JP2000151659A - Optical communication system for remote monitoring - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a remote monitoring optical communication system for a river management system that periodically collects monitoring data and monitoring video information from a plurality of slave stations by polling, emergency data is transmitted from an arbitrary slave station. Provide a means to send at any time. SOLUTION: In the present invention, the main system communication means that the emergency communication data generated in the slave station is FM-modulated at different carrier frequencies, and the E / E of the slave station is a frequency-multiplexed wave together with the FM modulated wave of the main system communication. The above-mentioned problem is solved by modulating the light intensity of O and transmitting it to the master station. Also provided are means for directly modulating O / E with baseband digital pulses and multiplexing transmission with FM waves, and means for preventing collision when a collision occurs due to simultaneous access to the master station in emergency data communication.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication system for remote monitoring used for collecting monitoring information from a plurality of monitoring points in a wide area river management system and the like, and an emergency data communication independent of a main system communication by polling. The present invention relates to an optical communication system for remote monitoring that enables the communication.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 19, a data collection system in an optical communication system for remote monitoring of a river management system is installed at a master station in a central management center and at a plurality of monitoring points at remote locations. The slave stations are connected by optical cables.

In this system, a polling access method is used as an information collecting method, and a master station collects data of each observation point sequentially from a slave station in a predetermined order. In recent years, video information of monitoring points has been collected simultaneously with observation data. The period of this polling access varies depending on the scale of the system and the monitoring conditions, but is performed at a period of several minutes to several tens minutes.

[0004] Also, a format example of calling a slave station from a master station used in the polling access control is shown in FIG.
20.

[0005] The master station sequentially instructs the slave stations to collect data by designating an address from the polling access control section 104, and calls the polling response control sections (204, 204) of the slave stations.
224, 244) know from the address part of the polling access signal that the own station has been called, and return response data to the master station.

FIG. 20 shows an example of the order (sequence) when calling the slave stations in order of address from the master station. In this example, the address of the slave station is: address = '1' for the slave station 200, address = '2' for the slave station 220, address = '3' for the slave station 240, and address = '4' for the slave station 260. Have assigned.

FIG. 21 shows an access sequence diagram in a case where main system communication is performed by polling access between a master station and a slave station. In response to polling access from the master station, communication is performed in order with the slave station 220 after the slave station 200.

The polling access signal from the master station and the response data from the slave station both have the frequency F0 (for example,
The frequency is modulated by an FM (frequency modulation) modulator (105, 205, 225, 245) having a carrier frequency of 70 MHz).

An E / O (electrical-to-optical converter) is generated by the FM signal.
Is transmitted to the optical fiber transmission line, and the receiving side returns the optical signal to a baseband signal, and the FM demodulation section (10
3, 203, 223, 243) to reproduce the original data.

In this conventional method, as described above, the master station sends the slave station at predetermined time intervals in the order of the slave station addresses.
Signals data collection (polling access). When calling the slave station from the master station, by sequentially changing the address of the slave station and calling the slave station, the slave station of the corresponding address recognizes that the own station has been called and starts transmitting data. When the data transmission is completed, the access right is passed to the slave station in the next address order. In this way, the master station sequentially collects data from each slave station.

[0011]

As described above, in the conventional data collection method of the remote monitoring optical communication system in the river management system based on polling access, the master station 100 controls the system at all times. Even when an emergency communication need arises from a slave station, communication cannot be performed without waiting until the own station is accessed.

Also, if the polling access cycle is shortened to reduce this problem, communication that requires a certain amount of time, such as surveillance video and communication calls, which are collected simultaneously with the data in accordance with the polling cycle, will be hindered. Problems occur.

For this reason, conventionally, it was necessary to separately provide a transmission line for emergency communication.

It is an object of the present invention to provide an optical communication system for remote monitoring that realizes emergency transmission means by a simple method.

