JPS6362148B2 - - Google Patents

Description

[Detailed Description of the Invention] [Description of the Field to which the Invention Pertains] The present invention relates to a digital optical system for transmitting digital optical signals through an optical relay transmission line configured by alternately cascading optical fiber cables and regenerative repeaters. Concerning a monitoring method for a transmission method. In particular, the present invention relates to a monitoring system that can individually select each regenerative repeater and monitor its status even during service operation of a transmission line.

[Description of conventional technology]

As optical relay transmission lines are put into practical use as high-speed multiplex communication lines, monitoring methods for maintaining high quality transmission lines have become an important issue. Particularly, when the information to be transmitted is image transmission or data transmission, such as by facsimile, slight deterioration of the repeater is perceived as a clear error. Many monitoring methods for this purpose have been proposed in the past.

Typical examples include JP-A-56-100538 and Technical Report CS80-10 of the Communication Systems Study Group of the Institute of Electronics and Communication Engineers. In this conventional monitoring method, the state of a regenerative repeater placed on a transmission path can be remotely monitored from a transmitting end or a receiving end, but in both cases, the monitoring operation is performed during non-operation. That is, in order to monitor the transmission path, it is necessary to temporarily stop the signal during service operation and transmit a monitoring signal instead. For this reason, the time during which monitoring can be performed is restricted, and the accuracy of monitoring deteriorates. For example, even if there is a regenerative repeater that is gradually deteriorating, there is a drawback that it is not possible to detect this before a failure occurs.

On the other hand, as a method for monitoring the optical relay transmission line while it is in operation, it has been considered to perform monitoring during operation by time-sharingly transmitting a monitoring signal to the digital signal that transmits the main signal. For this purpose,
It is necessary to provide each regenerative repeater with a circuit for correctly branching the main signal and the supervisory signal and for responding thereto and transmitting an information signal representing the status. especially,
In order to extract the monitoring signal and insert the information signal, it is not easy to design a synchronous circuit on a circuit scale that can be realized by each regenerative repeater, and the power consumption of these circuits also increases, making it difficult to This will have a major impact on the overall design.

[Purpose of the invention]

The present invention was made against this background, and it is possible to monitor transmission paths with high precision during service operation, and the circuit configuration provided in the repeater is simple. The purpose of this invention is to provide a monitoring method for digital transmission paths that can be designed to reduce power consumption.

Another object of the present invention is to provide a digital transmission path monitoring system that enables repeater connection and other remote control.

[Key points of the invention]

The present invention inserts a fixed digital code string with a fixed number of bits according to a coding rule that cannot exist as a main signal string from the transmitting end of a transmission path as a common monitoring signal for each regenerative repeater, and furthermore, the insertion of this monitoring signal is performed periodically, and depending on this period, each regenerative repeater is instructed to select,
The present invention is characterized by performing identification of monitoring instructions, monitoring the operating state of the regenerative repeater, and controlling for the monitoring.

That is, the first aspect of the present invention is that a monitoring signal consisting of a digital code string of a predetermined code length that does not comply with the above prohibition rule is set in advance in the regenerative repeater at the transmitting end for a duration controlled by input information. The monitoring signal and a signal consisting of a digital code string having the same code length as the monitoring signal and conforming to the prohibition rule are inserted in a time division manner between the main signal strings so that they appear at a period of the selected frequency. The code string composed of
The regenerative repeater is provided with means for transmitting to the relay transmission path, and the regenerative repeater extracts the selected frequency by extracting a monitoring signal consisting of a code string that does not comply with the prohibition rule from the code string received from the relay transmission path. first means; second means for identifying said input information by said duration of said selected frequency extracted by said first means; third means for replacing the monitoring signal transmitted to the relay transmission path with a digital code string corresponding to a signal given to an input terminal of information representing the state of the regenerative repeater obtained at the position of the regenerative repeater; The receiving end of the relay transmission path is provided with means for receiving the digital code string sent from the third means.

A second aspect of the present invention is to provide a regenerative repeater with the first means and the second means, and further to repeat the regenerative repeater at the position of the regenerative repeater in response to input information identified by the second means. The present invention is characterized by comprising fourth means for controlling the circuit of the regenerative repeater and/or the circuit of the regenerative repeater of another relay transmission line disposed at the position.

