JPS63261930A - Repeater monitor system for optical digital transmission line - Google Patents

Abstract

PURPOSE:To attain economy and to suppress generation of a code error by applying phase modulation or frequency modulation to a control instruction controlling the operating state of a repeater, sending the result and returning an acknowledge signal in a frequency different from the carrier frequency of the sender side. CONSTITUTION:A control instruction signal W outputted from a control instruction generator 12 is formed into a keying signal E by applying keying (modulation) to a carrier C from a carrier generating circuit 111 at a preliminary modulation circuit 112. The signal E is inputted to a phase modulation circuit 110 to modulate a pulse phase of a communication signal S thereby obtaining a transmission signal D being the superimposition of the signals S, W. As the carrier frequency of the acknowledge signal from the repeater, the frequency dividing or multiplying the carrier frequency for transmission is used. Thus, the signal is sent to an optical fiber 2s in in-service, the production of S/N code error is suppressed, and a standby system or the like is not required and economy is attained.

Description

Detailed Description of the Invention (1) Purpose of the Invention [Field of Industrial Application] The present invention relates to an optical fiber cable in which a plurality of optical digital repeaters (hereinafter abbreviated as "repeater") are inserted into an optical fiber cable. The present invention relates to digital transmission lines, and in particular to a repeater monitoring system for optical digital transmission lines that monitors the operational status of repeaters in an in-service state.

[Conventional technology] Low loss optical fiber and medium 1! Optical digital systems consisting of devices require high reliability over a long period of time, and
Even with μ, in order to monitor the operating status of a repeater with multiple circuit elements and to locate the fault location when a fault occurs, the cutoff of the sign error occurring in each repeater section is measured at T.
I! It is essential.

Conventional repeater monitoring methods include the out-of-service method, in which a special signal is transmitted and measured by relaying a communication service, and the in-service method, in which a special signal is superimposed on the transmitted signal and measured while the communication service is in progress. be. In the following explanation, we will discuss an in-service method that allows repeaters to be monitored without requiring a communication service.

FIG. 1 is a schematic diagram of a conventional in-service repeater monitoring system.

In the figure, 1 is a landing station installed on the land side, 2 and 2R are up and down optical fiber cables (hereinafter simply referred to as "optical fibers") that are transmission lines, and 3 is an optical fiber 2. This is a repeater that amplifies and equalizes the communication signal whose level has been lowered by propagating within the network. The landing station 1 generates a control command signal (hereinafter referred to as a "control signal") for monitoring and controlling the transmitting terminal station 11 and the repeater 3, which convert the communication signal to the communication method of the optical fiber 28. A control command generator 12 that demodulates the signal from the optical fiber 2Il, a receiving terminal station 13 that demodulates the signal from the optical fiber 2Il, and a response that demodulates the response signal sent back after the control signal sent from the control command generator 12 is processed by the repeater 3. It consists of a signal demodulator 14, and a middle III unit 3.
are regenerative relay circuits 31 and 31R that amplify, equalize, and reproduce communication signals and control signals, a control command receiving circuit 32 that detects and demodulates control signals, a carrier regeneration circuit 33 that extracts and reproduces modulated carriers, and control signals. a response signal creation circuit 34 for creating a response signal that informs the operating status of the elements in the regenerative relay circuit 318; and a premodulation circuit 35 that premodulates the response signal with the subcarrier regenerated by the subcarrier regeneration circuit 33. Each of the circuits includes a loopback creation circuit 36 that loops back the upstream regenerative relay circuit 318 and the downstream regenerative relay circuit 31R.

Next, the operation will be explained.

The control signal is transmitted to the optical fiber 2 via the transmitting terminal station 11. Although the control signal is superimposed on the communication signal originally transmitted through the optical fiber 2s, it is modulated using subcarriers so as not to deteriorate the transmission characteristics of the communication signal, thereby enabling in-service control. The control signal is transmitted through repeater 3
regenerative relay circuit 31. The amplified and equalized signal is demodulated by the control command receiving circuit 32, and the command is executed.

In general, monitoring is carried out by, for example, using a premetering function to monitor the input power level of the regenerative repeater circuit 318 and the operating status of the semiconductor laser to the landing station, and a function installed between the semiconductor laser cutoff and the upstream/downstream regenerative repeater circuits 318 and 31R. control functions such as creating a loopback creating circuit 36 by operating a light or electrical switch.

In telemetering, it is necessary to detect parameters of the repeater 3 and transmit them to the land station 1 using control signals.

