JPH09107343A - Transmission method of line monitoring signal - Google Patents

Abstract

(57) [Summary] (Correction) [Problem] To provide a transmission method in which the influence of the main signal data on the line monitoring signal is reduced. SOLUTION: A transmitting side 10 time-division-multiplexes predetermined signal data with main signal data before superimposition of a monitoring signal, and a receiving side 5
At 0, the main signal data is time-division separated from the received data after the monitoring signal is extracted. The predetermined signal data are delay data and inversion data of the main signal data, data of all bits 0 and 1
Of the data, the alternating data of bits 0 and 1, the pseudo random signal data, and the inverted data of the pseudo random signal data, the mark ratio when multiplexed is 1 /
Selected to be 2. The receiving side includes a separation unit 52 that time-division-separates the reception data after the extraction of the monitoring signal, a pattern detection unit 81 that connects to a predetermined output channel of the separation unit to detect a specific fixed pattern signal, and a specific fixed pattern. A control unit 82 for changing and controlling the separation phase of the separation unit by not detecting the pattern signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line supervisory signal transmission system, and more particularly to transmission of a line supervisory signal in which a line supervisory signal having a lower frequency than that of digital main signal data is transmitted. Regarding the scheme. This type of signal transmission system is used for terminal stations, relay stations,
Further, it is suitable to be applied to a repeater of an optical / metal communication line laid on the land / sea bottom.

[0002]

2. Description of the Related Art FIGS. 10 and 11 are diagrams (1) and (2) for explaining a conventional technique. FIG. 10 shows a partial configuration of a conventional optical direct seabed amplification repeater system.
0 is an optical repeater, 11 and 21 are optical / electrical converters (OE), 1
3 and 23 are a signal reproducing / retiming unit (RT),
Reference numeral 25 is a modulator (MD), and 16 and 26 are electric / optical converters (E).
O), 17 and 27 are optical amplifiers (OA) using erbium-doped fiber, and 31 is a repeater monitoring controller (SV).
C), 32, and 33 are demodulation units (DM). Optical repeater 5
The same applies to 0.

Other optical repeaters or terminal devices (not shown) are connected to the other ends of the optical repeaters 10 and 50, respectively, for exchanging the main signal data MS via an optical fiber transmission line. In that case, a predetermined line monitoring signal S is added to the main signal data MS.
V is superimposed and transmitted, and the relay line and the relay are monitored by the signal SV. There are various methods for exchanging the line monitoring signal SV, one example of which will be described below.

In the optical repeater 10, the modulation section 15 performs optical intensity modulation of the main signal data MS reproduced by the signal reproduction / retiming section 13 with the monitoring signal SV from the repeater monitoring control section 31, and the optical repeater is provided. To the container 50. In the optical repeater 50, the demodulation unit 72 performs optical intensity demodulation of the component of the monitoring signal SV from the received hybrid main signal data HS and inputs it to the repeater monitoring control unit 71. Upon receiving this, the repeater monitoring control unit 71 returns a predetermined response signal RP, which is sent to the optical repeater 10 by the route opposite to the above.

In the optical repeater 10, the demodulation section 33 performs optical intensity demodulation of the component of the response signal RP from the received hybrid main signal data HS and inputs it to the repeater monitoring control section 31. In this way, the optical transmission line and the optical repeater are monitored / controlled. FIG. 11 is a diagram for explaining the problems of the conventional transmission method. FIG. 11 (A) shows a part of the conventional transmission signal (hybrid main signal data HS), which is nominally 622M.
For the main signal data MS having a constant light intensity at bps (corresponding to STM-4), the light intensity modulation of about several% is performed by the SV signal. As the SV signal, for example using a sine wave signal of 10M～12MH _Z, representing the bit information 1/0 the length / breadth of the modulation period T. As the response signal RP, for example using a sine wave signal of 2K～12KH _Z, and responds by continuous signal with a constant interval.

FIG. 11B is a diagram for explaining the modulation degree, which is defined by the modulation degree = (b / a) × 100%. In general, it is necessary to reduce the influence of the SV signal on the main signal data as much as possible. Therefore, the modulation degree is selected to be about several percent.

