JP2523104B2 - Optical communication system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cableless optical communication system, and more particularly to a system for preventing generation of erroneous information on an optical communication line.

(B) Prior Art and Problems When information is transmitted and received by an optical communication system for performing cableless communication using the conventional communication light source, interference due to external factors occurring in the optical communication path (for example, optical communication path) Since there is no means to detect the interruption of the signal or the mixture of light waves of the same wavelength other than the purpose, etc., the deterioration of the information due to the interference cannot be prevented, and there is a problem in the reliability of the information.

(C) Object of the Invention In view of the above-mentioned conventional drawbacks, an object of the present invention is to provide an abnormality determination method and an erroneous information generation prevention method capable of detecting the presence or absence of interference in an optical communication path.

(D) Configuration of the invention In an optical communication system in which a plurality of light transmitting / receiving stations (1 ′, 2 ′) having a function of transmitting and receiving light waves form an optical communication path with a predetermined space therebetween, the optical communication path is Optical communication path (A) for information transmission as an upstream optical path, and the optical communication path (A)
At least one guard optical path (C) parallel to the optical communication path (C) is provided, and a monitor communication path (B) that constantly sends a pilot signal is provided as a downstream optical path, and light is received by the light receiving side of the optical communication path (A). An information determination signal obtained by comparing the received light level signal (P) with a threshold value within a normal range of the received light level value and an unmodulated received light level signal (P ') received through the guard optical path. An AND circuit (30 ') for ANDing a guard determination signal obtained by comparing the unmodulated received light level value with the upper and lower thresholds within the normal range is provided, and the AND circuit (30') is provided. ) Is provided, a gate (31) for blocking the reproduction information (27) of the optical communication path (A) is provided, and a light reception level signal (Q) of the monitor communication path (B) is set to a preset normal level. Upper and lower threshold values And an AND circuit (20) for detecting that any one of the threshold values is projected, and based on the output of the AND circuit (20), the optical transmitter (13, This is achieved by providing an optical communication system characterized by being configured to stop the light transmission of 13 ').

(E) Embodiments of the Invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a principle block diagram of an optical communication system according to the present invention.

The optical communication systems in the figure are roughly divided into a light transmitting section 1a and a light receiving section 1b.
The light transmitting / receiving station 1 and the light transmitting / receiving station 2a and the light receiving / receiving station 2 constituted by the light receiving section 2b constitute an optical communication system in which a light wave is transmitted and received mutually by a predetermined space.

In the figure, a light transmitting unit 1a of a light transmitting / receiving station 1 includes a storage unit 11 for storing information to be transmitted, a modulator 12 for superimposing the stored information as a modulation signal on a light wave, and a light transmitting unit for emitting a modulated light wave.
13 and a light transmitting lens 14, and the light receiving section 1b is a light receiving lens.
15, a photodetector 16 that photoelectrically converts the received incident light, a detection rectifier 17 that shapes the output of the photodetector 16, and a light reception level signal Q that is the output of the detection rectifier 17 is compared with a required threshold value 2. Further, it is composed of individual comparators 18 and 19 and an AND circuit 20 which takes the AND of the outputs of the respective comparators.

The light transmitting unit 2a of the light transmitting / receiving station 2 includes a light transmitting unit 21 and a light transmitting lens 22, and the light receiving unit 2b includes a light receiving lens 23, a light receiving unit 24 for photoelectrically converting the received incident light, and a light receiving unit. An information system is composed of a demodulator 26 that demodulates the output of 24 to obtain reproduction information 27 and a controller 32 that inputs the reproduction information 27 via a gate circuit 31.

Further, a detection rectifier 25 that shapes the output of the light receiver 24,
Two comparators 28 and 29 for comparing the received light level signal P, which is the output of the detection rectifier 25, with a required threshold value,
An AND circuit 30 that takes the AND of the outputs of the respective comparators.

In order to simplify the explanation, the transmitted light from the light transmitting / receiving station 2 to the light transmitting / receiving station 1 in this block configuration is not modulated. Of course, the light transmitting units 1a and 2a and the light receiving units 1b and 2b may have the same structure. However, the controller 32 of the light transmitting / receiving station 2 constantly drives the light transmitter 21 to continuously transmit light regardless of the occurrence of a failure in the optical path. Further, it is preferable that the transmitted waves of both stations have different wavelengths in order to avoid interference.

