IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
UP-0157900
(2002-05-31)
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등록번호 |
US-7574139
(2009-08-25)
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발명자
/ 주소 |
- Fu, Xiaoli
- Zhang, Genzao
- Shi, Feng
- Wang, Tongqing
- Li, Jinghui
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출원인 / 주소 |
- Oplink Communications, Inc.
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
10 인용 특허 :
2 |
초록
▼
A method and an apparatus for implementing carrier suppressed data format on conventional OTDM modules is provided. Adaptive phase shifting of optical signals traversing one of the tributaries of an OTDM module is performed with feedback loop control. A tapped portion of the input carrier signal is
A method and an apparatus for implementing carrier suppressed data format on conventional OTDM modules is provided. Adaptive phase shifting of optical signals traversing one of the tributaries of an OTDM module is performed with feedback loop control. A tapped portion of the input carrier signal is phase modulated at a frequency fc, and is combined with a tapped portion of the output from the OTDM. A phase shifter controller fed with this combined signal photodetects and band-pass filters the signal around fc to extract the amplitude of the AC component of the envelope of the combined signal, which depends upon the phase difference between successive pulses of the OTDM output. This signal is used to control a phase shifter coupled along one of the tributaries of the OTDM to adjust the phase difference of the signals of the two tributaries so that carrier suppression results.
대표청구항
▼
We claim: 1. An apparatus for providing carrier suppression for the optical output of an optical time domain multiplexing (OTDM) module, the OTDM module operable to interleave a plurality of optical signals traversing a respective plurality of tributaries including a first tributary, the apparatus
We claim: 1. An apparatus for providing carrier suppression for the optical output of an optical time domain multiplexing (OTDM) module, the OTDM module operable to interleave a plurality of optical signals traversing a respective plurality of tributaries including a first tributary, the apparatus comprising: a carrier phase shifter for shifting a phase of a carrier of a particular optical signal traversing the first tributary of the OTDM module; and a feedback loop apparatus for controlling the carrier phase shifter, the feedback loop apparatus controlling a magnitude of the shifting of the phase of the carrier of the optical signal as a function of an optical input signal and an optical output signal to achieve a phase difference of π between each pulse of the interleaved optical output signal. 2. An apparatus for providing carrier suppression for the optical output of an optical time domain multiplexing (OTDM) module, the OTDM module having a tributary, the apparatus comprising: a carrier phase shifter for shifting the phase of a carrier of an optical signal traversing a tributary of the OTDM module; a feedback loop apparatus for controlling the carrier phase shifter, the feedback loop apparatus detecting a phase modulated portion of an original non-pulsed version of the carrier and a portion of the optical output, generating an electrical combined signal which corresponds to an envelope of the sum of the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output, extracting an amplitude of an AC component of the electrical combined signal, and controlling a magnitude of said shifting of the phase of the carrier of the optical signal as a function of said amplitude to achieve a phase difference of π between successive pulses of the optical output. 3. An apparatus according to claim 2 wherein the feedback loop comprises: a first optical power tap for tapping an original non-pulsed version of the carrier generating the portion of an original non-pulsed version of the carrier; a phase modulator for modulating a phase of the portion of the original non-pulsed version of the carrier at a frequency fc generating a phase modulated portion of the original non-pulsed version of the carrier; a second optical power tap for tapping the optical output, generating the portion of the optical output; a detector for detecting the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output, generating an electrical combined signal, said electrical combined signal being a mean intensity of a sum of the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output; and a phase shifter controller for extracting the amplitude of the AC component of the electrical combined signal, and controlling the magnitude of said shifting of the phase of the carrier of the optical signal as a function of said amplitude. 4. An apparatus according to claim 3 wherein the phase shifter controller comprises: a band-pass block having a band-pass filter centered at frequency fc for extracting the amplitude of the AC component of the electrical combined signal; and a control signal calculator for generating from the amplitude a control step size at an update rate for use in controlling the magnitude of said shifting of the phase of the carrier of the optical signal. 5. An apparatus according to claim 4 wherein the phase shifter controller further comprises: an A/D converter for converting the electrical combined signal from the detector into a digital signal for use by the band-pass block; and a phase shifter driver for controlling the magnitude of said shifting of the phase of the carrier of the optical signal at the update rate as a function of the control step size generated by the control signal calculator; wherein the band-pass block includes a low-pass filter for filtering out short term noise from the electrical combined signal. 