Polarization-insensitive four-channel coarse wavelength-division (de)multiplexer based on Mach–Zehnder interferometers with bent directional couplers and polarization rotators

A polarization-insensitive four-channel coarse wavelength-division multiplexing (CWDM) (de)multiplexer based on Mach-Zehnder interferometers is proposed and demonstrated. By utilizing the bent directional couplers and the polarization rotators, the CWDM (de)multiplexer could work for both transverse electric and transverse magnetic polarizations. The measurement results of the fabricated devices show that the 1-dB bandwidth is ∼15 nm for dual polarizations, and the polarization dependent losses are <∼0.5 dB for all four channels.