Dual-laser time-domain Vernier sensor for high-resolution strain measurement

We demonstrate a fiber-optic strain sensor based on a dual-laser time-domain Vernier effect. Two narrow-linewidth lasers and a common-arm interferometer with a variable optical delay line enable optical path scanning. Signals from three photodetectors are converted to the spatial domain and superimposed to create a Vernier envelope. A strain sensitivity of 397.09 μm μ ε −1 and a short-term repeatability of 0.128 n ε (standard deviation over 18 s) are achieved. Sensitivity is tunable via laser wavelength without hardware changes. This scheme offers a cost-effective solution for high-resolution static strain sensing.