Claims
- 1. An apparatus for producing optical pulses for use on a transmission link, comprising:
a light source configured to produce an optical signal; and a pulse generator coupled to the light source, the pulse generator configured to receive, for a first channel, the optical signal and a clock signal, the pulse generator configured to modify the optical signal based on the clock_signal to produce an optical pulse having a predetermined pulse shape, the clock signal being associated with the predetermined pulse shape, the predetermined pulse shape being based on a transmission characteristic of the transmission link.
- 2. The apparatus of claim 1, wherein:
the pulse generator includes a Mach-Zehnder modulator responsive to the clock signal, the clock signal includes a swing voltage and a voltage bias, the swing voltage and the voltage bias being selected to substantially maximize a Q-factor associated with the predetermined pulse shape and the transmission link.
- 3. The apparatus of claim 1, wherein:
the optical signal includes a first spectral component; and the pulse generator includes a modulator, the modulator is configured to receive the optical signal and to produce the optical pulse having the first spectral component, a second spectral component and a third spectral component, the second spectral component and the third spectral component being based on the clock signal.
- 4. The apparatus of claim 3, wherein the pulse generator further includes:
a phase shifter coupled to the modulator, the phase shifter configured to receive a phase adjustment signal and the first spectral component of the optical pulse, the phase shifter configured to modulate the first spectral component of the optical pulse based on the phase adjustment signal from the phase shifter.
- 5. The apparatus of claim 4, wherein the pulse generator further includes:
an asymmetric Mach-Zehnder interferometer (AMZI) coupled to the modulator and the phase shifter, the AMZI receiving the first spectral component, the second spectral component and the third spectral component of the optical pulse from the modulator, the AMZI configured to send the first spectral component of the optical pulse to the phase shifter; and a combiner coupled to the phase shifter and the AMZI, the combiner configured to combine the first spectral component of the light pulse with a second spectral component and a third spectral component of the optical pulse.
- 6. The apparatus of claim 1, wherein the pulse generator further includes:
a phase shifter coupled to the modulator, the phase shifter configured to receive a phase adjustment signal, the second spectral component and the third spectral component of the optical pulse, the phase shifter configured to modulate the second spectral component and the third spectral component of the optical pulse based on the phase adjustment signal from the phase shifter.
- 7. The apparatus of claim 1, wherein:
the light source is a comb generator configured to produce the optical signal having a first spectral component, a second spectral component and a third spectral component associated with the first channel; the pulse generator includes a demultiplexer, a modulator and a multiplexer, the demultiplexer being coupled to the light source and the modulator, the modulator being coupled to the multiplexer; the demultiplexer is configured to send the first spectral component of the optical signal to the modulator and to send the second spectral component and the third spectral component of the optical signal to the multiplexer; the modulator is configured to modify the first spectral component of the optical signal; and the multiplexer is configured to combine the modified first spectral component of the optical signal, the second spectral component and the third spectral component of the optical signal for the first channel to produce the optical pulse.
- 8. The apparatus of claim 7, wherein:
the optical signal includes a plurality of spectral components associated with a second channel.
- 9. The apparatus of claim 1, wherein:
the pulse generator is configured to receive a second optical signal and a second clock signal, the second optical signal is received subsequent to the optical signal, the second clock signal is based on an error signal associated with the first optical pulse after being transmitted over the transmission link and the predetermined pulse shape.
- 10. The apparatus of claim 1, further comprising:
a modulator coupled to the pulse generator, the modulator configured to receive a data signal, the modulator configured to phase modulate the optical signal or the optical pulse based on the data signal.
- 11. The apparatus of claim 10, wherein:
the modulator is configured to modulate the optical signal or the optical pulse based on the data signal according to phase-shift keying (PSK), and the first channel is a wavelength-division multiplexed (WDM) channel from a plurality of WDM channels, each WDM channel from the plurality of WDM channels being associated with its own modulation signal.
