Photonic integrated circuit

A photonic integrated circuit, comprising:

• a substrate;
• a first light source formed on the substrate;
• a first coupler formed over the substrate, the first coupler comprising:
• a first port configured to receive light emitted from the first light source;
• and
• a second port configured to provide a first portion of the light emitted from the first light source;
• and
• a third port configured to provide a second portion of the light emitted from the first light source;
• a shutter variable optical attenuator formed over the substrate, the shutter variable optical attenuator comprising:
• an input port configured to receive the first portion of the light from the first light source;
• and
• an output port configured to block or to provide, based on a control signal, the first portion of the light from the first light source;
• a photodetector array;
• an optical hybrid comprising:
• a first input port configured to receive the second portion of the light from the first light source;
• a second input port;
• and
• multiple output ports coupled to the photodetector array;
• a loop-back waveguide comprising:
• a first port configured to receive the first portion of the light from the output port of the shutter variable optical attenuator;
• and
• a second port configured to provide the first portion of the light to the second input port of the optical hybrid to enable an on-chip testing of the photonic integrated circuit using the first light source and the photodetector array.