All these components for MEMS switching of optoelectronics require fairly large pieces of silicon, perhaps up to four inches on a side. Packaging these parts will be a major issue. The first issue to address is simply how to handle them and make reliable connections with them. In addition, they will have to be hermetically packaged and, of course, there is the issue of yield in a large, multi-component device. This is controlled so that the light is directed to one of two states by a polarizer.
Polarization diversity is used so that the device is insensitive to input polarization.
In the switched state, however, a thermal actuator creates a small bubble in the trench, and incident light internally reflects into the crossing waveguide. The loss at each intersection accumulates, though the possibility of 512 x 512 arrays with 11.5-dB loss is claimed. Since heat alters the refractive index of the glass, this mechanism provides a simple electrically controlled phase shifter. Differentially altering the phase between arms creates constructive or destructive interference that directs the light to one of two output waveguides. With the technological improvements, the market opportunities for incorporating PAs in long-haul telecom scenarios have provided the needed incentives to drive their cost down.