device (2-1, 4-1) and a reception device (2-1, 4-1) connected to the transmission device (2-1, 4-1) via a transmission path (3, 5). 2-2, 4-2). The transmission device (2-1, 4-1) includes a clock extraction unit (12) that extracts the first clock (C1) from the synchronous signal, and the synchronous signal and the asynchronous signal based on the first clock (C1). And a data multiplexing unit (11) that multiplexes the signals and generates a multiplexed signal. On the other hand, the receiving device (2-2, 4-2) includes a data separation unit (21) that separates the multiplexed signal into a synchronous signal and an asynchronous signal.

  The synchronous signal is, for example, a signal that conforms to STM-1 defined by SDH. The data multiplexing unit (11) maps the synchronous signal and the asynchronous signal to the payload portion (PLD) of the SDH frame.

  The transmission devices (2-1, 4-1) further include a fixed oscillator (13) that generates a free-run clock (C2), a first clock (C1) extracted by the clock extraction unit (12), and a free rank. A clock selector (14) for receiving the lock (C2). When the clock extraction by the clock extraction unit (12) is normal, the clock selection unit (14) outputs the first clock (C1) received from the clock extraction unit (12) to the data multiplexing unit (11). When the clock extraction by the clock extraction unit (12) is not normal, the clock selection unit (14) outputs the free-run clock (C2) to the data multiplexing unit (11).

  The data multiplexing unit (11) may generate a multiplexed signal by time-division multiplexing a synchronous signal and an asynchronous signal.

  The transmission device (4-1) further wavelength-divides the plurality of first transponders (40-1) and the plurality of signals having different wavelengths output from the plurality of first transponders (40-1). A wavelength multiplexing unit (41) that performs multiplexing and generates a wavelength multiplexed signal may be provided. In this case, each of the plurality of first transponders (40-1) includes the above-described clock extraction unit (12) and data multiplexing unit (11). Each of the plurality of transponders (40-1) converts the multiplexed signal into the plurality of signals having different wavelengths. On the other hand, the receiving device (4-2) further includes a wavelength separation unit (42) that separates the wavelength multiplexed signal into a plurality of signals having different wavelengths, and a plurality of second transponders that receive each of the plurality of signals. (40-2). In this case, each of the plurality of second transponders (40-2) includes the data separator (21) described above. Each second transponder (40-2) converts a corresponding signal among a plurality of signals into a multiplexed signal, and separates the multiplexed signal into a synchronous signal and an asynchronous signal.

  In a third aspect of the present invention, a multiplex transmission method is provided. The multiplex transmission method includes (A) extracting a first clock (C1) from a synchronous signal, and (B) multiplexing the synchronous signal and the asynchronous signal based on the first clock (C1). And (C) transmitting a signal generated based on the multiplexed signal.

  The synchronous signal is, for example, a signal that conforms to STM-1 defined by SDH. In the step (B), the synchronous signal and the asynchronous signal are mapped to the payload portion (PLD) of the SDH frame.

  In the step (B), a multiplexed signal may be generated by time division multiplexing of a synchronous signal and an asynchronous signal.

  The step (C) includes (a) a step of converting the multiplexed signal into a signal of a predetermined wavelength, and (b) wavelength division multiplexing for a plurality of signals having different wavelengths obtained by the step (a). And generating a wavelength multiplexed signal, and (c) transmitting a signal generated based on the wavelength multiplexed signal.

  According to the present invention, the clock used in the multiplex transmission of the synchronous signal and the asynchronous signal is fixed to the clock extracted from the synchronous signal. Therefore, clock management becomes unnecessary, and the burden of system operation and maintenance can be reduced.

  A multiplex transmission apparatus, a multiplex transmission system, and a multiplex transmission method according to embodiments of the present invention will be described with reference to the accompanying drawings.

