US5430569A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Suppression of noise and distortion in fiber-optic systems
Assignee: Emcore Corp
•
Filing: 1992-05-22
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Granted: 1995-07-04
•
Expires: 2012-05-22
Abstract
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.
Inventors
- 👤 Henry A. Blauvelt
- 👤 John S. Frame
- 👤 Amnon Yariv
- 👤 David B. Huff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 22:40
CPC Classifications
H; H04; H04B; H04B15/00; H04B10/00; H04B10/25; H04B10/2507
Claims Analysis
Total Claims: 39
Claim 1
Independent Claim
132 words
A noise and distortion suppression system for suppressing noise and distortion in a fiber-optic communications system having a semiconductor source laser connected to optical fiber and an RF input signal with an information frequency band for modulating the laser, the system comprising: means for generating a chirp generating signal having at least one frequency; means for generating a combination RF signal and chirp generating signal by combining the chirp generating signal with the RF signal; and means for applying the combination RF signal and chirp generating signal to the source laser for broadening the optical spectrum and modulating the laser, for changing the frequency of light from the laser for minimizing interference due to light backscattered into the laser from an optical fiber and for introducing an optical signal to the fiber.
Claim 2
Dependent Claim
132 words
A noise and distortion suppression system for suppressing noise and distortion in a fiber-optic communications system having a semiconductor source laser connected to optical fiber and an RF input signal with an information frequency band for modulating the laser, the system comprising: means for generating a chirp generating signal having at least one frequency; means for generating a combination RF signal and chirp generating signal by combining the chirp generating signal with the RF signal; and means for applying the combination RF signal and chirp generating signal to the source laser for broadening the optical spectrum and modulating the laser, for changing the frequency of light from the laser for minimizing interference due to light backscattered into the laser from an optical fiber and for introducing an optical signal to the fiber.
Claim 3
Dependent Claim
23 words
The noise and distortion suppression system of claim 1 wherein the chirp generating means generates a chirp generating signal comprising a single frequency.
Claim 4
Dependent Claim
31 words
The noise and distortion suppression system of claim 2, wherein the chirp generating means generates a chirp generating signal having a frequency less than the lowest frequency in the information band.
Claim 5
Dependent Claim
46 words
The noise and distortion suppression system of claim 3, wherein the chirp generating means generates a chirp generating signal having a frequency which, when combined with any frequency in the information band, causes no second-order intermodulation products which fall within the bandwidth of the information band.
Claim 6
Dependent Claim
31 words
The noise and distortion suppression system of claim 2, wherein the chirp generating means generates a chirp generating signal having a frequency greater than the highest frequency in the information band.
Claim 7
Dependent Claim
46 words
The noise and distortion suppression system of claim 5, wherein the chirp generating means generates a chirp generating signal having a frequency which, when combined with any frequency in the information band, causes no second-order intermodulation products which fall within the bandwidth of the information band.
Claim 8
Dependent Claim
27 words
The noise and distortion suppression system of claim 2, wherein the means for generating a chirp generating signal comprises means for generating a constant amplitude sine wave.
Claim 9
Dependent Claim
24 words
The noise and distortion suppression system of claim 1, wherein the chirp generating means generates a chirp generating signal comprising a plurality of frequencies.
Claim 10
Dependent Claim
46 words
The noise and distortion suppression system of claim 8, wherein the chirp generating means generates a chirp generating signal having a frequency which, when combined with any frequency in the information band, causes no second-order intermodulation products which fall within the bandwidth of the information band.
Claim 11
Dependent Claim
29 words
The noise and distortion suppression system of claim 8, wherein the means for generating a chirp generating signal comprises means for generating a constant amplitude frequency modulated sine wave.
Claim 12
Dependent Claim
24 words
The noise and distortion suppression system of claim 8, wherein the means for generating a chirp generating signal comprises means for generating filtered noise.
Claim 13
Dependent Claim
25 words
The noise and distortion suppression system of claim 8, wherein the means for generating a chirp generating signal comprises means for generating pseudo-random digital signals.
Claim 14
Dependent Claim
31 words
The noise and distortion suppression system of claim 1, wherein the chirp generating means generates a chirp generating signal having a frequency in the range from 1 KHz to 300 MHz.
Claim 15
Dependent Claim
31 words
The noise and distortion suppression system of claim 1, wherein the chirp generating means generates a chirp generating signal having a frequency in the range from 1 KHz to 200 KHz.
Claim 16
Dependent Claim
23 words
The noise and distortion suppression system of claim 1, further comprising means for predistorting the RF signal so that laser distortion is canceled.
Claim 17
Dependent Claim
151 words
A low noise fiber-optic communications system comprising: a semiconductor laser for producing an optical spectrum; means for applying an RF input signal with an information band to the laser for modulating the laser; a receiver coupled to the laser for producing an RF output signal with an information frequency band substantially similar to the information band of the RF input signal; means for generating a chirp generating signal having at least one frequency; means for applying the chirp generating signal to the laser for broadening the optical spectrum of the laser and changing the frequency of light from the laser for minimizing interference due to light backscattered into the laser from an optical fiber; and means for predistorting the RF input signal as a function of the chirp generating signal so that laser distortion of the information component of the RF output signal created by the chirp generating signal is canceled.
