Introduction to Fiber Optic
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Brief History of Fiber Optics
Fiber Optics involves the transmission of communications signals over thin
strands of glass or plastic. This technology is not really new since the
concept was originally formulated over a century ago and has been in commercial
use for at least twenty-five years. The first commercial fiber optic
installation was for a telephone system in Chicago in 1976. By the early 1980s,
the first long distance telephone fiber optics networks were operational. By the
mid-1980’s, most of the modern, basic fiber technology was developed and began
to be installed in the communications grid that now handles virtually all long
Technological Advantage of Fiber Optics
A tiny strand of optical fiber can carry more communications signals over longer
distances than a copper cable ten times its width. For example, a copper-based
communications cable with about 1000 pairs of conductors can only carry about 24
telephone conversations a distance of less than 3 miles. A significantly
thinner fiber cable can carry more than 32,000 conversations hundreds or even
thousands of miles before it needs assistance in the form of signal
regeneration. Beyond that, each fiber can simultaneously carry over 150 times
more data by transmitting at different wavelengths of light, if desired.
Because of these technological issues, the cost of transmitting a single phone
conversation over copper wire work is about 100 times more than the cost of
transmitting it over fiber! That’s why fiber has become the transmission line of
choice for long distance communications.
Fiber Optics Applications
Fiber optics are used in many non-communications applications, including
lighting, signs, sensors and visual inspection (medicine and non-destructive
testing). Most people have probably seen at least a fiber optic Christmas tree
or other lighting fixture that uses these versatile and flexible strand of
However, the focus of this introduction to fiber optics is on data
communications applications, including telephony, cable TV, Internet
connections, local area networks, industrial communications and control, closed
circuit video monitoring, alarm and intrusion sensors and multiple other uses,
including significant dependence by the military on this technology.
Fiber optics technology has made significant inroads into many of these
applications and are known to be in over 50% of all local telephone systems,
over 90% of all long distance telephone systems, the majority of cable TV
networks, many video surveillance networks, and most computer network
backbones. While fiber optics technology has not yet become the dominant cable
in desktop connections for LANs, as the cost of fiber continues to come down and
the cost of copper as a raw material continues to rise based upon increased
demand from developing countries, it is assumed by many that eventually fiber
will come to play a dominant role networking desktops, as well.
Benefits of Fiber Optics
Lower Overall Costs
Faster Data Speeds
Longer Transmission Distances
Smaller Physical Size
No Electromagnetic Radiation
Quite simply, optical fiber can transmit more information over longer distances
and in less time than any other data transport medium. Further, electromagnetic
radiation interference (the bane of copper wire cabling) does not affect fiber
optic wire which makes it possible to transmit information and data with less
noise and less errors thereby resulting in faster and more successful data
transmissions. Fiber strands are also much lighter and take up less space than
copper wires and that makes it more suitable for aircraft, automotive, and other
applications in which weight and/or size is a concern.
Bottomline: Fiber Optical Networking is the least expensive and most reliable
method for high speed and/or long distance communications and, just as
important, we are only now scratching the surface in utilizing the potential
bandwidth of fiber. For example, while most networks today rely on gigahertz
speeds, the singlemode fiber used in telecommunications and cable TV has a
bandwidth of greater than a terahertz. Standard systems today can carry up to 64
channels of 10 gigabit signals - each at a unique wavelength and the future for
increased transmission levels is quite bright.
