Fiber Optics



Fiber optics is simply a strand of glass or plastic used to contain light signals. Over the past decades these strands have come to be incorporated into a variety of applications in many different fields, from home lighting and theater decorations to more importantly, telecommunications.

How It Works

A fiber optic wire consist of a core made of graded index glass (pure glass), a cladding which reflects the light back into the core, and an outer coating which protects the core and cladding. All of this is place in a single jacket.

Basically fiber optics work by shining a light source in the fiber usually an Light Emitting Diode (LED) or a Laser called a transmitter. The light source travels through the fiber optic core by "bouncing" off of the cladding back into the glass core (the cladding acts sort of like a mirror) until it reaches the other end of the cable (the receiver). This is able to work because of the total reflection principle.
Picture of How Light "bounces" through the fiber cable through total internal reflection.

Benefits of Fiber Cabling In General

Unlike copper cable you don't have to worry about noise on the line or grounding the cable. Fiber cable also has greater distance range, while traditional twisted-pair copper media (UTP) can extend 100 meters per segment fiber media can extend over 2000 meters per segment.

Multi-mode Fiber

The part of the fiber cable which the light travels through is called the core, and different types of fiber optic cables have different sized cores. The glass core on multi-mode fiber which is made of graded index glass instead of the typical silicon dioxide (to allow the light to travel easier) has a diameter between 50-62.5 microns. A diameter of this size allows the "light" within the fiber to take many different paths, hence the name "multi-mode" . However, multiple paths often makes the transmission "sloppy" and causes signal loss over long distances, this is known as attenuation.

Multi-mode fiber is capable of transmitting data about 2km (6,560ft). Light Emitting Diodes (LEDs) are generally used as the light source for multi-mode fiber because they are cheap to manufacture and safer to use then lasers. A circular Subscriber Connector (SC) is used with multi-mode fiber.

Single Mode Fiber

Physically single mode fiber is almost exactly like multi-mode fiber except for the glass core is significantly smaller. The core on single mode fiber typically has a diameter between 8-10 microns and the light source enters the core at a 90degree angle. This basically means that there is a single defined path for the light to travel though the core. This allows for faster data transition over greater distances when compared to multi-mode fiber.

Single Mode Fiber is capable of transmitting data about 3km (9,849ft). This distance is considered the standard however, greater distances are possible, the IEEE has shown that it is possible to transmit data at 2.5Gb/s over 10km single mode fiber using Vertical-cavity surface-emitting lasers (VCSEL’s) (IEEE Photonics Technology Letters). A square Straight Tip (ST) connector is used with single mode fiber.

Although they cost more then LEDs, lasers are typically used as a light source for single mode fiber because of the quality of the light produced. Single mode Fiber is often used for cable TV service or backbones.

Overall, single mode fiber has better quality then multi-mode fiber but more expensive.

Diagram displaying the difference between how light travels through single mode and multi-mode fiber.

Terminating Fiber Optics

Fiber optic termination and splicing equipment includes tools or kits for cutting, finishing and joining fiber optic cables. Fiber optic termination and splicing equipment includes different kinds of connectors and splices to create both permanent and temporary joints between fibers. Fiber optic termination and splicing equipment also includes an optical fiber tool, or slitter, which slices into the cable’s outer coating and unpacks the fibers without damaging them as well as fiber optic cleaners, cleaning chemicals or solvents and cleaner dispensers for preparation of the cut and polished joint or splice.

Fiber optic cables are typically terminated by using connectors to couple the cable to network devices. Fiber optic connectors are specifically designed to limit light loss and provide a secure connection to a device. The most common fiber optic termination connectors have a bayonet mount and a cylindrical ferrule to hold the fiber in place. Other connectors may screw in or snap in to a network device.Fiber optic termination and splicing equipment makes it possible to customize cable to specific lengths and for specific uses. Fiber optics slicing is typically used to repair and restore damaged cables, but may also be used to cut long cables into shorter runs or mix a variety of cable types together.

Fiber optic termination and splicing equipment ranges from simple to elaborate devices, depending on type of fiber splicing. Splicing techniques include fusion splicing or mechanical splicing and are permanent connections between fiber optic cables. Fusion splicing involves meshing or welding the fiber cables by using an electric arc welder. Mechanical splicing involves an alignment device that holds two ends of the cable together while an index-matching gel or glue secures the splice together. Fiber optic termination and splicing equipment, such as the type used to do fusion splicing, can be expensive; but fusion splicing is the most efficient technique when making many splices, and usually results in fiber optic cable with very low back reflections.

