Ikier laser power loss

If your machine is using 5V TTL that would be correct for measurements when using a meter. It’s also possible your machine uses 3.3V logic so the range then would be 0-3.3V. For PWM control it’s the duty cycle that determines power level, not the absolute voltage.

But in either case you can infer duty cycle from the voltage value once you determine the signal voltage. 50% power will be 2.5V for a 5V system and 1.65V for a 3.3V system.

Note that there are other more exotic voltages used for signaling but the approach doesn’t change.