Yes, RPi direct pulse input: Directly connecting to Optical Pulse Counter with RPi? - #2 by pb66
(Did a search not reveal this?)
There are 3 connections to the optical sensor. 2 & 5 are +5V & GND respectively, 6 is the output. It is not in fact a pulse, in that there is no control of the shape of the output using (say) a Schmitt trigger. I measure pin 6 at 3 mV in darkness and VCC - 35 mV in reasonably bright light. The output goes to an acceptable ‘high’ state long before the LED on the rear of the sensor lights up.
Measurements: First try with EmonPi - Pulsecount stuck at 1 - #16 by Robert.Wall
Also Adjusting sensitivity of Optical Pulse Sensor - #21 by Kempson