JOHN WILLIAMSON FTTHTESTING
GOING FORWARD So what does the future hold for FTTH T&M? It depends who you ask. In the frame, according to Cole, are advances in OTDR technology allowing for greater dynamic range and resolution, and improvements in how test processes are managed using cloud platforms for distributing jobs and collecting results directly from the field. “Keep an eye on fibrescopes as advancements in camera technology have made video inspection more meaningful and economical,” he further suggests. An example is AFL’s DFS1 Digital FiberScope supporting magnified video inspection of optical fibre connector end-faces during fibre optic cable and connector installation and maintenance. The migration from current GPON and EPON to newer PON types such as XGS-PON and NG-PON2, and the co-existence of established and new, will raise some FTTH test issues. “A requirement will be to detect which type of technology is on the network and adapt to that,” ventures Audet. According to Clague, one challenge is that the newer standards like NG- PONs, and especially the P2P services being looked at for business applications or 5G front/backhaul, use longer wavelengths up to and around 1,625 nm where macro-bending of fibres and the associated attenuation of power levels becomes a real problem. “So, what we see as a future requirement, but realistically a requirement for today, is including 1,625 nm in the testing and certification tools and Methods Of Procedure when certifying network build in order to remove future OpEx costs related to finding and fixing macro-bend issues.” The increased availability and use of multi-function test solutions is one of Messina’s suggestions for the future. “We expect this trend will increase with the deployment of next generation 5G networks, where mobile backhaul and fronthaul will require a large redefinition and deployment of higher speeds, with fibre and Ethernet/CPRI/eCPRI/RoE synchronisation testing at the same time,” he calculates. And while not strictly speaking a test development topic, Viavi definitely sees the building and validating of business cases for the use of fibre monitoring solutions in PON as a future business development. “Of course, good ROI for fibre monitoring systems can only be achieved by using it during multiple phases of the network lifecycle,” reasons Clague. “As an embedded tool for build certification, then to identify customer connection to the network during installs in order to trigger service activation, and then the more traditional use of monitoring tools for identifying network outages and pinpoint fault locations to improve Mean Time To Repair.”
Reflectometers (OTDR) are relevant here. Fibre also has a lower tolerance than copper for bending, with the prospect of light going out of the required range and loss of some of the signal if the tolerance is exceeded. Alessandro Messina, EMEA marketing director, IP Network Division, Anritsu points out that this requires the capability to not just detect broken fibres in the access network, but also identify bent fibres through the application of simultaneous double trace, or two different wavelengths, analysis. Some FTTH/B implementations adopt a Point-to-Point (P2P) architecture, others are Point-to-Multipoint (P2MP). In the case of P2MP test complexities increase with the issue of splitter losses. AFL EMEA marketing manager Nicholas Cole remarks that the introduction of splitters makes OTDR testing much more complex due to the large point of loss introduced by those devices. “Each 50% split is equal to a 3dB reduction in power which adds a minimum of 15 dB to networks containing a 1:32 split commonly found in a GPON,” he states. “Legacy OTDRs do not like short links
requirement to correctly identify each fibre at the users’ end,” says Messina.
LABOUR PAINS In parallel with the inherent challenges presented by working with fibre and optical technology, experts say there has been a shortage of suitably skilled technicians able to install and test that technology. “The people in the field deploying the fibre and handling it sometimes have a limited background in fibre testing,” observes Tremblay-Lavoie. “There’s a lot of staffing issues. There’s a lot of training and education required.” One response of the fibre test industry to skills shortages is to add intelligence to remove complexity and to automate test solutions. In this context, Messina instances his company’s Fiber Visualizer, a tool that allows full automatic OTDR testing, where the user is driven step by step and the resulting trace is also automatically analysed to show the events, recognise them, and provide the pass or failed results. One of Viavi’s solutions for reducing the complexity of OTDR operations is the Smart Link Mapper (SLM). This
The people in the field deploying the fibre … sometimes have a limited background in fibre testing
OLIVIER TREMBLAY-LAVOIE TEAM MANAGER, PORTFOLIO MARKETING
with high loss events as they are unable to achieve enough dynamic range whilst maintaining resolution. Equipment vendors have overcome this by designing OTDRs with sophisticated algorithms utilising multi-pulse and automated test modes.” There’s also a customer service issue. “For example, if you are serving 16 customers, and one has a fault, you can’t take the entire network down to troubleshoot that one,” comments Francis Audet, CTO Advisor at Exfo. Audet reckons P2P test may not be a walk in the park either if the connection mixes fibre and, say, vectoring/ bonding over copper technologies, an arrangement necessitating the assessment of different operating parameters. Other problems may arise from the requirement to be able to track and check all fibres when end-to-end testing from the central office to the home. “This includes big challenges because of the distance, the splitting points, and the
takes an OTDR trace and simplifies it to a series of icons representing the fibre link under test. An approach to skills shortages followed by Exfo and others is to exploit better process automation. Exfo’s TestFlow product is a cloud-based process automation and compliance solution. It is designed to simplify tasks for field technicians by breaking down complex test procedures into a step- by-step automated sequence that gives access to the right test parameters and procedures, in turn certifying that network construction and installation jobs are completed correctly and to the right specifications/thresholds. Yet another response is for test houses to become more engaged with network builders or service providers in establishing the initial test methods and procedures to be applied. This, as remarked by Tremblay- Lavoie, might extend to proposing adjustments to network planning or design where the test approach might be judged weak or inappropriate to the particular network or architecture.
| ISSUE 15 | Q4 2018
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