Bent long-period fiber gratings for sensor applications

Zhihao Chen; Kin Seng Chiang; Mei Nar Ng; Yuen Ming Chan; Hong Ke

doi:10.1117/12.369362

11 November 1999 Bent long-period fiber gratings for sensor applications

Zhihao Chen, Kin Seng Chiang, Mei Nar Ng, Yuen Ming Chan, Hong Ke

Proceedings Volume 3897, Advanced Photonic Sensors and Applications; (1999) https://doi.org/10.1117/12.369362
Event: International Symposium on Photonics and Applications, 1999, Singapore, Singapore

Abstract

The transmission characteristics of bent long-period fiber gratings (LPFGs) and their applications as sensors are studied experimentally. We demonstrate that, by bending a LPFG, two major rejection bands in the wavelength region of interest can be produced, whose relative strength can be controlled by the amount of bending. The wavelength separation between the two bands increases linearly with the lateral displacement of the bent LPFG and a linear tuning range over 40 nm is demonstrated. All these characteristics show no significant polarization dependence. We also find that, by mounting a bent LPFG on a proper material, the thermally induced bending effect can enhance or cancel the direct thermal effect. With this technique, we obtain temperature sensitivities of 0.01 nm/degrees C and -0.35 nm/degrees C, which are, respectively, about 1/5 and 7 times of that of a straight bare LPFG. A temperature-insensitive LPFG-based sensor for the measurement of the concentration of NaCl in water is demonstrated with a sensitivity of -0.35nm/molarity by keeping the temperature sensitivity at 0.01 nm/degrees C from 15 to 70 degrees C. By using the same technique, a strain sensitivity of -49nm/percent (epsilon) is obtained, which is about 15 times of that of a straight bare LPFG.

Citation Download Citation

Zhihao Chen, Kin Seng Chiang, Mei Nar Ng, Yuen Ming Chan, and Hong Ke "Bent long-period fiber gratings for sensor applications", Proc. SPIE 3897, Advanced Photonic Sensors and Applications, (11 November 1999); https://doi.org/10.1117/12.369362

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