Fiber Optics: Premises Wiring versus Outside Plant Wiring
From an environmental perspective, there are two main types of fiber optics
applications.. “Outside Plant Wiring” (OPW) refers to fiber optics used outdoors
in telephony, networking or cable TV applications. “Premises Wiring” (PW) fiber
optics are basically used indoors. Telephone companies, cable TV companies,
Internet Service Providers (ISP’s), traffic signal vendors/installer, and the
military all use significant amounts of OPW, whether hanging from poles, buried
underground, running through conduits or even submerged underwater. Most OPW is
used over relatively long distances, from a few thousand feet to hundreds of
miles. By contrast, PW involves cables installed in buildings usually for LANs,
telecom, industrial control or security systems. Premise Wiring involves shorter
lengths, rarely longer than a few hundred to a couple of thousand feet, of
mostly “multimode” fiber. OPW, by the way, typically uses “singlemode” fiber to
achieve the greater distances that it requires. Both OPW and PW applications
are unique in the components, the installation methods and the testing
procedures that are used to install and maintain them, but they do share the
basic principles of fiber optic data transmission.
Basics of Fiber Technology
Optical fiber is made up of a light carrying core surrounded by a cladding which
traps the light in the core via of total internal reflection which is all
protected by a buffer or insulation. Most optical fibers are made of glass,
though some are made of plastic. The core and cladding are usually fused silica
glass which is covered by a plastic coating called the buffer or primary buffer
coating which protects the glass fiber from physical damage and moisture. Glass
optical fibers are the most common type used in communication applications,
though some specialized applications prefer plastic fiber strands.
In the above Reflection diagram, the fiber core is made from a material with a
higher refractive index than the cladding which will cause the light in the core
to be totally reflected at the boundary of the cladding for all light that
strikes at greater than a critical angle (which is determined by the difference
in the composition of the materials used in the core and cladding.) This is
what allows fiber cables to transmit data, in the form of lightwaves, along a
bending and twisting cable over miles of distance, if necessary.
Standard fiber optic transmission systems consist of a transmitter which
converts an electrical input into an optical output using an LED or laser diode
as its light source for the cable.. This light from the transmitter is coupled
into the fiber with a fiber optic connector and is transmitted through the fiber
optic cable. At the other end of the cable, the light is then coupled via
another connector to a receiver where a Photo-diode detector converts the light
back into an electrical signal which is then conditioned properly for use by the
receiving equipment. Much like other forms of transmission (e.g., copper wire
or radio), the ultimate performance of the fiber optic data link is determined
by how closely the reconverted electrical signal out of the receiver matches the
input to the transmitter.
Fiber optic systems use infrared light (invisible to the human eye) for
transmitting data because these wavelengths are especially well-suited for
maximizing distance the data can travel in the optical fiber. This is because
the ultra-pure glass that is used in making optical fiber has less attenuation
(signal loss) at wavelengths (colors) in the infrared range, which also happens
to be beyond the limits of the sensitivity of the human eye. The optical fiber,
therefore, has been designed and manufactured to have the highest performance at
these wavelengths, which are shown in the diagram below.
The particular wavelengths used, 850, 1300 and 1550 nm, also correspond to
wavelengths where optical light sources (lasers or LEDs) are easily
manufactured. Some advanced fiber optic systems transmit light at several
wavelengths at once through a single optical fiber to increase data throughput.
This method is called “wavelength division multiplexing.”
Wavelength division multiplexing is not all that complicates. With human
eyesight, one can see many different colors of light: red, green, yellow, blue,
etc., all at the same time. These colors (wavelengths of light) can be
transmitted through the air together and may even mix, but they can be easily
separated using the human eye or even a simple device like a prism. Prisms, you
may recall, separate the "white" light from the sun into the spectrum of colors
that make it up. The input end of a WDM system is much like the sun in this
regard.. It is a simple coupler that combines or multiplexes all of the signal
inputs into one output fiber. The demultiplexer then separates the light at the
end of the fiber. It shines the light on a “grating” which is a mirror-like
device that looks like the data side of a CD and it separates the light into the
different wavelengths by sending them off at different angles much like a prism
would do. Optical devices then capture each wavelength and focus it into another
strand of fiber, thereby creating separate outputs for each wavelength of light.
