JPH08204677A - Optical transmitter - Google Patents

Abstract

PURPOSE: To attain sure bit multiplex processing without use of a large capacity phase fluctuation absorption memory. CONSTITUTION: A timing signal generating section 400 of a bit multiplexer/ demultiplexer 300 generates a synchronization clock CK 43, which is superimposed onto reception optical transmission signals D30, D40 and the result is transferred respectively to frame multiplexers/demultiplexers 100, 200. Each of the frame multiplexers/demultiplexers 100, 200 extracts the synchronization clock CK 43 from reception optical transmission signals D30, D40. Synchronization processing and frame multiplex processing of STM-1 signals CH1-CH16 are conducted by using the synchronization clock CK 43 to send transmission optical signals L10, L20 to the bit multiplexer/demultiplexer 300.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device used in an optical synchronous communication system.

[0002]

2. Description of the Related Art Recently, network construction based on a new global standard of synchronous hierarchy has become active. This is called SDH (Synchronous Digital Hierarchy),
So far, STM-16 (Synchronous Transport)
Mode level 16), that is, a backbone transmission system of 2,488.32 Mbit / s has been put to practical use. With the increase in communication demand,
Although standardization of higher-speed STM-64 and the like is in progress, it is difficult to realize the device and it is expected that it will take some time before it is put into practical use.

Therefore, in order to easily increase the transmission capacity per optical fiber, an optical transmission device of the bit multiplexing system is being put to practical use. FIG. 7 shows an example of the configuration of such a conventional optical transmission apparatus, which is composed of two SDH-compliant STM-16 type frame multiplexer / demultiplexers 1 and 2 and a bit multiplexer / demultiplexer 3. To be done.

The frame multiplexer / demultiplexers 1 and 2 each have a synchronous clock CK in the station as an operating clock.
11, CK21 and preliminary synchronization clocks CK12 and CK22 are supplied, and also optical transmission signals L3 and L4 and 16-channel STM-1 signals CH1 to CH16 are supplied.

The optical transmitters (OS) 11 and 21 are provided with 16-channel STMs synchronized with the synchronization clocks of the frame multiplexer / demultiplexers 1 and 2, respectively.
−1 signals CH1 to CH16 are supplied. Optical transmitter (O
S) 11 and 21 frame-multiplex STM-1 signals CH1 to CH16 of 16 channels using respective operation clocks to generate STM-16 signals, convert them into optical transmission signals L1 and L2, and output them. . This optical transmission signal L1,
L2 is sent to the optical receivers (OR) 31 and 32 in the bit multiplexer / demultiplexer 3, respectively.

The optical receivers 31 and 32 respectively convert the optical transmission signals L1 and L2 into electrical signals, and the STM-16 signal D
1 and D2 are reproduced and clocks CK1 and
Extract CK2. The STM-16 signals D1 and D2 are output to the phase fluctuation absorbing memories 33 and 34, respectively.
The clocks CK1 and CK2 are output to the phase fluctuation absorbing memories 33 and 34, respectively, and the selector 3
5 is output.

The selector 35 selects one of the clocks CK1 and CK2 as necessary and outputs the clock CK0.
Is output as. The clock CK0 selected by the selector 35 is supplied to the phase fluctuation absorbing memories 33 and 34.

The phase fluctuation absorbing memories 33 and 34 receive the STM-16 signals D1 and D2 as clocks CK1 and C, respectively.
After reading in synchronization with K2, it reads out in synchronization with clock CK0. Read STM-16 signals D1 ', D
2 ′ is input to the multiplexer (MUX) 36.

The multiplexer 36 time-division-multiplexes the STM-16 signal D1 'and the STM-16 signal D2', and S
A signal (2 × ST) having twice the amount of information as the TM-16 signal.
M-16) is generated and transmitted to another station. On the other hand, the time division multiplexed signal (2 × STM-16) transmitted from another station is input to the demultiplexer (DMUX) 37.

The demultiplexer 37 converts the time division multiplexed signal into two systems of STM-16 signals (2 × STM-16) D3.
, D4. This STM-16 signal D3, D4
Are input to the optical transmitters (OS) 38 and 39, respectively.

