Apparatus for increasing directivity and lowering background light in tap detectors

摘要

A tap detector monitors an optical signal propagating through a waveguide as a portion of the optical signal is tapped and directed to the monitor detector. A precisely formed grating structure formed within the waveguide surface causes a portion of the propagating optical signal to be coupled out of the waveguide at a particular angle. The grating structure produces an angular separation of light propagating through the waveguide in opposite directions and which is directed out of the waveguide by the grating structure. A monitor detector is positioned to detect the light tapped from the optical signal and to avoid being influenced by any other signals that may be propagating in a direction opposite the optical signal and that are diffracted out of the waveguide by the grating structure.