Patent US5477368A successfully refreshed from Google Patents.
US5477368A
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High power lightwave transmitter using highly saturated amplifier for residual AM suppression
Assignee: AT&T Inc
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Filing: 1994-12-29
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Granted: 1995-12-19
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Expires: 2014-12-29
Abstract
Abstract Stimulated Brillouin scattering has been effectively suppressed and the effect of residual amplitude modulation has been mitigated in a dithered optical transmitter by injecting the dithered optical signal into an optical device, such as a highly saturated amplifier, whose small-signal intensity response at the dither frequency dampens the residual amplitude modulation thereby decreasing the eye closure (alternatively, increasing the eye pattern opening). The optical device (e.g., the highly saturated amplifier) exhibits a low frequency cutoff (-3 dB) at a frequency greater than or equal to the inverse of the round trip time for a fiber span with the effective optical transmission length into which the optical signal power is launched. The dither rate is generally in the neighborhood of or below the low cutoff frequency.
Inventors
- 👤 Lars E. Eskildsen
- 👤 Per B. Hansen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 12:33
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/25; H04B10/2507; H04B10/2537; H01; H01S; H01S2301/00; H01S2301/02; H01S2301/03; H01S3/00; H01S3/05; H01S3/06; H01S3/063; H01S3/067; H01S3/06754
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
179 words
Optical transmitter apparatus for generating a high power optical signal which is substantially immune from stimulated Brillouin scattering in a transmission medium having a refractive index n and an effective length L eff , the apparatus comprising: a laser having a supplied bias current for generating a continuous wave output signal operating at a predetermined optical carrier wavelength; means connected to the laser for dithering the optical carrier wavelength of the laser at a periodic rate, f d , said periodic rate being greater than or equal to c/2nL eff , where c is the speed of light in a vacuum; an intensity modulator connected to an output of the laser for varying the intensity of the continuous wave output signal; and highly saturated amplifier means responsive to an output signal from the intensity modulator for reducing a peak-to-peak amplitude of residual amplitude modulation on said intensity modulated output signal, said amplifier means having a low cutoff frequency, f c , being greater than or equal to c/2nL eff , and wherein c/2nL eff ≦f d ≦f c .
Claim 2
Dependent Claim
179 words
Optical transmitter apparatus for generating a high power optical signal which is substantially immune from stimulated Brillouin scattering in a transmission medium having a refractive index n and an effective length L eff , the apparatus comprising: a laser having a supplied bias current for generating a continuous wave output signal operating at a predetermined optical carrier wavelength; means connected to the laser for dithering the optical carrier wavelength of the laser at a periodic rate, f d , said periodic rate being greater than or equal to c/2nL eff , where c is the speed of light in a vacuum; an intensity modulator connected to an output of the laser for varying the intensity of the continuous wave output signal; and highly saturated amplifier means responsive to an output signal from the intensity modulator for reducing a peak-to-peak amplitude of residual amplitude modulation on said intensity modulated output signal, said amplifier means having a low cutoff frequency, f c , being greater than or equal to c/2nL eff , and wherein c/2nL eff ≦f d ≦f c .
Claim 3
Dependent Claim
19 words
The optical transmitter apparatus as defined in claim 1 wherein the highly saturated amplifier means is a Raman amplifier.
Claim 4
Dependent Claim
19 words
The optical transmitter apparatus as defined in claim 1 wherein the highly saturated amplifier means is a semiconductor amplifier.
Claim 5
Dependent Claim
22 words
The optical transmitter apparatus as defined in claim 1 wherein the highly saturated amplifier means is an erbium doped optical fiber amplifier.
Claim 6
Dependent Claim
29 words
The optical transmitter apparatus as defined in claim 4 wherein the transmission medium is single-mode optical fiber and the periodic rate is greater than or equal to 5 kHz.
Claim 7
Dependent Claim
20 words
The optical transmitter apparatus as defined in claim 1 wherein the dithering means varies the bias current to the laser.
Claim 8
Dependent Claim
20 words
The optical transmitter apparatus as defined in claim 1 wherein the dithering means varies an operating temperature of the laser.
