As there are continuously increasing throughput demands on fiber optical networks, many types of multiplexing systems have become a hot topic for research as there is a need to better utilize the bandwidth resources of the optical fiber and increase spectral efficiency, some of these allow of unique joint Digital Signal Processing. Carrier phase estimation is an important aspect of DSP-based receivers, through carrier phase estimation the effects of laser phase noise are mitigated, the effects of laser phase noise are in general more important as systems become more spectrally efficient. Traditionally carrier and phase recovery is done per channel basis using either blind or data aided methods, however some methods are able to exploit correlation between the channels and other such properties to perform joint carrier and phase recovery.

This topic focuses mainly on joint carrier and phase recovery algorithms and their performance. This topic looks at Frequency Comb-Based Transmission Systems and how in those systems the phase coherence between the lines can be exploited to simplify or increase the performance of digital carrier phase recovery algorithms and comparisons are made between different algorithms and different pilot distributions over the channels.

Papers:

1. Frequency Comb-Based WDM Transmission Systems Enabling Joint Signal Processing, Lars Lundberg et al

2. Joint Carrier Recovery for DSP Complexity Reduction in Frequency Comb-Based Superchannel Transceivers, Lars Lundberg et al

3. Pilot-Aided Joint-Channel Carrier-Phase Estimation in Space-Division Multiplexed Multicore Fiber Transmission, Arni F. Alfredsson et al                

4. Optimization of Pilot-Aided Joint Phase Recovery for Frequency Comb-Based Wideband Transmission, Gabriele Di Rosa et al

Interested student please contact Muhammad Ahmed Leghari for further discussion

Contact: ahmed.leghari@adtran.com

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.