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.
Highlights
Condition monitoring [1] is an emerging engineering area which is developing rapidly with the help of available sensing technologies, providing the means for efficient asset management and predictive maintenance in industry and infrastructures [2]
Typical laboratory setups use kHz-linewidth lasers, GHz-modulators, several optical amplifiers, highly sensitive photo-detectors, high bandwidth amplifiers and high-sample-rate/high-bandwidth digitizers. This set of components, together with assembling costs and tuning difficulties, make Phase-OTDR a niche technology that struggles to spread in applied research and real-life applications, such as structural health monitoring (SHM), even though its cost is small when considered per length of sensing
We present the design and implementation of a simple, low-cost, alignment-free, and sensitive non-linear Phase-OTDR system, designed to be portable and harsh-environment tolerant
Summary
Condition monitoring [1] is an emerging engineering area which is developing rapidly with the help of available sensing technologies, providing the means for efficient asset management and predictive maintenance in industry and infrastructures [2]. Such an uncontrolled signal change increases the difficulty in setting event alarm trigger thresholds when the signals are noisy Even with these limitations, non-linear Phase-OTDRs are useful instruments for SHM, where an extended sensing fiber length becomes essential for frequency analysis, aging detection or damage prevention on any large civil structure [13]. Typical laboratory setups use kHz-linewidth lasers, GHz-modulators, several optical amplifiers, highly sensitive photo-detectors, high bandwidth amplifiers and high-sample-rate/high-bandwidth digitizers This set of components, together with assembling costs and tuning difficulties, make Phase-OTDR a niche technology that struggles to spread in applied research and real-life applications, such as SHM, even though its cost is small when considered per length of sensing.
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