[Explanation based on examples]

The transmission line code of the digital transmission system is BSI
(BitSequence Independent). mBnC (m Binary
(with n Complement) code is being considered (for example, Technical Report CS81-30 of the Communication Systems Study Group of the Institute of Electrical Communication Engineers). In the case of this mBnC code, the number of consecutive same codes in the main signal is suppressed to (m+n) bits or less. Therefore, (m+n+1)
When transmitting a sequence of consecutive same codes of bits or more,
Since this cannot be a main signal, it can be distinguished as a different type of signal, that is, a supervisory signal.

FIG. 1 shows the structure of a code string according to an embodiment of the present invention. The main signal M is composed of an mBIC code string.
A short monitoring signal at a constant period during this main signal M
Insert SV. In FIG. 1, the main signal M is displayed briefly on the overall time axis to make the explanation easier to understand, but for example, only 10 bits of the supervisory signal SV are inserted for every 4000 bits of the main signal M.

The supervisory signal SV is composed of a code string of (m+4) bits in total, consisting of a (m+2) bits of consecutive 0 codes and "1"s added one bit before and after the code. The reason why one bit of "1" is added before and after is that depending on the contents of the main signal M before and after it, there may be more than (m+2) consecutive "0" bits, which has a negative effect on the transmission system. This is to ensure that you do not give up.

FIG. 2 is a block diagram of the main parts of a regenerative repeater according to an embodiment of the present invention. A fiber optic cable 1 is coupled to an opto-electrical converter 2 whose electrical output is connected to an equalizer 3
The signal is given to the discriminator 4 through the. One of these outputs is sent to the NRZ via the monitoring circuit 6 according to the present invention.
A code converter 7 is provided. Its output is applied to a drive circuit 8, which drives an electro-optical converter 9, and is sent to the next section of optical fiber cable 1'.
The timing circuit 5 separates a timing signal from the output signal of the equalizer 3 and controls the discriminator 4. The other output of the discriminator 4 is given to the monitoring circuit 6.

In the monitoring circuit 6, the input signal is given to the detection circuit 10. An example of the configuration of the detection circuit 10 is shown in FIGS. 3 and 4. FIG. FIG. 3 shows an example of a configuration using a delay line 31. FIG. 4 shows an example of a configuration using a shift register 41. Both are circuits that can obtain output pulses only when (m+2) bits of the same code continuous code string are input.

Returning to FIG. 2, the pulse output of detection circuit 10 is applied to trigger flip-flop 11. For each pulse output, flip-flop 11 inverts its output state. A desired frequency component is extracted from this output by a bandpass filter 12. Wave device 12
The output of is given to a Schmitt trigger circuit 14 via an integrating circuit 13. The output of the Schmitt trigger circuit 14 is sent to a monostable multivibrator 15.
It is also branched and applied to the signal duration comparison circuit 16. The output of the monostable multivibrator 15 is given to a comparison circuit 16, and the branch output is given to a shift register 18 as a shift pulse.

The output of the comparator circuit 16 is demodulated by the pulse width discrimination circuit 17 into binary codes "1" and "0" based on the length of the output pulse width. This demodulated output is given to the shift register 18 as a digital signal. Address data for identifying the selection of a self-regenerating repeater and command data for instructing monitoring contents are input to the shift register 18 . The control circuit 19 is
The contents of the shift register 18 has the function of referencing the address and command data with data previously stored in its own circuit, and if they match, starting or stopping the execution of the contents instructed by the command data.The contents of the shift register 18 will be explained in detail later. explain.

The terminal 20 is an input terminal to which a signal representing the state within the repeater is connected. The contents include, for example, the bias state of the electro-optical converter 8, the temperature state, and the equalizer 3.
The automatic gain control voltage included in the data, the state of the threshold voltage of the discriminator 4, etc. Each of these is an analog signal and is applied from a terminal 20 to a multiplexer 21. A necessary terminal 20 is selected according to the contents of the command, and the selected signal is converted to a specified frequency by the voltage controlled oscillator 22. The output of the voltage controlled oscillator 22 is periodically sampled by the sampling circuit 23 according to the output of the supervisory signal detection circuit 10, and inserted into the supervisory signal code string by the delay line 24 and the coupling circuit 25. Delay line 26 provides a delay to the signal passing through it.

FIG. 5 is a time chart showing the operation from the supervisory signal detection circuit 10 to the data signal demodulation of the shift register 18 in the above-mentioned embodiment device. FIGS. 5a to 5h show operating waveforms at points a to h indicated by cross marks in FIG. 2. a is an input signal to the supervisory signal detection circuit 10, and T _sv is the time interval at which the supervisory signal is time-division multiplexed to the main signal. Each repeater has a 1/1
A frequency other than T _sv is set in advance in the bandpass converter 12 as a selected frequency. FIG. 5 shows, as an example, the case where the selection frequency is set to 1/2T _sv .

