Cselt-centro Studi E Laboratori Telecomunicazioni S.p.a.

Vittorio Seano

Alfredo Fausone

Alberto Brosio

An emitter of unbalanced pulse-modulated energy, specifically a laser, has a feedback circuit including a first branch detecting the mean amplitude of the emitted energy and a second branch detecting the peak amplitude of its pulses. The second branch includes a band-pass filter, centered on the pulse cadence, followed by a peak detector which may comprise a coherent demodulator driven by a square wave whose frequency corresponds to that cadence. The peak detector generates a control signal for a pulse former whose output signals are superimposed upon a biasing signal from the first branch before being fed to the modulating input of the energy emitter.

Performance-stabilization system for an electrical component emitting

A nonlinear signal transducer U, such as a light-emitting diode or a semiconductive laser, is maintained at a suitable operating point by a constant biasing current and receives an electrical input signal by way of a series resistor R from a main amplifier AM of variable gain. The output voltage of the main amplifier is detected and integrated to provide a first reference voltage which is compared with the load voltage of the transducer U in a differential amplifier AE1, forming part of a first feedback loop, to adjust a voltage generator GT controlling the output voltage of the main amplifier AM so as to eliminate any voltage drop across the series resistor R as long as the input signal is absent or has an instantaneous magnitude equal to its mean value. A second feedback loop includes a peak-to-peak detector DP which emits a voltage proportional to the signal amplitude, that voltage being compared with a second reference voltage in a differential amplifier AE2 serving to adjust a current generator GC1 which controls the gain of the main amplifier AM. The second reference voltage may be varied manually or in response to changes in the output of the transducer U.

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Turin, Italy

Vittorio Seano