Fiber Infrastructure Research Articles

Full daylight quantum-key-distribution at 1550 nm enabled by integrated silicon photonics

The future envisaged global-scale quantum-communication network will comprise various nodes interconnected via optical fibers or free-space channels, depending on the link distance. The free-space segment of such a network should guarantee certain key requirements, such as daytime operation and the compatibility with the complementary telecom-based fiber infrastructure. In addition, space-to-ground links will require the capability of designing light and compact quantum devices to be placed in orbit. For these reasons, investigating available solutions matching all the above requirements is still necessary. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145 m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps during a whole sunny day (from 11:00 to 20:00). The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource to design quantum optical payloads for future satellite missions.

Distributed abstraction and verification of an installed optical fibre network

The management of wavelength routed optical mesh networks is complex with many potential light path routes and numerous physical layer impairments to transmission performance. This complexity can be reduced by applying the ideas of abstraction from computer science where different equipment is described in the same basic terms. The noise-to-signal ratio can be used as a metric to describe the quality of transmission performance of a signal propagated through a network element and accumulates additively through a sequence of such elements allowing the estimation of end-to-end performance. This study aims to explore the robustness of the noise-to-signal ratio metric in an installed fibre infrastructure. We show that the abstracted noise-to-signal ratio is independent of the observers and their location. We confirm that the abstracted noise-to-signal ratio can reasonably predict the performance of light-paths subsequently set in our network. Having a robust network element abstraction that can be incorporated into routeing engines allows the network management controller to make decisions on the most effective way to use the network resources in terms of the routeing and data coding format.

5G Network Deployment in Nigeria: Key Challenges and The Way Forward

Many countries are faced with different challenges in the deployment of 5G mobile wireless communication technology. These challenges have delayed the smooth rollout of this technology in these countries. Nigeria has its own issues that have hindered the implementation of this technology in the country. This paper discusses these challenges and suggestions made on what to do for the implementation of 5G technology. A survey was done by visiting and obtaining reports from two major players in the industry as well as understudying actions taken by other nations in tackling similar problems related to 5G network implementation. Based on the information gathered both from the industry and related literature some useful suggestions such as improved fiber infrastructure and relaxing regulatory barriers to encourage investors were made as a way forward for the full implementation and operation of the 5G technology in Nigeria.

5G Network Deployment in Nigeria: Key Challenges and The Way Forward

Many countries are faced with different challenges in the deployment of 5G mobile wireless communication technology. These challenges have delayed the smooth rollout of this technology in these countries. Nigeria has its own issues that have hindered the implementation of this technology in the country. This paper discusses these challenges and suggestions made on what to do for the implementation of 5G technology. A survey was done by visiting and obtaining reports from two major players in the industry as well as understudying actions taken by other nations in tackling similar problems related to 5G network implementation. Based on the information gathered both from the industry and related literature some useful suggestions such as improved fiber infrastructure and relaxing regulatory barriers to encourage investors were made as a way forward for the full implementation and operation of the 5G technology in Nigeria.

A Timing, Trigger, and Control System With Picosecond Precision Based on 10 Gbit/s Passive Optical Networks for High-Energy Physics

The Large Hadron Collider (LHC) experiments will have their timing, trigger, and control (TTC) system upgraded as a consequence of the need for higher bandwidth and components which are obsolete. In this article, we present a TTC based on passive optical networks (PONs). TTC-PON is a point-to-multipoint bidirectional TTC system based on the 10 Gbit/s International Telecommunications Union (ITU) XG-PON technology and modern field-programmable gate array (FPGA) devices. Each master can handle up to 64 slaves through a fully passive network, delivering a fixed-phase recovered clock to all the destinations with less than 5-ps jitter. TTC-PON pushes the limits of the PON technology by exploiting cutting-edge custom protocols on top of the commercially available XG-PON optical modules. It can potentially reuse the current optical fiber infrastructure already installed in the experiments and allows for high flexibility in terms of partitioning, which can ease future upgrades of the TTC network. The system features a picosecond-level on-the-fly phase monitoring for each slave's recovered clock by exploiting the bidirectionality of the network. In addition, a full set of link-quality monitoring tools was developed, allowing real-time performance monitoring. An overview of the tailored protocols will be given together with the details on the system implementation, operation, and performance. A discussion on the characterization campaign of more than 1000 optical modules delivered to the first implementation of the TTC-PON system will be drawn.

