A fibre optic based ranging sensor

Huang, Wen Xin (1993) A fibre optic based ranging sensor. Research Master thesis, Victoria University of Technology.


The remote determination of distance is an important requirement in a wide variety of technical and industrial applications. Ranging techniques have evolved from geometrical to bulk optical or radar methods. There is however a demand for low-cost short to medium range sensors, for operation in potentially hazardous environments, which may be satisfied by optical fibre based sensors. In this thesis the development of an optical ranging sensor, based on fibre optic technology, is described for range measurements over a few metres. Its operation requires an intensity modulated frequency-swept signal which is split and transmitted along two unequal paths before being recombined to form a beat signal. The frequency of this beat signal varies proportionally with the path difference. Incoherent light, from a 780 nm modulated laser diode, was launched into a fibre optic Michelson interferometer which was realised using a 3 dB coupler, with the ranging performed in a free-air path which, formed part of one arm. A variety of optical launching schemes were investigated, and processing electronics were developed progressively to improve the determination of the beat frequency. The sensor was calibrated over a free air path of several metres, and a conservative resolution of 1% was achieved.

Additional Information

Master of Science

Item type Thesis (Research Master thesis)
URI https://vuir.vu.edu.au/id/eprint/18178
Subjects Historical > FOR Classification > 0205 Optical Physics
Historical > FOR Classification > 0915 Interdisciplinary Engineering
Historical > Faculty/School/Research Centre/Department > School of Engineering and Science
Keywords fibre optic sensing systems, distance measurements, equipment, theoretical analysis, experimental details
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