Patent ID: 9729244
Date: 2017-08-08
CPC Classifications: H04B

Claim:
1. A transmitter with at least one optical modulator adapted to modulate the optical signal output by a laser source to generate a modulated optical signal, wherein the optical signal output by the laser source is tapped and supplied to a monitoring circuit, comprising: an optical front end configured to select signal components of a tapped modulated optical signal, via optical coherent detection, and to convert the selected signal components of the tapped modulated optical signal into analog signals; and at least one analog-to-digital converter (ADC) adapted to perform equivalent-time sampling of the analog signals to provide digital signals to be processed by a processing unit to monitor signal quality of the modulated optical signal, wherein the unmodulated optical signal output by the laser source is tapped by a first polarization maintaining coupler and supplied as a reference signal to the optical front end of the monitoring circuit, wherein the modulated optical signal output by the optical modulator is tapped by a second polarization maintaining coupler and supplied to the optical front end of the monitoring circuit, and wherein the unmodulated optical signal tapped by the first polarization maintaining coupler is supplied as a reference signal to a first polarization beam splitter of the optical front end, and the modulated optical signal tapped by the second polarization maintaining coupler is supplied to a second polarization beam splitter of the optical front end.