Lesson 2

Buried in Dirt - How Fibers Reach Your Home


    For those of you who may aspire to become an Engineer some day, this is a fun and interesting lesson.  You will amaze your parents and friends with the results of the Lab Experiment.

Next time you are riding as a passenger along the road, be on the lookout for aerial wires and cables in the front or rear of homes and commercial buildings.  Did you see any?  If yes, the construction is from a previous era where utilities like power, telephone and cable TV companies strung wire and cable from wooden or metal poles.  However, most new construction and installations within the past 30 years are now underground installations and nearly invisible unless you know where to look for clues to their existence.  But who gives companies permission to build aerial or underground networks in your city or county?  How do companies know where they can bury new lines to your home, school or business?

  Aerial Power, Telephone and Cable TV Wires   Underground Telephone
Pedestal Terminal

Whether your home or school is served by copper wires or fiber optics, the cables connect your location to the rest of the world, beginning with a "Local Exchange Central Office" that is like a post office for the telephone or cable company.  Signals from the cables serving you are cross-connected in the Central Office to various other cables that connect to "post offices" all around the world.  No, these are not really the Post Office where you mail a letter, we are just using that for comparison.  Rather than sorting actual cards and letters like the real Post Office, the telephone or cable Central Office sorts all your phone calls, Internet sessions, emails and in some cases, your television programs, routing them as electronic signals to and from distant locations.  Central Offices are usually windowless, brick or stone buildings so they can stand up to tornadoes and storms for many years.  In some cases, telephone/cable companies have extended some of the switching equipment from the Central Office to concrete pad-mounted roadside cabinets located near a housing subdivision or business park, but these merely send your calls back to the Central Office for processing.

  Telephone Switching
Central Office
  Remotely Connected Telephone
Switching Equipment Cabinets

Before wide acceptance of cellular phones as a substitute for the old-fashioned home telephone, the method for gathering all messages from customers was to install a wire or optical cable to every home and business.  Even today, most homes still require a wired connection for high-speed Internet and/or broadband television signals (unless they are using a satellite service).  To connect every home and business with a wire or fiber cable is an enormous and expensive effort.  The secret to installing cables and fibers to homes and businesses is in a peculiar thing called the "Public Right of Way" (ROW).

Take a look around the lawn that surrounds your home or school.  Did you know that even though the deed to your property describes the total square footage of your ownership, you may not be able to use all of the property the way you see fit (your parents may not even know this)?  A portion of every property that adjoins (is alongside or abuts) any street, alley or other roadway is reserved for the right of public use and called "Public Right of Way" (ROW).  There is a ROW along both sides of every road ever built to allow installation of utilities such as water lines, sewer pipes, power, telephone and cable TV cables and any other utility pole or sign that is of benefit to the general public.  Just past the edge of the ROW is privately-owned land.  In almost every case, you may not build any permanent structure (such as a building or swimming pool) in the public ROW or any Easement (Easement is described below).  This can be a big disappointment to unaware homeowners when they apply for a construction permit for buildings or pools.  In our Lesson Experiment, we'll discover if this is a problem for your own property.

The ROW is usually described as a distance "from centerline", meaning a specific footage from the exact centerline of the roadway extending into the property on both sides of the street.  For example, a residential street in a subdivision neighborhood may be described as "35 foot off centerline", meaning the ROW extends 35 feet from the centerline toward every house on the block.  Most homeowners don't check on this before buying property and in some cases are shocked to discover the ROW line is halfway from the street to their front window!  However, in most cases the ROW is at the back edge of the sidewalk if they exist.  Below is the proposed ROW for a new street and multiple building lots we will review for measurements.  The dashed line running through the center of the drawing represents the proposed centerline of the street.  The bulb-shape at left is a cul-de-sac, meaning this will be a dead-end street with a rounded portion at the end so that cars and trucks can turnaround to leave the neighborhood.

Right of Way Spec Drawing

The specification above depicts measurements for a minimum of 50 feet of public ROW.  The actual roadway to be constructed is to be a minimum of 28 feet in width.  If we derive measurement from the centerline (C/L) of the roadway, the ROW is to be 25 feet from the center of the road extending toward the homeowners property.  Using our formula below, let's see how much ROW extends from the edge of the street toward a house to be constructed on these new building lots:

  25 ft ROW from C/L (50 ft divided by 2)
minus 14 ft Street width from C/L (28 ft divided by 2)  
equals 11 ft ROW from edge of street toward house  

In this case, the public Right-of-Way will extend 11 feet from the back edge of the street toward the new house.  That means the power, water, sewer, telephone and cable companies can use that 11 feet to bury all their lines to serve the new homes along the street.  That also means the homeowner CANNOT use any of that land for permanent construction, and if they try to plant trees, mailboxes, fences or other items that require digging a hole, they have a high likelihood of cutting or damaging the utilities below.  In some cases, ROW is also reserved along the edge or back of building lots, so it is very important to research this before purchasing any property, as you may end up with unusable land along your property.

