An approach to improve the coupling efficiency of bidirectional optical subassembly (BOSA) modules is proposed and experimentally demonstrated. We analyzed the wavefront aberration coefficients of a typical BOSA. It was found that the 45-deg wavelength filter induces coma and astigmatism, and then it further deteriorates the laser diode to fiber coupling. We measured the BOSA efficiencies based on a series of different filters. For a typical 0.5-mm filter, 25% coupling efficiency improvement was achieved by optimizing the filter parameters.
Dynamic DWDM channel blocking and equalizing is proposed based on liquid crystal (LC) and bulk grating technology. A dispersion compensation and enhancement unit is employed so that low center-frequency shift small footprint could be achieved at the same time. The inter-channel crosstalk is also studied. With the optimized design of dispersion unit and LC module, a 32-channel, 100-GHz spacing sample is demonstrated with the insertion loss (IL) of 5.5 dB and 45dB extinction ratio. Application of our device to reconfigurable optical add-and-drop (ROADM) network is discussed