I think you have missunderstood me a little.

Pipes are great to use to build this kind of things. You should be aware that normal coloured PVC is transparent for IR so you will need to have either black PVC or paint the pipe.

Of course you can try using a LED and a photo resistor. If it works in a reliable way good for you, if it doesnt there are a few options down the road that can help. Modulation is really simple to do if you have a HPWM and a mosfet transistor or just do the modulation in SW on any pin. The receiver for modulation you can usually harvest from any old remotecontrolled device. Look for a black little component with 3 legs.. TSOP48xx or 41xx or anything.. they will all detect a pulse if IR.

Maybe your family has a DVD player that needs to be replaced with a Blueray ...

Build the transmitter tube first and then you can see how far and big the beam becomes. If size is not a problem you can easily get more than 300m transmission range but then you need a proper lense. Big diameter and low magnification.