JP5236179B2 - Line quality confirmation device for optical signal transmission system - Google Patents

Description

  The present invention relates to an optical communication system, and more particularly to a line quality confirmation device for an optical signal transmission system for confirming optical line quality in an optical cable section.

  In mobile communication, a radio signal amplifying apparatus including a radio signal (RF signal) amplifier is used to transmit radio waves to a mobile terminal apparatus or receive radio waves from a mobile terminal apparatus. Yes. However, in insensitive areas where radio waves are difficult to reach, such as in tunnels, underground malls, and buildings, wireless communication is basically not possible. Therefore, optical fiber cables and optical conversion type radio signal relays are used as countermeasures for insensitive areas for wireless communication. An optical signal transmission system composed of an amplifier is used. In this optical signal transmission system, an electrical signal from a modulation / demodulation device is converted into an optical signal by an optical conversion type radio signal relay amplification device, and then transmitted by an optical fiber, and the optical conversion type radio signal relay amplification device in a dead area Thus, an optical signal is converted into an electric signal and wirelessly transmitted to the mobile terminal device.

  As shown in FIG. 3, a general schematic configuration of such an optical signal transmission system is as follows: a master station device 15 of an optical conversion type wireless relay amplification device that transmits and receives signals to and from a modem device; Optical fiber cables 1 and 2 are connected to a terminal device and a slave station device 16 of an optical conversion type wireless relay amplification device that transmits and receives signals. The master station device 15 includes a band-pass filter 3 that passes only a target frequency band with respect to a downstream signal, an amplifier 4 that amplifies the signal, and an electric-to-optical converter (E / E) that converts the electric signal into an optical signal. O) 5, an optical-electrical converter (O / E) 8 that converts an optical signal into an electrical signal with respect to an upstream signal, an amplifier 7 that amplifies the signal, and an attenuator 13 that performs level adjustment. The bandpass filter 6 is configured to pass only the frequency band. On the other hand, in the slave station device 16, an optical-electrical converter (O / E) 9 that converts an optical signal into an electrical signal for a downstream signal, an amplifier 10 that amplifies the signal, and an attenuator 13 that performs level adjustment are provided. A band-pass filter 11 that passes only the frequency band of interest, a band-pass filter 14 that passes only the frequency band of interest for the upstream signal, an amplifier 10 that amplifies the signal, and an electrical signal as an optical signal It comprises an electro-optical converter (E / O) 12 for conversion.

  Now, when the downstream signal from the modem is input to the master station device 15 by a cable or the like, the input signal is passed through only the frequency band targeted by the device by the band pass filter 3 and amplified by the amplifier 4. The optical signal is converted into an optical signal by an electro-optical converter (E / O) 5 and transmitted through the optical fiber cable 1. Thereafter, the optical signal is converted into an electric signal by an optical / electrical converter (O / E) 9 in the slave station device 16 and then amplified by an amplifier 10. The level of the electric signal is adjusted by an attenuator 13 and a band pass filter. 11 to the antenna or the like. Similarly, the upstream signal passes through the band-pass filter 14 after the electrical signal from the antenna or the like is amplified by the amplifier 13 and converted into an optical signal by the electrical-to-optical converter (E / O) 12 to be an optical fiber cable. 2 is transmitted. This optical signal is converted into an electric signal by an optical / electrical converter (O / E) 8 in the master station device 15, then amplified by the amplifier 7, the level of the electric signal is adjusted by the attenuator 13, and the band pass filter 6. Is passed to the modem via a cable or the like. In such an optical signal transmission system, an optical distributor is generally provided in the master station device 15 so that a plurality of slave station devices 16 can be connected, and it is possible to cover a dead area.

