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Patent Granted on New Erbium-Doped Fiber

A patent has recently been granted to Fitel USA Corp., a parent company of OFS, for an erbium-doped fiber that is optimized for high-power
wavelength-division multiplexing (WDM) applications.

Erbium-doped fiber amplifiers are widely used in long-haul telecom and CATV applications. But these fibers have not been suitable for high-power amplifiers because they lack the required relatively flat gain spectrum and a low refractive index and thus a low numerical aperture (NA). Until now, it was possible to achieve a low NA, but the gain spectrum was not sufficiently flat. A fiber core doped with high concentrations of aluminum produces a flat gain spectrum, but aluminum also increases the NA.

OFS scientists have resolved this conflict by developing a fiber with an erbium-and germanium-doped core that is also doped with aluminum and fluorine. The aluminum helps achieve a relatively flat gain spectrum while the presence of fluorine lowers the refractive index – and thus the NA – even in the presence of aluminum.

This new fiber, HP980X, is a significant addition to the OFS family of erbium-doped fibers. In high-power WDM applications they make possible high power conversion while reducing both nonlinear effects, such as four-wave mixing, and excited state absorption.

Erbium-Doped Fiber Evolution

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