"Introduction Intent The intent of this test procedure is to measure the central wavelength@ peak wavelength@ and the spectral width (RMS and FWHM) of a semiconductor light-emitting diode (LED) using a dispersive spectrophotometric method (that is@ using a revolving diffraction grating) or other suitable methods. NOTE: RMS is the Root Mean Square and FWHM is the Full Width Half Maximum (3 dB down). Accuracy and precision The uncertainty of the procedure is determined by the uncertainty of the optical spectrum analyzer and the number of data points selected. The precision of the method is determined by the precision of the optical spectrum analyzer and the resolution setting used. The precision of this procedure may be enhanced by averaging several sweeps. Hazards This procedure involves measurements of energized optical sources. Exercise care to avoid possible eye damage. Do not look into the end of an energized fiber directly or with a magnification device. Applications This procedure is applicable to all light-emitting diodes."