Eight-wavelength receiver optical subassembly based on silica hybrid integrated technology

A receiver optical subassembly (ROSA) based on hybrid integrated technology is designed and fabricated. It consists of an 8-channel arrayed waveguide grating (AWG) with 2% refractive index difference, two 4-channel positive intrinsic-negative photodetector arrays, and two 4-channel transimpedance amplifier arrays. A flat-top optical spectrum was observed because the output waveguides have a multimode structure, and the average 1-dB bandwidth of AWG channels is 2.8 nm. The insertion loss of all channels is between −1.8 and −2.9  dB, and the cross talk between adjacent channel is less than −20  dB. The ROSA shows a maximum responsivity of 0.4  A  /  W and 3-dB bandwidth of more than 22 GHz for four channels, which can meet the data transmission rate of 25  Gb  /  s. In the future, we will improve the fabrication process to achieve a transmission rate of 8  ×  25  Gb  /  s.