[0007]

FIG. 11C shows a power spectrum of a conventional transmission signal. If the center frequency of the main signal data MS is f ₀ , the frequency of the SV signal is selected to be sufficiently low. In this case, if the main signal data MS is monotonic 0/1 alternating data,
The signal spectrum has a sharp narrow band as shown by the dotted line in the figure. Therefore, the main signal data MS in this case is S
The signal for V is not affected, and the signal for SV can be demodulated with a high SN on the receiving side.

However, in general, the main signal data MS is random data, and particularly in the case of the NRZ code, since the long continuation of data 1/0 is included, the power spectrum of the main signal data MS is in the frequency band of the SV signal. Has spread to. Therefore, conventionally, the main signal data MS
Influences the SV signal as noise and causes deterioration of the SN of the SV signal.

An object of the present invention is to provide a line monitoring signal transmission system in which the influence of the main signal data on the line monitoring signal is reduced.

[0010]

The above-mentioned problem is solved by the structure shown in FIG. That is, the transmission method of the present invention (1) is
In the line monitoring signal transmission method in which a line monitoring signal having a lower frequency than this is superimposed on digital main signal data and transmitted, in the transmission side 10, predetermined signal data is added to the main signal data before the monitoring signal is superimposed. Time division multiplexing is performed, and the receiving side 50 time division demultiplexes the main signal data from the received data after the monitoring signal is extracted.

FIG. 1A shows a power spectrum of a transmission signal in the case of the present invention. The characteristic a shows the power spectrum of the main signal data before multiplexing, and the low-frequency component thereof is a large noise component with respect to the monitoring signal SV.
When predetermined signal data is time-division-multiplexed with this main signal data (in this example, time-division two-division), the center frequency of the multiplexed signal moves to approximately 2f ₀ . In this case, for example, the mark ratio of the main signal data is ½ on average due to scrambling processing.
Then, in general, it is possible to multiplex predetermined signal data such that the mark ratio becomes 1/2. As a result, the mark ratio of the multiplexed signal in this case becomes 1/2,
Therefore, the total signal power (total spectrum area) of the multiplexed signal is the same as that of the characteristic a before multiplexing.
That is, the power spectrum of the multiplexed signal develops like the characteristic b, and the influence of the low-frequency component on the monitoring signal SV is reduced to about 1/2 of the conventional value.

Therefore, according to the present invention (1), the influence of the main signal data on the line monitoring signal can be greatly reduced. Preferably, in the present invention (2), the predetermined signal data is delay data of main signal data, inverted data of main signal data, data of all bits 0, data of all bits 1,
It is at least one of the alternating data of bits 0 and 1, the pseudo random signal data, and the inverted data of the pseudo random signal data.

For example, in the case where one or more delay data of the main signal data are multiplexed, the main signal data is separated into all the channels of the separating section 52 on the receiving side 50.
The extraction process of the main signal data is easy. Further, in the case where the inverted data of the main signal data is multiplexed, the multiplexed signal is alternating data of 0 and 1, so that the spread of the spectrum of the multiplexed signal is significantly suppressed.

Further, when fixed pattern data such as data of all bits 0, data of all bits 1 or alternating data of bits 0 and 1 are multiplexed, the fixed pattern data can be easily detected on the receiving side. Further, it is possible to easily specify the separation channel of the main signal data multiplexed in a fixed relationship with these. Further, in the case where the pseudo random signal data and / or its inverted data are multiplexed, there is no correlation with the main signal data, so the influence on the line monitoring signal can be greatly reduced.

Further, preferably, in the present invention (3), the mark rate when the predetermined signal data is multiplexed is 1.
It is selected to be / 2. The delay data of the main signal data, the inversion data of the main signal data, the alternating data of bits 0 and 1, the pseudo data of the pseudo random signal data and the inversion data of the pseudo random signal data are signal data with a mark rate of 1/2. Even if these are independently multiplexed with the main signal data, it is effective.

