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PPC blog

Dave Stockton

Recent Posts

PON fiber systems branch again with XGS-PON

Posted by Dave Stockton


In a previous blog I looked at the strong case for NGPON2, a fiber system which offers a minimum of 40 Gb/s aggregate downstream bandwidth, spread across four wavelengths, and a total upstream rate of 10 Gb/s. This successor to the lower capacity GPON system, NGPON2 is a composite Time- and Wavelength-Division Multiplexed Passive Optical Network (TWDM PON) system which uses time division as well as wavelength division multiplexing.

In that way it differed profoundly from the largely stalled NGPON1 system which solely used time division multiplexing. NGPON2 offered an immediate upgrade path to capacity of 80 Gb/s downstream and 20 Gb/s upstream. In comparison NGPON1 was limited to a one-off 4x capacity increase over GPON, but at significant capital cost.

The advantages of composite PON networks

TWDM PON systems offer great flexibility and scalability but the NGPON2 embodiment comes at a price, since it uses tunable lasers at the Optical Line Terminal (OLT) and tunable filters at the customer Optical Network Unit (ONU). This adds to cost and complexity.

Topics: Fiber to the premises, Fiber innovations

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The use of shared infrastructure to deploy fiber networks

Posted by Dave Stockton


Telecoms planners and installers know that new fiber network build costs are dominated by civils works (the installation of basic infrastructure into or above the ground).

The proportion of the build cost varies enormously, depending on circumstances such as the population density, projected uptake, urban or rural environment, and other local factors. Additionally, new in-ground techniques (slot cutting, directional drilling, and mole ploughing) can dramatically cut these costs.

However, where possible, planners aiming to reduce costs will try and remove the need for new civils builds altogether. One way to achieve this is to move into the world of shared infrastructure, sometimes known as "parasitic" technology.

Topics: Design and Install, Fiber to the home, Industrial premises

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How fiber and wireless networks are converging

Posted by Dave Stockton


At first sight, a mobile network and a modern, optical fiber-rich, fixed line network have little in common. They might be seen as competitors. After all, we hear regular stories of consumers "cutting the cord" and meeting all their voice and basic data needs with their smartphones.

In fact, the opposite is true - the growth in data volumes that need to be transmitted quickly around the "mobile" core network cannot generally be met through mobile technologies.

Essentially, this means that the core of a mobile network is made up of fixed line, usually fiber, connections.

The anatomy of a wireless network

Before we look at how fiber and wireless networks complement each other, it is worth taking a step back to look at wireless technology overall. Mobile phones transmit and receive signals in the microwave portion of the electromagnetic spectrum, specifically in the region 872 to 960, 1710 to 1875 and 1920 to 2170 MHz in the UK. Just below that frequency range TV broadcasts are carried and at higher microwave frequencies radar, satellite communication, and specialized applications operate.

This means there is limited capacity for onwards transmission of mobile telephony or data over the electromagnetic spectrum, even if it were to be a technically efficient medium.

Topics: Fiber to the premises, Design and Install, Market trends, Industrial premises

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What’s in a fiber network?

Posted by Dave Stockton


We all regularly talk about Fiber to the Premise (FTTP)/Fiber to the Home (FTTH) networks. But, in an era of specialisation, often we only know about the parts that we come into contact with during our working lives - such as the last drop connection, in the case of installers.

So what’s in an FTTP network and how does it work?

In brief, an FTTP network is made up of two main parts:

  • The physical layer.
  • The active optoelectronics. These can be in the central office, the outside network (if any) and at the customer premise.

The ITU-T standard helpfully defines the extent of a fiber network through the G series of recommendations.

It is G.984.2 that is most relevant here, as it covers GPON networks, and it is PONs I’ll address during this post.

Topics: Fiber to the premises, Design and Install, Fiber to the home

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An introduction to fiber cable pushing machines

Posted by Dave Stockton

Since they were first introduced in the 1980s, optical fiber cables have dramatically shrunk in size. A 96 fiber cable can now weigh 30kg/km (down from 300kg/km) and have a diameter of 7mm, compared to 20mm for first generation cables.

Similarly, 12 fiber drop cables used to connect individual FTTH customers now weigh less than 10kg/km and have a diameter of 1-3mm. These are normally installed into microducts, which typically range in outside diameter size from 3-18mm.

This leads to new challenges for installers when it comes to equipment. Previously cables would have been installed with heavy equipment, such as winches and capstans, or heavy compressors and blowing heads. However, this has four big disadvantages in the last drop:

1. People
It requires multiple operators, pushing up costs.

2. Disruption and mess
Customers don’t want bulky equipment in their buildings or apartments, particularly if it damages their homes.