Heterogeneous Optical Access Networks: Enabling Low-Latency 5G Services With a Silicon Photonic Smart Edge

In the 5G era, optical fronthaul is a major challenge in meeting growing demand. Edge computation and coordinated multipoint for 5G have stringent requirements for high throughput and low latency, either in single-wavelength or wavelength-division-multiplexing fronthaul. We propose a new silicon photonic solution to deliver 5G services on existing optical access networks with colorless optical network units, such as passive optical networks. The newly added 5G services form a heterogeneous optical access network. Using the existing fiber infrastructure, broadband services coexist with new 5G signals that can densify 5G coverage. The proposed scheme is both wavelength-selective (in the distribution network) and colorless (at the end user site). We use silicon microring modulators to create subcarriers slaved from the broadband service distributed carrier; additional microring modulators generate 5G signals exploiting those subcarriers. We experimentally validated the successful coexistence of 5G signals (various formats) with a broadband signal (various formats).

Bidirectional single-fiber filterless optical networks: modeling and experimental assessment

This paper proposes, designs, and validates a filterless metro network employing bidirectional transmission over a single fiber. Transmission impairments, dominated by cross talk, are specifically estimated leveraging on what we believe to be novel closed-form expressions to determine optical reach, launch power, and number of supported cascaded nodes. Results show that extremely good transmission performance can be achieved and further improved when misalignment in spectrum allocation is configured among the two counter-propagating directions. This confirms that filterless metro networks employing bidirectional transmission over a single fiber represent an extremely attractive solution, particularly in the case of scarce fiber availability and when regulatory aspects impose a rent for any occupied fiber infrastructure.

Vibration Sensing for Deployed Metropolitan Fiber Infrastructure

The optical fiber deployed in the metropolitan infrastructure carrying high-speed WDM traffic data is used also for network surveillance, identifying and localizing the onset of vibrations and dynamic stress events, potentially dangerous for the integrity of the fiber telecom asset. A coherent approach is adopted in a counter-propagating interferometer to develop a sensing system exploiting the ring layout of the metro network. With respect to usual dual Mach-Zehnder interferometric sensors, where typically the reference arm is kept isolated, in our arrangement we use as reference arm a fiber inside the same deployed cable, minimizing the impact of the city strong environmental noise. Preliminary assessments of the proposed sensing solution have been experimented in a metro ring of 32-km standard single-mode fiber deployed in the city of Turin, Italy, devoted to telecom applications. The sensor is demonstrated to operate preserving the coexistence with the high-speed WDM telecom traffic. With respect to complex and expensive sensing solutions based on pulsed phase-OTDR techniques, in the present case continuous-wave counter-propagating optical signals are exploited and the spatial resolution in dynamic event localization depends only on the receiver sampling rate: in our implementation, by adopting off-the shelf low-cost commercial 20 MS/s sampling boards, 10-meter spatial resolution is experimentally achieved. The proposed sensing solution provides significant added value to the deployed metro fiber infrastructure and the same interferometric approach based on the counter-propagating layout can be easily exploited in metro networks even in case of presence of optical nodes equipped with reconfigurable optical add-drop multiplexers useful for WDM traffic routing.

Demonstration of Software Defined Network Services Utilizing Quantum Key Distribution Fully Integrated with Standard Telecommunication Network

We present a demonstration of software defined networking (SDN) services utilizing quantum key distribution (QKD) technology, fully integrated with standard telecommunication network connecting production facilities of Telefonica in Madrid. All communications “co-propagate” over the same fiber infrastructure.