- 12. The apparatus of claim 10, wherein:
the modulator is configured to modulate the optical signal or the optical pulse based on the data signal according to differential phase-shift keying (DPSK), and the first channel is a wavelength-division multiplexed (WDM) channel from a plurality of WDM channels, each WDM channel from the plurality of WDM channels being associated with its own modulation signal.
- 13. The apparatus of claim 1, further comprising:
a modulator coupled to the pulse generator, the modulator configured to receive a data signal, the modulator configured to amplitude modulate the optical signal or the optical pulse based on the data signal.
- 14. The apparatus of claim 13, wherein:
the modulator is configured to modulate the optical signal or the optical pulse based on the data signal according to on-off keying (OOK), and the first channel is a wavelength-division multiplexed (WDM) channel from a plurality of WDM channels, each WDM channel from the plurality of WDM channels being associated with its own modulation signal.
- 15. The apparatus of claim 1, wherein:
the first channel is an optical-time-division multiplexed (OTDM) channel from a plurality of OTDM channels, each OTDM channel from the plurality of OTDM channels being associated with its own optical pulse and its own modulation signal.
- 16. A method for generating optical pulses for optical communications using a transmission link, comprising:
receiving, for a first channel, an optical signal and a clock signal, the clock signal being associated with a predetermined pulse shape, the predetermined pulse shape being based on a transmission characteristic of the transmission link; and modifying the optical signal based on the clock signal to produce an optical pulse having the predetermined pulse shape.
- 17. The method of claim 16, wherein:
the clock signal including a swing voltage and a voltage bias, the swing voltage and the voltage bias being selected to substantially maximize a Q-factor associated with the predetermine pulse shape and the transmission link.
- 18. The method of claim 16, wherein:
the optical signal is a continuous-wave (CW) signal; and the predetermined pulse shape being a quasi-return-to-zero (quasi-RZ) pulse shape.
- 19. The method of claim 16, further comprising:
forming the optical signal as a continuous wave and having the first spectral component, the optical signal being modified so that the optical pulse has the first spectral component, a second spectral component and a third component, the second spectral component and the third spectral component of the optical pulse being associated with the clock signal.
- 20. The method of claim 16, wherein the modifying includes:
splitting the optical signal onto a first optical path and a second optical path, a first spectral component of the optical signal being associated with the first optical path, a second spectral component and a third spectral component of the optical signal being associated with the second optical path; modifying a phase of the first spectral component of the optical signal on the first optical path based on a phase adjustment signal; and combining the first spectral component of the optical signal associated with the first optical path with the second spectral component and the third spectral component of the optical signal associated with the second optical path.
- 21. The method of claim 16, wherein the modifying includes:
splitting the optical signal onto a first optical path and a second optical path, a first spectral component of the optical signal being associated with the first optical path, a second spectral component and a third spectral component of the optical signal being associated with the second optical path; modifying a phase of the second spectral component and the third spectral component of the optical signal on the second optical path based on a phase adjustment signal; and combining the first spectral component of the optical signal associated with the first optical path with the second spectral component and the third spectral component of the optical signal associated with the second optical path.
- 22. The method of claim 16, further comprising:
forming the optical signal as a pulsed wave and having a first spectral component, a second spectral component and a third spectral component, the modifying step including:
modifying a phase of the first spectral component of the optical signal to produce an optical pulse having the predetermined pulse shape.
- 23. The method of claim 16, further comprising:
receiving, for the first channel, a second optical signal and a second clock signal, the second clock signal being based on an error signal, the error signal based on a transmission of the optical pulse over the transmission link; and modifying the second optical signal based on the second clock signal to produce a second optical pulse having a second predetermined pulse shape, the second predetermined pulse shape being associated with the transmission characteristic of the transmission link a time subsequent to a the predetermined pulse shape.
- 24. The method of claim 16, further comprising:
phase modulating the optical signal or the optical pulse with data using phase-shift keying (PSK), the first channel being a wavelength-division multiplexed (WDM) channel from a plurality of WDM channels, each WDM channel from the plurality of WDM channels being associated with its own modulation signal.
