Nortel Networks Corporation

Northern Telecom Limited

Bookham Technology Limited

Terry Victor Clapp

Alan Robinson

Stephen Day

Vincent Handerek

James E Whiteaway

Alan Fielding

Robert George Peall

Paul Mark Harrison

Richard Goodwin

An optical amplifier is provided from a body , at least part of which is doped with a rare earth such as erbium. At least one waveguide extends through the doped part of the body. Pump light is input on a side face of the body and is distributed in the body over the length of the waveguide . A reflective coating may be provided away from the pump light input, including on the opposite face to the pump light input, to multiply reflect pump light within the body to distribute the pump light within the body. The body may be in the form of a slab.

Optical amplifier, optical amplifier hybrid assembly and method of manufacture

Dispersion compensation devices are described which comprise waveguides including sampled Bragg gratings which exhibit comb-like reflectance characteristics. The profile of effective refractive index along the length of the grating is controlled to adjust the position of the teeth and/or to control the dispersion exhibited by the device (i.e. to control the chirp of the grating). The devices can thus be used to provide dispersion compensation to any one of a number of wavelength channels in a WDM system. In preferred arrangements, the effective refractive index distribution is set by a applying a temperature distribution along the length of the grating, or by setting an applied electric field.

Dispersion compensation apparatus and method utilising sampled Bragg gratings

The fibre fuse effect, also termed self propelled self focusing (SPSF) is a catastrophic damage mechanism resulting from a runaway thermal affect which can melt optical fibres. A method and apparatus for limiting the damage caused by a fibre fuse is provided by utilising a detector external to the fibre for monitoring the condition of the fibre.

Fibre fuse protection

An optical waveguide format tuneable optical filter is formed using Bragg grating reflectors to define one or more optical cavities of a Fabry P&eacute;rot etalon, the or each cavity of the etalon including one or more slots containing a controllable refractive index medium, for instance a silicone gel whose index is regulated by Joule heating, or a polymer dispersed liquid crystal whose index is electric field regulated. Strong coupling coefficient (&tilde; a few tens mm ) gratings may be made using lithography to form linear arrays of buried high index inclusions extending along the waveguide core axis.

Tuneable optical filters

An optical waveguide phase adjuster with enhanced sensitivity for instance for use in a Mach Zehnder has a monolithic integrated optics waveguide across which one or more thin, e.g. 10 &mgr;m, slots are made. The slots are filled with material whose refractive index varies strongly with temperature or applied field. The insertion loss of such a slot is small for thicknesses of less than about 25 &mgr;m, but begins to rise ever more rapidly thereafter.

Slotted monolithic optical waveguides

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 introduces undesirable non-linear wavelength dispersion into those pass-bands if that MMI section mixes modes of more than two different orders. This dispersion can be substantially compensated by the use of a tandem arrangement of two AWGs with MMIs of differing length chosen to provide complementary dispersions. In the case of a comb filter, an equivalent compensation can be achieved by arranging for the light to make a second passage through the AWG in the reverse direction.

Optical arrayed waveguide grating devices

An optical waveguide Bragg grating spectrally selective reflector is made by ion beam implantation through a photolithographic mask to raise locally the effective refractive index of the guide. This contrasts with the standard method, which uses UV light to raise the index through the agency of the photo-refractive effect.

Optical waveguide Bragg reflection gratings

A known form of electrically controlled optical attenuator is formed by a mach Zehnder waveguide configuration with a variable refractive index element in one arm to modify the undulatory spectral characteristic of the network to give a specific attenuation at a specific wavelength. The spectral characteristic of the network makes the attenuation that it provides wavelength dependent. An attenuator with a wavelength dependence of reduced magnitude is provided by the series combination of two Mach Zehnder networks, one having an electrically controllable optical path length adjuster in its longer interference arm, and the other with its adjuster in its shorter arm.

Electrically controllable optical attenuator

An injection laser assembly mounted upon a crystal substrate [10] employing a back facet monitor is disclosed. A graded index lens [34] focuses light from the, typically, high in diversion and low intensity rays output from the back facet of the laser [30]. To allow repeatable and efficient coupling the graded index lens [34] is mounted within a groove defined in the crystal. Several configurations for mounting a photodiode sensor [P1,P2] are possible.

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Standon, United Kingdom

Terry Victor Clapp