Fiber Bragg gratings (FBGs) have been attractive in fiber-optic sensors because of their many advantages, such as wavelength-selective nature, easy installation and adaptability, and low insertion loss. External perturbations like temperature, strain, and bending basically make the center wavelength of FBGs shifted. It is necessary to improve the sensitivity of the FBG sensing probe to external perturbation change to realize high quality of fiber-optic sensors. Recently, the weak value amplification (WVA) technique based on a quantum effect or interference has been proposed to enhance a degree of sensitivity in the process of measurement. The polarization-dependent WVA was experimentally suggested to realize the increment in a degree of sensitivity of the FBG strain and temperature sensors. The previous method, however, has many drawbacks, such as sophisticated structure, instability and difficulty in polarization adjustment, and experimental inconvenience due to polarization. In this paper, we propose a new method of the WVA based on the optical attenuation to improve the performance of the FBG sensor, which has a simple structure compared to the polarization-based WVA. The proposed WVA based on optical attenuation is configured by a broadband light source, two 3-dB optical couplers, two optical circulators, two FBGs with the same center wavelengths, and an optical attenuator. In the proposed WVA, the sensitivity of the sensing FBG to external perturbation can be enhanced by increasing the amplification factor depending on the optical attenuation. The strain sensitivity of the FBG sensor using the proposed attenuation-based WVA was successfully enhanced by a factor of 2.73 compared with that without the WVA.
Kwang-Wook Yoo, Duy Duong Anh Le, Seung Min Lee, Ju Il Hwang, Hoeil Chung, Kyung Joon Cha, and Young-Geun Han, "Weak value amplification based on optical attenuation for sensitivity improvement of fiber Bragg grating sensor (Conference Presentation)," Proc. SPIE 10528, Optical Components and Materials XV, 105280J (Presented at SPIE OPTO: January 30, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2289242.5751438510001.
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