- 25. The method of claim 16, further comprising:
phase modulating the optical signal or the optical pulse with data using differential phase-shift keying (DPSK), the first channel being a wavelength-division multiplexed (WDM) channel from a plurality of WDM channels, each WDM channel from the plurality of WDM channels being associated with its own modulation signal.
- 26. The method of claim 16, further comprising:
amplitude modulating the optical signal or the optical pulse with data using on-off keying (OOK), the first channel being a wavelength-division multiplexed (WDM) channel from a plurality of WDM channels, each WDM channel from the plurality of WDM channels being associated with its own modulation signal.
- 27. The method of claim 16, further comprising:
time-division multiplexing the optical pulse or the optical signal for the first channel with an optical pulse or an optical signal for a second channel, the first channel and the second channel from a plurality of optical-time-division multiplexed (OTDM) channels.
- 28. An apparatus, comprising:
a photodiode configured to receive an optical pulse having a first spectral component, a second spectral component and a third spectral component, the second spectral component and the third spectral component being based on a clock frequency, the photodiode configured to send a first signal having an amplitude and a spectral component with the clock frequency; a filter coupled to the photodiode, the filter having a spectral response associated with the clock frequency; and a detector coupled to the filter, the detector configured to send an error signal based on the amplitude of the first signal.
- 29. The apparatus of claim 28, wherein the filter is a bandpass filter having a spectral response, the clock frequency being within the spectral response of the bandpass filter.
- 30. The apparatus of claim 28, wherein:
the photodiode is configured to receive a plurality of optical pulses including the optical pulse and a second optical pulse, the optical pulse is an un-modulated training pulse, the second optical pulse is phase modulated with data.
- 31. The apparatus of claim 28, wherein:
the clock frequency is a microwave frequency; the first spectral component of the optical pulse has an optical frequency; the second spectral component of the optical pulse has its own frequency corresponding to a sum of the optical frequency and the microwave frequency; and the third spectral component of the optical pulse has its own frequency corresponding to a difference of the optical frequency and the microwave frequency.
- 32. The apparatus of claim 28, wherein:
the amplitude of the first signal is associated with a pulse width of an optical pulse received from a transmission link; and the error signal being associated with a difference between the pulse width of the optical pulse and a predetermined pulse width, the predetermined pulse width being based on a transmission characteristic of the transmission link.
- 33. A method for measuring an optical pulse received from a transmission link, comprising:
detecting a signal based on an optical pulse having a first spectral component, a second spectral component and a third spectral component, the second spectral component and the third spectral component being based on a clock frequency; filtering the detected signal to produce a first signal associated with the clock frequency; and detecting an amplitude of the first signal.
- 34. The method of claim 33, wherein:
the filtering is performed over a bandpass spectral response, the clock frequency being within the spectral response of the bandpass filter.
- 35. The method of claim 33, further comprising:
receiving a plurality of optical pulses including the optical pulse and a second optical pulse, the optical pulse is an un-modulated training pulse, the second optical pulse is phase modulated with data.
- 36. The method of claim 33, wherein:
the clock frequency is a microwave frequency; the first spectral component of the optical pulse has an optical frequency; the second spectral component of the optical pulse has its own frequency corresponding to a sum of the optical frequency and the microwave frequency; and the third spectral component of the optical pulse has its own frequency corresponding to a difference of the optical frequency and the microwave frequency.
- 37. The method of claim 33, wherein:
the amplitude of the first signal is associated with a pulse width of an optical pulse received from the transmission link; and the error signal being associated with a difference between the pulse width of the optical pulse and a predetermined pulse width, the predetermined pulse width being based on a transmission characteristic of the transmission link.
- 38. An apparatus, comprising:
a tunable delay device configured to receive a first amplitude portion of an optical signal; an optical hybrid coupled to the tunable delay device, the optical hybrid configured to receive a second amplitude portion of the optical signal; a detector coupled to the tunable delay device; and a processor coupled to the detector, the processor being configured to calculate a pulse width of the optical signal based on an autocorrelation of the first amplitude portion of the optical signal and the second amplitude portion of the optical signal component.
