In this tutorial overview, the principles, advantages, challenges, and practical requirements of optical orthogonal frequency division multiplexing (OFDM)-based optical access are presented, with an emphasis on orthogonal frequency division multiple access (OFDMA) for application in next-generation passive optical networks (PON). General OFDM principles, including orthogonality, cyclic prefix use, frequency-domain equalization, and multiuser OFDMA are summarized, followed by an overview of various optical OFDM(A) transceiver architectures for next-generation PON. Functional requirements are outlined for high-speed digital signal processors (DSP) and data converters in OFDMA-PON. A techno-economic outlook for such a “software-defined,” DSP-based optical access platform is also provided.

OFDM for Next-Generation Optical Access Networks

Feature Issue on
Optical Access Networks (OAN) The passive optical network (PON) is
an optical fiber based network architecture, which can provide much higher bandwidth
in the access network compared to traditional copper-based networks. Incorporating
wavelength-division multiplexing (WDM) in a PON allows one to support much higher
bandwidth compared to the standard PON, which operates in the "single-wavelength
mode" where one wavelength is used for upstream transmission and a separate one is
used for downstream transmission. We present a comprehensive review of various
aspects of WDM-PONs proposed in the literature. This includes enabling device
technologies for WDM-PONs and network architectures, as well as the corresponding
protocols and services that may be deployed on a WDM-PON. The WDM-PON will become a
revolutionary and scalable broadband access technology that will provide high
bandwidth to end users.

/pdf/wavelength-division-multiplexed-passive-optical-network-wdm-428jyy569l.pdf

Wavelength-division-multiplexed passive optical network (WDM-PON) technologies for broadband access: a review (Invited)

5G is the next cellular generation and is expected to quench the growing thirst for taxing data rates and to enable the Internet of Things. Focused research and standardization work have been addressing the corresponding challenges from the radio perspective while employing advanced features, such as network densification, massive multiple-input-multiple-output antennae, coordinated multi-point processing, inter-cell interference mitigation techniques, carrier aggregation, and new spectrum exploration. Nevertheless, a new bottleneck has emerged: the backhaul. The ultra-dense and heavy traffic cells should be connected to the core network through the backhaul, often with extreme requirements in terms of capacity, latency, availability, energy, and cost efficiency. This pioneering survey explains the 5G backhaul paradigm, presents a critical analysis of legacy, cutting-edge solutions, and new trends in backhauling, and proposes a novel consolidated 5G backhaul framework. A new joint radio access and backhaul perspective is proposed for the evaluation of backhaul technologies which reinforces the belief that no single solution can solve the holistic 5G backhaul problem. This paper also reveals hidden advantages and shortcomings of backhaul solutions, which are not evident when backhaul technologies are inspected as an independent part of the 5G network. This survey is key in identifying essential catalysts that are believed to jointly pave the way to solving the beyond-2020 backhauling challenge. Lessons learned, unsolved challenges, and a new consolidated 5G backhaul vision are thus presented.

5G Backhaul Challenges and Emerging Research Directions: A Survey

The main bandwidth bottleneck in today's networks is in the access segment. To address that bottleneck, broadband fiber access technologies such as passive optical networks (PONs) are an indispensable solution. The industry has selected time-division multiplexing (TDM) for current PON deployments. To satisfy future bandwidth demands, however, next-generation PON systems are being investigated to provide even higher performance. In this paper, we first review current TDM-PONs; we designate them as generation C. Next, we review next-generation PON systems, which we categorize into C+1 and C+2 generations. We expect C+1 systems to provide economic near-term bandwidth upgrade by overlaying new services on current TDM-PONs. For the long term, C+2 systems will provide more dramatic system improvement using wavelength division multiplexing technologies. Some C+2 architectures require new infrastructures and/or equipment, whereas others employ a more evolutionary approach. We also review key enabling components and technologies for C+1 and C+2 generations and point out important topics for future research.

