A configurable inputoutput interface is described that can be programmed to handle any one of a plurality of interfaces that embedded applications might have, including communication protocols and bus interfaces, data acquisition from multiple sensors and actuators, and controls of various motors. The light guide may be positioned to create uniformly dispersed illumination and to eliminate backscatter from the viewing window. The transmitter and sensor are mis-aligned with the air flow at the point where the beam contacts the filter. When the laser incident beam has an angle, the ripple spacing can be changed by changing a scanning direction.