Protecting the Integrity of Municipal Fiber Optic Networks

The most common multimode optical fibers, which allow multiple light modes to propogate along the link simultaneously, are designed with a core diameter size of 50µm for for high-speed communications networks.  You may recognize these types of fibers by industry specifications such as OM2, OM3, and OM4 or by brand names like Corning® ClearCurve® and OFS® LaserWave®.

 

However, for applications that require greater power transmissions using a high-power laser source, multimode fiber with a larger core diameter is a more suitable approach.  For example, a continuous-wave laser with power of 50W or above would require an optical fiber with a minimum core diameter of 100µm.

 

One important characteristic of a fiber is the power handling ability, measured in Watt/cm2.  For silica core fiber, its limit ranges from a few hundred KW/cm2 to 1MW/cm2 depending upon the glass type and dopants used1.  As the fiber's effective area increases, the ability to transmit a source with a higher power intensity also increases.  Thus, a large core fiber is the ideal choice for some medical (theraputic, surgical) and as well as some industrial (welding, cutting) high-power lasers.

 

To visually demonstrate the core size difference between a standard 50µm multimode fiber and a 100µm large core multimode fiber, see Figure 1 below:

 

 

Similar to the standard multimode types, large core fibers are also manufactured and optimized for operation at the 850nm and 1300nm wavelengths.  Below is a table showing some of the most common core/cladding combination offerings for large core fibers:

 

Core (µm)    Cladding (µm) In order to meet the growing needs of the local community, many municipalities have chosen to make significant investments to both deploy and maintain their own fiber optic networks for communications relating to a number of important areas:

 

Emergency services (Police, Fire, and 9-1-1 departments)

Government facilities

Educational facilities

Healthcare facilities

Transit and traffic cameras

Utilities

Business/Enterprise

Each one of these entities plays an important role in helping a community to thrive in terms of a growth, health, and/or safety perspective.  In general, all data is sensitive to a degree, but with communications for things like emergency services being absolutely critical, protecting that data while maintaining the overall performance is a major challenge faced by each municipality.

 

While hardware and data come to mind when thinking about maintaining an advanced fiber optic network, it’s just as important to consider the physical infrastructure that is relied upon to connect everything.  More often than not when an issue arises, it is the result of a problem with the optical fiber in the form of a break, degrading splice, etc.  Also, with malicious intrusion events on the rise relating to data theft of critical service and power grid information, the federal government is mandating a higher level of data protection by some municipal entities in the form of either a fiber monitoring system or data encryption.

 

Traditionally, both data encryption and fiber monitoring systems have been very cost-prohibitive for municipalities, which often have significant budget constraints to deal with.  While encryption is ultimately the best approach against potential data theft, it is very expensive and does not address the physical issues that most commonly occur like fiber breaks, degradations, and so forth.  Likewise, although a fiber monitoring system does not protect the data itself in the manner that encryption will, it does actively monitor and alert the operator in real-time to issues (be it a fault or intrusion), while helping to minimize service downtimes by identifying the location of the event within the cable.

 

Fiber Monitoring System Example

 

Although fiber monitoring systems in the current marketplace still generally require a significant up-front investment, some vendors are beginning to provide solutions that are much more cost-effective and scalable resulting in a better value proposition to the municipalities.  As opposed to having no solution or waiting an extended period of time to accumulate the large budget amount, they can now more easily deploy a solution to aid in their monitoring efforts from an integrity standpoint, while ensuring a higher level of all-around network performance.

 

There are a number of factors for municipalities to consider when determining the best manner for protecting their local fiber network.  There are many types of encryption solutions if they plan to go that route, as well as several different types of fiber monitoring systems.  Ultimately, the municipality must decide the best fit for meeting their unique network and monitoring needs.

 

If you are interested in learning more about how fiber monitoring solutions work, or you are considering deploying a fiber monitoring solution for your municipal network, you are welcome to contact the experienced team M2 Optics who are available to support you in any manner.

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If you are seeking more information about large core optical fibers, or have a requirement for specialty fibers, contact the engineering team at M2 Optics at your convenience.