Fig. 1. Schematic diagram of the proposed high-resolution strain sensor network.

Fig. 2. (a) Phase change induced by laser frequency shift. (b) Relationship between the reference channel and sensing channel for laser frequency shift.

Fig. 3. (a) Phase change induced by temperature fluctuation. (b, c) Enlarged images for phase change. (d) Relationship between the reference channel and sensing channel for temperature fluctuation.

Fig. 4. Hysteresis operator. (a) Relay operator. (b) Play operator.

Fig. 5. Block diagram of the LS-SVM based hysteresis model.

Fig. 6. (a) Received beat frequency signal. (b) Beat frequency signal of sensor element 55 and 54.

Fig. 7. The relationship between phase change and strain.

Fig. 8. (a) Temperature change waveform and corresponding phase change for model train. (b) Hysteresis loops for temperature change and the regression result. (c) Compensation error.

Fig. 9. (a) Original phase signal for temperature change and strain signal. (b) Compensation results for two methods. (c) PSD of the original result and compensation results.

Fig. 10. (a) Original phase signal in a quiet environment. (b) Compensation results for two methods. (c) Noise floor PSD of the original result and compensation results.