Basic study on novel fiber-optic distributed strain sensor with very high resolution using Rayleigh backscattering

我们以前提出了一种新的技术来测量分布应变和温度的光纤具有非常高的测量分辨率。该技术利用单模光纤瑞利背散射轨迹的锯齿状外观，通过使用具有精确频率控制光源的相干OTDR进行测量。为了明确这种传感技术的潜力，我们进行了数值模拟和实验。实验结果证实了瑞利后向散射轨迹的以下基本特征，这些特征对于我们的传感技术至关重要。(1)当传感光纤置于相同的条件下（应变和温度）时，OTDR走线始终呈现相同的波形。(2) OTDR轨迹的波形随应变或温度的变化而变化，但可以通过调节激光频率来重现初始波形。我们的数值模拟表明，对于40/8 km长的光纤，测量应变分布的分辨率为0.1/1 με，空间分辨率为1/0.1 m是可能的。

We have proposed previously a novel technique for measuring distributed strain and temperature in a fiber with a very high measured resolution. This technique makes use of the jagged appearance of Rayleigh backscatter traces from a single-mode fiber measured by using a coherent OTDR with a precisely frequency-controlled light source. In order to make clear the potential of this sensing technique, we have conducted numerical simulations and experiments. The experimental results confirmed the following basic characteristics of the Rayleigh backscatter traces that are essential as regards our sensing technique.(1) The OTDR trace always exhibits an identical waveform when the sensing fiber is placed under the same conditions (strain and temperature).(2) The waveform of the OTDR trace varies as the strain or the temperature changes, but the initial waveform can be reproduced by adjusting the laser frequency.Our numerical simulations indicated the possibility of measuring strain distribution with a resolution of 0.1/1 με and a spatial resolution of 1/0.1 m for a 40/8 km long fiber.