First, a case where identification control of an arbitrary repeater is performed will be explained using FIG. 5. In FIG. 5, the left diagram A shows the operation for inputting one binary signal "1" to the shift register 18. Figure B on the right shows the operation of the monitoring circuit for similarly inputting "0" to the shift register 18. FIG. 5a shows a transmission signal transmitted to the optical fiber cable 1. In FIG. Every 2T _sv twice the basic period of the monitoring signal, an SV code string that is a monitoring signal that does not comply with the prohibition rule shown in FIG.
Identification control monitoring in which SV ^* code strings (for example, Figure 7, excluding SVI in Figure 10, which will be explained later) that conform to the prohibition rule and are alternately inserted in a bit pattern different from the SV code string. The signals are multiplexed into a main signal train. By inserting the SV ^* code string alternately with the SV code string, the period at which the SV code string appears can be reduced.
2T _sv , and an identification control monitoring signal that passes through the selected frequency 1/2T _sv of the band wave transmitter 12 of each repeater is obtained.

The pulse width of the monostable multivibrator 15 is τ _n
First, the case where "1" is specified will be explained. As shown in FIG. 5A, an identification control monitoring signal consisting of repetitions of SV and SV ^* is transmitted from the transmitting end as a monitoring signal at a fundamental frequency _sv . This means that the output of the Schmitt trigger circuit 14 is τ ₁ as shown in FIG. 5e.
(>τ _n ) for a constant duration T ₀ . If we take the AND of this output pulse e and the output pulse f of the monostable multivibrator 15, we get
The output of the signal duration comparison circuit 16 has a pulse width τ _n
The output will appear. A signal h is obtained by the pulse width discrimination circuit 17 which sets the pulse width τ _n to "1".

Next, a case where "0" is specified will be explained. By the same method as described above, the discrimination control supervisory signal is sent out for another short constant duration T ₁ until the output of the Schmitt trigger circuit 14 reaches τ ₀ (<τ _n ) as shown in FIG. 5e. do. If this output pulse e is ANDed with the output pulse f of the monostable multivibrator 15, an output with a short pulse width τ ₀ appears at the output of the comparison circuit 16. A _signal h
get. Therefore, the code strings SV, SV ^* , SV,
The transmission time of a supervisory signal consisting of repetitions such as SV ^* has a duration T 1 and T ₀ corresponding to " ₁ " and "0" of the address and command data to the repeater.
By changing , any repeater can be identified and a monitoring command can be issued to that repeater. In the supervisory signal interval between time T ₁ and time T ₀ , that is, the interval in which the identification control supervisory signal is not transmitted, it is sufficient to simply repeatedly transmit the SV code string.

Next, a method for transmitting the status of the regenerative repeater to the receiving end after identifying the regenerative repeater and issuing a monitoring command will be described.

FIG. 8 is a time chart illustrating the circuit operation from the output of the electrically controlled oscillator 22 to the output of the coupling circuit 25 shown in FIG. Figure 8 a, b,
i, j, and k are operating waveforms at points marked with an x in FIG. 2. In the transmission path code string, SV codes are time-division multiplexed at each time interval T _sv as shown in FIG. 8a.

FIG. 9 shows the SV code. Since the period at which this SV code appears is T _sv , this signal is distinguished from the identification control monitoring signal, is blocked by the bandpass filter 12, and does not disturb the contents of the shift register 18.

On the other hand, the analog information selected by the multiplexer 21 is converted by the voltage controlled oscillator 22 into "1" and "0" codes of the frequency _VCO as shown in FIG. 8i. Here, the frequency _VCO is sampled at a period T _sv and transmitted to the receiving end, so in order to improve sampling accuracy, it is desirable to set _VCO << 1/T _sv . By performing a logical product of this signal i and the output b of the detection circuit 10 in the sampling circuit 23, j obtained by sampling the rectangular wave i with a period T _sv is obtained. This sampled pulse is applied by a delay line 24 to a combination circuit 25 which is an OR circuit.

The delay lines 24 and 26 connect the sampling pulse to m+2 bits of the SV code transmitted from the transmitting end.
It is adjusted and set at the time of manufacture of the repeater to match the phase of any one bit in the code. The SVI code in Figure 10 is (m+2) of the SV code in Figure 9.
This example shows a case where the m+2nd code of the O codes of the bits and the 1st code of the sampling pulse are ORed.