A geospatial approach for telematics analysis: case study of Misri Shah telephone exchange service coverage area DHA phase-VI, Karachi, Pakistan

The impact of rapid re-structuring of telecommunication industry from conventional land lines to cellular networks and relatively fast optic fiber infrastructure, effective and timely analysis about telecommunication facilities based upon accurate demand/supply estimation are now telecom industry’s utmost priorities. This paper is about telecommunication exchange level study in Karachi; which is quite timely addressed and important in comprehending the spatial coverage of telecom industry, which is progressing very well and transformed Pakistan among top countries in the utilization of this service industry. Advancement in telecom networks, technological development, immense competition, and consumer churn has attracted telecom operators to analyze existing network infrastructure and operate with systematical approaches. This paper examines the role of applied geoinformatics for telecommunication industry at exchange level, which provides an easy-to-use methodology for telematics analytics, network expansion, and consumer management in a highly cost-effective manner. The study reveals significant contribution to telecom network operation and modeling, and analyzing telecommunication network through various methods, such as GIS geodatabase modeling, demand and supply analysis, outside plan analysis, and business analysis, finally offers solution for network planning and design. Furthermore, this study identifies network gapes, discrepancies among system modules, identify hotspots, highlight commercial hubs, and finally provide developed geospatial environment at single platform for comprehensive telecom network and consumer analysis.

Australia’s fixed broadband deficit

Australia’s fixed broadband services performance and takeup is continuing to fall behind other comparable countries in international benchmarks. This is despite broadband being a hot topic of debate at three Federal Elections and the creation of a new broadband utility company by the Australian Government. The recent change of government, in 2013, prompted reviews into the structure of Australia’s fixed telecommunications market. A move away from utility style broadband to infrastructure competition has been recommended but the Australian Government has not embraced such a move, preferring instead to keep the utility structure for fixed broadband. While the new Coalition Government is investing in more fibre infrastructure as part of its Multi Technology Mix, there is no commitment to build a ‘deep fibre’ network that would have ‘natural monopoly’ characteristics. Competition from new technologies, wireless and fixed, may limit the financial viability of the utility broadband provider. Indecision about the structure of Australia’s broadband market is likely to continue to retard medium to long term investment in the fibre infrastructure needed to improve Australia’s broadband rankings against its international peers.

Modeling and mitigation of fiber nonlinearity in wideband optical signal transmission [Invited

The adoption of open optical networks (OONs) requires the development of open and effective network planning tools, enabling the use of multi-vendor or white-box transport solutions. Such tools for studying and planning optical networks must be able to take into account the physical layer impairments, including fiber nonlinearity. The use of wideband wavelength division multiplexing in OONs, with channel frequencies extending across the short, conventional, and long bands and beyond, offers a pathway to increasing data rates through the installed fiber infrastructure. However, achievable information rates are limited by the resulting signal distortion due to fiber nonlinearity as signal bandwidths are increased, in particular, inter-channel stimulated Raman scattering (ISRS). In this paper, we describe the nonlinear effects observed in wideband transmission systems, and review recently developed analytical tools, based on the Gaussian noise (GN) model of nonlinear interference with the inclusion of ISRS. Using the ISRS GN model, we assess the impact of fiber nonlinearity on the achievable information rates in transmission systems with bandwidths of up to 12 THz. We demonstrate the use of the model in the optimization of launch power spectral profiles for a variety of dynamic gain equalizer arrangements in a 1000 km standard single-mode fiber link, using particle swarm optimization and the steepest descent algorithm. Such nonlinear models and optimization methods could be applied in OON planning tools, for example, in optical link emulators to estimate quality-of-transmission and data throughput, and in impairment-aware software-defined network control and management.

Integrating Radio-Over-Fiber Communication System and BOTDR Sensor System.

