M $\times$ N Wavelength Selective Switches Using Beam Splitting By Space Light Modulators

We propose a multiple-input-multiple-output (M x N) optical switch with the same optical system as that used for a single-input-multiple-output (1 x N) switch based on a liquid crystal on silicon (LCOS). The proposed M x N switch can route multiple signals simultaneously from different plural inputs to plural outputs, which is called multipole multithrow (MPMT). In addition, our switch configuration can multiply an MPMT switch due to its multicast capacity by beam splitting with holographic phase modulation on the LCOS. We demonstrate a two-degree ROADM using our proposed 4 x 4 wavelength selective switch. The experimental results show that a two-degree ROADM node can be realized by using this switch. The increase in the insertion loss caused by the MPMT switching function is 3 dB due to beam splitting and 3-4.1 dB due to imperfections in the holographic phase modulations. The maximum port crosstalk (XT) is -20.0 dB.