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Reference Guide To Fiber Optics


Topic: OSP Fiber Optics: Basic Overview Table of Contents: The FOA Reference Guide To Fiber Optics

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What is "Fiber Optics"? 
Jump to:
Which Fiber Optics?  
Fiber, Copper or Wireless?  
Training  
Safety  
Fiber optics refers to the technology of transmitting light down thin strands of highly transparent material, usually glass but sometimes plastic. Fiber optics is used in communications, lighting, medicing, optical inspections and to make sensors. The FOA is primarily interested in communications fiber optics, so this book will focus on that application.
Fiber optic communications began during the 1970s in R&D labs around the world (Corning, Bell Labs, ITT UK, etc.) and was first installed commercially in Dorset, England by STC and Chicago, IL, USA in 1976 by AT&T. By the early 1980s, the first fiber optic telecommunications networks connected the major cities on each coast of the USA and began being installed throughout the world.
By the mid-80s, with the introduction of the first singlemode fibers, fiber’s bandwidth and distance capabilities made it significantly less expensive than other communications media and it began replacing all the telco copper, microwave and satellite long distance links. In the 90s, transoceanic fiber optic cables had replaced satellites between most continents. Now fiber has become cost effective for direct connection to the home.
CATV discovered fiber in the mid-1990s and used it first to enhance the reliability of their networks, a big problem. Not long afterwards, CATV system operators discovered they could offer phone and Internet service on that same fiber and greatly enlarged their markets.
The Internet was first transmitted over phone lines which by the late 1980s were mostly fiber. But as Internet traffic grew with the advent of the web and everyone using email, it soon surpassed voice in traffic volume and found the phone system, optimized for voice transmission, highly inefficient for large amounts of digital data. The Internet with its unique transmission protocols became independent from the phone network, although it often used fibers in the same cables.
As cell phones became better and less expensive, creating a gigantic market for personal communications and portable data access, their backbones were built on fiber optics. Frequency allocations for wireless systems were limited so cellular backhaul used fiber to connect to worldwide phone networks.
Cities started using fiber optics early in the game, connecting schools, data networks from city agencies and public safety organizations first. Intelligent highway systems led to connecting “smart” traffic light into networks that could optimize traffic flow. When worries about terrorism led to the installation of many surveillance cameras around cities, the distance from cameras to monitoring stations was long enough that connecting them on fiber was much less expensive. Today some even offer direct fiber connections to their residents or businesses.
Computer networks (LANs) started using fiber about the same time as the telcos, in the late 1970s. Industrial links were among the first applications as the noise immunity of fiber and its distance capability make it ideal for the factory floor. Connecting graphics displays and mainframe storage links, the predecessors of today's fiber SANs (storage area networks) in data centers,  came next. Today fiber is used in most corporate LANs as backbones, connections to desktops for engineering and graphics workstations and many wireless access points.
Utilities also have become big users of fiber. Practically every pipeline or electrical line has fiber running parallel to it or even inside the wires in the case of high voltage electrical distribution lines. Fiber provides communications over the routes and sometimes even includes sensors that keep track of the performance and problems. The electrical utilities are developing “smart grids” to make their power distribution more efficient and these networks depend on fiber for connections.
Other applications developed too: aircraft, ship and automobile data busses, CCTV for security, building automation systems, industrial networks and machinery, even links for consumer digital stereo!
Today fiber optics is either the dominant medium or a logical choice for every communication system. Costs have been reduced so much that fiber to the home is now cost effective, especially since it can offer services (entertainment as well as communications) that no other medium offers.


Which Fiber Optics?

Whenever you read an article or talk to someone about fiber optics, you need to know the point of view. We're mainly concerned with communications fiber optics, but it's also used in medical or nondestructive testing inspection and lighting. Fiber optics, you see, is not all the same. 

Even in communications, we have "outside plant" fiber optics as used in telephone networks, CATV, metropolitan networks, utilities, etc. or "premises" fiber optics as found in buildings and campuses.Just like "wire" which can mean lots of different things - power, security, HVAC, CCTV, LAN or telephone - fiber optics is not all the same. And this can be a big source of confusion to the novice. Lets define our terms.

Outside Plant (OSP)
outside plant

Telephone companies, CATV and the Internet all use lots of fiber optics, virtually all of which is singlemode fiber and most of which is outside buildings. It hangs from poles, is buried underground, pulled through conduit or is even submerged underwater. Most of it goes relatively long distances, from a few hundred feet to hundreds of miles.

