Aurora - Whitepaper014 Reva Rfpon

Aurora Networks, Inc.Aurora Networks, Inc.

June 2009

WHITE PAPER 14

2009 Aurora Networks, Inc. All rights reserved.

2009 Aurora Networks, Inc. All rights reserved.2

RFPON - The Next-generation RFoG Solution

Aurora Networks, Inc.5400 Betsy Ross DriveSanta Clara, CA 95054Tel 408.235.7000Fax 408.845.9045www.aurora.com

Copyright 2009 Aurora Networks, Inc. All rights reserved.

All rights reserved. No part of this document may be reproduced, stored in a retrievalsystem, or transmitted in any form by any means, electronic, mechanical, photographic,magnetic, or otherwise without the prior written permission of Aurora Networks.

2009 Aurora Networks, Inc. All rights reserved. 3

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Abstract

Auroras RFPON system architecture enablesthe migration of traditional RFoG (RF overGlass) architecture into a system that supportsRFoG plus PON (GEPON / GPON / future10GEPON) services simultaneously over thesame fiber (or fibers) to the home or premises.This RFPON architecture builds upon andutilizes the installed HFC fiber infrastructureto feed RFPON fiber services to all areas ofthe HFC plant, located anywhere between theheadend/hub and at distances in excess of 60kilometers from the headend/hub.

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BACKGROUND

Do cable operators need to deploy Fiber to thePremises (FTTP) networks to provide all theservices demanded by subscribers, both todayand tomorrow? Resolutely no! The hybrid fiber/coaxial (HFC) network, and Fiber Deep inparticular, can provide all the needed networkcapacity and more. However, there are scenarioswhere it makes sense for cable operators to deployfiber all the way to the home. In particular, FTTPnetworks may stop cables competition fromsecuring new footholds and help displace thecompetition. In rural areas with new builds orextensive upgrades and with low populationdensity, FTTP may prove more cost effective whileproviding additional operational benefits.Moreover, FTTP may provide new revenuestreams more cost-effectively. Specifically, areasof interest could be:

New housing developments

Rural, low-density areas

Multi-Dwelling Units (MDUs)

Commercial areas (co-located withresidential areas)

For a new housing development, the builder canoften raise the sale price of the house if it can beclaimed that the house is fiber ready. Indeed, inmany instances the extra cost of deploying thefiber all the way to the home will be met or heavilysubsidized by the builder. FTTP keeps thecompetition out.

For rural, low-density areas (



be happy to pay for a superior triple play service.For this application, the fiber can be distributedfrom the basement of the building and fed to theactual dwelling unit, providing true FTTP.However, there are other MDUs where this isnot feasible; for example, in a building alreadycabled with coax, trying to replace that with fibermay be prohibitively expensive. In these situations,the fiber can be run into the basement of thebuilding and either distributed via coax from thereor further split and the fiber fed via elevator shafts(or similar) to wiring closets on each floor, withcoax running from those closets to the unit.

For business areas, it may be optimum to startwith FTTP to provide commercial services viaPON, supporting high speed data and telephony.However, many businesses require video as welland this can be provided via traditional RFoG, allon a single fiber.

In all these scenarios, the optimal application isan architecture that operates from the sameheadend equipment as the traditional HFC plant,supports all the same services as HFC withpotential for new and innovative services,interfaces with all the same back-office equipment(in the same way) but is actually fiber to thepremises rather than the more traditional coax.This solution runs fiber all the way to the premisesto serve a single-output mini node customerpremises equipment (CPE) so that traditional RFoutput is maintained, enabling continued use ofset-top boxes, DOCSIS cable modems andeMTAs. This RFoG architecture, first deployedby Aurora Networks in 2006, has been taken tothe next level with our next-generation RFoGsolution, RFPON. RFPON supports a traditionalRFoG architecture but with seamless support forPON services, when needed. Alternatively, Aurora

Networks solution is so flexible that one can startwith PON and then add RFoG services.