6. An apparatus according to claim 5 further comprising a modulation clock for clocking the phase modulator with a sinusoidal clock signal, wherein the phase modulator modulates the phase of the portion of the original non-pulsed version of the carrier sinusoidally with a modulation phase range of at least π. 7. An apparatus according to claim 6 wherein the detector is a photodiode. 8. An apparatus according to claim 7 wherein the amplitude of the AC component of the electrical combined signal varies as a sinusoidal function of the phase of the carrier of the optical signal, the sinusoidal function having a maximum, wherein the control signal calculator generates the control step size from the amplitude of the AC component of the electrical combined signal according to the following: if the absolute value of the amplitude is less than a threshold amplitude or if the absolute value of the amplitude divided by the maximum is less than a control resolution, the control step size is zero; otherwise if the absolute value of the amplitude divided by the maximum is less than the absolute value of a previous amplitude divided by the maximum or if the sign of the amplitude is different from the sign of the previous amplitude, the control step size is one half the amplitude divided by the product of the maximum and the control resolution; and otherwise the control step size is the amplitude divided by the product of the maximum and the control resolution; wherein the phase shifter driver determines that the magnitude of said shifting of the phase of the carrier of the optical signal is equal to the product of the control step size and the control resolution. 9. An apparatus according to claim 7 wherein the band-pass filter block comprises a plurality of low-pass filters for multi-length low-pass filtering. 10. An apparatus according to claim 6 wherein the detector comprises: an optical combiner for combining the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output, generating a combined optical signal; and a photodiode for detecting the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output of the combined optical signal, and for generating the electrical combined signal. 11. An apparatus according to claim 10 wherein the OTDM module is implemented on a Lithium Niobate chip wherein the first optical power tap is a 2% external power tap, the second optical power tap is a 5% on chip power tap, the carrier phase shifter is an on chip Lithium Niobate phase modulator, the phase modulator is an on chip Lithium Niobate phase modulator, the optical combiner is an on chip combiner, the photodiode is an external PIN detector, the phase shifter controller is an external controller, and the band-pass filter is a digital electrical finite impulse response filter. 12. A method of providing carrier suppression for an optical output of an optical time domain multiplexing (OTDM) module, the OTDM operable to interleave a plurality of optical signals, the OTDM module having a tributary, the method comprising: shifting the phase of a carrier of a particular optical signal traversing the tributary of the OTDM module; and controlling a magnitude of the shifting of the phase of the carrier of the optical signal as a function of an optical input signal and an optical output signal to achieve a phase difference of it between each pulse of the optical output signal. 13. A method of providing carrier suppression for the optical output of an optical time domain multiplexing (OTDM) module, the OTDM module having a tributary, the method comprising: shifting the phase of a carrier of an optical signal traversing the tributary of the OTDM module; detecting a phase modulated portion of an original non-pulsed version of the carrier and a portion of the optical output; generating an electrical combined signal which corresponds to an envelope of the sum of the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output; extracting an amplitude of an AC component of the electrical combined signal; and controlling a magnitude of said shifting of the phase of the carrier of the optical signal as a function of said amplitude to achieve a phase difference of π between successive pulses of the optical output. 14. A method according to claim 13 further comprising: tapping an original non-pulsed version of the carrier generating the portion of an original non-pulsed version of the carrier; modulating a phase of the portion of the original non-pulsed version of the carrier at a frequency fc generating a phase modulated portion of the original non-pulsed version of the carrier; and tapping a portion of the optical output generating the portion of the optical output; wherein said electrical combined signal is a mean intensity of a sum of the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output. 