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As data centres are evolving from 10GbE through to 40 & 100GbE, the need for low loss multi-fibre connectivity is vital. As network speeds increase, the optical insertion loss budgets will become more stringent than ever. Headroom between the loss budgets and system performance is reducing and so then does margin for error. No longer is it okay just to use any compatible looking assembly and hope for the best, all fibre connector losses must be factored in and specified as part of the system design and vendors taken to task over conformance.

With a very typical configuration, identified in Fig.1, the end to end link consists of a patch cord, a cassette (which includes LC adapter at the front, an LC to MTP fan-out assembly inside and an MTP adapter at the rear), an MTP to MTP trunk cable, a remote cassette and a remote patch cord. This simple system, from switch to server will include a total of ten optical connectors and five sections of cable so it’s imperative to minimise losses at each connection point to ensure your network will function as planned. While this style has more connection points, it does provide the very best combination in terms of highest density, modularity, flexibility, versatility and of course, significantly reduced installation times.

Fig.1 Typical  MTP® Cassette & Trunk Configuration

The maximum loss expectation for a standard grade LC connector which is often the cassette’s front interface is 0.50dB, but typical around -0.30dB. For an MPO connector, the losses are higher at a maximum of -0.75dB.

 

Standard Grade MPO/LC Channel Loss

• OM3 LC Interface -0.5dBà CassetteàMPO Interface -0.75dBà 100m OM3 cable (-0.30dB) à Cassette à MPO Interface -0.75dBà LC Interface -0.50dB  = -2.80dB
• OM4 LC Interface -0.5dBà CassetteàMPO Interface -0.75dBà 150m OM4 cable (-0.45dB) à Cassette à MPO Interface -0.75dBà LC Interface -0.50dB  = -2.95dB

 

Whereas a high grade, low loss system will produce a LC connector at -0.20dB, with a typical around -0.10dB and an MPO/MPO connector at maximum of -0.35dB.

 

High Grade MPO/MTP® Elite/LC Channel Loss

• OM3 LC Interface -0.20dBà CassetteàMPO Interface -0.35dBà 100m OM3 cable (-0.30dB) à Cassette à MPO Interface -0.35dBà LC Interface -0.20dB  = -1.40dB
• OM4 LC Interface -0.20dBà CassetteàMPO Interface -0.35dBà 150m OM4 cable (-0.45dB) à Cassette à MPO Interface -0.35dBà LC Interface -0.20dB  = -1.55dB

 

Now compare these channel loss numbers to those allowed in Fig2. and it becomes immediately apparent that there is very likely to be an issue at 10GBase, let alone SR4 and SR10.

Fig2.

Fibre Type	1000 Base – Sx (1Gb/s)		10 GBase – SR (10Gb/s)		40 GBase – SR4 (40Gb/s) 100 GBase – SR10 (100Gb/s)
	Distance (m)	Channel Loss (dB)	Distance (m)	Channel Loss (dB)	Distance (m)	Channel Loss (dB)
OM3	1000	4.5	300	2.6	100	1.9
OM4	1100	4.8	400	2.9	150	1.5

 

What needs to be considered is that uninformed procurement or specification could lead to the cables ordered and installed will compromise the application and your vendor may have provided product that is acceptable within general fibre optic connector guidelines; and so starts the who is culpable discussion.

What makes for a low loss connector?

 

Starting with the connector itself, the variations between a low and standard loss is down to a number of subtle but very important differences. The first is the size, tolerance, concentricity and eccentricity of the fibre capillaries. The fibre connector ferrules are measured in mm whereas hole is measured in microns and tolerances of hole size as little as 0.01µm, that is 0.00001mm, so small deviations can make a very large difference. The concentricity is how central the hole is in relation to the connector ferrule and eccentricity is how elliptical the hole may be. So, considering single-mode core size is around 9µm, it should be unsurprising that minor offsets can bring about major losses in a system. Generally, 1.25/2.5mm connectors such as LC and SC are mated via an In-Line Adapter, where the alignment sleeve needs to be as accurately tolerance as the connectors. Generally, ceramic sleeved adapters provide more accuracy than those containing metal or polymer ones though are mostly reserved for single-mode adapters. The cost difference is almost negligible and worth requesting ceramic sleeved adapters for multimode applications.

 

When introducing MPO/MTP technology, the added challenge is to ensure alignment of all fibres within the ferrule. The spacing between each hole from F1 and F2 through to F12 must be equal and within tolerances. For 24f connectors, two rows require alignment and so brings the X axis and the Y axis into play. Then, for single-mode connectors an 8°angle is shaped onto the end-face of the connector. Note also that the connector alignment comes primarily from the two Pins set to either side of the row(s) of fibre. High grade connectors will include high precision Pins that are chamfered towards the tip for easier lead-in alignment.

 

What about the termination process?

 

Once the specification on the connector has been selected, it must then be terminated, polished and tested correctly to ensure the losses are kept to a minimal. The mechanical fit to the cable is vital to ensure the connector does not slip, rotate or crush the fibre within the cable. Most connectors are held in place with a metal crimp ring and the fibre held in place by way of engineering epoxy. The fibre must be allowed to move within the cable so as the spring action on the connector can operate during insertion. If not, it’s possible and likely that the fibre will break within the connector or micro-bending which causes higher losses. So, the correct cable and connector match along with the correct crimp sets and tooling is imperative.

 

Once terminated and the epoxy is cured, removal of the excess fibre is required and controlled best by laser cleaving. The polishing stage comes next by way of ultra-fine lapping films on high precision polishers. On completion, end-face geometry checks ensure a convex or dome shape has been applied to the fibre – if not, high insertion losses and back reflection is created as the fibre itself must make physical contact with the opposing mated connector. Visual inspection to 400x magnification comes next and finally optical performance testing to qualify the performance grade.