- 39. The apparatus of claim 38, wherein:
the first amplitude portion of the optical signal including its own plurality of optical pulses, the second amplitude portion of the optical signal including its own plurality of optical pulses, the tunable delay device is configured to iteratively apply an incremental delay from a range of delays to each pulse from the plurality of optical pulses for the first amplitude portion of the optical signal, and the processor configured to calculate the pulse width by measuring overlaps between each corresponding pulse from the plurality of optical pulses for the first amplitude portion of the optical signal and from the plurality of optical pulses for the second amplitude portion of the optical signal over the range of delays.
- 40. The apparatus of claim 38, further comprising:
a polarization controller and a splitter device coupled to the tunable delay device and the optical hybrid, the first amplitude portion of the optical signal and the second amplitude portion of the optical signal being associated with a first polarization of the optical signal.
- 41. The apparatus of claim 40, wherein:
the optical hybrid is a ninety-degree optical hybrid having a first port coupled to the splitter device, a second port coupled to the tunable delay device and a third port coupled to the detector (actually there are four output ports coupled to four detectors, may be two).
- 42. An apparatus, comprising:
a dispersion device configured to receive a first portion of an optical signal on a first optical path and a second portion of the optical signal on a second optical path, the dispersion device configured to introduce a first dispersion into the first portion of the optical signal and a second dispersion into the second optical signal, the first dispersion having its own amplitude and sign, the second dispersion having its own amplitude and sign, the amplitude of the first dispersion being substantially equal to the amplitude of the second dispersion, the sign of the first dispersion being opposite of the sign of the second dispersion; and a balanced detector coupled to the dispersion device.
- 43. The apparatus of claim 42, wherein:
the dispersion device is a chirped Bragg grating having a first side and a second side, the first side of the chirped Bragg grating being disposed within the first optical path, the second side of the chirped Bragg grating being disposed within the second optical path.
- 44. The apparatus of claim 42, wherein:
the dispersion device includes a first chirped Bragg grating and a second chirped Bragg grating, the first chirped Bragg grating being disposed within the first optical path, the second chirped Bragg grating being disposed within the second optical path.
- 45. The apparatus of claim 42, wherein:
the dispersion device includes a first dispersion-compensating fiber (DCF) and a second DCF, the first DCF being disposed within the first optical path, the second DCF being disposed within the second optical path
- 46. The apparatus of claim 42, further comprising:
a first photodetector coupled to the first side of the chirped Bragg grating; a second photodetector coupled to the second side of the chirped Bragg grating; a first bandpass filter coupled to the first photodetector; a second bandpass filter coupled to the second photodetector; a first Schottky diode coupled to the first bandpass filter and the balanced detector; and a second Schottky diode coupled to the second bandpass filter and the balanced detector.
- 47. A method for measuring an optical signal received from a transmission link, the optical signal including a plurality of optical pulses having an estimated pulse width, comprising:
splitting the optical signal into a first amplitude portion associated with a first optical path and a second amplitude portion associated with a second optical path; delaying each pulse from the plurality of pulses associated with the first amplitude portion of the optical signal with an increasing amount of delay corresponding to a fraction of the estimated pulse width of the optical pulse; combining the first amplitude portion of the optical signal with the second amplitude portion of the optical signal using an optical hybrid; detecting an overlap between the first amplitude portion of the optical signal and the second amplitude portion of the optical signal; and determining a pulse width of a pulse from the plurality of optical pulses for the optical signal based on the detected overlaps between the first amplitude portion of the optical signal and the second amplitude portion of the optical signal for the range of delays.
- 48. The method of claim 47, further comprising:
storing the detected overlaps between the first amplitude portion of the optical signal and the second amplitude portion of the optical signal, the range of delays including a final delay corresponding to substantially zero overlap between a pulse of the first amplitude portion of the optical signal and a corresponding pulse of the second amplitude portion of the optical signal.
