Dear Yahya,

Assume that the LED generates photo flux phi photons/ cm^2/sec which is proportional to its current Iled, then

phi= K Iled , K is constant depends oh the LED,

Then this photon flux will cause a current in the photodiode Iph which is proportional to phi,

Then Iph= S A phi with S the sensitivity of the photodiodeand A its active area.

Therefore Iph= SA K Iled,

Therefore you can represent the photodiode by a current controlled source with the controlling current the led current Iled.

If you have channel then you can multiply the expression of the photocurrent by an attenuation factor alpha, then,

Iph= alpha SA K Iled, also a current controlled source.

Best wishes

Thank you prof. Abdelhalim Zekry

I wanna connect optical transmitter circuit to receiver circuit in Simulink like what is shown in fig attached.

Dear Yahya,

what is the medium of the connection shown in the figure. What is it physically???

or even virtually??

What i proposed is to substitute your photo diode by a current controlled source.

Here the link will be optical through the air or a fiber.

Best wishes