POLARIZATION-INDEPENDENT INP WDM MULTIPLEXER DEMULTIPLEXER MODULE/

We report the design, fabrication, packaging, and characterization of a polarization independent integrated optical InP multiplexer/demultip lexer module. The device is based on a vertically etched diffractive g rating and separates four channels with 4 nm spacing in the 1.55 mu m window. An n(-)/n(+)-InP layer structure with very low birefringence r esults in a shift of the passbands between transverse electric (TE) an d transverse magnetic (TM) polarization of less than 0.1 mm. With a se lf-aligned flip-chip mounting technique light is optically coupled fro m the input and output waveguides to an array of lensed single mode fi bers with a coupling efficiency of more than 80%. The packaging includ es temperature control that allows fine tuning of the channel passband s over 5 nm. Optical crosstalk is always better than -17 dB and fiber to fiber losses of 15 dB are achieved. The module has been successfull y implemented in a 4 x 2.5 Gb/s WDM transmission system.