JP2002135223A - Demultiplex transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a demultiplex transmission system which simplifies its constitution and makes effective the frame transmission. SOLUTION: The demultiplex transmission system has a separator and a multiplexer. The separator divides a communication frame, including an overhead having n (n>=2) small overheads which include synchronizing information and information data into n small communication frames, based on the length of the small overhead. The small communication frames are transmitted over n predetermined transmission lines, corresponding to the sequence of the synchronizing information to the multiplexer. The multiplexer multiplexes the n small communication frames, based on the synchronizing information in each small communication frame and on the sequence of the synchronizing information and corresponding relation of the transmission lines to this sequence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverse multiplex transmission system (Inverse MUX) that bundles a plurality of transmission lines and uses them virtually as one thick transmission line.

[0002]

2. Description of the Related Art ITU-T (international telecommunications)
on Union-Telecommunication Sector)
(Synchronous Digital Hierarchy), the STM (Synchronous Transport Modul
e) Specify the frame. The STM frame has a nested configuration in which a high-speed frame includes a plurality of low-speed frames.

In a transmission system using this STM frame, a high-speed frame having a relatively high transmission speed is separated into a plurality of low-speed frames having a lower transmission speed and transmitted, and the transmitted low-speed frames are multiplexed. There is a demand for an inverse multiplex transmission system that reproduces original high-speed frames. For example, when applying this STM frame to an access system or a short-distance transmission system, since high-speed interface components capable of high-speed, large-capacity serial transmission are expensive, demultiplexing transmission that can transmit STM frames with cheap components is used. Application of the system is desired. In addition, when applying STM frames to long-distance transmission systems, high-speed, large-capacity serial transmission has limitations on the transmission distance due to the characteristics of optical fibers, and propagation loss is small and low-speed transmission is possible for relatively long-distance transmission. There is a demand for an inverse multiplex transmission system as a large-capacity bulk transmission system using a transmission path.

In this demultiplexing transmission system, when a high-speed frame is separated into a plurality of low-speed frames, the demultiplexer assigns a label indicating the relationship between the low-speed frame to the original high-speed frame and a label indicating the relationship between the low-speed frames. Give. The multiplexing device on the receiving side reproduces the high-speed frame in accordance with these labels attached to the low-speed frame.
Thereby, even if the receiving order of the low-speed frames by the multiplexing device on the receiving side is different from the transmitting order of the low-speed frames from the demultiplexing device, the multiplexing device faithfully converts the high-speed frames using the received low-speed frames. Can be played.

[0005]

However, since it is complicated to add a label to each low-speed frame and reproduce a high-speed frame from a plurality of low-speed frames based on the label, an apparatus for adding a label and decoding the label is used. And the entire system becomes extremely complicated, and it takes a lot of time to generate a low-speed frame and reproduce a high-speed frame. As a result, the efficiency of frame transmission deteriorates. .

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an information processing system that includes synchronization information such as an STM frame used in SDH recommended by the ITU-T.
It is based on the basic idea of using an existing frame structure comprising an overhead having (n ≧ 2) small overheads and each communication frame containing information data following the overhead.

[0007] In the demultiplexing transmission system according to the present invention, n (n ≧ n) each including synchronization information for synchronizing each other.
2) In order to obtain a small communication frame, which is simultaneously output from a communication frame containing information overhead following the overhead having the small overhead and the data data, the communication frame is divided into n based on the length of the small overhead. A separation device that divides the small communication frame into a plurality of small communication frames, and n transmission paths for transmitting the small communication frames corresponding to the synchronization information, each of which is predetermined in accordance with the arrangement of the synchronization information, In order to restore the communication frame from the n small communication frames, the synchronization information of the small overhead in each of the small communication frames received via the n transmission paths, an array of the synchronization information, and A multiplexing device for multiplexing the n small communication frames based on the correspondence of the transmission paths corresponding to the arrangement.

[0008] In the demultiplexing transmission system according to the present invention, the demultiplexing device generates a communication frame having n small overheads including synchronization information for synchronizing each other with n number of communication frames based on the length of the small overhead. It is divided into small communication frames and transmitted to the multiplexing device simultaneously via n predetermined transmission paths corresponding to the arrangement of the synchronization information. The multiplexing device may further include: the synchronization information of the small overhead in the overhead in each of the small communication frames received via the n transmission paths; an array of the synchronization information; and a transmission corresponding to the array. The small communication frame is multiplexed on the basis of the correspondence with the road.

