This part of IEC 61290 applies to all commercially available optical amplifiers (OAs) and optically amplified subsystems. It applies to OAs using optically pumped fibres (OFAs based on either rare-earth doped fibres or on the Raman effect), semiconductor optical amplifiers (SOAs) and waveguides (POWA). The object of this standard is to establish uniform requirements for accurate and reliable measurements, by means of the interpolated source subtraction method using an optical spectrum analyzer. The following OA parameters, as defined in Clause 3 of IEC 61291-1, are determined: • channel gain, and • channel signal-spontaneous noise figure. This method is called interpolated source subtraction (ISS) because the amplified spontaneous emission (ASE) at each channel is obtained by interpolating from measurements at a small wavelength offset around each channel. To minimize the effect of source spontaneous emission, the effect of source noise is subtracted from the measured noise. The accuracy of the ISS technique degrades at high input power level due to the spontaneous emission from the laser source(s). Annex A provides guidance on the limits of this technique for high input power. An additional source of inaccuracy is due to interpolation error. Annex A provides guidance on the magnitude of interpolation error for a typical amplifier ASE versus wavelength characteristic. NOTE 1 All numerical values followed by (‡) are suggested values for which the measurement is assured. Other values may be acceptable but should be verified. NOTE 2 General aspects of noise figure test methods are reported in IEC 61290-3.