International Standard Electric Corporation

Jeffrey G Farrington

Martin Chown

In a Sagnac effect optical fibre gyroscope, which uses a phase nulling photo detection technique to drive a feedback loop controlling one or more non-reciprocal elements connected in series with the coil, a commutating switch reverses the direction of propagation of oppositely directed beams of light directed through the coil and non-reciprocal elements. The null balance is detected as the absence in the photodetector output of any a.c. component in phase or out of phase with the commutation switching. This removes a source of systematic error occasioned by drift in optical parameters of unbalanced components.

Measurement of rotation rate using sagnac effect

In a Sagnac effect optical fibre gyroscope a commutating switch (SW) is included immediately before the Sagnac coil (C). Operation of the switch synthesises turning the coil upside down. This provides the advantages of producing an a.c. signal in response to a constant rotation rate and in certain arrangements remove a source of systematic error occasioned by drift in optical parameters of unbalanced components.

Measurement of rotation rate using Sagnac effect

In a repeater for use in an optical fiber data transmission system of the closed-loop type, the input and output transducers each have a component which, depending on its biasing conditions, can act as a photo-detector or as a light-emitter. One such device is a light-emitting diode, which if reverse-biased acts as a photo-detector. With suitable switching this enables the realization of a reversible repeater. During normal operation, the direction of transmission is reversed at the end of each message received by a remote terminal, a reply message being sent during this period of reversal, after which the remote terminal reverts to normal operation. In the event of an interruption in message reception as detected at a remote terminal, the reversal of transmission direction also occurs, so that a line break in effect converts the system to two 'one-way' systems.

Optical fiber repeater

In a closed-loop multiple data terminal data transmission system, each message includes in addition to a message portion, a prefix portion having at least the address of the terminal for which the message is intended. When such a message reaches a data terminal its address is checked, and if not for that terminal, the prefix and the message portions are repeated along the loop. If the message is for the terminal only the prefix is repeated along the loop, the message portion being retained at the intended terminal. The prefix with no attached message eventually reaches the originating data terminal where its arrival indicates that the message has reached its destination and that the loop is intact.

Data transmission systems

An optical fibre data transmision system in which some terminals at least act as repeaters for received data. Each terminal is allotted a specified transmission time. Terminals are provided with optical fibre by-pass arrangements in case a repeating terminal fails.

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Bishop's Stortford, United Kingdom

Jeffrey G Farrington