| 摘要 |
A tuneable optical fibre comprising a long-period Bragg grating (<bold>5</highlight>) written in a portion of an optical waveguide (<bold>10</highlight>) comprising a core and an optical cladding (<bold>11</highlight>), characterised in that the portion of the waveguide comprising the grating (<bold>5</highlight>) is at least partially immersed in an external environment consisting of two distinct sections, a first section (<bold>1</highlight>) whose refractive index is higher than that of the optical cladding (<bold>11</highlight>) and a second section (<bold>2</highlight>) whose refractive index is lower than that of the optical cladding (<bold>11</highlight>), the long-period grating being at least partially immersed in one of the said sections so as to almost independently tune the wavelength and/or the contrast of the spectral response of the filter.
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