High port-count free-space wavelength router with ultra-low coherent crosstalk

A free-space 80*80 port wavelength router is reported for the first time. Signal routing from any 40 central input ports to 69 output ports using C-band 0.4 nm-spaced wavelength channels is demonstrated. The high port-count is achieved through low background crosstalk of the holographic concave diffraction grating.