AN AMPLIFYING OPTICAL DEVICE

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An amplifying optical device (10) for providing optical amplification, the amplifying optical device (10) comprising at least one pump (11) for supplying pump radiation, at least one pump optical fibre (1) and at least one amplifying optical fibre (2), the amplifying optical device (10) being such that : the pump optical fibre (1) and the amplifying optical fibre (2) are coated with a common coating (3) and are in optical contact along a portion of their length (4), the pump optical fibre (1) is separated from the amplifying optical fibre (2) at two end portions (5, 6) of the common coating (3), one of the separated end portions (5) of the pump optical fibre (1) is connected to the pump (11), the pump optical fibre (1) and the amplifying optical fibre (2) comprise glass (7), the amplifying optical fibre (2) comprises a core (8) and a cladding (9), the core (8) is doped with at least one rare earth dopant (12), and the amplifying optical device (10) being characterized in that : the pump optical fibre (1) comprises a mode coupling means (15) in the form of a variation of refractive index with azimuth along at least one circle of constant radius, which variation has at least one azimuthal harmonic having an amplitude greater than an amplitude of a first and a second azimuthal harmonic, and which thereby couples guided modes of the pump optical fibre (1) to guided modes of the amplifying optical fibre (2) that overlap and can be absorbed by the rare earth dopant (12) in the core (8).