Study on fiber ring laser in sensing application with beat frequency demodulation

A simple fiber ring laser is used for sensing based on beat frequency demodulation. Because of the absence of a mode selecting device, the mode spacings between multi-longitudinal modes in the laser can be large. Therefore, the beat frequency signals with high frequency are generated, and the high sensitivities will be achieved. In the experiment, six different beat frequency signals are studied and compared in strain sensing. Their sensitivities are in good agreement with theoretical predictions. The signal-to-noise ratios, 3-dB bandwidths, maximum measureable strains, stabilities, and their measurement accuracies are also measured and discussed. The fiber ring laser sensor system proposed is robust and cost-effective.

► A simple fiber ring laser for sensing applications with beat frequency demodulation is proposed.
► The absence of mode selecting device induces higher beat frequency signals.
► Six different beat frequency signals are studied and compared in strain sensing in detail.
► The usage of high-frequency signal for sensing improves the measurement sensitivity and accuracy.
► The fiber ring laser sensor system presented is robust and cost-effective.