An optical displacement transducer for aerospace applications

Abstract

A passive optical linear displacement transducer for aerospace applications has been developed. The principle of operation is the wavelength encoding of the position of a reflective Gray code. The design allows the sensor to be passively interrogated using only two optical fibres. The example described here has a 38 mm stroke with a 38 μm resolution. The same principle can be applied to longer stroke linear sensors and rotary displacement sensors.

The optical design is based on the wavelength division of a broad-band source into 11 spectral bands, which are directed onto a reflective Gray code. The reflected light is decoded by a second wavelength division multi-plexer in the electronics housing and the position of the Gray code is determined by the respective on/off states of the channels. The transducer has been designed to operate in the harsh aerospace environment. The housing is of rugged construction to withstand the standard range of temperature, vibration, pressure and contamination conditions.