Quasi-Distributed Strain Sensing System Based on Optical Spectrum-Limited Chaos and CFBG Intensity Demodulation

We propose a quasi-distributed sensing system using optical spectrum-limited chaos for strain measurement with a high spatial resolution of locating. An optical bandpass filter is programmed in accordance with each sensor to implement the intensity demodulation of multiple chirped fiber Bragg gratings (FBGs). A cross-correlation algorithm is adopted in this sensing scheme. Consequently, strain sensing and locating can be simultaneously demodulated by the relative amplitude change (RAC) and time delay of a certain cross-correlation peak. Meanwhile, fiber fault monitoring can also be implemented by the cross-correlation algorithm, and an additional optical passband is reserved for sufficient breakpoint testing optical power. The proof-of-concept experiment demonstrates that the strain sensitivity reaches 0.12% RAC/
$\mu\varepsilon$
, and the spatial resolution is up to 3.3 cm. Finally, the performance of fiber fault monitoring is also demonstrated.