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Optical transmitter appts. for optical fibre communication - has electro-absorption modulator being controlled to absorb APC diode laser light corresponding to voltage from combined pre-voltage and modulation signal circuit
Optical transmitter appts. for optical fibre communication - has electro-absorption modulator being controlled to absorb APC diode laser light corresponding to voltage from combined pre-voltage and modulation signal circuit
The transmitter appts. includes a light source (2), an optical electro-absorbtion modulator (4), and an actuating circuit (6). The light source, e.g. a laser diode with automatic power control, has an actuating current directed into it to produce a carrier light corresponding in intensity to the actuating current. The actuating circuit is provided with a pre-voltage circuit (8) and a modulation signal producing circuit (10). The optical modulator receives the carrier light to absorb it in correspondence to a received voltage from the actuating circuit to output an intensity modulated signal. The pre-voltage circuit places an off-set voltage on the optical modulator so that the voltage applied to the optical modulator in a step region produces a stable carrier light. The modulation signal producing circuit receives an input signal to superpose a modulation signal on the offset signal.
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