Novel FSK heterodyne single-filter detection system using no IF frequency lock

A frequency-shift keyed (FSK) modulation/single-filter detection system which does not require an intermediate-frequency (IF) locking loop is reported. This system utilizes a laser frequency-locked to an atomic line (krypton 2p/sub 8/-3d/sub 1/" transition at 1.5224 mu m) as both transmitter and local oscillator. As a result, communication can be initiated without any manual adjustment to match the wavelengths of transmitter and local oscillator lasers. No significant degradation in the receiver sensitivity was observed due to the slight frequency dither used to lock the laser frequency to an atomic transition line.<
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