Lucent Technologies Inc.

Other

Alcatel-lucent USA Inc.

University of Minnesota

Noble Devices Technologies

Christi Kay Madsen

Gadi Lenz

Ronald Edward Scotti

Douglas Max Gill

Joseph Shmulovich

Charles H Henry

Edward J Laskowski

Julian Bernard Soole

Rebecca Jordan

John A Rogers

Keith Wayne Goossen

James Albert Walker

Herman M Presby

Edwin Arthur Chandross

Thomas Andrew Strasser

Joseph Earl Ford

Mahmoud Rasras

Conor S Rafferty

Yuan P Li

Arturo Hale

Valerie Jeanne Kuck

Jane Deborah LeGrange

Rudolf Feodor Kazarinov

Bharat Raj Acharya

Annjoe Golangco Wong-Foy

Cheng Cher Huang

Albert Georg Peter Oswald

Albin Lloyd Kasper

An optical device for changing polarization comprises a waveguide having a waveguide end facet coupled to a quarter-wave plate/reflector combination to rotate the polarization of incident light to the waveguide by 90 degrees. In one embodiment, a polarization beam splitter/rotator combination (PBSR) uses a quarter-wave plate in reflection at the end facet of the waveguide. The polarization beam splitter/rotator combination and variations of that structure are applied in various useful topologies as polarization mode dispersion (PMD) compensators and polarimeters.

Integrated polarization beam splitter with quarter-wave plate for polarimeter and PMD compensation applications

It is possible to perform reset free operation in devices having polarization state controllers by employing specific sequences of phase shifters and couplers. In particular, sequences comprising a coupler/phase shifter/coupler or phase shifter/coupler/phase shifter formed in, for example, a semiconductor substrate, e.g. silicon substrate, is used to form the polarization state controller. For example, a sequence functions as a quarter wave plate equivalent while two combined sequences function as a half wave plate. Moreover, sequences functioning as wave plates more general than quarter wave plates are advantageously employed. Control of the couplers and phase shifters of these sequences yield reset free or reset free, fully deterministic operation.

Reset free devices

In accordance with the invention, an optical data transmission system of enhanced flexibility is provided by sub-band multiplexing of a WDM channel. Specifically, an exemplary optical data transmission system comprises an optical source for generating a plurality of frequency spaced optical tones within at least one WDM channel, a plurality of modulators for modulating the tones, and an optical transmission fiber for receiving and transmitting the modulated tones. An advantage of this system is that the tones are coherent. As a consequence, the need for guard bands is substantially reduced, and more flexible coding systems can be used to achieve a higher level of integration. For example, both amplitude and phase coding can be applied to the sub-band signals.

Optical data transmission system using sub-band multiplexing

A semiconductor waveguide includes a section containing free charge, either electrons or holes, which can be steered into or removed from the path of the beam under the control of electrical signals. The mobile charges come from a potential well which may be either filled or depleted under electrical control. When the well is filled, the charges speed the beam propagation, introducing a phase change. When the well is emptied the beam propagates with extra delay. The phase shifter allows very high speed modulation of the beam using low voltage and low power electronics. The device can be created using standard silicon processing techniques, and integrated with other optical components such as splitters and combiners to create amplitude modulators, attenuators and other optical devices.

High speed semiconductor waveguide phase-shifter

In accordance with the invention, a variable optical delay line with a large continuous tuning range comprises an incremental variable delay line to provide delay selected from a sequence of incrementally differing delays and a continuous variable delay line to provide a continuously variable delay over a range encompassing a delay increment in the first variable delay line. In a preferred embodiment, the first variable delay line comprises an array of delay paths where each path is curved differently from the others to provide an incrementally different delay. The second variable delay line is a tunable delay path continuously tunable over the delay increment of the first.

Variable optical delay line with a large continuous tuning range

A new filter architecture uses subband division and a reflector structure. A de-multiplexer/multiplexer combination creates N subband branches comprising dispersive elements, phase control elements, and/or delay elements. The new structure yields high spectral accuracy across the filter's overall free spectral range (FSR). In one embodiment of the inventive filter, the overall filter has a free spectral range (FSR) of F, and the first multiband filter (MBF) has a FSR of The N subband outputs of the first multiband filter create a plurality of branches. Each branch comprises a dispersive element and optionally one or more elements such as a phase control element and/or a delay element. A reflector at the end of each of these branches reflects the light back through the branches and each of the MBFs and the first MBF.

Optical all pass filter device having improved time-bandwidth behavior

A single-stage all-pass optical filter is disclosed that may be applied to generate a large tunable delay of an optical pulse train. The all-pass optical filter includes an input port for receiving an input optical pulse having a regular repetition rate; an output port; a splitter/combiner; and one feedback path. A plurality of frequency-dependent time delay periods are applied to the input optical pulse so that the filter is characterized by a time-delay spectrum having a plurality of delay peaks. The free-spectral range (FSR) of the filter, i.e., the spacing between the delay peaks, is matched to the regular repetition rate of the input optical pulse. This matching is accomplished by the FSR being equal to the repetition rate or offset from the repetition rate to a sufficiently small degree that each frequency of the pulse train will fall within the bandwidth of one of the plurality of delay peaks. This single-stage all-pass optical filter is advantageous for correcting linear chirp of a pulsed laser or synchronizing control signals in an optical time-division multiplexer/demultiplexer system.

