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This part of IEC 61290 applies to optical fibre amplifiers (OFA) using active fibres, containing rare-earth dopants, currently commercially available. The object of this International Standard is to establish uniform requirements for accurate and reliable measurements of the signal-spontaneous noise figure as defined in 3.1.18 of IEC 61291-1. The test method independently detects amplified signal power and amplified spontaneous emission (ASE) power by launching optical pulses into the OFA under test. The ASE level is measured by synchronously measuring the power on an optical spectrum analyzer (OSA) during the optical pulse off period. The average optical signal level is measured bu random sampling in the OSA. Such measurement is possible because the gain response of the rare-earth doped OFA is relatively slow, particular in Er-doped OFA. However, since the OFA gain dynamics vary with amplifier types, operating conditions, and control schemes, the gain dynamics should be carefully considered when applying the present test method to various OFA. The manufacturer of the OFA should present data validating the required modulation frequency to limit the error to <1 dB. The measurements for obtaining this information are described in annex B. Two alternatives for determining the signal-spontaneous noise figure are specified; namely, the optical switching technique and the gated-OSA technique. The procedurer described in this standard is the gated-OSA technique. The optical switching technique is described in IEC 61290-10-1.