Multiplexing System For Frequency Modulated Fibre Optic Sensors Using Pseudo-Random Sequences

J. J. Mlodzianowski; D. Uttamchandani; B. Culshaw

doi:10.1117/12.949289

23 February 1989 Multiplexing System For Frequency Modulated Fibre Optic Sensors Using Pseudo-Random Sequences

J. J. Mlodzianowski, D. Uttamchandani, B. Culshaw

Proceedings Volume 1011, Fiber Optic Sensors III; (1989) https://doi.org/10.1117/12.949289
Event: 1988 International Congress on Optical Science and Engineering, 1988, Hamburg, Germany

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.

Citation Download Citation

J. J. Mlodzianowski, D. Uttamchandani, and B. Culshaw "Multiplexing System For Frequency Modulated Fibre Optic Sensors Using Pseudo-Random Sequences", Proc. SPIE 1011, Fiber Optic Sensors III, (23 February 1989); https://doi.org/10.1117/12.949289

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