For this reason, the input power level and laser operation parameters are converted into binary signals in a format suitable for telemetering, for example, by A/D conversion in the response signal generation circuit 34.

When the telemetering operation command is received, the response signal formatted by the response signal generation circuit 34 is sent to the control! Following the I command, the signal is premodulated by the premodulation circuit 35 using subcarriers transmitted in-service from the transmitting terminal station 11, and then transferred to the downstream regenerative relay circuit 31R. The downstream regenerative relay circuit 31 superimposes the response signal on the original communication signal, transmits it in-service to the landing station 1, and sends it to the receiving terminal station 13.
The telemetering operation is completed by introducing the response signal to the demodulator 14 through the demodulator and demodulating the response signal.

FIG. 2 is a signal waveform diagram for explaining a conventional method of modulating a control command signal.

FIG. 2(a) shows an arrangement of digital signals that are communication signals sent out from the transmitting landing station 1. In Figure (a), parity bits, such as mBIP, are inserted into the communication signal at equal intervals, and the parity is determined so that the number of marks in the parity block is an even number. Even parity. (b) is a signal waveform of a flip-flop output built in the control command receiving circuit 32 of FIG. In (b), P indicates the output at the position of the parity bit, and B indicates the output for communication signals other than the parity bit. The probability of occurrence of a mark code in a communication signal is random, and the average probability is 1/2. On the other hand, the parity bits are inserted so that the number of marks in the parity block is always even, so that the flip-flop output can maintain a constant value at the position of each parity bit.

(b) shows an example in which the output is 1''.

(C) is a low-pass filter (hereinafter referred to as rLPF) built in the control command receiving circuit 32 that converts the flip-flop output into
This shows the filter output signal when input to the filter (referred to as J).

Previous) Like a tree, the mark occurrence probability is 1 in the communication signal part.
/2 and becomes "1'' at the parity bit position, so the DC voltage of the LPF output shows a voltage slightly higher than 172 of the peak voltage VP of the flip 70 tube output.

By the way, FIG. 2(d) shows the 3ffi parity in the figure.
An example in which bit P' is forcibly inserted as odd parity is shown. Other parities are even parities. Now, when this signal is input to a flip-flop, an output as shown in (e) is generated. That is, the flip-flop output is inverted at the position of the parity bit P' (from "1" to "0" in the example of (e)), and this inverted state continues thereafter. That is, the DC voltage at the position of the parity bit P' changes to a voltage slightly lower than 1/2 of the flip-flop output voltage V, and this state continues thereafter.

According to this principle, if the parity bits inserted into the communication signal are periodically set to odd parity, a frequency component corresponding to this period is generated in the LPF output. Therefore, it becomes possible to transmit the baseband code of the control command to the repeater 3 using this frequency component (hereinafter referred to as "SV frequency") as a carrier.

Next, the transmission of the telemetering signal (response signal) from the repeater 3 to the receiving terminal station 13 is performed as follows. In FIG. 1, parameters to be transmitted as a response signal are formatted by a format circuit built in the response signal generation circuit 34. On the other hand, following the control command, the aforementioned carrier is transmitted from the transmitting terminal station 11 and extracted by a band pass filter (BPF) in the subcarrier regeneration circuit 33. Furthermore, a phase modulation circuit is inserted after the identification circuit in the downlink regeneration relay circuit 31R (not shown).
. Now, when the carrier extracted by the above-mentioned BPF is input to this phase modulation circuit according to the mark and space of the binary response signal format (for example, it is input when it is a mark and disconnected when it is a space), the downstream The pulse phase of the communication signal on the line is modulated. The degree of this modulation is limited to an amplitude that does not affect the regenerative relay function of the repeater inserted after the repeater, and the amplitude is limited to the extent that it does not affect the regenerative relay function of the repeater inserted after the repeater. Transmit. Figure 3 shows this situation. (a) shows the carrier input to the communication signal (b) according to the format of the response signal.

(C) shows how the pulse position of the original communication signal changes depending on the frequency of the carrier signal. The conventional transmission method of control commands and response signals for repeater monitoring has been described above.

[Problems to be Solved by the Invention] Figure 4 shows that by inverting the parity bits as described above,
The spectrum of generated carriers is shown.

In FIG. 4, ■ indicates a state in which there is no code error in the transmission path. In this case, the spectrum is a single sine wave and the amplitude is maximum.

On the other hand, 010 and ■ are cases where code errors in the transmission path gradually increase, and although it varies depending on the parity insertion interval, 0 is about 10, O is about 10-5, and ■ is about 10-4. Indicate a mistake. That is, when a code error occurs in the transmission path, the spectrum is spread, the amplitude at the carrier frequency is reduced, and the reception S/N within the repeater is degraded.

