Patents by Inventor Cedric F. Lam

Cedric F. Lam 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: 20110293279
    Abstract: Techniques, devices and systems for optical communications based on wavelength division multiplexing (WDM) that use tunable multi-wavelength laser transmitter modules.
    Type: Application
    Filed: May 26, 2010
    Publication date: December 1, 2011
    Applicant: Google Inc.
    Inventors: Cedric F. Lam, Hong Liu
  • Publication number: 20110292953
    Abstract: Techniques, devices and systems for optical communications based on wavelength division multiplexing (WDM) that use tunable multi-wavelength laser transmitter modules.
    Type: Application
    Filed: May 26, 2010
    Publication date: December 1, 2011
    Applicant: GOOGLE INC.
    Inventors: Hong Liu, Cedric F. Lam
  • Patent number: 7860393
    Abstract: A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands.
    Type: Grant
    Filed: November 24, 2008
    Date of Patent: December 28, 2010
    Assignee: AT&T Intellectual Property I, LP
    Inventors: Martin Birk, Patrick P. Iannone, Kenneth C. Reichmann, Nicholas J. Frigo, Cedric F. Lam
  • Patent number: 7725028
    Abstract: A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands.
    Type: Grant
    Filed: September 17, 2007
    Date of Patent: May 25, 2010
    Assignee: AT&T Intellectual Property I, LP
    Inventors: Martin Birk, Patrick P. Iannone, Kenneth C. Reichmann, Nicholas J. Frigo, Cedric F. Lam
  • Patent number: 7466919
    Abstract: A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands.
    Type: Grant
    Filed: June 7, 2006
    Date of Patent: December 16, 2008
    Assignee: AT&T Corp.
    Inventors: Martin Birk, Patrick P. Iannone, Kenneth C. Reichmann, Nicholas J. Frigo, Cedric F. Lam
  • Patent number: 7466918
    Abstract: Wavelength assignment schemes that provide full-connectivity in RANs with fixed-tuned OADMs. In the first scheme, wavelengths are assigned to nodes according to Hadamard code, and in the second scheme, bands of contiguous wavelengths are assigned to nodes. Simulation results show that on the average, the Hadamard wavelength assignment schemes approach the performance of RANs with OADMs that add-drop all wavelengths, while saving 50% of the TDM terminals. The saving of TDM terminals by using wavelength tunable OADMs vary in different cases. Tunable OADMs are advantageous for lower traffic granularity and more interactions of a RAN with the outside network.
    Type: Grant
    Filed: September 24, 2007
    Date of Patent: December 16, 2008
    Assignee: AT&T Corporation
    Inventors: Cedric F. Lam, Aleksandra Smiljanic
  • Patent number: 7366417
    Abstract: A method and a system in which selected wavelengths of a wavelength division multiplexed (WDM) signal are modulated with multicast data for multicasting data services on an optical network. The WDM signal is received from a hub node of the optical network, such as a unidirectional ring network or a bi-directional ring network. A four-port wavelength crossbar switch (4WCS) selectably switches selected wavelengths from the optical network to a modulator loop. The modulator loop includes a multicast modulator that modulates the selected plurality of wavelengths with the multicast data. Each modulated wavelength is then switched back to the optical network by the 4WCS switch, and sent to a plurality of subscriber nodes of the optical network. This architecture allows a facility provider to be physically separated from a content provider, and affords the flexibility of selectively delivering multicast content to individual subscribers.
    Type: Grant
    Filed: January 10, 2006
    Date of Patent: April 29, 2008
    Assignee: AT&T Corp.
    Inventors: Mark D. Feuer, Nicholas J. Frigo, Cedric F. Lam
  • Patent number: 7286760
    Abstract: Wavelength assignment schemes that provide full-connectivity in RANs with fixed-tuned OADMs. In the first scheme, wavelengths are assigned to nodes according to Hadamard code, and in the second scheme, bands of contiguous wavelengths are assigned to nodes. Simulation results show that on the average, the Hadamard wavelength assignment schemes approach the performance of RANs with OADMs that add-drop all wavelengths, while saving 50% of the TDM terminals. The saving of TDM terminals by using wavelength tunable OADMs vary in different cases. Tunable OADMs are advantageous for lower traffic granularity and more interactions of a RAN with the outside network.
    Type: Grant
    Filed: March 3, 2003
    Date of Patent: October 23, 2007
    Assignee: AT&T, Corp.
    Inventors: Cedric F. Lam, Aleksandra Smiljanic
  • Patent number: 7286761
    Abstract: A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands.
