Patents by Inventor Xiang-Dong Cao

Xiang-Dong Cao has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20040156038
    Abstract: A real time chromatic dispersion measurement arrangement measures total amount of chromatic dispersion an optical signal has gone through using a novel technique based on spectrum analyses of dispersion distorted optical signals. A novel method of dispersion measurement and monitoring is used to provide the feedback control signal for tunable dispersion compensation devices. This invention provides a simple cost-effective means for real time chromatic dispersion measurement and monitoring so that optical link dispersion can be managed or monitored dynamically without requiring expensive bit-error rate monitoring.
    Type: Application
    Filed: February 12, 2003
    Publication date: August 12, 2004
    Inventor: Xiang-Dong Cao
  • Publication number: 20040105678
    Abstract: A dynamic channel power equalization arrangement compensates for uneven channel powers of a wavelength multiplexed optical signal using diffractive gratings and semiconductor attenuator. A novel optical design is used to provide power equalization function and optical spectrum analyzer function in one single optical arrangement, as compared to the prior art in which there is only the power equalization function in such devices. This invention provides a simple cost-effective means for a complete solution for managing individual channel powers of wavelength-division multiplexed (WDM) signals.
    Type: Application
    Filed: November 29, 2002
    Publication date: June 3, 2004
    Inventor: Xiang-Dong Cao
  • Publication number: 20040101237
    Abstract: A tunable high-order chromatic dispersion compensation arrangement compensates for dispersion slope in an optical signal transmitted in optical fibers. A pair of parallel diffractive gratings is used to disperse wavelength channels into separate but parallel beams, a novel dispersive element based-on all-optical all-pass filter technology is used to apply required dispersion to different wavelength channels. A novel beam imaging arrangement based on diffractive grating is used to modify the beam width across the dispersive element such that dispersion slope or wavelength-dependent dispersion can be adjusted. Since the tuning mechanism is independent of material properties such as dispersion characteristics of the dispersive element, the resulting tunable dispersion slope compensator is highly reliable to manufacturing tolerance, environmental degradations, and can be massively produced.
    Type: Application
    Filed: November 26, 2002
    Publication date: May 27, 2004
    Inventor: Xiang-Dong Cao
  • Patent number: 6731877
    Abstract: A transmitter terminal in an ultra-long haul optical transmission system receives separate channel input signals in separate ones of a plurality of return-to-zero transmitters (RZTX). Each RZTX generates a corresponding forward error correction (FEC) modulated output signal in a separate channel frequency sub-band including predetermined channel separations from adjacent channel frequency bands. A multiplexing arrangement multiplexes the plurality of channel frequency bands from the RZTXs into separate groups of frequency bands. The groups of frequency bands have predetermined band-gap separations therebetween, and each group of frequency bands has a predetermined separate pre-chirp introduced therein before being multiplexed with all other groups of frequency bands into a single multiplexed output signal. An optical transmission line (OTL) is subdivided into predetermined sections and receives the single multiplexed output signal.
    Type: Grant
    Filed: March 3, 2000
    Date of Patent: May 4, 2004
    Assignee: Qtera Corporation
    Inventor: Xiang-Dong Cao
  • Patent number: 6721512
    Abstract: A compensation arrangement compensates for data signal changes from one of a group consisting of timing jitter dispersion and adaptive chromatic dispersion in an optical signal using a temporal imaging technique. An optical data input signal to the compensation arrangement includes a data pulse for each bit of data that have been subjected to a data signal change. In the compensation arrangement, a clock recovery arrangement generates an electrical clock output control signal including a predetermined phase modulation depth and phase and a data rate of the received optical input data signal. A phase modulator is responsive to the optical input data signal and the electrical clock output control signal from the clock recovery arrangement for generating an optical output signal. In this optical output signal, the phase of the data signal change associated with each data bit is delayed by a predetermined amount.
