As FTTH networks are deployed on a massive scale, fiber will replace the copper wiring in connecting homes and enterprises, bringing radical changes to the last mile of access networks. As a critical and difficult aspect of FTTH deployment, the optical distribution network (ODN), strongly impacts the total cost, system performance and reliability of FTTH networks.
Planning is key
There are three parts in an FTTH network: the optical line terminal (OLT), optical network terminal (ONT) and the optical distribution network (ODN). The ODN is an important component of the FTTH network, providing a physical channel for optical transmission between the OLT and ONU. It is usually comprised of fiber cables, optical connectors, optical dividers, and supporting devices that connect the components. The ODN has five components: feeder, optical cable distribution node, cable distribution part, cable access point and home access.
An FTTH plan covers active devices (OLT and ONT) and a passive optical distribution network (ODN). While topology for active devices is quite simple, ODN is more complex, and a key part of FTTH network planning. Within a radius of 20km or farther from the exchange to subscriber homes, the ODN needs numerous fibers, cables, passive nodes and massive engineering. Statistics show that the ODN cost accounts for 50% to 70% of the total FTTH investment. Appropriate ODN network planning is crucial to effectively guiding ODN construction and reining in the costs.
To guarantee correct fiber routing, ODN planning must fully address considerations in OLT site selection, outdoor connector box location, optical divider location, the utilization of existing pipes and cables and the distribution of target subscribers.
For example, the OLT is generally located in the central equipment room to cover more subscribers with fewer nodes. Resources should be used more efficiently through central optical division in the initial stage when subscribers are widely scattered. Operators must fully consider this situation during actual network construction to maximize ODN resource utilization and readily adapt to capacity expansion requirements. In addition, the architecture should be sufficiently stable and reliable to accommodate future network evolution.
A future-proof ODN deployment underpins sustainable FTTH development. A suitable ODN plan helps to considerably reduce engineering, equipment and operating costs. Most operators draft a detailed network plan with the help of a specialized design institute or advisory body. This helps them prevent project risks and ensure business success.
Quality is prerequisite
Successful FTTH network operations are largely contingent on QoS, which in turn hinges on ODN quality. As part of the FTTH network infrastructure, the ODN must be able to fulfill requirements over the next two decades or longer. As ODN construction involves large amounts of underground work and a long service life, a substandard ODN could incur high costs for reworking and reconstruction.
ODN quality is determined by a combination of product and construction quality. Currently, the Chinese market lacks unified standards for ODN quality. As a result, ODN products from different vendors may vary widely in consistency, reliability, and performance. For outdoor products, their protection level, resistance to high and low temperatures and materials all affect performance and reliability. There is an urgent need for operators to establish a set of unified standards for ODN products.
When it comes to construction quality, ODN engineering technology and processes are a must. For mass FTTH deployment, it is imperative for operators to have well-trained professional engineers, a complete set of specifications and systematic training. Fiber engineering is more sophisticated than copper wire networking. Indoor wiring is particularly a new domain for operators and must accommodate individual user requirements. Suitable indoor wiring guidelines are essential for high-quality engineering.
Currently, operators often use subcontractors and ODN construction is usually divided into two phases: home pass and home entry. As the two phases may be implemented years apart and several construction teams are likely to work simultaneously, it is hard to define responsibilities and trace the causes of problems.
Operators need to establish strict construction acceptance criteria to clearly define responsibilities and guarantee construction quality. In some cases, such as the massive national broadband construction in Singapore, a system integrator or general contractor is selected to oversee end-to-end FTTH network quality. In this way, consistent engineering quality can be guaranteed and the operators' expenditure on managing construction teams kept in check.
New technology for efficient home entry
Operators rely on efficient service provisioning to outpace competitors. In addition to improving customer satisfaction, simple and swift service provisioning enables operators to shift focus away from network equipment O&M to customer experience, further enhancing the loyalty of existing subscribers.
Fiber entry to the home is the first important step in the mass deployment of FTTH for service provisioning. For the sake of efficiency, operators have to provide ODN wiring products and solutions that suit various buildings.
Currently, the industry tends to offer a pre-connected solution for home fiber access. As network size grows, traditional welding can take a considerable amount of time.
When subscribers activate services at different times, operators may need to disassemble equipment repeatedly for fiber fusion and other operations, which in turn reduces activation efficiency and complicates project implementation. By contrast, factory-fabricated connections and fusions can significantly increase onsite productivity and shorten the time for service activation as links can be activated through simple plugging.
The industry has also proposed a number of new solutions to distribute fibers inside a building faster. For example, FTTH indoor cables with a small bending radius can serve wiring needs in a building with many corners. Small-diameter FTTH indoor cables made of anti-friction material can address problems such as a shortage of pipelines and limited distribution space inside a building. A new type of vertical distribution cable can be used directly without welding. Tailored for cable distribution in buildings, these solutions clear the way for distribution and increase distribution efficiency.
Intelligent fiber management supports mass deployment
Over the next few years, exchanges in China market are expected to house over 20,000 fiber lines. As FTTH networks are deployed on a massive scale, fiber management over the last mile will become a key O&M concern for operators. In fact, the error rate of fiber data management in FTTB scenarios has exceeded 20%, complicating fiber maintenance and troubleshooting.
The high error rate is largely attributed to the manual operation of entering passive network information into the database. In addition, fibers must be located and handled manually and efficiency is inevitably impacted, making sustainable network operation and maintenance difficult. To lower maintenance costs, operators need to consider intelligent fiber management solutions early on in the construction phase. Then, problems arising from inaccurate information, like rework in fiber repairs, and difficulties with fiber information maintenance, can be handled.
Spurred by the challenge of the surging number of FTTH fibers, some far-sighted operators and equipment vendors have begun to research solutions.
Huawei has come up with an intelligent fiber management solution called iODN to address the issues caused by manual entry, like heavy workloads and high error rates, providing solid assurance for mass FTTH deployment. The solution is designed to properly manage fiber connections through intelligent fiber management, helping ensure accurate maintenance and troubleshooting, increase maintenance efficiency and simplify O&M procedures. By automatically identifying and collecting data on ODN fiber connections, workloads and errors resulting from manual recording, it gets rid of the hassle of duplicate task dispatching due to inaccurate data. Combined with visualized software running on PDAs and intelligent port indications on distribution devices, the solution supports automatic fiber and port search and location, significantly improving O&M efficiency and paving the way for sustainable FTTH network operation and management.
In summary, a suitable ODN plan lays the groundwork for successful FTTH network deployment, while high-quality ODN deployment sets the stage for future operations. Swift service provisioning is essential for grabbing market share. Most importantly, only effective fiber resource management can sustain the operation and management of large networks.
On June 8, 2010, over 50 fixed network operators attended the FTTH & Next Generation Access Summit 2010 in London to jointly explore ways to "respond to challenges from mass FTTH deployment" and share experiences in mass FTTH commercialization. During the conference, global operators including BT and leading vendors like Huawei demonstrated their ODN solutions for mass FTTH deployment.
BT showcased its solution of deploying optical dividers in large-capacity connector boxes, which can simplify site acquisition and reduce link loss. Huawei unveiled its Easy ODN solution as a key part of its total SingleFAN FTTH solution. The one-stop solution enables operators to accelerate FTTH deployment efforts and move optical access networks forward into an era of easy O&M.