IEC 60793-1-61: 2017 establishes uniform requirements for measuring the polarization crosstalk of polarization-maintaining (PM) fibres . This document gives two methods for measuring the polarization crosstalk of PM fibres. Method A is the power ratio method, which uses the maximum and minimum values of output power at a specified wavelength, and Method B is the in-line method, which uses an analysis of the Poincaré sphere. Details of each method are described in Clause 6. Crosstalk values obtained by Methods A and B are based on different definitions. The crosstalk measured by Method A is defined as an "averaged" value over a measured waveleng t h range. In contrast, the crosstalk value obtained from Method B shows the "worst case" crosstalk value. Keywords: polarization-maintaining (PM) fibres