A New Twist for an Old Technology
Line Power as a New Spin to Reliable FTTH Power Needs
by: Tony Wilson and Kevin Borders
While new Fiber-to-the-Home (FTTH) deployments are increasing and becoming the preferred choice for Triple Play services, the best means for powering the equipment is still up for debate. The old adage “the more things change the more they remain the same” can certainly be applied to FTTH power. That premise is now being challenged from Mississippi to California, as telcos seek new solutions to best address cost, reliability, and customer satisfaction.
Fiber cable transmission, optical switching, network services, and optical network terminals (ONTs) have advanced dramatically over the last two decades, but until recently, how they are powered seemed to be stuck in the 1980s. Since the fiber optic cable can’t carry electrical current for powering subscriber equipment, optical equipment and phones are normally powered by subscriber-provided AC which is then converted to 12Vdc, all backed by a UPS with a lead acid battery in case there is a commercial power failure.
Compare this to the manner in which the legacy plant is powered: using the -48V supplied across the copper conductors. That school of thought placed the responsibility for powering in the hands of the service provider.
Not so with fiber. Powering fiber has changed who is responsible for powering phone/Intranet and even television service. The large carriers changed the paradigm and moved the responsibility for reliable service over to the subscriber, requiring the homeowner to sign an agreement to accept responsibility for the battery maintenance.
That said, many of the Independent telcos across the country have taken a different approach, focusing on ensuring high levels of customer satisfaction. This has been especially true with the Cooperatives, whose subscribers are also the owners. These owner/customers viewed having to provide an electrical outlet and power for phone service as a step backwards. They also thought that having untrained subscribers provide maintenance of the battery would lead to a less reliable service than the traditional legacy phone service with its “five nines” reliability.
“There didn’t seem to be any viable alternatives out there, but we decided we needed to keep the responsibility of maintaining our network and not rely on our customers to do it for us,” says Dan Richardson, OSP Manager for a west-coast-based telco. The challenge was finding something that had been field tested and didn’t fall into one of the very expensive alternative energy programs. After doing much research, they decided to take a serious look at powering their FTTH using Line Power.
An Alternative Solution Throws Powering a Curve
Network Line Power (NLP), sometimes called “express power” or “span power,” has been used for customer premises POTS phones since the inception of the network. In addition, it has also been used to power remote OSP intelligent devices. But, until recently, Network Line Power hasn’t always been effective, practical, or necessary.
Demands for more stable NLP systems capable of reaching greater distances grew over the last decade as more fiber-to-the-curb and remote DSLAM deployments increased. Refinements and advances in line powering technology and standards since the 1990s led to the development of the more stable, dual polarity ±190V system like the Alpha Technologies CSM 36. Systems such as these are now capable of powering multiple ONTs at distances up to 5 miles over a single copper pair.
NLP uses the existing copper network to deliver power from the Central Office (CO) or a Remote Power Node where a down voltage converter mounted on the outside of the home converts the power to 12Vdc to power the terminal. (See Figure 1.)
The way it works is simple. Power is provided by the telco to the customer over existing twisted copper pair lines. At the CO, commercial bulk rate AC power connects to rectifiers to produce -48Vdc power. Bulk -48Vdc power is delivered to a DC-DC converter for conversion to ±190Vdc. This upstream conversion is highly efficient, with low loss current transmitted over the twisted copper pairs.
At the home/premises, the process is reversed. The cable pairs are connected to a downstream converter that converts the power to usable 12Vdc for the ONT. (See Figure 2.)
The quote from humorist Mark Twain, “The rumors of my death have been greatly exaggerated,” certainly applies to the copper network. While many people have been predicting the demise and obsolescence of copper plant it appears this prediction maybe premature at best; and who would have predicted that its greatest foe, the cell phone, would lend a hand in its repurpose and increased usage.
Increase of cell phone usage has led to persistently steady losses of 5-7% of access lines across the telecom industry over the last 5 years, and has led many to assert that “copper is dead”. “It seemed the demise of our copper plant was a foregone conclusion,” said Eric Hoefer, Stayton Communications OSP Manager. “We had already started the deployment of FTTH and were running into some of the typical problems: unplugged UPS systems, missing batteries, and multiple truck rolls to get access to the residence. Plus, we have some very remote areas where access in the winter is a problem. So we were looking for a solution. Originally, we looked at the line power solution to solve our issues with powering MDU/apartments and duplexes, but realized we had enough vacant copper pairs to do much more.”
“There are a number of factors that cause phone companies to opt for the line power technology, but the biggest factor of all is access to their subscriber’s premises,” says Robert Macaluso, President of Generonix, the upstate NY company that makes the 12V downstream converter. The most common FTTH powering system is the indoor UPS that is powered by an outlet provided by the consumer. When subscribers are not home, the phone company can’t accurately trouble shoot the problem. We spend a lot of time talking to customers about natural disasters that cause extended commercial power outages, like Hurricane Katrina, ice storms, and tornados. And they all expose the Achilles’ heel of the FTTH network: the reliance on local subscriber maintained lead-acid batteries.”
