“…Brown and Hoffman [11] developed a conventional temperature distribution model for continuous-wave (CW) fiber lasers. Using this model, the temperature distribution inside the active fiber can be described by the heat-conduction equation [12]. Combined with the continuous boundary conditions [13,14] of a fiber, the following analytical expressions for the radial temperature distribution T(r) in the core, cladding and coating regions can be formulated [14] where a, b, and c denote the radii of the core, inner cladding, and coating, respectively; k 1 , k 2 , and k 3 represent the heat conductivities of the core, inner cladding, and coating region, respectively; T 0 is the center temperature of the core; T C is the coolant temperature; Q(z) is the heat power density along the fiber [15], which can be expressed as follows…”