A Mechanical Splice is basically a jacket like device that just kind of hold the two fibers together.
external image mechanical_splice.jpg
Fusion Splicing physically "combines" two fibers using heat. Similar to soldering or welding.

external image fusion_splice.jpg

Images From Tecra Tools Inc. 2006



Perhaps the least known application of fiber optic strands is in theater lighting. Many lighting designers find need to create the effect of stars behind a stage. One of the ways to achieve this illusion is by using a fiber optic star drop. The drop consists of a piece of black velvet or Duvatene which is wired from behind with hundreds of fiber optic strands, each terminating through the front of the drop at a random point. The strands all feed into a main light source that is usually attached to the same batten as the drop. When the light source is switched on, the light is refracted throughout the strands, and shows on the front of the drop as a hundred pin pricks of light, much like a starfield.

Ethernet Over Fiber

Ethernet (802.3) is a standard that is typically implemented on copper media. However, it can also be implemented on fiber. This will allow Ethernet to overcome the limitations of copper media such as distance and speed. Fiber has allow Ethernet to transcend from the Local Area Network (LAN) to the Wide Area Network (WAN) as Ethernet has broken the 100Gb/s mark on fiber. (ARS Technica)

Verizon FiOS

Verizon now offers digital cable television, telephone services (POTs Plain Old Telephone), and high speed internet service over fiber in select areas. FiOS operates by running fiber lines directly to each subscribers home know as fiber to the premises (fttp). There is basically a single box on the back of the subscribers home with ports for the Internet, digital cable television, and phone. By doing this the are not only able to compete in the digital cable market they are also able to provide Internet connections much faster then DSL that rival cable Internet.

Package One: 5Mb/s down and 2Mb/s up
Package Two: 15Mb/s down and 2Mb/s up
Package Three: 30Mb/s down and 5Mb/s up

Connection schematic For Verizon Fios Box

Decorative Use

Fiber Optics can be used in the home as decorations, accents, and many other lighting applications. Fiber Optics can be used for very beautiful decorations such as wall mounted pictures.

Mounted Picture*
external image etchglas1.jpg

Fiber Optics can also be used for accent lighting. Such as stair lighting, pool lighting, and glass brick lighting. This is because the strands of fiber completely illuminate when a light source is turned on.

Glass Block Lighting*

Step Lighting*

Pool lighting*
Starting in the early 1900s Americans started leaning more towards artificial Christmas trees. In the 1950s people started having unique trees with colorful lights and tinsel. Now a days its not uncommon to see fiber optic Christmas trees. There are two types of fiber optic trees; one that is tree shaped made of strands of lights and the other is an actual artificial tree but the limbs have multi-colored fiber optic lights.

external image xmas-tree5.jpg

*Pictures above for "Decortive Use" are from: Mica Lighting Company, Incorporated, 1999-2004


Dielectric optical lights were first discovered by John Tyndall, an Irish physicist. Tyndall discovered that by internal reflection light is able to travel inside material and water. Then in 1952 another physicist by the name of Narinder Singh Kapany conducted experiments, based off of Tyndall, which invented optical fiber. In following years research was spent on putting together fiber bundles. In 1956 a group of researchers form the University of Michigan; Hirschowitz, Peters, and Curtiss, patented the first optic semi-flexible gastroscope.
In 1965 a company called Standard Telephones and Cables stated that optical fiber could help with communication. Finally in 1970 the first practical optical fiber used for communication purposes was invented by; Maurer, Keck, Schultz, and Zimar who worked for the Corning Glass Works.
Out in Long Beach, California on April 22nd, 1977 general telephones and electronics were working through fiber optics. Two men by the names of David Payne and Emmanuel Desurvire created erbium-doped fiber amplifier which was used to reduce the cost of long distance fiber systems.
In 1991 the development of photonic crystal fiber was discovered, which was created to allow light through by diffraction from a periodic structure instead of internal reflection. Now a days you can find fiber optics anywhere from medical procedures to inspect the internal body, to automobiles, aircraft, to even holiday decorations.
external image 37e8ca04.jpg
Source- Wikipedia


Total Internal Reflection
Ethernet 802.3
Straight Tip Connector (ST)
Subscriber Connector (SC)
Vertical-cavity surface-emitting lasers
Light Emitting Diode (LED)

Citations / Resources

Wikipedia Entry
The Fiber Optic Association
Cisco CCNA Networking Academy Curriculum Version 3.1
BlackBox Networking Services
Ethernet Breaks 100Gb/s: ARS Technica
Verizon Fios
How Fiber Optics Work
Fiber Optic Splicing Guide
Mica Lighting