According to the demultiplex transmission system of the present invention, as described above, the synchronization information of the small overhead is provided in each small communication frame, and the arrangement of the synchronization information and the transmission corresponding to the arrangement are performed. Since the correspondence between the frames is determined in advance, the multiplexing device operates according to the correspondence between the arrangement of the synchronization information and the transmission lines corresponding to the arrangement, thereby providing the correspondence between the frames as in the related art. The communication frame can be reproduced by the synchronization information without adding a label for clarifying the communication frame.
In addition, the separation device divides the communication frame into n small communication frames based on the length of the small overhead, so that the processing for division is simplified and the communication frame can be appropriately adapted to each transmission path. Therefore, the multiplexing device can multiplex the small communication frames based on the above-mentioned fixed division unit of each small communication frame.

[0010]

FIG. 1 shows the configuration of an inverse multiplex transmission system according to the present invention. This inverse multiplex transmission system 1
As shown in FIG. 1, a high-speed frame output from a preceding device (not shown) and includes four low-speed frames, for example, an STM defined in SDH of ITU-T.
-4 frames, eg, STM-1
6 from the working optical signal RS including the low speed frame 50 for transmission.
A transmitting-side demultiplexer 10 that generates optical signals λ1 to λ4 including A to 50D and transmits the generated optical signals to a multiplexing device 20 on the receiving side, and a low-speed transmission frame included in the optical signals λ1 to λ4 received from the demultiplexer 10 High-speed frame 40 from 50A to 50D
A multiplexing device 20 for reproducing the working optical signal RS including the above, and the demultiplexing device 10 and the multiplexing device 20 are point-to-
Point, that is, a transmission system 30 having five transmission paths for directly connecting one-to-one with each other.
This demultiplexing transmission system 1 also includes optical signals λ1 to λ4
When a failure occurs in the path of the optical signals λ1 to λ5 by using the spare optical signal λ5, the frame to be transmitted on the failed path is transmitted by using the spare optical signal λ5. Rescue transmission from failure.

FIG. 2 shows a high-speed frame. As shown in FIG. 2A, the high-speed frame 40 shown in FIG.
And a payload 42 which is information data following the overhead. The overhead 41 is composed of four small overheads “A1” 43-1 to 43-4 for synchronizing the four transmission low-speed frames 50A to 50D and four small overheads “A2” 43- following them. 5
To 43-8. These small overheads 4
3-1 to 43-8 also function to establish frame synchronization of the high-speed frame 40 itself as a whole. In addition,
In this example, the length of each of the small overheads 43-1 to 43-8 is 1 byte.

On the other hand, the payload 42 includes the above-described four low-speed frames 44A to 44D in this order, and each of the low-speed frames 44A to 44D has a length of an integral multiple of the length of the small overhead 43, that is, 1 byte. Has a length that is an integral multiple of Accordingly, the payload 42 also has a length that is an integral multiple of the length of the small overhead 43, that is, a length that is an integral multiple of 1 byte.

FIG. 2B shows that the payload 42 has a length similar to the length of the small overhead 43, that is, a plurality of data "D1 to Dm" 47-1 to 47 having a length of 1 byte.
-M indicates a virtual configuration. As will be described later, the virtual data “D1 to Dm” 47-1 to 47-m are transmitted to the high-speed frame 40 when the low-speed transmission frame 50 is generated from the high-speed frame 40 by the separation unit 13 of the separation device 10. And a combining unit when the high-speed frame 40 is generated from the low-speed transmission frame 50 by the multiplexing unit 26 of the multiplexing device 20.

Referring again to FIG. 2A, each of the low-speed frames 44A to 44D in the above-described payload 42 includes an overhead 45 and a payload 46, respectively. The overhead 45 includes management information on the payload 46. The payload 46 includes data representing information to be transmitted from the demultiplexer 10 to the multiplexer 20.

FIG. 3 shows a low-speed frame for transmission. FIG.
As shown in FIG. 3, each of the low-speed transmission frames 50A to 50D is composed of a synchronization flag 51 and a payload 52. Synchronization flag 51
Is composed of the small overheads “A1” and “A2” 43 of the high-speed frame 40 shown in FIG. 1, and the payload 52 has the data “D1” to “D” shown in FIG.
m ”. More specifically, for example, the synchronization flag 51 of the transmission low-speed frame 50A is
The transmission low-speed frame 50 includes the small overhead “A1” 43-1 and “A2” 43-5 shown in FIG.
The payload 52 of A is the data “D” shown in FIG.
1 "47-1," D5 "47-5, and" D9 "47-
9 and so on.

