Processing circuits for addressed audio signal transmission through GI glass fibers

An audio signal covering the 20-Hz-to-20-kHz frequency range and an address signal consisting of one or more pulse-wave or sine-wave frequency signals, whose frequencies are allocated in the 150-kHz-to-600-kHz frequency range, are mixed together and then applied to a SWFM (square wave frequency modulation) circuit to obtain a SWFM signal. The SWFM signal is transmitted from a sender to a specific receiver through an optical fiber after being converted into an optical signal at 850 nm. This concept has been used in full-duplex communication. The signal-to-noise ratio was greater than 40 dB with a distortion factor of less than 1%