Aurora Networks, Inc.

Transcription

1 WHITE PAPER 14 Aurora Networks, Inc. June 2009

2 RFPON - The Next-generation RFoG Solution Copyright 2009 Aurora Networks, Inc. All rights reserved. All rights reserved. No part of this document may be reproduced, stored in a retrieval system, or transmitted in any form by any means, electronic, mechanical, photographic, magnetic, or otherwise without the prior written permission of Aurora Networks. Aurora Networks, Inc Betsy Ross Drive Santa Clara, CA Tel Fax

3 White Paper 14 RFPON The Next-generation RFoG Solution Abstract Aurora s RFPON system architecture enables the migration of traditional RFoG (RF over Glass) architecture into a system that supports RFoG plus PON (GEPON / GPON / future 10GEPON) services simultaneously over the same fiber (or fibers) to the home or premises. This RFPON architecture builds upon and utilizes the installed HFC fiber infrastructure to feed RFPON fiber services to all areas of the HFC plant, located anywhere between the headend/hub and at distances in excess of 60 kilometers from the headend/hub.. BACKGROUND Do cable operators need to deploy Fiber to the Premises (FTTP) networks to provide all the services demanded by subscribers, both today and tomorrow? Resolutely no! The hybrid fiber/ coaxial (HFC) network, and Fiber Deep in particular, can provide all the needed network capacity and more. However, there are scenarios where it makes sense for cable operators to deploy fiber all the way to the home. In particular, FTTP networks may stop cables competition from securing new footholds and help displace the competition. In rural areas with new builds or extensive upgrades and with low population density, FTTP may prove more cost effective while providing additional operational benefits. Moreover, FTTP may provide new revenue streams more cost-effectively. Specifically, areas of interest could be: New housing developments Rural, low-density areas Multi-Dwelling Units (MDUs) Commercial areas (co-located with residential areas) For a new housing development, the builder can often raise the sale price of the house if it can be claimed that the house is fiber ready. Indeed, in many instances the extra cost of deploying the fiber all the way to the home will be met or heavily subsidized by the builder. FTTP keeps the competition out. For rural, low-density areas (<30 HP/mile) it is always very difficult to deploy an HFC network cost effectively, with many line extenders or similar devices typically required to overcome the loss in coaxial cables to reach remote households. In this case, deploying FTTP brings many advantages: limitless bandwidth potential with very little loss of signal level, reduced operating costs (maintenance and powering) and as system design studies and cost analyses have shown, all for approximately the same or even lower cost than HFC or Fiber Deep deployments. With today s revenue generating unit (RGU) monthly payment potentially in excess of $100, providing service to these low-density homes now becomes viable. MDUs offer another unique market segment (assuming they are an existing development new MDU developments would be categorized as new housing developments ). Depending on the locale, they may attract a commercial, high-bandwidth demand or people who expect and would 3

4 RFPON - The Next-generation RFoG Solution be happy to pay for a superior triple play service. For this application, the fiber can be distributed from the basement of the building and fed to the actual dwelling unit, providing true FTTP. However, there are other MDUs where this is not feasible; for example, in a building already cabled with coax, trying to replace that with fiber may be prohibitively expensive. In these situations, the fiber can be run into the basement of the building and either distributed via coax from there or further split and the fiber fed via elevator shafts (or similar) to wiring closets on each floor, with coax running from those closets to the unit. For business areas, it may be optimum to start with FTTP to provide commercial services via PON, supporting high speed data and telephony. However, many businesses require video as well and this can be provided via traditional RFoG, all on a single fiber. In all these scenarios, the optimal application is an architecture that operates from the same headend equipment as the traditional HFC plant, supports all the same services as HFC with potential for new and innovative services, interfaces with all the same back-office equipment (in the same way) but is actually fiber to the premises rather than the more traditional coax. This solution runs fiber all the way to the premises to serve a single-output mini node customer premises equipment (CPE) so that traditional RF output is maintained, enabling continued use of set-top boxes, DOCSIS cable modems and emtas. This RFoG architecture, first deployed by Aurora Networks in 2006, has been taken to the next level with our next-generation RFoG solution, RFPON. RFPON supports a traditional RFoG architecture but with seamless support for PON services, when needed. Alternatively, Aurora 4 Networks solution is so flexible that one can start with PON and then add RFoG services. This white paper introduces Aurora s RFoG and RFPON solutions, emphasizing how Aurora, with the benefit of numerous field deployments, has developed tools to both solve the inherent issues with RFoG implementations and then provide a smooth migration path to an all-ip access network in the future, or vice-versa. RFoG BUILDING BLOCKS The reference architecture for a traditional RFoG system, from headend/hub, is shown in Figure 1. The reference architecture at the headend/hub site comprises a downstream optical transmitter operating nominally at 1550 nm, optical amplification as required by the topology being served and a wave division multiplexer (WDM) filter for combining downstream and upstream optical signals on a single fiber. It also comprises an upstream optical receiver which receives the 1310 nm upstream optical signals and converts them to RF. In the field, conveniently located between the headend and the end customers, there would be various optical splitters, supporting distances up to 20 kilometers from the headend with each fiber supporting 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 separate the downstream optical signal (at 1550 nm) from the selected upstream wavelength. The downstream optical receiver converts the RF downstream signals from the downstream optical carrier, and the RF signal is then fed via coax into