1. First Embodiment FIG. 1 schematically shows a configuration of a multiplex transmission system 1 according to a first embodiment of the present invention. The multiplex transmission system 1 conforms to SDH (Synchronous Digital Hierarchy), and the reference transmission speed is 155.52 Mbps. In FIG. 1, a multiplex transmission system 1 includes multiplex transmission apparatuses 2-1 and 2-2, and the multiplex transmission apparatuses 2-1 and 2-2 are connected to each other through a transmission line 3 of an optical fiber. The multiplex transmission apparatus 2-1 is a transmission side, and is hereinafter referred to as a transmission apparatus 2-1. On the other hand, the multiplex transmission device 2-2 is a receiving side, and is hereinafter referred to as a receiving device 2-2.

  The transmission apparatus 2-1 includes a multiplexing apparatus 10 that multiplexes signals. The multiplexing device 10 generates a multiplexed signal and sends the generated multiplexed signal to the receiving device 2-2 via the transmission path 3. On the other hand, the reception device 2-2 includes a separation device 20 that receives the transmitted multiplexed signal and de-multiplexes the received multiplexed signal. The data transmission between the transmission device 2-1 and the reception device 2-2 is completely transparent transmission, and the signal input to the transmission device 2-1 is output from the reception device 2-2 as it is.

  According to the present embodiment, multiplex transmission of a synchronous signal and an asynchronous signal is performed. For example, in FIG. 1, an STM (Synchronous Transport Module) signal that is a synchronous signal is a signal that conforms to STM-1 (155.52 Mbps). On the other hand, GbE signals and DS1 signals are listed as asynchronous signals. The GbE signal (1.25 Gbps) is a signal conforming to the GbE (Giga-bit Ethernet) standard. The DS1 signal (1.544 Mbps) is a signal conforming to the DS1 (Digital Signal Level-1) standard.

  The multiplexing device 10 of the transmission device 2-1 receives one STM signal, m (m is a natural number) GbE signals, and n (n is a natural number) DS1 signals. Multiplexer 10 generates a multiplexed signal by multiplexing these signals, and sends the generated multiplexed signal to transmission path 3. The separation device 20 of the reception device 2-2 receives the multiplexed signal transmitted via the transmission path 3. Then, the separation device 20 separates the multiplexed signal into one STM signal, m GbE signals, and n DS1 signals.

  FIG. 2 shows the configuration of the multiplexer 10 and the separator 20 in detail. The multiplexing device 10 includes a data multiplexing unit 11, a clock extraction unit 12, a fixed oscillator 13, and a clock selection unit 14. On the other hand, the separation device 20 includes a data separation unit 21. Hereinafter, the operation of the multiplex transmission system 1 according to the present embodiment will be described with reference to FIG.

  The clock extraction unit 12 receives the STM signal and extracts the clock C1 from the received STM signal. The clock C1 extracted from the STM signal compliant with STM-1 is hereinafter referred to as “STM clock”. The clock extraction unit 12 outputs the extracted STM clock C1 to the clock selection unit 14. Further, the clock extraction unit 12 outputs the STM signal to the data multiplexing unit 11.

  The fixed oscillator 13 generates a free-run clock C2 that is used when no STM signal is input. The free-run clock C2 is 155.52 Mbps, which is the same as STM-1. The fixed oscillator 13 outputs the free-run clock C2 to the clock selection unit 14.

  The clock selection unit 14 receives the STM clock C1 and the free-run clock C2 and selects one of them. Specifically, when the STM clock C1 is normally extracted, the clock selection unit 14 selects the STM clock C1. On the other hand, when the STM clock C1 is not normally extracted, such as when the input of the STM signal is cut off, the clock selection unit 14 selects the free-run clock C2. Then, the clock selection unit 14 outputs the selected clock selected to the data multiplexing unit 11.

  The data multiplexer 11 receives the selected clock selected by the clock selector 14 in addition to the above-described one STM signal, m GbE signals, and n DS1 signals. Then, the data multiplexing unit 11 performs time division multiplexing (TDM: Time Division Multiplex) of the plurality of signals based on the selected clock (usually the STM clock C1). That is, the data multiplexing unit 11 performs time division multiplexing by multiplying and using the STM clock C1 extracted from the STM signal.

