Here is most of what we know of the optical sensor.
Measurements & cct dgm: First try with EmonPi - Pulsecount stuck at 1 - #16 by Robert.Wall
Also Adjusting sensitivity of Optical Pulse Sensor - #21 by Kempson
Wire colours: 3.3V power: red, GND: black, output: blue
It certainly runs quite happily on 3.3 V.
From reading the above, you’ll see it doesn’t need a pulse, a steady light (daylight, a torch) is enough, and the output voltage can be read with a multimeter.