Next, the operation of the main part will be described. A light wave containing information transmitted by the light transmitting / receiving station 1 is incident on the light receiver 24 of the light transmitting / receiving station 2 and photoelectrically converted there. At this time, the received light level signal P, which has been converted to a direct current and is obtained from the detection rectifier 25, is compared with the comparators 28 and 29.
And a high level threshold value + V ₁ is applied to the input of the comparator 28 so that the output of the comparator 28 is inverted to the L level when the level value of the received light level signal P exceeds the threshold value + V _1. Connect to. A low level threshold value + V ₂ is applied to the input of the comparator 29, and the output of the comparator 29 is connected so as to be inverted to the L level when the level value of the received light level signal P becomes smaller than the threshold value + V ₂ . The threshold values + V ₁ and + V ₂ are set to required values within an allowable range with respect to the reception level value of the received light level signal P when the light is normally received.

Then, the outputs of the comparators 28 and 29 can be input to the AND circuit 30, and when the output of the AND circuit 30 becomes L level, the gate circuit 31 can be triggered to stop the output of the reproduction information 27. The outputs of the comparators 28 and 29 are also input to the controller 32 to monitor the level change.

In the above description, as long as the light transmitter 13 of the transmitter / receiver station 1 always emits a light wave of a constant level, the light reception level signal P of the transmitter / receiver station 2 always maintains a constant level in a state where there is no interference in the optical communication path A. It should be. By the way, if all or part of the optical communication path A is cut off due to an external factor, the light reception level value of the light reception level signal P also decreases corresponding to the degree of the cutoff, and the degree of this decrease is the threshold value. When it becomes smaller than + V ₂ , the output of the AND circuit 30 becomes L level and the output of the reproduction information 27 is stopped. In addition, when an undesired light wave of the same wavelength is mixed and received by an external factor, a beat phenomenon occurs between the light wave for the original communication and the amplitude of the composite wave corresponds to the phase difference. As the strength changes, the reproduced information 27 of the demodulated wave is affected by the change caused by the interference, and the reliability of that information is lost.

The light-receiving level value of the light-receiving level signal P also fluctuates according to the strength of the amplitude of the composite wave, and exceeds the threshold value + V ₁ or the threshold value + V _2.
The AND circuit 30 outputs the L level and the output of the reproduction information 27 is stopped to make it smaller. Therefore, it is possible to prevent erroneous occurrence of information transmitted from the light transmitting / receiving station 1 to the light transmitting / receiving station 2, but if this is left as it is, the light transmitting / receiving station 1 will not receive the optical communication path A.
It is not possible to know the occurrence of abnormalities, and the light transmitting station 1 continues to transmit light.

Therefore, a light wave for monitoring is transmitted from the light transmitter 21 of the light transmitting / receiving station 2 to the light transmitting / receiving station 1 via the light transmitting lens 22 using the monitor communication path B, and the light receiving lens 15 of the light transmitting / receiving station 1 is set. The light-receiving level signal Q, which is received by the light-receiving device 16 via the light-receiving device 16 and is photoelectrically converted, and obtained by the detection rectifier 17 which shapes this, is input in parallel to the comparators 18 and 19, respectively.

The received light level signal Q is the two comparators of the transmitter / receiver station 2.
28, 29 and the AND circuit 30 perform the same processing as the comparators 18, 19 and the AND circuit 20. When the output of the AND circuit 20 becomes L level, the light transmitter 13 is controlled to stop the light transmission. To configure.

If the optical communication system is configured as described above, since the optical communication path A and the monitor communication path B are arranged in parallel, the spatially moving object that interferes with the optical communication path A has a time difference. Also affects the monitor communication path B. If the monitor communication path B is disturbed even if the optical communication path A is normal, the AND circuit
The transmitter 13 is stopped by the L level output of 20, and the gate
Transmission of false information from 31 is blocked proactively. Even if the monitor communication path B is normal, if only the optical communication path A is disturbed, the gate 31 blocks the transmission of erroneous information.

Further, if the cause of the interference on the monitor communication path B disappears, the AND circuit 20 is always sent to the monitor communication path B.
Output becomes H level, and the light transmitter 13 starts light transmission.
Further, the transmitter / receiver station 1 stops the optical transmitter 13 so that the optical communication line A
Alternatively, it can be known that an abnormality has occurred in the monitor communication path B. It should be noted that this system also includes level abnormality detection due to a failure of each lens and each light receiver.

FIG. 2 shows a block diagram of an embodiment of the optical communication system according to the present invention. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals and their duplicate description will be omitted.

