I need a ciruit for avalanche photodetector

i am using 1200 nm LED driving using constant current circuit, i have not modulated the led, I want to measure voltage change when light traveling from diffused reflectance optical fiber from fat sample.

I want a APD circuit, like bias voltage, opamp resistor values etc, kindly help.

Does it require cooling to reduce noise? no idea in this field

Data sheet:
Avalanche Photodiode LSIAPD-50
50um InGaAs
Ultra Weak pulse optical detecting
High bandwidth up to 2.5GHZ

The second graph implies normal operation should be in a range 24 to 44 V (reverse bias).
However the table also gives gain specs for breakdown V -1.2, -2, -4V.
Absolute max operating voltage = 0.99×VBR

Typical photodiode schematics show amplification via op amp, with supply a few V. Basic example grabbed from the internet:



It's hard to be sure what is a suitable supply V for your photodiode. It's possible you need to confirm your op amp is okay to operate at 24-44 V.

I'm not sure about your photodiode since my experience is with a cheap photodiode in a circuit operating below 5V. It detects a narrow-beam orange led shining across the room. I don't need 2.5 GHz response nor ultra weak optical detection.

Played a bit with this once. To get avalanche gain you
will probably have to servo the photodiode bias to some
leakage level, below onset of avalanche breakdown.
This is probably cut-and-try unless you have a diode
that's popular for this application and well characterized.

Avalanche operation may need "quenching" after a
detect event, once initiated the same voltage that barely
made it leak will now multiply leakage big time. But for
a pulsed illumination, rather than "single photon" detect
applications you may not need to push so far into the
breakdown regime.