[0015]

Means for Solving the Problems To solve the above problems, an FM modulated wave having a carrier different from the carrier frequency of the FM modulated wave used in main system communication or a baseband pulse wave is used. , Send emergency communication data.

E / O using waves multiplexed with main system communication data
Is modulated on the optical transmission line, transmitted to an optical transmission path, demodulated into an electric signal on the receiving side, and then separated by a filter to solve the problem.

FIG. 1 is a block diagram of a first embodiment.
The FM modulators 206 and 226, which perform FM modulation of emergency communication data at a carrier frequency F1 different from the carrier frequency F0 of the base band used for the main system communication, are received from each of the slave stations, and the master station side receives from the slave station. Demodulation unit 10 for demodulating the FM modulated wave
8 is provided.

The slave station multiplexes an emergency communication data signal FM-modulated at the carrier frequency F1 and an FM-modulated signal for main system communication used for polling access and response. The intensity is modulated and sent to an optical fiber, and the master station separates using the difference in the used frequency band.

As the different carrier frequencies, interference is a problem in consideration of the center frequency F0 of the FM modulation signal for main system communication and the modulation band determined by the transmission speed of the data signal, the modulation index of the FM, the transmission waveform shaping, and the like. Any value can be selected as long as the frequency is not required.

Thus, the emergency data communication can be performed at an arbitrary time when the need arises independently of the polling access / response signal.

FIG. 4 is a configuration diagram according to a second embodiment that enables emergency data transmission from an external device. An interface with an external device is provided in the emergency data communication FM modulators 206 and 226 in the slave station, and emergency communication data from the external device is input.

Thus, from any slave station, for example,
Temporary emergency communication data using a portable device as an external device, such as in a disaster, can be transmitted to the master station.

FIG. 6 is a system configuration diagram according to a third embodiment that enables multiple polling access.
The master station and each slave station are provided with an FM modulator and an FM demodulator having a carrier frequency F1 different from that for the main system communication, and the FM modulator is connected to an external device of the master station and each slave station via a connection interface unit. , An FM demodulator, and FM-modulates polling data from an external device, and frequency-multiplexes the FM-modulated wave of main-system communication data.

Thus, the polling access communication between the master station and the external devices connected to each slave station can be performed simultaneously with the main system polling access communication.

FIG. 8 is a system configuration diagram according to a fourth embodiment for realizing emergency data communication by direct light intensity modulation of the O / E conversion unit using digital pulses. E / O (Electro-optical converter) directly with digital pulse instead of transmitting emergency data communication by FM modulated wave of carrier frequency F1
To modulate the light intensity.

The receiving side receives the emergency communication data by converting the optical signal into an electric signal and then separating the digital pulse with a low-pass filter. As a result, a configuration using inexpensive general-purpose digital LSI components becomes possible.

FIG. 11 relates to the fifth embodiment, and relates to an improvement of the configuration of FIG. 1. In FIG. 1, a collision occurs when access from a plurality of slave stations simultaneously performing emergency data communication collides with the master station. Propose preventive measures.

When a collision occurs, the collision can be prevented by mutually adjusting the retransmission delay time by a timer so that data is retransmitted with a delay time predetermined for each slave station.

FIG. 16 relates to the sixth embodiment. In the case where the number of slave stations is large in the fifth embodiment, if data is retransmitted with a predetermined delay time when a collision occurs, the slave station having a large delay time may be retransmitted. This is a system configuration plan that solves the problem of slow access.

In the present invention according to claim 6, the value of the retransmission timer is automatically adjusted according to the size of the time until the next polling access while monitoring the access order information of the polling access.

The basic idea is that the delay timer value of the slave station that performs polling in the next order is maximized, and the slave station that is currently being polled and has the maximum waiting time until the next polling access is maximized. The timer value is set to the minimum, and the timer values of the other slave stations are set by sliding to the intermediate values of the timer values of the two slave stations.

As a result, it is possible to suppress the occurrence of bias by the station in the retransmission delay time when a collision occurs.

