Where is it's receiver.

I found a circuit of transmitter on the Net which below, but no receiver was there.
Any one can help me,
it's out put is train of pulses, how can i convert them back in to audio.
Please guide me in this way.
Any link, any pic, tutorial that can help me plz.

An ordinary "safe" laser diode from a pointer will probably fry in that circuit because it doesn't have any current-limiting. A laser diode that can survive the high current is probably the "unsafe" kind that blind people.

The circuit is the pulse-width-modulation circuit from the datasheet for the LM555, and it uses a 40kHz carrier frequency. many receiver circuits on the web use infrared instead of visible light and are an AM receiver for the 40kHz signal.

you don't need to use a laser at all, give this a read

http://www.bluehaze.com.au/modlight/index.html

the site (slow for me) details building a luxeon powered "photophone", which communicated 104 miles from one mountain top to another

Those guys down under used big lenses and the air between those mountain tops was very thin and clean. Of course they did it in darkness.
It took them 35 years to make it go 104 miles. They could have walked the distance much faster.

I am finding Pulse width Demodulator.
Can u help me in this way?

A simple lowpass filter is a PWM demodulator for that simple transmitter.

Can any one will help me to built it's receiver plz.