Data of all bits 0 and all bits 1
If the data of (1) and (2) are multiplexed together, the mark ratio becomes 1/2 in the multiplexed signal. Also preferably, the present invention (4)
In the above, the receiving side 50 is connected to a separation unit 52 that time-division-separates the reception data after extracting the monitoring signal, and connects to a predetermined output channel of the separation unit 52 to detect a specific fixed pattern signal of the separation data. A pattern detection unit 81 and a control unit 82 that controls the change of the separation phase of the separation unit 52 when the pattern detection unit 81 does not detect a specific fixed pattern signal.
And

For example, it is assumed that the main signal data is multiplexed in the channel 1 of the multiplexer 14, the main signal data is inverted data in the channel 2, 0 data in the channel 3, and 1 data in the channel 4. On the receiving side 50 in this case, the pattern detection unit 81 uses the fixed channel signal “11
By not detecting "..."
Change the separation phase of. When the pattern detection unit 81 detects the specific fixed pattern signal “11 ...” On the separation channel 4, the main signal data is separated on the separation channel 1 at that time.

Further, in the present invention (5), preferably, the receiving side 10 is any one of the separation unit 52 for separating the reception data after the extraction of the monitoring signal by time division and each separation data output from the separation unit. And a pattern detection unit 81 that monitors the separated data output from the separation unit to detect a specific fixed pattern signal, and the pattern detection unit 81 detects the specific fixed pattern signal, The selection unit 83 is used to select separation data of a channel having a predetermined relationship with the detection channel.

In the case of the same setting as the above-mentioned present invention (4), for example, when the pattern detecting section 81 detects a specific fixed pattern signal "00 ..." On the separation channel 4, a specific fixation on the separation channel 1 at that time. The pattern signals "11 ..." Are separated, and the main signal data is separated in the separation channel 2 at that time. Therefore, the pattern detection unit 81 uses the selection unit 8
3, the channel 2 is selected and the main signal data is extracted.

According to the present invention (5), the control of the separation phase of the separation unit 52 can be reduced, so that the main signal data can be quickly extracted. Further, preferably, in the present invention (6), the separation data output from the separation unit is further time-division separated.
, And the pattern detection unit 81 detects the specific fixed pattern signal by monitoring the separation data output from the second separation unit.

For example, 0 is set in the separation channel 4 of the separation unit 52.
It is assumed that the alternating data “0101 ...” Of / 1 has been separated.
When this is further separated by the second separating unit 84, it is separated into 0 data and 1 data for which pattern detection is easy. Further, preferably, in the present invention (7), an arithmetic unit 85 for performing a predetermined logical operation on the separated data of one or more channels output from the separating unit is provided, and the pattern detection unit 81 outputs the output data of the arithmetic unit 85. It monitors and detects a specific fixed pattern signal.

For example, it is assumed that the pseudo random signal data is separated into the separation channel 3 of the separation unit 52 and the inverted data thereof is separated into the separation channel 4. For these, the calculation unit 85
Thus, for example, when an exclusive OR operation is performed, "11 ..." Data for which pattern detection is easy can be obtained at the output.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the same reference numerals indicate the same or corresponding parts throughout the drawings. FIG. 2 is a diagram showing a configuration of an optical repeater system according to an embodiment, in which 10 is an optical repeater, 12 and 22 are digital data demultiplexing units (DMX), and 14 and 24 are digital data multiplexing units ( MUX). The same applies to the optical repeater 50.

Hereinafter, the multiplexing unit 14 of the transmitting side 10 and the receiving side 5
Attention is paid to the operation of signal transmission with the 0 separation unit 52. The multiplexer 14 time-division-multiplexes predetermined dummy signal data DMY with low-bit-rate main signal data MS to form high-bit-rate transmission data. The modulator 15 superimposes the SV signal on the transmission data and sends it to the optical transmission line.