As described above, by combining the frequency multiplexing technique in the baseband frequency domain and the light intensity modulation transmission technique, it is possible to easily add monitoring video and monitoring data by ordinary polling access to the main system communication. Thus, an optical communication system for remote monitoring that enables emergency data communication at any time is realized.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the detailed drawings. 1 to 3 show explanatory views of a first embodiment of the present invention. In FIG. 2, normal polling access by main system communication is performed according to the data format shown in FIG.
In the sequence shown in FIG. 21, polling access and data collection are exchanged between the master station and slave stations.

The data a of the polling access including the address of the slave station is FM-modulated by the FM modulator 105 using the frequency F0 as the carrier frequency, and the data a electrically FM-modulated by the E / O converter 101 is used. Perform normal light intensity modulation,
The signal is transmitted from the master station to all the slave stations through the optical fiber 300 for downlink signal.

The slave station 200 that splits the optical signal from the coupler 301
Converts the optical signal into an electric signal by the O / E converter 202,
A predetermined FM modulation bandwidth centered on is extracted by a band-pass filter, and the signal level is AGC (automatic gain adjustment circuit)
Then, the FM demodulation unit 203 demodulates the received data (a), and the polling response control unit 204 determines whether or not the own station is accessed by looking at the slave station address part of the received data.

When the polling response control section 204 recognizes that the station has been accessed, the polling response control section 204 outputs the response data b and, at the same time, converts the optical output control signal into an E / O conversion signal in order to output light from the E / O conversion section. The bias supply unit of the unit 201 is applied. This is because a DC bias value corresponding to the amplitude value of the FM modulation wave is supplied to the O / E unit. Also, switch section
207 is controlled by the switch control signal, and the contact is moved to the contact 1 side.

The data b is frequency-modulated by the FM modulator 205 at the carrier frequency F0.
The frequency is modulated at the carrier frequency F2 by the FM modulator 213,
Frequency multiplexed through a buffer amplifier and a multiplexing amplifier (additional amplifier), and an E / O converter 201 through a switch 207.
Is transmitted to the master station through the coupler 311 and the optical fiber 310 for the upstream signal. The switch unit 207 is a dual contact switch.

In the master station 100, upon receiving the optical signal, the O / E
The conversion section 102 converts the signal into an electric signal, extracts each FM modulation component having F2 as a carrier through the band filter 106 and F2 through the band filter 111, adjusts the signal level to a constant level by AGC, and performs polling access by the FM demodulation section 103. Is demodulated, and the FM demodulation unit 112
Demodulates the monitoring video signal and sends it to the display device.

When it is desired to transmit data c from the slave station 220 that has not been accessed (an example of a sequence is shown in FIG. 3),
The data c is FM-modulated by the FM modulator 226 using a frequency F1 different from F0, which is the transmission frequency of the master station 100, as a carrier, and the E / O converter is driven through the switch 207 to transmit an optical signal to the transmission path.

[0041] In this case, the slave station 200 to transmission path even during transmission, each light intensity-modulated optical signal in the FM-modulated wave of the carrier frequency F0, F ₁ is on the optical fiber is transmitted simultaneously.

In the master station, after being converted back to an electric signal by O / E conversion, the FM of the emergency data c is passed through the bandpass filter 107 of F1.
The modulated wave is separated, and the emergency data c is reproduced through the FM demodulation unit 108.

According to this configuration, data can be transmitted from the slave station at an arbitrary time independent of data collection by polling access performing main system communication.

FIGS. 4 and 5 show explanatory views of a second embodiment of the present invention. FIG. 4 is an overall system diagram, and FIG. 5 is a detailed circuit configuration diagram. The purpose of this embodiment is to cope with a case where an external device connected to the outside of the slave station makes an emergency data communication request.

