A cost-effective method for estimating the Brillouin frequency shift (BFS) of the whole sensing fiber without using an electrical spectrum analyzer is developed. The Brillouin gain spectrum is down-converted and low-pass-filtered, and its total transmitted power is used to estimate the BFS. The strain dynamic range of this method is experimentally shown to be double the value of a conventional slope-assisted method.

Fibre-optic distributed Brillouin sensing that utilises correlationdomain techniques often requires an optical delay fibre in the reference path to control the correlation peak order in the sensing fibre. Nonetheless, a suboptimal delay fibre length can result in decreased performance. In this work, as a first step towards clarifying the optimal delay fibre length for Brillouin correlation-domain sensing, the authors evaluate the effect of changing the delay fibre length on the Brillouin gain spectra in a full-length measurement scenario.