The efficiency improvement of a bidirectional optical subassembly

An approach to improve the coupling efficiency of bidirectional optical sub-assembly (BOSA) modules is proposed and experimentally demonstrated. We analyzed the wave-front aberration coefficients of a typical BOSA. It was found that the 45° wavelength filter induces coma and astigmatism, and then it further deteriorates the laser diode (LD) to fiber coupling. We measured the BOSA efficiencies based on a serial of different filters. For a typical 0.5 mm filter, 25% coupling efficiency improvement was achieved by optimizing the filter parameters.