Patent ID: 7460787

Claim:
Communication method, comprising the steps of: providing an accurate common clock signal to a sender ( 10 ) and a receiver ( 20 ); in the sender, receiving the common clock signal, generating a carrier wave with a predetermined carrier frequency (f) using said common clock signal as timing reference, modulating the carrier wave with a data signal, and transmitting the modulated carrier wave using an optical light beam ( 13 ); in the receiver, receiving the common clock signal, receiving said optical beam ( 13 ), deriving a detection signal from the said optical beam, generating a reference signal having the same frequency (f) as the said carrier frequency using said common clock signal as timing reference, tuning to the predetermined carrier frequency (f), and deriving the data signal from the said detection signal; wherein the step of tuning to the predetermined carrier frequency (f) comprises the steps of: multiplying said detection signal with said reference signal, filtering the multiplied signal with a lowpass filter, and demodulating the filtered signal.