JPS60245324A - Optical communication system - Google Patents

Abstract

PURPOSE:To decide whether a disturbance exists in an optical communication line or not, and also to prevent the generation of error information by stopping a light transmission of a light transmitting station from a photodetecting station, by deciding to be abnormal, when a photodetecting level of the photodetecting station is shifted from a prescribed threshold. CONSTITUTION:In an optical communication system in which a light transmitting station 1 and a photodetecting station 2 is placed beyond an optical communication line A of a prescribed space, an incident light is converted photoelectrically by a photodetector 24 of a photodetecting station 2 and thereafter, shaped by a detecting rectifier 25, and a photodetecting level signal P is obtained. This photodetecting level signal P is inputted in parallel to comparators 28, 29, and compared and decided with thresholds V1, V2 of a prescribed level in a normal range of the photodetecting level signal. When one of its results is abnormal, it is decided that an abnormality is generated in the optical communication line A, by a controller 32, and sending of an optical signal from the light transmitting station 1 is stopped by sending a signal to a photodetecting part 1b provided on the light transmitting station 1 from a light transmitting part 2a provided on the photodetecting station 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a cableless optical communication system, and more particularly to a system for preventing the occurrence of false information on an optical communication path.

(bl) Prior Art and Problems When transmitting and receiving information using an optical communication system that performs cableless communication using a conventional communication light source, interference caused by external factors that occur in the optical communication path (for example, Since there was no means to detect interference (blocking, incorporation of unintended wavelengths of light, etc.), it was not possible to prevent information from being altered due to interference, and there was a problem with the reliability of the information.

(C1 Purpose of the Invention In view of the above-mentioned conventional drawbacks, the present invention aims to provide an abnormality determination method capable of detecting the presence or absence of interference in an optical communication path and a method for preventing the generation of false information.

(dl Structure and object of the invention) According to the present invention, in an optical communication system in which a plurality of light transmitting/receiving stations having light wave transmitting and receiving functions constitute an optical communication channel separated by a predetermined space, each light transmitting/receiving station is provided. When the received light level of a station exceeds a required darkness value, it is determined that there is an abnormality in the optical communication path, and the light receiving station stops transmitting light to the partner station corresponding to the abnormal light reception. This is achieved by providing an optical communication system.

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

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

The optical communication system in the figure is roughly divided into a light transmitting section 1a and a light receiving section 1.
A light transmitting/receiving layer 1, a light transmitting section 2a, and a light receiving section 2M composed of b.
The light transmitting/receiving layer 2 formed by the iron and the light transmitting/receiving layer 2 constitute an optical communication system that mutually transmits and receives light waves with a predetermined space between them.

In the figure, the light transmitting section 1a of the light transmitting and receiving layer 1 includes a storage section 11 for information to be transmitted, a modulator 12 that superimposes the stored information on a light wave as a modulation signal, and a light transmitter that emits the modulated light wave. 13 and a light transmitting lens 14, the light receiving section 1b includes a light receiving lens 15, a light receiver 16 that photoelectrically converts the received incident light, and a detection rectifier 17 that shapes the output of the light receiver 16.
and two comparators 18 that compare the received light level signal Q, which is the output of the detection rectifier 17, at a required darkness value.
．． 19, and an AND circuit 20 that ANDs the outputs of each comparator.

Further, the light transmitting section 2a of the light transmitting/receiving layer 2 includes a light transmitter 21 and a light transmitting lens 22, and the light receiving section 2b includes a light receiving lens 23,
A light receiver 24 that photoelectrically converts the received incident light, and a light receiver 2
a demodulator 26 that demodulates the output of 4 to obtain reproduction information 27;
An information system includes a controller 32 that inputs reproduction information 27 via a gate circuit 31.

Furthermore, there is a detection rectifier 25 that shapes the output of the light receiver 24, and two comparators 28 that performs a combalare I-convergence of the received light level signal P, which is the output of the detection rectifier 25, at a required darkness value.
．． 29, and an AND circuit 30 that ANDs the outputs of each comparator.

To simplify the explanation, it is assumed that the light waves transmitted from the light transmitting/receiving layer 2 to the light transmitting/receiving layer in this block configuration are not modulated.

Of course, the light transmitting sections 1a and 2a and the light receiving sections 1b and 2b may have the same configuration. However, it is preferable that the wavelengths of the optical waves transmitted by both stations are different to avoid interference.

Next, the functions of the main parts will be explained. The light wave containing information transmitted by the light transmitting/receiving layer 1 is incident on the light receiver 24 of the light transmitting/receiving layer 2 and photoelectrically converted there. At this time, the DC-converted received light level signal P obtained from the detection rectifier 25 is sent to the comparator 28.
and 29 in parallel, and comparator 2
A high level darkness value +v1 is applied to the input of the comparator 8, and the output of the comparator 28 is inverted to L level when the level value of the received light level signal P exceeds the threshold value +v1. Also, the input of the comparator 29 has a low level darkness value +v.
2 is applied, and the output of the comparator 29 is inverted to L level when the level value of the received light level signal P becomes smaller than the dark value +v2. It is assumed that the threshold values +Vl and +v2 are set to required values within the allowable range for the reception level value of the reception level signal P during normal reception.

Then, each output of comparators 28 and 29 is connected to an AND circuit 3.
0, and when the output of the AND circuit 30 becomes L level, the gate circuit 31 is triggered and the reproduction information 27 is input.
output can be stopped. The outputs of the comparators 28 and 29 are also input to a controller 32 to monitor level changes.