In this case, as shown in FIG. 5, the contact 2 of the switch unit 207 is turned to the ON side by an optical output control signal from the external device, and the emergency communication data c from the external device is transmitted to the FM modulation unit 20.
In step 6, FM modulation of the carrier frequency F1 is performed.
, The signal is converted into an optical signal by the E / O converter and transmitted to the master station.

When the slave station 200 to which the external device requesting communication is connected at the same time as the polling access, the contact 1 of the switch unit 207 is also turned to the ON side, and the optical output control signal is added by the adding circuit 214. The light output is controlled by the addition. This is for adjusting the required DC bias value of the E / O converter based on the overlap of the FM multiplex in the time domain.

The E / O converter 201 is driven by the multiplexed signal of the polling response data b and the video signal and the emergency data c from the external device, each of which is FM-modulated at the carrier frequency F0, F2, F1, and the optical signal. And transmitted to the master station 100.

In the master station 100, after the O / E conversion section 102 returns the signal to an electric signal, the FM demodulation sections 103, 112, and 108 return the original polling response data b, the monitor video signal, and the emergency signal from the slave station external device. The communication data c is demodulated.

With this configuration, in the event of an emergency, emergency data can be transmitted from a nearby child station to the parent station using a portable device, independently of data transmission by polling access.

FIGS. 6 and 7 are explanatory diagrams of a third embodiment of the present invention. FIG. 6 is an overall system diagram, and FIG. 7 is a detailed circuit configuration diagram. In addition to regular data collection by normal polling access by main system communication, when a special type of data is to be collected by emergency data communication at another polling cycle in the event of a disaster, the master station 100 and each child It is an object of the present embodiment to enable polling access independent of main system communication with an external device connected to the station (multiple polling access).

As shown in FIG. 7, in order to enable access from the external device 410 connected to the outside of the master station 100 to the external device 420 of the slave station 200, data from the external device 410 is transmitted to the master station 100. e is subjected to FM modulation of the carrier F1 by the FM modulator 110, frequency-multiplexed with the data a which has been FM-modulated by the carrier F0 used for normal polling, and the E / O converter 101
And converts it into an optical signal and transmits it to the slave station.

The slave station 200 demodulates the data “a” in the FM demodulation section 203, passes the data “a” to the polling response control section 204,
Demodulates the data e and transmits it to the external device 420 through the interface unit 208.

As a result, even if the master station 100 and the slave station perform video monitoring and monitoring data collection by polling the main system communication at a long time period, for example, the externally connected device of the master station 100 and any slave station can be monitored. Tens of meters between external connection devices
It is also possible to perform high-speed polling at intervals of s, and it is possible to quickly collect data from an external device of the slave station.

FIGS. 8 to 10 show explanatory views of the fourth embodiment of the present invention. The purpose of this embodiment is to implement a standard pulse on the receiving side as an implementation means for emergency data communication by directly optically modulating the O / E converter with digital pulses and transmitting the digital pulses instead of the frequency multiplexing method by FM modulation. The purpose is to achieve economics through the use of a processing circuit and LSI.

In FIGS. 8 and 9, when the slave station 220 that is not accessed wants to transmit the emergency communication data c during the main system communication by the polling access, the optical output control unit 232 The data c is applied, the E / O conversion unit 201 is driven through the addition circuit 214, and the data is transmitted to the master station 100 as an ON / OFF light intensity modulation signal corresponding to the digital pulse.

The master station 100 receives the FM modulated / light intensity modulated wave from the slave station 200 performing polling access by the main system communication and the digital pulse / light intensity modulated wave from the slave station 220 using a composite wave. After the wave is converted back to an electric signal by the O / E converter, the signal is applied to the latch 123 and the comparator 124 through the low-pass filter 121 and the AD converter 122 of the data extractor 120.

The AD converter has a flash type AD.
Use the converter to always set the sampling clock application pin to 1
By doing so, the digital value of the pulse waveform of the data cycle on the transmission side based on the value of the DC component corresponding to the FM modulation wave can be easily extracted without using a special clock.

