Clipping distortion controlling circuits
AssigneeNEC Corporation
InventorToshiro Yoshida
Life of this patent
Estimating the term…
Abstract
A clipping distortion controlling circuit for stabilizing an amount of generation of the clipping distortion. A level of the clipping distortion generated by a light-emitting semiconductor laser element is monitored through a light-receiving element and a band-pass filter. A limiter-level of a pre-clipping circuit is changed to be controlled in accordance with the level of the clipping distortion. For this reason, it is capable of coping with the level-fluctuation of the clipping distortion caused by gain-change of an amplifier or by characteristic degradation of the light-emitting element, so that clipping distortion generation has a stabilized characteristic.
Claims14
A clipping distortion controlling circuit including:
- limiting means for restricting an analog input signal to a level below a threshold value and then outputting said restricted analog input signal;
- a semiconductor laser element for converting a combined signal into an optical signal and for transmitting the optical signal, a digital input signal being combined with said restricted analog input signal to form said combined signal;
- and controlling means for changing said threshold value in accordance with a distortion-component of said optical signal.
A method for controlling clipping distortion, comprising the steps of:
- converting an output signal from a light-emitting element by photoelectric-conversion into a first electric signal containing frequency components of clipping distortion;
- obtaining a second signal by selecting only required distortion components to be monitored among frequencies of the clipping distortion contained in said first signal;
- inputting said second signal for detecting the level thereof into a peak-detecting circuit;
- and
- comparing a voltage Vi outputted from said peak-detecting circuit with a reference voltage.
A clipping distortion controlling circuit, comprising:
- a pre-clipping circuit comprising a plurality of diodes connected to ground, said pre-clipping circuit restricting an analog input signal using a threshold value;
- a semiconductor laser element that converts said restricted signal combined with a digital input signal into an optical signal, said element transmitting said optical signal;
- and
- a controller that changes said threshold value in accordance with a distortion-component of said optical signal, said controller comprising a comparator.
Dependencies are inferred from the claim text.