Automatic fiber alignment and coupling using the output of a photodiode and a 3-axis stage
Needed equipment:
- Raspberry Pi
- A PiPlates "DAQC2plate" is installed on the GPIO header. This provides the ADC needed to read intensity from the photodiode (via a Thorlabs photodiode amplifier)
- USB connected to a ThorLabs MDT693B 3-axis piezo controller. The controller haves as a tty device via a serial console, generally at /dev/ttyACM0
- Thorlabs NanoMax stage with at least open loop piezo actuators. This connects only to the above MDT693B.
- We're using the NanoMax 300, which has a 20um range with input voltage from 0-75V
- An appropriate lens (e.g. Edmund high-precision lambda/40 aspheres are good) to focus the beam from free space onto the fiber
- A photodiode that's monitoring power out of the fiber
- A thorlabs photodiode "transimpedance amplifier" which the photodiode plugs into, and from which a BNC cable carrying an analog intensity signal from 0-10V is fed to analogue input pins on the PiPlate.
Installation and Pi confiuration:
- Handy to have the ssh server enabled and vim installed
- Install the "pyhidapi" library by doing "#apt install python3-hid"
- Install the "pyserial" library by doing "pip3 install pyserial"
-
- Clone this repo and make "main.py" executable