OPTICAL-FIBRE DEVICE COMPRISING A DIFFRACTION GRATING

摘要

Optical-fibre device comprising an optical fibre (1) and a diffraction grating (4) made into said optical fibre, said optical fibre (1) having a core (2), a first radius (R1) and a first refractive index (n1); a first cladding area (3a) made around said core (2) and having a second radius (R2) and a second refractive index (n2) lower than said first refractive index (n1); and a second cladding area (3b) made around said first cladding area (3a) and having a third radius (R3) and a third refractive index (n3) greater than said second refractive index (n2) and lower than said first refractive index (n1); the grating (4) being made into the core (2) along a longitudinal axis of the fibre (1) and being of the variable pitch type; the first and the second radiuses (R1R2) and the first, second and third refractive indexes (n1, n2, n3) are selected so that the effective refractive index (neff) of at least one higher order mode is greater than the third refractive index (n3).