Research On Key Technologies Of Photonic Crystal Fiber Resonator Optic Gyroscope

The Resonant Fiber Optic Gyroscope(RFOG)is a new generation of inertial rotation sensor based on the Saganac effect in the fiber ring resonator,and it could sense the rotation angular rate by detecting the resonance frequency difference between the two beams propagating along the clockwise and counterclockwise directions in the fiber ring resonator.Compared with the Interferometric Fiber Optic Gyroscope(IFOG),the fiber length of RFOG is much shorter,which reduces the volume and the temperature sensitivity of fiber ring resonator.Meanwhile,RFOG has the priorities of high detection accuracy,wide dynamic range,low cost,and so on.All these advantages make the RFOG widely concerned by researchers all over the world,and RFOG has been developed as a potential tendency of FOG in the future.However,restricted by the present optical devices and technologies,RFOG is still in the experimental research stage,and its performance has not yet reached the engineering level,some problems need to be further solved.In order to acquire better resonant performance,the RFOG usually uses the fiber laser with ultra-narrow line-width as its light source.However,it magnifies the optical noises,such as temperature-induced polarization fluctuation,Kerr-effect-induced noise and Faraday-effect-induced noise as well,which could degrade its performance greatly.Fiber ring resonator,as the core section of RFOG,requires the features of high finesse,high polarization extinction ratio and high temperature stability.While the present fiber ring resonators always suffer from low finesse,low polarization extinction ratio and low temperature stability,which limit the performance of RFOG severely.The development of photonic crystal fibers(PCFs),especially the research and development of air-core photonic band-gap PCFs(PBFs)provided a brand-new idea for improving the performance and suppressing the noises of RFOG.In an air-core PBF,the mode is mainly guided in air rather than silica,as a consequence,the bending loss,Kerr effect parameter,Shupe-effect parameter and Faraday-effect parameter in a PBF are much lower than those in a solid fiber.Therefore,the PBF based RFOG can obtain higher temperature stability and lower noise,which has a distinct advantage in improving the RFOG's performance furtherly and solving the problem of bad environment adaptability.Based the above-mentioned advantages in PBF,this research proposes to investigate the performance of PBF based RFOG,and the research starts from the subjects of designing Polarization-Maintaining(PM)PBF and single-polarization-single-mode coupler used in RFOG,and analyzing the temperature-induced polarization fluctuation noise,Kerr-effect-induced noise,Faraday-effect-induced noise in overall PM-PBF resonator based RFOG.The purpose is to improvethe performance of resonator and RFOG.The following main topics are included in this dissertation:(1)The mechanism and key techniques of RFOG are analyzed comprehensively.Firstly,the fundamental principle and performance parameters of RFOG and fiber ring resonator are analyzed on the basis of analyzing the Sagnac effect.Secondly,the influences of different structure parameters on the fiber ring resonators based on different fibers are mainly analyzed comparatively,and the advantages of PM-PBF in improving the performances of fiber ring resonators are demonstrated preliminarily.Finally,some key techniques of RFOG are demonstrated briefly,and the technical solutions used in this paper are introduced briefly.(2)Due to the defects of poor temperature stability,low birefringence and high nonlinear parameter in traditional PM fibers,a kind of PBF with good PM property,ultra-low nonlinear parameter and ultra-low temperature sensitivity is proposed.At first,the demands of PM fibers for fiber ring resonators and RFOGs are analyzed with detail,and the advantages of PM-PBF in RFOGs are also verified.And then,due to the special demands of PBF in RFOG,a kind of PBF with good PM property,ultra-low nonlinear parameter and low loss is proposed.At last,the temperature properties of PM-PBF are investigated in detail based on the full-vector finite element method and the thermo dynamic principles.It is demonstrated that the PM property of this PBF is insensitive to temperature variation.The PBF with good performances could meet the quality demands of fiber ring resonators and RFOGs for PM fibers.(3)Due to the problem of effective coupling in the PM-PBF fiber ring resonator,a kind of single-polarization-single-mode coupler based on dual-core PBF is proposed.Firstly,the potential function of single-polarization-single-mode coupler in fiber ring resonator and RFOG is demonstrated.Secondly,a kind of polarization splitter based on dual-core PCF is proposed,and its properties are analyzed with detail,which provides a very important reference for proposing the directional coupler based on dual-core PBF in the following section.Finally,a kind of directional coupler based on dual-core PBF is proposed,and the influences of structure parameters on the coupling properties in this coupler are mainly investigated,and an single-polarization-single-mode coupler based on dual-core PBF with short length is obtained by optimizing the structure parameters.(4)Due to the temperature-induced fluctuation noise of RFOG,a fiber ring resonator model based on overall PM-PBF is proposed.Firstly,a reflector fiber ring resonator model that based on transmission matrix method is established,and then the temperature-induced polarization fluctuation noise factors in the fiber ring resonator are studied with details.Secondly,an overall-PBF fiber ring resonator is proposed that based on the proposed PM-PBF and directionalcoupler in the former section,and the polarization extinction ratio variation induced by the coupling error in polarization axes of directional coupler is studied as well.Finally,the temperature-induced polarization fluctuation noise in overall-PBF based fiber ring resonator is analyzed specifically,and its distinct advantage in suppressing the temperature-induced polarization fluctuation noise is verified.(5)The Kerr-effect-induced and Faraday-effect-induced noises in overall-PBF based RFOG are studied with details.At the beginning,the Kerr-effect-induced noise factors in the fiber ring resonator are researched with detail,and then the Kerr parameter of PM-PBF is studied.After that,the Kerr-effect-induced noise in the overall-PBF based fiber ring resonator is studied deeply,and its effectiveness in suppressing the Kerr-effect-induced noise of RFOG is verified.Moreover,the Faraday-effect-induced noise factors in the fiber ring resonator are studied in detail,and then the Faraday-effect parameter of the PM-PBF is studied.Finally,the Faraday-effect-induced noise in the overall-PBF based fiber ring resonator is studied,and its effectiveness in suppressing the Faraday-effect-induced noise of RFOG is testified.