On the other hand, prior to the emergency communication, the polling access control unit 104 normally informs the start of the reception of the polling response data b from the slave station by the main system communication.
Then, the average level of the light of the FM modulation wave at the time of the main system communication is held by the latch unit 123, and is used as a zero level reference when a digital pulse is applied.

In this state, when the output of the AD converter 122 and the output of the latch 123 are compared by the comparator 124, the emergency transmission data c is extracted as a difference signal. This is shown in FIG.

FIGS. 11 to 15 show explanatory views of a fifth embodiment of the present invention. The purpose of this embodiment is the first embodiment.
While accessing 240 with the normal polling access procedure,
Addressing data discard due to interference error (see FIG. 13) when the unaccessed slave station 200 and slave station 220 transmit emergency communication data FM-modulated at the carrier frequency of F1 to the master station 100 at the same time. It is to be.

Polling access control section 104 of master station 100
Detects that an error has occurred in the emergency communication data obtained as a result of demodulation by the FM demodulation unit 108 due to a collision, and discards the data. Next, the master station 100 sets the data collision flag FE to 1 in the slave station call format shown in FIG.
Is returned to the slave stations 200 and 220. At this time, the address section stores the broadcast mode address (for example, 999
9) is specified.

The slave stations 200 and 220 determine that the respective emergency communication data c has been discarded from the data collision flag FE of the response data g, and that a plurality of slave stations including themselves are communicating based on the communication flag FC. Check. When the data collision flag (FE = 1) is received, each of the slave stations 200 and 220 waits until a predetermined time has elapsed by the timer units 216 and 236 (the slave station 200 waits for α hours, and the slave station 220 Retransmission is performed after the waiting time β hours). Thereby, collision avoidance is performed. The timing at this time is shown in FIG.

As described above, even when emergency data from a plurality of slave stations collide with the master station, the plurality of emergency communication data can be reliably transmitted to the master station due to the delay of the initial detection time and the retransmission delay time. Becomes possible.

FIGS. 16 to 18 show explanatory views of a sixth embodiment of the present invention. The aim of the present embodiment is that when there are many slave stations in the fifth embodiment, the maximum value of the timer length for preventing collision increases, and the timer length is set to a fixed value in advance,
An object of the present invention is to solve a problem that retransmission of a specific slave station having a large timer value is always delayed.

Therefore, in the present invention, as shown in FIG. 18, the timer setting section 219 uses the address section (A3 to A0) of the frame format of the main system communication which is polled and accessed.
To know the next slave station to be accessed.

The slave station that has learned that it will be accessed next can communicate by polling access without using the emergency sub-communication means, so the timer 236 sets the collision avoidance retransmission delay time to the longest value. I do.

The slave station that is currently being accessed sets the collision avoidance retransmission delay time of the timer 216 to the shortest value since the next polling access becomes longer one cycle later.

The other stations also set the retransmission delay time by sliding according to the order of each address according to the set values of the timer values of the two stations. This can be easily realized by sliding the value of the address counter of the timer memory of each slave station according to the address value to be accessed by polling and the address value of the own station.

Thus, when retransmission is performed to avoid collision of emergency data from a plurality of substations when the number of substations increases, only certain substations have a long waiting time during retransmission. Can be avoided.

According to the present invention, even when the number of slave stations is large, a highly reliable emergency data communication in which the retransmission delay time at the time of collision is set to an average value for each slave station becomes possible.

[0071]

As described above, according to the present invention, even a slave station that has not been accessed for polling has an effect on the master station independently of the main system communication without affecting the main system communication by polling access. Emergency data communication at the same time.

Also, using a single optical fiber transmission line,
A plurality of polling access systems having different polling access periods can be used simultaneously.

Further, according to the fifth and sixth aspects of the present invention, the effect of applying the present invention is high, for example, emergency data communication from a plurality of slave stations can be performed with high reliability.

