Simulation And Analysis Of Losses In Photonic Crystal Fibers

Photonic Crystal Fibers (PCFs) are also called Holey Fibers and Microstructured Fibers. PCFs differ from conventional fibers in structure, its appearance had aroused the interests of whole-world research institutions.Plastic Optical Fibers (POF) is a kind of low-cost, light, easily installed, and soft data transmission medium. It is especially well suited to short distance, high connector-density systems such as LANs. The loss limit of PMMA POF at wavelengh 650 nm is about 100 dB/km. So the loss reduction has been the key problem of achieving the practical application.This paper firstly introduces some characters of PCF and photonic bandgap.Secondly the theory of plane-wave expansion and multipole method relevant to this paper is elaborated. Multipole method is a recently developed method. The significant prospect of this method is to calculate mode loss.Thirdly, we employ the air-core PCF structure to overcome the shortage of high material absorption loss of plastics. So mostly light wave can propagate in air core once the light frequency falling in the bandgap band. The relationship of transmission loss and light frequency and the number of cladding rings are worked out by multipole method. After that, bigger radius of hollow core and suitable light frequency can reduce the loss and put the PCFs into use.Lastly, the fundamental mode loss of a special kind of depressed-index core PCF is analyzed. The index of the core is a little smaller than that of the cladding base material, so the fundamental mode loss of short wavelength increases rapidly and leads to the mode cutoff. After the simulation, the relationship of fundamental mode loss with the core index , wavelength and the diameter of cladding air holes is given. And it is found that adjust of the coreindex and the diameter of cladding air holes can control the cutoff wavelength and the fundamental mode loss.