The Application Of Broadband Optical Chaos In Fiber Sensing

Optic fiber sensing networks often need to work in harsh environments,thus fiber fault and damage can happen occasionally.Because of the wide range and complex structure of the fiber sensing networks,it often requires a lot of time and manpower to locate the fiber fault position.Therefore,fiber fault monitoring and locating in fiber sensing networks is of great significance for the improvement of survivability.Broadband optical chaos based on partial feedback semiconductor optical amplifier(SOA)ring structure possesses a good correlation characteristic.Combined with the cross correlation algorithm,monitoring and precise locating of fiber fault can be achieved.Furthermore,by monitoring the peak fluctuation in the cross correlation curve,sensing parameters can be demodulated simultaneously.Thus the broadband optical chaos and correlation algorithm can be applied in fiber sensing.The main studies of this thesis include:(1)The output properties of the broadband optical chaos based on partial feedback SOA ring structure and the principle of fault monitoring and locating with optical chaos and correlation are studied.The spatial resolution of 3.6 cm is achieved in a fault locating experiment,and the spatial resolution is unaffected by the sensing range.(2)Broadband optical chaos and correlation are applied to the field of vibration sensing,and division correlation demodulation method is proposed for the demodulation of dynamic vibration signal.The relationship between the frequency sensing range,sensing distance and sampling rate is analyzed,and through a vibration sensing experiment,a maximum frequency of 8kHz is measured under the sensing distance of 6km,while 24kHz is measured under 80m.Also,the precise locating of the sensing points is achieved.(3)Broadband optical chaos and correlation are applied to the field of liquid level sensing,and based on the correlation algorithm,differential correlation demodulation method is proposed to improve the ability of resisting light source power variation.The dynamic range of 5.4cm with the accuracy of 0.18cm and the linearity R~2 of 0.99686 in liquid level sensing is achieved through experiment,and the ability of resisting light source power variation and fault monitoring and locating is verified.