Pwm\Fm conversion?

Question

I'm trying to control an underwater ROV using a conventional radio setup, with the tiny hitch that one obviously cannot transmit radiowaves through water. I was thinking of converting the transmitter output to PWM, piping it down a fiber optic cable to a pulse reciever at the ROV end, reconverting it to FM, and then running it to the reciever.

Now for my problem: how do I convert FM to PWm and back again, in such a way that a conventional radio system won't foul up?

I forgot to mention that the PWm will be piped down the cable by laser.

Answer 1

I don't understand why you want to start with a FM signal, and then need to revert back to a FM signal....?
If you already intend to use a fibre optic cable, then why not just send your digital signals from surface to ROV?
These guys may have some handy stuff to achieve this: http://www.esssales.com/ifo/fiberoptic-kits.html
I can't think of an easy method of converting PWM signals into a FM radio signal.....

Answer 2

PWM can be converted to FM, but FM cannot be converted to PWM without interference or lose of signal.