Design Of Photonic Crystal Fibers And Its Application

The theoretical design of photonic crystal fiber (PCF s) and its applicationcharacteristics have been analyzed. Three kinds of novel PCF s, which can beapplied in different applications, have been proposed, and the analysis of theircharacteristics has been carried out. The special work is as follows:1. In order to improve the low threshold of the stimulated Raman scattering insingle mode fiber in Raman distributed temperature sensor (Raman DTS), we havedesigned a large-mode-area photonic crystal fiber (PCF) with two cladding layers,and carried out a detailed investigation on its optical characteristics, such assingle-mode characteristic, effective mode area, and the bending characteristics. Byappropriate design, the designed PCF can has a cutoff wavelength below1250nm, alarger mode area of~288μm2, and only a small bending loss of0.25dB/m under abending radius of5cm. Using the designed PCF as the sensing fiber in Raman DTS,it can greatly improve the Nonlinear threshold in the sensing fiber (about3.4timescompared to that of the conventional single-mode fiber), and the signal to noise ratioin Raman DTS.2. In the face of the fiber in the project of the fiber to house, which can work atsmall bending radius with low bending losses, we have designed abending-insensitive single-mode photonic crystal fiber (PCF) based on the existenceof a triangular core and two cladding layers, and carried out a detailed investigationon its optical characteristics, such as single-mode characteristic, effective mode area,and the bending characteristics. Simulation results show that the designed PCF canhave an effectively single-mode operate, a small bending loss below0.15dB/m forthe bending radius of5mm, as well as a stable effective mode area of85μm2, whichcan connect well with the SMF. It can be used in some special occasions requiringsmall bending radius, such as the data center wiring system, the high speed network,especially for the project of the Fiber to The House.3. For the liquid filled HiBi-PCF temperature sensor, we have proposed a novel structureof an alcohol not full-filled HiBi-PCF, and investigated their novel characteristics. Usingthe alcohol not full-filled HiBi-PCF inserted into a Sagnac interferometer as the sensinghead, we can get the temperature variations by monitoring one resonant wavelength of theSagnac interferometer shift depending on temperature. By considering the influences of the birefringence–temperature dependence of the alcohol-filled HiBi-PCF, the thermoexpansion of alcohol, and the group birefringence of the HiBi-PCF itself, we can predictthat the resonant dip wavelengths blue-shift with temperature increasing, which is contraryto what had been reported. Experimental results show that the phenomenon is consistentvery well with our theoretical expectation, and the temperature sensitivity is estimated to be-1.1nm/°C. What’s more, the sensitivity of the proposed temperature sensor is related tothe initial value of L2/L1.