Claim 9
Dependent Claim
107 words
Method for generating a high power optical signal which is substantially immune from stimulated Brillouin scattering in a transmission medium having a refractive index n and an effective length L eff , the method comprising the steps of: generating an optical output signal having a wavelength which varies at a periodic rate about a predetermined optical carrier wavelength; and reducing a peak-to-peak amplitude of residual amplitude modulation on said optical output signal by amplifying the signal so that the periodic rate occurs in a small signal intensity response region in the neighborhood of or below a low frequency cutoff and above or equal to c/2nL eff .
Claim 10
Dependent Claim
107 words
Method for generating a high power optical signal which is substantially immune from stimulated Brillouin scattering in a transmission medium having a refractive index n and an effective length L eff , the method comprising the steps of: generating an optical output signal having a wavelength which varies at a periodic rate about a predetermined optical carrier wavelength; and reducing a peak-to-peak amplitude of residual amplitude modulation on said optical output signal by amplifying the signal so that the periodic rate occurs in a small signal intensity response region in the neighborhood of or below a low frequency cutoff and above or equal to c/2nL eff .
Claim 11
Dependent Claim
73 words
The method as defined in claim 8 wherein the step of generating further includes biasing a laser via a bias current to produce the optical output signal and dithering the bias current to the laser at a periodic rate, f d , said periodic rate being greater than or equal to c/2nL eff , where c is the speed of light in a vacuum to vary the wavelength of the optical output signal.
Claim 12
Dependent Claim
30 words
The method as defined in claim 9 wherein the generating step further includes the step of modulating the intensity of the optical output signal in response to a data signal.
Claim 13
Dependent Claim
127 words
Optical transmitter apparatus for generating a high power optical signal which is substantially immune from stimulated Brillouin scattering in a transmission medium having a refractive index n and an effective length L eff , the apparatus comprising: an optical source for generating an intensity modulated output signal having a carrier wavelength which varies about a predetermined wavelength at a periodic rate, f d ; and highly saturated amplifier means responsive to the intensity modulated output signal for reducing a peak-to-peak amplitude of residual amplitude modulation occurring substantially related to said periodic rate on said intensity modulated output signal, said amplifier means having a low cutoff frequency, f c , being greater than or equal to c/2nL eff , and wherein c/2nL eff ≦f d ≦f c .
Claim 14
Dependent Claim
127 words
Optical transmitter apparatus for generating a high power optical signal which is substantially immune from stimulated Brillouin scattering in a transmission medium having a refractive index n and an effective length L eff , the apparatus comprising: an optical source for generating an intensity modulated output signal having a carrier wavelength which varies about a predetermined wavelength at a periodic rate, f d ; and highly saturated amplifier means responsive to the intensity modulated output signal for reducing a peak-to-peak amplitude of residual amplitude modulation occurring substantially related to said periodic rate on said intensity modulated output signal, said amplifier means having a low cutoff frequency, f c , being greater than or equal to c/2nL eff , and wherein c/2nL eff ≦f d ≦f c .
Claim 15
Dependent Claim
127 words
Optical transmitter apparatus for generating a high power optical signal which is substantially immune from stimulated Brillouin scattering in a transmission medium having a refractive index n and an effective length L eff , the apparatus comprising: an optical source for generating a continuous wave output signal having a carrier wavelength which varies about a predetermined wavelength at a periodic rate, f d ; and highly saturated amplifier means responsive to the intensity modulated output signal for reducing a peak-to-peak amplitude of residual amplitude modulation occurring substantially related to said periodic rate on said intensity modulated output signal, said amplifier means having a low cutoff frequency, f c , being greater than or equal to c/2nL eff , and wherein c/2nL eff ≦f d ≦f c .
Claim 16
Dependent Claim
127 words
Optical transmitter apparatus for generating a high power optical signal which is substantially immune from stimulated Brillouin scattering in a transmission medium having a refractive index n and an effective length L eff , the apparatus comprising: an optical source for generating a continuous wave output signal having a carrier wavelength which varies about a predetermined wavelength at a periodic rate, f d ; and highly saturated amplifier means responsive to the intensity modulated output signal for reducing a peak-to-peak amplitude of residual amplitude modulation occurring substantially related to said periodic rate on said intensity modulated output signal, said amplifier means having a low cutoff frequency, f c , being greater than or equal to c/2nL eff , and wherein c/2nL eff ≦f d ≦f c .
References Cited (Backward Citations)
US5329396A
Cited
US5373385A
Cited
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