Browse Prior Art Database

Fiber Sensor

IP.com Disclosure Number: IPCOM000059725D
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Korth, HE: AUTHOR

Abstract

This article relates to an optical sensor with a glass fiber. As shown in the figure, a light pulse is transmitted from a light- emitting diode (LED) through the fiber to an appropriate modulator M which may take the form of movable mirror, an interferometer or a fluorescent material. Depending on the value to be measured, such as the position of a mechanical component, a certain amount of light is reflected to the modulator and transmitted back to the LED. Thus, the LED alternately acts as a transmitter for a light pulse and, after a certain transmission delay, as a receiver. Accordingly, the LED input terminal is periodically switched to a sending terminal S and a receiving terminal R which is connected to an appropriate signal processor supplying an output signal for further evaluation.

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Fiber Sensor

This article relates to an optical sensor with a glass fiber. As shown in the figure, a light pulse is transmitted from a light- emitting diode (LED) through the fiber to an appropriate modulator M which may take the form of movable mirror, an interferometer or a fluorescent material. Depending on the value to be measured, such as the position of a mechanical component, a certain amount of light is reflected to the modulator and transmitted back to the LED. Thus, the LED alternately acts as a transmitter for a light pulse and, after a certain transmission delay, as a receiver. Accordingly, the LED input terminal is periodically switched to a sending terminal S and a receiving terminal R which is connected to an appropriate signal processor supplying an output signal for further evaluation. The switch used for that purpose is actuated by an oscillator whose frequency must match the optical length of the fiber such that the clock cycle of the oscillator amounts to an even multiple of the total transmission time through the fiber. At an oscillator frequency of 5 megacycles, for example, a fiber length of 10 m should be used. In that way, only one element is used for sending and receiving, thus obviating the need for a special directional coupler in the fiber. The illustrated arrangement is simpler than known sensors and eliminates the attenuation attributable to the couplers previously required.

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