The effect of dispersion on spectral broadening of incoherent continuous-wave light in optical fibers.

In addition to fiber nonlinearity, fiber dispersion plays a significant role in spectral broadening of incoherent continuous-wave light. In this paper we have performed a numerical analysis of spectral broadening of incoherent light based on a fully stochastic model. Under a wide range of operating conditions, these numerical simulations exhibit striking features such as damped oscillatory spectral broadening (during the initial stages of propagation), and eventual convergence to a stationary, steady state spectral distribution at sufficiently long propagation distances.

Photodarkening-induced increase of fiber temperature.

We examine the effect of photodarkening-induced pump light absorption on Yb-doped fiber thermal loading. In these experiments, the fiber is cladding pumped at 915nm, air cooled by natural convection, and monitored with a midinfrared thermal camera. The fiber temperature is found to correlate with progressive photodarkening.

Thermal bleaching of photodarkening-induced loss in ytterbium-doped fibers.

We study the thermal bleaching process of photodarkening-induced loss in ytterbium-doped fibers. The observed power-law time dependence of the normalized absorption coefficient is well represented by the thermal decay model of Erdogan et al. [J.

Heat-induced darkening and spectral broadening in photodarkened ytterbium-doped fiber under thermal cycling.

We study thermal bleaching of photodarkening-induced loss in a 20-microm core diameter, large-mode-area ytterbium-doped silica fiber. Pristine and photodarkened samples are subjected to thermal cycling pulses. Recovery of the photodarkened fiber absorption coefficient initiates at approximately 350 degrees C and complete recovery is reached at approximately 625 degrees C.

Photodarkening rate in Yb-doped silica fibers.

Yb-doped fibers are widely used in laser applications requiring high average output powers and high-peak-power pulse amplification. Photodarkening (PD) is recognized as one limiting factor in these fibers when pumped with high-intensity radiation. We describe an approach for performing quantitative PD studies of fibers, and we present measurements of the rate of PD in Yb-doped single-mode fibers with varying inversion levels.