 

Conclusion

When specifying for your network, insisting on Low Loss or Elite grade is the smart option and can help facilitate when planning for future upgrades. Getting to know the cabling system at the component level and working with partners who understand connectivity pitfalls and have the experience and capability to provide best in class network systems.

 

Lite Linke’s optical fibre facility celebrates 25 years and utilises state-of- the-art equipment including Daisi interferometers, Optek Systems Laser Cleaving, Domaille polishers and JGR loss testing. Componentry is amongst the best-in-class and turnaround times are unrivalled for UK/European manufacture.

By Paul Desmond, Managing Director of Leader Optec

Talk to data centre managers and the issue that keeps coming round is how to bolster their green credentials.

Data centres have been one of the biggest growth stories of the last ten years, mushrooming from virtually nothing to consuming anywhere between 3 and 5 per cent of the global electricity supply and accounting for around 2 per cent of total greenhouse gas emissions. This puts the data centre industry on a similar footing to the aviation industry.

In the US, research by the Natural Resources Defence Council recently claimed that 34 power plants, each generating 500 megawatts of electricity, are required to power today’s data centres. It predicts that by 2020 the number of power plants needed will have increased to over 50.

There will continue to be an exponential growth in the number of data centres from the very large ones run by the major Cloud providers to the tens of thousands of other centres supporting business and government.

The challenge is how to make them as energy efficient as possible and one of the key ways to achieve this goal is to make the networking infrastructure as effective as possible.

One important consideration is the amount of space that is required. A typical rack in a data centre used to consume under 2kW of power, but it is no longer acceptable to expect customers to continue ramping up the space they need in order to meet their rising power requirements.

One trend is the increasing popularity of MTP technology over more conventional options. The adoption of MTP hyper high density modular design solutions can have a transformational impact on the efficiency of cabinet space with savings of up to 80 per cent. This translates into five times’ more fibre per cabinet.

While the space saving capability is one important consideration, there are a range of other key benefits in adopting MTP solutions.

Speed is one such factor – the completely tool-less solution can achieve 24 connections in less than a minute compared to up to 40 minutes using a single fibre pre-termination. This can build to 144 fibres in a 1U configuration.

Alongside space and time savings is the cost saving. According to US Conec, every square metre of floor space costs US$ 45,000.

Innovation and flexibility are the key as data centres face the challenge of meeting the world’s storage requirements.

Today’s data centres and those that are in the planning need to do everything they can to ensure they are fully future-proofed and, at the same time, green. They need to be able to meet the voracious demands of the Cloud, Big Data, the Internet of Things and high performance computing.

This means embracing smart solutions to deliver the connectivity, power and cooling necessary.

How a data centre is networked is now high on the agenda to minimise the environmental impact of a facility’s infrastructure. Today’s data centre design centres on reducing wastefulness, something measured by Power Usage Effectiveness (PUE). Managers strive to see how close they can get to zero wasted energy.

No one is underestimating the challenges facing those with responsibility for the world’s data centres as well as their stakeholders who include the likes of Google, Facebook and Apple.

On the one hand, they are having to keep pace with the rapidly increasing bandwidth requirements of their customers – a big enough challenge in itself.

Alongside this they are expected to do everything they can to develop and protect their environmental credentials. Even organisations like Greenpeace recognise the size of the challenge facing the industry. Gary Cook, Greenpeace’s senior IT analyst, called it a “tremendous challenge”, adding: “If the sector simply grew on its current path without any thought as to where its energy came from, it would become a major contributor to climate change far beyond what it already is.”

Ian Bitterlin, one of the UK’s leading data centre experts and a visiting professor at the University of Leeds, says the amount of energy used by data centres is doubling every four years. Analysts are forecasting that data centres will consume roughly treble the amount of electricity over the next decade.

Leader Optec is also responding to a range of other challenges facing the sector. For example, we make a point of using recycled cable drums and work with some of our clients to collect and reuse their drums rather than allowing them to go to landfill.

As a company, we are also committed to recycling other products left after the installation process, and are currently working on the development of a wider initiative to help our customers and partners further reduce their carbon footprint.

The good news is that the industry is very much aware of the challenges it faces and strong collaboration between the various stakeholders will help to ensure that no stone is left unturned.

Paul Desmond is the Managing Director of Leader Optec. The company’s Lite Linke suite of MTP Elite Solutions utilises best-in-class components, bespoke design and UK manufacturing to meet the challenges facing networks.

All of the MTP connectivity, containment and cabling solutions are manufactured from Leader Optec’s headquarters in St Asaph. Products include cassettes and chassis as well as assemblies and accessories.

Tierx Limited have partnered with Lite Linke to supply customers in Middle East and Africa with the complete “MTP® Elite Solutions’’ product range.  Hasan Unsal, Sales Director of Tierx Limited said of the partnership, “Our company has always focused on supplying customers with only the very best in fibre optic products and services.  When looking to distribute an MTP® solution and after extensive evaluation, we found that Lite Linke will provide customers with a high quality, genuine MTP® range way above other products on the market.  This partnership will strengthen our company’s offering to customers, giving us the ability to supply the complete end-to-end solution in fibre data centres’’.  

Paul Desmond, Lite Linke Managing Director commented on the partnership, ‘’Hasan really knows his market exceptionally well and is a highly respected individual and that comes across the first time you meet him. Tier-X will represent Lite Linke in a new region for us and we’re delighted to have their support.’’

Lite Linke’s highly engineered, innovative products are all about Speed and Simplicity which means that no tools are required to be able to install the Lite Linke solution.

Our Push. Click. Connect. Repeat process highlights the simplicity of the products’ design and means everything connects instantly – improving speed, efficiency and ensuring effortless installation every time.