Domestic and foreign technical staff has done a lot of researchon Mode field diameter measurementmore than 20 years ago.A lot of research papershave been published.Many standard organizations have published the relevant standards.Measurement of mode field diameter of effective international and domestic standards are based on PetermannⅡdefinition directly or indirectly.IEC released IEC 60793-1- 45:2001 in 2001

then in 2002 issued a corrigendum.ITU-T released 3 versions of the standard about mode field diameter measurement. The newest ITU-T standard is ITU-T G.650.1 2010.China GB latest version is GB/T 15972.45-2008.The authorfoundmultiple formulas inconsistent on these standards after intensive research.Thoseformulas were derived from the definition of mode field diameter in the paper.The correctness was verified from the dimensional angle

and the internal calculation method of the instruments widely used. Ultimately the paper concluded that the standards of ITU-T and IEC on mode field diameterhave errors in the calculation formula.And suggestedthe relevant international standardorganization discuss andcorrect those mistakes as soon as possible.