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Proceedings Paper

A highly precise fiber sensor by use of counting demodulation
Author(s): Shiya He; Haijun Li; Shuyang Hu; Wei Liu; Kuanxin Yu
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Paper Abstract

Wavelength encoding sensors, such as fiber Bragg grating, have the advantage of strong antijamming ability. However, the wavelength encoding signal is usually converted into electric intensity signal by demodulators in most measurements. The intensity signal is easy to be disturbed by environmental factors, so the advantage of wavelength encoding fails due to the instable intensity demodulation. In this paper, a novel wavelength demodulating method is presented. This method demodulates the wavelength encoding signal directly by means of counting using a Sagnac interferometer with birefringent fiber without the encoding conversion from wavelength to intensity. Through the interferometer, the changed wavelength signal from sensor becomes the kind of output light, the intensity of which is changed with wavelength periodically. The intensity can easy be disturbed, but its period is very stable. In other words, the change of wavelength in one intensity period is stable. With this character, we count the number when the rising edge and falling edge of intensity appear, and then calculate the accurate change of wavelength signal. In experiment, we get the 0.01 nm wavelength resolution by use of a Sagnac interferometer with 200 meter birefringent fiber. It can be proved that the intensity frequency (the reciprocal of intensity period) changed with wavelength is proportional to the length of birefringent fiber. The length is fixed, the frequency is determined. For farther increasing the wavelength resolution, it is only necessary to increase the length of birefringent fiber. The wavelength demodulator by counting method has high stability and high precision.

Paper Details

Date Published: 17 January 2008
PDF: 5 pages
Proc. SPIE 6830, Advanced Sensor Systems and Applications III, 68300Y (17 January 2008); doi: 10.1117/12.754514
Show Author Affiliations
Shiya He, Beijing Univ. of Technology (China)
Haijun Li, Beijing Univ. of Technology (China)
Shuyang Hu, Beijing Univ. of Technology (China)
Wei Liu, Beijing Univ. of Technology (China)
Kuanxin Yu, Beijing Univ. of Technology (China)


Published in SPIE Proceedings Vol. 6830:
Advanced Sensor Systems and Applications III
Yun-Jiang Rao; Yanbiao Liao; Gang-Ding Peng, Editor(s)

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