    Type: Grant
    Filed: July 30, 2001
    Date of Patent: October 23, 2007
    Assignee: AT&T Corp.
    Inventors: Martin Birk, Patrick P. Iannone, Kenneth C. Reichmann, Nicholas J. Frigo, Cedric F. Lam
  • Patent number: 7127181
    Abstract: Link robustness, chromatic dispersion and polarization mode dispersion (PMD) immunity can be improved in fiber optical system by using a method for receiving an optical double sideband signal over an optical fiber system, comprising the steps of splitting the received optical double sideband signal into an upper sideband signal and a lower sideband signal, photodetecting the upper sideband and the lower sideband, equalizing the photodetected upper sideband signal and the lower sideband signal, and combining the equalized upper sideband signal with the equalized lower sideband signal. While PMD compensation is envisioned as a major application, one may also use the method and system for chromatic dispersion compensation or dispersion slope compensation in high bit rate systems, i.e. using dispersion compensation fiber (DCF) for coarse compensation and diversity receiver with electrical equalizer for fine tuning.
    Type: Grant
    Filed: August 4, 2005
    Date of Patent: October 24, 2006
    Assignee: AT&T Corp.
    Inventors: Alan H. Gnauck, Cedric F. Lam, Sheryl L. Woodward
  • Patent number: 7085495
    Abstract: A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands.
    Type: Grant
    Filed: July 30, 2001
    Date of Patent: August 1, 2006
    Assignee: AT&T Corp.
    Inventors: Martin Birk, Patrick P. Iannone, Kenneth C. Reichmann, Nicholas J. Frigo, Cedric F. Lam
  • Patent number: 7027733
    Abstract: A method and a system in which selected wavelengths of a wavelength division multiplexed (WDM) signal are modulated with multicast data for multicasting data services on an optical network. The WDM signal is received from a hub node of the optical network, such as a unidirectional ring network or a bi-directional ring network. A four-port wavelength crossbar switch (4WCS) selectably switches selected wavelengths from the optical network to a modulator loop. The modulator loop includes a multicast modulator that modulates the selected plurality of wavelengths with the multicast data. Each modulated wavelength is then switched back to the optical network by the 4WCS switch, and sent to a plurality of subscriber nodes of the optical network. This architecture allows a facility provider to be physically separated from a content provider, and affords the flexibility of selectively delivering multicast content to individual subscribers.
    Type: Grant
    Filed: December 27, 2001
    Date of Patent: April 11, 2006
    Assignee: AT&T Corp.
    Inventors: Mark D. Feuer, Nicholas J. Frigo, Cedric F. Lam
  • Patent number: 6959154
    Abstract: Link robustness, chromatic dispersion and polarization mode dispersion (PMD) immunity can be improved in fiber optical system by using a method for receiving an optical double sideband signal over an optical fiber system, comprising the steps of splitting the received optical double sideband signal into an upper sideband signal and a lower sideband signal, photodetecting the upper sideband and the lower sideband, equalizing the photodetected upper sideband signal and the lower sideband signal, and combining the equalized upper sideband signal with the equalized lower sideband signal. While PMD compensation is envisioned as a major application, one may also use the method and system for chromatic dispersion compesation or dispersion slope compensation in high bit rate systems, i.e. using dispersion compensation fiber (DCF) for coarse compensation and diversity receiver with electrical equalizer for fine tuning.
    Type: Grant
    Filed: November 28, 2000
    Date of Patent: October 25, 2005
    Assignee: AT&T Corp.
    Inventors: Alan H. Gnauck, Cedric F. Lam, Sheryl L. Woodward
  • Patent number: 6871020
    Abstract: A power spectrum measurement system and a method monitor a power spectrum of N-channels in an M-channel wavelength division multiplexed optical communication network, where N is less than or equal to M. An add-drop node in the network drops a channel and adds a channel for transmitting data on the network. The added channel has the same wavelength as the dropped channel. The power of the added channel is controlled to minimize crosstalk. The power spectrum measurement system includes a detection circuit and a processing circuit. The detection circuit is an inexpensive, scalable circuit for detecting the power of each channel. The processing circuit is connected to the detection circuit and calculates the power of each channel based upon the power detected by the detection circuit. The processing circuit also calculates power of the added channel for minimizing crosstalk.
    Type: Grant
    Filed: April 3, 2001
    Date of Patent: March 22, 2005
    Assignee: AT&T Corp.
