Extend fiber to the premises with OBI-free RFoG

To unlock the full potential of RFoG there are some operational challenges to address. This is especially important for migration to DOCSIS 3.0 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 kilometers and a 25-decibel 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 the 20-km distance and 25-dB loss budget, impacting network performance. To service these groups and still realize the advantages of a fiber-based network, operators needed a cost-effective solution.

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 paramount, 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, the upstream signal degrades 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, traditional RFoG networks are likely to experience OBI due to 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 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 different time—preserving the integrity of the upstream signals. In the short term, this method is perfectly adequate. However, over time, it 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. 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 3.0 services.

VHub RFoG network

Aggregated AgileMax Network

The solution: CommScope “OBI-free” solutions

CommScope offers a wide range of innovative solutions that eliminate OBI in RFoG networks and support the transition to DOCSIS 3.0 services:

The AgileMax® family of fiber distribution devices: AgileMax’s active optical distribution technology replaces the optical splitters found in traditional RFoG architecture, completely eliminating OBI from the network—even if the network deploys multiple active upstream lasers. AgileMax enables service groups of up to 1,024 R-ONUs to a single head-end optical receiver port and supports less-expensive “non-tunable” R-ONUs that, with VHub technology, can extend the reach of your network to over 20 km.

OBI-free R-ONUs: CommScope OBI-free R-ONUs allow operators to select one of 16 upstream wavelengths for each unit via an internal rotary switch, providing 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.

CommScope 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 the deployment of DOCSIS 3.0 and the expansion to 1.2 GHz with evolution paths to 10G PON architectures. Deliver the optimum solution for your network using CommScope’s powered or passive splitters, tunable R-ONUs and VHub technology.

CommScope AgileMax®—complete OBI elimination distribution solution

Leverage our leadership in video and broadband to innovate your next-generation technologies. With more than 500 access and transport patents earned over the past 60 years, CommScope has been a major contributor to the development of RFoG standards. As a leading vendor in the industry, we have shipped more R-ONUs than any other vendor, with our innovative VHub and AgileMax technologies providing a wide range of network design options.