The Research Of Linewidth Narrowing Technique Of Linear Cavity Fiber Laser

Linear resonant cavity optical fiber laser has been widely used in the field of fiber optical fiber communication and optical fiber sensor as for its small volume bulk,stable longtitude mode and suitable to multiplexed systems.However,the laser linewidth is typically a few kilo hertz that will introduce huge phase noise in the unbalance interference system.In this paper,the compression of the laser's line width and phase noise are studied.The relationship of laser's linewidth and the cavity structure parameters are analyzed in theory including grating cavity photons life,cavity loss,and other factors.Apodized fiber grating used in linear cavity laser,virtual folded cavity and self-feedback injection is studied from theory and experiment.Paper main research results are as follows:i.Apodized fiber grating which is more suitable for using in linear cavity fiber laser has carried on the theoretical and experimental research.As a result of setting the sinc type mark apodized fiber grating production system,we succeeded in fabricating apodized fiber grating,the experimental 50 db high reflectivity of the grating are obtained.ii.We solve the problem of fabricating of appointed center wavelength fiber grating according to the requirement of fiber laser.Now,the precise of the central wavelength is 0.05 nm which ensure the making of special structure linear cavity fiber laser.iii.Based on the theory of spatial hole burning effect of laser,the virtual folded cavity linear laser has been adopted to control the polarization of different directions lasers in the cavity.Experiment is described in detail about the method of making the laser,including the making of polarization-maintaining fiber gratings and the accuracy of micron fiber cutting method.The result of experiment show that the virtual folded cavity linear laser has effective reduced the hole burning effect of laser.iv.The experiment has studied the self-feedback injection DFB fiber laser.We have reduced the phase noise by 10 d B and suppressed the linewidth of the laser obviously.