Coupled few mode fibers, and corresponding optical link and optical system

Abstract

An optical fiber having an optical core and an optical cladding surrounding the optical core, the optical core having a single α graded-index profile with α≥1, α being a non-dimensional parameter that defines the index profile shape of the optical core, and the optical core having a maximal refractive index nat its center; the optical cladding has at its outer edge a refractive index n, and comprises a region of depressed refractive index n, called a trench, with a negative refractive index difference Δn=n−nwith respect to said optical cladding, the trench having an outer radius R. The optical core and cladding are configured to support propagation of at least six spatial modes and at maximum fifty-five spatial modes at an operating wavelength λbetween, and including, 1460 nm and 1675 nm, and the optical core satisfies an ovality criterion between 0.05 and 0.3, when said ovality criterion is measured at a circumference of equal index nwithin said core, such that Δn−n−nis less than 75% of Δn=n−n, said ovality criterion o being defined by the following equation: where a is a length of a semi-major axis of said circumference and b is a length of a semi-minor axis of said circumference.