The Raman gain spectrum of Phosphorous-doped optical fibers (PDF) is known to exhibit, in addition to the pure silica response, a strong 40 THz frequency-shifted Stokes peak relative to the pump. This large shift reduces the number of cascades required in Raman lasers using nested cavities. We report a measurement of the Raman gain coefficient for a PDF. Our measurement scheme has the advantage of requiring only a pump source and no signal. We developed a model taking into account both contributions from spontaneous and stimulated Raman scattering. Raman spectra gathered at several pump powers are fitted against this enhanced theoretical model. The experimental values of the Raman gain coefficient obtained are in agreement with published results.