  By the way, in such an optical signal transmission system, the line quality confirmation in the optical cable section in which the optical fiber cables 1 and 2 are laid is performed by testing the loss of the optical fiber cables 1 and 2 using OTDR (0 optical Time Domain Rejectometers) or the like. The method is common. This OTDR test method measures the optical power backscattered from different locations in an optical fiber cable by measuring from a single direction over the entire length of the optical fiber cable. At the connection part or the like, light reflection occurs at that point, and the reflection point or the like is measured. Another method for checking the line quality is to measure the bit error rate. For example, as an information exchange means between the master station device and the slave station device, there is one using a modem 21 as shown in FIG. 4, and here, in the case of transmitting data from the master station device side to the slave station device side. Information exchange means will be described. First, data to be transmitted in advance to the slave station device 16 side is stored in the RAM 19 on the master station device 15 side. Next, the data stored in the RAM 19 is read from the CPU 17 by the program stored in the ROM 18, and the data is transferred to the line controller 20. Inside the line controller 20, the data inputted as parallel data is serially converted and serially transferred to the modem 21 in time series at a determined transfer rate. The data input to the modem 21 is analog-modulated and input to the electro-optical converter (E / O) 5 via the band pass filter 3 and the amplifier 4. The optically converted data is transmitted to the slave station device 16 via the optical fiber cable 1. The optical signal received on the side of the slave station device 16 is converted into an electric signal by an opto-electric converter (O / E) 9 and amplified by an amplifier 10, and a modem signal is extracted through a band-pass filter 11. 21 is input. Data input to the modem 21 is digitally demodulated from analog data and input to the line controller 20. The input data is stored in the RAM 19 by a program in the ROM 18 and a command from the CPU 17. This accumulated data is used as necessary information in the slave station device 16. In this way, data is transmitted from the master station device 15 side to the slave station device 16 side, but data transmission is also performed from the slave station device 16 side to the master station device 15 side in the same procedure (for example, Patent Document 1). See).

JP-A-9-181822

  However, in the conventional method for measuring the bit error rate in the line quality confirmation device of the optical signal transmission system, the bit error rate measuring device is headed to the place where the optical fiber cable is laid, and the master station device 15 side and the slave station device 16 are connected. Because it is necessary to connect this between the line controller 20 and the modem 21 on the side, and to open and operate the storage case doors on the master station device 15 side and the slave station device 16 side, it cannot be measured easily. It spends a lot of work time and effort.

  An object of the present invention is to confirm the line quality of an optical signal transmission system in which a line quality can be measured by a simple method without bringing a bit error rate measuring equipment to a place where an optical fiber cable is laid. To provide an apparatus.

  In order to achieve the above object, the present invention provides an optical fiber cable between a master station device that converts an electrical signal into an optical signal and transmits it and a slave station device that receives the optical signal and converts it into an electrical signal. In the line quality confirmation device of the optical signal transmission system configured to connect and confirm the line quality of the optical fiber cable, the optical fiber cable line is switched to the bit error rate measurement mode from the normal communication mode to the master station apparatus. A maintenance terminal device that gives an instruction to measure the bit error rate is always connected, and the line quality is confirmed based on the bit error rate measurement result output from the maintenance terminal device.

  According to the line quality confirmation device of the optical signal transmission system according to the present invention, it is required for the BER measured via the optical fiber cable and the actual analog line signal in accordance with an instruction from the maintenance terminal device connected to the master station side. The quality of the analog line can be evaluated from the correspondence with the quality index, and when measuring BER, go to the place where the optical fiber cable was laid as before and bring in large equipment for BER measurement Eliminates complicated work such as connecting to the line, and easily measures the BER using the maintenance terminal device, master station device and optical fiber cable that have already been installed, and easily grasps the line quality when the quality deteriorates Will be able to.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a line quality confirmation apparatus for an optical signal transmission system according to an embodiment of the present invention.
The master station device 15 and the slave station device 16 are connected by an optical fiber cable 1. The master station device 15 is provided with a port capable of serial communication such as a personal computer, and a maintenance terminal device 22 is provided in this port. Connected. The maintenance terminal device 22 is used to measure BER (Bit Error Rate) via the optical fiber cable 1, that is, (number of bits received by mistake) / (number of bits of transmitted data). Correspondence between the BER and the quality index (S / N ratio, etc.) required for the actual analog line signal is determined by logical calculation or simulation, and at least a pass / fail judgment threshold value is stored in advance for each transmission rate. The line quality of the analog line is confirmed by comparing the threshold value with the actual measurement BER.

  For this purpose, the maintenance terminal device 22 performs, for example, simple BER measurement using the BER measurement data shorter than usual periodically or irregularly between the master station device 15 and the slave station device 16. The means 23, the normal monitoring means 24 for monitoring the line quality while comparing the BER measured by the simple BER measuring means 23 with a preset threshold value, and the BER measured by the normal monitoring means 24 exceeds the threshold value. When the normal communication mode is temporarily terminated and the transition means 25 for automatically shifting to the BER measurement mode, the detailed BER measurement means 26 for performing a more accurate BER measurement using a sufficiently long BER measurement data, The BER measured by the detailed BER measuring unit 26 is displayed on the display unit together with the line quality threshold value, or has an output unit 27 or the like.

