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Proceedings Paper

Multiplexing System For Frequency Modulated Fibre Optic Sensors Using Pseudo-Random Sequences
Author(s): J. J. Mlodzianowski; D. Uttamchandani; B. Culshaw
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Paper Abstract

A simple system for multiplexing frequency modulated sensors has been demonstrated and its performance evaluated. The multiplexing scheme is based on spread spectrum modulation of the optical source exciting the sensor network. A pseudo-random binary sequence generated from a digital shift register, is used to modulate the source. This sequence has the feature that its normalized autocorrelation has a value of 1 at zero delay and a constant value of -1/N (where N is the code length) at other delays. A demonstration system consisting of a single mode fibre network of three sensors and the associated electronics has been built. The network is illuminated by a laser diode intensity modulated by 255 bit PN sequence. An analog correlator is used to correlate the signal received from the network with a reference sequence. By altering the delay of the reference sequence it is possible to tune to any specific sensor in the network, and suppress the signals from unwanted sensors. Experimental measurements have shown that the responses from the sensors can be suppressed by up to 30 dB.

Paper Details

Date Published: 23 February 1989
PDF: 4 pages
Proc. SPIE 1011, Fiber Optic Sensors III, (23 February 1989); doi: 10.1117/12.949289
Show Author Affiliations
J. J. Mlodzianowski, University of Strathclyde (Scotland)
D. Uttamchandani, University of Strathclyde (Scotland)
B. Culshaw, University of Strathclyde (Scotland)

Published in SPIE Proceedings Vol. 1011:
Fiber Optic Sensors III
Ralf Th. Kersten, Editor(s)

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