Returning to FIG. 1, the separation device 10 is similar to that shown in FIG.
O / E unit 11 for converting the working optical signal RS including the high-speed frame 40 into an electric signal, and a synchronization unit for establishing frame synchronization of the high-speed frame 40 constituted by the electric signal obtained by the O / E unit. 12 and a separating unit that generates four transmission low-speed frames 50A to 50D by separating the high-speed frame 40 synchronized by the synchronization unit for each length of the small overhead 43, that is, for each byte. 1
3, four transmission low-speed frames 50A to 50D generated by the separation unit, and a spare frame 5 described later.
A switching unit 14 that switches a total of five frames of 0E under control of a control unit 15 described later, and a control unit 15 that controls switching by the switching unit. Further, the demultiplexer 10 converts five of the low-speed transmission frames 50A to 50D and the spare frame 50E switched by the switching unit 14 from electric signals to corresponding optical signals λ1 to λ5. O section 16 and the E /
The five optical signals obtained by the O unit 16 are wavelength-multiplexed,
The O / E unit 11 and the synchronization unit 12 for the wavelength multiplexing unit 17 for transmitting to the multiplexing device 20 via the transmission system 30 and the backup optical signal PS for relieving the working optical signal RS from the failure.
O / E circuit 18a and synchronization circuit 18 functioning similarly to
b.

The multiplexing device 20 includes a wavelength demultiplexing unit 21 that demultiplexes the five multiplexed optical signals received from the demultiplexing device 10, and converts the five optical signals demultiplexed by the wavelength demultiplexing unit into electric signals. An O / E unit 22 for conversion;
Frame 50 for transmission of electrical signals obtained by the unit
And a switching unit 2 for switching the low-speed transmission frame 50 under the control of the control unit.
4, an adjusting unit 25 for adjusting the delay difference between the low-speed transmission frames 50, and a multiplexing unit 26 for synchronizing the low-speed transmission frames 50 and reproducing the high-speed frame 40 described above.
A synchronization unit 27 for establishing frame synchronization of the high-speed frame 40 generated by the multiplexing unit 26; and a high-speed frame 40 of the electric signal synchronized by the synchronization unit.
To an optical signal, an E / O unit 28 for converting the
And a spare unit 29 having a synchronizing circuit 29a and an E / O unit 29b that function similarly to the synchronizing unit 27 and the E / O unit 28.

The transmission system 30 is composed of, for example, an optical fiber, and includes five transmission lines as described above. Each transmission path is provided corresponding to the arrangement of the small overhead 43 of the high-speed frame 40 in FIG. 2A so as to transmit the optical signals λ1 to λ5. More specifically, for example, the transmission path for transmitting the optical signal λ1 is the high-speed frame 4 shown in FIG.
0 small overhead “A1” 43-1 and “A2” 43
-5 is provided. The optical signal λ5 is
Use a transmission path for the spare signal.

The operation of the specific example of the inverse multiplex transmission system 1 will be described. The working optical signal R including the high-speed frame 40 shown in FIG. 2A output from the preceding device (not shown)
S is input to the O / E unit 11. The working optical signal RS is
The O / E unit 11 converts the electric signal into a high-speed frame 40. When converted into an electric signal by the O / E unit 11, the high-speed frame 40 is output to the synchronization unit 12. The high-speed frame 40 establishes frame synchronization based on the overhead 41 shown in FIG.

The separation unit 13 receives the input high-speed frame 4
0 for each length of the small overhead 43 and the small overhead 4
3, that is, by distributing them to each of the four transmission lines except for the backup transmission line of the transmission system 30 in a predetermined order, the four transmission low-speed frames 50A to 50D shown in FIG. Generate Specifically, the separation unit 13 distributes the first small overhead “A1” 43-1 of the high-speed frame 40 as a part of the synchronization flag 51 of the low-speed frame 50A for transmission, and distributes the next small overhead “A1” 43-1. -2 is distributed as part of the synchronization flag 51 of the transmission low-speed frame 50B, and the next small overhead "A1" 43-3 is distributed as part of the synchronization flag 51 of the transmission low-speed frame 50C. The small overhead "A1" 43-3 is distributed as a part of the synchronization flag 51 of the transmission low-speed frame 50D.

