Suppression of noise and distortion in fiber-optic systems
First Claim
1. A noise and distortion suppression system for suppressing noise and distortion in a fiber-optic communications system having a semiconductor source laser connected to an optical fiber and an RF input signal with an information frequency band for modulating the laser, the system comprising:
- means for applying a combination RF signal and chirp generating signal having at least one frequency to the source laser for modulating the laser and for changing the instantaneous frequency of light from the laser for minimizing noise and distortion due to reflections.
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Accused Products
Abstract
Noise and distortion due to scattering and reflection in a fiber-optic communications system are suppressed by modulating the optical frequency of (chirping) a laser light source to broaden the spectrum of the laser light output. The broader spectrum spreads the noise produced by an unchirped source over a broader band. A noise and distortion suppression system includes a chirp signal generator coupled to the signal path of an RF input signal carrying information to modulate the laser optical output. In some cases, the frequency of the chirp generating signal may result in second-order intermodulation products falling within the information band. In such cases, the RF input signal is predistorted to offset the expected distortion products.
92 Citations
38 Claims
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1. A noise and distortion suppression system for suppressing noise and distortion in a fiber-optic communications system having a semiconductor source laser connected to an optical fiber and an RF input signal with an information frequency band for modulating the laser, the system comprising:
means for applying a combination RF signal and chirp generating signal having at least one frequency to the source laser for modulating the laser and for changing the instantaneous frequency of light from the laser for minimizing noise and distortion due to reflections. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A low noise fiber-optic communications system comprising:
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a semiconductor laser having an RF input for producing a modulated optical spectrum; a receiver for producing an RF output signal with an information frequency band substantially similar to an information band of the RF input signal; an optical fiber coupling the laser to the receiver; means for generating a chirp generating signal; means for applying the chirp generating signal to the laser for minimizing noise and distortion due to reflections; and means for predistorting the RF input signal so that laser distortion of the information component of the RF output signal created by the chirp generating signal is canceled. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A low noise fiber-optic communications system comprising:
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a semiconductor laser; an input electrical signal path connected to the laser for modulating the laser with an information component having an informational frequency bandwidth; and means for applying a signal to the laser for changing the frequency of light from the laser for minimizing noise and distortion due to reflections without distorting the information component. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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37. A method for suppressing noise and distortion in a fiber-optic communications system having a semiconductor laser with an optical output coupled to a remote receiver, the method comprising the steps of:
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modulating the laser optical output; applying a chirp generating signal to the laser for changing the instantaneous frequency of light from the laser for minimizing noise and distortion due to reflections; transmitting light from the laser to the receiver by way of an optical fiber; and demodulating the laser optical output at the receiver for producing a low noise electrical output signal. - View Dependent Claims (38)
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Specification