Joint channel power and amplifier gain optimization in coherent DWDM systems

Abstract In this paper, the channel power and amplifier gain of coherent dense wavelength division multiplexing (DWDM) fiber-optic communication systems are jointly optimized. The objective is to maximize the minimum margin of signal to noise ratio (SNR). The presented optimization problem is non-linear and non-convex, in which the intra- and inter-channel nonlinear interference (NLI) noise of fiber is estimated by using the so-called Gaussian noise (GN) model. Furthermore, the noise and other practical aspects of optical amplifiers such as output power saturation, maximum gain limitation, gain tilt and ripple, and noise figure non-flatness are modeled. Finally, we show that this problem can be reformulated as a convex optimization. Our results reveal that joint power and amplifier gain optimization in a 5-span fiber link with span length of 80km (100km) leads to 1 dB (0.47 dB) higher SNR than the conventional power optimization method in which amplifier gain is fixed and equals to span loss. By considering gain ripple and tilt in a 8-span fiber link with span length of 80 km, we observed that our algorithm has 0.72 dB and 1.86 dB higher SNR than the alternative power optimization methods in which amplifier gain is equalized and unequalized, respectively.