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ARRIS OBI-free RFoG solutions expand fiber reach in HFC networks all the way to the home or business. They deliver the full potential of DOCSIS 3.1 and provides the infrastructure for future transition to all-fiber, 10G PON networks.

RFoG (Radio Frequency over Glass) is a fiber-deep network design in which the coax portion of an HFC (Hybrid Fiber Coax) network is replaced by a PON (Passive Optical Network) architecture. Fiber to the Home / Premises (FTTH, FTTP) makes economic sense for new build, multi-dwelling units, businesses and high-use consumers.

RFoG eliminates the need for HFC nodes, RF amplifiers, and taps and passives in the network, while utilizing the existing cable headend and subscriber equipment (modems, gateways and set-tops) and back-office support systems.

An RFoG network is capable of seamlessly delivering functionality and services to subscribers in a manner that is comparable to current HFC systems.

An ARRIS RFoG network provides distinct performance advantages over current HFC networks, including:

  • Proven support for DOCSIS 3.1 services
  • A more economical choice for MDU and rural deployments
  • Comparable to HFC performance in greenfield suburban residential deployments
  • Expand upstream and downstream bandwidth and significantly extend network reach by eliminating the RF noise and ingress inherent in coax deployments
  • Lower energy costs and provide a greener alternative to coaxial delivery, with the added benefit of less network downtime due to power outages
  • Significantly lower operating and maintenance costs by eliminating the need for HFC nodes and RF amplifiers
  • Immunity to environmental factors – such as temperature, galvanic corrosion, and humidity – that can cause coaxial cabling to degrade physically over time
  • Efficiently bridge between HFC and FTTx architectures and provides the infrastructure needed to transition to all-fiber, high-bandwidth 10G PON networks
  • Multiple options to eliminate Optical Beat Interface (OBI) in the network
HFC and RFoG networks comparison - ARRIS OBI-Free RFoG Solutions

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To unlock full potential of RFoG there are some operational challenges to address. This is especially important for migration to DOCSIS 3.1 and other next-generation delivery systems.

The Challenge: Extending the Network’s Reach

RFoG networks were designed initially to support 32 subscribers from a single fiber feed, with a maximum distance of 20 km and a 25 dB loss budget. In densely populated urban environments, this network design easily supported large numbers of subscribers. When the time came to extend the RFoG network to large service groups in suburban and rural areas, Operators found themselves exceeding 20 km distance and 25 dB loss budget and were unable to maintain network performance. In order to service these groups and still realize the advantages of a fiber-based network, Operators needed to find a way to cost-effectively extend the reach of their RFoG networks beyond 20 km while maintaining a 25 dB loss budget.

The Solution: The ARRIS NH4000 Optical Virtual Hub (VHub)

Our NH4000 Optical Virtual Hub (VHub) can extend the reach of a RFoG network’s single fiber feed in excess of 20, 40, 80, or even 100 km while still supporting 32 subscriber service groups and maintaining a 25 dB loss budget. A single ARRIS VHub utilizes internal 2 x 8 splitting that, in combination with 1 x 16 external splitting for each access line, easily extends services to 256 homes or more, and also supports the upstream returns required by the network.

Extending reach of RFoG - ARRIS OBI-Free RFoG Solutions
Extending reach of RFoG

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The Challenge: Dealing with OBI

A second challenge of RFoG deployment is Optical Beat Interference (OBI). In an industry where the flawless delivery of high-speed network data is the paramount objective, OBI can be a major impediment to efficient and error-free data delivery. While a complex phenomenon, OBI can simply be explained as this: when two or more optical transmitters in the RFoG network with closely spaced or identical wavelengths transmit simultaneously, it causes the upstream signal to degrade at the receiver. This degradation, in turn, damages the data being transmitted on the upstream signal. Data packets are lost, and the end user experiences service interruptions. Unfortunately, RFoG networks are likely to experience OBI, primarily because of the large number of R-ONUs (RFoG Optical Network Units) at the premises all simultaneously transmitting back to the headend’s optical receiver on the same wavelength.

OBI mitigation is possible in traditional RFoG networks but the solutions are imperfect to varying degrees. For example, a common method of mitigating OBI uses a CMTS scheduler to manage upstream bursts in a time domain. When the CMTS identifies two or more R-ONUs with sufficiently close or overlapping wavelength transmissions, it schedules one R-ONU to transmit upstream at a time preserving the integrity of the upstream signals. In the short term, this method is perfectly adequate. However, over time, this option can prevent networks from efficiently using its full channel capacity. It also can have a real impact on the network’s future growth: as channels and bandwidth approach maximum capacity, network efficiency will decrease in proportion to the number of R-ONUs in the time domain. As a result, this could seriously hamper the ability to grow the network in parallel with consumer demand for new services and create a major roadblock to implementing DOCSIS 3.1 services.

The Solution: ARRIS “OBI-free” Solutions

ARRIS offers a wide range of innovative solutions that eliminate OBI in RFoG networks and supports the transition to DOCSIS 3.1 services:

The AgileMax Family of Fiber Distribution Devices: By replacing the optical splitters found in traditional RFoG architectures, AgileMax’s active optical distribution technology completely eliminates OBI from the network—even if it deploys multiple, active upstream lasers—and achieves service groups of up to 1024 R-ONUs to a single headend optical receiver port. AgileMax supports less-expensive ‘non-tunable’ R-ONUs and may be used with VHub technology to extend the reach of your network to over 20 km.

OBI-free R-ONUs: ARRIS OBI-free R-ONUs allow Operators to select one of sixteen upstream wavelengths for each unit via an internal rotary switch, which provides enough wavelength separation to avoid OBI. This wavelength management approach allows multiple OBI-free R-ONUs to transmit simultaneously into a single upstream optical receiver with no chance of OBI.

VHub RFoG Network - ARRIS OBI-Free RFoG Solutions
VHub RFoG Network

Aggregated AgileMax Network - ARRIS OBI-Free RFoG Solutions
Aggregated AgileMax Network

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ARRIS offers robust, field-proven RFoG solutions designed to meet the needs of today’s evolving networks while leveraging your existing valuable network assets. Solutions that enable deployment of DOCSIS 3.1 and expansion to 1.2 GHz with evolution paths to 10G PON architectures. The combination of powered or passive splitters, tunable R-ONUs and VHub technology means that ARRIS can deliver the optimum solution for your network.

ARRIS leverages our leadership in video and broadband technology and services, combined with our dedication to close collaboration with our customers, to continually innovate next-generation technologies. With more than 500 access and transport patents earned over the past 60 years, ARRIS has been a major contributor to the development of RFoG standards. We were the first to have its equipment incorporated into an RFoG deployment.

ARRIS has shipped more R-ONUs than any other vendor in the industry, and our innovative VHub and AgileMax technologies provide a wide range of network design options.

ARRIS AgileMax® - Complete OBI Elimination HPON™ Distribution Solution
ARRIS AgileMax® - Complete OBI Elimination HPON™ Distribution Solution

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Solution Products

NH/VH4000/2000 Virtual Hubs (VHub)
NH/VH4000/2000 Virtual Hubs (VHub)
Outside Plant Hardened Optical Virtual Hubs
AgileMax 1RU
AgileMax 1RU
Complete OBI Elimination RFoG Distribution Platform
RFoG-compliant Optical Network Units