This white paper introduces Auroras RFoG andRFPON solutions, emphasizing how Aurora, withthe benefit of numerous field deployments, hasdeveloped tools to both solve the inherent issueswith RFoG implementations and then provide asmooth migration path to an all-IP access networkin the future, or vice-versa.

RFoG BUILDING BLOCKS

The reference architecture for a tradi-tional RFoG system, from headend/hub,is shown in Figure 1. The referencearchitecture at the headend/hub site comprises adownstream optical transmitter operatingnominally at 1550 nm, optical amplification asrequired by the topology being served and a wavedivision multiplexer (WDM) filter for combiningdownstream and upstream optical signals on asingle fiber. It also comprises an upstream opticalreceiver which receives the 1310 nm upstreamoptical signals and converts them to RF. In thefield, conveniently located between the headendand the end customers, there would be variousoptical splitters, supporting distances up to 20kilometers from the headend with each fibersupporting up to 32 customers.

At the customer site, an RFoG CPE is required,designed for either indoor or outdoor installation,and which comprises a WDM filter to separatethe downstream optical signal (at 1550 nm) fromthe selected upstream wavelength. The down-stream optical receiver converts the RF down-stream signals from the downstream opticalcarrier, and the RF signal is then fed via coax into

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the home. In the upstream, the RF signal issupplied to an upstream transmitter (with an outputat 1310 nm) for onward transmission to theheadend. Another emerging upstream wavelengthis 1610 nm; the wavelength of choice set by theSCTE standards committee. This wavelengthprovides compatibility on the same fiber withexisting PON and the emerging 10G-PON standardwavelengths.

The associated RFoG reference diagramfrequency/wavelength spectrum for a typical NorthAmerica system is shown in Figure 2.

This is exactly the same suite of products offeredto any subscriber in any area of the existing HFCcable plant, not just areas which are fed via fiber.This results in a completely unified headend,significantly simplifying operation for the cableoperator.

Figure 1. RFoG Reference Architecture, Highlighting Distance Limitations

Figure 2. RFoG Spectrum



LIMITATIONS OF HEADEND/HUB-BASED RFoG

While the system does meet many ofthe objectives of the cable operatorto deploy an HFC-compatibleFTTP network, technically this solution haslimitations, namely:

Limited downstream reach

Limited upstream reach

Fiber-intensive

While the downstream reach is important, andlimited by the power which can be launched intothe downstream fiber, the system limitation willbe driven by the upstream. The major costelement in the system is the RFoG CPE and itsassociated laser diode for return transport, henceminimizing the cost of this component is important.To overcome the upstream loss budget of 2426dB, a 20 km 32-split system with a fully loadedreturn band (i.e., four DOCSIS channels tosupport DOCSIS 3.0, plus an additional VoIPDOCSIS channel), and a high power upstreamlaser would be required (on the order of 10 dBm),which is costly; this is clearly not the direction togo for any type of CPE. Alternatively, an upstreamreceiver technology breakthrough would berequired to achieve the very low input levelsrequired by a CPE using a cost-effective low powerlaser, assuming acceptable carrier-to-noiseperformance. A 1610 nm laser does provide PONcompatibility, and technically can provide thehigher optical power; however, this is a moreexpensive unit. Auroras upstream receiversolution supports a 24 dB loss budget at 1610nm and 25.6 MHz load with just 3 dBm RFoGCPE transmitters without special provisions ormodulation techniques and is compatible with any

directly-modulated laser RFoG CPE. There areother solutions being proposed, namely FM anddigital links from the CPE, but they do not offerthe same compatibility and flexibility to theoperator.

Aurora can provide a traditional headend/hub-based RFoG solution. However, depending uponactual equipment and network configuration, thereach will only be in the 1020 kilometer range.Unfortunately, this greatly impacts the area whichcan be served directly from the cable systemsheadends/hubs.

