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Applied Optics

Applied Optics


  • Vol. 35, Iss. 22 — Aug. 1, 1996
  • pp: 4522–4525

Interferometric distributed optical-fiber sensor

Stephanus J. Spammer, Pieter L. Swart, and André Booysen  »View Author Affiliations

Applied Optics, Vol. 35, Issue 22, pp. 4522-4525 (1996)

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An interferometric technique is described for detecting and locating perturbations along an optical fiber. This distributed sensor, based on a modified fiber-ring interferometer, has a position-dependent response to time-varying disturbances such as strain or temperature. These disturbances cause a phase shift that is detected and converted to spatial information. The sensor consists of two parts, namely, a reflecting-fiber-ring interferometer and a differentiating-ring interferometer. The reflecting ring consists of a fiber ring with one port of the coupler connected to a reflector. Consequently the output port of the reflecting-ring interferometer is the same as the input port. Because it is an inherent zero-path-imbalanced system, a short-coherence-length source such as a light-emitting diode can be used. Any time-varying perturbation on the fiber in the ring results in a detector signal proportional to the product of the rate-of-phase change caused by the perturbation and the distance of the perturbation relative to the center of the fiber ring. The second part of the system, a differentiating-ring interferometer, consists of the same fiber-ring interferometer modified only slightly. The output of this part of the sensor is proportional only to the rate of phase change as a result of the unknown perturbation and contains no distance information. By dividing the output of the reflecting-ring interferometer by the output of the differentiating-ring interferometer, we determine disturbance location. Results obtained with a 155-m distributed fiber sensor are discussed.

© 1996 Optical Society of America

Original Manuscript: September 1, 1995
Revised Manuscript: January 16, 1996
Published: August 1, 1996

Stephanus J. Spammer, Pieter L. Swart, and André Booysen, "Interferometric distributed optical-fiber sensor," Appl. Opt. 35, 4522-4525 (1996)

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  1. J. P. Dakin, D. A. J. Pearce, A. P. Strong, C. A. Wade, “A novel distributed optical fiber sensing system enabling location of disturbances in a Sagnac loop interferometer,” Fiber Optic and Laser Sensors V, R. P. DePaula, E. Udd, eds., Proc. SPIE838, 325–328 (1987).
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