Motorola Corporation

Arris Enterprises LLC

Motorola Mobility LLC

General Instrument Corporation

Freescale Semiconductor,inc.

General Instrument Corporation of Delaware

Jun J Wang

Ravindranath Droopad

Zhiyi Jimmy Yu

Jerald A Hallmark

Jamal Ramdani

William J Ooms

Kerry I Litvin

Jonathan K Abrokwah

Daniel S Marshall

Corey D Overgaard

Jay A Curless

Kerry Litvin

Marcel F Schemmann

Matthias Passlack

Timothy J Wilson

Venkatesh Gururaj Mutalik

Yi Wei

Kurt W Eisenbeiser

Samir S Vaidya

Yong Liang

Alexander A Demkov

Shamsuddin H Chasmawala

David R Maas

Richard A Meier

Xiaoming Hu

Prachi P Kumar

Chen Mu

Zhiyi Yi

Kalvyn T Rasquinha

Nghia T Vuong

Systems and methods for providing dispersion compensation to optical systems. In some embodiments, the disclosed dispersion compensation system may be capable of adjusting the amount of dispersion compensation. The disclosed dispersion compensation system may include a cascade of varactor circuit elements, each with separate bias control, and optionally may include one or more switches to enable or disable selective ones of the cascaded varactor circuit elements.

Dispersion compensation circuit with cascaded varactor circuit elements

Techniques for transmitting an optical signal through optical fiber with an improved cost effective stimulated Brillouin scattering (SBS) suppression include externally modulating a light beam emitted from a light source with a high frequency signal. The light beam is also modulated externally with an RF information-carrying signal. The high frequency signals are at least twice a highest frequency of the RF signal. The high frequency signals modulating the light source can be gain and phase adjusted by the first set of gain and phase control circuit to achieve a targeted spectrum shape. The adjusted high frequency signals then are split, providing a portion of the split signals to modulate the light source and another portion of the split signals to the second set of phase and gain control circuit for adjusting a phase/gain. The output of second set of phase and gain control circuits can be applied to the external modulator to eliminate intensity modulation caused by the corresponding high frequency signals that modulate the light source. The spread spectrum for SBS suppression or the optical transmitter's SNR is further improved by cancelling a beat between SBS suppression modulation tones and out of band distortion spectrum of information bearing RF signal.

Stimulated Brillouin Scattering (SBS) suppression in an optical communications system

In one embodiment, an electro-absorption modulator receives an optical light from an optical light source and outputs a modulated optical signal. The electro-absorption modulator includes a bias voltage used to set a predetermined modulation performance and an output power of the electro-absorption modulator. A controller measures a photocurrent generated by the electro-absorption modulator and uses the photocurrent as a reference to automatically control the bias voltage of the electro-absorption modulator to maintain the predetermined modulation performance and the output power of the electro-absorption modulator when a detuning change occurs between the electro-absorption modulator and the optical light source throughout the lifetime of transmitters based on an EML device.

Automatic bias control of an optical transmitter

In one embodiment, an electro-absorption modulator is configured to receive an optical light from an optical light source and outputs a modulated optical signal. The electro-absorption modulator includes a bias voltage that is used to set optimum predetermined modulation performance and an output power of the electro-absorption modulator. A controller is configured to measure a bias current of the optical light source and use a change of the bias current to determine a detuning change that occurs between the electro-absorption modulator and the optical light source. The controller uses the detuning change to automatically control the bias voltage of the electro-absorption modulator to maintain the predetermined modulation performance and maintain the output power of the electro-absorption modulator.

Performance prediction and maintenance of an optical transmitter

Stimulated brillouin scattering (SBS) suppression in an optical communications system

Stimulated Brillouin scattering (SBS) suppression in an optical communications system

Techniques for transmitting an optical signal through optical fiber with an improved stimulated Brillouin scattering (SBS) suppression and an improved transmitter's signal to noise ratio (SNR) include externally modulating a light beam emitted from a light source with a high frequency signal. The light beam is also modulated externally with an RF information-carrying signal. The high frequency signal is at least twice a highest frequency of the RF signal. The high frequency signal modulating the light source can be split, providing a portion of the split signal to a phase and gain control circuit for adjusting a phase/gain. The output of phase and gain control circuit can be applied to the external modulator to eliminate intensity modulation for SBS suppression improvement. The optical transmitter's SNR is further improved by cancelling a beat between SBS suppression modulation tone and out of band distortion spectrum of information bearing RF signal.

Systems and methods for using a dispersion compensation circuit to directly modulate a laser. Techniques include calibrating a varactor bias point in a dispersion compensation circuit during manufacturing, but positioning the dispersion compensation circuit between a first attenuator and a second attenuator. Each attenuator, capable of reducing power of an input signal, may be adjustable so that the attenuation provided by each attenuator may be adjusted. The ratio of attenuation between attenuators may be adjusted based on either chirp of a laser or fiber length, and a varactor bias point may be adjusted by the other one of the chirp of the laser or fiber length. Thus, both chirp and fiber length may serve as a basis for adjusting attenuation between attenuators having a dispersion compensation circuit positioned between them.

