Differentiating interferometer for current measurements

Pieter L. Swart; Stephanus J. Spammer; David C. Theron

doi:10.1117/12.221704

25 September 1995 Differentiating interferometer for current measurements

Pieter L. Swart, Stephanus J. Spammer, David C. Theron

Proceedings Volume 2510, Fiber Optic and Laser Sensors XIII; (1995) https://doi.org/10.1117/12.221704
Event: European Symposium on Optics for Environmental and Public Safety, 1995, Munich, Germany

Abstract

A differentiating interferometer is proposed for measuring time varying signals. The system comprising a modified fiber ring resonator was implemented to measure electrical current. The modified ring resonator consists of a length of fiber between one of the input and output ports of a directional coupler. This length of fiber forms a delay line resulting in a constant delay time. The other coupler output port is connected to the sensing element and a reflector. By means of the delay time, the interferometer detects the derivative of the unknown perturbation signal at the common input/output port of the interferometer. Since the total path length imbalance is zero, a short coherence length source such as a light emitting diode can be used. The inherent properties of the interferometer also ensures insensitivity to slowly varying fluctuations such as temperature drift. With the introduction of frequency domain multiplexing, the sensor can easily be expanded into a multiplexed sensor system to measure multiple signals. Current measurement is achieved by means of a current transformer terminated with a resisitive load. The resulting potential difference across the load drives a piezoelectric ring which in turn phase modulates the optical signal. Results of a frequency multiplexed two element 50Hz current sonsor will be discussed.

Citation Download Citation

Pieter L. Swart, Stephanus J. Spammer, and David C. Theron "Differentiating interferometer for current measurements", Proc. SPIE 2510, Fiber Optic and Laser Sensors XIII, (25 September 1995); https://doi.org/10.1117/12.221704

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KEYWORDS

Interferometers

Sensors

Multiplexing

Signal detection

Phase shift keying

Modulation

Modulators

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