Planar lightwave circuit eight-channel CWDM multiplexer with <3.9-dB insertion loss

This paper describes the demonstration of an improved eight-channel coarse wavelength-division multiplexer. The fully packaged channel losses range from 2.3 to 3.9 dB, the 1-dB bandwidth is 16.3 nm, and the crosstalk is <-28dB. This silica-waveguide device could have very low cost.

I. Introduction

Coarse wavelength-division multiplexing (CWDM) has a channel spacing of 20 nm and is designed for use with uncooled transmitter lasers. Currently, all major commercially available CWDM multiplexers/demultiplexers (from here on called “mux”) are based on thin-film filter (TFF) technology. This is because a CWDM mux must have very wide flat passbands on a constant wavelength-spacing grid with low loss. Previously, only TFFs could achieve this for more than four channels. The drawbacks to TFFs are they require tedious filter characterization and hand assembly and hermetic packages. Silica-waveguide technology, on the other hand, can be mass produced, needs only fiber attachment, and does not need a hermetic package. Thus, silica-waveguide-based CWDM muxes could potentially be manufactured at a lower cost than TFF-based ones.