Directly modulated laser with dispersion compensation

A dispersion correction circuit is provided for use with an input driving signal. The dispersion correction circuit includes an input portion an output portion and a filter portion. The input portion is arranged to receive the input driving signal. The output portion can output an output signal based on the input driving signal. The filter portion is disposed between the input portion and the output portion. The filter portion includes a first varactor, a DC bias portion, and a second varactor. The DC bias portion provides a DC bias to the first varactor. The first varactor is arranged in a first polarity direction, and the second varactor is arranged in a second polarity direction that is the same as the first direction.

Electronic dispersion correction circuit for optical transmission system

A dispersion correction circuit is provided for use with an input driving signal. The dispersion correction circuit includes an input portion, an output portion and a filter portion. The input portion is arranged to receive the input driving signal. The output portion can output an output signal based on the input driving signal. The filter portion is disposed between the input portion and the output portion. The filter portion includes a varactor, a DC bias portion, and a transformer. The DC bias portion provides a DC bias to the varactor.

A communication system performs adaptive scheduling by considering present and past reported CQI values and other indications of channel conditions in scheduling a Modulation and Coding Scheme (MCS) and then executing a 'dithering' function in order to effectuate an MCS that is intermediate between adjacent discrete MCSs. In one embodiment, the communication system determines a first MCS based on a channel quality metric received from a mobile station (MS) and then transmits data utilizing the first MCS. The communication system assigns weights to each of the first MCS and a second MCS based on whether the transmitted data is acknowledged and, based on the assigned weights, selects one of the first and second MCSs for a subsequent transmission of data to the MS. The communication system also may assign weights to each of a first and second MCS based on a transition between a MIMO-A and a MIMO-B transmission scheme.

Method and apparatus for scheduling downlink transmissions in an orthogonal frequency division multiplexing communication system

A device is provided for use with a dither tone signal and an information signal. The device includes a laser diode, an electro-optic modulator, a first filter and a second filter. The laser diode can output a first light signal, whereas the electro-optic modulator can transmit a second light signal. The first filter can generate a first filtered signal based on the information signal. The second filter can generate a second filtered signal based on the dither tone signal. The first light signal is based on the dither tone signal, the information signal and the first filtered signal. The second light signal is based on the first light signal, the information signal, the dither tone signal and the second filtered signal. The filtered signals reduce or cancel the undesired leaked/interfering signals.

System and method for reducing mutual leakage between distributed feedback laser and electro-absorption modulator in integrated electro-absorption modulated laser

Methods of transmitting an optical signal through optical fiber in a manner suppressing stimulated Brillouin scattering (SBS) are provided. A light beam emitted from a light source is modulated by driving either the light source or a separate phase modulator or both simultaneously with a separate high frequency signal dithered by one or more low frequency dithering signals of a frequency or frequencies lower than that of the high frequency signal. Thereafter, the light beam is further modulated externally with an RF information-carrying signal. The high frequency signal is at least twice a highest frequency of the RF information-carrying signal. The light beam modulated with the RF information-carrying signal is coupled into optical fiber. The high frequency signal dithered by the one or more low frequency dithering signals spreads the optical power of the light beam in a wider spectral range thereby raising the SBS threshold power level for purposes of suppressing SBS while the undesired induced spurious frequency component level is controlled. The form of the spread spectrum is also controlled and adjusted. An optical transmitter is also disclosed.

Method and apparatus for improved SBS suppression in optical fiber communication systems

A method and system for managing a communication between a base station () and plurality of subscriber stations (and) is disclosed. The method includes determining () whether a Round Trip Delay (RTD) component is greater than the duration of a data slot for at least one subscriber station of the plurality of subscriber stations. The RTD component is a part of a Transmit/receive Transition Gap (TTG) of the base station. The method also includes scheduling () the data slot for the at least one subscriber station using the RTD component of the base station when the duration of the RTD component is greater than the duration of the data slot for the at least one subscriber station.

Method and system for managing communication between a base station and subscriber stations

An improved method and apparatus is provided for transmitting a WDM optical signal. The method begins by modulating optical channels that are each located at a different wavelength from one another with (1) a respective one of a plurality of information-bearing electrical signals that all embody the same broadcast information; (2) a respective one of a plurality of RF signals having a common functional broadcast waveform, at least one of the RF signals being out of phase with respect to remaining ones of the plurality of RF signal and (3) at least one of the RF signals being phase adjusted with respect to its original phase. Each of the modulated optical channels is multiplexed to form a WDM optical signal. The WDM optical signal, while maintaining the pre-assigned phase relationships between the modulation signals of the optical channels, is forwarded onto an optical transmission path.

Method and apparatus for transmitting multiple channels in a wavelength division multiplexed (WDM) optical communication system with reduced raman crosstalk and nonlinear distortions

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Horsham, PA, United States of America

Jun J Wang