In this paper, we propose and experimentally demonstrate for the first time, the integration of a radio-over-fiber (RoF) communication system and a Brillouin optical time-domain reflectometry (BOTDR) distributed sensor system using a single optical fiber link. In this proof-of-concept integrated system, the communication system is composed of three modulation formats of quadrature phase-shift keying (QPSK), 16-quadrature amplitude modulation (16-QAM) and 64-QAM, which are modulated onto an orthogonal frequency division multiplexing (OFDM) signal. Whereas, the BOTDR sensor system is used for strain and/or temperature monitoring over the fiber distance with a spatial resolution of 5 m using a 25 km single-mode silica fiber. The error vector magnitude (EVM) is analyzed in three modulation formats in the presence of various BOTDR input pump powers. Using QPSK modulation, optimized 18 dBm sensing and 10 dBm data power, the measured EVM values with and without bandpass filter are 3.5% and 14.5%, respectively. The proposed system demonstrates a low temperature measurement error (±0.49 °C at the end of 25 km) and acceptable EVM values, which were within the 3GPP requirements. The proposed integrated system can be effectively applied for practical applications, which significantly reduces the fiber infrastructure cost by effective usage of a single optical fiber link.

Setting the scene for slow fashion: Digital explorations of New York's fibrescape

Abstract Farmers with sheep, alpacas and goats provide opportunities for local slow fashion. This is a practice-based case study that developed after discovering primary issues experienced by New York fibre farmers such as low profits and difficulty reaching a market. Beyond products available, farmers highlighted the educational value of their farms, animals and fibres, which are intangible aspects of slow fashion. The aim of this research is to increase the visibility of New York farms, natural fibres and opportunities for slow fashion through digital media short films. This research was guided by Actor Network Theory and the cartography of controversies method during broader slow fashion research in 2013 through 2017. The four New York farm-to-fashion films highlight fibre agro-tourism, artisanship, locally produced fashion and sorting raw fibres for scaled production. The process of creating the short films and interacting with farmers made several entities within the local farm-to-fashion network more visible, including limited access to communication technologies in rural areas, water issues, the closure of fibre mills and economic development issues. The 'collective existence' of local farm-to-fashion is complex and includes social, economic, political and environmental elements in addition to previously considered entities such as fibre animals, farmers, infrastructure and tools. The films were presented to several academic, community audiences and are available as open resources.

Novel Digital Radio Over Fiber (DRoF) System With Data Compression for Neutral-Host Fronthaul Applications

Digital radio-over-fibre transmission has been studied extensively as a way of providing seamless last-mile wireless connectivity by carrying digitised radio frequency (RF) services over broadband optical infrastructures. With the growing demand on wireless capacity and the number of wireless services, a key challenge is the enormous scale of the digital data generated after the digitisation process. In turn, this leads to optical links needing to have very large capacity and hence, high capital expenditure (CAPEX). In this paper, we firstly present and then experimentally demonstrate a multiservice DRoF system for a neutral-host fronthaul link where both forward and reverse links use data compression, multiband multiplexing and synchronisation algorithms. The effect of a novel digital automatic gain control (DAGC) is comprehensively analysed to show an improved RF dynamic range alongside bit rate reduction. In this case, the system allows all cellular services from the three Chinese mobile network operators (MNOs) to be converged onto a single fiber infrastructure. We successfully demonstrate 14 wireless channels over a 10Gbps 20km optical link for indoor and outdoor wireless coverage, showing a minimum error value magnitude (EVM) of 60dB RF dynamic range. It is believed that the technology provides an ideal solution for last-mile wireless coverage in 5G and beyond.

The Outlook for PON Standardization: A Tutorial

In light of the 5G deployments, edge computing, and future high bandwidth services, the industry is rethinking the optical access network architecture design. Passive optical network (PON) with its efficient fiber infrastructure plays an essential role in this design transformation. This article reviews the driving forces shaping the new generations of PON systems in the coming years; and discusses the course of action in the FSAN Group, ITU-T, and IEEE standards bodies to address the impending requirements.

