Long-Range Distributed Static Strain Sensing With <100 Nano-Strain Resolution Realized Using OFDR

Aiming at realizing a long-range and distributed static strain sensing system with nano-strain resolution realized using optical frequency domain reflectometry (OFDR), which is required for many practical applications, this paper provides a theoretical analysis for this system by using one-dimensional scattering model with backscattering process modelled by a set of discrete scatterers. Based on this model, the main noise sources of the sensing system are thoroughly analyzed, which mainly include the intensity noise, the random drift of the optical frequency, the phase noise of the optical source, and the phase noise caused by the frequency sweep nonlinearity. The theoretical prediction agrees well with the experimental results. In the experiments, by eliminating the main noise in the system, a distributed static strain sensing system is achieved over a 25-km-long fiber with a spatial resolution of 2.5 m and a strain resolution of <100 nano strain. This paper provides a reference for how to optimize OFDR-based distributed static strain sensing system to obtain an ultra-high performance.