Amendment 1 to Recommendation ITU-T G.650.1 (2010) is aimed to provide measurement procedures for coherent multi-path interference (MPI) in a short optical fibre cables (jumpers). An improvement in bending-loss in a single-mode fibre affects not only the fundamental mode but may also influence the higher order modes. This may change the cut-off wavelength mechanism. In this case, the single-mode operability of an optical fibre can be investigated by evaluating the MPI characteristics.
Appendix IV introduces three kinds of test methods:
- ECL/PM (External Cavity Laser/Power Meter) method,
- LED/OSA (Light Emitting Diode/Optical Spectrum Analyser) method,
- FS (Fibre Stretching) method.
A new note is added in the bottom of clause 3.6.1 in order to provide reference to MPI and new Appendix IV.