Characterization and application of fiber laser with faraday rotating mirror = 패러데이 회전거울을 사용하는 광섬유 레이저의 특성 및 그 응용에 관한 연구

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This dissertation describes an erbium-doped fiber laser operating in orthogonally polarized dual-frequency modes and its application to electric current sensing with frequency read-out. A Faraday rotating mirror and spatial hole burning effects in a gain medium and in a saturable absorber are utilized to control the lasing mode and polarization. The polarization mode beat (PMB) frequency changes linearly in response to an external magnetic field induced by an electric current. When the laser was applied to sensing an alternating current (AC) of a solenoid (1528 turns, 42 cm long), the PMB frequency was modulated in proportional to the applied current with the slope coefficient of 8.3 kHz/A. A simple frequency demodulation technique based on a phase-locked loop (PLL) circuit is used for signal processing. The scale factor of 3.5 μV/(Aㆍturn) and the noise-equivalent current of $2.0 A_{rms}\cdot turn/Hz^{1/2}$ were obtained. The fiber laser sensor in the present set-up would not be suitable for a direct current (DC) measurement because of the drift and hopping of the PMB frequency. However, this problem can be largely tolerated in the case of an AC measurement. The polarimetric fiber laser current sensor has the potential advantages of frequency encoding, immunity to intensity fluctuations, and freedom from lead-fiber sensitivity, which are difficult to achieve with previous passive polarimetric current sensors. Resulting from these advantages, the laser sensor can be easily extended to an array structure by use of frequency division multiplexing (FDM) and/or wavelength division multiplexing (WDM) technique. We propose and demonstrate a novel frequency domain multiplexing technique of polarimetric fiber laser current sensors. Each sensor operates at a different PMB frequency that is determined by the cavity length of individual laser. A bank of electrical bandpass filters can be used to separate signals from different sensors. Furthermore, a wavelength divis...
Kim, Byoung-Yoonresearcher김병윤researcher
한국과학기술원 : 물리학과,
Issue Date
169627/325007 / 000975221

학위논문(박사) - 한국과학기술원 : 물리학과, 2001.8, [ iv, 76 p. ]


frequency division multiplexing; current sensor array; current sensor; fiber laser; wavelength division multiplexing; 파장 분할 방식; 주파수 분할 방식; 전류 센서 어레이; 전류 센서; 광섬유 레이저

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