In cases of major roads such as State or Interstate highways, the ROW is from some point between the lanes of traffic and may be 100 feet or more.  Again, when you are traveling it can be easy to find the end of the ROW, as telephone poles are usually placed just 1 foot inside the edge of the ROW boundary, so if you see a power pole and fence along the roadway, that is likely very near the ROW boundary.  Nearly every Interstate Highway has a fence along the right-of-way to try and keep small animals off the road, so watch for these in rural areas.  Now you have a new game to play when traveling, "Find the ROW!"

Measuring Right-of-Way

Therefore, for a telephone or cable company to install a wire or optical fiber to your home, a "Right-of-Way Engineer" must review and approve all work orders and designs to ensure the cables are being buried in the ROW and not on private property.  Accidently installing a cable on private property can be very expensive, as the land owner can demand you remove the cable or pay them a stiff sum of money as a penalty, so the ROW Engineer is a very important position in any company.

The good news is that all ROWs are clearly marked on public land records and available at your town hall, city engineering office or state highway department.  Many of these are now available on-line for free viewing so you can research your own property right from home.

As an ROW Engineer, your job would be to research and verify that every foot of the cable installation design drawings from the local Central Office to your home or business is in the ROW, not private property.  This may cover 30 or more city blocks or miles of construction between cities.  In some cases it may be less expensive to install a cable across a portion of someone's private property than to stay in the ROW, so the engineer can negotiate something called an "Easement" across private property.  Unlike public ROW, and Easement is valid only for the utility that negotiates the use, so no one else can install cables without negotiating their own rights to do so.  In some states, the terms "ROW" and "Easement" are used interchangeably, so look for both when researching properties.

Some ROW records also depict known utilities that have already been buried so you can find a space to place the new lines.  Obviously you can't just plow in new cables and destroy the existing lines, so you must use great care in deciding where to bury the lines as to cause no disruption in service for existing utilities.

Once you have developed a set of blueprint drawings to install a cable, the entire project must be submitted to the local governing authority such as city or state engineering departments.  After the project has been approved and issued a "Construction Permit", you can begin construction after notifying all other utilities with cables or pipes where you plan to work underground.

For many years, cables were installed underground using tractors with a back-hoe attachment or hand-trenched by teams of workers using shovels.  This was called "open trench" construction.  The downside was the restoral of grass after filling in the trench, as you could almost always trace the path of the trench for many months by the changes in the quality of the grass.  In some cases, the grass (sod) was removed and replaced and withered quickly, leaving a brown path along the trench line.

Open Trench Construction

However, another method for installing cables especially in neighborhoods with nice, green lawns is a process called "Directional Boring."  With directional boring, a machine punches a hole into the ground at an angle with an extendable rod, boring a hole sideways under and across lawns, under streets and sidewalks, then pulls a flexible tubing back through the hole like threading a needle.  Once the tubes are in place, a fiber cable can easily be pulled underneath lawns and roadways.  Using this process, no lawns are destroyed and there are no trench lines.  The boring rod direction can be controlled from above ground with a device that resembles a remote control for a battery-powered race car, allowing the technician to maneuver the boring tool around objects like rocks or buried debris.

If you keep a sharp eye out, you will see these boring machines in use daily as directional boring has become the deFacto method for installing optical fiber cables underground.  In areas where aerial facilities are more common, optical fiber cables are merely lashed onto exisitng cables and strands.

Directional Boring Machine Remotely Controlling the
Boring Direction

In highly urban areas (major cities), a series of underground conduit systems are already beneath the streets and if any conduits have spare capacity, new cables are merely pulled into place.  Utilities often share conduit systems, but power cables have their own conduits systems separated from communications cables.

Once the cables have been installed, a second team of technicians come along and splices the ends of the fibers together, completing the optical circuit from the local Central Office to your home, school or business.  For more details of this please see Lesson 4  Splitting Hairs- How Fibers are Spliced and Connected to Equipment.

This completes Lesson 3  Buried in Dirt- How Fibers Reach Your Home

OK, now crank up your investigative skills and conduct the Lab Experiment (s) for this lesson by clicking the button at the top right of this page, then proceed to the Lesson Test by clicking the button also at the top right of this page.

Don't forget you can order a sample fiber from a real telephone cable for use in some experiments by clicking ORDER FIBER or button on top right of the Home page.  Prices from $1.00 per fiber.  Great way to earn extra credits in your next Technical Presentation, Science Fair or Merit Badge!

Lesson Test
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