    Type: Grant
    Filed: March 2, 2000
    Date of Patent: April 13, 2004
    Assignee: Nortel Networks Limited
    Inventor: Xiang-Dong Cao
  • Patent number: 6604871
    Abstract: To compensate for polarization mode dispersion (PMD) induced distortion in an optical signal, an optical pulse is split into two orthogonally polarized pulses. A polarization controller selectively aligns the arbitrarily oriented first and second principal states of polarization of the PMD pulses to match fixed orientations of predetermined first and second principal states of polarization of a beam splitter. The PMD pulses are then coupled to a Mach-Zender interferometer that measures the differential delay between them and selectively compensates for the measured differential delay. An optical combiner combines output the compensator PMP pulses to generate a combined output optical signal.
    Type: Grant
    Filed: April 23, 2002
    Date of Patent: August 12, 2003
    Assignee: Siemens Information and Communications Networks, Inc.
    Inventor: Xiang-Dong Cao
  • Publication number: 20020118422
    Abstract: Polarization Mode Dispersion (PMD) causes an optical pulse to be split into two arbitrarily oriented orthogonally polarized PMD pulses with a differential group delay therebetween in an optical transmission line. To compensate for the PMD induced distortion, a polarization controller in a PMD compensator selectively adjusts the aligning of the received arbitrarily oriented first and second principal states of polarization of the PMD pulses to match fixed orientations of predetermined first and second principal states of polarization of a beam splitter. First and second output paths of the beam splitter are coupled to first and second paths of a Mach-Zender interferometer arrangement. The Mach-Zender interferometer arrangement measures the PMD differential delay between the first and second principal states of polarization of the respective first and second PMD optical pulses, and selectively compensates for the measured differential delay.
    Type: Application
    Filed: April 23, 2002
    Publication date: August 29, 2002
    Applicant: Siemens Telecom Networks
    Inventor: Xiang-Dong Cao
  • Publication number: 20020075536
    Abstract: In an optical regenerator for use in an optical transmission system, an optical input signal to the regenerator comprising N wavelength division multiplexed channel signals is received in a signal synchronizing arrangement which synchronizes the phase of all of the N channels, where N·2. An optical output signal from the signal synchronizing arrangement has N phase-synchronized wavelength division multiplexed channels and is provided as an optical input signal to a nonlinear optical loop mirror (NOLM) arrangement. The NOLM has a high nonlinearity fiber loop that propagates equal parts of the optical input signal from the signal synchronizing arrangement in both a clockwise (CW) and a counterclockwise (CCW) direction. An optical clock signal from a laser having a phase that matches the phase of the CW and CCW propagating signals is multiplexed with the CW signal to provide a 180 degree phase shift between the CW and CCW propagating signals while propagating in the optical fiber loop.
    Type: Application
    Filed: June 30, 1998
    Publication date: June 20, 2002
    Inventor: XIANG-DONG CAO
  • Patent number: 6396607
    Abstract: In an optical regenerator for use in an optical transmission system, an optical input signal to the regenerator comprising N wavelength division multiplexed channel signals is received in a signal synchronizing arrangement which synchronizes the phase of all of the N channels, where N·2. An optical output signal from the signal synchronizing arrangement has N phase-synchronized wavelength division multiplexed channels and is provided as an optical input signal to a nonlinear optical loop mirror (NOLM) arrangement. The NOLM has a high nonlinearity fiber loop that propagates equal parts of the optical input signal from the signal synchronizing arrangement in both a clockwise (CW) and a counterclockwise (CCW) direction. An optical clock signal from a laser having a phase that matches the phase of the CW and CCW propagating signals is multiplexed with the CW signal to provide a 180 degree phase shift between the CW and CCW propagating signals while propagating in the optical fiber loop.
    Type: Grant
    Filed: June 30, 1998
    Date of Patent: May 28, 2002
    Assignee: Siemens Information and Communication Networks, Inc.
    Inventor: Xiang-Dong Cao
  • Patent number: 6337755
    Abstract: In an all-optical regenerator, an optical input signal having N wavelength division multiplexed (WDM) channel signals is demultiplexed and each channel signal is directed onto a separate optical path. In each optical path a clock recovery arrangement is responsive to the associated optical channel signal for generating an electrical clock signal having a frequency corresponding to a bit rate frequency of the optical channel signal. The electrical clock signal is used to generate at least one electrical driving voltage signal. An optical amplitude/phase modulator, including at least three electrodes and first and second Lithium niobate optical waveguides, is responsive to both the optical channel signal and the at least one electrical driving voltage signal for generating an optical output channel signal which is polarization independent.