Outside plant cables often have very high fiber counts, up to 288 fibers or more. Cable designs are optimized for the application: cables in conduit for pulling tension and resisting moisture, buried cables for resisting moisture and rodent damage, aerial for continuous tension and extreme weather and undersea for resisting moisture penetration. Installation requires special equipment like pullers or plows, and even trailers to carry giant spools of cable.
Long distances mean cables are spliced together, since cables are not manufactured in lengths longer than about 45 km (2.-3 miles), and most splices are by fusion splicing. Connectors (generally SC or LC styles) on factory made pigtails are spliced onto the end of the cable. After installation, every fiber and every splice is tested with an OTDR.
If this sounds expensive, you are right! The installer usually has a temperature controlled van or trailer for splicing and/or a bucket truck. Investments in fusion splicers, OTDRs and other equipment can be quite expensive.
Most outside plant telephone installs are done by the telco themselves, while a small number of large, specialized installers do CATV, utility and municipal work.

Premises Cabling
premises fiber
By contrast, premises cabling- cabling installed in a building or campus - involves shorter lengths, rarely longer than a few hundred feet, typically with fewer fibers per cable. The fiber is mostly multimode, except for the enlightened user who installs hybrid cable with both multimode and singlemode fibers for future high bandwidth applications.
Splicing is practically unknown in premises applications. Cables between buildings can be bought with double jackets, PE for outside plant protection over PVC for building applications requiring flame retardant cable jackets, so cables can be run continuously between buildings. Today's connectors often have lower loss than splices, and patch panels give more flexibility for moves, adds and changes.
Most connectors are SC or ST style with LCs becoming more popular. Termination is by installing connectors directly on the ends of the fibers, primarily using adhesive or sometimes prepolished splice techniques. Testing is done by a source and meter, but every installer should have a flashlight type tracer to check fiber continuity and connection.
Unlike the outside plant technician, the premises cable installer (who is often also installing the power cable and Cat 5/6 for LANs too!) probably has an investment of less than $2,000 in tools and test equipment.
There are thousands of cabling installers who do fiber optic work. They've found out it isn't "rocket science," and their small initial investment in training, tools and test equipment is rapidly paid back.

Few installers do both outside plant and premises cabling. The companies that do are usually very large and often have separate divisions doing each with different personnel. Most contractors do nothing but premises cabling.


Fiber, Copper or Wireless?

fiber vs copper

The biggest advantage of optical fiber is the fact it is the most cost effective means of transporting information. Fiber can transport more information longer distances  in less time than any other communications medium, as the photo on the left from the late 1970s illustrates so well. 
The bandwidth and distance capability of fiber means that fewer cables are needed, fewer repeaters, less power and less maintenance. In addition, fiber is unaffected by the interference of electromagnetic radiation which makes it possible to transmit information and data with less noise and less error. Fiber is lighter than copper wires which makes it popular for aircraft and automotive applications. 
Wireless was used as a long distance medium until fiber became available, but wireless is limited by available transmission frequencies so it was dropped as a long distance medium. While local wireless has grown exponentially, it uses fiber as a backbone and connection to the international phone system and Internet. 
These advantages makes the use of optical fiber the most logical choice in data transmission.
Twenty five years ago, fiber was just being introduced. It was expensive and required PhD's from Bell Labs to install it while copper wire was easy to install. Today most communications installers do fiber and wireless as well as copper.
Because fiber is so powerful, at today's network speeds fiber still has plenty of headroom and users can look to the future of ten to one hundred gigabit speeds with confidence. Telcos use DSL over copper today but it's very limited in bandwidth over typical subscriber connection lengths and many older copper wires will not support DSL speeds, leading to the adoption of fiber to the home. Copper gigabit Ethernet can work over short cables in LANs or but only if it is carefully installed and tested. 
But isn't fiber more expensive? Telcos and CATV operators use fiber because it's actually much cheaper. They optimize the architecture of their network to take advantage of fiber's speed and distance advantages. In LANs, you need to follow the  EIA/TIA 568 standard for "centralized fiber" to optimize the fiber usage, and then it can be cheaper than copper. Installing the proper fiber today in a LAN will give you good chance of being able to handle new network speeds for years to come. One fiber, FDDI grade 62.5/125,  outlasted 9 generations of copper!   See Networks for more information on how to use fiber.


The Secret To Success In Fiber Optics Is Training!
You wouldn't try to drive a truck or fly a plane without taking lessons. Likewise for improving your golf or tennis game. Well, the secret to fiber optics is training too. With some basic knowledge and hands-on practice gained in a training course, fiber is pretty easy to install.

