Abstract

We report here the experimental demonstration of measurement of both twist and transverse stress using polarization modulation in a single all-fiber circuit consisting of a single-mode fiber (SMF)/dual-mode fiber (DMF) in a Sagnac interferometer (SI) loop. The SMF-SI prototype setup is seen to be suitable for precise measurement of twist over a broad range of $\pm 50°$ and transverse stress up to 5 N with a sensitivity as high as $2.85\times {10}^6\mathrm{pW}/°$ and $2.08\times {10}^7\mathrm{pW}/\mathrm{N}$, respectively. It is envisaged that nearly ideal operation for twist measurement can be achieved by appropriately selecting the operating domain (pretwisted Sagnac loop for practical realization of the device) and required magnitude of applied transverse stress (weight yielding maximum sensitivity). Unlike SMF-SI, a DMF assisted SI exhibits asymmetric transmittance yielding a peak shift ($\sim 45°$) in addition to falling/rising peak amplitude of effective power($\sim 20\mathrm{\mu W}$). This key characteristic is further utilized for tunable measurement of torsion (unidirectional from $-70°$ to 40°) while keeping the sensitivity fixed. This research problem is then analyzed on the avenue of theoretical consideration and using classical polarization optics; we have derived the Jones birefringence matrix that accurately describes the transmission behavior of the configured fiber circuit (SMF-SI and DMF-SI) for each of the three cases, namely, transverse stress, twist, and both twist and transverse stress. Series of experimental measurements for various conditions of induced birefringence (linear/circular) were performed at length, and the results were compared with those determined theoretically towards configuring a twist and stress measuring device. The study provides an understanding of the underlying physics of dual-mode interference in a Sagnac configuration experiencing linear and circular birefringence.

© 2015 Optical Society of America

Characteristics of transverse-stress-induced phase change through a distinct dual-mode fiber in a Sagnac loop

Saba N. Khan, Sudip Kr. Chatterjee, Kajal Mondal, and Partha Roy Chaudhuri
J. Opt. Soc. Am. A 30(5) 1013-1020 (2013)

Highly sensitive twist sensor employing Sagnac interferometer based on PM-elliptical core fibers

Binbin Song, Hao Zhang, Yinping Miao, Wei Lin, Jixuan Wu, Haifeng Liu, Donglin Yan, and Bo Liu
Opt. Express 23(12) 15372-15379 (2015)

Highly sensitive torsion sensor with femtosecond laser-induced low birefringence single-mode fiber based Sagnac interferometer

Bo Huang and Xuewen Shu
Opt. Express 26(4) 4563-4571 (2018)

Simultaneous multi-parameter measurement using Sagnac loop hybrid interferometer based on a highly birefringent photonic crystal fiber with two asymmetric cores

Khurram Naeem, Bok Hyeon Kim, Bongkyun Kim, and Youngjoo Chung
Opt. Express 23(3) 3589-3601 (2015)

Orientation-free pressure sensor based on π-shifted single-mode-fiber Sagnac interferometer

Jiulin Gan, Li Shen, Qing Ye, Zhengqing Pan, Haiwen Cai, and Ronghui Qu
Appl. Opt. 49(27) 5043-5048 (2010)