Connecting a current follower to a Raspberry Pi with an MCP3008
Im not sure what "OED" is but if it's a photodiode you could reverse its bias to -15V and reverse the diode in the circuit. When light hits the diode it will cause current flow out of the op-amp's virtual earth and the op-amp output will rise positively.

You still need to create a negative supply for the photodiode but this will be very low power. Regarding the output level created by the circuit, if your RaPi limit is (say) 3V3 then you can use a resistor potential divider for lowering the output or just run the op-amp from 0V and +3V3 (or whatever power source is available).