The exponential traffic growth, demand for high speed wireless data communications, as well as incessant deployment of innovative wireless technologies, services, and applications, have put ...considerable pressure on the mobile network operators (MNOs). Consequently, cellular access network performance in terms of capacity, quality of service, and network coverage needs further considerations. In order to address the challenges, MNOs, as well as equipment vendors, have given significant attention to the small-cell schemes based on cloud radio access network (C-RAN). This is due to its beneficial features in terms of performance optimization, cost-effectiveness, easier infrastructure deployment, and network management. Nevertheless, the C-RAN architecture imposes stringent requirements on the fronthaul link for seamless connectivity. Digital radio over fiber-based common public radio interface (CPRI) is the fundamental means of distributing baseband samples in the C-RAN fronthaul. However, optical links which are based on CPRI have bandwidth and flexibility limitations. Therefore, these limitations might constrain or make them impractical for the next generation mobile systems which are envisaged not only to support carrier aggregation and multi-band but also envisioned to integrate technologies like millimeter-wave (mm-wave) and massive multiple-input multiple-output antennas into the base stations. In this paper, we present comprehensive tutorial on technologies, requirements, architectures, challenges, and proffer potential solutions on means of achieving an efficient C-RAN optical fronthaul for the next-generation network such as the fifth generation network and beyond. A number of viable fronthauling technologies such as mm-wave and wireless fidelity are considered and this paper mainly focuses on optical technologies such as optical fiber and free-space optical. We also present feasible means of reducing the system complexity, cost, bandwidth requirement, and latency in the fronthaul. Furthermore, means of achieving the goal of green communication networks through reduction in the power consumption by the system are considered.
Increasing mobile traffic and smart devices require continuous expansion of optical access network capacity and easy optical connectivity for residential, business, and mobile services. A high-speed ...TDM-PON system with high power budget is an attractive solution to accommodate explosive mobile traffic since multiple remote nodes with simple optical power splitters could easily provide optical connections anywhere in an optical distributed network. Thus, both high speed per wavelength and high-power budget are desirable in the TDM-PON system. We demonstrate a TDM-PON system with 50 Gb/s/λ with PAM4 and 35-dB power budget in the entire O-band by simply operating a booster SOA in the saturation region. In addition, a dynamic range of 50 Gb/s PAM4 receiver higher than 15 dB is demonstrated to support loud-soft ratio. We also successfully demonstrate error-free transmission of 50 Gb/s TDM-PON system by utilizing an OLT line-card and an ONU board.
Next generation optical metro networks need to serve heterogeneous access traffic with guaranteed quality of service (QoS) and lower CAPEX and OPEX. In this context, an integrated network ...infrastructure enabling multiple services access and network slicing is necessary. In this paper, we investigate recent research efforts on network slicing in optical metro networks, the MTN and M-OTN. These technologies have limitations in flexible network resource slicing and efficient bandwidth utilization. Therefore, we propose a new all optical metro network SiMON for achieving flexibility in network slicing and efficiency in bandwidth utilization. In addition, we theoretically investigate the SiMON in achieving end-to-end deterministic latency. A jitter reduction method for SiMON network slices is proposed by formulating the latency components of its communication paths. Theoretical analysis and numerical studies support that the SiMON outperforms the MTN in flexible network resource slicing, and achieves higher bandwidth efficiency than the M-OTN. Moreover, an experimental setup of the SiMON system has been implemented by FPGA. Experimental results show that the SiMON achieves 96.5% of bandwidth utilization with dynamic adjustable network slicing. Below 2<inline-formula><tex-math notation="LaTeX">\mu s</tex-math></inline-formula> jitter is achieved in the SiMON network slices under burst traffic, and below 0.2<inline-formula><tex-math notation="LaTeX">\mu s</tex-math></inline-formula> jitter has been achieved for constant frame rate traffic with short frame lengths.
As coverage increases or network topology becomes more complex, the optical path loss difference between any two access points in tree-like passive optical networks (PON) is uneven, causing service ...fairness problems at the physical layer. The service fairness of the far-near user access in 200-Gbps coherent PON with various user cases is discussed in this work. A fairness allocation mechanism based on time division multiplexing (TDM) non-orthogonal multiple access (NOMA) in the time-power domain is proposed theoretically to provide fair transmission between the arbitrary two optical network units (ONUs) with the best and the worst performance within single timeslots. Then, a series of subsequent experiments are performed with different path loss and split ratios (SR) to prove the effectiveness and practicality of the proposed NOMA scheme, totally including 12 subcases. Any sub-experiment proves that by optimizing power allocation, the signal-to-interference noise ratio (SINR) or bit-error rate (BER) on the physical layer can be approximated to the same value. The Jain's fairness index at a fixed and flexible hard-decision forward error correction (HD-FEC) standard, and modified fairness index are used to evaluate service fairness in different cases. This TDM-NOMA scheme may address the service fairness issue in next-generation coherent PON with wide coverage.
