The intent of this test procedure is to measure the central wavelength, peak wavelength, and the spectral width (rms, MSTM, 15 dB down and FWHM)(Footnote 1) of a Multilongitudinal Mode (MLM) semiconductor laser diode using a dispersive spectrophotometric (using a revolving diffraction grating) method or other suitable methods. EYE SAFETY WARNING. Exercise care to avoid possible eye damage from looking into the end of an energized fiber from a laser source. Most importantly, personnel should avoid looking into any energized fiber using any type of magnification device. Footnote 1 - rms is the Root Mean Square, MSTM is the Maximum Skew Tenth Maximum (10 dB down) and FWHM is Full Width Half Maximum (3 dB down).