Distributed Vibration Sensor Based on Coherent Detection of Phase-OTDR

TLDR

Pencil break measurement emulates acoustic emission from cracks in concrete or steel bridges to enable early crack identification. The system aims to provide vibration detection for health monitoring of civil structures and other dynamic monitoring needs. A distributed vibration sensor was built using heterodyne detection and moving‑average/differential signal processing on a phase‑OTDR system. The sensor first measured and located broadband acoustic components from pencil‑break vibration, achieving 5 m spatial resolution and a 1 kHz maximum frequency response limited by the data‑acquisition trigger.

Abstract

We developed a distributed vibration sensor by using heterodyne detection and signal processing of moving averaging and moving differential for the phase optical time domain reflectometry system. The broadband acoustic frequency components generated by pencil-break vibration have been measured and identified in location by our distributed vibration sensor for the first time. Pencil break measurement is a standard technique to emulate the acoustic emission of cracks in concrete or steel bridges for early crack identification. The spatial resolution is 5m and the highest frequency response is 1 kHz, which is limited by the trigger frequency of data acquisition card. This new sensing system can be used for vibration detection of health monitoring of various civil structures as well as any dynamic monitoring requirement.