An insertion loss, branching deviation and polarization dependent loss (PDL) as to a 2 N optical splitter using silica-based planar lightwave circuits has been investigated. New key technologies such as (1) a novel wedge type Y-branch, (2) an offset waveguide at the junction between the curved input waveguide and the Y-branch, and (3) low birefringence waveguides due to the appropriate dopant concentration of a cladding, have been devised and incorporated into the splitter. As a result, 2 N optical splitters with low average insertion loss ( 13.2 dB), low branching deviation ( 0.4 dB) and low PDL ( 0.2 dB) have been successfully developed.

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.