  Normally, polling is performed periodically or irregularly between the master station device 15 and the slave station device 16, and the maintenance terminal device 22 uses the simple BER measurement means 23 in the same manner, and the BER measurement is shorter than usual. BER measurement is performed more simply using the data for monitoring, and the line quality is monitored by the normal monitoring means 24 while comparing with the threshold value. However, when the BER measured by the normal monitoring unit 24 exceeds the threshold, the transition unit 25 of the maintenance terminal device 22 temporarily terminates the normal communication mode and automatically transitions to the BER measurement mode. The relay operation of the radio signal for mobile communication is stopped and the mode is shifted to a test mode state in which only the control signal is exchanged between the master station device 15 and the slave station device 16, and the detailed BER measuring means 26 is used for measuring a sufficiently long BER. Perform more accurate BER measurements using the data. The result is stored in the RAM 19 and then notified to a higher-level monitoring device by the output means 27 so that the line quality can be confirmed. Further, the result is stored in the RAM 19, and then the data stored in the RAM 19 in the master station device 15 when the maintenance staff goes to the site is sucked to the maintenance terminal device 22 side and displayed on the output means 27 at this time. The BER when the line condition deteriorates is grasped by silently monitoring the measured result.

  Accurate BER measurement by the detailed BER measurement unit 26 is performed by issuing a BER measurement start command to the master station device 15 by the transition unit 25 of the maintenance terminal device 22. Receiving this command, the master station device 15 shifts to the test mode state, and then passes the data to the line controller 20 shown in FIG. 4 so that the modem 21, the electro-optical converter (E / O) 5 and the optical fiber are transferred. A loop command is transmitted to the slave station device 16 via the cable 1. In the slave station device 16, this is stored in the RAM 19 via the optical-electrical converter (O / E) 9, the modem 21, and the line controller 20. The stored data is analyzed by a program in the ROM 18, and the slave station device 16 sets the line controller 20 on the slave station device 16 side to the loop mode and sets the slave station device 16 side in a loop state with respect to the master station device 15. Sends a command indicating that it has been changed.

  Next, in order to actually perform the BER measurement, the detailed BER measurement means 26 of the maintenance terminal device 22 uses the PN9 stage (511) pseudo-random pattern or the like as the BER measurement data and sends it to the master station device 15 side. . The data output from the master station device 15 enters the slave station device 16 via the optical fiber cable 1 and is looped back because the line controller 20 is in the loop mode. The data is again sent to the master station device 15 side. Returned. This data is input from the master station device 15 to the maintenance terminal device 22, and the detailed BER measurement means 26 of the maintenance terminal device 22 returns the returned data and the transmitted PN9 stage (511) simulation data. Compare with random patterns, etc., and check if there is any data corruption. This operation is repeated to continue the BER measurement.

  When the BER measurement is terminated, a BER termination command is sent from the maintenance terminal device 22 to the slave station device 16 via the master station device 15, the loop mode of the line controller 20 on the slave station device 16 is turned off, and the normal communication mode is set. Return to. At the same time, the output means 27 of the maintenance terminal device 22 calculates the total number of transmitted output bits and the total number of received error bits, calculates the BER, and stores it in advance on the display screen for each transmission rate. By displaying a threshold value for determining pass / fail and a BER of the current measurement result, the line quality of the analog line can be confirmed based on a comparison between the two.

  A command exchanged between the master station device 15 and the slave station device 16 such as a BER measurement start command has a minimum transmission rate, for example, ITU-T so that it can be transmitted and received without error detection or retransmission. Recommendation V. 21 FSK 300 bps is used, but with such a transmission rate, it takes a lot of time to perform BER measurement with sufficient accuracy on a high-quality line, so when there are few errors, gradually increase the transmission rate of BER measurement data. For example, V. 33 64QAM 14400 bps is preferable.

  In addition, although the BER measurement start command is given from the maintenance terminal device 22 here, there is another method in which a BER measurement start command is prepared in the master station device 15 in advance. In this case, the maintenance terminal device 22 shifts to the BER measurement start mode and displays the BER result, and other functions are provided on the master station device 15 side.

FIG. 2 is a flowchart showing the processing operation at the time of the above-described BER measurement.
When the master station device 15 receives the BER measurement start command from the maintenance terminal device 22 in step S1, the master station device 15 issues a loop command to the slave station device 16 as described above in step S2. Receiving this, the slave station device 16 changes the line controller 20 on the local station side from the normal communication mode to the loop mode in step S3. Thereafter, in step S 4, the master station device 15 transmits data to the slave station device 16 such as a PN9 (511) pseudo-random pattern stored in advance in the ROM 18. This data received by the slave station device 16 via the optical fiber cable 1 is looped back at the portion of the line controller 20 on the slave station device 16 side in step S5, and returned to the master station device 15 side again. On the master station device 15 side, a conveyor check with the transmission data is performed at step S6. If the data is different, the number of errors is counted up at step S8.

