120 km single-photon Brillouin optical time domain reflectometry

TL;DR

This paper introduces a 120 km range single-photon BOTDR system using standard fibers and SPADs, enabling distributed temperature and strain measurements with high resolution and reliability.

Contribution

It presents a novel hd-BOTDR method that employs a fiber Bragg grating-based frequency discriminator, eliminating the need for frequency scanning.

Findings

Achieved 120 km range with 10 m resolution

Successfully detected a hot spot at 100 km

Demonstrated strain and temperature differentiation

Abstract

We present a novel distributed Brillouin optical time domain reflectometer (BOTDR) using standard telecommunication fibers based on single-photon avalanche diodes (SPADs) in gated mode, hd-BOTDR, with a range of 120 km and 10 m spatial resolution. We experimentally demonstrate the ability to perform a distributed temperature measurement, by detecting a hot spot at 100 km. Instead of using a frequency scan like conventional BOTDR, we use a frequency discriminator based on the slope of a fiber Bragg grating (FBG) to convert the count rate of the SPAD into a frequency shift. A procedure to take into account the FBG drift during the acquisition and perform sensitive and reliable distributed measurements is described. We also present the possibility to differentiate strain and temperature.