5 White Paper 14 Figure 1. RFoG Reference Architecture, Highlighting Distance Limitations the home. In the upstream, the RF signal is supplied to an upstream transmitter (with an output at 1310 nm) for onward transmission to the headend. Another emerging upstream wavelength is 1610 nm; the wavelength of choice set by the SCTE standards committee. This wavelength provides compatibility on the same fiber with existing PON and the emerging 10G-PON standard wavelengths. The associated RFoG reference diagram frequency/wavelength spectrum for a typical North America system is shown in Figure 2. This is exactly the same suite of products offered to any subscriber in any area of the existing HFC cable plant, not just areas which are fed via fiber. This results in a completely unified headend, significantly simplifying operation for the cable operator. Figure 2. RFoG Spectrum 5

6 RFPON - The Next-generation RFoG Solution 6 LIMITATIONS OF HEADEND/HUB- BASED RFoG While the system does meet many of the objectives of the cable operator to deploy an HFC-compatible FTTP network, technically this solution has limitations, namely: Limited downstream reach Limited upstream reach Fiber-intensive While the downstream reach is important, and limited by the power which can be launched into the downstream fiber, the system limitation will be driven by the upstream. The major cost element in the system is the RFoG CPE and its associated laser diode for return transport, hence minimizing the cost of this component is important. To overcome the upstream loss budget of db, a 20 km 32-split system with a fully loaded return band (i.e., four DOCSIS channels to support DOCSIS 3.0, plus an additional VoIP DOCSIS channel), and a high power upstream laser would be required (on the order of 10 dbm), which is costly; this is clearly not the direction to go for any type of CPE. Alternatively, an upstream receiver technology breakthrough would be required to achieve the very low input levels required by a CPE using a cost-effective low power laser, assuming acceptable carrier-to-noise performance. A 1610 nm laser does provide PON compatibility, and technically can provide the higher optical power; however, this is a more expensive unit. Aurora s upstream receiver solution supports a 24 db loss budget at 1610 nm and 25.6 MHz load with just 3 dbm RFoG CPE transmitters without special provisions or modulation techniques and is compatible with any directly-modulated laser RFoG CPE. There are other solutions being proposed, namely FM and digital links from the CPE, but they do not offer the same compatibility and flexibility to the operator. Aurora can provide a traditional headend/hubbased RFoG solution. However, depending upon actual equipment and network configuration, the reach will only be in the kilometer range. Unfortunately, this greatly impacts the area which can be served directly from the cable systems headends/hubs. In a typical RFoG deployment, each fiber would serve up to 32 subscribers. For example, in a 256 home service area, a cable operator would need to dedicate eight fibers from the headend/ hub to that area to ensure service to each subscriber. Similarly, with these direct fiber runs from the headend, there is no practical method to provide any redundancy in the system. With the growing importance of high-demand, highrevenue services, lack of redundancy is not an ideal solution. AURORA NETWORKS VHUB-BASED RFoG SOLUTION Aurora has pioneered technology which efficiently overcomes all the limitations of an RFoG system: the VHub. The VHub houses a fully operational hub in a standard node housing. In this application it is designed to serve 256 subscribers. Effectively, it moves the functionality of an indoor hub to a weather-proof node enclosure that can be deployed closer to subscribers in the network. The same can be achieved with the OTN configuration so prevalent

