FIBER OPTIC BASICS PART 2

ON-LINE COURSE

FIBER OPTIC BASICS DID YOU REMEMBER TO DOWNLOAD THE

PDF FILE FOR FIBER OPTICS??? YOU WELL NEED IT TO GET THROUGH THIS

COURSE

FIBER OPTICS – INTRO PART 2Now that we have completed Part 1 of Fiber

Optics, in this part we well cover:• Cable protects fibers in the application

environment• Connectors join fibers or connect to active

devices so they can be disconnected for rerouting, testing, etc.

• Splices join two fibers permanently• Hardware provides the mounting, protection,

etc. for connectors or splices• Test equipment checks performance

FIBER OPTIC CABLE

Because of the wide variety of conditions to which they are exposed, optical fibers have to be encased in several layers of protection. The first of these layers is the primary buffer coating, a thin protective coating made of ultraviolet curable acrylate (a plastic), which is applied to the glass fiber as it is being manufactured. This thin coating provides moisture and mechanical protection.

FIBER OPTIC CABLEThe next layer of protection is a buffer, that is typically

extruded over this coating to further increase the strength of the single fibers. This buffer can be either a loose tube or a tight tube. The next layer is a strength member, usually an armored fiber, that can be used for pulling the cable. Finally, the entire cable is covered by a jacket designed to withstand the environment into which the cable is going to be installed.

Tight buffer (a zipcord is shown), distribution and breakout cables are used indoors. Outdoors, loose tube cable is used to allow filling the cable with water-blocking materials to protect the fibers from moisture.

FIBER OPTIC CABLE

CATAGORIES OF FIBER• Tight buffer (Zipcord)

• Distribution

• Loose Tube

• Tight buffer Breakout

CABLE TYPE USAGE CHARTType Application #FibersTight buffer Building cable

Single fiberZipcordBreakout

1-48

Distribution Building cablePlenum

6-144

Loose Tube OSPAerialSubmarine

6-144+

Ribbon OSPAerialSubmarine

72-288+

TIGHT BUFFER CABLE:Tight buffer cable is made in three versions:• Single fiber, usually used for patchcords• Zipcord used as a duplex patchcord for

connecting transceivers or connecting devices together

• Breakout cable, which is simply a number of single fiber cables inside a jacket used for indoor cabling where each fiber is terminated and routed directly to a connection.

TIGHT BUFFER CABLE:• Distribution cable is an indoor cable that has

multiple fibers with a 900 micron buffer coating which can be terminated directly, but lacking the protection of the tight buffer cables above, must be protected by enclosure in a patch panel or box.

• Loose tube cable comes in many varieties for underground, aerial or even underwater applications. It can also be armored for protection against rodents for direct burial.

• Ribbon cable puts 12 or 24 fibers in ribbons and stacks the ribbons to make a small diameter very high fiber count cable. Applications are similar to loose tube designs.

Fiber Optic Cable Selection Criteria

• Cost• Proper for the

application (building, riser, plenum, aerial, direct burial, submarine, etc.)

• Enough fiber for redundancy, upgrades

• Meets environmental requirements

• Choose hardware to fit cable needs

Fiber Optic Cable Selection Criteria

Other factors to be considered when choosing a fiber optic cable are: 1. Current and future bandwidth requirements. 2. Acceptable attenuation rate.3. Length of cable.4. Cost of installation. 5. Mechanical requirements (ruggedness, flexibility, flame retardanct, low smoke, cut- through resistance).

Fiber Optic Cable Selection Criteria

6. UL/NEC requirements. 7. Signal source (coupling efficiency, power output, receiver sensitivity).8. Connectors and terminations.9. Cable dimension requirements.10. Physical environment (temperature, moisture, location).11. Compatibility with any existing systems.

Specifications For Fiber Optic Cable

Specifying the proper cable requires two major considerations: (see next slide)1. How the cable will be installed.2. What environment it will be facing after installation.

These are simply guidelines to consider when looking for a cable for any particular installation. Different manufacturers have different cable designs for applications - and maybe different designs than other manufacturers.

Therefore it is preferable to talk to several manufacturers when choosing a cable, especially in unusual situations.

Specifications For Fiber Optic Cable

Installation Specifications– Tensile load– Bend radius– Diameter/ construction– Temperature

Environmental Specifications - Temperature - Long term bend radius - Electrical codes - Long term tensile load - Flame retardance - Rodent penetration - Water resistance - Crush loads - Abrasion resistance - Resistance to chemicals - Impact resistance - Vibration

CHOOSING THE RIGHT FIBER• Install the best

multimode fiber• Include spare fibers• Include singlemode

fibers in multimode cable

• Include fibers in copper cables (rare)

CHOOSING THE RIGHT FIBER• The standard multimode fiber for over 15 years has

been 62.5/125 - the so-called FDDI grade fiber for it’s bandwidth to support FDDI. There has been a revival of interest in the earlier design 50/125 fiber for it's higher bandwidth performance with VCSELs (up to 10 Gb/s), but it cannot be mixed with 62.5/125! If you choose one fiber, all patchcords must be the same fiber!

• Fiber is cheap - as cheap as kit string! When specifying backbone cables, install lots of spare fibers including singlemode fibers in multimode cables for future high bandwidth applications.

• Sometimes it makes sense to put fibers into copper cables. This is becoming more common when using a combination cable (coax and UTP) for home networks that may include 2 fibers.