Plessey Overseas Limited

Plessey Handel Und Investments A.g.

Gec-marconi Limited

Marconi Caswell Limited

Ericsson Ab

Marconi Communications Gmbh

Marconi UK Intellectual Property Limited

William James Stewart

Rosemary Cush

Michael C Wiltshire

David James Robbins

John B Pendry

Ruth Hibberson

Anthony J Holden

Andrew Cannon Carter

David R Wight

Douglas C Reid

Mark C Farries

John A Robinson

Nicola Shaw

Jens Buus

John P Dakin

Richard Carpenter

In a telecommunication system, channels of information are modulated onto respective carriers that are swept repeatedly across a frequency range in a time-staggered fashion so that, at any one time each carrier is at a different frequency. The carriers are multiplexed onto a single communications link and separated, on reception, by filters swept in synchronism so as to de-multiplex the signals.

Communications system

The present invention provides a wavelength selective optical filter device ( ) for receiving input radiation and outputting corresponding filtered output radiation, characterized in that the filter device ( ) includes a plurality of at least partially mutually coupled Fabry-Perot optical resonators ( ) for filtering the input radiation to generate the output radiation, the filter device ( ) being tunable from a first radiation wavelength to a second radiation wavelength by mutually detuning the resonators in a period where the resonators are being retuned from the first wavelength (&lgr; ) to the second wavelength (&lgr; ) so that the filter device ( ) is substantially in a non-responsive state during the period. The resonators incorporate freely suspended mirrors ( ) which are electrostatically actuated to affect tuning of the resonators ( ). The filter device ( ) is thereby capable of tuning between different wavelengths without tuning through wavelengths therebetween. The filter device ( ) can be included into an add-drop filter ( ) for providing channel add and drop functions when the filter ( ) is incorporated in a multichannel WDM communication system ( ).

Wavelength selective optical filter

A structure which exhibits magnetic properties when it receives electromagnetic radiation is formed from an array of capacitive elements each of which is smaller, and preferably much smaller, than the wavelength of the radiation. Each capacitive element has a low resistance conducting path associated with it and is such that a magnetic component of the received electromagnetic radiation induces an electrical current to flow around the path and through the associated element. The creation of internal magnetic fields generated by the flow of the induced electrical current gives rise to the structure's magnetic properties.

Structure with magnetic properties

An optical modulator includes an optical input; an optical output; at least one optical path connecting the optical input and output; and an electrode structure for selectively changing the optical characteristic of a part of the at least one optical path in response to a control signal such as to modulate light passing along the optical path. The optical path further includes a structure which slows the passage of light along the part of the optical path to enhance the modulation effect of the modulator for a given length of optical path. Preferably the structure comprises a sequence of coupled resonator structures in which each resonator structure is defined by a pair of partially reflecting planes which define an optical resonator cavity within the optical parts.

Optical modulator

The performance of a microwave antenna is improved by incorporating a fine wire dielectric material which has a dielectric constant &isin; of less than unity at microwave frequencies. The effect of the dielectric material is to refract microwaves so that the antenna appears to have a larger aperture than that of its physical size. Furthermore, by selecting the transmission cut off frequency of the dielectric material, two antenna elements which are intended to operate within different frequency bands can be mounted one behind the other.

Antenna arrangements

The present invention provides a wavelength selective optical filter device ( ) for receiving input radiation and outputting corresponding filtered output radiation, characterised in that the filter device ( ) includes a plurality of at least partially mutually coupled Fabry-Perot optical resonators ( ) for filtering the input radiation to generate the output radiation, the filter device ( ) being tunable from a first radiation wavelength to a second radiation wavelength by mutually detuning the resonators in a period where the resonators are being returned from the first wavelength (&lgr; ) to the second wavelength (&lgr; ) so that the filter device ( ) is substantially in a non-responsive state during the period. The resonators incorporate freely suspended mirrors ( ) which are electrostatically actuated to affect tuning of the resonators ( ). The filter device ( ) is thereby capable of tuning between different wavelengths without tuning through wavelengths therebetween. The filter device ( ) can be included into an add-drop filter ( ) for providing channel add and drop functions when the filter ( ) is incorporated in a multichannel WDM communication system ( ).

A method of proving the integrity of optical paths in an optical communication system wherein the same diagnostic optical signal is transmitted along each path from one end, and each path is provided at its other end with a grating pattern, for example, for producing a pattern of time spaced echoes of the diagnostic signal unique to that path. In one particular embodiment the diagnostic signal comprises an amplitude modulated optical signal and the echoes are produced at a time spacing such that the modulation components of the echoes are in-phase at a different frequency for each path.

