Patents by Inventor Radhakrishnan L. Nagarajan

Radhakrishnan L. Nagarajan 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).

  • Patent number: 10116391
    Abstract: The present invention relates to telecommunication techniques and integrated circuit (IC) devices. More specifically, embodiments of the present invention provide an off-quadrature modulation system. Once an off-quadrature modulation position is determined, a ratio between DC power transfer amplitude and dither tone amplitude for a modulator is as a control loop target to stabilize off-quadrature modulation. DC power transfer amplitude is obtained by measuring and sampling the output of an optical modulator. Dither tone amplitude is obtained by measuring and sampling the modulator output and performing calculation using the optical modulator output values and corresponding dither tone values. There are other embodiments as well.
    Type: Grant
    Filed: November 2, 2017
    Date of Patent: October 30, 2018
    Assignee: INPHI CORPORATION
    Inventors: Todd Rope, Radhakrishnan L. Nagarajan, Hari Shankar
  • Patent number: 10107961
    Abstract: An silicon photonics device of hybrid waveguides having a coupling interlayer with an accurately controlled thickness and a method of making the same. The device includes a first plurality of Si waveguides formed in a SOI substrate and a first layer of SiO2 overlying the first plurality of Si waveguides and a second plurality of Si3N4 waveguides formed on the first layer of SiO2. At least one Si3N4 waveguide is disposed partially overlapping with at least one of the first plurality Si waveguides in vertical direction separated by the first layer of SiO2 with a thickness controlled no greater than 90 nm. The device includes a second layer of SiO2 overlying the second plurality of Si3N4 waveguides. The method of accurately controlling the coupling interlayer SiO2 thickness includes a multilayer SiO2/Si3N4/SiO2 hard mask process for SiO2 etching and polishing as stopping and buffering layer as well as Si waveguide etching mask.
    Type: Grant
    Filed: December 27, 2017
    Date of Patent: October 23, 2018
    Assignee: INPHI CORPORATION
    Inventors: Liang Ding, Radhakrishnan L. Nagarajan
  • Publication number: 20180299629
    Abstract: A photonic transceiver apparatus in QSFP package. The apparatus includes a case having a base member, two partial side members, and a lid member to provide a spatial volume with an opening at a back end of the base member. Additionally, the apparatus includes a PCB, installed inside the spatial volume over the base member having a pluggable electrical connector at the back end. Further, the apparatus includes multiple optical transmitting devices in mini-transmit-optical-sub-assembly package, each being mounted on a common support structure and having a laser output port in reversed orientation toward the back end. Furthermore, the apparatus includes a silicon photonics chip, including a fiber-to-silicon attachment module, mounted on the PCB and coupled to a modulation driver module and a trans-impedance amplifier module. Moreover, the apparatus includes a pair of optical input/output ports being back connected to the fiber-to-silicon attachment module.
    Type: Application
    Filed: June 20, 2018
    Publication date: October 18, 2018
    Inventors: Radhakrishnan L. NAGARAJAN, Peng-Chih LI, Masaki KATO
  • Publication number: 20180299620
    Abstract: An apparatus of polarization self-compensated delay line interferometer. The apparatus includes a first waveguide arm of a first material of a first length disposed between an input coupler and an output coupler and a second waveguide arm of the first material of a second length different from the first length disposed between the same input coupler and the same output coupler. The apparatus produces an interference spectrum with multiple periodic passband peaks where certain TE (transverse electric) and TM (transverse magnetic) polarization mode passpand peaks are lined up. The apparatus further includes a section of waveguide of a birefringence material of a third length added to the second waveguide arm to induce a phase shift of the lined-up TE/TM passband peaks to a designated grid as corresponding polarization compensated channels of a wide optical band.
    Type: Application
    Filed: June 22, 2018
    Publication date: October 18, 2018
    Inventors: Masaki KATO, Radhakrishnan L. NAGARAJAN
  • Publication number: 20180294884
    Abstract: A Pulse Amplitude Modulated (PAM) optical device utilizing multiple wavelengths, features a communications interface having enhanced diagnostics capability. New registers are created to house additional diagnostic information, such as error rates. The diagnostic information may be stored in raw form, or as processed on-chip utilizing local resources.