[0074]

[Brief description of the drawings]

FIG. 1 is an overall system diagram of Embodiment 1 of an optical communication system for remote monitoring according to the present invention.

FIG. 2 is a detailed system configuration diagram including a monitoring video system according to the first embodiment.

FIG. 3 is a sequence diagram in the case where the slave station 220 transmits emergency data c while the slave station 200 is transmitting in the first embodiment.

FIG. 4 is a system diagram of an optical communication system for remote monitoring during emergency data multiplex transmission from an external device according to a second embodiment.

FIG. 5 is a detailed system configuration diagram including a monitoring video system according to a second embodiment.

FIG. 6 is a system diagram of an optical communication system for remote monitoring at the time of multiple polling access according to a third embodiment.

FIG. 7 is a detailed system configuration diagram including a monitoring video system according to a third embodiment.

FIG. 8 is a system diagram of an optical communication system for remote monitoring by digital pulse / FM multiplexing according to a fourth embodiment.

FIG. 9 is a detailed system configuration diagram including a monitoring video system according to a fourth embodiment.

FIG. 10 is an explanatory diagram showing a relationship between an optical level on a transmission line, a digital pulse, and an FM modulated wave in a fourth embodiment.

FIG. 11 is a system diagram of an optical communication system for remote monitoring with collision prevention according to a fifth embodiment.

FIG. 12 is a detailed system configuration diagram including a monitoring video system according to a fifth embodiment.

FIG. 13 shows a case where the child station 200 and the child station 220 are simultaneously set in the
FIG. 9 is a diagram for explaining a situation in which emergency communication data is transmitted to 0 and a collision occurs.

FIG. 14 illustrates a collision detection notification format from a master station with a collision detection notification function to a slave station used in a fifth embodiment.

FIG. 15 is an explanatory diagram in the case where the slave stations 200 and 220 retransmit to the master station after sequence adjustment in the fifth embodiment.

FIG. 16 is a system diagram of an anti-collision remote monitoring optical communication system with an automatic retransmission delay time adjusting function according to a sixth embodiment.

FIG. 17 is a detailed system configuration diagram including a monitoring video system according to a sixth embodiment.

FIG. 18 is a state transition diagram of a slave station timer with an automatic retransmission delay time adjustment function according to the sixth embodiment.

FIG. 19 is a system configuration diagram of a conventional optical communication system for remote monitoring.

FIG. 20 is an example of a format and a calling sequence used when a slave station is called from a master station in a conventional system.

FIG. 21 is an explanatory diagram of a sequence by ordinary polling access in a conventional system.

[Explanation of symbols]

 100 Master station 200, 220, 240 Slave station 101, 201, 221 E / O converter (electrical-optical converter) 102, 202, 222 O / E converter (optical-electrical converter) 103, 203, 223, 243 Carrier FM demodulation unit for frequency F0 104 Polling access control unit 105, 205, 225 FM modulation unit 106, 210, 230 for carrier frequency F0 Band filters 107, 209, 217 for center frequency F0 Band filters 108, 211, 218 for center frequency F1 , 238 FM demodulation section of carrier frequency F1 109, 208 Interface section with external equipment 110, 206, 226, 218 FM modulation section of carrier frequency F1 111 Band filter of center frequency F2 112 FM demodulation section of carrier frequency F2 120 Baseband Digital pulse data extraction section 121 Low-pass filter 122 AD converter 123 Latch section 124 Comparator 201, 221, 241 E / O (Electro-optical conversion section) 202, 222, 242 O / E (Opto-electric conversion section) 204, 224 244 polling response control unit 206 FM modulator 207, 207b, 227, 227b for rear frequency F1 Switch 212, 232 Optical output controller 213, 233 FM modulator for carrier frequency F2 214, 234 Adder circuit 216, 236 Timer 219, 239 Timer setting 300 , 310 Optical fiber transmission line 301, 311, 302, 312 Optical coupler