In this example, the case of the new synchronous hierarchy is taken as an example, and 622M (STM-4), which is the transmission rate of the trunk system, is multiplexed for four channels to obtain the transmission rate of 2.4G (STM-16). explain. In addition, since a signal having a transmission rate four times higher is transmitted, the spectrum of the SV signal band is 1
/ 4. The separation unit 52 time-division-separates the high-bit-rate received data HS after the SV signal extraction, and the low-bit-rate main signal data MS and predetermined dummy signal data DM.
Y is generated.

In this case, it is not necessarily decided in which separation channel the main signal data MS appears, and various extraction methods of the main signal data can be considered. Each case will be described below. FIG. 3 is a diagram for explaining the monitoring signal transmission system according to the first embodiment. FIG. 3A shows the basic configuration thereof, and in the figure, 41 is a bit shifter.

The bit shifter 41 delays the low bit rate main signal data (NRZ code) by n bits by the low bit rate transmission clock signal T1CK. In this case, the delay number n bits is selected to be approximately the same as the maximum number of consecutive 0s of the scrambled main signal data (for example, 128 bits). In the multiplexing unit 14, the channels C1,
Main signal data is input to C3, and delay data is input to channels C2 and C4. The multiplexing unit 14 has channels C1 to C1.
Each data of C4 is transmitted as a transmission clock signal T of a low bit rate.
The signals are multiplexed in the order of the channels C1 to C4 by the multiplexed clock signal T4CK having a frequency four times that of 1CK and transmitted as a high bit rate transmission signal.

The demultiplexing unit 52 demultiplexes the high bit rate received data into four channels C1 to C4 in order by the demultiplexing clock signal R4CK having a frequency four times that of the low bit rate transmission clock signal, and each low bit rate signal is demultiplexed into channels. C1
Output to C4. FIG. 3B shows an example operation timing chart. For example, if the phases of multiplexing and demultiplexing are matched, as shown in the figure, the channels C1 to C1 on the multiplexing side and the channels on the demultiplexing side are
The same data is obtained for C4. In this case, the main signal data is obtained from the channel C1 on the separation side.

However, the phases of multiplexing and demultiplexing are not always the same. For example, if the separation phase is delayed by 1 bit from the above, the delay data of the main signal is on the separation side channel C1, the main signal data is on the channel C2, and the channel C is on the separation side.
The delayed data of the main signal is output to 3 and the main signal data is output to the channel C4 separately. However, since the delay data of the main signal in this case is nothing but the main signal data, in this case as well, the main signal data is obtained from the channel C1 on the separation side. This relationship is the same even if the separation phase is delayed by 2 or 3 bits, and returns to the initial state when delayed by 4 bits.

According to the first embodiment, since the main signal data and the delay data thereof are multiplexed, the main signal data can be obtained on all channels on the receiving side regardless of the phase of multiplexing / demultiplexing. Therefore, the frame synchronization for extracting the main signal data is not necessary, and the main signal data can be taken out from an arbitrary channel of the separating unit 52, and the control and the configuration for extracting the main signal data are simple.

FIG. 4 is a diagram for explaining a supervisory signal transmission system according to the second embodiment. FIG. 4A shows the principle of the configuration. In the figure, 42 is a flip-flop (FF), 81 is a pattern detection unit (PD), and 82 is a separated phase control unit (SC). Flip-flop 42
Is inverted by the low bit rate transmission clock signal T1CK, and at its output terminal Q, alternating data of "0/1" is obtained.

In the multiplexing unit 14, channel C1 is main signal data, channel C2 is all "0" data,
Channel C3 has all "1" data, channel C3
The alternating data of "0/1" is input to. In this example,
Since 3/4 of the multiplexed signal is a fixed pattern and the periodicity of the fixed pattern does not appear in the frequency band of each SV signal, the influence on each SV signal can be significantly reduced.

On the receiving side, the pattern detection unit 81 detects the bit pattern "0101 ..." Of the "0/1" alternating data in the separated data of the channel C4. When the bit pattern cannot be detected for a predetermined period, the control signal C is output to the control unit 82, and the control unit 82 delays the separation phase of the separation unit 52 by one bit.

