Transmission Characteristics And Temperature Sensing Applications Of Photonic Crystal Fibers

The unique light guiding mechanism and flexible structural design of photonic crystal fibers(PCFs)make them widely used in fiber communication,fiber sensing,nonlinear optics,and fiber lasers.The microporous structure in PCFs provides a platform for filling functional materials such as gases,liquids,and solids.These processing methods combined material science and optical make PCFs superior.Filled PCFs are widely used in fiber sensing,fiber modulation devices,nonlinear optics,optoelectronic integration,and other fields.The Filling with liquid is easier to achieve than solids and gases.Based on the excellent properties of PCFs and the improved performance of PCFs liquid filling,the transmission characteristics and applications of PCFs and liquid-filled PCFs were studied theoretically and experimentally.The main research work is as follows:(1)A solid core photonic bandgap fiber with the low loss,single mode,wide bandwidth,and the first band gap transmission locating at 1550 nm,was fabricated by plasma chemical vapor deposition combined with stack drawing method.Besides,the parameters of the fiber structural were optimized by simulation.(2)A simple and easy device was designed and manufactured for liquid filling into the PCFs.Low-loss fusion of liquid-filled PCFs and single-mode fibers is achieved by modifying the fusion method and the fusion program parameters.The temperature transmission characteristics of two low-loss PCFs filled with glycerol were studied experimentally.At 110~280 ?,the transmission spectra exhibit the characteristics of temperature-modulated light intensity,achieving a temperature sensitivity of 0.936 dB/? at 150 ? at 1430 nm.This simple structure can be applied to temperature sensing,fiber attenuators,and fiber filters.(3)The transmission spectra of toluene-filled PCFs were studied experimentally.The filled PCFs were photonic bandgap(PBG)guided light.There are two obvious notches in one of the fiber wide-band gap transmission windows.This spectral notches originates from the resonance absorption of the high refractive index rod.Temperature sensitivity up to-14.63 nm/? is obtained based on the blue shift characteristic of spectral notches with temperature.This simple all-fiber structure temperature modulator can be used for high precision temperature measurement and notch filters.(4)The temperature sensing characteristics of Sagnac interferometer(SI)using the polarization-maintaining photonic crystal fiber(PM-PCF)were studied theoretically and experimentally.The temperature sensitivity ranged from-1.62 to-1.83 nm/?.The fiber birefringence is mainly due to stress birefringence.The good temperature sensitivity of boron-doped PM-PCF SI depends on temperature-sensitive stress birefringence.(5)The boron-doped PM-PCF was filled with glycerol and toluene,respectively.The filled fiber became a hybrid PCFs with improved total internal reflection and PBG light guiding mechanism.Owing to the unique structure and PBG effect on the modulation of fiber birefringence,the temperature sensitivity of SIs based on boron-doped PM-PCF filled with liquid shows a changing process of positive-zero-negative.The glycerol-filled boron-doped PM-PCF SI obtained a temperature sensitivity of-6.34 nm/? at 42 ?,while the toluene-filled boron-doped PM-PCF SI even obtained a high temperature sensitivity up to 19.03 nm/? at 37.5 ?.These SIs,whose interference peaks on the two sides of fixed point(temperature sensitivity is equal to zero)shift for different directions with the temperature,can be used for multi-parameter measurement.(6)Theoretical and experimental studies were executed for the temperature response characteristics of the bandgap transmission spectra of glycerol and toluene filled boron-doped PM-PCF.The sensitivity of the shifts of bandgap edges with temperature is as high as-10.033 nm/?(38 ?~45 ?)in glycerol-filled boron-doped PM-PCF,while ultrahigh as-76.197 nm/?(59 ?~63 ?)in toluene-filled boron-doped PM-PCF.The high sensitivities stem from the high transmission window located in the first band gap.Thermally tunable filled PCFs with PBG effects are available for temperature sensing and tunable bandpass filters.