  In subsequent step S9, the master station device 15 determines whether or not a BER measurement end command has been received from the maintenance terminal device 22 side. As a result, if the BER measurement end command has not been received, step S4 is performed. Returning to PN9, the PN9 stage (511) pseudo-random pattern or the like is sent again to continue the measurement. On the other hand, as a result of the determination, when the BER measurement end command is received from the maintenance terminal device 22 side, the BER measurement mode is switched to the normal communication mode, and the total number of output bits transmitted in step S10 and the total number of received errors are BER is calculated and the result is output to the display screen of the maintenance terminal device 22 in step S11.

  According to such an optical signal transmission system, the BER measured via the optical fiber cable 1 in accordance with an instruction from the maintenance terminal device 22 connected to the master station device 15 side and the quality required for the actual analog line signal The analog line quality can be evaluated from the correspondence with the index, and when measuring BER, go to the place where the optical fiber cable was laid as before and bring in large-scale equipment for BER measurement to the line The complicated work such as connection is eliminated, and the BER is easily measured by using the maintenance terminal device 22, the master station device 15, and the optical fiber cable 1 that have already been installed, and the line quality when the quality deteriorates can be easily achieved. It becomes possible to grasp.

  In carrying out the present invention, the maintenance terminal device 22 uses the BER measurement data that is shorter than usual periodically or irregularly between the master station device 15 and the slave station device 16 as described above. A simple BER measuring means 23 for performing the monitoring, a normal monitoring means 24 for monitoring the line quality while comparing the BER measured by the simple BER measuring means 23 with a preset threshold value, and the BER measured by the normal monitoring means 24 When the value exceeds the threshold, the normal communication mode is temporarily terminated and the transition means 25 for automatically shifting to the BER measurement mode, and the detailed BER measurement for performing more accurate BER measurement using sufficiently long BER measurement data And a means for displaying the BER measurement result by the detailed BER measuring means on the display unit together with the line quality threshold value, and an output means 27. That. According to such a line quality confirmation device for an optical signal transmission system, simple BER measurement means 23 can perform simple BER measurement without adversely affecting the line in the normal communication mode, and the line quality is in a predetermined state. If it is worse, the normal communication mode can be temporarily terminated and more accurate BER measurement can be performed using the detailed BER measurement means 26. Therefore, more efficient BER measurement and line quality confirmation can be performed. Will be able to.

  The line quality confirmation apparatus for an optical signal transmission system according to the present invention is not limited to the one shown in FIG. 1 but can be applied to other ones.

It is a block block diagram which shows the outline of the line | wire quality confirmation apparatus of the optical signal transmission system by one embodiment of this invention. 3 is a flowchart showing a processing operation in the line quality confirmation device of the optical signal transmission system shown in FIG. 1. It is a block block diagram which shows the conventional optical signal transmission system. It is a block block diagram which shows the optical signal transmission system at the time of the conventional data exchange.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Optical fiber cable 3,11 Band pass filter 4,10 Amplifier 5 Electric-optical converter (E / O)
9 Opto-electric converter (O / E)
15 Master station device 16 Slave station device 17 CPU
18 ROM
19 RAM1
20 Line controller 22 Maintenance terminal device

Claims (1)

A base station apparatus that converts a downstream signal from an electrical signal to an optical signal and transmits and transmits an upstream signal from an optical signal to an electrical signal, and receives and converts a downstream signal from an optical signal to an electrical signal. An optical signal transmission comprising: a slave station device that converts a signal from an electric signal to an optical signal and transmits the optical signal, and an optical fiber cable that is connected to the master station device and the slave station device and communicates signals in a communication mode. In the line quality confirmation device of the system,
A maintenance terminal device that is always connected to the master station device is provided. The maintenance terminal device includes detailed BER measurement means for performing detailed BER measurement using the detailed BER measurement data, and BER measurement data shorter than the detailed BER measurement data. Has a simple BER measurement means for performing simple BER measurement using
The simple BER measurement means performs simple BER measurement on optical signal transmission via the optical fiber cable during the communication mode,
Compare the threshold value for a predetermined reference with the simple BER measurement result,
When the simple BER measurement result is larger than the threshold value, it is determined that the line quality is simply deteriorated, and the communication mode is temporarily interrupted.
When the communication mode is temporarily interrupted, the detailed BER measurement means uses the master station device and the slave station device to measure the detailed BER on the optical signal transmission via the optical fiber cable. And
Storing the measurement results and returning to the communication mode;
An apparatus for confirming the line quality of an optical signal transmission system.

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