The optical transmitters 38 and 39 are respectively STM-
The 16 signals D3 and D4 are converted into optical transmission signals L3 and L4 and sent to the frame multiplexer / demultiplexers 1 and 2. The optical transmission signals L3 and L4 are received by the optical receivers (OR) 12 and 22 in the frame multiplexer / demultiplexers 1 and 2, respectively, and converted into STM-16 signals. These STM-
The 16 signals are separated into 16-channel STM-1 signals CH1 to CH16 by a separation unit (not shown).

The operation of the conventional optical transmission device having the above configuration will be described. Two sets of 16-channel STM-1
The signals CH1 to CH16 are respectively frame-multiplexed in the frame multiplexer / demultiplexers 1 and 2 using the synchronous clocks CK11 and CK12 of the frame multiplexers / demultiplexers, and then converted into optical transmission signals L1 and L2, and bit multiplexed / demultiplexed. It is sent to the separation device 3. The optical transmission signals L1 and L2 are converted into electrical signals by the optical receivers 31 and 32, respectively, and S
The TM-16 signals D1 and D2 are reproduced. This STM-
The 16 signals D1 and D2 are written in the phase fluctuation absorption memories 33 and 34 at clocks CK1 and CK2, respectively, and both are read at the clock CK0,
The phase difference between the two signals is absorbed and output as STM-16 signals D1 'and D2' which are synchronized with each other.

The STM-16 signal D1 'and the STM-16 signal D2' are time-division multiplexed by the multiplexer 36 to form a time-division multiplexed signal (2.times.STM-16) having a double transmission rate. Sent to other stations.

On the other hand, the time division multiplexed signal (2.times.STM-16) transmitted from another station and having a double transmission rate is sent by the demultiplexer 37 to two systems of STM-16 signals D3 and D.
Divided into 4. The STM-16 signals D3 and D4 are
Optical transmission signals L3, L3 are transmitted by the optical transmitters 38, 39, respectively.
After being converted to L4, it is sent to the frame multiplexer / demultiplexers 1 and 2, and 16-channel STM-1 signals CH1 to CH are sent.
It is separated into 16.

Therefore, if the optical transmission device having the above configuration is used, a time division multiplexed signal (2 × STM-
16) can be transmitted and received, and the amount of transmission per optical fiber can be easily increased.

By the way, as described above, in the above-mentioned optical transmission apparatus, the phase change absorption memories 33 and 34 are used to synchronize the STM-16 signals D1 and D2 when switching the synchronous clocks of the frame multiplexer / demultiplexers 1 and 2. Phase fluctuations that may occur during the period are absorbed, and the bit multiplexing in the multiplexer 36 is normally performed.

That is, suppose now that one of the synchronization clocks C is
If a failure occurs in K11 and CK21, the synchronization clock is switched to the preliminary synchronization clock CK12 or CK22. Here, the synchronous clocks CK11, CK12 and CK21, CK22 used by the frame multiplexer / demultiplexers 1 and 2 are used.
The phase difference between and is not guaranteed. Therefore, when the device tries to synchronize with a new clock after switching the synchronization clock, the phase of this reference synchronization clock may be shifted by one cycle at worst, and this phase variation is stored in the memories 33 and 34. I try to absorb it.

However, with such a conventional configuration, the maximum value of the phase fluctuation, that is, 1 of the synchronous clock.
The memories 33 and 34 must have a capacity necessary to absorb the period. For example, if the general sync clock is 64K + 8K (composite signal), 1.544Mbit / s (bipolar signal), 2.048Mbit / s (bipolar signal), 2.048MHz (sine wave), etc. The amount of phase fluctuation that must be performed is on the order of microseconds, and memories 33 and 34 having capacities corresponding thereto are required. However, as described above, STM-16 type frame multiplexing /
The bit rate of the transmission signal of the separation device is 2,488.32 Mbit / s, and this transmission signal is stored in the memory 33 for the microsecond order.
To accommodate 34, a huge size of memory is required. When such a memory is mounted, the power consumption of the device increases, and high-density mounting becomes difficult. Further, since the propagation delay of the signal in the device is proportional to the size of the memory, the increase of the propagation delay cannot be ignored.

