Report

Multicore Photonic Crystal Fiber Based 1x16 Intensity Splitters/Couplers Dror Malka and Zeev Zalevsky Faculty of Engineering, Bar-Ilan University, Israel. [email protected] 1 Spoiler We demonstrated a new design of a multicore PCF that can divide a single optical power equally into sixteen ports. 2 Photonic Crystal Fiber (PCF) PCF is a new type of optical fiber which obtains its waveguide properties from a periodic arrangement of tiny and closely spaced variations of the refraction index which go along the whole length of fiber 3 Guiding mechanisms 1. Index guiding mechanism (similar to the one in classical optical fibers): If the defect of the structure is realized by removing the central capillary then guiding of electromagnetic wave in a PCF can be regarded as a modified total internal reflection mechanism. 2. Photonic bandgap mechanism: If the central defect is realized by inserting a central air capillary, which has a diameter different than other capillaries (usually bigger), then we can obtain a photonic bandgap. 4 Splitting technique The optical splitter can be obtain by changing the value of the refractive index in z axis Refractive index profile of the intensity splitter 1x8 .XZ cross section (y=0) 5 Splitting technique We use a new technique based on air holes with different sizes. This technique describes the relationship between the distances between neighboring cores and air hole size. By optimization of selecting air hole diameter which corresponds to the distance between the cores we can neglect the other coupling coefficients. 6 PCF Design Silica • d is the hole diameter of large air-holes • pitch- distance between two air holes • d', d'' are the hole diameter of small airholes. • The coupling coefficients are: 1 , 2 , 3 , 4 , 5 , 6 , 7 • , L2 are distances between cores. L1 d' d d '' 0.23, 0.441, 0.303 2.64 m, L1 12.1 m, L 2 20.957 m 7 (a) (b) (c) Refractive index profile of the intensity splitter 1x16: (a) the xy plane. (b) the xz plane. (c) the yz plane 8 Coupled-mode equations Since the structure is symmetrical and cores are identical the amplitudes fulfill: a1 a 2 ,a 3 a 4 ,a 5 a 6 a 7 a 8 a 9 a10 a11 a12 ,a13 a14 ,a15 a16 The coupling characteristics can be describe: da 0 da1 ja 0 j2a11 2a 3 2 , ja1 ja 0 1 2a 5 4 a15 7 dz dz da 3 da 5 ja 3 ja 0 2 2a 5 3 a13 6 , ja 5 ja14 a 3 3 a 9 5 dz dz da 9 da15 da13 ja 9 ja 5 5 , ja15 ja17 , ja13 ja 3 6 dz dz dz 9 Physical conditions In order to obtain a complete transfer of the energy from core 0 to the other cores the following condition should take place: 1 2 3 4 5 6 7 This conditions depends on the geometrical values of the PCF structure. we perform optimizations of the geometric values in order to obtain the required conditions. 10 Simulation Results We solve the PCF structure using RSoft Photonics CAD Suite software which is based on BPM. first step, we launch an optical signal at wavelength of 1.55m into the central core. second step, we calculated the output power of the 16 channels along different axial positions (different values of z). Finally we found the appropriate value for z that satisfies the physical conditions. 11 Simulation Contour Map of Transverse Field Contour Map of Transverse Field 30 1.0 1.0 20 20 10 10 Y (m) Y (m) 30 0 0 -10 -10 -20 -20 -30 -30 -20 -10 0 X (m) (a) 10 20 30 0.0 -30 -30 -20 -10 0 10 20 30 0.0 X (m) (b) The intensity splitting 1x16 of the optical signal simulation of 2D xy cross sections: (a) z=0. (b) z=3.582mm 1.55m 12 Simulation Core 0 Core 1 Core 3 Core 5 Core 9 Core 13 Core 15 The propagation distance z as a function of the normalized power propagation 13 Conclusions • The energy of the optical signal at 1550nm wavelength can be divided into sixteen cores in a PCF structure with dimensions of 60m x 60m x 3.582mm, where the ratio of the total power in each port is about 6.25% of the overall injected power. • The fabrication of this PCF structure is feasible and it is significantly easier to fabricate in comparison to previously published approaches for PCF based couplers/splitters. • The concept can be extended for designing PCF splitter/couplers with higher splitting ratio such as: 1x32 and 1x64. 14