7 White Paper 14 in xpon deployments, but the VHub solution avoids requirements for permits and rights of way access as well as land acquisition costs while, at the same time, providing higher granularity, scalability and security. VHubs can be strand or pedestal mounted. The key VHub features for this application are: Support for up to 12 plug-in modules (forward path EDFAs, return path receivers, integrated forward/return wavelength management modules with or without return path receiver functionality, digital transceivers and transponders, optical switches, monitoring transceivers and optical multiplexers) Monitoring and control of the VHub via our Opti-Trace EMS software Redundancy and route diversity with switching times less than 10 milliseconds (typically <5 milliseconds). The Aurora VHub-based RFoG architecture is shown in Figure 3. The VHub system has been successfully deployed world-wide for over five years in many different applications and configurations. In addition to its flexibility in placement it can be located very deep into the network it overcomes the limitations of the RFoG headend/hub-based reference design by: Downstream reach. With forward path EDFAs packaged for installation in this housing, the downstream reach is no longer limited. Upstream reach. At the VHub, the return signals are processed from an analog to digital signal format. With Aurora s standard digital return technology, the upstream reach is no longer limited. With the VHub configured with upstream analog return path receivers, the subscriber CPEs only need to transport back to the VHub, a very short distance of typically no more than about 5 kilometers. With analog receivers in the VHub, effectively 64 subscribers can share Figure 3. VHub: Overcoming the Limitations of RFoG 7

8 RFPON - The Next-generation RFoG Solution the upstream bandwidth. Once received, the upstream signals are then fed into two 2- fer digital return transmitters, each transmitting on one of 15 CWDM wavelengths. Use of the digital return overcomes the distance limitation (now with a reach >60 kilometers) while use of WDM technology provides a very fiber-efficient solution. (Aurora s white paper titled Digital Return Technology provides more detailed information.) Fiber-intensive. With the traditional RFoG approach, one dedicated transport fiber is needed for 32 subscribers. With the VHub, this is reduced to one transport fiber for 256 subscribers, with the forward and reverse wavelengths sharing the same fiber. The traditional approach needs eight times more fiber. In addition, with the VHub, the existing HFC fiber can be shared with the RFoG wavelengths. With Aurora s various O - band and C -band multi-wavelength technologies, a previously used fiber can be freed up for this application. Route-redundancy option. Aurora s hardened VHub-based optical switch provides route diversity with switching times less than 10 milliseconds (typically <5 milliseconds). The only way to provide route redundancy with traditional RFoG is to build two separate systems. In addition, Aurora has developed integrated passive wavelength management modules, simplifying input/output connections to the network that are housed in the VHub. In particular, one module provides a combined optical splitter for the 1550 nm broadcast signals together with 1310/ 1550 diplex filters. This compact design, with 8 MPO connectors, eliminates most fiber jumpers and minimizes associated losses that are normally created by broadcast splitting and/or 1310/1550 (or 1610/1550 as-needed) mux/demux functions. This integrated module not only saves precious VHub real estate but the removal of many of the jumpers improves reliability and also greatly simplifies the installation and maintenance of the unit. Taking this to the next-level of integration, Aurora has consolidated the return path receivers into the integrated passive module while maintaining the same module form factor. This further simplifies operation and opens VHub slots which can be populated with other modules. Today there are eight fibers from the VHub, with each fiber able to serve up to 32 subscribers. (These subscribers can, of course, be either residential or commercial.) RFPON: EVOLVING RFoG WITH THE ADDITION OF PON When making the investment to deploy FTTP, it has already been stated by some that it is critical that there exist an established path to take the network from its current cable TV form of today to an all-ip world that will be needed for future generations. Aurora s RFPON solution provides that evolutionary path, enabling a step-by-step, area-by-area upgrade with its award-winning Node PON technology. The choice of an upstream wavelength is not arbitrary; the 1310 nm solution of today is more cost-effective given the wide availability of components (both active and passive) at this wavelength. However, 1610 nm is potentially more