    Type: Application
    Filed: May 25, 2018
    Publication date: October 11, 2018
    Inventors: Todd ROPE, Radhakrishnan L. NAGARAJAN, Jamal RIANI, Pulkit KHANDELWAL
  • Publication number: 20180275359
    Abstract: An optical transceiver by hybrid multichip integration. The optical transceiver includes a PCB with a plurality of prefabricated surface bonding sites. A first chip includes a FOWLP package of multiple electronics devices embedded in a dielectric molding layer overlying a dielectric redistribution layer is disposed on the PCB by respectively bonding a plurality of conductor balls between the dielectric redistribution layer and the plurality of prefabricated surface bonding sites while exposing soldering material filled in multiple through-mold vias (TMVs) in the dielectric molding layer. The optical transceiver further includes a second chip configured as a Sipho die comprising photonics devices embedded in a SOI wafer substantially free from any electronics device process. The second chip is stacked over the first chip with multiple conductor bumps being bonded respectively to the soldering material in the multiple TMVs.
    Type: Application
    Filed: May 21, 2018
    Publication date: September 27, 2018
    Inventors: Liang DING, Radhakrishnan L. NAGARAJAN, Roberto COCCIOLI
  • Publication number: 20180262273
    Abstract: A single chip dual-channel driver for two independent traveling wave modulators. The driver includes two differential pairs inputs per channel respectively configured to receive two digital differential pair signals. The driver further includes a two-bit DAC per channel coupled to the two differential pairs inputs to produce a single analog differential pair PAM signal at a differential pair output for driving a traveling wave modulator. Additionally, the driver includes a control block having internal voltage/current signal generators respective coupled to each input and the 2-bit DAC for providing a bias voltage, a tail current, a dither signal to assist modulation control per channel. Furthermore, the driver includes an internal I2C communication block coupled to a high-speed clock generator to generate control signals to the control block and coupled to host via an I2C digital communication interface.
    Type: Application
    Filed: May 10, 2018
    Publication date: September 13, 2018
    Inventors: Radhakrishnan L. NAGARAJAN, Todd ROPE
  • Publication number: 20180262268
    Abstract: In an example, the present invention includes an integrated system-on-chip device. The device is configured on a single silicon substrate member. The device has a data input/output interface provided on the substrate member. The device has an input/output block provided on the substrate member and coupled to the data input/output interface. The device has a signal processing block provided on the substrate member and coupled to the input/output block. The device has a driver module provided on the substrate member and coupled to the signal processing block. In an example, the device has a driver interface provided on the substrate member and coupled to the driver module and configured to be coupled to a silicon photonics device. In an example, a control block is configured to receive and send instruction(s) in a digital format to the communication block and is configured to receive and send signals in an analog format to communicate with the silicon photonics device.
    Type: Application
    Filed: May 9, 2018
    Publication date: September 13, 2018
    Inventor: Radhakrishnan L. NAGARAJAN
  • Patent number: 10055375
    Abstract: The present invention provides an integrated system-on-chip device. The device is configured on a single silicon substrate member. The device has a data input/output interface provided on the substrate member. The device has an input/output block provided on the substrate member and coupled to the data input/output interface. The device has a signal processing block provided on the substrate member and coupled to the input/output block. The device has a driver module provided on the substrate member and coupled to the signal processing block. The device further includes a driver interface and coupled to the driver module and configured to be coupled to a silicon photonics device. In an example, a control block is configured to receive and send instruction(s) in a digital format to the communication block and is configured to receive and send signals in an analog format to communicate with the silicon photonics device.
    Type: Grant
    Filed: October 11, 2017
    Date of Patent: August 21, 2018
    Assignee: INPHI CORPORATION
    Inventors: Siddharth Sheth, Radhakrishnan L. Nagarajan
  • Patent number: 10056733
    Abstract: A wavelength locker integrated with a silicon photonics transmission system comprising a silicon-on-insulator (SOI) substrate and an input via a power tap coupler to receive a fraction of a transmission signal with one or more frequencies from a primary output path of the silicon photonics transmission system. The wavelength locker further includes a splitter configured to split the input to a first signal in a first path and a second signal in a second path and a first delay-line-interferometer (DLI) coupled to the second path to receive the second signal and configured to generate an interference spectrum and output at least two sub-spectrums tunable to keep quadrature points of the sub-spectrums at respective one or more target frequencies. The wavelength locker is configured to generate an error signal fed back to the silicon photonics transmission system for locking the one or more frequencies at the one or more target frequencies.