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04Q 9/00 321 H04B 9/00 K (72) Inventor Yasuaki Fujimura 3-chome in front of Hakata-eki, Hakata-ku, Fukuoka City, Fukuoka Prefecture 22-8 F-term in Fujitsu Kyushu Digital Technology Co., Ltd. (reference) 5K002 AA02 AA04 BA04 BA33 CA09 DA06 DA08 DA10 DA21 DA91 FA01 GA01 GA03 GA07 5K032 AA06 BA08 BA11 BA18 CA04 DA01 DA18 DB07 DB14 5K048 AA06 AA08 BA30 CA03 CA13 CB02 DA02 DC08 EA23 EB01 EB14 EB15 HA01 HA02

Claims (6)

[Claims] An optical communication system for remote monitoring comprising means for performing main system communication for collecting monitoring data and monitoring video information from a plurality of slave stations at regular intervals from a plurality of slave stations by a polling access control procedure. An FM modulator for FM-modulating emergency communication data at a carrier frequency different from that of the main system communication, a switch for combining and outputting an output signal of the FM modulator and a polling access response signal, and an output of the switch for each of the slave stations. The master station has a filter separation unit and an FM demodulation unit for separating and extracting the emergency communication data from the slave station separately from the main system communication data. An optical communication system for remote monitoring, wherein data communication can be performed at any time from any slave station independently of the main system communication by polling access. 2. The FM for the emergency communication in the slave station.
As input means to the modulating unit, there are interface means for applying emergency data from an external device, and a dual contact switch for synthesizing and outputting a polling access response signal by main system communication and the emergency external communication data signal to the O / E conversion unit at the same time. An optical communication system for remote monitoring, comprising: a polling access response and an emergency data communication from an external device of a slave station to a master station. 3. The configuration according to claim 2, wherein an external interface unit, an FM communication unit for emergency communication transmission, and an FM demodulation unit for emergency communication reception are provided in the master station, and the emergency communication is performed in the master station. An FM modulator for demodulation and an FM demodulator for emergency communication are connected to an external device of the master station via the master station external interface unit.
A demodulation unit is configured to be connected to an external device of the slave station via the slave station external interface unit, and between the external device connected to the master station and the external device connected to each slave station. An optical communication system for remote monitoring, wherein polling access communication is performed at an arbitrary period independent of polling access communication in main system communication. 4. The slave station according to claim 1, further comprising an E / O direct drive unit using digital pulses instead of the FM modulation unit, as the emergency data communication unit as an emergency data communication unit. And a means for combining the output of the driving means with an FM modulated wave for main system communication to drive and transmit an E / O conversion unit. The master station according to claim 1, further comprising: In place of the demodulation unit, there are provided filter means for separating a digital input pulse, and means for removing a level corresponding to an average light intensity by an FM modulated wave for main system communication from the digital input pulse and restoring binary digital data. An optical communication system for remote monitoring, characterized in that: 5. The configuration according to claim 1, wherein the polling response control section of the slave station newly has a function of setting a retransmission waiting time timer for emergency communication data, and the master station has a collision due to simultaneous access from a plurality of slave stations. Error detecting means and means for notifying the slave station of data discard due to collision, and means for detecting the data discard to the slave station. When the master station detects data discard due to collision, the slave station After the elapse of the waiting time set for each,
An optical communication system for remote monitoring, wherein an emergency communication data packet is retransmitted from each slave station. 6. The timer setting function according to claim 5, wherein the order of polling access control of the main system communication with respect to the plurality of slave stations is monitored, and the sub data communication of the slave station currently being polled is performed. The value of the retransmission wait delay timer when a collision occurs is minimized, the value of the retransmission wait delay timer of the next slave station to be accessed is maximized, and the timer values of the other slave stations are intermediate between these two values. An optical communication system for remote monitoring, characterized in that the values are automatically and sequentially slid and adjusted.