Optical communication systems are the backbone of current communication network as they allow fast and reliable information exchange. However, the advent of new generation applications and services require an ever increasing demand for higher capacity, lower cost, and lower energy consumption. According to discussions in [1], because of the difference in the growth rates between the fiber capacity and the traffic demand, there is expected to be a capacity shortage within the next decade. 

Among several options for increasing the capacity of installed optical fibers, exploiting new wavelength bands appears to be a promising and economical solution. Extending the transmission bandwidth from conventional band (C-band) to multi-band (MB), researchers are aiming to transmit information over the entire single mode fiber spectrum. This will increase the optical capacity and thus postpone the need to deploy new fibers. 

The challenges for the realization of such multiband networks lie both in the development of key components – as well as in the modelling of the physical and network layers. 

The modelling of UWB systems enables to optimize the design of a given optical communication link to achieve maximum throughput, including finding optimal signal launch power, data rates, modulation formats, number of channels, and, in the case of hybrid-amplified links, also the Raman amplifier’s pump powers and frequencies. The Gaussian noise closed-form model (GN-CFM) expressions [2] have increasingly been used for rapid evaluation of nonlinear interference (NLI) noise, which, together with amplified spontaneous emission (ASE) noise and transceiver noise, define the received SNR. GN-CFM, in turn, can be used to optimize optical link parameters.

The main paper of the seminar work [3] uses the GN model discussed in [4] [5] to calculate optimum launch power per channel with the presence of Raman amplification. The student’s task is to deliver the steps they used in paper [3] as well as to understand the mechanics of a hybrid amplification schemes and GN model defined in [4] [5].  

[1] Essiambre, René-Jean and Robert W. Tkach. “Capacity Trends and Limits of Optical Communication Networks.” Proceedings of the IEEE 100 (2012): 1035-1055.

[2] D. Semrau, R. I. Killey, and P. Bayvel, “A Closed-Form Approximation of the Gaussian Noise Model in the Presence of Inter-Channel Stimulated Raman Scattering,” Journal of Lightwave Technology, vol. 37, pp. 1924–1936, May 2019.

[3] H. Buglia, E. Sillekens, L. Galdino, R. I. Killey, and P. Bayvel, "Impact of launch power optimisation in hybrid-amplified links," 2024. 

[4]H. Buglia, E. Sillekens, L. Galdino, R. I. Killey, and P. Bayvel, “Throughput maximisation in ultra-wideband hybrid-amplified links”, in Optical Fiber Communications Conference, 2024, Tu3H.5.

[5]H. Buglia, M. Jarmolovicius, L. Galdino, R. I. Killey, ? and P. Bayvel, “A closed-form expression for the Gaussian noise model in the presence of Raman amplification”, Journal of Lightwave Technology, vol. 42, no. 2, pp. 636–648, 2024. DOI: 10.1109/JLT.2023.3315127.