Optical fiber cables are constructed differently from copper cables. It is not enough to make a sound mechanical connection between the fiber and the connection hardware, as with a copper conductor connection. The fiber core must be aligned precisely with the fiber core of the con- necting cable or hardware. This ensures the maximum transfer of light pulse energy is
obtained.
• Light pulses in optical fibers are generated by : • LED’s
• Lasers • Vesels
• Optical fibers offer a much lower signal loss than copper cable so it is often used for long runs. It is also immune to EMI, RFI ( noisy environments)
CONNECTORS:
The two most widely used connectors in use today are: • ST
• SC
ST Optical connector:
The ST style connector is the older of the two. It is used in Audio, Video, and Data applica- tions. The connector is built around a cylindrical ferrule. The construction of the ST is a keyed spring loaded bayonet sock-
et.
Losses: .3 -to- .75 dB/ connector
SC Optical connector:
The SC style connector is also built around the same cylindrical ferrule as the ST style connec- tor.
The construction or design of the SC surpasses that of the ST. The SC has a push / pull design for mating of the two fibers.
It has a housing around the ferrule for added protection. It also has a Non-Optical Disconnect which allows it to withstand pulling forces on the cable and not lose any optical power.
COMPATIBLE ST Vs THE SC CONNECTOR
The duplex SC connector has been recommended by the TIA/EIA 568-A Commercial Building Telecommunications Cabling Standard as the choice for the connector
interface at all cross - connections and outlets.
The SC connector was chosen because it is easy to duplex, to ensure polarity and prohibit the reversal of transmit and receive. Other factors were size, cost,and ease of field termination. The culmination of these factors resulted in the duplex SC,or T568SC,being adopted as the connector of choice for building cabling.
The 568SC has a push - pull latching mechanism. This allows it to be duplexed for easier mating than a bayonet style ST connector. The user may terminate the fiber on the cabling side of the connector hardware or outlet with a simplex SC connector and place them into a duplex adapter, in effect, this duplexes them.
The 568SC has an Non-Optical disconnect feature designed in for use with patchcords.
Non-Optical disconnect means the subunit cable may be pulled up to 6.5 lbs. without the ferrules decoupling inside the adapter.
The ST compatible connector is not a dead connector for commercial building
installations, the ST connector will support the same speed networks that an SC will support.
TERMINATION:
Epoxy termination:
Epoxy termination requires placing
assembled connectors into a curing oven. This is a time-consuming process. Typical curing ovens can hold up to six connectors at a time. The curing for epoxy-style connectors can be as long as 45 minutes.
Advantages: Batch termination
Available in Single-mode and Multimode Low connector material cost
Disadvantages: Consumables
Oven Needed Large Kits
Adhesive termination:
Adhesive termination connectors are cured under a Ultraviolet light ( UV ); The process takes less than a few minutes.
Advantages: Low consumable cost
No heat generated equipment needed
Faster installation time than the heat- cured termination techniques
Disadvantages: Consumables
Large Kits
...
CRIMP STYLE TERMINATION:
Enhancement of optical connectors has resulted in the development of crimp-style connectors which require no curing process.
Advantages: No epoxy
No polishing No consumables
Fewer tools needed minimal set-up required
Disadvantages: Tensil Strength
CONNECTORIZATION: EPOXY STYLE
Connectorization:
The procedures below are designed to be generic in nature for each of the
terminations. To ensure proper installation for each connector, please refer to the vendor’s specific instructions
EPOXY STYLE :
1. Slide the boot of the connector over the end of the cable to be connectorized. Strip jacket to a length of 1 1/8”
2. Measure and mark the buffer from 3/8” from the end of the fiber.
3. Remove the excessive buffer in 1/4” increments to the mark made of the buffer, be sure to remove any and all buffer and coating on the fiber. Cut kevlar at 1/4 “ see fig. C.
