Nortel Networks Corporation

Cisco Technology, Inc.

Other

Ciena Corporation

Stc, Inc

James E Whiteaway

George H Thompson

Terry Bricheno

Theodor Kupfer

Alan Fielding

Thomas Duthel

Stephen Day

Soeren Gehrke

Seb J Savory

Kim Bryon Roberts

Han Henry Sun

Leo L Strawczynski

Maurice M O'Sullivan

Richard E Epworth

Nebojsa Stojanovic

Terry Victor Clapp

Christopher R Fludger

Adrien Comeau

Jonas Geyer

Bram Peeters

Andrew J Collar

Jürgen Hauenschild

George H B Thompson

Princy Johnson

Dave Walker

Soren Gehrke

Sören Gehrke

A system configured to maintain a consistent local-oscillator-power-to-primary-signal-power ratio (LO/SIG ratio). The system may be configured to: receive the voltages for a plurality of optical signal components split from a combined SIG and LO signal; determine individual factors for the plurality of optical signal components; average the individual factors; determine whether the averaged output is less than an existing minimum reference value for a variable optical attenuator; determine whether the averaged output is greater than an existing maximum reference value for the variable optical attenuator; change the existing minimum reference value to a new value associated with the averaged output, due to determining that the averaged output is less than the existing minimum reference value; change the existing maximum reference value to a new value associated with the averaged output, due to determining that the averaged output is greater than the existing maximum reference value; and change a new value associated with the averaged output to be transmitted to the variable optical attenuator.

Optical communication reception system

According to a first aspect, techniques are provided to optimize a Mach-Zehnder modulator drive waveform by distorting the outer modulation levels of the waveform, thereby equalizing eye openings of the received optical field, and in particular creating a wider and more defined central eye opening of the received optical field. According to a second aspect, techniques are provided to adjust in-phase (I) modulation levels based on the imperfect performance of a Mach-Zehnder modulator allocated to modulate quadrature-phase (Q) modulation levels, and conversely to adjust the Q modulation levels based on the imperfect performance of an MZ modulator allocated to modulate I modulation levels.

Pre-distortion techniques for optical modulators to improve constellation point separation

A system configured to maintain a consistent local-oscillator-power-to-primary-signal-power ratio (LO/SIG ratio). The system may be configured to: receive the voltages for a plurality of optical signal components split from a combined SIG and LO signal; determine individual factors for the plurality of optical signal components; average the individual factors; determine whether the averaged output is less than a minimum reference value for a variable optical attenuator; determine whether the averaged output is greater than a maximum reference value for the variable optical attenuator; change a value associated with the averaged output to the minimum reference value, due to determining that the averaged output is less than the minimum reference value; change a value associated with the averaged output to the maximum reference value, due to determining that the averaged output is greater than the maximum reference value; and change a new value associated with the averaged output to be transmitted to the variable optical attenuator.

Techniques and configurations are provided to generate multiple coherent optical subcarriers. A laser source generates as output a light beam at a carrier frequency. A multicarrier generator is provided that is coupled to the laser source and comprises one or more dual carrier generators each configured to modulate the light beam at the same modulation frequency or different modulation frequencies so as to output a plurality of light beams each at a different subcarrier frequency that is offset from the carrier frequency. The multicarrier generator generates the plurality of light beams on individual outputs, e.g., fibers, without the need for an optical demultiplexing filter.

Filter-less generation of coherent optical subcarriers

Phase detection techniques in which an input signal is sampled to obtain several samples at different points in time with respect to a clock, said different points in time comprising an earliest point and latest point. The detection techniques further include generating a phase control signal obtained from the several samples of the input signal.

Phase detection method and phase detector

An optical communications system comprises a transmitter, a receiver and an optical communications link between the transmitter and receiver. The transmitter comprises a current-driven directly modulated laser for providing a modulated optical signal and a current controller for controlling the current waveform applied to the laser. The current waveform applied to the laser is determined to compensate for the effects of the laser non-linearities and the fiber chromatic dispersion. This system applies pre-compensation to the directly modulated laser input current waveform to provide both pre-compensation for chromatic dispersion and compensation for the non-linearities of the directly modulated laser. These are two of the main limiting factors in providing a low cost high data rate and long reach optical communications system.