FIG. 4B shows an example of an operation timing chart. In this example, the phases of multiplexing and demultiplexing are initially out of phase, so that the channel C1 of the demultiplexing unit 52 has alternating data of "0/1", the channel C2 has main signal data, and the channel C3 has all "0". Data and all "1" data are separated into the channel C4.

In this case, the pattern detection unit 81 cannot detect the bit pattern of "0101 ..." From the channel C4, and accordingly, the control unit 82 delays the separation phase by one bit. Further, as a result, in the separating unit 52, channels C1 → C4, C4 → C3, C3 → C2 for each separated data.
The replacement of C2 → C1 occurs. As a result, the pattern detection unit 81 will now detect the bit pattern of "0101 ..." On the channel C4, and no further phase control will be performed. At this point, the main signal data is obtained in the channel C1 of the separation unit 52. Therefore, the frame synchronization signal is not necessary even in the second embodiment.

A selector 83 may be provided instead of the phase control by the control unit 82. In this case, the pattern detection unit 81 detects presence / absence of three patterns of “00 ...”, “11 ...”, and “0101 ...” for each of the channels C1 to C4 of the separation unit 52. Since the determination of no pattern can be made relatively quickly, the determination does not take time even when there are three patterns. Then, if the first selected channel is the main signal data, "0" is detected in the next channel.
A pattern of "0 ...", "11 ...", or "0101 ..." is always found. It is possible to easily determine which channel the main signal data is separated from from the channel number at this time and the found pattern. As a result, the selector 8
3 is selected to quickly extract the main signal data.

FIG. 5 is a diagram for explaining a supervisory signal transmission system according to the third embodiment. FIG. 5 (A) shows the basic configuration thereof, and in the figure, 84 is the second separation unit (D
MX). The configuration and operation on the transmitting side are the same as in the case of FIG. FIG. 5B shows an example operation timing chart.

In this example, the alternating pattern of "0101 ..." Appearing on the channel C4 of the separating section 52 is further separated by the separating section 84 into two patterns of "00 ..." And "11 ..." And these are divided into channels C41, C42. Respectively output to. The pattern detection unit 81 stops the phase control by the control unit 82 by detecting the two patterns at the same time. At this time, the main signal data is separated in the channel C1 of the separation unit 52.

The separating section 84 may be connected to the channel C2 of the separating section 52. In this case, the separating unit 84 regards the “00 ...” Patterns appearing on the channel C2 as “00 ...” And “0.
0 ... ”, and the channels C41 and C42 are separated.
Output to The pattern detection unit 81 stops the phase control by the control unit 82 by simultaneously detecting these two patterns, and at this time, the main signal data is separated in the channel C1 of the separation unit 52.

Similarly, the separating section 84 may be connected to the channel C3 of the separating section 52. In any of the above cases, the pattern detection unit 81 determines that “00 ...
Since it suffices to detect a simple fixed pattern of "...", the circuit configuration and control for the detection are simple.

In addition, even if the transmission line quality is deteriorated and the bit error rate becomes 1 × 10 ⁻³ or more, the channel C
The probability that the fixed pattern “00 ...” Of 41 includes bit 1 or the probability that the fixed pattern “11 ...” Of channel C42 includes bit 0 is 1 bit per 1000 bits. There is little possibility of false detection.

FIG. 6 is a diagram for explaining a supervisory signal transmission system according to the fourth embodiment. FIG. 6 (A) shows the basic configuration thereof, and in the figure 43 is an inverter circuit (I). In the multiplexing unit 14, channel C1 is main signal data, channel C2 is inverted main signal data,
Channel C3 has all "0" data, channel C4
The data of all "1" is input to each.

In this example, since the inverted data is multiplexed next to the main signal data, "1" is added to the multiplexed signal.
There is a high probability that the data will be alternating data of "0" or "01". Further, since the multiplexed data of the channels C3 and C4 is 0/1 alternating data having no periodicity other than the high transmission bit rate, there is no influence on the SV signal band. Therefore, an effect of significantly canceling the influence of the multiplexed signal on the SV signal band can be expected.