/pdf/next-generation-optical-access-networks-41pmztcn8d.pdf

Next-Generation Optical Access Networks

It is anticipated that more than 75 Mb/s per subscriber is required for the convergence service such as triple-play service (TPS) Among several types of high-speed access network technologies, wavelength-division-multiplexing passive optical network (WDM-PON) is the most favorable for the required bandwidth in the near future Furthermore, WDM technologies, such as athermal arrayed-waveguide grating (AWG) and low-cost light source, have matured enough to be applied in the access network In this paper, the authors propose and implement a WDM-PON system as a platform for TPS The system employs an amplified spontaneous emission (ASE)-injected Fabry-Pe/spl acute/rot laser diode scheme It has 32 channels of 125 Mb/s and adopts Ethernet as Layer 2 Multicast and virtual local area network features are used for the integration of services such as Internet protocol high-definition broadcast, voice-over Internet protocol, video on demand, and video telephone The services were demonstrated using the WDM-PON system

Fiber-to-the-home services based on wavelength-division-multiplexing passive optical network

Aspects of the subject disclosure may include, for example, a system for detecting an accumulation of a liquid on a transmission medium that may interfere with the propagation of guided electromagnetic waves on a surface of the transmission medium, and directing a device to remove at least a portion of the liquid accumulating on the surface of the transmission medium to mitigate the interference. Other embodiments are disclosed.

Method and apparatus for mitigating interference affecting a propagation of electromagnetic waves guided by a transmission medium

We investigate using Fabry-Perot lasers as the upstream transmitters in a wavelength-division-multiplexed passive optical network (WDM-PON). We demonstrate transmission of a 10-Mb/s signal through each port of a wavelength-grating router followed by 18 km of fiber using an uncooled Fabry-Perot laser. These signals could be subcarrier multiplexed together, so that each user would have a dedicated radio-frequency channel. Since Fabry-Perot lasers provide more output power than low-cost light-emitting diodes, this may enable deployment of WDM-PON's in areas where optical loss prohibits the use of other low cost optical sources. The bit-rate is limited by mode-fluctuations being converted into intensity noise when transmitted through the router.

A spectrally sliced PON employing Fabry-Perot lasers

A passive optical network is provided that spectrally slices optical signals transmitted in both upstream and downstream directions utilizing wavelength division multiplexing routing. The passive optical network preferably includes an incoherent signal source at both ends to provide signals that are spectrally sliced according to optical frequency. The downstream information may be transmitted in a conventional data format. The upstream transmissions may be segregated by subcarrier multiplexing, time scheduling or wavelength division multiplexing. A broadcast signal can be overlayed with point-to-point information for transmission to plural network units.

Wavelength division multiplexing passive optical network including broadcast overlay

As the number of wireless users and per-user bandwidth demands continue to increase, both the vendor and carrier communities agree that wireless networks must evolve toward more dense deployments. So-called heterogeneous networks are a commonly proposed evolution, whereby existing macrocellular networks are supplemented with an underlay of small cells. The placement of new small-cell sites is typically determined based on various location-dependent factors such as radio propagation calculations, user densities, and measurements of congestion and demand. The backhaul network, which can account for a significant portion of the total cost of the deployment, is then designed in reaction to the placement of small cells. In contrast, we describe a design method that first considers the locations of existing fibered and powered facilities that might be leveraged to provide inexpensive backhaul. Naturally, such a method is only feasible if the carrier has a legacy local fiber network. This article describes an efficient fiber backhaul strategy for a small-cell network, which leverages facilities associated with an existing FTTN residential access network. Once potential small-cell sites are determined from among all FTTN remote terminals, optimization techniques are used to choose the most efficient subset of sites for maximum coverage, and to design the fiber backhaul architecture.

http://mauricio.resende.info/doc/small-cells.pdf

Design and optimization of fiber optic small-cell backhaul based on an existing fiber-to-the-node residential access network

Fiber to the home in the U.S. market has not been deployed as rapidly as many had hoped or predicted. We examine some of the historical, competitive, and economic reasons for this. We argue that, from a competitive service perspective, it may be difficult to construct compelling business cases for large-scale deployment without either a technical need for fiber, or significant changes in either public policy or industrial organization.

Kenneth C. Reichmann

Papers

Method and apparatus for mitigating interference affecting a propagation of electromagnetic waves guided by a transmission medium

A spectrally sliced PON employing Fabry-Perot lasers

Wavelength division multiplexing passive optical network including broadcast overlay

Design and optimization of fiber optic small-cell backhaul based on an existing fiber-to-the-node residential access network

A view of fiber to the home economics