Entanglement between a Diamond Spin Qubit and a Photonic Time-Bin Qubit at Telecom Wavelength.

We report on the realization and verification of quantum entanglement between a nitrogen-vacancy electron spin qubit and a telecom-band photonic qubit. First we generate entanglement between the spin qubit and a 637nm photonic time-bin qubit, followed by photonic quantum frequency conversion that transfers the entanglement to a 1588nm photon. We characterize the resulting state by correlation measurements in different bases and find a lower bound to the Bell state fidelity of ≥0.77±0.03. This result presents an important step towards extending quantum networks via optical fiber infrastructure.

Measurement-device-independent quantum key distribution coexisting with classical communication

The possibility for quantum and classical communication to coexist on the same fiber is important for deployment and widespread adoption of quantum key distribution (QKD) and, more generally, a future quantum internet. While coexistence has been demonstrated for different QKD implementations, a comprehensive investigation for measurement-device independent (MDI) QKD—a recently proposed QKD protocol that cannot be broken by quantum hacking that targets vulnerabilities of single-photon detectors—is still missing. Here we experimentally demonstrate that MDI-QKD can operate simultaneously with at least five 10 Gbps bidirectional classical communication channels operating at around 1550 nm wavelength and over 40 km of spooled fiber, and we project communication rates in excess of 10 THz when moving the quantum channel from the third to the second telecommunication window. The similarity of MDI-QKD with quantum repeaters suggests that classical and generalized quantum networks can co-exist on the same fiber infrastructure.

Connected OFCity Challenge: Addressing the Digital Divide in the Developing World

Over the past 50 years, the development of information and communications technology has provided unprecedented support to the steady economic growth of developed countries. In recent years, some of the largest growth has been reported in emerging economies, which, however, often lack adequate telecommunications infrastructure to further sustain their development. Although a number of service providers and system vendors have started to address the issue, the challenges they encounter are substantially different from those in the developed world, including an unreliable electricity grid, poor fiber infrastructure, low revenue expectations, and often a harsh climate environment. This paper reports use cases and solutions pertinent to the development of the networking infrastructure in emerging economies, provided by organizations directly involved in such activities. After providing some background information on the current state of network infrastructure and the main challenges for Africa and rural China, the paper provides details on two proposed solutions. The first focuses on the provisioning of services and network infrastructure through the development of low-cost data centers, whereas the second proposes cost-effective adaptation of both fiber and hybrid copper–fiber technology to rural areas. The article is concluded with a brief discussion on the complementarity of the two approaches.

KaaS: Key as a Service over Quantum Key Distribution Integrated Optical Networks

In the Internet Age, optical networks are vulnerable to numerous cyberattacks, and conventional key distribution methods suffer from the increased computational power. QKD can distribute information-theoretically secure secret keys between two parties based on the principles of quantum mechanics. Integrating QKD into optical networks can leverage existing fiber infrastructures with wavelength division multiplexing for the practical deployment of secret keys, and accordingly employ the secret keys for optical-layer security enhancement. Then, how to efficiently deploy and employ secret keys over QKD-integrated optical networks are emerging as two challenges. This article proposes a framework of key as a service (KaaS, i.e., providing secret keys as a service in a timely and accurate manner to satisfy the security requirements) to jointly overcome these two challenges. To enable the typical functions (i.e., secret-key deployment and employment) in KaaS, two secret-key virtualization steps, that is, key pool (KP) assembly and virtual key pool (VKP) assembly, are introduced. Also, we illustrate a new QKD-integrated optical network architecture from a holistic view, where the control layer is implemented by software defined networking for efficient network management. A time-shared KP assembly strategy and an on-demand VKP assembly strategy are presented for KaaS implementation. The success probabilities of KP assembly and VKP assembly are defined to evaluate the benefits of KaaS for efficiently deploying and employing secret keys as well as for security enhancement over QKD-integrated optical networks.