[0019]

As described above, since the conventional optical transmission device requires a memory of a huge size, the power consumption of the device increases, the mounting density decreases, and the signal in the device increases. However, there is a problem in that the propagation delay of is increased.

The present invention has been made to solve the above problems, and enables reliable bit multiplex processing without using a large capacity memory for absorbing phase fluctuations, thereby reducing power consumption and high packing density. It is an object of the present invention to provide an optical transmission device capable of achieving high speed and reducing signal propagation delay.

[0021]

In order to achieve the above-mentioned object, each of the optical transmission devices according to the present invention frame-multiplexes a transmission signal group for transmission, converts it into an optical transmission signal for transmission, and sends it out. And a plurality of frame multiplexer / demultiplexers having a function of separating the optical transmission signal for reception having the same format as the optical transmission signal for transmission into a transmission signal group for reception having the same format as the transmission signal group for transmission and outputting the same. , A plurality of transmission optical transmission signals are synchronized and then time division multiplexed to generate a transmission bit multiplexed signal, and a reception bit multiplexed signal of the same format as this transmission bit multiplexed signal is used as a transmission optical transmission signal. Optical equipped with a bit multiplexer / demultiplexer having a function of time-division demultiplexing into a plurality of optical transmission signals for reception of the same format and sending them to a frame multiplexer / demultiplexer respectively In the transmission device, the bit multiplexing / demultiplexing device generates a synchronous clock required for each frame multiplexing / demultiplexing device to transmit the optical transmission signal for transmission, and a synchronization clock generating means. And a synchronous clock transfer means for respectively transferring the synchronized clocks to each frame multiplexer / separator, and each frame multiplexer / separator detects the synchronized clock transferred from the bit multiplexer / separator. For reading the synchronous clock detecting means and the transmission signal group for transmission in synchronism with the individual clock of each frame multiplexing / separating device of its own, and then reading in synchronization with the synchronous clock detected by the synchronous clock detecting means. The synchronization processing means and the transmission signal group for transmission read from the synchronization processing means are synchronized with the synchronization clock. And to constitute comprises a frame multiplexing unit for sending and converted into the transmitting optical transmission signal after the frame multiplexing the bit multiplexing / demultiplexing device.

[0022]

As a result, according to the present invention, a synchronous clock is generated by the bit multiplexer / separator and is supplied to each frame multiplexer / separator, and each frame multiplexer / separator synchronizes with this synchronous clock. Then, the transmission signals for transmission are subjected to synchronization processing and frame multiplexing processing, and then sent to the bit multiplexing / demultiplexing device. That is, each frame multiplexer / demultiplexer always sends the transmission optical transmission signal in synchronization with the common synchronization clock. Therefore, even if the synchronous clock used by each frame multiplexer / separator is switched from the current one to the spare one due to a failure or the like,
The phase difference between the transmission optical transmission signals sent from the demultiplexer to the bit multiplexer / demultiplexer is always kept constant without being affected by the switching of the synchronous clock. Therefore, the memory for absorbing the phase fluctuation provided in the bit multiplexing / demultiplexing device becomes unnecessary or has a very small capacity, which reduces the power consumption of the device, increases the packing density, and delays the signal propagation. Can be reduced.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, the same parts as those in FIG. 7 are designated by the same reference numerals and detailed description thereof will be omitted. FIG. 1 shows the configuration of an optical transmission apparatus according to an embodiment of the present invention, which is different from the conventional configuration shown in FIG.
Pointer processing circuits (SA) 130 and 230 and bit multiplexing / demultiplexing device 30 in demultiplexing devices 100 and 200, respectively.
The main difference is that a timing signal generation unit (hereinafter abbreviated as TSG) 400 is added in 0 and the selector 35 is omitted.

First, the TSG 400 will be described. FIG. 2 shows a concrete configuration of the TSG 400, and the TS
The G400 includes a selector 410 and a PLL circuit 420. The selector 410 is a working synchronous clock CK in the station building.
41 and the standby synchronization clock CK42 are supplied,
One of the two synchronization clocks is selectively output to the PLL circuit 420.

