Optical waveguide switch with movable reflector in trench

A 2 x 2 MEMS switch 1 is described comprising a chip 3 having at least two V-shaped waveguides 4,5 therein, the vertices of the V-shapes being located at a wall 8 of a trench 2 formed in the chip 3. A MEMS actuator 20 moves a micromirror 15 between first and second positions relative to the wall 8 of the trench, to switch between an express mode (Fig.3(a)) and a switched mode (Fig.3(b)) of operation. The 2 x 2 switch may be replicated to build a 2D switch matrix 40. In a modified embodiment there are three waveguides (60,62,63, fig 6) at the trench and the switch forms a 2 x 2 Add-drop switch which can be used as a building block for an ROADM (70, fig 7). In a further alternative embodiment, instead of using a mirror the actuator 20 is configured to use total internal reflection in the express and switched operation modes (fig 4).