Design and optimization of a near-elliptic cladding photonic crystal fiber with high extinction ratio stability

A new near-elliptic cladding Polarization-maintaining photonic crystal fibre (PM-PCF) with four different hole diameters was proposed. Since the refractive index decreases gradually from x-axis to y-axis, less polarization coupling and high extinction ratio were obtained compared to the conventional PM-PCFs. Secondly, every hole diameter of near-elliptic cladding was optimized to get good performance, considering proper mode field diameter of x-axis and y-axis for better coupling to SLD and smaller confinement loss of the new PCF, high birefringence and high extinction ratio, especially the effects of disturbance on extinction ratio stability. According to series of comparison on different hole diameters and correlation between different holes, the optimum parameters of this new PCF of Λ =2.2μm, d 1 =2μm, d 2 =1.1μm, d 3 =1.7μm and d 4 =1.2μm were derived. The optimized near-elliptic cladding PCF can obtain both high extinction ratio (>29dB) and good extinction ratio stability ( d 3 ) which is useful for practical use.