The PLL circuit 420 includes a phase comparator 421,
Loop filter 422, voltage controlled crystal oscillator (hereinafter, V
A CXO) 423 and a frequency dividing circuit 424.

The phase comparator 421 is the selector 410.
Select output clock of and the divided clock described later are supplied,
A phase difference signal having a duty corresponding to the phase difference between both clocks is output to the loop filter 422. The loop filter 422 smoothes the phase difference signal,
A voltage signal proportional to the phase difference between the selected output clock and the divided clock is generated and output to the VCXO 423.

The VCXO 423 oscillates a clock having a frequency corresponding to the voltage signal, and outputs the oscillated clock to the frequency dividing circuit 424. This frequency dividing circuit 424 is
The divided clock is generated by dividing the above clock, and two divided signals, clock C, which have a dividing relation with each other are generated.
Generates K43 and CK44.

With this configuration, the TSG 400 is
The working sync clock CK41 and the backup sync clock CK42 in the station building are supplied, and of these two sync clocks,
Clocks CK43 and CK44 with one of them as a reference clock are generated. This clock CK44 is output to the phase fluctuation absorbing memories 330 and 340 as a read clock instead of the clock CK0 output from the selector 35 having the conventional configuration. Further, the clock CK43 is used for the optical transmitter (OS) 38.
It is output to 0,390.

Next, the optical transmitter 380 will be described with reference to FIG. 3 showing the configuration of the optical transmitter 380. The optical transmission unit 390 has the same configuration as the optical transmission unit 380, and therefore description thereof will be omitted.

The optical transmitter 380 is composed of an optical transmitter 381 and an optical modulator 382, and is supplied with an STM-16 signal D3 and a clock CK43, respectively. Optical transmitter 38
1 converts the STM-16 signal D3 into an optical signal and outputs it to the optical modulator 382. The optical modulator 382 uses the clock CK.
The optical signal is amplitude-modulated by 43 and output as an optical transmission signal L30, whereby the clock CK43 is transmitted while being superimposed on the optical transmission signal L30.

The reason for adopting such a configuration is that STM-1
This is because the 6 signals are as fast as 2,488.32 Mbit / s and the frequency of the clock CK43 is lower than that. That is, the optical transmitters 380 and 390 superimpose the clock CK43 on the optical transmission signals 120 and 220, respectively, and generate optical transmission signals L30 and L30.
The signal is output to the optical receivers (OR) 120 and 220 as 40.

Next, the optical receiving section 120 will be described with reference to FIG. 4 showing a specific configuration of the optical receiving section 120.
The light receiving section 220 has the same configuration as the light receiving section 120, and therefore description thereof will be omitted.

The receiving section 120 is composed of a photoelectric converter 121, an amplifier 122, a bandpass filter (hereinafter abbreviated as BPF) 123, and an identification reproduction circuit 124. The photoelectric converter 121 converts the optical transmission signal L30 into an electric signal, the amplifier 122 amplifies this electric signal, and the BPF 12
3 and the identification reproduction circuit 124.

The BPF 123 extracts the superimposed clock CK43 from the amplified electric signal. The identification / reproduction circuit 124 uses the amplified electric signal to generate the ST signal.
Reproduce M-16 signal.

That is, the optical receivers 120 and 220 reproduce the STM-16 signal from the optical transmission signals L30 and L40, respectively, and extract the superposed clock CK43 to the pointer processing circuits (SA) 130 and 230. Output.

Next, the pointer processing circuit 130 will be described with reference to FIG. 5 showing a specific configuration of the pointer processing circuit 130. Regarding the pointer processing circuit 230,
Since it has the same configuration as the pointer processing circuit 130, the description thereof will be omitted.

The pointer processing circuit 130 is the PLL circuit 1
31 and a synchronization processing circuit 132. The PLL circuit 131 is supplied with a clock CK43 as a reference clock and oscillates a clock CK43 'synchronized with the clock CK43. This clock CK43 'is used for the optical transmitter (OS) 1
10 and the synchronization processing circuit 132.

