The temperature distribution inside a double-cladding optical fiber laser or amplifier is examined in detail. Traditionally, the quantum defect in the core is taken to be the main source of heating in an active optical fiber. However, contributions from the parasitic absorption of the signal and the pump may also play an important role, especially for low quantum defect or radiation-balanced lasers and amplifiers. The contributions to the heating in both the core and the inner-cladding are considered and analyzed in general terms in this paper. In particular, it is shown that if the maximum tolerable surface temperature of the fiber relative to the ambient is taken to be 300°C to avoid damaging the fiber’s outer polymer cladding, the core temperature rises only in the range of 0°C–5°C relative to the inner-cladding for an air-cooled fiber. However, for a water-cooled fiber, the core temperature can be higher than the inner-cladding by as much as 50°C, potentially changing a single-mode core to multimode due to the thermo-optic effect.

中文翻译：

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双包层光纤激光器或放大器内部的温度分布

详细检查了双包层光纤激光器或放大器内部的温度分布。传统上，纤芯中的量子缺陷被视为有源光纤中的主要加热源。但是，信号和泵浦的寄生吸收的贡献也可能起重要作用，尤其是对于低量子缺陷或辐射平衡的激光器和放大器而言。本文从总体上考虑和分析了芯部和内包层对加热的贡献。特别是表明，如果为了避免损坏光纤的外部聚合物包层，将光纤相对于环境的最大容许表面温度设为300°C，则纤芯温度仅在0°C–5的范围内升高相对于空气冷却纤维的内包层为°C。然而，