System comprising a single-stage all-pass optical filter

Various apparatus and methods for generating a 90&#xb0; AP optical pulsetrain. In one embodiment, the apparatus includes: (1) a phase-modulated optical signal generator configured to generate a phase-modulated optical signal having a carrier band and sidebands phase-shifted relative thereto by multiples of 90&#xb0; and (2) an optical filter coupled to the phase-modulated optical signal generator and configured to 180&#xb0; phase-shift selected ones of the carrier band and sidebands to generate the 90&#xb0; AP optical pulsetrain.

Apparatus and method for generating a 90&#xb0; alternate phase optical pulsetrain

In accordance with the invention, a variable delay line with continuous tuning comprises an optical path providing at least one continuous delay element coupled to a series of switchable binary fixed delays. The series of switchable delays can be configured to select a delay among a plurality of incremental delays, and the continuous delay can set a continuous delay in a range encompassing the delay increment of the binary series. In a preferred embodiment, the variable delay element comprises a tunable all pass filter (APF) with delay tunable from essentially 0 to a time T and the switchable binary fixed delays form a series (0,T), (0, 2T), (0, 4T), . . . , [0, (2n+1)], where n is an integer &#x2267;0. The switches are preferably Mach-Zehnder switches. In an alternative embodiment, the continuous delay element comprises a suitable pair of APF arms. The path and all components can be fabricated as an integrated planar waveguide (solid state) device.

Compact solid-state variable optical delay line with a large continuous tuning range

In accordance with the invention, an optical fiber is coupled to a planar waveguide through 1) a series of planar waveguide segments of enlarged cross section and 2) a segment of vertically tapered cross section. The combination of spaced segments and tapered segments provide efficient coupling over a much shorter length than required for conventional adiabatic coupling.

Method and apparatus for compactly coupling an optical fiber and a planar optical waveguide

In accordance with the invention, a high speed thermo-optic phase shifter comprises a length of optical waveguide including a waveguiding core of a first material having an index of refraction nand a first order temperature dependence |dn/dT| and, optically coupled to the core, a length of a second material having an index npreferably greater than the core (n&#x3e;n) and a first order temperature dependence |dn/dT| than the core (|dn/dT|&#x3e;|dn/dT|). Advantageously, the length of second material is adiabatically tapered at both ends. Upon heating, as by a resistance heater, the second material changes the optical pathlength by an amount predominantly determined by |dn/dT| providing faster switching speed. In a preferred embodiment, the core comprises silica, and the second material comprises silicon to produce switching speeds up to a few hundred MHz.

High speed thermo-optic phase shifter and devices comprising same

In accordance with the invention, an MZI-based reconfigurable multi-channel filter is provided with enhanced channel bandwidth by adding an all-pass filter to one or both of the MZI arms. The result is a square-shaped amplitude response closely approximating the ideal.

Reconfigurable multi-channel filters having enhanced channel bandwidth

A liquid crystal polarization rotator device is able to rotate polarization fast enough to compensate polarization mode dispersion. The amount or degree of rotation is rapidly reconfigurable. The device includes a cavity filled with a nematic liquid crystal material. The cavity has electrodes on a first face, e.g., a first substrate, and electrodes on a second face, e.g., a second substrate, opposite the first face. The electrodes are shaped and positioned to produce an electric field across the cavity capable of rotating the alignment direction of the molecules of the liquid crystal material in the cavity. The electrodes are patterned on the ends of optical fibers. Aligning and positioning of the electrodes on the ends of the optical fibers with a predetermined spacing forms the cavity that is filled with the nematic liquid crystal material. The filled cavity is a so-called liquid crystal microcell wave plate. A control system is used to control the 'rapid' rotation of the alignment direction of the molecules of the liquid crystal material. The control system receives data regarding the polarization of light entering or leaving the microcell and adjusts the direction of the electric field also using trigger pulses such as to rotate the nematic liquid crystal material molecules by a first predetermined number of degrees greater than a second desired number of degrees of rotation. Then, the trigger pulses for the electric field are stopped after the molecules have rotated by the second desired number of degrees. In this manner, the molecules rotate by the second desired number of degrees much faster than if a pulse had been applied with the same speed to rotate them by the second desired number of degrees in he first place.

Liquid crystal polarization rotator and method of using same

In accordance with the invention, an optical fiber transmission system is provided with a new method and apparatus to measure PMD and then to use the measurements to control adaptive optical filters that minimize system signal degradation. The measurements provide accurate information to compensate for distortions and thereby permit higher transmission rates. The new technique can obtain phase information without optical heterodyning and without bandlimiting. In a first embodiment, an optical signal transmitter, such as a laser/modulator pair, is driven by a data signal combined with a test signal, in the form of a comb of tones with known relative magnitude and phase relationships. Tunable all pass filters recover phase and magnitude information to control an adaptive filter for precise compensation. In a second embodiment, no changes are made to the transmitted signal. The relative delay between orthogonal polarizations of a modulated signal can be obtained by using a polarization beam splitter (PBS), flipping (rotating by 90&deg;) the polarization of one output, sweeping a narrowband optical filter (NBF) across the signal spectrum and detecting the interference between polarizations. Additional detectors can obtain the magnitude versus frequency for the orthogonal components, x and y.

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South Plainfield, NJ, United States of America

Christi Kay Madsen