Further, the synchronization processing circuit 132 is supplied with the synchronization clock (CK11 or CK21) of the frame multiplexer / demultiplexer 100 and 16-channel STM-1 signals CH1 to CH16 synchronized with the synchronization clock. The synchronization processing circuit 132 uses the section adaptation function using the pointer processing to perform 16-channel ST
With respect to the M-1 signals CH1 to CH16, the input side operates with the above-mentioned synchronous clock, and the output side outputs them to the optical transmission section 110 in synchronization with the clock CK43 '.

That is, the pointer processing circuits 130 and 23
0 is the clock C for the STM-1 signals CH1 to CH16 of 16 channels which are synchronized with the respective synchronization clocks.
It is output to the optical transmitter 110 in synchronization with K43 '.

The optical transmitters 110 and 120 respectively frame-multiplex 16-channel STM-1 signals CH1 to CH16 using the clock CK43 ', and generate optical transmission signals L10 and CH10.
Convert to L20 and output. This optical transmission signal L10, L20
Are output to the optical receiving units (OR) 31 and 32 in the bit multiplexer / demultiplexer 300, respectively.

The optical receivers 31 and 32 convert the optical transmission signals L10 and L20, respectively, into electrical signals, and the STM-16 signal D
10 and D20 are reproduced and the clock CK45 is extracted. The STM-16 signals D10 and D20 are output to the phase fluctuation absorbing memories 330 and 340, respectively, and the clock CK45 is output.
Is input to the phase fluctuation absorbing memories 330 and 340 as a writing clock.

The phase fluctuation absorbing memories 330 and 340 are
The STM-16 signals D10 and D20 are respectively written with the clock CK45 and read with the clock CK44. That is, the phase fluctuation absorbing memories 330 and 340
Absorbs relative phase fluctuations that may occur between the STM-16 signal D10 and the STM-16 signal D20, and both of them are in synchronization with the clock CK44.
Output 0 '. The read STM-16 signal D10 ',
D20 'is output to the multiplexer (MUX) 36.

The operation of the optical transmission device having the above configuration will be described. The time division multiplex signal (2 × STM-16) having a transmission rate twice as high as that transmitted from another station is supplied to the demultiplexer 37, and the STM-16 signal D3 of two systems is supplied.
, D4. This STM-16 signal D3, D4
In the optical transmitters 380 and 390, respectively,
The clock CK43 generated in G400 is superimposed and output as optical transmission signals L30 and L40, respectively.

The optical transmission signals L30 and L40 are divided into 16-channel STM-1 signals CH1 to CH16 by the frame multiplexer / demultiplexers 100 and 200, respectively, and the superimposed clock CK43 is extracted.

On the other hand, the STM-16 signal to be transmitted, 2
16 channels of STM-1 signals CH1 to CH16
Respectively perform frame multiplexing using the clock CK43 in the frame multiplexer / demultiplexers 100 and 200,
It is converted into optical transmission signals L10 and L20. This optical transmission signal L
The optical receivers 31 and 32 convert the signals 10 and L20 into electric signals to reproduce the STM-16 signals D10 and D20.

The STM-16 signals D10 and D20 are written into the phase fluctuation absorbing memories 330 and 340, respectively, at the clock CK45, and both are read at the clock CK44, thereby absorbing the phase difference between the two signals. The STM-16 signals D10 'and D20' are output in synchronization with each other.

The STM-16 signal D10 'and the STM-16 signal D20' are time-division-multiplexed by the multiplexer 36 to form a time-division multiplexed signal (2.times.STM-16) having a double transmission rate. Sent to other stations.

That is, in the optical transmission device having the above configuration, two sets of 16 channels supplied to the frame multiplexer / demultiplexer using the clock CK43 generated using the synchronous clock on the bit multiplexer / demultiplexer 300 side as the reference clock. The STM-1 signals CH1 to CH16 are subjected to frame multiplexing for optical transmission. Further, by using the clock CK44 having a frequency division relationship with the clock CK43, the STM-16 signals D10 'and D2 are output from the phase fluctuation absorbing memories 330 and 340.
0'is being read.

