Optical coupling efficiency of bidirectional transceiver sub-module with refractive index control

Conventionally, optical communication modules for subscriber have been composed of transmitter and receiver as separated or combined requiring two lines of optical fibers to constitute a network. To realize the fiber-to-the-home (FTTH), it is necessary to make the cheaper and more compact module as well as to reduce the fiber installation cost. In this study, an accurate silicon optical bench (SiOB) has been designed for passive integration of bidirectional transceiver sub-module. Optical coupling between the transceiver chip and a single mode fiber is accomplished by aligning an acute angle-faceted fiber on the V-groove of SiOB to the front facet of the flip-chip bonded chip. Transmitted light from the laser diode of the transceiver chip is coupled into fiber core as in usual buff coupling, while receiving light from the fiber is refracted downward by Snell's law and absorbed into pin-PD's photosensitive area after being reflected at the metal coated V-groove side-wall.