The block diagram of the optical communication system shown in FIG. 2 is roughly divided into a light transmitting / receiving station 1'comprising a light transmitting section 1a 'and a light receiving section 1b and a light transmitting section 2a.
And a light receiving / receiving station 2'comprising a light receiving portion 2b '.

Reference numeral 13 'in the light transmitting section 1a' is a non-modulated light transmitting device which is a demultiplexer of the light transmitting device 13 and is parallel to the optical communication path A of the lens 14 and the lens 23 arranged opposite to each other and in the same direction. The guard optical path C for transmitting unmodulated light is composed of the lens 14 'and the lens 23'. Even if there is a time difference in the guard optical path C, the guard optical path C is more effective than the interference of the spatially moving object with the optical communication path A. It can be blocked in advance and multiple paths can be provided.

Reference numeral 23 'is a lens, 24' is a photodetector for photoelectrically converting unmodulated light, and 25 'is a detection rectifier for shaping the output of the photodetector 24'. Using a comparator circuit of the light receiving portion 2b shown in FIG. 1 the 'received light level signal P unmodulated light obtained via the' wave rectifier 25, a comparator 28 and a low is applied to the threshold + V ₁ high level Comparator applied level threshold + V ₂
It is connected in parallel to the input terminals of 29 and 29, and the output of each comparator is input to the AND circuit 30 '.

Further, inputs the output to the AND circuit 30 'via the' comparator 29 applies a 'threshold + V ₂ lower level with respect to the received light level signal P is output of the detection rectifier 25 modulated light, an AND circuit Each input signal 30 'is also input to the control unit 32 to monitor the level change of each input signal. The setting criterion of the low level threshold + V ₂ ′ is the same as the low level threshold + V ₂ in FIG.

In such a circuit configuration, by appropriately selecting the arrangement of the guard optical path C with respect to the optical communication path A, it is possible to block the guard optical path C before an obstacle in the optical path blocks the optical communication path A. This makes it possible to detect the interference of the optical communication path A in advance and control the information transmission.

Therefore, when at least one abnormality of the optical communication path A and the guard optical path C is detected by the output of the AND circuit 30 ', the gate 31 is shut off to prevent the transmission of erroneous information, and
As in the case of the figure, even if there is a time difference, when the monitor communication path B is disturbed by a spatially moving object that causes disturbance, the output of the AND circuit 20 causes the light transmitter 13 and the light transmitter 13 'to be simultaneously operated. It can be stopped.

(F) Effects of the Invention As described in detail above, according to the optical communication system of the present invention, it is possible to prevent erroneous occurrence of transmission information in cableless optical communication.

[Brief description of drawings]

FIG. 1 shows a principle block diagram of an optical communication system according to the present invention, and FIG. 2 shows a block diagram of an embodiment of the optical communication system according to the present invention. In the figure, 1, 1 ', 2, 2'is a light transmitting / receiving station, 1a, 1a', 2a is a light transmitting section, 1b, 2b, 2b 'is a light receiving section, and A, B, C are communication paths using light, + V ₁ , + V ₂ , + V ₂ ′ indicate threshold values.

Claims (1)

(57) [Claims] 1. An optical communication system in which a plurality of light transmitting / receiving stations (1 ', 2') having a function of transmitting and receiving a light wave constitute an optical communication path with a predetermined space in between, and the optical communication path is upstream. An optical communication path (A) for transmitting information as an optical path, and at least one parallel to the optical communication path (A)
A guard optical path (C) of a book is provided, and a monitor communication path (B) for constantly sending a pilot signal is provided as a downstream optical path, and a light reception level signal (P) received at the light receiving side of the optical communication path (A) is provided. ) Is compared with a threshold value within the normal range of the received light level value, and an unmodulated received light level signal (P ') received through the guard optical path is received as the unmodulated received light. An AND circuit (30 ') is provided to take the AND of the guard judgment signals obtained by the upper and lower threshold values within the normal range of the level value, and the output of the AND circuit (30') is used to A gate (31) for cutting off the reproduction information (27) of the optical communication path (A) is provided, and further, a light reception level signal (Q) of the monitor communication path (B) is provided.
Is provided with an AND circuit (20) for detecting that any one of the thresholds is extruded by comparing each of the thresholds with the upper and lower thresholds of a normal level value set in advance. ), The light transmission of the light transmitters (13, 13 ') in the upstream optical path is stopped.