Polarisation independent 8*8 waveguide grating multiplexer on InP

A polarisation independent InP-based 8×8 multiplexer is realised by designing the free spectral range to exactly match the TM-TE shift. The device exhibits a channel spacing of 88.4 GHz (0.71 nm), a crosstalk of −20 dB and a channel bandwidth of 39 GHz (0.31 nm). The insertion loss is below 5 dB for all eight channels.