In this way, when the small overheads "A1" 43-1 to 43-4 are allocated to the four low-speed transmission frames 50A to 50D excluding the standby frame,
The separation unit 13 further transmits the small overhead “A2” 43-5 following the high-speed frame 40 to the low-speed frame 50A for transmission.
The small overhead “A” in the synchronization flag 51
1 "43-1 and the next small overhead" A
2 "43-6 is distributed after the small overhead" A1 "43-2 in the synchronization flag 51 of the low-speed transmission frame 50B, and the next small overhead" A2 "43-7 is distributed to the low-speed transmission frame 50C. It is distributed after the small overhead "A1" 43-3 in the synchronization flag 51, and the last small overhead "A2" 43-8 is divided into the small overhead "A1" in the synchronization flag 51 of the low-speed transmission frame 50D. "Distribute after 43-4. In this way,
The separation unit 13 creates the synchronization flag 51 for each of the low-speed transmission frames 50A to 50D.

When the creation of the synchronization flag 51 of the low-speed transmission frames 50A to 50D is completed, the separation unit 13 continues.
Separates the payload 42 of the high-speed frame 40 in units of the length of the small overhead 43, that is, for each of the four transmission paths for each virtual data shown in FIG. 2B. Specifically, the separation unit 13 distributes the data “D1” 47-1 of the first byte of the payload 42 as the head of the payload 52 of the low-speed transmission frame 50A, and distributes the data “D1” 47-1 following the data “D1” 47-1. The data “D2” 47-2 in the byte is distributed as the head of the payload 52 of the low-speed transmission frame 50B, and the data “D2” 47-2 is distributed.
The third byte data "D3" 47-3 following 47-2 is distributed as the beginning of the payload 52 of the transmission low-speed frame 50C, and the fourth byte data "D4" 47- following data "D3" 47-3. 4 is distributed as the head of the payload 52 of the transmission low-speed frame 50D.

The separation unit 13 further outputs data “D4” 4
The fifth byte data “D5” 47-5 following 7-4 is distributed after the data “D1” 47-1 in the payload 52 of the low-speed transmission frame 50A, and the data “D5” 47-
The data "D6" 47-6 of the sixth byte following "5" is transferred to the data "D2" of the payload 52 of the transmission low-speed frame 50B.
Distribute after 47-2. Thereafter, the demultiplexing unit 13 repeats the same distribution to transmit the low-speed frames 50A to 50A for transmission.
Complete 0D. 4 low-speed frames for transmission 50A-5
0D are created, the low-speed frames 50
A to 50D are supplied to the switching unit 14.

On the other hand, the protection optical signal PS is also used as the current optical signal RS.
Similarly to the above, after being converted into an electric signal by the protection unit 18 and establishing frame synchronization, a protection frame 50E is generated and supplied to the switching unit 14.

The switching unit 14 controls the four transmission low-speed frames 50A to 50D from the separation unit 13 and the protection frame 50E from the protection unit 18 according to the frame transmission state, that is, the quality of the frame transmission. Switching is performed under the control of the unit 15. More specifically, the control unit 15
Is a line system (hereinafter, referred to as "downlink system") in the direction opposite to the transmission direction of the line system (hereinafter, referred to as "uplink system") including the demultiplexer 10 and the multiplexing device 20, that is, multiplexing. Of an uplink system obtained from a downlink system composed of a demultiplexer (not shown) provided at a station where the demultiplexer 20 is installed and a multiplexer (not shown) provided at a station where the demultiplexer 10 is installed. Based on the information on the state, the quality of the transmission quality of the four transmission low-speed frames 50A to 50D is determined. When any one of the four transmission low-speed frames 50A to 50D is defective, the control unit 15 does not use the defective transmission low-speed frame but uses the spare frame 50E instead. For example, when the transmission state of the transmission low-speed frame 50A is bad, the information to be transmitted included in the transmission low-speed frame 50A is:
It is transmitted using the spare frame 50E.