In the above explanation, as long as the light transmitter 13 of the light transmitting/receiving layer 1 always emits light waves at a certain level, the light receiving level signal P of the light transmitting/receiving layer 2 will also always emit a partial level when there is no interference on the optical communication path A. It should be maintained. By the way, if all or part of the optical communication path is blocked due to an external factor, the received light level value of the received light level signal P will also decrease corresponding to the degree of the blockage, and the degree of this decrease will be When becomes smaller than the dark value +v2, the output of the AND circuit 30 becomes L level and the output of the reproduction information 27 is stopped. Also, when an unintended light wave with the same wavelength is mixed in due to an external factor and is received, a beat phenomenon occurs between the light wave and the original communication light wave, and the amplitude of the composite wave will vary depending on the phase difference. As the strength changes, the reproduced information 27 of the demodulated wave is also affected by the changes due to interference, and the reliability of the information is lost.

Corresponding to the strength of the amplitude of the composite wave, the received light level value of the received light level signal P also fluctuates, and may exceed the dark value 10vI or become dark value +v.
Since the value becomes smaller than 2, the AND circuit 30 outputs the L level and output of the reproduction information 27 is stopped. Therefore, although it is possible to prevent the information from being erroneously transmitted from the light transmitting/receiving layer 1 to the light transmitting/receiving layer 2, the light transmitting/receiving layer 1 cannot detect the occurrence of an abnormality in the optical communication path.

Therefore, a light wave for monitoring is sent from the light transmitter 21 of the light transmitting/receiving layer 2 via the light transmitting lens 22 to the light transmitting/receiving layer 1 using the monitor optical path B, and then via the light receiving lens 5 of the light transmitting/receiving layer 1. The light receiver 16 receives the light and photoelectrically converts it, and the DC-converted light reception level signal Q obtained from the detection rectifier J7 that shapes the received light is input in parallel to comparators 18 and 19, respectively.

The received light level signal Q is sent to two comparators 2 in the light transmitting/receiving layer 2.
8, 29 and the AND circuit 30 are performed by the comparators 18, 19 and the AND circuit 20, and when the output of the AND circuit 20 becomes L level, the light transmitter 13 is controlled and the optical communication path A is The destination of the light transmitter 13 is stopped.

If the optical communication system is configured as described above, the optical communication path A
If an abnormality occurs in the monitor communication path B, the optical communication is stopped, and when the abnormal state of the monitor communication path B is recovered and the value of the received light level signal Q becomes normal, the optical communication can be automatically restarted. Note that this method also includes detection of level abnormalities due to failures in each lens and each light receiver.

FIG. 2 shows a block diagram of another embodiment of the optical communication system according to the present invention. In the top view, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and redundant explanation thereof will be omitted.

The block diagram of the optical communication system shown in FIG. 2 can be roughly divided into a light transmitting and receiving layer 1' consisting of a light transmitting section 1a' and a light receiving section 1b, and a light transmitting and receiving layer 2' consisting of a light transmitting section 2a and a light receiving section 2b'. It consists of

Reference numeral 13' in the light transmitting section 1a' is an unmodulated light transmitter obtained by branching the light transmitter I3.
A non-modulated optical path C parallel to the optical communication path A is composed of L lenses 14' and 23', and this non-modulated optical path C serves as a guard optical path for the optical communication path A, and a plurality of paths can be provided. Can be done.

23' is a lens, 24' is a light receiver for photoelectrically converting unmodulated light, and 25' is a detection rectifier for shaping the output of the light receiver 24'. Using the comparator circuit of the light receiving section 2b shown in FIG. It is connected in parallel to the input terminal of the comparator 29 to which the dark level value 10v2 is applied, and the output of each comparator is input to the AND circuit 30'.

Further, the output is sent to the AND circuit 30 through a comparator 29' to which a dark value +ν2', which is also low in ζ, is applied to the received light level signal P of the modulated light which is the output of the detection rectifier 25.
At the same time, each human input signal from the AND circuit 30' is also input to the control unit 32 to monitor level changes of each input signal. The setting criteria for the low-level darkness value +v2' are the same as for the low-level darkness value +v2 in FIG.

With such a circuit configuration, by appropriately selecting the arrangement of the guard optical path C with respect to the optical communication ImA, it is possible to block the guard optical path C before an object blocking the optical path blocks the optical communication path A. Therefore, interference with the optical communication path A can be detected in advance and the transmission of information can be controlled.

Therefore, an abnormality is detected by the output of the AND circuit 30', and the light transmitter 14.1 of the light transmitting/receiving layer 1', which is the other station of communication, is detected using the monitor communication path B explained in FIG.
4' can be stopped in advance.

([1) Effects of the Invention As described above in detail, according to the optical communication system of the present invention, it is possible to prevent erroneous generation of transmitted information in cableless optical communication.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical communication system according to the present invention, and FIG. 2 is a block diagram of another embodiment of the optical communication system according to the present invention. In the figure, l, 1', 2.2' are light transmitting and receiving layers, la,
la'. 2a is the light transmitting part, lb, 2b, 2b' are the light receiving part, A, B
, C is a communication path using light, 10v, , +v2. +y2
° indicates the darkness value. 1＼11no1no゛

Claims (1)

[Claims] In a block communication system in which a plurality of light transmitting/receiving stations having light wave transmitting and receiving functions are separated by a predetermined space and constitute an optical communication path, when the light receiving level of each of the light transmitting/receiving stations exceeds a required darkness value, the An optical communication system characterized in that it is determined that there is an abnormality in the optical communication path, and the light receiving station stops transmitting light to a partner station corresponding to the abnormal light reception.