  FIG. 3 conceptually shows a configuration of an SDH frame (STM-N frame) generated in SDH. As shown in FIG. 3, one SDH frame is composed of 9 rows × (270 × N) columns of signals. The frame period is defined as 125 μs. The SDH frame includes an overhead part OH (9 × N columns) and a payload part PLD (261 × N columns) in which multiplexed information is stored. The STM-1 frame corresponds to a case where N is 1.

  In multiplexing the synchronous signal and the asynchronous signal, the data multiplexing unit 11 maps the synchronous signal and the asynchronous signal to the payload part PLD of the SDH frame (STM-N frame). For example, the GbE signal is mapped to the payload part PLD of the SDH frame by “GFP (General Framing Procedure)”. GFP is a technology for mapping general-purpose frames to SDH frames. 7041 is standardized. Further, for example, the DS1 signal is mapped to the payload part PLD of the SDH frame by the “stuff multiplexing method”. The staff multiplexing method is ITU-T G. 707 is standardized.

  In this manner, the data multiplexing unit 11 performs time division multiplexing of the STM signal that is a synchronous signal, the GbE signal that is an asynchronous signal, and the DS1 signal, and generates a multiplexed signal that includes an SDH frame. For example, the data multiplexing unit 11 generates a multiplexed signal composed of STM-16 frames (N = 16) by time division multiplexing. The multiplexing device 10 converts the multiplexed signal (multiplexed electrical signal) generated by the data multiplexing unit 11 into a multiplexed optical signal, and sends the multiplexed optical signal to the transmission path 3.

  The separation device 20 of the reception device 2-2 receives the multiplexed optical signal from the transmission path 3, and converts the multiplexed optical signal into a multiplexed electrical signal. The data separator 21 of the separator 20 receives the multiplexed electrical signal. The data separator 21 separates the received multiplexed signal and reproduces one STM signal, m GbE signals, and n DS1 signals.

  As described above, according to this embodiment, the synchronous signal and the asynchronous signal are mapped to the SDH frame, and the time division multiplexing of the synchronous signal and the asynchronous signal is performed. In the time division multiplexing, basically, the STM clock C1 extracted from the STM signal is used. In other words, the clock used in the multiplex transmission of the synchronous signal and the asynchronous signal is fixed to the STM clock C1 extracted from the STM signal that is the synchronous signal. Therefore, clock management becomes unnecessary, and the burden of operation and maintenance of the multiplex transmission system 1 can be reduced.

2. Second Embodiment The present invention can also be applied to a wavelength division multiplex (WDM) transmission system. According to the wavelength division multiplexing method, a plurality of optical signals having different wavelengths are multiplexed, and the multiplexed signals are transmitted through one optical fiber.

  FIG. 4 schematically shows the configuration of a WDM multiplex transmission system 1 to which the present invention is applied. In FIG. 4, the multiplex transmission system 1 includes multiplex transmission apparatuses 4-1 and 4-2, and the multiplex transmission apparatuses 4-1 and 4-2 are connected to each other through an optical fiber transmission line 5. The multiplex transmission device 4-1 is a transmission side, and is hereinafter referred to as a transmission device 4-1. On the other hand, the multiplex transmission device 4-2 is a receiving side, and is hereinafter referred to as a receiving device 4-2.

  The transmission device 4-1 converts the input data into a signal of a predetermined wavelength, and generates a wavelength multiplexed signal by wavelength division multiplexing a plurality of signals obtained by wavelength conversion. Then, the transmission device 4-1 transmits the generated wavelength multiplexed signal to the reception device 4-2 through the transmission path 5. The receiving device 4-2 receives the wavelength multiplexed signal and separates the received wavelength multiplexed signal into a plurality of signals. Further, the receiving device 4-2 performs wavelength conversion on each of the plurality of signals to obtain original data.

  As illustrated in FIG. 4, the transmission device 4-1 includes a plurality of transponders (TPND) 40-1, a wavelength multiplexing unit (OMUX: Optical Multiplexer) 41, and an optical amplification unit 43-1. On the other hand, the receiving device 4-2 includes a plurality of transponders 40-2, a wavelength demultiplexer (ODMUX) 42, and an optical amplifying unit 43-2. According to the present embodiment, each of the transponders 40-1 and 40-2 has the function according to the present invention, that is, the functions of the multiplexer 10 and the separator 20 shown in FIG.

