BS EN 61280-2-9:2003 Fibre optic communication subsystem basic test procedures - Test procedures for digital systems - Optical signal-to-noise ratio measurement for dense wavelength-division multiplexed systems
2009BS EN 61280-2-9:2009 Fibre optic communication subsystem test procedures — Part 2-9: Digital systems — Optical signal-to-noise ratio measurement for dense wavelength-division multiplexed systems
2003BS EN 61280-2-9:2002 Fibre optic communication subsystem basic test procedures - Test procedures for digital systems - Optical signal-to-noise ratio measurement for dense wavelength-division multiplexed systems