Generally, in conventional repeater monitoring, if a code error of 10-5 or more occurs, it is not only difficult to control the repeater using this transmission line, but also the noise can even cause control malfunctions. . Broadcast 2! As explained in relation to Figure 1, the supervisory system also includes a function to loop back the uplink and downlink signals, and if a loopback is formed due to malfunction, the communication line will be disconnected. , resulting in serious damage.

For this reason, only the other aspects of monitoring that do not affect the line status even if a malfunction occurs are controlled using the above-mentioned parity-even-odd method, and for those that cause serious failures, special There is an example of using a method of transmitting a code out of service, that is, taking the line out of service. As another method, a method is used in which a backup relay system is constructed and connections are made within the middle 11 circuit so that the repeater monitoring and control can also be performed from the kitten relay system.

The above-mentioned method requires two systems of supervisory control, and the method described below has the problem of being uneconomical and complicated due to the installation of a backup system.

(2) Structure of the Invention [Means for Solving the Problems] The present invention has been made in order to solve the problems of the prior art mentioned above. It is an object of the present invention to provide a repeater monitoring method for optical digital transmission lines that can monitor repeaters using an excellent method.

The present invention is characterized in that a carrier wave for transmitting control commands is keyed by a binary low-speed control command signal, and the clock of a communication signal is phase-modulated or frequency-modulated by the keyed carrier wave and transmitted in-service. After detecting the control command signal from the received transmission signal by delay detection or synchronous detection, the desired repeater monitoring information is converted into a low-speed binary code into a response signal that is transmitted to the carrier wave or another signal transmitted in advance from the transmitting terminal station. The purpose of this method is to key a carrier wave obtained by converting the frequency of one of the carrier waves, phase-modulate it into a transmission signal, and send it back.

[Function] In the present invention, since the control command signal is transmitted after being phase-modulated or frequency-modulated, the occurrence of S/N code errors within the repeater for regenerative repeating is suppressed, and the response signal from the repeater is transmitted at the transmitting side. Since the return signal is sent back at a carrier frequency different from that of the carrier frequency, it has the effect of preventing malfunctions.

[Example] The present invention will be described in detail below using the drawings.

In the following description, in order to clarify the difference from the conventional configuration, the explanation will focus on the points that are different from the conventional configuration.

FIG. 5 is a schematic diagram of a transmitting terminal station 11' according to the present invention,
In the same figure (a), the control command signal is phase-modulated and sent to the transmitting terminal station 11.
FIG. 11(b) is a block diagram showing a case in which the control command signal is transmitted after being frequency-modulated.

In FIG. 3A, a control command signal W (containing a designation code for specifying a repeater and an effective command), which is binary low-speed data output from a control command generator 12, is output from a carrier generation circuit 111. Carrier C of H2 in about tens of
The premodulation circuit 112 performs keying (variation 31) using marks and spaces to obtain a keying signal E. This keying signal E is input to the phase modulation circuit 110, and the communication signal S
The pulse phase (position) of is modulated to obtain a transmission signal in which the communication signal S and the control command signal W are superimposed. Therefore, the control command signal W can be superimposed on the communication signal S and transmitted in-service to the optical fiber 28 from the transmitting terminal station 11'. Note that at the time when the transmission of the 1iil control command signal W is completed, the carrier C from the carrier generation circuit 111 is continuously transmitted, or the carrier frequency f' is generated from another carrier generation circuit different from the carrier generation circuit 111.
It is necessary to transmit the carrier so that the carrier can be detected on the repeater 3 side. Further, the phase modulation circuit 110 can be easily realized by a variable delay circuit using a barac diode or the like.

As mentioned above, in the present invention, the carrier C is controlled by the control command signal W.
Since the communication signal S is phase-modulated using the keyed signal E and sent out, the tolerance for S/H deterioration due to regenerative relay within the repeater 3 is increased, and the sign? J error can be reduced.

On the other hand, FIG. 6(b) is a block diagram of the transmitting terminal station 11' when the control command signal W is frequency modulated and transmitted.
The phase modulation is the same as the phase modulation shown in FIG. 4(a) until the II 60 command signal @W keys the carrier of the main 129 frequency f to obtain the signal E. The signal E keyed by the control command signal is input to the clock generation circuit 114, and the lock frequency f is determined depending on the presence or absence of the carrier C. (same as the clock frequency fo of the communication signal). At that time, if the frequency deviation (±fd) is made sufficiently small compared to the carrier frequency, it is possible to prevent spectrum spreading and also to prevent the occurrence of code errors during regenerative relay within the repeater 3. It can be prevented. Clock frequency f frequency-shifted by signal E. By frequency modulating the Δ signal S (clock frequency f.) with ±f in the frequency modulation circuit 113, a transmission signal F in which the control command signal W and the communication signal S are multiplexed can be obtained.

