Novel high gain and wide band hybrid amplifier designed with a combination of an EYDFA and a discrete Raman amplifier

Abstract

In an optical communication network, over a broad range of spectrum, the gain of the amplifier must be flattened in order to increase the bandwidth utilization of the network. Here we analyze a novel approach of designing a hybrid amplifier with a combination of a single mode (SM) erbium ytterbium co-doped fiber amplifier (EYDFA) and a discrete Raman amplifier (RA) to flatten its gain over the optical spectrum of the C and L bands, which is about 90 nm of spectral width. This hybrid amplifier requires only 5 optimal pump signals in RA, and there is no need of any gain flattening filter in it. The performance of this simulated hybrid amplifier is analyzed with the help of 110*40 Gb/s non-return-to-zero dense wavelength division multiplexed (DWDM) signals as the input. They cover the entire C and L bands, and the presence of dense channels also ensures the accurate measurement of important parameters of the hybrid amplifier such as maximum gain, gain ripple, noise figure, and optical signal-to-noise ratio (OSNR). The five pump signals of RA are spaced equally, unequally, and semi-unequally in order to attain the objective. The least gain ripple is obtained for semi-unequal pump frequency spacing. The length of the SM EYDFA, the RA, the power of the pump signals, and the power of the DWDM input signals are optimized through the multi-parameter multi-target optimization tool of the Optisystem simulation software. The five pumping signals of RA are tested with forward, backward, and both forward and backward schemes in order to analyze the performance of the hybrid amplifier. Out of all the experiments, the SM EYDFA + RA forward pumping scheme offers superior performances such as maximum gain of 31.2 dB, very low gain ripple of 2.09 dB (6.7% of the maximum gain), maximum noise figure of 4.68 dB, and maximum OSNR of 34.23 dB. This new design of hybrid amplifier with superior gain flattening performance will be very much useful for cable television or community antenna television (CATV) and telecommunication networks.