increasing range of photo-diode detector with little voltage
To null out the Sun, and the 120Hz, connect a Darlington collector-output to bottom of PhotoDiode. Drive the Darlingon base from an inverted (inverted by another OpAmp, pivoting around VDD/2) version of the OpAmp buffer. We want a very slow feedback, to null out the Sun.

Have this inverting OpAmp use 0.1UF Cfeedback, and 1MegOhm Rin. Tie Rin to output of first OpAmp; this new opamp+darlington nulling-loop will attempt to keep the first OpAmp at 50% of VDD.
Tie Pin+ to 10k+10K voltage divider, producing VDD/2.
Use 10Kohm from OpAmp to base of the Darlington. 

This integrating-nulling-loop may let you avoid those lossy filters in front of the photodiode.

You may need to switch from NRZ bitstreams to a code that implements exactly 50% duty cycle{Miller? Manchester?}.  With that, you can speed up the nulling loop and better null more and more optical interference.







simulate this circuit &ndash; Schematic created using CircuitLab