Next, the phase modulated or frequency modulated transmission signal D
Regarding how to detect the control 0R1 command signal W in the control command receiving circuit 32' in the repeater 3 from (F),
This will be explained using phase modulation as an example.

FIG. 6 is a block diagram of a control command receiving circuit 32' for detecting control command signals according to the present invention. The transmission @D branched by the regenerative relay circuit 313 in the relay 3 is
After being amplified by an amplifier 320, the signal is branched, one being input to a delay circuit 321, and the other being input to an attenuator 322 having the same loss as the delay circuit 321. Delay circuit 32
1 and the attenuator 322 are sent to the multiplier 323.
In the attack modified by LPF or BPF324, the key 1
The component of Syria C is extracted, and the detection circuit 3
At 25, the control command signal W is detected. That is, the control command signal W can be detected by commonly used delay detection. Note that the frequency conversion circuit 37 is one of the features of the present invention, and divides or multiplies the extracted carrier frequency f to obtain a carrier having a frequency f' different from the transmission carrier frequency f from the transmitting terminal station 11'. This is what you create. By making the carrier frequency f' of the response signal different from the carrier frequency f of the control command signal, it is possible to prevent other repeaters from malfunctioning due to the returned response signal. FIG. 7 shows the BPF 324 obtained by dividing the carrier frequency f for transmission by 172 as the carrier frequency f for return according to the present invention.
This shows a relationship diagram with characteristics. Even in this case, a passband of about 2KIIZ is practical, so in this example, by dividing the carrier by 172, there is no possibility that the response signal will be received incorrectly as a control signal, and highly reliable monitoring can be achieved. method can be implemented.

FIG. 8 is a block diagram when a control command signal is detected by synchronous detection according to the present invention. Key ↑ containing wave signal and modulation signal
・The rear C signal is detected by the same 11JI detection circuit 327 (multiplier), and the rest is the same as the delayed detection shown in FIG.

Next, calculation results of transmission characteristics when using the repeater monitoring method of the present invention will be explained.

FIG. 9 is a diagram showing the relationship between the number of relays and the received S/N when phase modulation according to the present invention is used, and the transmission rate is 140 Hbps.
, =F Ya IJ 7 Frequency 21 KHz, Communication BP
The reception S/N of the phase modulation signal with respect to the number of repeaters is shown when F band 2 is set to ++z and the Q of the timing extraction circuit of the regenerative repeater is 700.

The reception S/N is determined by the additive characteristics of the carrier frequency attenuation by the timing extraction circuit and the random jitter of the digital transmission signal generated as noise, but it is not possible to secure S/820 dB or more with up to about 80 relays. can. Therefore, 1.5 μm optical submarine cable system relay I?
! Since each interval has more than 100 gaps, even if the present invention is applied to a long-distance optical cable system, each repeater cannot receive enough S/S.
N can be secured.

Note that this transmission characteristic is the same for the transmission of the response signal.

FIG. 10 shows experimental results of the present invention in which changes in the level of the control signal were measured when a code error existed in the transmission path under the same conditions as described above. (a) is a control signal waveform diagram when there is no code error, and (b) is a control signal waveform diagram when the code error is 10-8: (
In C), the sign error is 10-2. Although some deterioration of the reception S/H is seen, sufficiently accurate reception is possible even at 10-2 o'clock.

In the above description, a repeater inserted into an optical submarine cable was used as an example, but the present invention can also be applied to an optical fiber cable installed between land and land.

(3) Effects of the invention As explained above, the control command signal is transmitted in-service to each intermediate unit, and the clock frequency or phase of the transmitted signal is modulated by turning on and off the low-speed carrier, and
A carrier for transmitting a response signal from a repeater is created by dividing or multiplying the carrier transmitted from a terminal station, and by configuring a repeater monitoring system, the signal @
The reception S/N is stable against errors, and the S/N is stable even with multiple relays.
A highly stable monitoring system with small deterioration of /H can be realized.