  More specifically, in the transmission device 4-1, one STM signal, m GbE signals, and n DS1 signals are input to one transponder 40-1. Then, the multiplexer 10 of the transponder 40-1 multiplexes the input signals by the same method as in the first embodiment. Furthermore, the transponder 40-1 converts the signal obtained by multiplexing into a signal having a predetermined wavelength, and outputs the signal obtained by the wavelength conversion to the wavelength multiplexing unit 41. The predetermined wavelength is slightly different for each of the plurality of transponders 40-1.

  The wavelength multiplexing unit 41 receives a plurality of signals having different wavelengths from the plurality of transponders 40-1. The wavelength multiplexing unit 41 generates a wavelength multiplexed signal by wavelength division multiplexing the plurality of signals. The generated wavelength multiplexed signal (WDM signal) is amplified by the optical amplifying unit 43-1 and sent to the transmission line 5.

  In the receiving device 4-2, the wavelength demultiplexing unit 42 receives the wavelength multiplexed signal (WDM signal) transmitted through the transmission path 5. Then, the wavelength demultiplexing unit 42 demultiplexes the received wavelength multiplexed signal to obtain a plurality of signals having different wavelengths. The wavelength separation unit 42 outputs the obtained plurality of signals to the plurality of transponders 40-2, respectively.

  In the reception device 4-2, each transponder 40-2 receives a signal from the wavelength separation unit 42. Each transponder 40-2 converts the received signal into a signal having the original wavelength. Further, the separation device 20 of each transponder 40-2 separates the signal obtained by the wavelength conversion by the same method as in the first embodiment. As a result, one STM signal, m GbE signals, and n DS1 signals are obtained.

  Also in this embodiment, the same effect as that of the first embodiment can be obtained. That is, it is possible to reduce the burden of operation / maintenance of the multiplex transmission system 1.

FIG. 1 is a block diagram showing a configuration of a multiplex transmission system according to the first embodiment of the present invention. FIG. 2 is a block diagram showing in detail the configuration of the multiplex transmission apparatus according to the first embodiment. FIG. 3 is a diagram conceptually showing the structure of the SDH frame. FIG. 4 is a block diagram showing a configuration of a multiplex transmission system according to the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multiplex transmission system 2 Multiplex transmission apparatus 2-1 Transmission apparatus 2-2 Reception apparatus 3 Transmission path 4 Multiplex transmission apparatus 4-1 Transmission apparatus 4-2 Reception apparatus 5 Transmission path 10 Multiplexer 11 Data multiplexing part 12 Clock extraction part 13 Fixed oscillator 14 Clock selection unit 20 Separation device 21 Data separation unit 40 Transponder 41 Wavelength multiplexing unit 42 Wavelength separation unit 43 Optical amplification unit OH Overhead unit PLD Payload unit

Claims (17)