Optical laser control for optical communications systems

A method of synthesizing a modulated optical signal using a laser cascaded with an amplitude modulator. A phase drive signal V(t) is derived for driving the laser to generate an optical carrier signal with a desired phase &#x3c6;(t). An amplitude drive signal V(t) is then derived for driving the amplitude modulator to impose a desired amplitude S(t) onto the optical carrier signal generated by the laser. The amplitude drive signal V(t) is compensated for amplitude modulation of the optical carrier signal generated by the laser.

Optical E-field modulation using a directly driven laser

A receiver for an optical transmission system, has a polarization diverse and phase diverse coherent optical receiver, and a digital adaptive equalizer for compensating for distortions in the optical signal introduced by the optical path. The entire field of the optical signal is mapped including phase and polarization information, to enable more complete compensation for impairments such as chromatic dispersion and PMD. Furthermore, it can also reduce the problems which have so far held back coherent optical detection from widespread implementation, such as polarization alignment and phase tracking. This can be applied to upgrade existing installed transmission routes to increase capacity without the expense of replacing the old fiber.

Digital compensation for optical transmission system

The invention is directed to an improved wavelength selective optical filter component having an optical path therethrough and comprising a first and a second optical port, a multimode interference region and a wavelength selective element. The first optical port and the multimode interference region each have an axis of symmetry relative to the optical path. The optical path enables light to travel through the multimode interference region and the wavelength selective element from the first or second optical port to the other optical port, and wherein the axis of symmetry of the multimode interference region is not aligned with the axis of symmetry of the first optical port. An advantage of arranging the multimode interference region and first optical port such that their axes of symmetry are not aligned is that this introduces a slope in the pass band of the device which can be chosen at the design stage to meet a specific slope requirement or can be used to cancel a pre-existing slope to give a resultant flat pass band.

Wavelength selective optical filter

A reconfigurable optical add drop module has a coarse demultiplexer, for outputting sub bands of wavelengths, a fine mux/demux, for adding and/or dropping wavelengths, a coarse multiplexer, for remultiplexing the sub bands, an optical switch in between the coarse demultiplexer and the fine mux/demux, to switch the sub bands for pass through, or for add/drop. Reconfiguration can be remote, automatic, with less interruption to traffic. By switching sub bands rather than individual wavelengths, the number of switches can be reduced, and consequently losses, and space requirements can be reduced. Also, upgrading from pass through to add drop, of one or more sub bands is easier. Hence initial capital cost of nodes and the cost of upgrading can be reduced, since there is less need to provide redundant add drop capacity initially. Mid stage access enables external components to be added to the optical path for the sub bands.

Reconfigurable WDM mux/demux/OADM

An optical couplercomprising at least three fibresand, portions of the fibres being fused to each other to form a coupling regionoperable to couple light therebetween. At least two of the fibres have inputsand/orand/orand at least two of the fibres have outputsand/orand/or. In use, on illumination of at least two of the inputs light intensity is emitted from a plurality of the outputs having a substantially asymmetric phase relationship, such as, for example, a quadrature phase relationship between two of the outputs. The invention also provides for methods of making such a device.

3 Fibre I and Q coupler

An optical demultiplexer has a coarse filter and a plurality of arrayed waveguide gratings (AWGs) connected to respective outputs of the coarse filter . The AWGs are of like design with a plurality of configurations and are arranged to have a configuration corresponding to be frequency range output on the respective output. The device can be used in WDM systems.

Optical demultiplexing system and method

A planar dispersion compensator for an optical signal is provided. The compensator decomposes an inputted optical signal into N component signals separated by a fractional wavelength &dgr;&lgr;. Each component signal has its path-length adjusted to induce a sufficient phase shift between input and output to change the group delay of the optical signal when recombined from each of the component signals. In this manner, pulse broadening can be compensated by selectively varying the induced phase shifts to produce the desired level of opposite group delay. Portions of the substrate of the planar waveguide are removed to improve thermal responsiveness of the path-length adjustment means.

Planar waveguide dispersion compensator

A planar dispersion compensator for an optical signal is provided. The compensator decomposes an inputted optical signal into N component signals separated by a fractional wavelength &dgr;&lgr;. Each component signal has its path-length adjusted to induce a sufficient phase shift between input and output to change the group delay of the optical signal when recombined from each of the component signals. In this manner, pulse broadening can be compensated by selectively varying the induced phase shifts to produce the desired level of opposite group delay.

Growing community of inventors

Sawbridgeworth, United Kingdom

James E Whiteaway