A polymethylmethacrylate (PMMA) microstructured polymer optical fiber (mPOF) is fabricated and characterized. Using the cut-back technique the fiber loss is measured which is higher than the step-index silica fibers. Through a novel experimental scheme, the backward Stokes spectrum of the fabricated mPOF is recorded over a range exceeding 3000 cm^‑1 during the cut-back method and compared with that of step-index silica fiber. Especially, the gain coefficient of the Raman peak at 2950 cm^‑1 is directly measured, that is without comparing with other known material. The results show a very good agreement with those obtained through other experimental schemes.