US Patent 7283711 Double-clad photonic optical fiber

The invention proposes a double-clad photonic optical fiber presenting:a fiber core, first cladding surrounding the fiber core, and second cladding surrounding the first cladding;at least one hole in the fiber core; anddoping using a rare earth ion, at least in the core of the fiber.The invention makes it possible to obtain a double-clad fiber with good overlap between the signal and a pump injected into the core. It improves amplification efficiency in double-clad optical amplifiers where the signal is injected into the core of the fiber and the pump into the first cladding.