Multiple Wavelength Band Optical Switching Unit

An input device of a multiple wavelength band optical switch comprising:

• an optical demultiplexer configured to receive light and disperse the received light along a dispersion axis;
• and
• a light director configured to direct light in a first wavelength band to the optical demultiplexer at a first angle of incidence and to direct light in a second wavelength band to the optical demultiplexer at a second angle of incidence, the second angle of incidence being different from the first angle of incidence;
• wherein the difference between the first and second angles of incidence causes the optical demultiplexer to output dispersed spectra of light corresponding to the first and second wavelength bands such that the dispersed spectrum of light corresponding to the first wavelength band is overlapped along the dispersion axis and separated along a switch axis relative to the dispersed spectrum of light corresponding to the second wavelength band, the switch axis being perpendicular to the dispersion axis.