Patent ID: 8743370
Filing Date: 2014-06-03
Classification: H04B

Abstract:
1. A demodulator comprising: a substrate; a collimator emitting a modulated light beam subjected to differential phase shift keying; a delay interferometer; a photodetector; and a light guiding element, wherein the collimator is disposed on a bump of the substrate and the delay interferometer and the photodetector are disposed on a flat region of the substrate, wherein the delay interferometer includes: wherein the light reflection means reflects the first branched light beam and the second branched light beam respectively such that the difference in the optical path length between the first branched light beam and the second branched light beam becomes a length corresponding to one symbol of the modulated light signal, wherein the light branch element combines the first branched light beam and the second branched light beam reflected by the light reflection means to generate a first interference light beam and a second interference light beam, wherein the photodetector outputs an electrical signal which is in proportion to the difference in intensity between the first interference light beam and the second interference light beam generated by the delay interferometer, wherein the light guiding element guides the first interference light beam or the second interference light beam generated by the delay interferometer to the photodetector, and wherein the height of the light guiding element with respect to the substrate is smaller than the height of the optical axis of each of the first branched light beam and the second branched light beam before being reflected by the light reflection means with respect to the substrate, and is greater than the height of the optical axis of each of the first branched light beam and the second branched light beam after being reflected by the light reflection means with respect to the substrate.