    Type: Grant
    Filed: March 8, 2017
    Date of Patent: August 21, 2018
    Assignee: INPHI CORPORATION
    Inventors: Brian Taylor, Radhakrishnan L. Nagarajan, Masaki Kato
  • Patent number: 10050736
    Abstract: An integrated apparatus with optical/electrical interfaces and protocol converter on a single silicon substrate. The apparatus includes an optical module comprising one or more modulators respectively coupled with one or more laser devices for producing a first optical signal to an optical interface and one or more photodetectors for detecting a second optical signal from the optical interface to generate a current signal. Additionally, the apparatus includes a transmit lane module coupled between the optical module and an electrical interface to receive a first electric signal from the electrical interface and provide a framing protocol for driving the one or more modulators. Furthermore, the apparatus includes a receive lane module coupled between the optical module and the electrical interface to process the current signal to send a second electric signal to the electrical interface.
    Type: Grant
    Filed: September 1, 2017
    Date of Patent: August 14, 2018
    Assignee: INPHI CORPORATION
    Inventor: Radhakrishnan L. Nagarajan
  • Publication number: 20180217334
    Abstract: An apparatus for converting fiber mode to waveguide mode. The apparatus includes a silicon substrate member and a dielectric member having an elongated body. Part of the elongated body from a back end overlies the silicon substrate member and remaining part of the elongated body up to a front end is separated from the silicon substrate member by a second dielectric material at an under region. The apparatus also includes a waveguide including a segment from the back end to a tail end formed on the dielectric member at least partially overlying the remaining part of the elongated body. The segment is buried in a cladding overlying entirely the dielectric member. The cladding has a refractive index that is less than the waveguide but includes an index-graded section with decreasing index that is formed at least over the segment from the tail end toward the back end.
    Type: Application
    Filed: March 22, 2018
    Publication date: August 2, 2018
    Inventors: Masaki KATO, Radhakrishnan L. NAGARAJAN
  • Patent number: 10036904
    Abstract: An integrated differential Electro-Absorption Modulator (EAM) device. The device includes a substrate, an electrical driver, and two EAM modules. The electrical driver circuit is configured overlying the substrate member and has one output electrically coupled to the first EAM module and the other output electrically coupled to the second EAM module. The first and second EAM modules have a first and a second output, respectively. A beam splitter can be configured to split an optical input into two optical outputs, each of which can be optically coupled to the optical inputs of the first and second EAM modules.
    Type: Grant
    Filed: March 26, 2014
    Date of Patent: July 31, 2018
    Assignee: INPHI CORPORATION
    Inventor: Radhakrishnan L. Nagarajan
  • Publication number: 20180212712
    Abstract: The present invention is directed to communication systems and methods. According to an embodiment, a receiving optical transceiver determines signal quality for signals received from a transmitting optical transceiver. Information related to the signal quality is embedded into back-channel data and sent to the transmitting optical transceiver. The transmitting optical transceiver detects the presence of the back-channel data and adjusts one or more of its operating parameters based on the back-channel data. There are other embodiments as well.
    Type: Application
    Filed: January 20, 2017
    Publication date: July 26, 2018
    Inventors: Todd ROPE, Radhakrishnan L. NAGARAJAN
  • Patent number: 10031289
    Abstract: An apparatus of polarization self-compensated delay line interferometer. The apparatus includes a first waveguide arm of a first material of a first length disposed between an input coupler and an output coupler and a second waveguide arm of the first material of a second length different from the first length disposed between the same input coupler and the same output coupler. The apparatus produces an interference spectrum with multiple periodic passband peaks where certain TE (transverse electric) and TM (transverse magnetic) polarization mode passband peaks are lined up. The apparatus further includes a section of waveguide of a birefringence material of a third length added to the second waveguide arm to induce a phase shift of the lined-up TE/TM passband peaks to a designated grid as corresponding polarization compensated channels of a wide optical band.
    Type: Grant
    Filed: April 1, 2016
    Date of Patent: July 24, 2018
    Assignee: INPHI CORPORATION
    Inventors: Masaki Kato, Radhakrishnan L. Nagarajan
  • Patent number: 10025046
    Abstract: A photonic transceiver apparatus in QSFP package. The apparatus includes a case having a base member, two partial side members, and a lid member to provide a spatial volume with an opening at a back end of the base member. Additionally, the apparatus includes a PCB, installed inside the spatial volume over the base member having a pluggable electrical connector at the back end. Further, the apparatus includes multiple optical transmitting devices in mini-transmit-optical-sub-assembly package, each being mounted on a common support structure and having a laser output port in reversed orientation toward the back end. Furthermore, the apparatus includes a silicon photonics chip, including a fiber-to-silicon attachment module, mounted on the PCB and coupled to a modulation driver module and a trans-impedance amplifier module. Moreover, the apparatus includes a pair of optical input/output ports being back connected to the fiber-to-silicon attachment module.
