Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Radio over fiber plays a prominent role in the realization of next generation integrated Optical -Wireless Networks to distribute mobile broadband signals effectively to meet the increasing demand of multimedia services with guaranteed quality of services. In this paper the signal transport schemes of analog and digitized Radio over fiber systems with relevance to cellular communication and the comparison of different Radio over fiber systems with their merits and demerits is explored. Further, review of existing different types of multioperator multiservice architectures to realize high performance Radio over fiber based fronthaul architectures also presented in detail. © 2020 Walter de Gruyter GmbH, Berlin/Boston.

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Department of Communication Engineering

School of Electronics Engineering

Vellore Campus

Journal of Optical Communications

Radio over fiber based signal transport schemes for emerging mobile fronthaul networks - A review

An adaptive impairments assessment is necessary to evaluate the impact of various linear and nonlinear effects in future generation cognitive optical transport links. In this paper, an Adaptive Fiber Impairment Mitigation (AFIM) algorithm is proposed to identify a suitable mitigation scheme for the cognitive environment. The AFIM algorithm will assess fiber impairments and adaptively select a suitable mitigation scheme with minimum complexity based on the present network conditions and user performance target. The performance of AFIM algorithm is compared with Fixed Fiber Impairment Mitigation approach in terms of outage probability and outage capacity analysis. An Orthogonal Frequency Division Multiplexing based Mode Division Multiplexing system with Few Mode Fiber (FMF) is suggested as a solution to increase the nonlinearity threshold limit of the system. The L 2-by-3 nonlinear transform based Peak to Average Power Ratio reduction technique is implemented to mitigate fiber nonlinear effects in FMF based backbone and backhaul links. The performance analysis of the FMF system has been evaluated and compared with that of Single Mode Fiber system. The proposed analytical model and mitigation schemes are integrated with the AFIM algorithm to realize the cognitive optical network. Further, the result shows that AFIM algorithm enhances the system capacity by more than 6-folds at an outage probability of 0.5 and reduces the outage probability to 0.6 at the capacity range of 20 Gbps. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Optical and Quantum Electronics

Fiber impairments mitigation in OFDM based cognitive optical networks

AbstractOrthogonal frequency division multiplexing (OFDM) is a special form of multicarrier (MC) modulation technique which is adopted in 4G mobile communication systems. The combination of OFDM with passive optical network (PON) architecture is highly desirable for design of flexible and energy efficient backhaul and backbone networks for 5G systems. An intensive mathematical model for linewidth analysis in OFDM based backhaul (BH) and backbone (BB) systems is proposed. The proposed mathematical model includes fiber dispersion, fiber nonlinear effects, amplified spontaneous emission (ASE) noise, transmitter and receiver noises. The impact of laser linewidth in the developed analytical model is analysed in terms phase rotation term (PRT) and inter-carrier interference (ICI) power. Further, the BER performance of the DD-OFDM system as a function of laser linewidth is also presented. The results of the analytical model solved using MATLAB is compared with virtual photonics integrated (VPI) based simulation results. The results of our proposed model suggest that DD-OFDM would perform better for lower linewidth in dispersion uncompensated (DUC) links and it has no impact on the dispersion compensated (DC) links for BB networks. In BH networks, the system performs better for lower linewidth in both DUC and DC links.

Analysis of Laser Linewidth on the Performance of Direct Detection OFDM Based Backhaul and Backbone Networks

Fiber nonlinearity is seen as a capacity limiting factor in OFDM based dispersion managed links since the Four Wave Mixing effects become enhanced due to the high PAPR. In this paper, the authors have compared the linear and nonlinear PAPR reduction techniques for fiber nonlinearity mitigation in OFDM based dispersion managed links. In the existing optical systems, linear transform techniques such as SLM and PTS have been implemented to reduce nonlinear effects. In the proposed study, superior performance of the L2-by-3 nonlinear transform technique is demonstrated for PAPR reduction to mitigate fiber nonlinearities. The performance evaluation is carried out by interfacing multiple simulators. The results of both linear and nonlinear transform techniques have been compared and the results show that nonlinear transform technique outperforms the linear transform in terms of nonlinearity mitigation and improved BER performance. © 2016 Elsevier B.V.

Optics Communications

Improved fiber nonlinearity mitigation in dispersion managed optical OFDM links

Energy-efficient system design with controlled levels of electromagnetic pollution, without compromising on the user quality of experience and operator revenue, are essential considerations in the design of next-generation wireless communication networks. Integration of multiple services and multiple operator transmissions onto a common shared infrastructure is the solution forward to satisfy the contradictory subscriber and operator requirements and also to derive a future-proof fronthaul to support new techniques like opportunistic, co-operative and cognitive communications. This paper reports the link budget analysis, energy efficiency estimation and electromagnetic radiation calculation for a Multi-Operator Multi-Service Analog Radio over Fiber fronthaul for a small cell configuration. The BER analysis and the link budget analysis are presented for the central base station to remote antenna unit (RAU) link as well as the RAU to user equipment link. The estimated minimum transmission power sufficient to establish and maintain a quality connection suggests the possibility of eliminating the energy consuming power amplifiers in the transceivers and also achieve a reduced electromagnetic pollution in the environment. © 2017, Springer Science+Business Media New York.

Photonic Network Communications

Energy and electromagnetic pollution considerations in ARoF-based multi-operator multi-service systems

The past decade has seen the phenomenal usage of orthogonal frequency division multiplexing (OFDM) in the wired as well as wireless communication domains, and it is also proposed in the literature as a future proof technique for the implementation of flexible resource allocation in cognitive optical networks. Fiber impairment assessment and adaptive compensation becomes critical in such implementations. A comprehensive analytical model for impairments in OFDM-based fiber links is developed. The proposed model includes the combined impact of laser phase fluctuations, fiber dispersion, self phase modulation, cross phase modulation, four-wave mixing, the nonlinear phase noise due to the interaction of amplified spontaneous emission with fiber nonlinearities, and the photodetector noises. The bit error rate expression for the proposed model is derived based on error vector magnitude estimation. The performance analysis of the proposed model is presented and compared for dispersion compensated and uncompensated backbone/backhaul links. The results suggest that OFDM would perform better for uncompensated links than the compensated links due to the negligible FWM effects and there is a need for flexible compensation. The proposed model can be employed in cognitive optical networks for accurate assessment of fiber-related impairments. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).