Where to Get Training?
training

Well, you can start right here at the FOA, of course! This reference guide is designed to get you started and you should have "hands-on" training leading to a recognized certification program like the FOA CFOT to be qualified to install fiber. Check the website of the Fiber Optic Association at http://www.TheFOA.org. for the leading fiber optic certification program in the industry. Finally, take advantage of the training offered by manufacturers and distributors whenever you can, often this training is free or cheap! (but limited to the manufacturer's equipment of course.)

How about Certification?
That's what the FOA is all about. We have hundreds of FOA-approved schools offering FOA certifications. Over 30,000 students have been certified by FOA schools (7/2010.)Around the world, FOA is recognized as the leader in fiber optic education and certification.
Standards
The adoption of any technology depends on having workable standards  to insure product compatibility. Most of what we call standards are voluntary standards created by industry groups. Standards are not "codes" or actual laws that you must follow to be in compliance with local ordinances but sensible guidelines to ensure proper operation of communications systems. Standards are often developed by groups within each country, like EIA/TIA or IEEE in the US, but are increasingly becoming international under the auspices of ISO and IEC.
Standards like EIA/TIA 568 ( from the Electronic Industries Alliance/ Telecommunications Industry Association in the US) which covers all of the things you need to know to install a standard premises cabling network are good guidelines for designs and should be followed to ensure interoperability.
Primary measurement standards like for optical power measurements are set by standards organizations in each country like NIST (the US National Institute of Standards and Technology) and coordinated worldwide.

The only common "mandatory standard" in the US - we call them codes - is the NEC 770 (National Electrical Code). The NEC specifies fire prevention standards for fiber optic cables. Other countries have similar codes for building safety.
If an indoor cable doesn't have a NEC rating - don't install it - it won't pass inspection!
A listing of the EIA/TIA standards is on the website of The Fiber Optic Association. Information on the EIA/TIA standards can be found on the website of most of the suppliers of structured cabling hardware.

More on standards.

 


Before we get started - Safety First!

You might think that eye damage from working with lasers would be the big concern in fiber optic installations. The reality is that high power lasers burning holes in metal or burning off warts mostly have little relevance to your typical fiber optic installation. Optical sources used in fiber optics are generally of much lower power levels (The exception is high power DWDM or CATV systems). Of course, you should always be careful with your eyes, especially when using a fiber optic microscope which can concentrate all the light from the fiber into your eye. NEVER look into a fiber unless you know no light is present - use a power meter to check it - and anyway, the light is in the infrared and you can't see anything anyway!

The real safety lecture will always be about small scraps of glass cleaved off the ends of the fibers being terminated or spliced. These scraps are very dangerous! The cleaved ends are extremely sharp and can easily penetrate your skin. If they get into your eyes, they are very hard to flush out. Don't even think about what happens if you eat one. Always wear safety glasses whenever working with fiber and always carefully dispose of all fiber scraps!

Always follow these rules when working with fiber.
1. Always wear safety glasses to protect your eyes from fiber scraps.
2.
Dispose of all scraps properly. Always use a properly marked container to dispose of later and work on a black pad which makes the slivers of glass easier to spot.
3. Do not drop them on the floor where they will stick in carpets or shoes and be carried elsewhere.
4. Do not eat or drink anywhere near the work area.

Fiber optic splicing and termination use various chemical adhesives and cleaners as part of the processes. Follow the instructions for use (detailed on the chemical's MSDS  - material safety data sheet) carefully. Remember, even simple isopropyl alcohol, used as a cleaner, is flammable.

Read more about fiber optic safety.

Zero Tolerance for Dirt

With fiber optics, our tolerance to dirt is near zero. Airborne particles are about the size of the core of SM fiber- they absorb lots of light and may scratch connectors if not removed! Dirt on connectors is the biggest cause of scratches on polished connectors and high loss measurements!

1. Try to work in a clean area. Avoid working around heating outlets, as they blow dust all over you
2. Always keep dust caps on connectors, bulkhead splices, patch panels or anything else that is going to have a connection made with it.
3. Use special fiber optic cleaners or lint free pads and isopropyl alcohol to clean the connectors.
4. Ferrules on the connectors/cables used for testing will get dirty by scraping off the material of the alignment sleeve in the splice bushing - creating an attenuator. You can see the front edge of the connector ferrule getting black! Use the metal or ceramic alignment sleeve bulkheads only for testing.

Read more about cleaning fiber optic components.

Test Your Comprehension





References
The FOA Reference Guide to Outside Plant Fiber Optics  

The FOA Online Reference Guide to Fiber Optics  
FOA Reference Guide to Outside Plant Fiber Optics
You can buy the printed version of the 
The FOA Reference Guide to Outside Plant Fiber Optics from the FOA eStore or Amazon.




Table of Contents: The FOA Reference Guide To Fiber Optics


 


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