A distributed fiber sensor based on Rayleigh scattering is described which converts vibration-induced optical phase changes into optical intensity variations by using modulated dual-pulses injected into sensing fiber. Phase generated carrier algorithm is used to permit arctangent operation to demodulate the phase information along the sensing fiber. The demonstrated sensor is capable of probing dynamic acoustic or vibration disturbances over 10km of sensing length with spatial resolution of 6m and large signal to noise ratio. The background noise of our system is estimated about 1×10-3 rad/√Hz.
Rayleigh backscattering induces mode hopping of DFB fiber lasers in the sensor array, and the critical length related to
Rayleigh backscattering limits the size of DFB fiber laser sensor networking. Based on three-mirror cavity model, the
critical length for DFB fiber lasers are derived. It increases nearly exponentially with the coupling coefficient for the
ideal π-shifted DFB fiber lasers. While the reflectivity of the sub-FBG at lasing wavelength is the main factor to resist
Rayleigh backscattering for a non-ideal DFB fiber laser. The corresponding experiments have been carried out, and the
results agree with the predictions.
Rayleigh backscattering induces mode hopping of distributed feedback (DFB) fiber lasers in the sensor array, and the critical length related to Rayleigh backscattering limits the size of DFB fiber laser sensor networking. Based on a three-mirror cavity model, the critical length for a DFB fiber laser is derived. It increases nearly exponentially with the coupling coefficient for the ideal π-shifted DFB fiber lasers. The reflectivity of the sub-fiber Bragg grating at the lasing wavelength is the main factor to resist Rayleigh backscattering for a nonideal DFB fiber laser. The corresponding experiments have been carried out, and the critical length of larger than 150 m was achieved for 42-mm-long DFB fiber lasers.
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