The Beat-length Measurement And Sensing Of Polarization-maintaining Few-mode Fiber Based On Polarized Interference

Polarization-maintaining few-mode-fiber(PM-FMF),which has the advantages of both single-mode polarization-maintaining fiber(PMF)and few-mode-fiber(FMF),is a new kind of fiber that is envisioned to have applications in optical communications and sensors.PM-FMF can realize multiple-input-multiple-output(MIMO)-less spacedivision-multiplexing(SDM)transmission.PM-FMF can also realize simultaneous measurement of strain and temperature.Thus the characteristic measurement of PMFMF is very important.In this thesis,we make a theoretical study about PM-FMF.We propose an accurate beat-length measurement of PM-FMF based on polarization interference and demonstrate a simple multi-parameter optical sensor based on a PMFMF,for the first time.The research in this article mainly include the following aspects:1.The basic theory of PM-FMF was introduced.The properties of modes in fibers,including the procedure of mode solving,mode field distribution,optical attenuation,dispersion and coupling property,polarization-maintaining property,mode excitation and mode conversion,etc.,were discussed in detail.2.The theory and measuring method of beat-length were introduced.An accurate beat-length measurement of PM-FMF based on polarization interference was proposed and the formula of PM-FMF was deduced.The reasons of the disturbances(including mode crosstalk)were analyzed.We simulated the beat-length results of PMF and PMFMF,respectively.3.We set up the beat-length measurement system of PM-FMF.The beat-length of a 3-mode PANDA PM-FMF was measured.The methods of Fourier transform and filtering were experimentally verified and the operation requirement can be lower.4.A simple multi-parameter optical sensor based on a PM-FMF was proposed and the sensing theory of strain and temperature was introduced.Single-parameter sensing of temperature and strain was experimentally accomplished.Then the optical fiber sensor based on the PM-FMF can discriminatingly sense temperature and strain by using those sensing parameters.