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Abstract

A tuneable fibre grating transmission filter (10) comprising an optical fibre (12) including a grating section (14) in which a fibre Bragg grating (16) having one or more phase-shifts within its periodic refractive index variation, is provided, and tuning means, in the form of mechanical tuning apparatus (18), to which the grating section (14) is coupled. The tuning apparatus (18) is operable to apply a variable axial strain to the grating section (14) to thereby tune the wavelength of the grating (16). The fibre (12) may be optically coupled to a second fibre, including a second grating section in which a broadband transmission filter inn the form of chirped fibre Bragg grating is provided. The chirped grating has a spectral profile including a pass band of substantially the same bandwidth and covering substantially the same wavelengths as the stop bands and the pass band of the phase-shifted grating (16).

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First Claim