Samer Mohammed has built an optical link that can be used to send audio using an inexpensive laser beam from a laser pointer. Samer has sent in the block diagrams so you can see how the system has been constructed.
“This project demonstrates the use of laser in optical communications. the project consists of a transmitter and receiver that will support a one-way communications link between two separate locations. It is mainly built from a few ICs, operational amplifiers and transistors. It is possible to transmit music, voice and data. The laser used in the transmitter is a simply a laser diode that it used in cheap laser pointers and at the receiver, the laser sensor is a photo-diode.”
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Samer, you can easily build fast FM detectors by using XOR logic ports. The 4046 PLL chip itself uses a XOR port to detect phase (and frequency) change.