FIG. 6B shows an example of an operation timing chart. On the receiving side, when the pattern detection unit 81 detects the “11 ...” Pattern having the predetermined number of bits or more in the output data of the separation channel C4, the main signal data is separated in the channel C1 of the separation unit 52. Further, for example, when the pattern detection unit 81 is connected to the separation channel C3, when the pattern detection unit 81 detects a "00 ..." Pattern having a predetermined number of bits (for example, 129 bits) or more, the channel C1 of the separation unit 52. The main signal data is separated into.

In these cases, even if the transmission line quality deteriorates and the error rate becomes about 1 × 10 ⁻³ ,
The "11 ..." pattern or the "00 ..." pattern is not satisfied at the ratio of 1 bit to 1000 bits.
Pattern detection is fully possible. Of course, the forward protection control and the backward protection control of the phase synchronization may be used together as in the normal frame synchronization control.

FIG. 7 is a diagram for explaining the monitoring signal transmission system according to the fifth embodiment. FIG. 7 (A) shows the basic configuration thereof, and in the figure 44 is a pseudo-random signal generator. In the multiplexer 14, main signal data is input to the channel C1, pseudo random signal data is input to the channel C2, all "0" data is input to the channel C3, and all "1" data is input to the channel C4.

Since the pseudo random signal data has no correlation with the main signal data, the multiplexed signal data can be made into a more random signal. FIG. 7B shows an example operation timing chart. FIG. 8 is a diagram for explaining the monitoring signal transmission system according to the sixth embodiment. FIG. 8A shows the basic configuration.

In the multiplexing section 14, the main signal data is input to the channel C1, the first and second pseudo random signal data are input to the channels C2 and C3, and the alternating data of "0/1" is input to the channel C4. There is no correlation between the first and second pseudo random signal data, and the multiple signal data can be made into a more random signal.

FIG. 8B shows an example of an operation timing chart. FIG. 9 is a diagram for explaining the monitoring signal transmission system according to the seventh embodiment. FIG. 9A shows the principle configuration thereof, and in the figure, reference numeral 85 denotes an EX-0R circuit (EO) which is an example of an arithmetic unit. In the multiplexing unit 14, the main signal data is input to the channel C1, the pseudo random signal data is input to the channel C2, the delay data of the main signal is input to the channel C3, and the inverted data of the pseudo random signal is input to the channel C4.

In the present invention, various combinations other than the above combinations are possible, and the multiple signal data can be converted into more random signals. FIG. 9B shows an example operation timing chart. On the receiving side, EX-
The 0R circuit 85 takes EX-0R (exclusive OR) of the separated data of the channels C2 and C3 of the separating unit 52. Therefore, the output of the EX-0R circuit 85 is an all "1" data pattern.

When the pattern detection unit 81 detects the "11 ..." Pattern having a predetermined number of bits or more, the main signal data or the delay data of the main signal is separated into the channel C1 of the separation unit 52, and the channel C3 is separated. The delay data of the main signal or the main signal data is separated. Since the delay data of the main signal is none other than the main signal data, the separation phases can be quickly synchronized.

Various other units can be considered as the calculation unit 85. For example, “0101 ...” Pattern and “1010
… ”And AND with the pattern“ 0000… ”
A pattern is obtained, and when OR is taken, a "1111 ..." Pattern is obtained. Further, a complicated calculation of the separation pattern (complex pattern matching calculation, decoding calculation, parity check calculation, etc.) may be performed.

In each of the above embodiments, the line monitoring signal transmission system using the optical communication line is described, but the present invention is also applied to the line monitoring signal transmission system using the metal communication line. it can. Further, although the above embodiments have described the line monitoring signal transmission system by the repeater, the present invention is also applied to the line monitoring signal transmission system of each node (terminal station, relay station, etc.) configuring the communication network. it can.