When the switching unit 14 performs frame switching according to the transmission state of the frame, the E / O unit 16 determines which of the low-speed transmission frames 50A to 50D and the spare frame 50E has been selected by the switching unit 14. Four optical signals among the optical signals λ1 to λ5 included and corresponding to each frame are generated, and the generated optical signals are output to the wavelength multiplexing unit 17. The generated optical signal is wavelength-multiplexed by the wavelength multiplexing unit 17. The wavelength-multiplexed optical signals are simultaneously transmitted in parallel to the multiplexer 20 via the transmission paths of the transmission system 30. For example, the transmission low-speed frame 50A is transmitted to the multiplexing device 2 via a transmission line for transmitting the corresponding optical signal λ1.
Sent to 0. The transmission low-speed frames 50A to 50A
It is assumed that optical signals λ1 to λ4 corresponding to 0D are multiplexed and transmitted.

When the optical signals λ1 to λ4 are transmitted to the multiplexing device 20 in parallel and simultaneously, the optical signals λ1 to λ4 are demultiplexed into the optical signals λ1 to λ4 by the wavelength demultiplexing unit 21. / E section 22. The separated optical signals λ1 to λ4 are converted by the O / E unit 22 into electric signal transmission low-speed frames 50A to 50D, respectively, and the transmission low-speed frames 50A to 50D are output to the control unit 23. In the control unit 23, the transmission low-speed frames 50A to 50D are subjected to processing for frame switching, for example, calculation of a BER (Bit Error Rate), and error detection / correction.

After the processing for frame switching is performed by the control unit 23, the transmission low-speed frames 50A to 50D are switched by the switching unit 24 to frame switching corresponding to the frame switching of the switching unit 14 in the separation device 10. receive. After receiving the frame switching by the switching unit 24, the transmission low-speed frames 50A to 50A
D, the adjusting unit 25 adjusts the delay difference between the low-speed transmission frames 50A to 50D based on the synchronization flag 51 of FIG. 2A, whereby the frames 50A to 50D are adjusted.
Undergo mutual phase alignment.

After the phase adjustment by the adjustment unit 25 is completed, the low-speed transmission frames 50A to 50D are output to the multiplexing unit 26. The multiplexing unit 26 determines whether the frames 50A to 50A
After synchronizing 0D with each other based on the synchronization flag 51 shown in FIG. 2A, the length of the small overhead 43 shown in FIG. The high-speed frames 40 are reproduced by extracting the frames in a predetermined order.

More specifically, the multiplexing unit 26 first extracts the small overhead “A1” 43-1 which is the first byte of the transmission low-speed frame 50A, and then extracts the first byte of the transmission low-speed frame 50B. Small overhead "A1"
43-2 to extract the small overhead "A1"
1 and then extract the small overhead "A1" 43-3, which is the first byte of the transmission low-speed frame 50C, and arrange it after the small overhead "A1" 43-2. The small overhead “A1” 43-4 which is the first byte of 50D is extracted and arranged after the small overhead “A1” 43-3.

The multiplexing unit 26 outputs a low-speed frame 50 for transmission.
When the extraction of the small overhead “A1”, which is the first byte of the synchronization flag 51 of A to 50D, is completed, the small overhead “A2” 43-5 which is the second byte of the low-speed transmission frames 50A to 50D is next. ~ 43-8 are processed. That is, the multiplexing unit 26 sets the small overhead “A2” 43 that is the second byte of the transmission low-speed frame 50A.
-5 is extracted and 2 of the transmission low-speed frame 50D described above is extracted.
The small overhead "A1" 43-4, which is the second byte of the low-speed transmission frame 50B, is extracted after the small overhead "A1" 43-4, which is the byte, and the small overhead "A2" 43- is extracted. After that, the overhead 41 of the high-speed frame 40 shown in FIG. 2A is reproduced by repeating the same extraction and alignment.

The multiplexing unit 26 further transmits data "D1" 47-1 which is the third byte of the transmission low-speed frame 50A.
And arranged after the small overhead “A2” 43-8, which is the second byte of the low-speed transmission frame 50D, and then extract the third byte of data “D2” 47-2 of the low-speed transmission frame 50B. The data "D1" 4
Arrange after 7-1. By repeating such extraction and alignment, the payload 42 of the high-speed frame 40 shown in FIG. 2A is created, and as a result, the reproduction of the high-speed frame 40 shown in FIG. 2A is completed.

