Performance analysis of 90° hybrid for InP monolithic coherent photodetector at L-band

An optical 90° hybrid monolithic with a 4-channel photodetector array is characterized and analyzed. The fabricated chip exhibits a phase error within ±10° and a common rejection ratio exceeding 13.6 dB over 40 nm range in the L-band. A taper structure is adopted at hybrid inputs and outputs to improve phase error performance by 43.8% and fabrication error tolerance is analyzed numerically to well explain the deviations from theory.