Aston University

Aston Photonic Technologies Limited

Karen Elizabeth Chisholm

Catherine Anne Sugden

Lin Zhang

Ian John Murgatroyd

Apparatus () for interrogating an optical signal (not shown) propagating in an optical waveguide, such as an optical fiber, having an input section () and a second section () through which light entering from the input section () will subsequently propagate. The second section () includes a grating portion, such as a tilted chirped fiber Bragg grating (). The grating () causes at least part of the optical signal to be coupled out of the optical fiber, through the fiber cladding. A photodetector () is provided generally alongside the grating (). The photodetector () is arranged to collect and detect substantially all of the outcoupled optical signal. The relationship between the optical power outcoupled by the grating () and the wavelength of the optical signal is known, allowing a measurement of the outcoupled optical power to be used to determine the wavelength of the optical signal propagating through the grating ().

Apparatus for interrogating an optical signal

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 ( ).

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Karen Elizabeth Chisholm