Optical coupling efficiency studies of passively aligned CWDM optical modules

A compact low-cost passively aligned optical sub-assembly (OSA) with four different optical transmission channels is fabricated for CWDM transceiver module. A silicon optical bench (SiOB) with V-groove, and U-groove was fabricated with dimensional accuracy of ±1 μm. A 125 μm diameter single mode optical fiber (SMF) and a 250 × 250 × 100 μm3 laser diode (LD) was passively aligned on the SiOB using adhesive and solder preform respectively. Process related coupling losses due to the shifting of fiber during the adhesive attachment and cure process is demonstrated. Analytical studies were carried out to find the effect of parameters such as dimensions of laser diode, SiOB and attachment process on the coupling losses of the module. It was found that dimensional uncertainty of SiOB and the attachment process parameters are the crucial parameters for the coupling loss in passive alignment assembly of CWDM transceiver. An optical coupling loss of 25% was observed due to the shift of fiber during the attachment process and it was in good agreement with the analytical calculated results.