I am working with a LED and Photodiode detector circuit.

Im concerned that I am getting electricial intererence.

The drive circuit is a uses a buffer amplifier for the LED delivers
provides 5V @50mA.

It is driven from a 6.5V supply

The output from the OP Amp is amplified by a simple(ie 2op amps)
current pre amp and voltage amplifier.

A voltage regulator connected to the 6.5V supply provides 2.5V to the
supplly rails of the Op Amps.

The drive circuit and amplifier circuits are on PCB and are connected
to the LED and PD semicoductor by copper wire.

What precautions can I take to avoid interference.

Graeme