“But the largest and most frequent culprit causing outages is the subscriber who unplugs the UPS in order to use an electrical outlet for other purposes, then forgets to plug it back in. In both cases the battery typically lasts for 8 hours and then dies. The customer doesn’t really know why the phones aren’t working and doesn’t associate an apparatus that plugs into their wall in another room with the phone system. And while commercial power is 96% reliable, (much less than the five nines of the copper network), subscribers aren’t,” cautions Macaluso. “Telcos must respond to alarms, whether they are due to power failures or subscribers unplugging an outlet, hitting a circuit breaker, or not reporting a dead battery. The NLP system relies on the batteries back at the CO or Remote Power Hub, and those batteries are backed by a generator. So regardless of how long commercial power is off, the phone lines are still active.”
There are also environmental concerns with using high numbers of subscriber batteries to power the communications network. Given the current the current UPS model for FTTH, where batteries must be carefully replaced and recycled every 2 to 3 years, there potentially could be millions of batteries introduced into the environment. Lead acid batteries are considered a hazardous material by the EPA, and have specific handling and disposal recommendations.
"Just converting to a longer lasting lithium battery doesn't make the problem go away," cautions Dewain Tennant, President of Site Environmental Acquisition Services, Inc., Benton, Arkansas. "When all the batteries were contained in a central office or managed by the phone company, we had a regulated, controlled and mostly contained situation. With a few hundred million new batteries sitting out there in the environment with a 25-year lifecycle, the phone companies have a whole different problem to deal with now. Lawyers and liability experts are all working feverishly to make sure their clients aren't going to be part of the next Super Fund cleanup of batteries, which could be replaced perhaps 4 times a decade in 200-300 million locations around the country."
Short-Term Twist Pain for Long-Term Gain
With all the advantages line power has to offer, one might think there is a mad rush to change the powering paradigm, but there are some downsides to this alternative approach to powering FTTH.
Many telcos have miles of deteriorated old aerial plant, and the joint pole rental expense is sizeable. Maintaining that asset in many rural areas doesn't make financial sense for their FTTH deployment. Others still have miles of buried air core cable that has problems carrying -48V for POTS service, much less the elevated voltages required for line power. Replacing all the defective spans of this relic with new copper just to use it for powering is a real stretch, even if they can continue depreciating the copper under a different utilization rate.
Many customers whose plant can support line powering still have issues with maintaining both a copper and fiber cable plant. "The reaction to this concept will vary greatly depending on who is in the room," says Ted Burk, President of Tabur Services. "While general managers and operations managers love the idea of extending their recovery on the copper, a cable maintenance manager may not be as thrilled because they have to work on keeping it running! Even though everyone generally agrees that they want to avoid the 'access nightmare' caused by indoor UPS systems, line powering is something that has to be weighed and judged on an individual basis."
Maintaining a copper plant for voice and data is much different than maintaining a conductive pair to carry power. There will be some basic maintenance required, and a cut cable will bring the system to a halt unless the line power is used only as a backup system to the AC provided at the residence. Some companies have used this line power backup approach for customers that cannot afford to lose their communications, for example, banks, nursing homes, and critical care activities. But cost issues have kept this deployment to an exception rather than the rule.
The biggest blocker to purchasing and deploying NLP is the upfront cost differential for equipment. Network Line Power has an upfront cost factor of roughly 3 times the indoor UPS solution and about 2 times the outdoor UPS solution. If you factor in the continued depreciation of the copper plant, battery replacement every 2 to 3 years, and the cost of a single truck roll for outages, then the costs appear more even. But looking only at first cost makes it hard to rationalize line power, despite the advantages of much higher reliability, increased customer retention, simpler installation, less customer intrusion, and a greener solution.
"Nevertheless, the number of customers opting for line power continues to increase on a monthly basis, and the daily number of inquiries keeps us jumping," says Michael Burkhalter, VP of US Telecom Sales at Alpha Technologies. "Some people are more dedicated to guaranteeing 24/7 reliability regardless of cost, while others are waiting for the next generation of cost reduced systems. The Rural Utilities Service (RUS) obviously felt offering an alternative approach was important when they listed the ±190 system and 12V line powered converter as 'acceptable for use' in 2010."
"Line power provides the reliability customers have come to expect from the Telecom network," remarked Neil Olsen, VP of Marketing at Generonix. "It doesn't challenge customers with new and confusing requirements to manage their batteries, and it is the better environmental solution. People who just assume their copper plant isn't worth anything may lose out on the chance to add an old twist to their new technology. They lose the opportunity to strengthen their customer base by providing reliable, easy and green services -- the differentiators that may provide them the edge to compete with cable, wireless, competitive fiber and satellite services. One thing is for certain: the vigorous debate on local power versus line power is sure to continue for the foreseeable future."
Kevin Borders is a Senior DC Product Manager at Alpha Technologies. He has more than 20 years experience in the Telecom and Power sectors, having worked extensively in marketing, sales, engineering, and product management roles at PECO II and Marconi/RELTEC. Kevin holds a BSc in Electrical Engineering from the University of Missouri and an MBA in Corporate Finance from the University of Dallas. For more information visit www.alpha.ca.