4. Clean the stripped fiber with alcohol wipes.
5. Mix the epoxy on a clean surface and coat the bare fiber ( looks like a 900 micron buffer) 6. Insert the fiber into the connector body using a twisting motion if necessary
7. Slide the cable jacket into the back of the connector being sure that the kevlar fans back to fit between the cable jacket and the inside of the metal sleeve
8. Crimp the rear shell of the connector with a hex die. see fig. D. 9. Slide the boot up to fit tight to the back of the connector. 10. Cure the epoxy:
a. Oven b. Room air
11. Score the fiber as close the the ferrule as possible to the tip of the ferrule with the scribe tool. Gently pull up on the scored fiber with tweezers, remove the excess fiber. see fig. E. 12. Remove any glass bur’s that may be on the end of the fiber with a 5 micron film.
13. Final polishing procedure: polishing in a figure 8 motion on the fine film
14. Clean the tip of the ferrule and inspect with a view scope to ensure a good clean polish ( free of chips, scratches, and cracks) see fig. F.
Figure C.
. . . .
OPTICAL FIBER TERMINATION:
Figure D.
CRIMP STYLE TERMINATION:
The crimp style termination is a mechanical splice that happens internally in the
connector body. An index matching gel is also internal the body to help couple the light the junction of the two fibers.
This style of connection: there is no epoxy , and no polishing of the ferrule.
Crimp style termination: ST Connector 900 micron
1. Load the connector body into the installation tool, with release wire up.
2. Slide the 900 um strain relief boot onto the rear housing until it locks. Slide the rear housing with boot down the fiber ( little end first)
3. Strip approximately 40 mm ( 11/2”) buffer from the end of the end of the cable. Be sure to strip buffer from the fiber in small 5mm ( 1/4”) sections. After stripping, measure and mark the buffer 9mm ( 3/8”) from the end.
4. With an alcohol wipe clean the bare fiber
5. Cleave the fiber 7 mm from the end of the buffer, see figure G. 6. Insert cleaved fiber into the hole of the microscope, check the cleave 7. Remove rear dust cap from the connector body
8. Carefully insert the fiber into the stem of the connector body. Gently twisting the fiber may ease insertion. Do not twist or remove the fiber once it is fully inserted, the fiber is fully inserted when the 9mm mark on the buffer is reached at the
end of the connector body, ensure there is a slight bow in the fiber, see figure H.
9. Depress the installation tool plunger. Hook release wire, slowly release the plunge, see figure I.
10. Push and rotate the connector body 1/4 turn counterclockwise in order to unlock the connector from the installation tool. Rest the crimping tool against the connector body to ensure it is aligned properly. Using the first die on the first crimping tool, crimp the stern on the buffer at the “ buffer crimp area”, see figure J.
11.Unclamp the fiber. Align and press the rear housing with boot into the front housing until a click is heard. Remove the connector from the installation tool. The installation is complete
. . . .
OPTICAL FIBER TERMINATION:
...
Figure G. Figure H.
Overview:
• A good installer is efficient, organizing the work to complete first thing first. • A good cable set-up means all materials are placed so the cable can be
handled properly.
• Job site should be secured from any occupants of the building or any non- related personnel.
• Equipment should be in proper place for pulling - jackstand, cable tree, tuggers, etc.
Secure the area for Cable pulls:
• Set - up cones and caution tape across the area • Notify proper personnel that work is beginning
Cable Pull set-up:
• Large cable reels may need the use of a Jackstand • Smaller cable reels may need the use of a cable tree • Others:
• Reel-in-a- box • Easy-box
Pulling horizontal pathways:
Horizontal pathways support many different kinds of information for its users: • Voice communications • Data communications • CATV • Alarms / Security • Audio Conduit Pulls:
Conduit provides a good pathway for the cable. Conduit may be made of: • Electrometallic tubing (EMT)
• Rigid metal
• Rigid Polyvinyl chloride (PVC) • Fiberglass
Note: Conduit made of flexible metallic tubing should not be used unless it is the only practical alterna- tive.
Moving the cable ( fiber) through the conduit from one end to the other requires some type of object to precede the cable through the conduit.