THREE PORT TRANSCEIVER

1 . An optical coherent transceiver comprising a monolithically integrated electrical and optical circuit having a substrate with a planar surface onto which is formed a polarization and phase-diversity coherent receiver and a polarization and phase-diversity modulator, and said optical coherent transceiver including only three optical Input/Output ports employing only three grating couplers, the first grating coupler optically connected to the polarization-diversity receiver, the second grating coupler optically connected to the receiver and the input of the polarization-diversity modulator, and the third grating coupler optically connected to the output of said modulator;

wherein one of the grating couplers couples in to the transceiver a modulated signal, a second one of the grating couplers couples in to the transceiver a continuous-wave signal, and a third one of the grating couplers couples out a modulated signal.

2 . The optical transceiver according to claim 1 wherein the three grating couplers are connected to a fiber assembly including optical fiber having a bend radius less than 8 mm.

3 . The optical transceiver according to claim 1 wherein all three grating couplers are 2-D grating couplers.

4 . The optical transceiver according to claim 1 wherein one grating coupler is a 1-D grating coupler and the other two are 2-D grating couplers.

5 . The optical transceiver according to claim 1 wherein the substrate is a Si substrate.

6 . The optical transceiver according to claim 2 wherein the fiber assembly is vertical to within 2 degrees of the substrate surface.

7 . The optical transceiver according to claim 1 wherein TOPS are included in the combining paths of a grating coupler such that VOA functionality is provided.

8 . The optical transceiver according to claim 8 further comprising an external laser module that provides the cw signal.

9 . The optical transceiver according to claim 9 wherein said laser cw signal provides both transmitter and local oscillator function