In the COUPE PDK, is the optical I/O interface — grating coupler pitch, position, count, and fiber array geometry — fixed by the process, or free for the designer? Has that tightened across COUPE generations, and does the PDK specify a test interface?

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The optical I/O interface in the COUPE PDK is a hybrid architecture: the coupling mechanism (vertical O-band grating coupler with embedded microlens) and fiber-array pitch (127 µm) are process-fixed, while the array geometry (ch…

In the COUPE PDK, is the optical I/O interface — grating coupler pitch, position, count, and fiber array geometry — fixed by the process, or free for the designer? Has that tightened across COUPE generations, and does the PDK specify a test interface?

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