Point-to-point Applications

While residential services are characterized by high volume and low margin, commercial services are characterized by low volume and high margin. Cable operators, with their excellent fiber footprint, are well positioned to offer commercial service solutions at far less cost than their telco counterparts. This is because whenever access fiber needs to be constructed, the cable operator need only construct a few hundred feet of fiber to the node while the telco must construct miles of fiber to the central office. Perhaps this is why some consider the cable operator's optical node the crown jewel of the business.

In a commercial services point-to-point campus interconnection application, buildings can be connected using fiber to create a transparent Layer 2 network. Bandwidth would be rate limited below 1000 Mbps so that anticipated future revenue increases are built into the package. For these high value links, typically it is important to have a demarcation point that can detect disconnections on the handoff port (fiber cuts as well as power failures at the customer premises), to perform loopback testing and perform service assurance functions in order to reduce downtime, and to reduce truck rolls and increase customer satisfaction. In a true transparent LAN service, it is also important that the cable operator does not interfere or have visibility into the customers' traffic. In this case placing an Ethernet switch at the customer premises with an IP address for management would be a violation of accepted security practices as well an intrusive use of IP addresses in the customers' Layer 2 networks.

A very straightforward point-to-point application can be built that is based almost entirely on Aurora's line of SMART Media Converters™. With such a solution, the media converters are demarcation points for the optical Ethernet transport over an existing HFC network (with associated indoor and outdoor optical passives, CWDM multiplexers, demultiplexers, single- and multi-channel filters and 1310/CWDM filters). This solution is a very good fit for low customer density applications. The links in this approach are all implemented with equipment that is Metro Ethernet Forum MEF-9 and MEF-14 compliant, supporting up to 1000 Mbps of transport which can be bandwidth rate limited in 1 Mbps increments. Advanced 802.3ah remote demarcation point monitoring features include dying gasp, link status, remote loopback and physical interface control. This approach is depicted in the following figure.

Figure 1. Point-to-point Ethernet access with CWDM SMART Media Converters

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Aurora also offers a highly scalable solution that provides true transparent LAN service and advanced management features via the IEEE 802.3ah OAM standard. In addition, the system solution is certified by the Metro Ethernet Forum for MEF-9, MEF-14 and MEF-18 and can utilize either dark fiber or lit fiber to deliver commercial Fast Ethernet, Gigabit Ethernet or T1/E1 access services. Scalablility results from use of CWDM, DWDM and TDM technologies to multiply the available dedicated bandwidth over a single strand of fiber. With Aurora's CWDM SMART Media Converters, up to 15 CWDM wavelengths are available for carrying 100 Mbps FastE or 1000 Mbps GigE fiber links with no practical limits for the number of T1/E1 connections carried over these point-to-point links. Using Aurora's Fiber on Demand™, each wavelength pair is divided into 16 time division multiplexed time slots and provides access for 16 dedicated FastE customers. Thus a pair of fibers can service 15 optical node platforms, each node supporting 16 dedicated FastE customers to which it is connected, for a total of 240 FastE dedicated point-to-point customers — all using a single pair of fibers. And with a standard DWDM ITU grid (ITU-T G.694.1 with 100 GHz channel spacing) we have 40 channels with which to work.

As subscriber density increases or fiber becomes scarce, a Fiber on Demand deployment (which uses the DS4004U Optical Ethernet Multiplexer installed in Aurora outdoor node enclosures) provides the required solution. Fiber on Demand supports up to 240 dedicated symmetric 100 Mbps Layer 1 pipes over just two fibers. By leveraging existing HFC infrastructure, fiber-based Ethernet services can be incrementally added to link individual subscribers on an as needed basis. Each DS4004U is capable of supplying four 100 Mbps dedicated links to standard media converter CPEs or a hardened wireless gateway. The DS4004U can be configured with a variety of SFP (plug-in) transceivers, is transparent to IP Layer 2 and higher protocols, and provides low latency for VoIP traffic.

Figure 2. Idealized point-to-point architecture using a Fiber on Demand solution

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For T1/E1 local loop service, Aurora's GT3410A module provides a highly scaleable method of service delivery as it runs over the existing point-to-point Ethernet links. This module is also certified for MEF-9, MEF-14 and MEF18.

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