This part of IEC 61290 applies to commercially available optical fibre amplifiers (OFAs) using active fibres containing rare-earth dopants as described in the following. The object of this international standard is to establish uniform requirements for accurate and reliable measurements of the multichannel gain and noise parameters as defined in IEC 61291-4. The test methods described in this standard use small-signal probes to obtain the multichannel gain and noise parameters while one or more lasers set the saturation condition for the OFA. These methods are classified as indirect in that there is not a laser source at each wavelength of the multichannel plan. Multichannel parameters are estimated from the probe data. IEC 61290-10-1 and IEC 61290-10-2 are test methods for measuring noise parameters using pulse techniques. These methods are direct in that the multichannel source is required to have a laser at each wavelength for which multichannel parameters are to be measured. Probe techniques provide clear advantages for measuring multichannel gain characteristics in that a simple source configuration can provide parameters for a wide range of multichannel plans. Either a small-signal laser or a broadband noise source serves as the probe signal, and single or multiple lasers are used to set the OFA saturation condition. Pulse modulation of the saturating sources may optionally be used to measure ASE at or near the saturating laser wavelengths without the contaminating effect of source spontaneous emission. If pulse modulation is not used, the source spontaneous emission must be measured, and its effect removed from the measured result. For a multichannel source with high spontaneous emission or at high total input power, the source noise subtraction method can lead to large uncertainty. The probe techniques described herein are indirect in that laser sources are not required at each channel frequency. A measurement error results from inhomogeneous effects that are DUT dependent. The main source of this error is spectral hole burning (see [1]1 [2] and [4]). The applicability of pulse modulation of the saturating signal(s) and the selection of the modulation rate are dependent on the optical fibre amplifier’s characteristics, specifically its time response. They may be unsuitable for amplifiers with active automatic level control (ALC) or automatic gain control (AGC) circuits. They may also be unsuitable for praseodymiumdoped OFAs that have gain relaxation times that are much faster than erbium-doped designs. For erbium-doped fibre amplifiers (EDFAs), inaccuracy due to modulation is generally small. Refer to IEC 61290-10-2 for a discussion of inaccuracy due to pulse repetition rate. In order to predict multichannel parameters by probe methods it is necessary to properly set the output level of the saturating signal(s) to simulate the saturation effect of a specified multichannel plan. Clause 5 describes a methodology to accomplish this under the assumption of homogeneous behavior within a wavelength region. This methodology has the limitation that the wavelength dependence of any output coupling circuit from the active fibre to the output port is assumed to be zero within defined regions. Parameters measured with the methods described herein include channel gain, channel signal-spontaneous noise figure, and amplified spontaneous emission (ASE). Values marked with(*) indicate preliminary values. Final values are under study.