[Laser] Mystery Modulated Light

[steve kavanagh]

I was scanning around last night with my new optical receiver and was rather surprised to get a strong clean tone around 1 kHz coming from an apartment building about 200 metres away.  I checked tonight and it is there again. This time I was able to get the computer connected and found the modulation frequency is 1265 Hz (according to Spectran), with a number of harmonics present at 2530 Hz, 3795 Hz, etc.

Any guesses as to what might be emitting this modulated light ?

73,
Steve VE3SMA