Akira Oyobe

Temperature dependence of the gain in erbium-doped fibers

The temperature dependence of the gain in erbium-doped fibers between -20 and +85 degrees C is discussed. The characteristics of three types of erbium-doped fibers with different erbium concentrations and glass compositions are investigated. The gain decreased with increasing temperature at the rate of -0.07 dB/ degrees C when pumped at 1.48 mu m. The change in the gain was small when pumped at 0.98 mu m. By measuring the change in the absorption and fluorescence spectra with temperature, it is deduced that the change in the gain is mainly due to the change in the saturated population inversion. >

Gain characteristics of ER/sup 3+/ doped fiber with a quasi-confined structure

The fiber-structure dependence of the gain characteristics of Er/sup 3+/ doped fibers pumped at 1.48 mu m is analyzed. The optimum V value is derived theoretically and experimentally. For step-index fibers, the optimum V value is 1.6, which is smaller than that needed to minimize spot size. The fiber with a small V value enjoys a large Er/sup 3+/ confinement effect. For laser diode pumping, an efficiency of 1.7 dB/mW is achieved at 1.536 mu m. The bending characteristics are also described. >

Gain competition in multichannel optical communication systems using erbium-doped fiber amplifiers

Abstract Gain competitions in saturated erbium-doped fiber amplifiers are investigated experimentally in a two-channel system. The experimental results show that, unlike the case of single-carrier amplification, in case of multichannel amplification, large gain compression appears at short wavelength region of the gain profile due to the energy conversion, and that a flat gain profile normally cannot be obtained for saturated amplifiers.

Hermetic erbium-doped fiber coils for compact optical amplifier modules

In recent years, gain characteristics of erbium-doped fibers (EDFs) have been much improved by reducing the erbium concentration1,2 and by adoption of a structure confining the erbium-doped region to the central part of the mode field3 However, these techniques elongated the optimum lengths of the EDFs tens or severa1 hundreds of meters. To mount such long EDFs in compact amplifier modules, they must be coiled up to a small diameter, potentially reducing the mechanical reliability of the EDFs. In this paper we demonstrate a compact and efficient EDF coil with a hermetic carbon coating to prevent mechanical fatigue under the strained conditions.