Therefore, if the optical transmission device having the above-mentioned configuration is used, the optical transmission signals L10 and L20 are subject to phase fluctuations which may occur when the synchronous clocks CK11 and CK12 and CK21 and CK22 of the frame multiplexer / demultiplexers 100 and 200 are switched. Not affected by.

On the other hand, regarding the phase fluctuation that may occur when switching between the working synchronous clock CK41 and the spare synchronous clock CK42 on the side of the bit multiplexer / demultiplexer 300, PL
By making settings as described below between the L circuits 420 and 131, the phase fluctuation absorbing memories 330 and 34 are
It does not affect the phase relationship between 0 input and output clocks.

The above setting will be described with reference to FIG. FIG. 6 is a diagram showing a part of the configuration of the above embodiment, and the frame multiplexer / demultiplexer 200 is omitted because it is completely the same.

Working synchronous clock C by selector 410
The clock CK4 of the phase variation absorption memory 330 is switched by the switching operation between K41 and the standby synchronization clock CK42.
It is expected that there will be a phase difference between 5 and CK44. This phase difference occurs when the PLL circuit 131 follows the output clock of the PLL circuit 420 whose phase changes.

However, the time response characteristic of the PLL circuit 420 is set to a low speed, whereby the phase change between the working synchronization clock CK41 and the standby synchronization clock CK42 is gently absorbed, and compared with the PLL circuit 420. The time response characteristic of the PLL circuit 131 is set at high speed. With such a configuration, the PLL circuit 131 responds quickly to the output clock of the PLL circuit 420 whose phase changes without delay, so that the phase difference that may occur between the clocks CK45 and CK44 of the phase fluctuation absorbing memory 330. Can be kept to a minimum.

For this reason, the size of the phase fluctuation absorption memories 330 and 340, which has been a problem in the past, may be zero in principle, but it may be caused by imperfections in the circuit or relative differences in transmission line delay. Considering the phase difference, the phase variation absorption memory 33
Even if 0, 340 is used, a required memory size of several tens ns (nanosecond) is sufficient.

Therefore, the memory size can be reduced as compared with the conventional memory size, and it can contribute to the reduction of the power consumption of the device, the high-density mounting, and the reduction of the propagation delay of the signal inside the device. The present invention is not limited to the above embodiment. For example, in the above embodiment, the pointer processing circuits 130 and 230 have operation clocks (CK11, CK21, CK12, CK22).
To supply clocks other than the optical transmitters 380, 3
Although the clock CK43 is superimposed on the STM-16 signal at 90, if the clock is extracted from the STM-16 signal received by the optical receivers 120 and 220 and used by the pointer processing circuits 130 and 230, the above superposition is performed. Is not always necessary.

Further, in the above embodiment, two sets of STM-1 are used.
Although the case where 6 signals are bit-multiplexed has been shown, the present invention is also applicable to the case where two or more sets of STM-16 signals are bit-multiplexed to obtain a transmission signal having a transmission rate twice or more.

Needless to say, various modifications may be made without departing from the gist of superimposing and transmitting low-frequency clocks and then separating them.

[0058]

As described above, according to the present invention,
An optical transmission device capable of reliably performing bit multiplexing processing without using a large-capacity phase fluctuation absorption memory, which can reduce power consumption, increase packaging density, and reduce signal propagation delay. Can be provided.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a configuration of an embodiment of an optical transmission device according to the present invention.

FIG. 2 is a block circuit diagram showing a configuration of a timing signal generation unit of the optical transmission device according to the present invention.

FIG. 3 is a block circuit diagram showing a configuration of an optical transmitter of the optical transmission device according to the present invention.

FIG. 4 is a block circuit diagram showing a configuration of an optical receiving section of the optical transmission device according to the present invention.

FIG. 5 is a block circuit diagram showing a configuration of a pointer processing circuit of the optical transmission device according to the present invention.

FIG. 6 is a conceptual diagram illustrating a phase variation that may occur in the optical transmission device according to the present invention.

FIG. 7 is a diagram showing a configuration of a conventional optical transmission device.

