Advantages of Fiber Optic Transmission

There are many advantages to using fiber.  In this section below we will discuss the many key benefits.  Over the past year the cost of copper cable has increased 4 times.  With the increases in copper wire, fiber optics has become even more desirable as a transmission medium.

Longer Distances

One of the biggest benefits of fiber optic transmission is the capability to transport signal a long distance.  Basic systems are capable of sending signals up to 5 Km over Multimode fiber and up to 80 KM over Singlemode without repeaters.  Most modern fiber optic systems transport information digitally.  A digital fiber optic system can be repeated or regenerated virtually indefinitely.  An electro–optical repeater or an erbium doped fiber amplifier,  EDFA, can be used  to regenerate or amplify the optical signal.

Multiple signals

As discussed in previous sections, fiber has a bandwidth of more than 70 GHz using typical off the shelf fiber optic transport equipment.  Hundreds, even thousands of video and audio signals can be transported over a single fiber.  This is achieved by using a combination of time-division multiplexing, TDM and optical multiplexing.  Fiber optic transport equipment is readily available to transport more than 8 video and 32 audio channels per wavelength.  Off the shelf coarse wave-division multiplexing CWDM equipment easily provides up to 18 wavelengths.  This combination of equipment provides up to 144 video and 576 audio channels as shown in figure 11.

Time-division and Optical Multiplexing,  Figure 11.

Size

Fiber optic cable is very small in diameter and size when compared to copper.  A single strand of fiber optic cable is about 3 mm.  A video coaxial cable is about 6 mm.  Fiber cable facilitates higher capacity in building conduits.  There is often limited space in existing building conduits for infrastructure expansion.  In mobile and field productions for sports and news events, fiber is the cable of choice due to space limitations in mobile and electronic news gathering vehicle.  Fiber is often the only possible choice due to these size and space issues.

Weight

The size and materials in a fiber optic cable are drastically lighter in weight than copper cable.  Copper cable can weigh more than 10 times the weight of fiber optic cable.  A single core of PVC jacketed fiber weighs about 25 lbs per Kilometer.  A RG-11/U coaxial copper cable weighs about 300 lbs per Kilometer.

Weight becomes a factor when suspending cable from poles.  Weight is an important factor in mobile and news applications.  The Department of Transportation enforces strict weight limitations on all truck and mobile vehicles.  When a truck is built and loaded with all the required electronic equipment and power generators, there is little weight left for 1000’s of feet of copper cable.  Fiber optic equipment is widely used in mobile production vehicle do the drastic weight savings.

Noise Immunity

A signal traveling on a copper cable is susceptible to electro-magnet and RF interference.   In many applications it is unavoidable to have to route cabling near power sub-stations, HVAC equipment and other industrial sources interference.   A signal traveling as photons in an optical fiber is immune to such interference.  The photons traveling down a fiber cable are immune to the effects of electro-magnet and RF inference.  In Military application, fiber systems are immune to an electro-magnetic pulse, EMP, generated by a nuclear explosion in the earth’s atmosphere.  In the event of a nuclear war, the first wave of attacks would be nuclear atmospheric detonations to generate massive electro-magnetic pulses that would destroy all electronic equipment and communications.  Fiber optic equipment is used in command and control bunkers to isolate facilities and systems from EMP interference.  A fiber optic signal does not radiate any interference or noise.   A fiber optic cable will never generate any electro-magnet or RF interference that would interfere with any other systems.

Easy Installation

One of the myths regarding fiber is that it is extremely difficult to install and maintain.  This may have been true in the early days, but now it is as simple to terminate an optical fiber with a connector as it is to connectorize a coax with a BNC connector.

Easy Termination

Fiber optic termination kits are now available that require no epoxy and special polishing as shown ion figure 12.  Simple cable stripping tools are used, similar to those used for copper coax, to prepare the fiber for termination.  Epoxy free connectors are available to terminate both Multimode and Singlemode fiber optic cable.  The connectors are already pre-polished.  No polishing equipment is needed.

