Northern Telecom Limited

Stc, Inc

Nortel Networks Corporation

International Standard Electric Corporation

Bookham Technology Limited

Standard Telephones & Cables Public Ltd. Co.

Terry Bricheno

Alan Fielding

James E Whiteaway

Richard E Epworth

George H Thompson

Kevin C Byron

Stephen Day

James Wilson Parker

Stephen Wright

Alan Robinson

Philip W Black

Sureshchandra Mishrilal Ojha

Norman Derek Leggett

Michael F Grant

Robert A Baker

Brian A Eales

Vernon Baker

Alexander J Robertson

David John Moule

Sandra Davis

George H B Thompson

Gregory John Milner

John S Leach

Clifford Graham Cureton

Ross K Finlay

John E Ashton

Nicholas A Hewish

Nicholas J Pitt

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.

An assembly for combining the outputs from a group of n single mode optical fibres on to the photosensitive surface of a photodetector ( ) has an adiabatically tapered bundle ( ) of fibres ( ) the small end of which is fusion spliced to one end of a length ( ) of multimode fibre whose other end is optically coupled with the detector ( ) by means of a lens ( ).

Waveguides to photodetector assembly

It is found that the use of a multimode interference (MMI) section to flatten the pass-bands of an arrayed waveguide grating (AWG) multiplexer/demultiplexer or comb filter device introduces undesirable wavelength dispersion into those pass-bands if that MMI section mixes modes of more than two different orders, and if the grating of that device is a 'uniform' grating whose waveguides are equally (minimally) attenuating, and in which the optical path length difference between each adjacent pair of waveguides of the array is the same. This dispersion can be substantially compensated by appropriate 'tailoring' of the grating to remove such uniformity

Optical arrayed waveguide grating devices

An optical comb filter is constructed from a monolithic arrangement of two identical integrated optics format arrayed waveguide diffraction gratings connected back-to-back via a star coupler incorporating a field stop (spatial filter,Alternatively, only one of the diffraction gratings is employed in conjunction with a combined field stop and retro-reflector, the other end of the diffraction grating being optically coupled with one port of an optical circulator.

Optical comb filter

Optical multiplexter/demultiplexer

A dispersion compensator exhibiting low polarisation mode dispersion is constructed from a polarisation beam-splitter, a .pi./4 rotation Faraday rotator, and a matched pair of polarisation maintaining fibres provided with a matched pair of chirped Bragg reflection gratings. The waveguides are oriented with respect to the beam-splitter so that light reaching the waveguides from the beam-splitter via the rotator is launched into both waveguides with a polarisation state aligned with the same polarisation axis (i.e. both fast or both slow).

Dispersion compensation with low polarization mode dispersion

A planar optical waveguide comprises at least two cladding layers on a substrate with at least one core layer disposed between the cladding layers. The overcladding layer of the two layers is doped in order to produce a thermal coefficient of expansion close to or equal to that of the substrate in order to reduce the polarisation sensitivity of the device.

Planar optical waveguide

Optical fiber elements, such as narrow pass-band filters, dispersion equalizers, and channel dropping filters, are constructed from 2.times.2 single mode optical fiber fused tapered couplers having formed on one side of coupling regions Bragg distributed gratings in the two fibers from which the coupler is constructed. By making the gratings at a point where the fibers remain fused together in side-by-side contact it is ensured that they lie equidistant from the coupling region.

Optical fibre Bragg distributed gratings

During the photo-induced creation of a Bragg grating in a photosensitive optical fibre using the interference fringe pattern generated in the near field of a phase grating, the spacing between fibre and phase grating is modulated.

Method of creating bragg gratings in waveguides

Optical coupling between the end of a laser (10) mounted on a silica motherboard (12) and an optical fibre (11) is effected with the aid of a silicon platform (14) to which the end of the fibre (11) is secured. The motherboard (12) and fibre platform (11) are crystallographically etched to provide complementary mating profiles with a clearance of less than 10 .mu.m when alignment is established. While that alignment is maintained, resin (23) is introduced between motherboard and the fibre platform, and is cured. The minimal thickness of the cured resin minimises misalignments caused by resin shrinkage.

Method and apparatus for providing optical coupling between optical

An optical fibre amplifier in which a length of optically amplifying fibre is spliced between a pair of 2.times.2 tapered fused fibre couplers each constructed from a length of amplifier type profile fibre and a length of transmission type profile fibre. In each coupler, one of two constituent fibres has been pre-stretched so as to match the propagation constants of the two fibres within the coupling region of that coupler.

Optical fibre amplifier

A 1.times.N single mode optical waveguide coupler comprises a single input optical fibre (1), a slab-like mixer waveguide (3) and a plurality (N) of output optical fibres (2). As a result of interference effects light introduced into the mixer waveguide (3) via the centrally located input fibre (1) produces a linear array of output spots at various intervals along the length of the mixer waveguide. The length of the mixer waveguide is chosen such that the output optical fibres are aligned with one such array of output spots. The fibres may be adiabatically tapered to a smaller diameter in order to increase their modal spot size.

Single mode couplers

An optical fibre star coupler in which the mixer element (11, 21, 45) exhibits optical gain. This allows the use of couplers having a relatively large number of outputs without the requirement for an excessive power level for any input signal.

Active optical fibre star couplers

A non-circularly-symmetric intensity distribution is formed on a quadrant photodetector by coherently mixing two optical signals propagating in selected modes of different order. These modes are chosen either such that a change in relative phase of the two signals produces solely a rotation of the orientation of that intensity distribution, or such that a change in relative states of polarization produces this rotation.

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Great Sampford, United Kingdom

Terry Bricheno