Abstract

Special shaped fibers, including tapered and lensed fiber (TLF) and wedge-shaped fiber (WSF), play an important role in planar lightwave circuit (PLC) technology to attain high efficient coupling with the elliptical optical field of InP based multiple quantum well (MQW) waveguide chips. Output optical field of MQW-PLC, TLF, WSF were numerically analyzed using beam propagation method (BPM) and staircase concatenation method (SCM), respectively. The optimum coupling conditions between WSF and PLC were achieved with wedge angle of 45°, cylindrical endface lens curvature radius of 2.5µm, aspect ratio of PLC elliptical optical spot of 5, and misalignment tolerance of 5.5µm. The focused optical spot diameter of TLF and WSF were measured and calculated based on the transformation relationship between object and image Gaussian beams, which differed less than 3.2% from those of the simulation. 1.55µm wavelength signal was injected into PLC-based coupler chip from SMF, TLF, WSF as input fiber separately with the same SMF as output fiber. The coupling efficiency of WSF-PLC-SMF linkage was 24.827dB and 16.22dB higher than that of SMF-PLC-SMF and TLF-PLC-SMF schemes, and therefore an WSF-PLC-SMF experimental prototype was established for pigtailed PLC packaging technique.