[Laser] Simple optical beacon experiment in San Diego

[Charles Pooley]

Kerry Banke <kbanke at qualcomm.com> wrote:
   
  >Charles - I do have a wide-band optical link built around a laser pointer. 
>The system is reasonably flat out to 500 MHz using the approach you 
>describe but of course the sensitivity is very much reduced due to the low 
>load impedance of 50 ohms to get the frequency response.
  ------------------------------------------
   
  As I said in previous post, how about using the PD as the capacitor of an LC tank?
  The impedance at resonance will be much higher, and you get a sirst tuning effect to boot.  Some tuning effect would be available by varying the bias voltage on the PD, or even an AFC loop could be used to lock it to the incoming signal frequency.
   
  If you are using a laser, you can use an interference filter to improve background light problems.  These filters art "tunable" by tilting at an angle from the normal.  The pass wavelength of a 660 nm filter will shift to 650 when tilted a little over 15 degrees.
   
  Charles Pooley KD6HKU