Coherent Access: A Review Shahpari, Ali; Ferreira, Ricardo M.; Luis, Ruben S. ...
Journal of lightwave technology,
2017-Feb.15,-15, 2017-2-15, Volume:
35, Issue:
4
Journal Article
Peer reviewed
Open access
In this paper, we will address the benefits of the coherent detection in future optical access networks. The scarcity of the optical spectrum, the required flexibility, and constant evolution of ...requirements highlight the effectiveness of coherent techniques toward the future passive optical networks (PON). A set of architectures for coherent optical access networks will be presented and the key attributes of each scenario will be investigated. In addition, as a basis to decrease the cost of the local oscillator (LO) at customer side, we experimentally investigate the possibility of using a low-cost laser as LO with real-time detection of a Nyquist-shaped differential quadrature phase-shift keying (DQPSK) signal using simple 8-bit digital signal processing (DSP) on a field-programmable gate array. Moreover, we experimentally derive a set of optimized parameters and their impact on the network operation for coherent ultradense wavelength-division multiplexing (UDWDM) systems. The balance between the number of channels, power budget, and dynamic power range will be evaluated. Furthermore, we demonstrate a reconfigurable real-time receiver DSP for future flexible UDWDM-PON systems applying the DQPSK and D8PSK modulation formats. By reviewing some of the motivations for this technology, such as flexibility, spectral efficiency, as well as compatibility with software-defined networking, we show that this technology is approaching the required maturity.
This special issue includes extensions of optical networking papers that were presented at the European Conference on Optical Communication (ECOC) 2023, held 1–5 October 2023 in Glasgow, Scotland.
Excellence in transmission can be assessed in optical transport networks before providing any additional connections or upgrading the connections. Generally, the Physical Layer Model (PLM) is used to ...assess the transmission quality which has high probability in uncertainty and inaccuracy due to the circumstances of physical layer. The network efficiency is directly proportional to the margins. If the margins getting increases in the PLM, the efficiency of the network decreases. Maintaining the excellence in transmission is the biggest challenge when the margins getting increased. Other significant factors for excellence in transmission is scalable, minimum latency with maximum speed and energy efficient. Photonic switching is a hopeful solution for handling these challenges. Machine learning technique is proposed to assess the excellence of transmission and flow detection. ML-E and Precedence based scheduling algorithms are proposed for excellence of transmission and flow detection respectively. The proposed techniques justify variations, uncertainties in kits like fiber dilution, dispersion and optimizes PSON (packet switched optical network). Simulation results are demonstrated and the proposed work results indicates that it can outperform a benchmark in all aspects.
•A two-dimensional fragmentation-aware model is formulated and analyzed.•Two VONE algorithms are proposed, named Two-Dimensional Fragmentation Aware (TDFA) VONE algorithm, and Fragmentation and ...Continuity Aware (FCA) VONE algorithm.•Simulation results show that the proposed algorithms perform better than baseline algorithm in blocking probability and spectrum utilization issues.
Based on the concept of infrastructure as a service, optical network virtualization can improve the efficiency of network infrastructure by sharing the physical substrate network among different tenants and applications. The most important issue of optical network virtualization is how to handle the virtual optical network embedding (VONE) process, especially with the coexistence of the requests those can be reserved in advance (AR) and those require immediate reservation (IR). To address this issue, we investigate the time and spectrum fragmentation during the VONE process, which undermines the embedding success rate in elastic optical networks. A two-dimensional fragmentation measurement is first proposed to evaluate the resource state. Then we design a Two-Dimensional Fragmentation Aware (TDFA) VONE algorithm, and a Fragmentation and Continuity Aware (FCA) VONE algorithm, which decreases the two-dimensional fragmentation in the VONE process. Simulation results show that the proposed algorithms perform better than the baseline algorithm in blocking probability and spectrum utilization issues.
This letter proposes and experimentally demonstrates a novel physical layer security method based on a piecewise chaotic permutation for orthogonal frequency division multiplexing (OFDM) passive ...optical networks. The piecewise parabolic chaotic map is adopted to generate chaotic permutation vectors, which enhance the physical layer security with a simple structure. An experiment with a 26.33-Gb/s encrypted optical OFDM signal is performed to demonstrate the proposed method. The results show good resistance against illegal optical network units and indicate that our method has the potential for use in secure optical access networks.
