JPH0161269B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of transmitting optical data between two stations connected by an optical transmission line by applying an optical wavelength division multiplexing method.

Conventionally, optical transmitter/receivers used in this type of optical transmission system are electrically connected, as shown in the example in FIG.
optical converter 1, optical filter 2, optical-electrical converter 3,
It is composed of a synchronous output circuit 4 and an error detector 5. It is also connected to an optical transmitting/receiving device of the other station via an optical fiber cable 6. The code applied to this optical transmission system is the nBIC code,
Here, we will explain using 8BIC code as an example. In this example, as shown in Figure 2, one block consists of nine codes (8 of which are information bits), and if the seventh code is M, then the complementary code for M is is inserted as M′ at the 9th position.

In the above device, a plurality of transmission signals A are converted into respective optical wavelengths by an electric-to-optical converter 1, multiplexed by an optical filter 2, and then sent to an optical transmission line 6.
sent to. Further, the optical signal train sent from the other station is demultiplexed by the optical filter 2, converted into an electrical signal train by the optical-to-electrical converter 3, and then the received signal B
is obtained from the synchronous output circuit 4 as follows. Further, errors in the received signal are detected by an error detector 5. However, according to such conventional technology, the other station,
Alternatively, if a failure occurs in the optical transmission line 6, the received optical signal cannot be obtained, and the leakage light from the optical filter 2 of the optical signal train sent from the own station is emphasized, and the optical-to-electrical converter 3 It comes around.
Since this signal has the same code structure as the signal transmitted from the other station, the error detector 5 has to monitor the leakage signal of the own station, and cannot detect the signal input interruption of the received signal from the other station. It has the disadvantage of In addition, in a one-way transmission system, even if one of the optically multiplexed signals sent from the other station is disconnected, the channel that was receiving that signal is not connected to the optical filter. Needless to say, the same problem can occur due to leakage from other channels.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide an optical wavelength division multiplexing method that can accurately detect the state when the receiving optical wavelength input is cut off due to an abnormality in the other station. The objective is to provide an applied optical transmission system.

According to the present invention, for each block, N information bits and a complementary code for the m-th (mN) information bit are appended to the two sides connected by an optical transmission line, and the optical information is transmitted. In the method of transmitting optical data using wavelength multiplexing, on the transmitting side,
means for encoding optical signals with different wavelengths by changing the order of the m-th bit corresponding to the information bit; and means for optically wavelength multiplexing these encoded optical signals and transmitting the optical signals. on the receiving side, means for separating the optical wavelength multiplexed signal received via the transmission line into respective optical wavelengths, and optical-to-electrical conversion for each optical signal separated by the separating means. , means for detecting a signal for each block encoded with a different order of the m-th bit, and receiving the outputs of these signal detecting means, respectively;
Means for detecting code errors from the m-th bit of a different order of the information bits and complementary code bits thereof, respectively, and detecting the presence or absence of an error in the received code by these code error detection means. As a result, an optical transmission system is obtained which is characterized in that only corresponding information bits on the transmitting side are selectively received.

Next, an embodiment of the optical transmission system according to the present invention will be described with reference to the drawings.

FIG. 3 shows a configuration block diagram of an embodiment according to the present invention. Note that this example shows the configuration of the optical transmitting/receiving device of one station when a bidirectional optical wavelength multiplexing method is applied, and it is assumed that the device of the other station has the same configuration. In this figure, the transmitting section is composed of a block signal generator 10 and an electro-optical converter 11. Of these, the block signal generator 10 has a control circuit 10
-1, memory 10-2, complementary code generation circuit 10-3
and a complementary code addition circuit 10-4 are built-in. On the other hand, the receiving section includes an optical-to-electrical converter 13, a synchronous output circuit 14, and an error detector 15. Each element of the transmitting section and the receiving section has a function corresponding to a plurality of channels as indicated by the symbol . The optical filters 12 perform optical wavelength multiplexing and separation, respectively. Fiber optic cable 1
6 is connected to the equipment of the other station to form an optical transmission line, and it sends the optical signal optically multiplexed by the optical filter 12 to the other station, and also transmits the optical multiplexed optical signal from the other station. Upon receiving the signal, the optical filter 12 separates the light into wavelengths. The optical filter 12 may be configured, for example, by condensing light projected onto the concave lens from a plurality of electro-optical conversion elements spaced apart from each other on the optical axis of the concave lens onto the input end of the optical fiber 16. In addition to optical wavelength multiplexing,
On the contrary, the multiplexed light emitted from the end of the optical fiber 16 is passed through the concave lens and applied to a plurality of light-to-electrical conversion elements according to the light wavelength via a reflecting mirror or the like.

In the apparatus configured as described above, an example of the code block configuration of the transmission signal generated by the block signal generator 10 and the reception signal obtained by the synchronization output circuit 14 is as shown in a and b in FIG. 4, respectively. Become. In the transmission code block in Figure a, the 7th of the 8 information bits in the block is
For the th code M ₁ , its complementary code M ₁ ′ is the 9th code M 1 ′.
It is inserted in the second place. On the other hand, in the received code of FIG. b, that is, the corresponding transmitted code block of the partner station, the complementary code M ₂ ' to the eighth code M ₂ in the block is inserted at the ninth position. Note that the above code configuration is an example of one channel each for the transmission code of the own station and the reception code, that is, the transmission code of the other station, but in reality, multiple transmissions that are optically multiplexed are used. The codes are set so that the order of the information bits to be subjected to the ninth complementary code is different not only between the own station and the other side, but also between multiplexed channels of each station.