Fiber Optic Connector Termination Kit, Figure 12

Connector types

Over the years as fiber optic communications have grown and changed, there have been many different types of connectors.  Today there are four common connector types that are used in most fiber optic applications.  The first is the ST connector.  It is a bayonet style connector similar to a coaxial BNC connector pictured below in figure 13.
It is available for Singlemode and Multimode application.

ST Connector, Figure 13

The next style is the FC connector.  This connector has a threaded screw type receptacle.  It is similar to an RF F-Type connector as shown in figure 14.  It is only used fro Singlemode applications.

FC Connector, Figure 14

The telecommunications industry standardized on the SC connector.  It is a square snap-in type  connector as shown in figure 17.  The SC connector has gained popularity in the video and computer networking.

SC Connector, Figure 15

Telecommunications and networking applications typically require two fibers.  One for transmitted data and one for received data traffic.  Since SC type connectors were popular in these types of applications, two SC connectors were required. As the size of fiber equipment reduced and the density of fiber optic I/O’s increased, a small alternative to the SC connector was required.  This led to the LC connector as shown in figure 18. An LC is approximately half the size of an SC connector.  It is rectangular in shape and has a locking clip.

LC Connector, Figure 16
Easy Spicing

Another myth is the repair or maintenance of a broken or cut fiber.   The cost of fusion splicing equipment has come down significantly.  A new unit can cost under $7,000 and units are available for daily rental.  The fusion splicer is a small portable device, as shown in figure 17, which is easily carried in the field.  A fusion splice is very easy to perform.  First the fiber is stripped and prepared using simple tools.  The fiber is placed in the fusion splicing machine.   The LCD screen shows the device automatically aligning the fibers.  With the press of a button a fusion arc is generated to splice the fibers together.  The fusion splicer even tests the connection when complete.

Fusion Splicer, Figure 17

There is now an even simple way to splice a fiber in the field, mechanical splicing.  A mechanical splice consists of a small device, pictured below in figure 18, which is used to splice a fiber.  It is about 2 inches long by ½ inch wide.  The process involves first stripping the fiber optic cable and then inserting the ends into the splicing unit with mating gel.  A key is used to close and clamp the unit shot.  The mechanical splice gives fiber installers the ability to splice and repair with expensive equipment in areas where no electrical power is available.

Mechanical Splicing Kit, Figure 18

Fiber optic cable is available in many configurations for just about every application.  Cables are available with multiple fibers from 1 strand to 100’s of strands.  Fiber optic cable is available in configurations that meet all building and installation codes.  There is Plenum rate fiber for installing fiber cable in a plenum space.  There is riser rated cable that can support its own weight for vertical runs through walls in tall buildings.  Tactical and armor rated fiber cable is available for outdoor and military environments.

Radiation and Security

Fiber optic transport is a secure means of communications.  Since a fiber optic cable emits or radiates no RF energy, it is impossible to passively listen or to tap into a fiber optic circuit.  The only way to tap into a fiber optic cable is to physically cutting the cable.  An eavesdropper would have to cut the fiber and install a splitter to tap into the fiber optic link.   The cut in the fiber and the inserted splitter can be detected by fiber optic test equipment.

Environmental Conditions

Fiber optic cable is immune to environmental condition.  Fiber optic cable is capable of tolerating temperature extremes.  Unlike copper cable, fiber is immune to moisture.   Fiber is available with jacketing that is resistant to nuclear radiation.  Many fiber optic systems are used for the inspection of nuclear reactors.   Many Military applications require fiber optic equipment and cable to have resistance to radiation.

Advantages of Fiber Optic Transmission, Easy Installation, Environmental Conditions, Fiber Optic Transport Systems for Broadcast Television, Longer Distances, Multiple signals, Noise Immunity, Radiation and Security, Size, Weight advantage, advantages, Easy Installation, environmental, fiber, longer distance, Multiple signals, Noise Immunity, optic, radiation, security, Size, transmission, Weight