Optical signal receiver and optical space transmission system

Abstract

An optical signal receiver comprising an opto-electric converter for converting an optical signal transmitted from a remotely opposed transmitter into an electric signal, a reproduction circuit for reproducing a data signal from an output of the opto-electric converter, a fixed signal generation circuit for generating a fixed signal having a logic level fixed to 0 or 1, a switch for selectively outputting either the data signal reproduced by the reproduction circuit or the fixed signal generated by the fixed signal generation circuit, and a control circuit for detecting an abnormal state of optical signal transmission and controlling the switch. The control circuit is adapted to output the fixed signal from the switch, when it detects the abnormal state while outputting the data signal from the switch. The optical signal receiver constitutes an optical space transmission system with transmitter for transmitting an optical signal.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to an optical signal receiver for detecting optical signals transmitted from a remotely opposed transmitter and also to an optical space transmission system comprising such a receiver and adapted to convey information to it. [0003] 2. Related Background Art [0004] With a conventional optical space transmission system, a signal to be transmitted from a transmitter is modulated into an optical signal, which is then transmitted from the transmitter to a receiver by way of the atmosphere. Upon receiving the signal, the receiver demodulates the optical signal transmitted from the transmitter so that the information that the signal represents can be conveyed from the transmitter to the receiver by way of the atmosphere. [0005] However, an optical space transmission system using a light beam as an optical signal has a disadvantage that the optical signal can be affected and attenuated by natural phen...

AI Technical Summary

Benefits of technology

[0008] In view of the above identified circumstances, an object of the present invention is to provide an optical signal receiver and an optical space transmission system that can minimize the influence of any abnormal transmission of an optical signal on the computer network devices connected to the system by suspending the output of the received signal that may be incorrect so that the proper operation of the entire transmission system can be restored quickly.

Problems solved by technology

However, an optical space transmission system using a light beam as an optical signal has a disadvantage that the optical signal can be affected and attenuated by natural phenomena such as rain falls and fogs in the atmosphere.

When abnormal communications arise in such a conventional space transmission system due to a natural phenomenon such as a rain fall or a dense fog in the atmosphere operating as transmission paths of light beams, some of the optical receivers of the system may be forced to keep on outputting incorrect signals as long as the natural phenomenon continues.

Then, even if the optical space communication is returned to normal during the initialization, the device cannot resume its operation at least during the initialization period.

Additionally, when an optical transmission system has backup routes so that some or all of the transmission paths for optical signals in an optical transmission system may be switched to respective wired transmission paths when abnormal communications arise on those transmission paths, the computer network devices connected to the switched transmission paths cannot decide to switch the transmission path on the basis of the presence or absence of a bit stream received from the optical receiver so that they are often accompanied by a problem of difficulty of switching the transmission path and an interrupted telecommunication.

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