Bell Telephone Laboratories

At&t Bell Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

Lucent Technologies Inc.

American Telephone and Telegraph, Co.

At+t Corp.

At&t Company and At&t Bell Laboratories

Rodney C Alferness

Steven K Korotky

Gadi Eisenstein

Thomas L Koch

Uziel Koren

Janet L Jackel

Matthew S Whalen

Lawrence L Buhl

Rodney S Tucker

Arun N Netravali

Charles H Henry

Ivan P Kaminow

Thomas Huntington Wood

Herwig Werner Kogelnik

Enrique A Marcatili

Rudolf F Kazarinov

Andrew Gomperz Dentai

Adel A Saleh

Nils A Olsson

Fred L Heismann

Ping K Tien

Jane E Zucker

Zigmantas Leonas Budrikis

Tomas Brenner

Ronald V Schmidt

Kenneth J Orlowsky

Charles H Joyner, Jr

Vellayan Ramaswamy

David W Hagelbarger

Yosi Shani

Susan P Lyman

A wavelength filter has a low index waveguide, a high index waveguide and a grating for coupling therebetween. The high index waveguide is in horizontal proximity to said low index waveguide. The low index waveguide and said high index waveguide have substantially different geometries which result in substantially different indices. A method for fabricating the wavelength filter is also disclosed.

Design and method for planar coupled waveguide filter

Wavelength division multiplexing, spatial switching cross-connect structures which may be deployed as intermediate nodes of an all optical network to route any input channel on any source fiber to any destination fiber at any available wavelength to achieve full connectivity between the nodes of the network. The non-blocking cross-connect structure comprises a wavelength division demultiplexer for receiving multiple wavelength channels from each source fiber and for separating received channels into N wavelengths so that the wavelengths are organized according to a corresponding fiber of origin, a nonblocking optical structure for spatially and independently rearranging the received wavelengths so that wavelengths having a common destination fiber are grouped together, and a wavelength division multiplexer for multiplexing together wavelengths having the same destination fiber.

Non-blocking optical cross-connect structure for telecommunications

A double-periodic grating is described for obtaining polarization-independent filtering and coupling. The grating may be viewed as a combination of two gratings with slightly different grating periods. The two periods are carefully chosen to match the difference in propagation constants of the TE and TM polarization modes such that both modes are coupled at the same wavelength. A novel method of obtaining a double-periodic grating is described.

Polarization-independent optical wavelength selective coupler

Various optical functions are generated in accordance with the present invention of a novel broadly tunable monolithic wavelength selective coupler which can be integrated with a gain medium to form a broadly tunable laser. The tunable wavelength selective coupler supports a pair of asynchronous waveguides, an upper waveguide and a lower waveguide, in combination with a phase match course grating for coupling optical energy between said waveguides. One end of the lower waveguide terminates at an output facet. The corresponding end of the upper waveguide terminates in an optical signal absorbing medium. The other end of the lower waveguide is terminated to prevent optical energy from entering the waveguide; and, the corresponding end of the upper waveguide terminates at an input facet. The combination of a gain section and the monolithically tunable wavelength selective coupler forms a broadly tunable laser which is an important source of optical energy for a number of applications such as wavelength division multiplexed networks and switching systems. The laser frequency is determined by that wavelength .lambda.o which satisifies the forward coupling phase match condition, .lambda.g=.LAMBDA..vertline.N.sub.2 -N.sub.1 .vertline. of the coupler where .LAMBDA. is the coarse grating period and N.sub.1, N.sub.2 are the effective indices of the two waveguides. Wavelengths which are not coupled from the upper waveguide to the lower waveguide are attenuated in the optical signal absorbing means. Tuning of the laser wavelength is achieved by either injecting current into or applying a reverse bias voltage to the upper waveguide to decrease or increase its index respectively and change the coupled wavelength.

Tunable optical waveguide coupler

Polarization rotation is achieved in an exemplary embodiment in an optical waveguide by augmenting the waveguide structure with a plurality of spaced-apart sections for loading the refractive index of the waveguide to cause a lateral asymmetry in the refractive index profile of the waveguide viewed in the plane transverse to the waveguide longitudinal axis. Each spaced-apart section induces non-zero coupling between the principal orthogonal polarization modes. Phase matched coupling between the principal orthogonal polarization modes is achieved by spacing the sections periodically by a distance .LAMBDA. equal to .lambda./.DELTA.N where .lambda. is the propagation wavelength in the waveguide and .DELTA.N is the difference between the effective refractive indices for the principal orthogonal polarization modes. Realizations of the waveguide structure are shown using Group III-V semiconductor rib waveguide structures.