Therefore, even when creating a loopback using a repeater as in the past, there is no need to use a signal or to install a standby system, so it is economical and the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional repeater monitoring system, FIG. 2 is a waveform diagram for explaining a conventional control command signal, and FIG. 3 is a waveform diagram for explaining a conventional response signal return method. Fig. 4 is a spectrum diagram of a conventional control command signal, Fig. 5(a),
(b) is a block diagram of a transmitting terminal station that sends out a control command signal according to the present invention, FIG. 6 is a block diagram that detects a control command signal according to the present invention, and FIG. FIG. 8 is a block diagram of control command signal detection in synchronous detection according to the present invention, and FIG. 9 is a diagram showing the relationship between the number of relays and received S/N when phase modulation according to the present invention is used. The relationship diagram, FIG. 10, shows the measurement results of the control command signal according to the present invention. 1...Landing station, 2.2...Optical fiber, 3...
Medium R relay type, 11. 11'... Transmitting terminal station, 12... Control command generator, 13... Receiving terminal station, 14... Response signal demodulator, 31. 31R...Regenerative relay circuit, 32.32
'... Control command receiving circuit, 33... Subcarrier regeneration circuit, 34... Response signal creation circuit, 35, 112.
... Premodulation circuit, 36 ... Loopback creation circuit, 3
7... Frequency conversion circuit, 110... Phase modulation circuit,
111...Carrier generation circuit, 113...Frequency modulation circuit, 320...Amplifier, 321...Delay circuit,
322...attenuator, 323...multiplier, 324...
・Band pass filter (BPF), 325... Control command signal detection circuit, 326... Phase locked loop (PLL)
), 327... Synchronous detection circuit. Figure 2 U Figure 3, y2. Fig. 4 r''-----------------
Meng--L------------" Figure 6 Figure 7 mercen f! , Sad Figure 8 SWR Figure 9 Figure 10 Saiji Gogon Juushiri's Δ Shi 1 F Death 4 To Sign Rust 10'' 8 yh 2 Too N No. Book June 19, 1980 Commissioner of the Japan Patent Office Black 1) Mr. Yu Aki 1, Indication of the incident 1988 Patent Application No. 95447 2, Name of the invention Repeater monitoring system for optical digital transmission line 3, ?iti correction Relationship with the patent case Patent applicant address 2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name 1
21 International Telegraph and Telephone Co., Ltd. 4, Agent 105 Address 1-20-11-6, Nishi-Shimbashi, Minato-ku, Tokyo Subject of amendment Column 7 of the scope of claims of Mei Mizan Contents of amendment Description [Patent Scope of claims] 4 levers ≧, /, /'1-・ We will make the corrections as shown in the attached sheet. °2. Claims: A repeater monitoring system for an optical digital transmission line having upstream and downstream optical fibers provided between two terminal stations and a repeater inserted into the optical fibers, A control command signal in the form of a low-speed binary code that controls operating conditions etc. is keyed to a carrier wave that is lower in speed than the transmission speed at which the communication signal is transmitted, and the communication signal is phase-modulated or frequency-modulated using the keyed carrier wave. By doing so, a transmission signal in which the control command signal and the communication signal are superimposed is transmitted to the optical fiber, and the repeater detects the received transmission signal and detects the control command signal. A second signal obtained by converting the frequency of one of the carrier wave or a carrier wave for transmitting a response signal transmitted from the terminal station using the response signal created using the low-speed binary code for repeater information. A relay for an optical digital transmission line, characterized in that the keyed second carrier wave is used to phase-modulate a communication signal received from another repeater, and the signal is sent back to the terminal station. equipment monitoring method. ”

Claims (1)

[Claims] In a repeater monitoring system for an optical digital transmission line that has optical fibers for upstream and downstream transmission lines provided between two terminal stations and a repeater inserted into the optical fibers, a low-speed method that controls the operating status of the repeater is used. By keying a carrier wave having a lower speed than the transmission speed at which the binary code control command signal transmits the communication signal, and performing phase modulation or frequency modulation of the communication signal with the keyed carrier wave, the control command signal is obtained. A transmission signal obtained by superimposing the transmission signal and the communication signal is transmitted to the optical fiber, and the repeater detects the received transmission signal to detect the control command signal, and then transmits the desired repeater information to the low-speed A second carrier wave obtained by frequency converting the carrier wave or the carrier wave for transmitting the response signal transmitted from the terminal station with a response signal created with a binary code is keyed, and the keyed second carrier wave is then keyed. A repeater monitoring system for an optical digital transmission line, characterized in that a communication signal received from another repeater is phase-modulated using a carrier wave and sent back to the terminal station.