A study to maximize the total conversion efficiency and reduce the payload for Nd/Cr doped fiber laser had been performed. Laser oscillation has been observed in a multimode Nd‐doped fiber laser with “D‐shaped” clad under quasi‐solar pumping simulated by an intense metal‐halide arc lamp of which color temperature was 5600 kelvin. The fiber is 78‐m long. The Nd doping rate was 3000 ppm in silica core‐glass. The output power obtained was 300 mW when the injected power of lamplight was1.1 W at the entrance of the fiber and the optical‐optical conversion efficiency was over 25&percent;. The threshold of the input power for laser oscillation is 24 times of the solar constant in space. This value is one order lower than the case of crystal lasers which had been reported under solar‐pumping. © 2004 American Institute of Physics