9 White Paper 14 future-proof; it permits an optional overlay with either an IEEE 802.3ah (EPON, or GEPON) or an ITU G.984 (GPON) system, given that both these systems use 1310 nm for upstream data communications. An additional factor in selection of the 1610 nm wavelength is its compatibility with the emerging IEEE 802.3av (10GEPON) system which is heading towards standardizing on 1577 nm downstream/1270 nm upstream, but this currently remains a work-inprogress. Meanwhile, other options can be made available upon request, such as a 1590 nm upstream path already in use by several cable operators worldwide. The new wavelength frequency/content plan is shown in Figure 4. Figure 4. RFPON Supports the Best of Both Worlds GEPON SOLUTION Aurora Network s Gigabit Ethernet Node GEPON Module, the GE4132M, is an OLT module designed to work in all our VHubs and nodes, making PON delivery from an outdoor platform a reality. Using this OLT module, cable operators can costeffectively add all-ip services to their networks on a service area by service area basis, operating in parallel with traditional cable TV services that are transported over the 1550 nm and 1610 nm wavelengths. Ultimately, but only if and when justified by revenue growth, Node PON equipment can enable full migration of an installed HFC network to a standards-based GEPON FTTP network. With a VHub which can support one, two or three Node PON modules, the dedicated IP-bandwidth to a group of 256 subscribers can be as high as 3 Gbps full duplex. (This is in addition to all the traditional cable TV services that are received from the traditional RFoG deployment.) Of course, the CPE device at the home will also need to be upgraded to support the new PON services. However, by adhering to the widelydeployed GEPON standard, the expectation is that the additional CPE device would be costeffective, with costs driven down by wide-scale deployment. Going one step further and eliminating the RF overlay would allow five Node PON modules to be supported up to 5 Gbps dedicated bi-directional bandwidth to 256 subscribers. With future generation support for the evolving 10GEPON standard, bandwidth potential is almost limitless. This is truly a futureproof solution. Today Aurora Networks is the only company to provide this seamless evolution from an HFC architecture to a full IP-based network on a 9

10 RFPON - The Next-generation RFoG Solution service area by service area implementation. In addition, there are notable key features for our Node PON solution: Fully-compliant with the GEPON standard compatible with off-the-shelf GEPON CPE devices Today s bandwidth is 1000 Mbps bidirectional Each module can support up to 64 subscribers Designed to fully interoperate with existing DOCSIS cable modem back-office provisioning systems. PRACTICAL EXAMPLE The following example, shown in Figure 5, examines how a cable operator could use Aurora s RFoG and RFPON solutions to serve a rural area. Initially this deployment is viewed as an extension of the installed HFC network. The VHub would be located at a convenient place, being served from the same headend equipment and Figure 5. Serving a Rural Area 10

11 White Paper 14 provisioning system. If no route diversity is required, the VHub would be served by just one fiber from the nearest fiber node. If the broadcast and narrowcast services are not available on the 1550 nm wavelength, then the appropriate transmitter 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). From the VHub, today there would be eight fibers, each connected to the appropriate splitter, to service the widely-distributed homes in the area. If the cable operator is looking for a future-proof solution, it is recommended that 1610 nm rather than 1310 nm be adopted for the upstream signal. The downstream services (broadcast TV, downstream data and VoD traffic, etc.) are carried on 1550 nm with all the associated upstream traffic on 1610 nm. (The CPE device would also need to mirror these wavelength selections.) Once network capacity demand exceeds that available, as a next-step a Node PON module can be installed in the VHub, introducing dedicated IP services. The corresponding CPE would need to be upgraded to service the PON infrastructure. (Typically, GEPON-ready CPEs will not be deployed until a subscriber has signed-up for those services; this considerably reduces the upfront capital cost.) The frequency/channel plan for both the traditional and the IP services is shown in Figure 4. With the Node PON seamlessly integrating with DOCSIS provisioning systems, the introduction of this new technology does not cause disruption to back-office processes and procedures. Additionally, with each Node PON supporting symmetrical bandwidth of up to 1 Gbps, this solution is also compelling for providing service to businesses which are co-located in the same rural serving area. This could result in the cable operator having a unified network for both residential and business consumers with minimal capital expenditure and no additional operating expenses and while gaining additional revenue streams! SUMMARY Providing services to a new area is very expensive for cable operators; however, if it makes good business sense, then fiber is the optimum way to provide connectivity. Aurora has been pioneering in this space, developing and optimizing solutions specifically for cable, and fiber to the premises in particular. With our VHub technology, the cable operator has an optimal solution to deploy FTTP today: a solution which cost-effectively overcomes the limitations associated with other approaches. Importantly, with the introduction of our Node PON GEPON module and careful wavelength selection, our RFPON solution provides the cable operator with an evolutionary upgrade path capable of supporting all-ip full-duplex services once justified by the potential revenue opportunity. Aurora Networks working with cable operators to break access barriers. 11

12 RFPON - The Next-generation RFoG Solution Aurora Networks, Inc Betsy Ross Drive Santa Clara, CA Tel Fax