Studies On Manufacture Of Fiber Mode Field Adaptor

In recent years, the emergence of some novel fibers has brought new vigor andvitality to the area of fiber laser. Large mode area fibers (LMAs) have attracted muchattention as a result of their wide use in high power fiber lasers, and photonic crystalfibers (PCFs) have been the hot spots of domestic and international research because oftheir applications such as the supercontinuum generation. Meanwhile, there areincreasing demands for fiber devices of them. One of the fiber devices is the mode fieldadaptor (MFA), which can reduce the splicing loss with traditional single-mode fibers(SMFs). This dissertation is based on the analysis of the mode field properties of LMAsand PCFs to design and manufacture MFAs for them by a series of techniques andmethods.1. According to the theoretical model of thermally expanded core (TEC) fiber, therelationship between refractive index profile of a TEC fiber and conditions such asheating time is studied. The transmission processing of light in TEC fiber is stimulatedto study the change of mode field. TEC technique is realized for SMFs in experimentand both mode field diameters (MFDs) versus heating time and excess losses duringTEC processing are measured.2. Low-loss MFAs for LMA-SMF with similar cladding diameters are designedand manufactured by TEC technique with0.2dB loss which has achieved practical level.3. Tapering LMAs are analyzed by low-loss tapering adiabaticity condition withthe results showing that the tapering length should be always longer than1cm. Themode field properties of tapering LMAs are analyzed in some detail and the relationshipbetween MFDs and fiber core diameter for LMAs with different numerical apertures(NAs) is stimulated.4. Combining TEC technique and fiber tapering technique, low-loss MFAs forLMA-LMA and SMF-LMA with different cladding diameters are designed andmanufactured with0.3dB loss which has achieved practical level. The output spot ofMFA is also measured and it can be concluded from the spot distribution that thetransmission of fundamental mode light is maintained by MFAs.5. Air hole collapse technique for PCFs is introduced and the change of MFDs forPCFs with different collapse ratios is stimulated. The mode field mismatch betweensmall-core photonic crystal fibers and single-mode fibers is solved by using a taper rigto control air hole collapse with the lowest loss0.64dB.