21 November 2007 Precise wavelength demodulator used for fiber sensitivity
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Proceedings Volume 6724, 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems; 67241L (2007) https://doi.org/10.1117/12.782901
Event: 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes, 2007, Chengdu, China
Abstract
Wavelength encoding sensors, such as fiber Bragg grating, have the advantage of strong antijamming ability. However, the wavelength encoding signal is usually converted to 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 wavelength encoding signal directly by means of counting using a Sagnac interferometer with birefringent fiber without 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 at the rising edge and falling edge of intensity appear, and then calculate the accurate change of wavelength signal. From experiment, we get 0.067 nm wavelength resolution by use of a Sagnac interferometer with 30 meter birefringent fiber. It is proved that the intensity frequency (the reciprocal of intensity period) changed with wavelength is proportional to the length of birefringent fiber. If the length is fixed, the frequency is determined. For farther increase of wavelength resolution, it is only necessary to increase the length of birefringent fiber. The wavelength demodulator is characteristic of high stability and high precision.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Shiya He, Tiecheng Guo, Shuyang Hu, Wei Liu, Kuanxin Yu, "Precise wavelength demodulator used for fiber sensitivity", Proc. SPIE 6724, 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems, 67241L (21 November 2007); doi: 10.1117/12.782901; https://doi.org/10.1117/12.782901
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