The high-speed frame 4 reproduced by the multiplexing unit 26
0 is output to the synchronization unit 27. In the synchronizing unit 27, the high-speed frame 40 transmits the E
It is output to the / O unit 28. In the E / O unit 28, an optical signal RS including the high-speed frame 40 is generated and output to a subsequent device.

In the specific example of the inverse multiplex transmission system, as described above, the demultiplexer 10 converts the high-speed frame 40 into the overhead 41 of the high-speed frame 40 and the length of the small overhead 43 which functions to establish synchronization. By separating the small overhead 43 into the synchronization flag 5
1 are generated as transmission low-speed frames 50A to 50D, and then transmitted to the multiplexing apparatus 2 via the transmission paths of the transmission system 30 ordered according to the arrangement of the small overheads 43.
Send to 0. Upon receiving the transmission low-speed frames 50A to 50D, the multiplexing device 20 establishes synchronization between the frames based on the synchronization flag 51 of the frames 50A to 50D, and then transmits the small overhead from each of the frames 50A to 50D. The high-speed frame 40 described above is reproduced by extracting the small overhead 43 and the data 47 in units of length 43 and in the order of the transmission paths and arranging them continuously. Therefore, it is not necessary to perform a complicated process of adding a complicated label indicating the relationship between the original high-speed frame and the relationship between the low-speed frames to each low-speed frame and reproducing the frame based on the label as in the related art. This makes it possible to make frame transmission more efficient than in the past.

As described above, the present invention relates to ITU-
Although an example using an STM frame used in SDH recommended by T has been described, the present invention is not limited to this, and the present invention can be applied to frames of various communication standards.

[0036]

According to the demultiplexing transmission system according to the present invention, as described above, the multiplexing device is operated in accordance with a predetermined arrangement of the synchronization information and a transmission line corresponding to the arrangement. Thereby, the communication frame can be reproduced by the synchronization information without giving a label for clarifying the correspondence between the frames as in the related art, and the separation device can The process for simplifying and distributing small communication frames of equal length corresponding to each transmission path without excess or deficiency, and the multiplexing device, based on the above-mentioned fixed division unit of each small communication frame, The small communication frame can be multiplexed. Therefore, the configuration of the demultiplexing device and the multiplexing device can be simplified as compared with the related art, and the time for generating a small communication frame in the demultiplexing device and reproducing the communication frame in the multiplexing device can be reduced. As a result, frame transmission can be made more efficient.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a specific example of an inverse multiplex transmission system.

FIG. 2 is a diagram showing a high-speed frame.

FIG. 3 is a diagram showing a low-speed frame for transmission.

[Explanation of symbols]

 Reference Signs List 10 separation device 11, 22 O / E unit 12, 27 synchronization unit 13 separation unit 14, 24 switching unit 15, 23 control unit 16, 28 E / O unit 17 wavelength multiplexing unit 18, 29 preliminary unit 20 multiplexing device 21 Wavelength separation unit 25 adjustment unit 26 multiplexing unit 30 transmission system

Continued on the front page F term (reference) 5K028 AA06 AA11 KK01 KK03 MM05 MM16 NN01 5K047 AA15 BB04 CC02 HH01 HH54 LL06 MM12

Claims (4)

[Claims] An overhead having n (n ≧ 2) small overheads each including synchronization information for synchronizing each other and a communication frame including information data following the overheads are simultaneously output from each other. A separating device that divides the communication frame into n small communication frames based on the length of the small overhead in order to obtain a small communication frame, each of which is predetermined in accordance with the arrangement of the synchronization information; N transmission paths for transmitting each of the small communication frames corresponding to the synchronization information, and receiving through the n transmission paths to restore the communication frame from the n small communication frames. The synchronization information of the small overhead in each small communication frame;
A multiplexing device for multiplexing the n small communication frames based on an array of the synchronization information and a correspondence relationship of the transmission line corresponding to the array. 2. The apparatus according to claim 1, wherein the separating device sequentially obtains the n small communication frames by sequentially allocating the communication frames in correspondence with the transmission paths for each length of the small overhead. Item 7. An inverse multiplex transmission system according to Item 1. 3. The demultiplexing transmission system according to claim 1, wherein the demultiplexing device and the multiplexing device are connected to each other in pairs. 4. The inverse multiplex transmission system according to claim 1, wherein each of the small communication frames of the communication frame is transmitted in parallel via each of the transmission paths.