Aston Photonic Technologies Limited

British Aerospace Public Limited Company

Bookham Technology Limited

Aston University

Lin Zhang

Ian Bennion

Yu Liu

Catherine Anne Sugden

Xuewen Shu

Kaiming Zhou

Karen Elizabeth Chisholm

John A R Williams

Zhijun Yan

Bashir Aliyu Labbo Gwandu

Filip Floreani

Donghui Zhao

John Williams

Mehmet Aytun Erdentug

Christopher Groves-Kirkby

Embodiments of the invention comprise apparatus and methods for detecting the presence of a substance in a test material using a plurality of wavelength-specific couplers (e.g. tilted fiber gratings) which provide a spatially distributed multi-node all-optical measurement system. Each node of the measurement system can comprise an optical module that is sensitive to the intensity of a limited band of wavelengths. The node is thus capable of detecting the presence of an absorption peak in a spectrum without having to obtain the full spectrum. By providing a plurality of optical modules that are sensitive to different wavelengths, the spectral signature of different substances may be monitored without having to measure full spectra. The measurement system may be particularly useful in a process control environment where it is desirable to take measurements of one or more substances in different locations.

Optical detector module, measurement system and method of detecting presence of a substance in a test material

A regenerated optical waveguide is fabricated by hydrogenating an optical waveguide () and exposing a grating section () to a UV laser beam interference fringe pattern () to form a Type I grating. The grating section () is exposed for a second period to erase the Type I grating, and then a third period to cause a regenerated optical waveguide grating to form. The resonant wavelength increases during the third period from being substantially the same as the final wavelength of the Type I grating.

Methods of fabricating a regenerated optical waveguide grating

In the present invention an optical waveguide grating sensing device for a dual-parameter optical waveguide grating sensor includes a first optical waveguide grating of a first resonant wavelength provided in a first section of an optical waveguide and a second optical waveguide grating of a second resonant wavelength provided in a second of an optical waveguide. The first and second gratings have different coefficients of rate of change of wavelength as a function of temperature and have substantially the same coefficient of rate of change of wavelength as a function of stain.

Dual-parameter optical waveguide grating sensing device and sensor

A strain sensor comprises an optical waveguide having a plurality of reflecting structure (Bragg grating) along its length. Each structure reflects light at a different characteristic wavelength (&lgr; to &lgr; ) which changes in dependence on a change of physical length of at least part of the reflecting structure. The reflectivity of reflecting structures which reflect at characteristic wavelengths which are adjacent to each other (&lgr; and &lgr; or &lgr; and &lgr; ) are configured to be different such that the intensity of light reflected from adjacent structures can be used to discriminate between them.

Strain sensing

A fiber optic grating sensor ( ) comprising an optical fiber ( ) in which a grating portion ( ) is provided, the refractive index ( ) of the fiber ( ) varying periodically along the grating portion ( ). The periodic variation of the refractive index ( ) has an amplitude envelope which includes, in this example, two regions ( ) in which the amplitude of the envelope is substantially reduced, and in this example is substantially nulled. The null regions ( ) give the grating portion a spectral profile ( ) within which there are, in this example two pass bands ( ).

Fibre optic grating sensor

Apparatus for sensing temperature and/or strain in an object includes a broadband light source (1), connector means (2) in the form of an optical circulator or an optical coupler to which at least two substantially identical optical fiber Bragg gratings (4, 5) are connected. Grating (4) receives the broadband light from the connector means (2) and functions as a sensor of temperature and/or strain in an object. Light is reflected back from the grating (4) to the connector means (2) and then passed to the grating (5) which acts as a reference grating through which a light output signal is transmitted to a detector (8) which is conveniently a photodetector. Means are provided for chirping the two gratings (4, 5) at the same bandwidth and the detector (8) measures the intensity of the received light output signal, with the intensity being monotonically related to the change in temperature and/or strain sensed by the grating (4) in the object.

Apparatus for sensing temperature and/or strain in an object with

Growing community of inventors

Birmingham, United Kingdom

Lin Zhang