Is the RMS Method for Spectrum Width Calculation on the AQ6370C Optical Spectrum Analyzer FOTP-127 Compliant?

The AQ6370C Optical Spectrum Analyzer was developed in accordance with the IEC standard: WG4 (IEC 61280-1-3) Test procedures for general communication subsystems -Central wavelength and spectral width measurement. We cannot guarantee the RMS method for spectrum width calculation on the OSA is 100% compliant with the FOTP-127 standard since the equations are written slightly differently.

 

The K parameter in the RMS method algorithm was included to allow more flexibility in the computation method of spectrum width based on the original shape of the signal. For example, a value of 2.355 for K is recommended for the FWHM for a Gaussian shape response. The default value of K is 2.0. If you wish to use the exact same calculation method as the IEC method, please set the K parameter to 1 instead of 2. Please note that there is a typo in the AQ6370C User's Manual Appendix 2. The proper equation, with the K parameter included, can be found in the attached document.

 

This also applies to the following OSA models: