I can only make sense of the circuit if I assume that A7p is a diode. I indeed sketched up the circuit in a simulator and it is working if I apply 12V to yellow and 5V on red, GND on green and I take black as output.
in that way I can get an output on the black wire depending on the voltage (0~20mV) I apply on on the feedback pin of the laser diode. Still no clue about the red/white wire. (the original equipment is connected through a shielded cable, and the red/white is connected to the outer mesh of the cable, but NOT to ground)