Fast coarse-fine locating method for φ-OTDR

Abstract

We proposed and demonstrated a coarse-fine method to achieve fast locating of external vibration for the phase-sensitive optical time-domain reflectometer (φ-OTDR) sensing system. Firstly, the acquired backscattered traces from heterodyne coherent φ-OTDR systems are spatially divided into a few segments along a sensing fiber for coarse locating, and most of the acquired data can be excluded by comparing the phase difference between the endpoints in adjacent segments. Secondly, the amplitude-based locating is implemented within the target segments for fine locating. By using the proposed coarse-fine locating method, we have numerically and experimentally investigated a distributed vibration sensor based on the heterodyne coherent φ-OTDR system with a 50-km-long sensing fiber. We find that the computation cost of signal processing for locating is significantly reduced in the long-haul sensing fiber, showing a potential application in real-time locating of external vibration.

Application of sensors for civil aircraft inerting system performance flight test

“…This system employs a patented technology based on diode laser absorption spectroscopy, enabling non-contact and real-time measurement of low-temperature gas [8] . It proves to be a valuable tool for analyzing the oxygen concentration in Jet-A aviation fuel and air mixtures [9][10] . The laser diode emits visible light with a wavelength of 760 nanometers, which is absorbed by oxygen molecules.…”

Enhanced fault characterization by using a conventional OTDR and DSP techniques

“…the Poisson noise in photon-counting OTDR and the coherent Rayleigh noise in Coherent-OTDR [20]). In addition, this presented detection approach can be extended to other configuration such as ϕ -OTDR for sensing applications [22].…”

Long range fading free phase-sensitive reflectometry based on multi-tone NLFM pulse

“…Though distributed amplifications, including Raman amplification [11], Brillouin amplification [12], and their combination [13], have been validated to compensate the fiber loss and thus extend the sensing distance to over 100 km, these configurations require the pump light be injected into the both ends of sensing fiber, which reduces the degree of freedom in embedding the fiber into structures. The un-pumped schemes are characterized by single ended injection, but their sensing distances are limited to within 50 km [14,15]. However, frequency modulation technique is promising for sensing range improvement, because it increases the pulse length without deteriorating the spatial resolution [16].…”