US5453868A
Expired / Lapsed
US
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Suppression of noise and distortion in fiber-optic systems
Assignee: Emcore Corp
•
Filing: 1994-08-02
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Granted: 1995-09-26
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Expires: 2014-08-02
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 07:54
CPC Classifications
H; H04; H04B; H04B15/00; H04B10/00; H04B10/25; H04B10/2507
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
86 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 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.
Claim 2
Dependent Claim
86 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 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.
Claim 3
Dependent Claim
18 words
The noise and distortion suppression system of claim 1 wherein the chirp generating signal has a single frequency.
Claim 4
Dependent Claim
26 words
The noise and distortion suppression system of claim 2, wherein the chirp generating signal has a frequency less than the lowest frequency in the information band.
Claim 5
Dependent Claim
41 words
The noise and distortion suppression system of claim 3, wherein the chirp generating signal has 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
26 words
The noise and distortion suppression system of claim 2, wherein the chirp generating signal has a frequency greater than the highest frequency in the information band.
Claim 7
Dependent Claim
41 words
The noise and distortion suppression system of claim 5, wherein the chirp generating signal has 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
20 words
The noise and distortion suppression system of claim 2, wherein the chirp generating signal comprises a constant amplitude sine wave.
Claim 9
Dependent Claim
19 words
The noise and distortion suppression system of claim 1, wherein the chirp generating signal comprises a plurality of frequencies.
Claim 10
Dependent Claim
42 words
The noise and distortion suppression system of claim 8, wherein the chirp generating signal has a frequency spectrum 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
22 words
The noise and distortion suppression system of claim 8, wherein the chirp generating signal comprises a constant amplitude frequency modulated sine wave.
Claim 12
Dependent Claim
17 words
The noise and distortion suppression system of claim 8, wherein the chirp generating signal comprises filtered noise.
Claim 13
Dependent Claim
18 words
The noise and distortion suppression system of claim 8, wherein the chirp generating signal comprises pseudo-random digital signals.
Claim 14
Dependent Claim
26 words
The noise and distortion suppression system of claim 1, wherein the chirp generating signal has a frequency in the range from 1 KHz to 300 MHz.
Claim 15
Dependent Claim
26 words
The noise and distortion suppression system of claim 1, wherein the chirp generating signal has 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
107 words
A low noise fiber-optic communications system comprising: 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.
Claim 18
Dependent Claim
107 words
A low noise fiber-optic communications system comprising: 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.
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
63 words
A low noise fiber-optic communications system comprising: 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.
Claim 29
Dependent Claim
63 words
A low noise fiber-optic communications system comprising: 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.
Claim 30
Dependent Claim
28 words
The system of claim 26 wherein the means for applying a signal comprises an oscillator having a modulation frequency lower than the lowest frequency of the information component.
Claim 31
Dependent Claim
28 words
The system of claim 26 wherein the means for applying a signal comprises an oscillator having a modulation frequency greater than the highest frequency in the information component.
Claim 32
Dependent Claim
37 words
The system of claim 26 wherein the means for applying a 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
17 words
The system of claim 26 wherein the means for applying a signal comprises a constant amplitude oscillator.
Claim 34
Dependent Claim
20 words
The system of claim 26 wherein the means for applying a signal comprises means for generating a frequency modulated signal.
Claim 35
Dependent Claim
17 words
The system of claim 26 wherein the means for applying a signal comprises means for generating noise.
Claim 36
Dependent Claim
19 words
The system of claim 26 wherein the means for applying a signal comprises means for generating pseudo-random digital signals.
Claim 37
Dependent Claim
17 words
The noise and distortion suppression system of claim 26 wherein the signal comprises a plurality of frequencies.
Claim 38
Dependent Claim
24 words
The noise and distortion suppression system of claim 26 wherein the signal has a frequency in the range from 1 KHz to 300 MHz.
Claim 39
Dependent Claim
24 words
The noise and distortion suppression system of claim 26 wherein the signal has a frequency in the range from 1 KHz to 200 KHz.
Claim 40
Independent Claim
93 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: 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.
Claim 41
Independent Claim
93 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: 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.
Claim 42
Dependent Claim
33 words
The method of claim 37 further comprising the step of applying a predistorted signal to the laser for canceling 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 |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-09-25 | 1999-03-27 | 1999-09-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-09-25 | 2003-03-27 | 2003-09-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-09-25 | 2007-03-27 | 2007-09-26 | $7700.00 | Window Closed / Lapsed |