In each of the above embodiments, the case where the transmission signal of high bit rate is modulated by the optical intensity (AM) by the SV signal is described. However, for example, the FM modulated SV signal is superimposed / separated. It may be configured. Although the preferred embodiments of the present invention have been described, it goes without saying that various changes in the configuration, control, and combinations thereof can be made without departing from the spirit of the present invention.

[0055]

As described above, according to the present invention, the influence on the line monitoring signal can be greatly reduced regardless of the bit rate of the main signal data. In this case, for example, in the case of application to an optical transmission line system, the circuit change of the device may be a simple logic change of the electric circuit. On the other hand, with regard to the optical system circuit, it suffices to develop high-speed bit rate components, and the optical components (0 / E, E / 0) can be unified into simple ones. Therefore, regardless of the transmission bit rate of the main signal data, the system can be commonly designed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram showing a configuration of an optical repeater system according to an embodiment.

FIG. 3 is a diagram illustrating a monitoring signal transmission system according to the first embodiment.

FIG. 4 is a diagram illustrating a monitoring signal transmission system according to a second embodiment.

FIG. 5 is a diagram for explaining a supervisory signal transmission system according to a third embodiment.

FIG. 6 is a diagram for explaining a monitoring signal transmission system according to a fourth embodiment.

FIG. 7 is a diagram illustrating a supervisory signal transmission system according to a fifth embodiment.

FIG. 8 is a diagram illustrating a monitoring signal transmission system according to a sixth embodiment.

FIG. 9 is a diagram for explaining a supervisory signal transmission system according to a seventh embodiment.

FIG. 10 is a diagram (1) for explaining a conventional technique;

FIG. 11 is a diagram (2) for explaining a conventional technique;

[Explanation of symbols]

 10 transmission side 14 multiplexing section 15 superposition section 50 reception side 52 separation section 72 extraction section 81 pattern detection section 82 control section 83 selection section 84 second separation section 85 arithmetic section

Claims (7)

[Claims] 1. A transmission method of a line monitoring signal in which a line monitoring signal of a lower frequency than that of digital main signal data is superimposed and transmitted, wherein a transmission side has a predetermined value in the main signal data before the superposition of the monitoring signal. Is a time-division multiplexed signal data, and the receiving side separates the main signal data from the received data after the monitoring signal is extracted by time-division demultiplexing. 2. The predetermined signal data includes delayed data of main signal data, inverted data of main signal data, data of all bits 0, data of all bits 1, alternating data of bits 0 and 1, pseudo random signal data and pseudo. 2. The line monitoring signal transmission system according to claim 1, wherein the random signal data is at least one of inverted data. 3. The transmission method of a line monitoring signal according to claim 2, wherein the predetermined signal data is selected so that the mark ratio when multiplexed is 1/2. 4. The receiving side includes a separating unit for time-division separating the received data after extracting the monitoring signal, and a pattern for connecting to a predetermined output channel of the separating unit to detect a specific fixed pattern signal of the separated data. 3. The line monitoring signal transmission system according to claim 2, further comprising a detection unit and a control unit that controls the change of the separation phase of the separation unit when the pattern detection unit does not detect a specific fixed pattern signal. 5. The receiving side includes a separation unit that time-division-separates the reception data after extracting the monitoring signal, a selection unit that selects any one of the separation data output from the separation unit, and a separation unit that separates the output of the separation unit. A pattern detecting section for monitoring data and detecting a specific fixed pattern signal, wherein the pattern detecting section causes the selecting section to detect the specific fixed pattern signal, and the channel having a predetermined relationship with the detection channel. 3. The transmission method of the line monitoring signal according to claim 2, wherein the separated data of (1) is selected. 6. A second separation unit for further time-division separating the separation data output from the separation unit, wherein the pattern detection unit monitors the separation data output from the second separation unit to detect a specific fixed pattern signal. 6. The transmission method of the line monitoring signal according to claim 4, wherein 7. A calculation unit for performing a predetermined logical operation on the separation data of one or more channels output from the separation unit, wherein the pattern detection unit monitors the output data of the calculation unit to detect a specific fixed pattern signal. The line monitoring signal transmission method according to claim 4 or 5, wherein: