A method of in-wafer testing is provided for a monolithic photonic integrated circuit (PIC) formed in a semiconductor wafer where each such in-wafer circuit comprises two or more integrated electro-optic components, one of each in tandem forming a signal channel in the circuit. The method includes the provision of a first integrated photodetector at a rear end of each signal channel and a second integrated photodetector at forward end of each signal channel. Then, the testing is accomplished, first, by sequentially operating a first of a selected channel electro-optic component in a selected circuit to monitor light output from a channel via its first corresponding channel photodetector and adjusting its operating characteristics by detecting that channel electro-optic component output via its second corresponding channel photodetector to provide first calibration data. Second, by sequentially operating a second of a selected channel electro-optic component in the selected circuit to monitor signal output from the second selected channel electro-optic component via its second corresponding channel photodetector and adjusting its operating characteristics by detecting that channel electro-optic component output via its second corresponding channel photodetector to provide second calibration data. The first and second calibration data for each circuit channel for the selected circuit are then stored for future reference.