Abstract

Distributed optical fiber sensing (DOFS) technology has recently experienced an impressive growth in various fields including security, structural monitoring and seismology, among others. This expansion has been accompanied by a speedy development of the technology in the last couple of decades, reaching remarkable performance in terms of sensitivity, range, number of independent sensing points and affordable cost per monitored point as compared with competing technologies such as electrical or point optical sensors. Phase-sensitive Optical Time-Domain Reflectometry (φOTDR) is a particularly interesting DOFS technique, since it enables real-time monitoring of dynamic variations of physical parameters over a large number of sensing points. Compared to their frequency-domain counterparts (OFDR), φOTDR sensors typically provide higher dynamics and longer ranges but significantly worse spatial resolutions. Very recently, a novel φOTDR approach has been introduced, which covers an existing gap between the long range and fast response of φOTDR and the high spatial resolution of OFDR. This technique, termed time-expanded (TE) φOTDR, exploits an interferometric scheme that employs two mutually coherent optical frequency combs. In TE-φOTDR, a probe comb is launched into the fiber under test. The beating of the backscattered light and a suitable LO comb produces a multi-heterodyne detection process that compresses the spectrum of the probe comb, in turn expanding the detected optical traces in the time-domain. This approach has allowed sensing using φOTDR technology with very high resolution (in the cm scale), while requiring outstandingly low detection and acquisition bandwidths (sub-MHz). In this work, we review the fundamentals of TE-φOTDR technology and describe the recent developments, focusing on the attainable sensing performance, the existing trade-offs and open working lines of this novel sensing approach.

Time-expanded φOTDR using low-frequency electronics

Miguel Soriano-Amat, Hugo F. Martins, Sonia Martin-Lopez, Miguel Gonzalez-Herraez, María R. Fernández-Ruiz, and Vicente Durán
Opt. Express 31(2) 843- 852 (2023)

Distributed fiber-optic vibration sensing based on phase extraction from time-gated digital OFDR

Shuai Wang, Xinyu Fan, Qingwen Liu, and Zuyuan He
Opt. Express 23(26) 33301-33309 (2015)

Vectorial distributed acoustic sensing based on a multicore fiber and phase-sensitive optical time-domain reflectometry

Xunzhou Xiao, Jun He, Bin Du, Xizhen Xu, and Yiping Wang
Opt. Lett. 47(20) 5413-5416 (2022)

Distributed optical fiber sensing in coherent Φ-OTDR with a broadband chirped-pulse conversion algorithm

Kai Cao, Tuanwei Xu, Lilong Ma, Yinghao Jiang, Yaning Xie, Dimin Deng, and Fang Li
Opt. Express 31(4) 6649-6658 (2023)

Interferometric optical time-domain reflectometry for distributed optical-fiber sensing

Sergey V. Shatalin, Vladimir N. Treschikov, and Alan J. Rogers
Appl. Opt. 37(24) 5600-5604 (1998)