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 80 km (100 km) 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.

中文翻译：

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相干 DWDM 系统中的联合信道功率和放大器增益优化

摘要 本文对相干密集波分复用(DWDM)光纤通信系统的信道功率和放大器增益进行了联合优化。目标是最大化信噪比 (SNR) 的最小裕度。所提出的优化问题是非线性和非凸的，其中光纤的通道内和通道间非线性干扰（NLI）噪声是通过使用所谓的高斯噪声（GN）模型来估计的。此外，还模拟了光放大器的噪声和其他实际方面，例如输出功率饱和、最大增益限制、增益倾斜和纹波以及噪声系数非平坦度。最后，我们表明这个问题可以重新表述为凸优化。我们的结果表明，在跨距长度为 80 公里（100 公里）的 5 跨距光纤链路中联合功率和放大器增益优化比传统的功率优化方法高 1 dB (0.47 dB) SNR，其中放大器增益固定且等于跨度损失。通过考虑跨距长度为 80 公里的 8 跨距光纤链路中的增益纹波和倾斜，我们观察到，我们的算法的信噪比分别比放大器增益均衡和非均衡的替代功率优化方法高 0.72 dB 和 1.86 dB。