This part of IEC 60793 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 wavelength range. In contrast, the crosstalk value obtained from Method B shows the "worst case" crosstalk value.dition 1.0 2017-02 INTERNATIONAL STANDARD Optical fibres – Part 1-61: Measurement methods and test procedures – Polarization crosstalk IEC 60793-1-61:2017-02(en) THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright ？ 2017 IEC, Geneva, Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mecha