IEC 62149-3:2014 covers the performance specification for optical modulators monolithically integrated with laser diodes for 2,5 Gbit/s to 40 Gbit/s multi-channel fibre optic transmission systems. This performance standard contains a definition of the product performance requirements together with a series of sets of tests and measurements with clearly defined conditions, severities and pass/fail criteria. The tests are intended to be run as an initial design verification to prove any product's ability to satisfy the performance standard's requirements. This standard is only applicable for on-off keying format. This second edition cancels and replaces the first edition published in 2004 and constitutes a technical revision. The significant technical change with respect to the previous edition is as follows: The performance standards covered by this standard are now extended to a 40 Gb/s-class system from their original 2,5 Gb/s. Keywords: optical modulators monolithically integrated, laser diodes, 2,5 Gbit/s to 40 Gbit/s multi-channel fibre optic transmission systems