- 49. A method for measuring an optical signal received from a transmission link, the optical signal including a plurality of optical pulses having an estimated pulse width, comprising:
introducing a first dispersion into a first portion of an optical signal on a first optical path; introducing a second dispersion into a second portion of the optical signal on a second path, the first dispersion having its own amplitude and sign, the second dispersion having its own amplitude and sign, the amplitude of the first dispersion being substantially equal to the amplitude of the second dispersion, the sign of the first dispersion being opposite of the sign of the second dispersion; and detecting the first portion of the optical signal after the introducing of the first dispersion and the second portion of the optical signal after the introducing of the second dispersion to produce a balanced-detected signal.
- 50. The method of claim 49, wherein:
the first dispersion is introduced into the first portion of the optical signal by a first side of a chirped Bragg grating; and the second dispersion is introduced into the second portion of the optical signal by a second side of the chirped Bragg grating.
- 51. The method of claim 49, wherein:
the first dispersion is introduced into the first portion of the optical signal by a first chirped Bragg grating; and the second dispersion is introduced into the second portion of the optical signal by a second chirped Bragg grating.
- 52. The method of claim 49, wherein:
the first dispersion is introduced into the first portion of the optical signal by a first dispersion-compensating fiber (DCF); and the second dispersion is introduced into the second portion of the optical signal by a second DCF.
- 53. A method for adaptively tuning a pulse generator sending an optical pulse over a transmission link, comprising:
sending a plurality of testing signals each being associated with its own dithered value from a plurality of dithered values, each dithered value from the plurality of dither values being associated with at least one from a center value and an offset value; receiving a plurality of optical pulses each being uniquely associated with an testing signal from the plurality of testing signals; detecting a plurality of modulation signals based on the plurality of optical pulses, each modulation signal from the plurality of modulation signals having its own amplitude and a spectral component with a modulation frequency; and calculating a new center value based on the amplitude of modulation signals.
- 54. The method of claim 53, wherein:
the plurality of testing signals includes a first testing signal, a second testing signal and a third testing signal, the sending includes:
sending the first testing signal, the first testing signal being associated with a difference of a center value and an offset value; sending the second testing signal, the second testing signal being associated with the center value; sending the third testing signal, the third testing signal being associated with a sum of a center value and an offset value.
- 55. The method of claim 54, wherein the receiving includes:
receiving an optical pulse based on the first testing signal, the optical pulse for the first testing signal being associated with its own amplitude; receiving an optical pulse based on the second testing signal, the optical pulse for the second testing signal being associated with its own amplitude; and receiving an optical pulse based on the third testing signal, the optical pulse for the third testing signal being associated with its own amplitude.
- 56. The method of claim 53, wherein:
the new center value is calculated by selecting a maximum amplitude from the amplitude of modulation signal for the first testing signal, the amplitude of the modulation signal for the second testing signal and the amplitude of the modulation signal for the third testing signal.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to co-pending U.S. patent application Ser. No. 10/084,057, entitled “Method and System for mitigating nonlinear transmission impairments in fiber-optic communications systems,” filed on Feb. 28, 2002, which claims priority to No. 60/352,991, entitled “Optical communication system and method,” filed on Feb. 1, 2002; both the entirety of which are incorporated herein by reference. This application is also continuation-in-part of the patent application “Light source for generating output signal having evenly spaced apart frequencies,” filed on Jun. 18, 2002, the entirety of which is incorporated herein by reference.
Provisional Applications (2)
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Date |
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60352991 |
Feb 2002 |
US |
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60352991 |
Feb 2002 |
US |
Continuation in Parts (2)
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Number |
Date |
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Parent |
10084057 |
Feb 2002 |
US |
Child |
10215036 |
Aug 2002 |
US |
Parent |
10173579 |
Jun 2002 |
US |
Child |
10215036 |
Aug 2002 |
US |