    Type: Grant
    Filed: August 9, 2017
    Date of Patent: July 17, 2018
    Assignee: INPHI CORPORATION
    Inventors: Radhakrishnan L. Nagarajan, Peng-Chih Li, Masaki Kato
  • Publication number: 20180191430
    Abstract: In an example, the present invention includes an integrated system-on-chip device. The device is configured on a single silicon substrate member. The device has a data input/output interface provided on the substrate member. The device has an input/output block provided on the substrate member and coupled to the data input/output interface. The device has a signal processing block provided on the substrate member and coupled to the input/output block. The device has a driver module provided on the substrate member and coupled to the signal processing block. In an example, the device has a driver interface provided on the substrate member and coupled to the driver module and configured to be coupled to a silicon photonics device. In an example, a control block is configured to receive and send instruction(s) in a digital format to the communication block and is configured to receive and send signals in an analog format to communicate with the silicon photonics device.
    Type: Application
    Filed: February 23, 2018
    Publication date: July 5, 2018
    Inventor: Radhakrishnan L. NAGARAJAN
  • Patent number: 10014950
    Abstract: A PAM4 driver with at least 56 Gbps speed for driving a Mach-Zehnder modulator. The PAM4 driver is configured as 2-bit CMOS digital-to-analog convertor including a drive control module for receiving a pair of incoming differential digital data and generating a first processed reference signal and a second processed reference signal. The PAM4 driver further includes a mirrored buffer circuit to produce two sets of four voltage levels. Furthermore, the PAM4 driver includes a decoder module controlled by a switch bias control module configured to decode each of the two sets of four voltage levels for generating a first output signal and a complementary second out signal with 4 independently adjustable analog levels for driving the Mach-Zehnder modulator with close ended termination resistor.
    Type: Grant
    Filed: July 11, 2017
    Date of Patent: July 3, 2018
    Assignee: INPHI CORPORATION
    Inventor: Radhakrishnan L. Nagarajan
  • Patent number: 10012797
    Abstract: A semiconductor monolithic transmitter photonic integrated circuit (TxPIC) comprises two different situations, either at least one signal channel in the PIC having a modulated source with the channel also extended to include at least one additional element or a plurality of modulated sources comprising N signal channels in the PIC of different transmission wavelengths, where N is equal to or greater than two (2), which may also approximate emission wavelengths along a standardized wavelength grid. In these two different situations, a common active region for such modulated sources and additional channel elements is identified as an extended identical active layer (EIAL), as it extends from a single modulated source to such additional channel elements in the same channel and/or extends to additional modulated sources in separate channels where the number of such channels is N equal to two or greater.
    Type: Grant
    Filed: January 27, 2005
    Date of Patent: July 3, 2018
    Assignee: Infinera Corporation
    Inventors: Radhakrishnan L. Nagarajan, Fred A. Kish, Jr., Masaki Kato, Charles H. Joyner, David F. Welch, Randal A. Salvatore, Richard P. Schneider, Mehrdad Ziari, Damien Jean Henri Lambert, Sheila K. Hurtt, Andrew G. Dentai, Atul Mathur, Vincent G. Dominic
  • Patent number: 10014936
    Abstract: In an example, the present invention includes an integrated system-on-chip device. The device is configured on a single silicon substrate member. The device has a data input/output interface provided on the substrate member. The device has an input/output block provided on the substrate member and coupled to the data input/output interface. The device has a signal processing block provided on the substrate member and coupled to the input/output block. The device has a driver module provided on the substrate member and coupled to the signal processing block. In an example, the device has a driver interface provided on the substrate member and coupled to the driver module and configured to be coupled to a silicon photonics device. In an example, a control block is configured to receive and send instruction(s) in a digital format to the communication block and is configured to receive and send signals in an analog format to communicate with the silicon photonics device.
    Type: Grant
    Filed: February 23, 2018
    Date of Patent: July 3, 2018
    Assignee: INPHI CORPORATION
    Inventor: Radhakrishnan L. Nagarajan