Study Of Brillouin Scattering In Optical Fiber And Its Application

Brillouin scattered light originates from light interaction with acoustic phonons whenlightwave transmits in optical fiber and the Brillouin scattering light has a certain frequencyshift relative to the incident light. The Brillouin frequency shift is subject to the properties ofoptical transmission medium and changes linearly with the temperature and strain of themedium. Brillouin scattering effect in optical fiber can be used in distributed fiber-opticsensing, Brillouin fiber laser, multi-wavelength Brillouin fiber laser, broadband microwavesignal generator and so on. This dissertation focuses on the Brillouin fiber laser and itsapplication in distributed fiber-optic sensing and the main contents are as follows.The Brillouin fiber laser and its frequency shift effect has been studied. Ultra-shortcavity Brillouin fiber ring laser with the length of5m has been realized through usinghome-made Er3+/Yb3+codoped phosphate glass fiber with a net gain up to5.2dB/cm. Inaddition, multi-wavelength Brillouin fiber laser with27order stokes light anddouble-Brillouin frequency shift multi-wavelength Brillouin fiber laser with9order stokeslight have been realized through optimizing the laser cavity. To overcome the broadbandsignal coherent demodulation problem in distributed fiber temperature sensing system, anactive Brillouin fiber ring laser has been constructed to serve as optical frequency shifter andthus we have successfully downconverted the demodulation signal from11GHz to100MHz inin distributed fiber temperature sensing system.The temperature sensing system based on dual-frequency Brillouin fiber laser microwavegenerator has been constructed, microwave signal originates from a beat frequency producedby the dual-frequency Brillouin fiber laser. The frequency of the microwave signal can betuned by changing the temperature of optical fiber within the ring cavity. Based ondual-frequency Brillouin fiber laser, a temperature sensing system has been constructed andthe sensitivity is tested to be better than±1℃. All-light controlled trigging laser has beenrealized in the experiment. Based on the properties of cross gain saturation and saturableabsorption in gain medium, all-fiber optical controlled trigging laser、hybrid optical controlledtrigging laser and SOA optical controlled trigging laser have been realized. In addition, theoperation state of the optical controlled trigging laser can be triggered to be on or off by singletrigging pulse. The response time of the optical controlled trigging laser is subject to thecarrier recovery time of the gain medium. The shorter carrier recovery time is, the fasterresponse rate of the optical controlled trigging laser will be. The response time of the all-fiberoptical controlled trigging laser and hybrid optical controlled trigging laser is within several milliseconds, whereas the response time of the SOA optical controlled trigging laser is lessthan one microseconds. And the trigging pulsewidth for the on and off state in the SOAoptical controlled trigging laser has been tested to reach75ns and40ns respectively in theexperiment.