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US 4,357,713 AGranted
Method and apparatus for reduction of modal noise in fiber optic systems
AssigneeThe United States of America as represented by the Secretary of the Army
InventorsJames C. Blackburn, Jonathan Vanderwall
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Abstract
A dithering means is applied to a laser diode to provide dither modulation along with a signal input thereto. Modal noise, otherwise generated by the system, is reduced by the introduction of dither modulation.
Claims8
An analogue optical signal system with reduced modal noise comprising:
- a source for generating an optical output signal linearly related to a high frequency wide-band input signal;
- means for applying a biasing signal to said source wherein said source is biased to operate above threshold whereby said optical signal system operates as an analogue system;
- transmission means for transmitting said output signal to a receiver;
- and
- means for applying a high frequency signal above the Nyquist rate of said transmitted signal to said biasing signal.
2 more elements
A method of reducing modal noise in an analogue optical signal system comprising the steps of:
- applying an input signal current to a wavelength - current dependent source of single mode optical radiation;
- applying a biasing signal to said source wherein said source is biased above the threshold whereby said source generates an optical output signal linearly related to said input signal;
- transmitting said output signal to an optical receiver;
- and
- modulating said biasing signal with a high frequency signal above the Nyquist rate of said transmitted output signal.
2 more elements
Dependencies are inferred from the claim text.