A 120-MHz Bandwidth Linear Signal Transmission System Using Fiber Optics

A complete linear fiber-optic-signal transmission system with an upper frequency limit greater than 150 MHz is described. The transmitter accepts signals in the range of 1 to 15 mV and amplitude modulates an LED. The emitted light signal is carried via fiber optics to a receiver employing a silicon avalanche detector and an amplifier which increases the signal level to the hundreds of millivolts range. Sine-wave bandwidth is 30 kHz-120 MHz (voltage response down to 70 percent), and phase distortion is low, thus preserving pulseshapes. For a transmission path consisting of 15 m of low-cost fiber cable, the dynamic range is 30 dB with harmonic content 30 dB below signal.