Optical channel upgradability of multiwavelength erbium-doped fiber amplifier for hybrid digital/analog dense wavelength-division-multiplexing systems

Abstract

We investigate theoretically the impact of optical channel upgradability on the design of erbium-doped fiber amplifier (EDFA), in terms of guard band, channel number and input signal power level for simultaneously amplifying amplitude-modulated vestigial-sideband analog cable television signal and multiple optical digital baseband signals in hybrid dense wavelength-division-multiplexing (H-DWDM) systems. The single-staged forward and backward bidirectional pumping scheme for EDFA without using any inter-staged components is adopted because it is the best amplifier configuration to offer the highest output power with fairly low noise figure and highly satisfied carrier-to-noise ratio performance. In this work, we define the guard band Δλ GB as the channel spacing between the analog channel and the nearest digital channel. We find that various guard bands (Δλ GB =6.45–1.61 nm) do not affect the noise figure (3.36–3.38 dB) and channel gain variation (ΔG D =0.12–0.13 dB) . However, the channel number (10–32, Δλ D =0.8 nm) influences the gain variations (ΔG D =0.12–3.62 dB) evidently. The gain variation of H-DWDM EDFA for a launched 10, 16, 20 and 24 digital channels is 0.12, 0.65, 0.71 and 0.74 dB, respectively, but that for 28 and 32 digital channels is degraded to 2.47 and 3.95 dB, respectively, because the left-most digital channel is very close to the 1530 nm spectrum so as to degrade the gain flattening. This degradation can be improved by shifting the digital channels away from the 1530 nm band.