[Explanation of Codes] 1, 2 ... Frame Multiplexing / Demultiplexing Device, 3 ... Bit Multiplexing / Demultiplexing Device, 11, 21 ... Optical Transmitter (OS), 12, 22 ...
Optical receiver (OR), 31, 32 ... Optical receiver (OR), 3
3, 34 ... Phase fluctuation absorption memory, 35 ... Selector, 3
6 ... Multiplexer (MUX), 37 ... Demultiplexer (DMUX), 38, 39 ... Optical transmitter (OS), 10
0, 200 ... Frame multiplexing / demultiplexing device, 300 ... Bit multiplexing / demultiplexing device, 110, 210 ... Optical transmission unit (OS),
120, 220 ... Optical receiver (OR), 121 ... Photoelectric converter, 122 ... Amplifier, 123 ... Bandpass filter (B
PF), 124 ... Identification reproduction circuit, 130, 230 ... Pointer processing circuit (SA), 131 ... PLL circuit, 132 ...
Synchronization processing circuit, 330, 340 ... Phase fluctuation absorption memory, 380, 390 ... Optical transmission unit (OS), 381 ... Optical transmitter, 382 ... Optical modulator, 400 ... Timing signal generation unit (TSG), 410 ... Selector, 420 ... PLL circuit, 421 ... Phase comparator, 422 ... Loop filter, 4
23 ... Voltage controlled crystal oscillator (VCXO), 424 ... Dividing circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04J 3/06 A

Claims (4)

[Claims] 1. Each of the transmission signal groups for transmission is frame-multiplexed, converted into an optical transmission signal for transmission and transmitted, and an optical transmission signal for reception having the same format as the optical transmission signal for transmission is transmitted to the transmission signal for transmission. A plurality of frame demultiplexing / demultiplexing devices having a function of demultiplexing and outputting to a group of receiving transmission signals of the same format as that of the group, and for synchronizing the plurality of optical transmission signals for transmission and then performing time division multiplexing for transmission A bit-multiplexed signal is generated, and a reception bit-multiplexed signal having the same format as the transmission bit-multiplexed signal is time-division-separated into a plurality of the reception optical transmission signals having the same format as the transmission optical transmission signal, and each of the frames is An optical transmission device comprising a bit multiplexer / demultiplexer having a function of sending to a multiplexer / demultiplexer, wherein the bit multiplexer / demultiplexer is Synchronous clock generating means for generating a synchronous clock necessary for the frame multiplexing / separating device to send out the optical transmission signal for transmission, and the synchronous clock generated by this synchronous clock generating means for each frame multiplexing / separating device. Synchronous clock transfer means for respectively transferring to the device, and each of the frame multiplexing / separating devices, synchronous clock detecting means for detecting the synchronous clock transferred from the bit multiplexing / separating device, Synchronization processing means for reading the transmission signal group for transmission in synchronism with an individual clock of each frame multiplexing / separating device of its own, and then reading in synchronism with the synchronization clock detected by the synchronization clock detecting means; The transmission signal group for transmission read out from the synchronization processing means is synchronized with the synchronization clock, and the frame number is increased. The optical transmission device according to claim converted into the transmitting optical transmission signal After that a frame multiplexing means for delivering to the bit multiplexing / demultiplexing device. 2. The synchronous clock transfer means superimposes and transfers the synchronous clock generated by the synchronous clock generation means on the reception optical transmission signal, and the synchronous clock detection means comprises the bit multiplexer / demultiplexer. The optical transmission device according to claim 1, wherein the synchronous clock is extracted from a reception optical transmission signal transmitted from the optical transmission device. 3. The synchronous clock transfer means transfers the synchronous clock generated by the synchronous clock generating means by amplitude-modulating the reception optical transmission signal by the clock. Optical transmission equipment. 4. The synchronous clock generating means selectively selects a working reference clock and a spare reference clock,
Based on the selected reference clock, a first PLL circuit having a predetermined time response characteristic is used to generate a synchronous clock, and the synchronous clock detecting means detects the synchronous clock transferred from the bit multiplexer / separator. Based on the first
A second PLL circuit having a time response characteristic having a higher speed than the time response characteristic of the second PLL circuit, and a synchronous clock is detected and supplied to the synchronization processing means and the frame multiplex transmission means. Item 2. The optical transmission device according to item 1.