JOHN WILLIAMSON FIBRE INSPECTION
MSOs are doing similar things with the Head End Re-architected as a Datacenter (HERD). Use of MPO/MPT technology is also evident in FTTA installations and in FTTH set-ups involving solutions such as Corning’s Opti-Tip.
cabling also raises inspection and test challenges for end users. “User issues are related to handling high-density cable systems terminated with MPO that may have different specifications. MPO connectors come with and without pins, and have different mapping (polarity A, B or C),” continues Cole. “This requires technicians to not only consider which test equipment is needed to interface on to the cable but also what test cords are required where.” “There’s no general labelling convention for different types of polarity,” adds Lavallee. “If you don’t validate this at the time of install, there’s no efficient way to currently trouble- shoot that after the event. You have to unplug it piece by piece and try and figure it out.” COMING CLEAN It turns out that appropriate inspection and cleaning have the same primacy in MPO/MPT connectors as is found with regular simplex connectors. The most common tools are ribbon based cleaners, but Clague says that the ones that are designed for MPO/MTP are usually push and click ‘stick’ type where the ribbon is drawn over the ferrule, rather than the ‘box’ type - as an example Cletop - where you drag the connector along cleaning ribbon. But he cautions that you may have to repeat the MPO/MPT inspect, clean, re-inspect processes a few times in order to shift dirt completely, as it’s not uncommon for a cleaning to simply move the dirt to another part of a MPO ferrule. “Think of it this way: MPO connectors have a larger surface area which means a higher probability
It only takes a small slip or a poor fibre handling technique and you’ve either damaged the end face or got dirt on it
WHO GOES WHERE? In this general environment an
interesting aspect of the FOTE industry is how, prices apart, different vendors differentiate products that ostensibly perform the same functions. At a base level there are FOTE specialisms: not all vendors address the same market sectors. “You will find that different vendors focus on certain user groups performing specific tasks such as certification testing, or verification and fault-finding,” states Cole. “Certification testing is optimised for installation teams building new networks, whereas verification and fault finding is likely to be carried out during commissioning and maintenance.” Coles also reflects that one clear distinguishing feature would be whether to offer dedicated, or modular devices. Lavallee argues that ease of use is a key selling point, with tools having, for example, auto-centring of the fibre, auto-focus, auto-capture and auto-analysis. Automation and ease of use speak directly to a generally acknowledged paucity of qualified, experienced optical test personnel. “Recruiting technicians can be hard,” states Lavallee. “And the people that you recruit most probably will not come from the fibre optic world, but from other fields of work.” Clague agrees. “Inspection scopes need to become highly automated - a one button test or even no button test. Think of an auto detection of a connector being inserted for test which automatically triggers the whole process.” A follow-on from this is that the industry needs tools that support repeatability, providing the same test results for the same types of network set-up. Further, these tools should give the same results whether they are in the hands of new operatives or experienced technicians. Viavi adds a slight caveat to the ease of use and automation mantra. “The trick here, though, is how to make the whole process quick and easy with minimal tedium, so that it’s more likely for someone to actually do it,” reasons Clague. The ability to tackle a range of equipment configurations and layouts also scores highly. “More and more distribution panels are getting denser, so there are more connectors per footprint,” says Lavallee. “You need a tool that gives you good accessibility so that you can easily access all the connectors in the patch panel.”
DOUGLAS CLAGUE, SOLUTIONS MARKETING CIVT, VIAVI
of contamination,” he reports. “The probabilities of contamination scale exponentially, so if in a 12-fibre connector fibre number 1 has a 95% chance of being dirt free, the others are 55%. The point here is the same that you will end up doing more inspect and clean cycles for MPO.” The demands and challenges associated with installing, inspecting and re-jigging MPO/MPT links were initially of most consequence to datacentre operators. Today, though, as Lavallee remarks, the multi-fibre technology has spread its wings, in part due to the growth of interest in datacentre type operations in different sectors. For example, telcos are revamping the central office as Central Office Re- architected as a Datacenter (CORD), and
In simple terms, achieving the correct polarity in optical networking is to do with making sure signals correctly travel from required transmitters to required receivers. With MPO/MPT technology, where fibre counts in connectors can range from 8 to 72 (or above), getting a handle on polarity is challenging. The US Telecommunications Industry Association (TIA) has standardised on three different MPO/MPT polarity methods – A, B and C. POLARITY NEEDS CLARITY?
As described by Clague the differences are as follows:
A is straight through connection, pin 1 goes to pin 1, 2 to 2, and so on;
B is full transpose, where pin 1 goes to pin 12 (for a 12-fibre connector), pin 2 to 11, pin 3 to 10 and so on;
C is transposed pairs where pin 1 goes to pin 2, pin 2 goes to pin 1.
Clague says types A & B are mostly used in structured cabling environments where you have backbone cabling linking two patch panels and then a patch cord from panel to end device. He adds that type C is for special use cases, for example where you might be delivering or providing a 10G or 100G circuits/links directly between transmission equipment. The three polarity schemes certainly add interconnect flexibility, but there’s a price to be paid. “Around 30% of the people handling MPO cables report having problems and confusion with link polarity types,” comments Lavallee.
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ISSUE 17 | Q2 2019
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