Fiber is a great medium for connecting customers to communication networks. It’s transparent with low attenuation, huge bandwidth and signal distortions are minimal. You know all this. But many service provider don’t translate those characteristics into economic benefit, preferring to stick with a design practice inherited from copper-based networks. There is room for improvement.

In many fiber access networks, active network demarcation technology terminates a service on the customer premises. This device provides valuable information about the service quality. Frequently it also acts as a policing function assuring that customers stay within the boundaries of the contracted service.

You might assume that this is an optimized design practice providing best cost and functionality but I would like to question that. There are two pretty obvious inefficiencies which tend to be overlooked until you take a closer look and start thinking about better ways to implement fiber access services:

• Firstly, the demarcation device on the customer premises is frequently colocated with a customer edge router. It’s not very cost-efficient to have two different network elements with similar functionality side by side. This results in higher expenditure on hardware and also increased cost for installation, provisioning and operation.
• Secondly, let’s assume there’s a problem with the fiber link. A communication service provider (CSP) needs to take immediate action in order to fulfil stringent SLA requirements. A management system for the router or demarcation device will confirm that the link isn’t up and running. However, this issue might be caused by various reasons. It might be the result of an accidentally drawn connector, a failure on an interface card of the router or demarcation device, a problem in a fiber patch panel or a broken fiber on the link. Thus begins a costly and time-consuming root-cause analysis.

The first problem is easy to solve. There are network elements which are optimized to provide a basic customer edge router function in combination with network demarcation functions. A CSP can simplify the customer premises installation by just installing a single multi-layer demarcation device. Done.

The second problem, however, is more difficult. Not being able to do an effective root-cause analysis results in either triggering the wrong action or trying to address all possible failures at once. This results in a time-consuming fault isolation or an expensive repair process – not good for a service provider aiming at high profitability rather than wasting money with useless repair attempts.

So, what to do?

Well, the good news is there’s a simple solution. CSPs can install an optical in-service fiber link monitor which supervises the fiber connection. Such light-weight optical testing solutions use an optical live signal to constantly monitor the fiber integrity independent of the user traffic. As the test signal shares its fate with the user data traveling over the same fiber, a fast detection and isolation of faults at the lowest network layer becomes possible. Even the location of a fault can be precisely determined.

Measurement systems based on optical time-domain reflectometer technology are applied for some time for reactive fault isolation in fiber networks. Following the disruption of a fiber connection, services staff use those systems to locate the break and initiate appropriate repair measures. Those systems, however, are too expensive for in-service monitoring.

Recent innovation in optical components and digital signal processing technology reduces the cost of optical fiber link monitoring solutions significantly. The operational cost savings of link monitoring technology certainly outweigh expenditure. And, today, CSPs can apply in-service fiber link monitors on any link.

Will link monitoring replace active demarcation technology? There are additional functions provided by active demarcation technology such as resiliency, service policing or traffic aggregation. Active and passive monitoring actually complement each other nicely while there is a case for pure active or pure passive monitoring. As passive monitoring is agnostic to user data, it’s most effective with proprietary or fully encrypted data streams or in scenarios in which CSPs simply intend to avoid the cost of an active component at the edge of their network. What`s more, passive demarcation technology can be applied under harsh environmental conditions.

In short, no service provider can afford to ignore this route to operational improvement. The advantages of fiber monitoring, such as immediate fault isolation for faster reaction to network failures, will make CSPs apply this technology on most fiber links. It’s now a vital tool for avoiding unsuccessful repair attempts, being faster back to service and pleasing customers.