11 GHz SCM broadband communications using frequency-locked lasers

A FM modulated frequency-locked laser (FLL) pair for optical communication is reported. The subcarrier (locked) frequencies can be easily tuned from 3 to 11 GHz. Utilizing the FLL modulator within its bandwidth limits, any broadband analog signal, such as TV VHF bands (lower and upper band plus FM radio), CATV channels, and even TV UHF band, can be readily FM modulated on to these very-high-frequency microwave subcarriers. A simple FM demodulation can then be used to recover the original signals. This is directly compatible with standard TV or cable-ready receivers. Digital data in Manchester code format can also be transmitted. The operation of the FLL and the transmission and reception of five TV channels (channels 2 to 6 or substituting one with channel 13) on a 11-GHz subcarrier were experimentally demonstrated. The FLL is based on the concept of double beam modulation (DBM), which can be readily utilized for subcarrier modulated (SCM) multichannel broadband communications.<
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