Path integrity proving in optical communications systems

An optical device comprising an optical waveguide (13) on a substrate (11) which over part of its length forms one of a stack (15) of coupled optical waveguide sections of the same length, the stack being of a length such that a light wave of predetermined frequency propagating along the waveguide (13) to enter the stack (15) at one end thereof produces light waves at the other end of the stack which are substantially in phase adjacent each waveguide section. The device finds particular application for coupling light from a substrate waveguide into another waveguide, e.g. an optical fibre (27), off the substrate (11).

Light energy broadening coupler

An optical device comprising a length of optical waveguide (1) having incorporated therein an extended sequence of coupled single resonator structures (9) so as to form an optical slow wave structure. The sequence of resonator structures is suitably formed by a Bragg diffraction grating pattern (7) extending along the waveguide.

Optical devices incorporating slow wave structures

An optical sensor includes a resonant mirror device 1, and a prism 2 disposed adjacent the device for coupling a beam of light into the device 1. The device 1 and the prism 2 are mounted on a rotatable platform. A beam of light is produced by He-Ne laser 3 and is linearly polarized with equal TE and TM components by a polarizer 4 arranged at 45.degree. to TE and TM axis. A lens 6 is arranged in the path of the linearly polarized beam of light for focussing the beam of light onto the device thereby providing simultaneously a range of angles of incidence at which the beam of light can be coupled into said device. The platform on which the device 1 and the prism 2 are mounted, is rotated to a position, at which the angle of incidence of beam of light coupled into the device is such that a resonance is excited in said device for at least one of said components. The beam of light reflected from the device is passed through an analyser 11 arranged at 90.degree. to the polarizer 4. On resonance of one or both components, one component is phase shifted to the other between 0 and 2 radians. The beam in this case will be elliptically polarized light and at least a component of light will be passed by the analyser 11 and will be projected as a bright band on a viewing plane. When the phase shift is radian, the beam is linearly polarized, but in the plane of the transmission axis of the analyser and so all the light is transmitted by the analyser.

Optical sensor

This invention describes a technique for improving the sensitivity of a resonant mirror sensor which has particular applications in areas involving sensing at an interface such as immunosensing using immobilized antibodies. By the introduction of a Bragg grating structure in the sensor, there is produced enhanced dispersion and hence enhanced sensitivity in the region close to the band edge. This improves the detection limit of the sensor without changing the composition or involving the sensor size and allows more sensitive operation at reduced incident angles.

Optical sensor including a Bragg grating structure for enhanced

An optical fibre coupling device comprises a mount 11 supporting an optical fibre waveguide having at a fibre end a surface of the fibre core 2 material which is surrounded by a body 3 of cladding material. At the core end a circular symmetric phase plate 7 is centered about the core 2 such that the light from a laser 1 entering or leaving the waveguide experiences a predetermined phase change. The phase change can act to reduce an optical coupling loss which occurs when the device is in use.

Optical fibre coupling device

An optical assay apparatus of the type comprising an optic waveguide and a coating sensitized to a specific assay species. The light signal response of the apparatus is enhanced by coupling a resonant metallic medium to the waveguide and to the sensitized coating. To this end, a metal coated transparent buffer layer may be interposed between the waveguide and the sensitized coating. Alternatively, a metallized optically matched grating can be used in place of the buffer layer or the metallic medium can be of particulate form, with each particle having a sensitized coating. In using the optical assay apparatus, the sensitized coating is exposed to a fluid assay sample. A light beam is directed onto the sensitized coating and reflected onto a detector. The detected light is monitored for any change indicating the presence of the specific assay species in the fluid sample.

Optical assay: method and apparatus

A biosensor includes an optically dense body provided with a coating sensitized to a specific assay species, and an input and output coupling structure. Light signal response is enhanced by incorporating a partially reflecting, partially transmitting medium between the coupling structure and the optically dense body having a lower refractive index. The thickness of such medium is chosen so that light may be coupled by frustrated total internal reflection and to enable the medium to serve as a resonant mirror.

Biosensors

A coupler (FIG. 4) comprising a pair of interwined monomode fibers optically coupled along a portion of their length. The diameter of one fiber is significantly smaller than that of the other and this fiber is thus wound helically. A helical pitch not exceeding 10 mm is chosen. For such pitch, the smaller diameter fiber is appreciably longer. The following inequality thus holds:

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Blakesley, United Kingdom

William James Stewart