Autumn 2013 Optical Connections Magazine

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Reducing operating expense in fibre access networks

test equipment were deployed. For some operators this group made up the majority of the workforce. For many years there was no option but to invest heavily. With the arrival of digital services, testing became more important and costly when carried out in the traditional manner, even with the evolution of more intelligent technology. To combat this, centralised test equipment and solutions were developed that would enable tests to be performed remotely by lower skilled staff. Additionally routine overnight testing could identify problem areas often before the customer realised they had a problem. With this, operators have reduced the number of technicians, expensive test equipment and training without jeopardising quality. Centralising Fibre Testing Overall, operators have managed to reduce the numbers of staff employed dramatically, by more than 50 percent in many cases and enjoyed the associated OPEX reductions whilst improving customer service. The challenge in fibre networks is to be able to replicate what has already been achieved with copper. Testing fibre is, in many ways, easier than testing copper, with its lower susceptibility to external factors like electrical fields or water. OpticalTimeDomainReflectometry

(OTDR) has been successfully used for many years on installation, maintenanceandfaultfinding.These field units are relatively expensive, requiring skilled operators and only testing one fibre at a time. They also need “out of service” fibres to test, meaning faults must be reported before they are noticed. On top of these less than ideal conditions the Passive Optical Network (PON) architecture of many fibre access networks leads to handheld tests only being performed at customer premises. One advantage of modern PON transmission equipment is that the Optical Line Terminals (OLT) and Optical Network Terminals (ONT) constantly communicate, allowing statistical analysis that will show failings in the electronics and possibly issues with the physical layer. Whilst useful, this does not identify the nature or location of issues. A New Dimension in Access Fibre Testing Advances in OTDR technology, combined with low cost optical switches have introduced a new way to test fibre. By using an “out of band” testing wavelength which does not interfere with the transmission, engineers can test from the OLT or switch end of the PON. In the past it has been problematic to view all customers on PON

individually. Breakthroughs have been made that allow this with very high resolution, even where 128 customers are on one PON system. One OTDR combined with a switch can test many PON systems and reduce the overall cost and complexity of testing. Dirty connectors, ONTS disconnects, micro bends and breaks are all visible. The OTDR systems can also be integrated with GIS mapping software to show the real location of faults and send teams with the correct equipment. The Future’s Bright, the Future Uses Non-Interfering Wavelengths In future, finding faults on PON systemswillnolongerbea“darkart” with armies of trained technicians. Faults that occur will be pinpointed with instant corrective actions. Maintenance will be determinable by routine testing and planned new customer connections will be instantly verified. The cost savings of the adoption of these systems is huge with staff numbersbeingdramaticallyreduced, personal test equipment almost eliminated, costly training reduced, plus a better working system and happier customers. I think this is a goal we can all relate to! Max Penfold International Sales Manager, United Technologists Europe Limited

By Max Penfold T he access network accounts for over 90 percent of cabling in most Telecommunications systems. The big push within the industry now is the transition to fibre to improve broadband speeds and services. This is a major task, as the number of European households set to be connected by 2017 will double to over 40 million by 2017 (FTTH Council). A Challenge for Operators Fibre optics have proved to be very reliable and not prone to failure if properly installed. However, where cables are open to human error, this can change. It is simple to introduce faults in fibres by using poor practice, lack of training or carelessness. In addition to telecommunications staff having access to fibres, with cables laid in the street or on overhead drops, other utilities also come across fibre cabling and unwittingly damage them. To add to these issues, end users now expect a lot from new services and quickly complain when things do not work. Operators will be forced to take a new approach to fault detection to remedy these issues. Not Starting From Scratch Operators have had to overcome similar challenges in access networks over the years. In the early days of copper, vast numbers of technicians armed with a variety of

Optical Distribution Frame + Fibre Test

IP

OTDR Optical Switch Optical Switch

ONT ONT

2x2

1xN

Optical Line Terminal (OLT)

ONT ONT

2x2

1xN

How a centralised typical system topology for a PON management system will look given recent developments in remote testing

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