Low-crosstalk 1×40 100 GHz spacing Cascaded Planar Echelle Gratings for Mux/Demux on 3-μm Silicon platform

A 40-channels 100 GHz spaced (de-)multiplexer (Demux/Mux) based on cascaded planar Echelle gratings (PEGs) with low crosstalk and insertion loss is designed and fabricated on 3-μm Silicon-on-Insulator (SOI) platform. The low crosstalk level 40-channels Demux/Mux is effectively achieved by cascading one 1×8 100 GHz spacing cyclic PEG with 800 GHz free spectral range (FSR) and eight 1×5 800 GHz spacing PEGs. The cascaded PEGs provide double filtering to the noise floor thus decreasing the crosstalk. The low-crosstalk and compact 1×40 100 GHz spacing PEG can be employed as Demux and Mux in large-scale photonic integrated circuit (PIC) for large-channel all-optical on-chip system, such as integrated wavelength selective switches (WSSs). The experimental results show that the 1×40 cascaded PEG owns the insertion losses ranging from 2.0 dB to 5.0 dB, low crosstalk < -35 dB, 100 GHz channel spacing and compact size of 25 mm². For data transmission experiments, error-free operation at 10^-9 BER are measured with power penalties < 0.1 dB, < 0.6 dB and < 1.0 dB for 10 Gbit/s, 25 Gbit/s and 35 Gbit/s NRZ-OOK PRBS 2³¹-1 data, respectively.