In a typical RFoG deployment, each fiber wouldserve up to 32 subscribers. For example, in a256 home service area, a cable operator wouldneed to dedicate eight fibers from the headend/hub to that area to ensure service to eachsubscriber. Similarly, with these direct fiber runsfrom the headend, there is no practical method toprovide any redundancy in the system. With thegrowing importance of high-demand, high-revenue services, lack of redundancy is not anideal solution.

AURORA NETWORKS VHUB-BASEDRFoG SOLUTION

Aurora has pioneered technology whichefficiently overcomes all the limitationsof an RFoG system: the VHub. TheVHub houses a fully operational hub in a standardnode housing. In this application it is designed toserve 256 subscribers. Effectively, it moves thefunctionality of an indoor hub to a weather-proofnode enclosure that can be deployed closer tosubscribers in the network. The same can beachieved with the OTN configuration so prevalent


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in xPON deployments, but the VHub solutionavoids requirements for permits and rights of wayaccess as well as land acquisition costs while, atthe same time, providing higher granularity,scalability and security. VHubs can be strand orpedestal mounted. The key VHub features forthis application are:

Support for up to 12 plug-in modules(forward path EDFAs, return path receivers,integrated forward/return wavelengthmanagement modules with or without returnpath receiver functionality, digital transceiv-ers and transponders, optical switches,monitoring transceivers and opticalmultiplexers)

Monitoring and control of the VHub via ourOpti-Trace EMS software

Redundancy and route diversity with switch-ing times less than 10 milliseconds (typically



the upstream bandwidth. Once received, theupstream signals are then fed into two 2-fer digital return transmitters, eachtransmitting on one of 15 CWDM wave-lengths. Use of the digital return overcomesthe distance limitation (now with a reach >60kilometers) while use of WDM technologyprovides a very fiber-efficient solution.(Auroras white paper titled Digital ReturnTechnology provides more detailedinformation.)

Fiber-intensive. With the traditional RFoGapproach, one dedicated transport fiber isneeded for 32 subscribers. With the VHub,this is reduced to one transport fiber for 256subscribers, with the forward and reversewavelengths sharing the same fiber. Thetraditional approach needs eight times morefiber. In addition, with the VHub, the existingHFC fiber can be shared with the RFoGwavelengths. With Auroras various O-band and C-band multi-wavelengthtechnologies, a previously used fiber can befreed up for this application.

Route-redundancy option. Aurorashardened VHub-based optical switchprovides route diversity with switching timesless than 10 milliseconds (typically


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future-proof; it permits an optional overlay with eitheran IEEE 802.3ah (EPON, or GEPON) or an ITUG.984 (GPON) system, given that both these systemsuse 1310 nm for upstream data communications. Anadditional factor in selection of the 1610 nm wave-length is its compatibility with the emerging IEEE802.3av (10GEPON) system which is heading towardsstandardizing on 1577 nm downstream/1270 nm

upstream, but this currently remains a work-in-progress. Meanwhile, other options can be madeavailable upon request, such as a 1590 nm up-stream path already in use by several cable op-erators worldwide.

The new wavelength frequency/content plan isshown in Figure 4.

Figure 4. RFPON Supports the Best of Both Worlds

GEPON SOLUTION

Aurora Networks Gigabit EthernetNode GEPON Module, the GE4132M,is an OLT module designed to work inall our VHubs and nodes, making PON deliveryfrom an outdoor platform a reality.

Using this OLT module, cable operators can cost-effectively add all-IP services to their networkson a service area by service area basis, operatingin parallel with traditional cable TV services thatare transported over the 1550 nm and 1610 nmwavelengths. Ultimately, but only if and whenjustified by revenue growth, Node PON equipmentcan enable full migration of an installed HFCnetwork to a standards-based GEPON FTTPnetwork. With a VHub which can support one,two or three Node PON modules, the dedicatedIP-bandwidth to a group of 256 subscribers canbe as high as 3 Gbps full duplex. (This is in addition

to all the traditional cable TV services that arereceived from the traditional RFoG deployment.)Of course, the CPE device at the home will alsoneed to be upgraded to support the new PONservices. However, by adhering to the widely-deployed GEPON standard, the expectation isthat the additional CPE device would be cost-effective, with costs driven down by wide-scaledeployment. Going one step further and eliminatingthe RF overlay would allow five Node PONmodules to be supportedup to 5 Gbpsdedicated bi-directional bandwidth to 256subscribers. With future generation support forthe evolving 10GEPON standard, bandwidthpotential is almost limitless. This is truly a future-proof solution.