Asymmetric, periodically loaded waveguide for polarization rotation

An arrangement for butt coupling of waveguide electrooptic plates to form a crossbar switch. The arrangement includes a stack of M splitter plates, each of which routes an injected optical signal to one of N outputs, and a stack of N combiner plates, each of which routes the signal of a selected one of M inputs to a common output. The stack of splitter plates is rotated with respect to the stack of combiner plates and the output signal ports of the splitter plates are coupled to the input signal ports of the combiner plates, so that each output of an splitter plate is connected to a different combiner plate. Within each splitter plate there is a fan-out network of waveguide electrooptic couplers and each coupler, under electric control, routes signals from one input to either one of two outputs. With j levels of such interconnected couplers 2.sup.j output are developed. The combiner plates have an identical architecture but with a signal flow in the reverse direction. Butt coupling of the splitter and combiner plates is achieved by employing splitter and combiner plates of a different crystal cut, by interposing polarization rotation means between two stacks, or by including polarization rotation means within the splitter plates, the combiner plates or both.

Optical interconnect arrangement

Disclosed is a time division multiplexed optical communication system that is capable of operation at relatively high bit rates and that is relatively stable and immune to crosstalk and noise. The system comprises receiver means wherein the timing signal for demultiplexing is derived from the fully multiplexed optical pulse stream by means that comprise a narrow band receiver and timing means that produce a lower-frequency timing signal from the output of the narrow band receiver. The timing signal is used to drive one or more optical switches. In one embodiment of the invention the receiver means have a binary-tree architecture and the timing signals are substantially sinusoidal. In another embodiment the receiver means have a linear-bus architecture and the timing signals are pulse-like.

Division multiplexing and demultiplexing means lightwave communication

Wavelength tunability and single frequency output are achieved in a coherent light source employing an adjustably controllable reflector. The light source includes a gain medium coupled to a single-mode fiber having a partially reduced cladding region at a predetermined distance from the gain medium. A Bragg reflector is either formed on the reduced cladding region of the single-mode fiber or formed on an external element in close proximity to the reduced cladding region. A single resonant optical cavity is formed by placing another reflector on the side of the gain medium opposite the gain medium-to-fiber coupling. Wavelength tuning of the light source is accomplished by controllably adjusting the period or the Bragg reflector element.

Wavelength tunable composite cavity laser

A grating coupler is combined with a quantum well index modulator and an optical waveguide to alter the reverse or forward coupling characteristics between two different propagation modes of the system.

Grating coupler with monolithically integrated quantum well index

An optical power tap is disclosed which allows effectively nonreciprocal injection and removal of power at each node of a single-mode optical fiber local area network. The power tap uses a wavelength-selective directional coupler to inject and remove power from the bus, and a nonlinear converter in the bus to convert light from one wavelength to another. In the specific embodiment disclosed a neodymium-doped silica fiber is used as a nonlinear material to convert light from one wavelength to another.

Single-mode optical fiber tap

Highly frequency-selective reflectivity is realized in an optical device including a waveguide and an evanescent-field coupled grating resonator cavity. The device may include a light source and serve as a low-chirp, narrow-linewidth communications laser for use, e.g., for transmission over a fiber having non-negligible dispersion and also in wavelength-multiplexed coherent systems.

Narrow-linewidth resonant optical device, transmitter, system, and method

A structure of first and second grating sections separated by a phase-shift section serves as a narrow-band resonator filter. Such structure may be optically coupled to a semiconductor laser cavity, and the resulting assembly can serve as a tunable narrow-linewidth laser, e.g., in wavelength-multiplexed and coherent-lightwave communications systems.

Optical communications laser including a resonator filter

An optical filter using first and second grating sections separated by a changed refractive index section operates as a narrowband grating resonator.

Optical waveguide resonator filters

Low loss semiconductor waveguides for supporting propagation of optical signals over a wide range of wavelengths are achieved by growing at least two epitaxial layers of dopant material contiguous along a major surface of each layer to form a heterointerface therebetween. At least one of the epitaxial layers includes a sufficient concentration of semiconductor material to cause strain via lattice mismatch substantially at and near the heterointerface. The strain induces a change in refractive index such that the heterointerface exhibits a substantially higher refractive index than a portion of each epitaxial layer proximate to the heterointerface. The resulting waveguide is capable of supporting propagation of optical signals substantially along the heterointerface. In one example, contiguous epitaxial layers of InP and InGaP form a waveguide for optical signals at wavelengths greater than 0.93 .mu.m. The concentration of Ga in the InGaP epitaxial layer is varied from 10.sup.18 to 10.sup.20 cm.sup.-3 to increase the refractive index difference between the heterointerface and the immediate surrounding layers.

Semiconductor heterointerface optical waveguide

Narrow band, wavelength selective optical coupling is achieved in a device including first and second optical transmission media and a filter. The first and second optical transmission media are in substantially close proximity of each other in a predetermined interaction region to provide evanescent coupling therebetween. The filter is positioned on the first optical transmission medium in the predetermined region for causing the coupling to be wavelength selective and contradirectional from the first optical transmission means to the second optical transmission means. One exemplary embodiment of the coupler includes optical fibers as the transmission media and a Bragg reflection grating integrally formed on the first transmission medium as the filter. Other embodiments include the use of semiconductor waveguides as the optical transmission media.

Growing community of inventors

Holmdel, NJ, United States of America

Rodney C Alferness