Embodiments of the present invention are generally related to a high-power liquid-cooled pump and signal combiner and methods thereof for fiber optic applications. More specifically, embodiments of the present invention relate to a pump and signal combiner capable of conveying several kilowatts of pump laser power for kilowatt class rare-earth doped fiber amplifiers without suffering thermal damage. In one embodiment of the present invention, a high-power, heat dissipating optical fiber device comprises a section of optical fiber configured to propagate light, a cooling chamber, substantially encapsulating the optical fiber, and a fluid within the cooling chamber having a refractive index selected to control the interaction and propagation of the light in the fluid.