To realize a low-cost WDM transceiver module based on a PLC-platform, simple, assembly techniques have been successfully developed. The formation of index marks with an accuracy of below 0.1 µm has made it possible to mount Opto-electronic devices on the silicon terrace of the PLC-platform by a passive alignment. A newly developed trench formation technique for inserting a 1.3/1.5 µm WDM dielectric filter enabled us not only to ensure a stable WDM function but also to prevent excess loss associated with the dielectric filter scheme. It is found that these two technologies are practically useful to achieve high-performance WDM transceiver module.

Precise direct mounting of laser diode (LD) and photodiode (PD) chips on silica planar lightwave circuits (PLCs) has been investigated for application to transceiver modules. To achieve submicron optical alignment, self-aligned index marks on the PLCs and LDs were directly detected by transmission infrared light. The repeatability of the positioning was measured to be within 0.125 µm. The output power of the resultant module was 0.2 mW at 80 mA. A waveguide-type PD was also mounted in the same way, and module sensitivity of 0.25 A/W was demonstrated.