Claim 18
Dependent Claim
151 words
A low noise fiber-optic communications system comprising: a semiconductor laser for producing an optical spectrum; means for applying an RF input signal with an information band to the laser for modulating the laser; a receiver coupled to the laser for producing an RF output signal with an information frequency band substantially similar to the information band of the RF input signal; means for generating a chirp generating signal having at least one frequency; means for applying the chirp generating signal to the laser for broadening the optical spectrum of the laser and changing the frequency of light from the laser for minimizing interference due to light backscattered into the laser from an optical fiber; and means for predistorting the RF input signal as a function of the chirp generating signal so that laser distortion of the information component of the RF output signal created by the chirp generating signal is canceled.
Claim 19
Dependent Claim
23 words
The system of claim 16, wherein the means for generating a chirp generating signal comprises means for generating a constant amplitude sine wave.
Claim 20
Dependent Claim
24 words
The system of claim 16, wherein the means for generating a chirp generating signal comprises means for generating a constant amplitude frequency modulated signal.
Claim 21
Dependent Claim
20 words
The system of claim 16, wherein the means for generating a chirp generating signal comprises means for generating filtered noise.
Claim 22
Dependent Claim
21 words
The system of claim 16, wherein the means for generating a chirp generating signal comprises means for generating pseudo-random digital signals.
Claim 23
Dependent Claim
31 words
The system of claim 16, wherein the chirp generating means generates a chirp generating signal having a frequency which is less than the bandwidth of the RF output signal information band.
Claim 24
Dependent Claim
27 words
The system of claim 16, wherein the chirp generating means generates a chirp generating signal having a frequency in the range from 1 KHz to 300 MHz.
Claim 25
Dependent Claim
27 words
The system of claim 16, wherein the chirp generating means generates a chirp generating signal having a frequency in the range from 1 KHz to 200 KHz.
Claim 26
Dependent Claim
17 words
The system of claim 16, wherein the means for predistorting the RF signal comprises an amplitude modulator.
Claim 27
Dependent Claim
38 words
The system of claim 24, wherein the amplitude modulator comprises an input for receiving the chirp generating signal and an output coupled to a signal path of the RF input signal for amplitude modulating the RF input signal.
Claim 28
Dependent Claim
77 words
A low noise fiber-optic communications system comprising: a semiconductor laser; means for applying an RF signal with an information component having an informational frequency bandwidth to the laser; and means for applying a chirp generating signal to the laser for optical frequency modulating the laser without distorting the information component of the RF signal and changing the frequency of light from the laser for minimizing interference due to light backscattered into the laser from an optical fiber.
Claim 29
Dependent Claim
77 words
A low noise fiber-optic communications system comprising: a semiconductor laser; means for applying an RF signal with an information component having an informational frequency bandwidth to the laser; and means for applying a chirp generating signal to the laser for optical frequency modulating the laser without distorting the information component of the RF signal and changing the frequency of light from the laser for minimizing interference due to light backscattered into the laser from an optical fiber.
Claim 30
Dependent Claim
30 words
The system of claim 26 wherein the means for applying a chirp generating signal comprises an oscillator having a modulation frequency lower than the lowest frequency of the information component.
Claim 31
Dependent Claim
30 words
The system of claim 26 wherein the means for applying a chirp generating signal comprises an oscillator having a modulation frequency greater than the highest frequency in the information component.
Claim 32
Dependent Claim
39 words
The system of claim 26 wherein the means for applying a chirp generating signal comprises an oscillator having a modulation frequency which causes no intermodulation products with any frequency in the information component to fall within the informational bandwidth.
Claim 33
Dependent Claim
19 words
The system of claim 26 wherein the means for applying a chirp generating signal comprises a constant amplitude oscillator.
Claim 34
Dependent Claim
22 words
The system of claim 26 wherein the means for applying a chirp generating signal comprises means for generating a frequency modulated signal.
Claim 35
Dependent Claim
19 words
The system of claim 26 wherein the means for applying a chirp generating signal comprises means for generating noise.
Claim 36
Dependent Claim
21 words
The system of claim 26 wherein the means for applying a chirp generating signal comprises means for generating pseudo-random digital signals.
Claim 37
Independent Claim
113 words
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: applying an RF input signal having an informational bandwidth to the laser for modulating the laser optical output; applying a chirp generating signal to the laser for broadening the spectrum of the laser optical output and changing the frequency of light from the laser for minimizing interference due to light backscattered into the laser from an optical fiber; and demodulating the laser optical output at the receiver for producing a low noise RF output signal substantially similar to the RF input signal.
Claim 38
Independent Claim
113 words
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: applying an RF input signal having an informational bandwidth to the laser for modulating the laser optical output; applying a chirp generating signal to the laser for broadening the spectrum of the laser optical output and changing the frequency of light from the laser for minimizing interference due to light backscattered into the laser from an optical fiber; and demodulating the laser optical output at the receiver for producing a low noise RF output signal substantially similar to the RF input signal.
Claim 39
Dependent Claim
40 words
The method of claim 34 wherein the step of applying a chirp generating signal to the laser comprises predistorting the RF input signal for canceling any laser distortion caused by modulating the laser optical output with the chirp generating signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1998-07-03 | 1999-01-02 | 1999-07-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-07-03 | 2003-01-02 | 2003-07-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-07-03 | 2007-01-02 | 2007-07-04 | $7700.00 | Window Closed / Lapsed |