In the block signal generator 10, the information bits A to be transmitted are transmitted to the control circuit 1 for each channel.
After being temporarily stored in the memory 10-2 under clock control of 0-1, it is read out in a block configuration and applied to the complementary code addition circuit 10-4. At the same time, the control circuit 10-1 controls the complementary code generating circuit 10-3 to generate complementary codes for information bits of a predetermined order for each channel. Then, the complementary code adding circuit 10-4 transfers the complementary code given from the complementary code generating circuit 10-3 to the memory 10-2.
It is added to the end of the information bit string of each channel read out from the block signal, and is supplied to the electro-optic converter 11 in a complete form as a block signal. The error detector 15 on the reception side is configured with, for example, a parity check circuit, and when it receives the block signal converted for each channel by the opto-electrical converter 13, it detects the complementary code in the block and the parity check circuit. The synchronization signal is obtained by exclusive ORing with the corresponding delayed information bit. Therefore, if the synchronization signal is obtained at this synchronization signal output block cycle, it will be a correct synchronization signal, and if it is obtained in a disturbed state, it will be out of synchronization and an alarm signal will be sent to the output side. On the other hand, the output of the optical-to-electrical converter 13 is similarly applied to the synchronization output circuit 14, which is controlled by the correct synchronization signal obtained from the error detector 15, and receives the block-divided received signal B on the output side. Obtained for each channel.

Now, according to this device, during communication with the partner station device, for example, the electro-optical converter 11' of the partner station,
Alternatively, if a failure occurs in the transmission line 16 and the reception signal from the other station cannot be obtained, the transmission signal of the own station leaks to the optical-to-electrical converter 13 side in the optical filter 12, but the signal is not transmitted to the complementary code. Since the position of the corresponding code is different from the preset code position of the received signal, error detector 15 detects block synchronization and sends out an alarm signal. By hearing this alarm, you can immediately know that the optical signal from the other station has been cut off.

In the above embodiment, the code structure of the block signal was explained as 8BIC, but the number of information bits is not limited to this, and several bits that also serve as mark rate adjustment may be added following the information bits. However, it goes without saying that any one of them may be selected as the target of the complementary code.

Furthermore, although the above embodiments are cases in which the present invention is applied to a bidirectional optical multiplexing system, it is clear that the invention can also be applied to a unidirectional optical multiplexing system. In that case, a unidirectional optical filter is used, but it is still used for optical multiplexing.
Therefore, if, for example, a failure occurs in one of the multiplexed optical signals at the transmitting station and the receiving station no longer receives the optical signal, the optical filter for optical wavelength separation at the receiving station will Even if the received light of other working channels leaks into the channel where the fault has occurred, an alarm to notify the occurrence of the fault can be obtained from the error detector for the same reason as described above.

As is clear from the above description, according to the present invention, data is transmitted by optical wavelength division multiplexing by changing the order of complementary codes of block signals and their corresponding codes for each channel to be multiplexed. As a result, it is now possible to accurately detect interruptions in optical transmission signals for each channel on the receiving side without complicating the equipment configuration, and it has become possible to immediately take measures in the event of a failure. In this respect, the effect of improving reliability and maintainability is significant.

[Brief explanation of drawings]

Figure 1 is a block diagram showing an example of the configuration of an optical transmitter/receiver that applies a conventional optical transmission system, and Figure 2 is a
FIG. 3 is a block diagram showing the structure of the embodiment according to the present invention; FIG. 4 a and b
3 are formats showing the configuration of the transmit and receive block signals, respectively, applied to the embodiment of FIG. In the figure, 10 is a block signal generator;
-1 is a control circuit, 10-2 is a memory, 10-3 is a complementary code generation circuit, 10-4 is a complementary code addition circuit, 1
1 is an electric-to-optical converter, 12 is an optical filter, 13 is an optical-to-electrical converter, 14 is a synchronous output circuit, 15 is an error detector, and 16 is an optical fiber cable.

Claims (1)

[Claims] 1. N information bits are transmitted for each block between the two stations connected by an optical transmission line, and a complementary code for the m-th (mN) information bit is attached after these information bits. In a system for transmitting data using an optical wavelength multiplexing system, the transmitting side includes means for encoding optical signals having different wavelengths by respectively changing the order of the m-th bit of the information bit; means for optically wavelength multiplexing the equally encoded optical signals and transmitting the same; on the receiving side, means for separating the optical wavelength multiplexed signals received via the transmission line into respective optical wavelengths; means for photo-electrically converting each of the optical signals separated by the separating means, and detecting a signal for each block encoded by changing the order of the m-th bit, and the like; means for receiving the outputs of the signal detecting means and detecting code errors from the m-th bit of the different order of the information bits and the complementary code bits thereof, respectively; An optical transmission system characterized by selectively receiving only the corresponding information bits on the transmitting side by detecting the presence or absence of code errors. 2. In the optical transmission system as set forth in claim 1, when a bidirectional optical wavelength division multiplexing system is applied in which both the stations are equipped with the various means on the transmitting side and the receiving side, one-way transmission is possible. For the m-th bits of the information bits in different orders, which are suitable for the sending side and the receiving side, and the m-th bits, respectively, in different orders, of the information bits, which are suitable for the sending side and the receiving side in the opposite direction, Furthermore, this optical transmission system is characterized by having different rankings.