Wavelength selective switching device and method for selectively transmitting optical signals based on wavelength

An optical device comprising:

• an input optical unit comprising an input to receive optical signals, said input optical unit being configured to selectively rotate one of the polarization components of each of said optical signals to a first polarization state;
• an output optical unit comprising an output to selectively transmit said polarization components of a selected optical signal of said optical signals;
• a diffraction grating optically coupled to said input and output optical units to diffract said polarization components of said optical signals to and from said input and output optical units, said diffraction grating being a reflective type grating;
• an active optical element optically coupled to said diffraction grating, said active optical element being configurable to selectively convert said polarization components of said selected optical signal from said first polarization state to a second polarization state;
• and
• an intermediate optical unit positioned between said diffracting grating and said active optical element, said intermediate optical unit being configured to laterally displace and rotate said polarization components of said selected optical signal in an outgoing direction from said second polarization state to said first polarization state such that said polarization components of said selected optical signal are in said first polarization state at said diffraction grating in both said incoming and outgoing directions, said intermediate optical unit comprising a Wollaston prism and a wave plate positioned such that said polarization components of said selected optical signal in said outgoing direction are selectively transmitted through said wave plate.