Abstract
Utilizing a single-photon detector, a novel direct-detection optical-fiber sensor for distributed measurement of temperature based on spontaneous Brillouin scattering is proposed and demonstrated experimentally. In our scheme, the ratio of the backscattered Rayleigh signal and the backscattered Brillouin anti-Stokes is adopted to retrieve the monitored temperature information along the optical fiber. Taking advantage of the high sensitivity of the single-photon detector, our proposed system achieves a dynamic range of 20 dB without any optical amplification. The obtainable dynamic range corresponds to a sensing distance of 120 km with a measured temperature error of 0.96°C. Furthermore, the proof-of-concept experiment demonstrates 1.2 m spatial resolution over 4.2 km sensing link with 1.24°C temperature error. Considering the performance we achieved now, and the increasing improvement of the fabrication technology of sing-photon detector, the photon-counting distributed Brillouin sensor is opening a door in the field of optical-fiber sensors.
Highlights
As one of the strongest nonlinear optical phenomena, Brillouin scattering has been discovered and widely studied for several decades
When performing the so-called strong backscattered Rayleigh scattering (RS) component measurement, an amplified spontaneous emission (ASE) light source with the maximum output power of 16.9 dB m is used instead of the distributed feedback (DFB) laser source to suppress the fluctuation of captured backscattered RS caused by coherent fading noise. e received wideband backscattered RS is coupled into the variable optical attenuator (VOA) via the second channel of the OS2 in order to avoid saturating the singlephoton detectors (SPD)
By using the ASE light source and an optical spectrum analyzer (OSA: YOKOGAWA, AQ6370D), the corresponding experimental results are successfully obtained, which are separately plotted in Figures 3 and 4
Summary
As one of the strongest nonlinear optical phenomena, Brillouin scattering has been discovered and widely studied for several decades. The first type (BOTDR) is considered as one of the most promising techniques that can retrieve distributed ambient temperature information by single-ended fiber under test (FUT) architecture, large dynamic range, and random accessibility. It typically adopts a modulated probe pulse to interrogate the FUT and demodulate position information from the time-of-flight of the backscattered Brillouin photons from the sensing fiber. The change in temperature conditions of the sensing optical fiber induces variations in the acoustic
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