3. Equipment cost
Operators need to invest in buying or hiring expensive machines to carry out installations.

4. Time
While the cable install itself may not take long, setting up (and dismantling machines) is time-consuming, limiting the number of installs that can be completed in a day.

Topics: Design and Install, Fiber to the home

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Why GPON needs to change - introducing NGPON2

Posted by Dave Stockton


When deciding the best fiber architecture for their network, planners have to make the choice between point to point (P2P) or a passive optical network (PON).

Both have strengths and weaknesses, as we covered in a previous blog

The majority of network operators have invested in GPON and GEPON architectures.

However, since they’ve been installed, predicted bandwidth needs have increased dramatically, meaning that they now need to change.

Consequently, much work has been done in creating a successor to GPON and GEPON, ensuring that PON architectures are able to underpin future, higher capacity networks.

After a false start along the way, the new NGPON2 standard, created by the FSAN group, looks set to achieve this.

Topics: Design and Install, Fiber to the home, Fiber innovations

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Multicore networks – the solution to future fiber bandwidth needs?

Posted by Dave Stockton

Even in the midst of current fiber network rollouts, research and development is continuing on the next generation of optical technology, looking to meet the future fiber bandwidth needs of both FTTH and core fiber networks. In this blog I’m going to look at multicore networks, an area where current research could have a big potential impact on future network design and implementation.

The space paradox

It may come as something of a surprise, but the majority of the optical fiber within networks is quite literally a waste of space! Even more bizarrely, the most modern fibers are the biggest waste of space of all.

This paradox arises because of the way fibers transmit the signal they are fed. It is the relatively small core (central portion) of the fiber that carries the information in the network. The remainder of the fiber (the cladding) is there to provide protection and to bulk up the fiber sufficiently that our clumsy human hands can manipulate it. In the case of earlier, multimode fibers with a 62.5 micron core (and 125 micron cladding diameter), 25% of the cross section area of the fiber is used for signal transmission. This decreased to just 16% of the cross sectional area for 50 micron core multimode fiber and now, in the current G.675C fibers, less than 0.5% of the glass cross section is actually used to carry the signal.

Topics: Market trends, Fiber innovations

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Choosing the right fiber cable to meet the National Electrical Code

Posted by Dave Stockton

In a previous blog, I looked at Standards Organizations, what they do and how they relate to each other. As a follow up this post looks at how installers can meet the specific US National Electrical Code (NEC) regulations by choosing the right fiber cable, and which standards to follow for individual deployments.

The US NEC covers building wiring requirements and is revised and reissued every 3 years, with NEC 2014 the current edition. It lists cables by their application, in line with the relevant ANSI, UL or CSA tests.

Article 770 and UL 1651 testing

For the fiber industry the key part of the NEC is article 770, which covers the installation of optical fiber cables and raceways in public and private buildings. There are exclusions for certain parts of specific industries such as mining, railways and electrical generation where the code doesn’t apply.

In UL 1651 the code identifies the following types of in-building optical fiber cables:

Topics: Design and Install, Regulatory/Policy

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Closing the loop – factors in choosing the right fiber closure

Posted by Dave Stockton

Closures are the housings which contain and protect the individual joints in any fiber system, as opposed to fiber joining (fusion splicing, connectorization and mechanical splicing), which are covered in this separate blog. Given how fragile fiber is, and the potential need to upgrade cables, good quality closures are vital to a successful installation. But what is a closure and what should you be looking for when choosing one?

Types of closures

Basic Closures

At its simplest, a closure joins one length of fiber cable to a different length of the same type of cable. This is sometimes known as in-line closure or track joint. Added functionality is provided by a spur (or branch) joint which divides the cable into two ongoing parts - the main cable and a side or spur cable. There are also end of route closures where the cable is broken out into individual elements for customer or telco connection.

Topics: Design and Install, Fiber to the home, Industrial premises

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Who sets the standards for fiber cable?

Posted by Dave Stockton

In the high-tech telecoms world, the credit for new advances often goes to smart scientists and busy entrepreneurs. However, there is a group of people without whom the whole interconnected machine would fall apart. These are the men and women that generate the standards – the norms – to which a particular item performs and perhaps, even more importantly, defines its interface with other parts of the system.

Most people in the industry have heard about the different standards bodies, but exactly who are these people, what do their organizations do and how do they operate? This blog post aims to shed light on the whole area of standards for fiber cable and provide an introduction to the benefits they provide.

Topics: Regulatory/Policy, Fiber innovations

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