A multiplex transmission apparatus for multiplex transmission of synchronous and asynchronous signals,
A clock extractor for extracting a first clock from the synchronous signal;
A multiplex transmission apparatus comprising: a data multiplexing unit that multiplexes the synchronous signal and the asynchronous signal based on the first clock. The multiplex transmission apparatus according to claim 1,
The synchronization signal is a signal compliant with STM-1 (Synchronous Transport Module Level-1) defined by SDH (Synchronous Digital Hierarchy). The multiplex transmission apparatus according to claim 2,
The data multiplexing unit maps the synchronous signal and the asynchronous signal to a payload part of an SDH frame. The multiplex transmission apparatus according to any one of claims 1 to 3,
A fixed oscillator that generates a free-run clock;
A clock selection unit that receives the first clock and the free-running clock extracted by the clock extraction unit;
When the clock extraction by the clock extraction unit is normal, the clock selection unit outputs the first clock received from the clock extraction unit to the data multiplexing unit,
When the clock extraction by the clock extraction unit is not normal, the clock selection unit outputs the free-run clock to the data multiplexing unit. A multiplex transmission apparatus according to any one of claims 1 to 4,
The data multiplexing unit is a multiplex transmission apparatus that generates a multiplexed signal by time division multiplexing (TDM) of the synchronous signal and the asynchronous signal. The multiplex transmission apparatus according to claim 5,
Multiple transponders,
A wavelength multiplexing unit that performs wavelength division multiplexing (WDM) on a plurality of signals having different wavelengths output from each of the plurality of transponders; and
Each of the plurality of transponders includes the clock extraction unit and the data multiplexing unit, and each of the plurality of transponders converts the multiplexed signal into the plurality of signals having different wavelengths. A multiplex transmission system for multiplex transmission of synchronous and asynchronous signals,
A transmitting device;
A receiving device connected to the transmitting device via the transmission path,
The transmitter is
A clock extractor for extracting a first clock from the synchronous signal;
A data multiplexing unit that multiplexes the synchronous signal and the asynchronous signal based on the first clock to generate a multiplexed signal;
The receiving apparatus includes a data separator that separates the multiplexed signal into the synchronous signal and the asynchronous signal. The multiplex transmission system according to claim 7, wherein
The synchronization system signal is a signal compliant with STM-1 (Synchronous Transport Module Level-1) defined by SDH (Synchronous Digital Hierarchy). The multiplex transmission system according to claim 8, wherein
The data multiplexing unit maps the synchronous signal and the asynchronous signal to a payload portion of an SDH frame. A multiplex transmission system according to any one of claims 7 to 9,
The transmitter is
A fixed oscillator that generates a free-run clock;
A clock selection unit that receives the first clock and the free-running clock extracted by the clock extraction unit;
When the clock extraction by the clock extraction unit is normal, the clock selection unit outputs the first clock received from the clock extraction unit to the data multiplexing unit,
When the clock extraction by the clock extraction unit is not normal, the clock selection unit outputs the free-run clock to the data multiplexing unit. A multiplex transmission system according to any one of claims 7 to 10,
The data multiplexing unit generates a multiplexed signal by time division multiplexing (TDM) of the synchronous signal and the asynchronous signal. The multiplex transmission system according to claim 11, comprising:
The transmitter is
A plurality of first transponders;
A wavelength multiplexing unit that performs wavelength division multiplexing (WDM) on a plurality of signals having different wavelengths output from each of the plurality of first transponders, and generates a wavelength multiplexed signal; and
Each of the plurality of first transponders includes the clock extraction unit and the data multiplexing unit, and each of the plurality of transponders converts the multiplexed signal into the plurality of signals having different wavelengths,
The receiving device is:
A wavelength separator that separates the wavelength multiplexed signal into a plurality of signals having different wavelengths;
A plurality of second transponders for receiving each of the plurality of signals;
Each of the plurality of second transponders includes the data separation unit, and each of the second transponders converts a corresponding signal among the plurality of signals into the multiplexed signal, and converts the multiplexed signal to the synchronization A multiplex transmission system that separates system signals and asynchronous signals. A multiplex transmission method for multiplex transmission of synchronous and asynchronous signals,
(A) extracting a first clock from the synchronous signal;
(B) multiplexing the synchronous signal and the asynchronous signal based on the first clock to generate a multiplexed signal;
(C) transmitting a signal generated based on the multiplexed signal. The multiplex transmission method according to claim 13, comprising:
The synchronization system signal is a signal that conforms to STM-1 (Synchronous Transport Module Level-1) defined by SDH (Synchronous Digital Hierarchy). 15. The multiplex transmission method according to claim 14, wherein
In the step (B), the synchronous signal and the asynchronous signal are mapped to a payload portion of an SDH frame. The multiplex transmission method according to any one of claims 13 to 15,
In the step (B), the multiplexed signal is generated by time division multiplexing (TDM) of the synchronous signal and the asynchronous signal. The multiplex transmission method according to claim 16, wherein
The step (C) includes:
(A) converting the multiplexed signal into a signal of a predetermined wavelength;
(B) Steps of performing wavelength division multiplexing (WDM) on a plurality of signals having different wavelengths obtained by the step (a) to generate a wavelength multiplexed signal;
And (c) transmitting a signal generated based on the wavelength multiplexed signal.

Images