transmitter vs reciever!!!!

why do we use different diodes for different purposes...like some of them are used as transmitters of light(visible, ir etc) and others as recievers???
cant the same diode be used for all the purposes...i mean each diode has the property of emitting light when current flows through it and also producing a drop in potential when lights fall on it...
as an example tsop is used as a ir reciever...why cant it be used as transmitter??
and also why only for ir, why not visible light??

To a certain extent, you can. A LED can be used as a photo diode. It is just not optimized to do so.

kchriste said:

To a certain extent, you can. A LED can be used as a photo diode. It is just not optimized to do so.

Click to expand...

Yes. Rather like using a wrench as a hammer. It works, but not very effectively.

Look at the datasheet for a TSOP IR receiver. It is an entire complicated receiver circuit and it cannot be made to transmit.

It's also digital only, but who uses analogue IR transmission these days?