Optical receiver photodiode testing using test optical terminal at different location than operational optical terminal

A designed-for-test (DFT) structure for a photonic integrated circuit (PIC), the DFT structure comprising:

• a plurality of photodiodes on a substrate, each photodiode having a first optical terminal and a second, test optical terminal, the second, test optical terminal in a different location than the first optical terminal of the photodiode;
• a different optical component in optical communication with the first optical terminal of each photodiode of the plurality of photodiodes;
• and
• a grating coupler in optical communication with and coupled to the second, test optical terminal of at least one selected photodiode of the plurality of photodiodes,
• wherein each different optical component is in optical communication with the first optical terminal of a respective photodiode via a first optical signal path, and the grating coupler is in optical communication with the second, test optical terminal of the at least one selected photodiode via a second optical signal path separate from the first optical signal path.

A method, comprising:

• optically communicating a test optical signal into a grating coupler in optical communication with a first, test optical terminal of a photodiode in a photonic integrated circuit (PIC), the first, test optical terminal being different than a second optical terminal of the photodiode through which an operational optical signal is optically communicated from an optical component during operation of the PIC;
• and
• determining whether the photodiode is operational based on an electrical output of the photodiode and the test optical signal,
• wherein the grating coupler is in optical communication with and coupled to the first, test optical terminal of the photodiode via a first optical signal path, and wherein the optical component is in optical communication with the second optical terminal of the photodiode via a second optical signal path separate from the first optical signal path.