Frequency-swept pump based SBS filter with an ultra-flat passband, very steep edges and flexible tunability with very high resolution is attractive in MPF. But the sweep period has not been studied yet, while it is a key parameter to realize flat spectral response and acceptable signal performance. Therefore, the optimal frequency sweep period should be accurately studied and it has great guiding significance for practical application of the SBS filter based on frequency-swept pump.

In this paper, we realize a series of 2-GHz wide rectangular optical filters based on the stimulated Brillouin scattering (SBS) effect in optical fiber with a frequency-swept pump and gain feedback compensation scheme. The frequency sweep pump period is a key parameter to achieve acceptable signal performance in the frequency-swept pump based SBS gain filter. We evaluate the system performance of the signal, which is fed into the SBS filter based on frequency-swept pump with different sweep periods ranging from 0.1  to 100 μs, in terms of eye diagrams and bit-error rate (BER) after 12.5  and 25 km of fiber transmission, respectively. Both 500-Mb/s and 1-Gb/s on-off-keying (OOK) signals are used for real-time signal quality evaluation. The optimum eye diagram and BER performance are achieved after 25 km transmission under a 1 μs frequency sweep pump period, as well as after 12.5-km transmission under a 0.5 μs sweep period. The experimental results show that the optimal frequency sweep pump period is always around 1/120 of the signal propagation time in the fiber for different transmission length, providing a guideline on the design of the frequency-swept pump based SBS gain filter and its applications.