Therefore, the output of the coupling circuit 25 is the result of ORing the sampled pulse j and the SV code transmitted from the transmitting end, as shown in FIG. 8k. That is, the output of the voltage controlled oscillator 22 is "1".
When , the SV code becomes an SVI code that conforms to the prohibition rule,
When it is "0", the SV code is output as is, and this signal train is transmitted via the optical fiber cable 1'.

FIG. 10 shows an example of an SVI code. At the receiving end, the same circuit as the monitoring signal detection circuit 10 of the repeater extracts an output corresponding to the sampled pulse train j from the received signal train, and then demodulates the frequency _VCO by performing envelope detection on the output. , the status of each repeater can be grasped from this frequency _VCO .

The above explanation has been about monitoring the status of one regenerative repeater in the same housing, but the status of other regenerative repeaters can also be monitored by inputting a signal representing the operating status of each circuit to the terminal 20 of the multiplexer 21. Can be monitored. Therefore, in a system in which regenerative repeaters for multiple systems are mounted in the same housing, by providing the monitoring circuit of the present invention for each regenerative repeater, when a repeater failure occurs, the normal system line is used to It is possible to accurately grasp the failure state of a failure repeater.

In addition, although the above explanation was limited to the method of transmitting the operating status of the regenerative repeater to the receiving station, it is also possible to switch the electro-optical conversion element having a call depending on the contents of the command data, and to transmit the uplink transmission line signal downlink within the repeater. It can also be applied as a control signal for returning to a transmission line signal.

FIG. 11 is a diagram showing an example of a configuration when this monitoring circuit is applied to transmission line signal return. code 1
27 is a gate circuit forming a loop of the upstream transmission line and the downstream transmission line, and the control circuit 19 of the monitoring circuit 6
is limited by the output of The uplink transmission line signal is taken out from the output of the coupling circuit 25, and the downlink transmission line signal NRZ/RZ
By inserting it into the input of the conversion circuit 7, it becomes possible to transmit the operating state of this regenerative repeater to the uplink transmission line signal transmission station using the downlink transmission line, similar to the method described above. In this case, it is preferable that the downlink transmission path signal is stopped at the downlink transmission path signal transmission station.

[Explanation of application examples]

In the above example, the prohibition rule for the main signal is a restriction on the number of consecutive "0"s, but the present invention can be similarly implemented with respect to restrictions on the number of consecutive "1s" and other prohibitions.

The input information for controlling the monitoring signal is a binary signal in the above example, but it may be a multi-value signal or an analog signal.

In the above example, the input information is stored in the register by the regenerative repeater, and the control circuit takes in the input information and performs control, but the input information can also be identified using other configurations. Particularly when the input information is a multilevel signal or an analog signal, the circuit of this part can be simplified accordingly.

In addition to loopback connection, the repeater can be controlled by changing bias voltage, switching connection with spare parts, etc.

It is a matter of design whether the number of bits of the supervisory signal should be set to the same degree as the number of bits of the main signal.
For example, if the method of the present invention is implemented on a digital relay transmission line of several hundred Mb/s, even if the ratio of the monitoring signal to the main signal is set to about 1/100,
A monitoring signal on the order of Mb/S can be transmitted. Therefore, it is possible to select a wide variety of monitoring items or control items, and any number of repeaters can be used.

In the method of the present invention, multiple pieces of information can be transmitted in the supervisory signal, so the supervisory signal can be transmitted redundantly by repeatedly transmitting it, so that the supervisory signal can be transmitted effectively even when the error rate of the relay transmission path deteriorates. It is also possible to configure it as follows.

[Explanation of effects]