Today Aurora Networks is the only company toprovide this seamless evolution from an HFCarchitecture to a full IP-based network on a



service area by service area implementation. Inaddition, there are notable key features for ourNode PON solution:

Fully-compliant with the GEPON standardcompatible with off-the-shelf GEPON CPEdevices

Todays bandwidth is 1000 Mbps bi-directional

Each module can support up to 64subscribers

Designed to fully interoperate with existingDOCSIS cable modem back-officeprovisioning systems.

PRACTICAL EXAMPLE

The following example, shown in Figure5, examines how a cable operator coulduse Auroras RFoG and RFPONsolutions to serve a rural area.

Initially this deployment is viewed as an extensionof the installed HFC network. The VHub wouldbe located at a convenient place, being servedfrom the same headend equipment and

Figure 5. Serving a Rural Area


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provisioning system. If no route diversity isrequired, the VHub would be served by just onefiber from the nearest fiber node. If the broadcastand narrowcast services are not available on the1550 nm wavelength, then the appropriate trans-mitter would need to be installed at the headend/hub and a dark fiber to the node commissioned(or a wavelength added to an existing fiber). Fromthe VHub, today there would be eight fibers, eachconnected to the appropriate splitter, to servicethe widely-distributed homes in the area. If thecable operator is looking for a future-proofsolution, it is recommended that 1610 nm ratherthan 1310 nm be adopted for the upstream signal.The downstream services (broadcast TV,downstream data and VoD traffic, etc.) are carriedon 1550 nm with all the associated upstream trafficon 1610 nm. (The CPE device would also needto mirror these wavelength selections.)

Once network capacity demand exceeds thatavailable, as a next-step a Node PON modulecan be installed in the VHub, introducing dedicatedIP services. The corresponding CPE would needto be upgraded to service the PON infrastruc-ture. (Typically, GEPON-ready CPEs will not bedeployed until a subscriber has signed-up for thoseservices; this considerably reduces the upfrontcapital cost.) The frequency/channel plan for boththe traditional and the IP services is shown in Figure4. With the Node PON seamlessly integrating withDOCSIS provisioning systems, the introductionof this new technology does not cause disruptionto back-office processes and procedures.

Additionally, with each Node PON supportingsymmetrical bandwidth of up to 1 Gbps, thissolution is also compelling for providing serviceto businesses which are co-located in the samerural serving area. This could result in the cableoperator having a unified network for bothresidential and business consumers with minimalcapital expenditure and no additional operatingexpensesand while gaining additional revenuestreams!

SUMMARY

Providing services to a new area is veryexpensive for cable operators; however,if it makes good business sense, then fiberis the optimum way to provide connectivity. Aurorahas been pioneering in this space, developing andoptimizing solutions specifically for cable, and fiberto the premises in particular. With our VHubtechnology, the cable operator has an optimalsolution to deploy FTTP today: a solution whichcost-effectively overcomes the limitationsassociated with other approaches. Importantly,with the introduction of our Node PON GEPONmodule and careful wavelength selection, ourRFPON solution provides the cable operator withan evolutionary upgrade path capable ofsupporting all-IP full-duplex servicesoncejustified by the potential revenue opportunity.Aurora Networksworking with cable operatorsto break access barriers.



Aurora Networks, Inc.5400 Betsy Ross DriveSanta Clara, CA 95054Tel 408.235.7000Fax 408.845.9043www.aurora.com

Aurora - Whitepaper014 Reva Rfpon

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