    Type: Grant
    Filed: November 17, 1998
    Date of Patent: January 8, 2002
    Assignee: Qtera Corporation
    Inventor: Xiang-Dong Cao
  • Patent number: 6295396
    Abstract: An optical arrangement provides dispersion slope compensation to a received dispersion distorted input signal comprising N×M wavelength multiplexed channels. In the optical arrangement, a major dispersion compensating fiber (DCF) provides a first predetermined chromatic dispersion correction value to the N×M wavelength channels. A plurality of fiber Bragg gratings (FBGs) are serially coupled along an optical fiber. Each FBG is arranged to reflect a separate one of N groups of wavelength channels received in the input signal back along the optical fiber in order to provide a second dispersion slope compensating value. Either, the FGBs can chirped to compensate for the dispersion slope within each group of wavelength channels, or each FBG only reflects one group or wavelength channels and small DCFs introduce dispersion slope compensation into the FBG reflected signals.
    Type: Grant
    Filed: June 4, 1999
    Date of Patent: September 25, 2001
    Assignee: Qtera Corporation
    Inventors: Xiang-Dong Cao, Fahri Diner
  • Patent number: 6148122
    Abstract: An optical modulator receives both an optical channel signal and at least one electrical driving voltage signal, and generates an optical output channel signal which is polarization independent. The optical modulator includes at least three electrodes, and first and second lithium niobate optical waveguides interspersed between the electrodes. At least one electrode receives the driving voltage signal to provide a travelling wave therealong. The first optical waveguide receives the optical channel signal, and the second optical waveguide provides the optical output channel signal. A cross splice/delay line interconnects the second end of the first optical waveguide to the first end of the second optical waveguide with polarization maintaining optical fibers, respectively, for introducing a predetermined rotation of TE and TM modes. As a result, polarization components at the second end of the second optical waveguide experience a same amount of phase modulation.
    Type: Grant
    Filed: November 17, 1998
    Date of Patent: November 14, 2000
    Assignee: Qtera Corporation
    Inventors: Xiang-Dong Cao, David Kirk Lewis
  • Patent number: 6130766
    Abstract: A polarization mode dispersion (PMD) compensator compensates for PMD in an optical signal by an automatic tracking of a principal state of polarization (PSP). A polarization controller (PC) receives a dithering optical signal including first and second principal states of polarization (PSPs) and PMD distortion received by the PMD compensator. The PC transforms the first and second PSPs into linearly polarized components, and is responsive to a feedback control signal for aligning the linearly polarized first and second PSPs to first and second polarization axes of the PBS, respectively. A polarization beam splitter (PBS) directs first polarized components of the received dithering optical signal onto a first output path, and directs second orthogonally polarized components of the received dithering optical signal onto a second output path for transmission as a PMD compensator output signal.
    Type: Grant
    Filed: January 7, 1999
    Date of Patent: October 10, 2000
    Assignee: Qtera Corporation
    Inventor: Xiang-Dong Cao
  • Patent number: 6104515
    Abstract: A high-order polarization mode dispersion (PMD) compensation arrangement compensates for PMD in an optical signal using a temporal imaging technique. An optical data input signal to the PMD compensator arrangement includes first and second polarization components for each bit of data that have been subjected to PMD. In the PMD compensation arrangement a clock recovery arrangement generates an electrical clock output control signal including a predetermined phase modulation depth and phase and a data rate of the received optical input data signal. A phase modulator is responsive to the optical input data signal and the electrical clock output control signal from the clock recovery arrangement for generating an optical output signal. In this optical output signal, the phase of the first and second polarization components associated with each data bit are delayed by a predetermined amount.
    Type: Grant
    Filed: February 1, 1999
    Date of Patent: August 15, 2000
    Assignee: Otera Corporation
    Inventor: Xiang-Dong Cao