As explained above, according to the present invention, in order to identify regenerative repeaters, a prohibited code string that does not exist in the main signal code string is used as a monitoring signal, and a monitoring signal common to each regenerative repeater is used. Since it is a signal, there is an advantage that the configuration of the monitoring circuit is extremely simplified. Therefore, it becomes possible to individually identify and monitor regenerative repeaters from a distance during service operation, which eliminates the need to set up backup lines, improves the operation rate of transmission lines, and improves system design and operation. It is extremely advantageous. Further, since it is possible to give various control signal commands even when not in operation, there is an advantage that maintenance content can be improved. The system of the present invention is particularly effective when implemented in a submarine optical fiber system.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a transmission code structure according to an embodiment of the present invention. FIG. 2 is a block diagram of a main part of a regenerative repeater according to an embodiment of the present invention. FIG. 3 and FIG. 4 are configuration diagrams of a supervisory signal detection circuit. Figure 5 is a time chart for explaining the operation. FIG. 6 is a diagram showing an example of the structure of an SV code string. FIG. 7 is a diagram showing an example of the structure of an SV ^* code string. 8th
The figure is a time chart for explaining the operation. FIG. 9 is a diagram showing an example of the structure of an SV code string. FIG. 10 is a diagram showing an example of the structure of an SVI code string. FIG. 11 is a configuration diagram of the main parts of a repeater when making a loopback connection. 1, 1'...Transmission line by optical fiber, 6...Monitoring circuit, 10...Monitoring signal detection circuit, 11...Trigger
Flip-flop, 12...bandwidth wave generator, 13...integrator circuit, 14...schmitt trigger circuit, 15...mono multivibrator, 16...comparison circuit, 17...
Pulse width discrimination circuit, 18...Shift register, 19
...Control circuit, 20...Input terminal (inputs the state of the repeater, etc.), 21...Multiplexer, 22...Voltage controlled oscillator, 23...Sample circuit, 24...Delay line, 25...Coupling circuit, 26...Delay line.

Claims (1)

[Scope of Claims] 1. A digital relay transmission line including a plurality of regenerative repeaters is provided with a relay transmission line configured to transmit a main signal train having a specific prohibition rule from the transmitting end of the relay transmission line. In the monitoring method, the transmitting end transmits a monitoring signal consisting of a digital code string of a predetermined code length that does not comply with the above prohibition rule for a duration controlled by the input information to the regenerative repeater with a selection set in advance. The monitoring signal and a signal consisting of a digital code string having the same code length as the monitoring signal and conforming to the prohibition rule are inserted in a time-division manner between the main signal strings so that the signal appears at the frequency period. The regenerative repeater includes means for transmitting the constructed code string to the relay transmission path, and the regenerative repeater extracts a monitoring signal consisting of a code string that does not conform to the prohibition rule from the code string received from the relay transmission path. a first means for extracting said selected frequency by said first means; a second means for identifying said input information by said duration of said selected frequency extracted by said first means; In response to the identified input information, a digital code string conforming to the above prohibition rule is transmitted to the relay transmission path in response to a signal given to the input terminal of information representing the state of the regenerative repeater obtained at the position of the regenerative repeater. a third means for replacing the above-mentioned monitoring signal transmitted to the relay transmission line, and a receiving end of the above-mentioned relay transmission path is provided with means for receiving the above-mentioned digital code string transmitted from the third means. Features a monitoring method for digital relay transmission lines. 2. The input information is composed of a plurality of continuous binary signals, and has two types of duration, long and short. The second means includes a register circuit that stores input information that arrives in chronological order, and and means for selecting a repeater based on the accumulated input information. 3 Information representing the status of the regenerative repeater obtained at the position of the regenerative repeater includes information about the regenerative repeater and a regenerative repeater on another relay transmission line installed in the same chassis as the regenerative repeater. The method for monitoring a digital relay transmission line according to claim 1 or 2, including information on: 4 In a method of monitoring a digital relay transmission line including a plurality of regenerative repeaters, the relay transmission line is configured to transmit a main signal train having a specific prohibition rule from the transmitting end of the relay transmission line. The supervisory signal and the supervisory signal are configured such that the supervisory signal consisting of a digital code string with a predetermined code length that does not comply with the above prohibition appears in the regenerative repeater at a period of a preset selection frequency during a duration controlled by the information. , a code string constructed by time-divisionally inserting a signal consisting of a digital code string having the same code length as the monitoring signal and conforming to the above prohibition rule between the main signal strings, is transmitted to the relay transmission path. The regenerative repeater includes a first means for extracting the selected frequency by extracting a monitoring signal consisting of a code string that does not comply with the prohibition rule from the code string received from the relay transmission path. means for identifying the input information by the duration of the selected frequency extracted by the first means; and reproducing and relaying the input information in response to the input information identified by the second means. and fourth means for controlling the circuit of the regenerative repeater and/or the circuit of the regenerative repeater of another relay transmission line disposed at the position of the digital relay transmission. Road monitoring method. 5. The digital relay transmission line monitoring system according to claim 4, wherein the fourth means includes means for making a return connection of the relay transmission line.