    Inventors: Mikhail Boroditsky, Nicholas J. Frigo, Cedric F. Lam
  • Patent number: 6751372
    Abstract: A four-port wavelength-selective crossbar switch generates an add/drop wavelength signal from a wave division multiplexed (WDM) signal using a plurality of double-sided reflectors that selectively reflects a selected wavelength channel signal of the WDM signal through optical circulators to provide low crosstalk between the dropped and added wavelength signals. The switch also reduces the number of WDM MUX-DEMUX required to one half that compared to a traditional approach. Furthermore, the switch can be designed to be wavelength cyclic with individual free spectral ranges that can be independently set to either through or add/drop states.
    Type: Grant
    Filed: December 27, 2001
    Date of Patent: June 15, 2004
    Assignee: AT&T Corp
    Inventors: Mark D. Feuer, Nicholas J. Frigo, Cedric F. Lam
  • Patent number: 6697574
    Abstract: An optical telecommunications network suitable for carrying broadcast and switched services. The network includes a wavelength division multiplexing (WDM) coupled to a waveguide grating router (WGR). In accordance with the invention, an adjacent input port is connected with the same optical content. Thus, its outputs are adjacent (or wrapped around). According, the optical power in each of the broadcast bands at the outputs remains the same but is reduced by a factor of two in power for each channel but occupying twice as many channels. This has the effect of increasing the SNR by a factor of two.
    Type: Grant
    Filed: April 2, 2001
    Date of Patent: February 24, 2004
    Assignee: AT&T Corp.
    Inventors: Nicholas J. Frigo, Patrick P Iannone, Cedric F. Lam, Kenneth C Reichmann
  • Patent number: 6661976
    Abstract: A method and system for generating and transmitting optical signals with only one sideband. Single-sideband optical signal transmission reduces the signal impairment effects associated with dispersion. Such transmission also increases the spectral efficiency of optical transmission systems. Single-sideband modulation also makes possible electrical compensation for optical link dispersion during transmission. Single-sideband modulation is generated using the modulating data signal and its Hilbert transform, which is approximated by a tapped-delay time filter. Line coding is used to remove the low-frequency content in the modulating data signal, avoiding the inefficiencies of tapped-delay-line filter approximated Hilbert transformers at low frequencies. Line coding can also help optical single side band signal generation and transmission using a simple optical filter instead of Hilbert transformers.
    Type: Grant
    Filed: January 5, 2000
    Date of Patent: December 9, 2003
    Assignee: AT&T Corp.
    Inventors: Alan H. Gnauck, Cedric F. Lam, Sheryl Leigh Woodward
  • Publication number: 20020131689
    Abstract: A four-port wavelength-selective crossbar switch generates an add/drop wavelength signal from a wave division multiplexed (WDM) signal using a plurality of double-sided reflectors that selectively reflects a selected wavelength channel signal of the WDM signal through optical circulators to provide low crosstalk between the dropped and added wavelength signals. The switch also reduces the number of WDM MUX-DEMUX required to one half that compared to a traditional approach. Furthermore, the switch can be designed to be wavelength cyclic with individual free spectral ranges that can be independently set to either through or add/drop states.
    Type: Application
    Filed: December 27, 2001
    Publication date: September 19, 2002
    Applicant: AT&T Corporation
    Inventors: Mark D. Feuer, Nicholas J. Frigo, Cedric F. Lam
  • Publication number: 20020131117
    Abstract: A method and a system in which selected wavelengths of a wavelength division multiplexed (WDM) signal are modulated with multicast data for multicasting data services on an optical network. The WDM signal is received from a hub node of the optical network, such as a unidirectional ring network or a bidirectional ring network. A four-port wavelength crossbar switch (4WCS) selectably switches selected wavelengths from the optical network to a modulator loop. The modulator loop includes a multicast modulator that modulates the selected plurality of wavelengths with the multicast data. Each modulated wavelength is then switched back to the optical network by the 4WCS switch, and sent to a plurality of subscriber nodes of the optical network. This architecture allows a facility provider to be physically separated from a content provider, and affords the flexibility of selectively delivering multicast content to individual subscribers.
    Type: Application
    Filed: December 27, 2001
    Publication date: September 19, 2002
    Applicant: AT&T Corporation
    Inventors: Mark D. Feuer, Nicholas J. Frigo, Cedric F. Lam
  • Publication number: 20020093710
    Abstract: A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands.
    Type: Application
    Filed: July 30, 2001
    Publication date: July 18, 2002
    Inventors: Martin Birk, Patrick P. Iannone, Kenneth C. Reichmann, Nicholas J. Frigo, Cedric F. Lam