Linien for Side-of-fringe locking

[Celesoar]

I need to lock the microring resonator to a stable laser. For simplicity, I want to use only PID to lock the microring resonator at its side-of-fringe, like the following picture:

If I don't give the set point off-set and just feedback the swept spectroscopy signal to FAST IN 1, I want to know whether the PID-only mode can give the set point automatically.