A low-cost technique for broadband gain and noise figure characterization of optical amplifiers using a broadband source and a filter

We report a unique low-cost technique for broadband gain and noise figure characterization of erbium-doped fiber amplifiers using an amplified-spontaneous-emission source and a wavelength filter with multiple steep slopes. Gain and noise figure of the amplifier can be obtained by extracting the slope and intercept of output versus input power spectral density at filter slopes. Based on this technique, we present two methods of gain and noise figure measurements: one by using a fixed filter with multiple steep slopes at the measured wavelengths, and the other using a tunable filter with one or more steep slopes. The required filter depth is about 35 dB. The results obtained over a 20 dB total input power range using both methods are in good agreement with those obtained using conventional spectral-interpolation technique employing multiple DFB lasers at 100 GHz spacing. The discrepancy is within ±0.3 dB in the C-band. This technique can also be used to characterize other types of broadband optical amplifiers, as its accuracy is in principle not affected by the response time of the amplifying medium.