A record performance metric waveguide grating router (WGR) design with a 200 GHz free spectral range (FSR) capable of resolving sub-GHz resolution spectral features is developed for a fine resolution photonic spectral processor (PSP). The WGR’s FSR was designed to support subchannel add/drop from a superchannel of 1 Tb/s capacity. Due to fabrication imperfections, we introduce phase corrections to the light beams emerging
from the 250 waveguides of the WGR output using a liquid crystal on silicon (LCoS) phase spatial light modulator (SLM) placed in an imaging configuration. A second LCoS SLM is located at the Fourier plane, for arbitrary spectral amplitude and phase manipulations. The PSP is utilized in multiple system transmission experiments, such as flexible spectral shaping and subcarrier drop demultiplexing with sub-GHz spectral resolution.