Patent ID: 8280256
Filing Date: 2012-10-02
Classification: G02B,H04B

Abstract:
1. An optical hybrid circuit comprising: a multimode interference coupler including a pair of input channels provided at positions symmetrical with each other with respect to a center position in a widthwise direction thereof, a pair of first output channels neighboring with each other for outputting a pair of first optical signals having an in-phase relationship with each other, and a pair of second output channels neighboring with each other for outputting a pair of second optical signals having an in-phase relationship with each other, the multimode interference coupler being adapted to convert quadrature phase shift keying signal light or differential quadrature phase shift keying signal light into the pair of first optical signals having an in-phase relationship with each other and the pair of second optical signals having an in-phase relationship with each other; and a 2:2 optical coupler connected to the first output channels or the second output channels and having two channels on the input side and two channels on the output side, the 2:2 optical coupler being adapted to convert the pair of first optical signals or the pair of second optical signals into a pair of third optical signals having a quadrature phase relationship with the pair of first or second optical signals.