A Low-Cost Phase-OTDR System for Structural Health Monitoring: Design and Instrumentation

Abstract

The design, development, and testing of a low-cost phase optical time-domain reflectometry (Phase-OTDR) system, intended for use in structural health monitoring (SHM) applications, are presented. Phase-OTDR is a technology that is growing and evolving at an impressive rate. Systems based on this principle are becoming very sensitive and elaborate and can perform very accurate condition monitoring, but at the same time, they are critically alignment-dependent and prohibitively costly to be considered as viable options in real field applications. Certain Phase-OTDR systems have been applied in real field studies, but these examples are mostly a proof-of-concept. The system presented here is the result of a compromise between performance and cost, using commercial components, specifically combined and tuned for SHM applications. The design and implementation of all the electronic and optoelectronic steps are presented, and the operation of the system is demonstrated, achieving a spatial resolution of ~6 m over 5 km. This work provides useful engineering guidelines for the low-cost implementation of Phase-OTDR systems. It is anticipated that the affordable development of such interrogation systems will promote their use in a wide range of SHM applications with moderate monitoring requirements and will assist the penetration of Phase-OTDR technology in the industry.

Comparative Assessment and Experimental Validation of a Prototype Phase-Optical Time-Domain Reflectometer for Distributed Structural Health Monitoring

“…Given that the system does not have a fully linear response, we demonstrate its application in structural analysis through a frequency content study. A complete discussion on this Phase-OTDR system performance, tuning, cost analysis, and decisions made during its design has been presented in [34], along with several parameter estimations.…”

“…Figure 6 shows the Phase-OTDR interrogation system recently developed by our group [34]. In this system, the laser provides continuous-wave light (1550 nm wavelength) that is pulsed by a semiconductor optical amplifier (SOA), used as a shutter to stimulate the Spectral Hole Burning (SHB) phenomenon.…”

“…The specific nonlinear Phase-OTDR system presented here is the result of a compromise between performance and cost, using commercial components, specifically combined and tuned for SHM applications, with a cost under 10 k€, which is substantially lower than the cost of typical commercial linear Phase-OTDR systems [34]. We present monitoring tests of the system on a scaled Bailey-type steel bridge model, which we also monitor with FBGs, GBRI, and Laser Tracking.…”

Optical Fiber Sensors for Ultrasonic Structural Health Monitoring: A Review

“…The repetition rate in turn determines the sampling rate of the system. Out of the three scattering principles, the Rayleigh scattering is the most commonly used because of the higher signal strength [22]. Although the distributed nature and the large range are both highly desirable, the sampling rate achieved by these sensors is very limited.…”

High SNR Φ-OTDR with Multi-Transverse Modes Heterodyne Matched-Filtering Technology

“…Phase-sensitive optical time domain reflectometer (Φ-OTDR) can detect and locate one or more vibration events occurring at any position along the optical fiber, and has a wide range of applications in boundary intrusion monitoring [1,2], oil and gas pipeline safety monitoring [3] and structural health monitoring [4,5]. The Φ-OTDR scheme was first proposed by H. F. Taylor et al to achieve intrusion detection in 1993 [6].…”