15. A method according to claim 14 wherein said extracting the amplitude of the AC component of the electrical combined signal comprises band-pass filtering centered at frequency fc, and wherein said controlling the magnitude of said shifting of the phase of the carrier of the optical signal further comprises generating from the amplitude a control step size at an update rate. 16. A method according to the claim 15 wherein said extracting the amplitude of the AC component of the electrical combined signal further comprises: converting the electrical combined signal into a digital signal for use in band-pass filtering; low-pass filtering for filtering out short term noise from the electrical combined signal; and controlling the magnitude of said shifting of the phase of the carrier of the optical signal at the update rate as a function of the control step size. 17. A method according to claim 16 further comprising controlling the modulating of a phase of the portion of the original non-pulsed version of the carrier by clocking with a sinusoidal clock signal, wherein the modulating of a phase of the portion of the original non-pulsed version of the carrier modulates the phase of the portion of the original non-pulsed version of the carrier sinusoidally with the modulation phase range of at least π. 18. A method according to claim 17 further comprising: combining the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output, generating a combined optical signal; and detecting the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output of the combined optical signal. 19. A method according to claim 18 wherein the OTDM module is implemented on a Lithium Niobate chip, wherein the tapping of an original non-pulsed version of the carrier is external 2% power tapping, the tapping of the optical output is on chip 5% power tapping, the shifting of the phase of the carrier of the optical signal is on chip Lithium Niobate phase shifting, the modulating of the phase of the portion of the original non-pulsed version of the carrier is on chip Lithium Niobate phase modulating, the combining of the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output is on chip combining, the controlling of the magnitude of said shifting of the phase of the carrier of the optical signal as a function of said amplitude is performed externally. 20. A method according to claim 17 wherein the amplitude of the AC component of the electrical combined signal varies as a sinusoidal function of the phase of the carrier of the optical signal, the sinusoidal function having a maximum, wherein generating from the amplitude a control step size at an update rate comprises: if the absolute value of the amplitude is less than a threshold amplitude or if the absolute value of the amplitude divided by the maximum is less than a control resolution, the control step size is zero; otherwise if the absolute value of the amplitude divided by the maximum is less than the absolute value of a previous amplitude divided by the maximum or if the sign of the amplitude is different from the sign of the previous amplitude, the control step size is one half the amplitude divided by the product of the maximum and the control resolution; and otherwise, the control step size is the amplitude divided by the product of the maximum and the control resolution; wherein the magnitude of said shifting of the phase of the carrier of the optical signal is determined to be equal to the product of the control step size and the control resolution. 21. A method according to claim 17 wherein low-pass filtering comprises multi-length low-pass filtering. 22. An optical time domain multiplexing (OTDM) module providing carrier suppression for an interleaved optical output of the OTDM module, the OTDM module having a plurality of tributaries including a first tributary, the OTDM module comprising: a carrier phase shifter for shifting the phase of a carrier of an optical signal traversing the first tributary of the OTDM module; and a feedback loop apparatus for controlling the carrier phase shifter, the feedback loop apparatus controlling a magnitude of the shifting of the phase of the carrier of the optical signal as a function of an input carrier signal and an optical output to achieve a phase difference of π between each pulse of the interleaved optical output. 23. An optical time domain multiplexing (OTDM) module providing carrier suppression for the optical output of the OTDM module, the OTDM module having a tributary, the OTDM module comprising: a carrier phase shifter for shifting the phase of a carrier of an optical signal traversing a tributary of the OTDM module; and a feedback loop apparatus for controlling the carrier phase shifter, the feedback loop apparatus detecting a phase modulated portion of an original non-pulsed version of the carrier and a portion of the optical output, generating an electrical combined signal which corresponds to an envelope of the sum of the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output, extracting an amplitude of an AC component of the electrical combined signal, and controlling a magnitude of said shifting of the phase of the carrier of the optical signal as a function of said amplitude to achieve a phase difference of π between successive pulses of the optical output. 24. A method of providing carrier suppression for the optical output of an optical time domain multiplexing (OTDM) module, the OTDM module having N tributaries, the method comprising: for N-1 tributaries of the OTDM module, shifting the phases of the carriers of optical signals traversing the N-1 tributaries; detecting a phase modulated portion of an original non-pulsed version of the carrier and a portion of the optical output; generating an electrical combined signal which corresponds to an envelope of the sum of the phase modulated portion of the original non-pulsed version of the carrier and the portion of the optical output; extracting an amplitude of an AC component of the electrical combined signal; and controlling magnitudes of said shifting of the phases of the carriers of optical signals traversing the N-1 tributaries as a function of said amplitude to achieve a phase difference of π between successive pulses of the optical output.
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