Current fiber optic systems range from 4 to 32 channels for separate
wavelengths. When utilizing a system with higher numbers of wavelengths, this
technology is often referred to as “Dense” Wavelength Division Multiplexing or
Fiber Optic Cabling
Fiber Optic Cables enclose up to one thousand optical fibers to protect them
against various environmental conditions in which they must operate. For
example, cables installed in trays in buildings require less protection than
buried underground or placed under water. These cables will include
strengthening features such as a strong synthetic fiber called aramid fiber (or
the DuPont trade name “Kevlar”) which prevents the stress of pulling the cable
from affecting the delicate optical fibers.
The outside of the cable is called the “jacket”. It is the ultimate protection
for the optical fibers and will be designed to withstand any extremes of
temperature, moisture and the potential stress of installation. Certain
specialty cables even have a layer of thin metal under the jacket to prevent
rodents from chewing through the cable.
Fiber Optic Connectors
When an optical fiber is to be connected to another fiber or to optical
equipment, it can be spliced permanently by “welding” it at high temperatures
or by applying special adhesives. Or it can be terminated with a connector
that makes it possible to handle the individual fiber without damage. These
connectors tightly align optical fibers to minimize how much light is lost
during transmission. Most connectors use ceramic cylinders (known as
“ferrules”) about 2.5 mm in diameter with precisely aligned holes in the center
that accept the fiber. Most connectors use adhesive to attach the fiber and the
end is polished to a smooth finish. The most common types of connectors used in
fiber optic patch cables are FC, LC, MTRJ, SC, and ST.
Fiber Optics Jobs
The fiber optics industry is growing rapidly and requires many skilled people to
perform a variety of functions. Each function or job has unique requirements
and requires different educational backgrounds.
Fiber Optic Component Design is one job in the industry. Most of those who
design components have at least a undergraduate degree and for components such
as connectors, a relevant degree might be in mechanical engineering. Optical
components such as the fibers, themselves, will require knowledge of both optics
and materials, so college degrees in physics, chemistry or materials might be
the most appropriate. A background in solid-state physics would be helpful for
designing the lasers and other such optical equipment.
Fiber Optic Manufacturing jobs, like any other manufacturing position, will have
differing requirements depending on the technical nature of the job. Some may
require manual dexterity and skills while others may require advanced technical
education to understand the complicated manufacturing processes involved in
Designers of complete fiber optic systems are typically electronic engineers. In
this case, fiber optic components are used in the same way that integrated
circuits are used to develop communications systems.
Fiber optic cable installers must be trained and experienced in the process of
pulling, splicing and terminating these delicate cables. This position requires
more manual dexterity than many other jobs, as well a real understanding of how
the systems work.
Workers who install telephone and cable TV fiber optic networks do much of their
work outdoors. They may have to operate heavy equipment that dig trenches and
lay and/or pull cables. Then they bring the ends of the cables into special
trucks or trailers where lengths of cable are spliced together and tested.
Outside plant installations require more hardware (and, therefore, more
investment.) including pullers, splicers, OTDRs and even splicing vans to
perform this job..
On the other hand, computer and security networks also use fiber cabling which
is installed inside buildings. For these installations, cables are typically
pulled through conduits or laid in cable trays and then terminated near the
equipment. Unlike the significant equipment required for outside installers,
premises installers usually only require a termination kit for attaching
connectors and a simple kit for testing the cable and connection.
Fiber optics, like any fast-growing technology, needs more trained workers. Some
of those workers are trained in high schools and colleges, where general
courses will prepare the potential worker for most any aspect of fiber optics.
All of these programs need qualified teachers, so fiber optics training is also
an important job in the industry.
The fiber optics cable industry is dynamic and fast-growing because it offer so
many advantages over other data transmission methods. As users’ data
transmission requirements continue to grow at a breath-taking pace, the fiber
optics industry is assured of a long and economically healthy growth for the
foreseeable future. It is an exciting time to be in this industry and
NetCablesPlus is proud to play its small part by providing high quality,
low-cost fiber optic cabling to a wide array of users.
Visit the NetCablesPlus
Fiber Optic Patch Cables Page Here...