Off-Chip Polarization-Diversity $4 \,\, \times \,\, 4$ Si-Wire Optical Switch With Digital DGD Compensation

A $4 \,\, \times \,\, 4$ Si-wire path-independent insertion-loss optical switch having off-chip polarization diversity is demonstrated. The polarization diversity is achieved using off-chip components of polarization-maintaining fiber arrays and fiber-based polarization splitters and combiners. A path-independent on-chip loss of 4.8 ± 0.5 dB is obtained with a polarization-dependent loss below 1 dB. Crosstalk of the switch is measured to be −30 and −20 dB for the bandwidths of 2.9 and 12.9 nm, respectively, for all switch settings. The residual differential group delay (DGD) is <8 ps. Penalty-free 100-Gb/s dual-polarization quadrature-phase-shift-keying signal transmission is also demonstrated with residual DGD compensation by digital signal processing.