In our last post we talked about choosing the right fiber optic connector type best suited to your application.  In this article we will talk about the various termination methods for your connector choice.  The termination method you choose is just as important your connector choice.  Here are the most common termination methods.



Connector Termination Options


Interface Loss + ‘Termination Loss’ = True Connector Loss


Important Note - The method that you choose to terminate fiber has greater impact on a loss budget than your choice of connector!

The connector charts in our previous post show dB values in terms of interface loss (i.e. loss at the connector endface). For a true estimate of connector loss you must add to that value the additional loss produced by the termination method that you choose, which for the sake of discussion we will call “termination loss.” This additional loss occurs at the point where the connector is joined to the field fiber. Most fiber optic connectors fall into one of two categories; they are either “quick termination connectors” or they are “epoxy style” connectors.



Quick Term vs. Epoxy Connectors


Which is Better?


Quick Termination Connectors and Epoxy Connectors each have their own advantages and disadvantages, depending on the application and options you choose.



Quick Term Connector Options


“Quick-term” connectors provide a “quick” way to terminate fiber. These connectors are available with factory-polished ferrule endfaces, so no time is required for field polishing. Also, they do not require time to cure epoxy.
Quick term connectors offer two main options:

Quick Term Option 1

“Mechanical” Quick-Term Connector

Most “mechanical” quick-term connectors use a mechanical device to hold or “splice” the field fiber to a fiber stub within the connector body. These connectors are great when...



  • Speed is of the essence, e.g. emergency restoration
  • Installers do not have the skill or experience to assemble and hand polish connectors in the field
  • Fusion splice connectors and equipment are not available

 

Examples of “mechanical” quick-term connectors are:

  • UNICAM Pretium from Corning
  • Bobtail Connector from Fiber Instrument Sales (FIS)
  • Fast Connectors from AFL
  • Mechanical Field Connectors from Sumitomo


Quick-Term Option 2


“Splice-On” Connector (SOC)

Similar to “mechanical” quick term connectors, SOC quick-terms have a factory-polished fiber stub within the connector body. The difference is that SOC’s use a fusion splicing process to join the fiber stub to the field fiber instead of mechanical means, resulting in lower loss.

SOC’s typically have lower loss than field-polished epoxy connectors. The factory polish on an SOC is of higher precision than that which can be achieved by hand polishing in the field.

Insertion Loss Comparison (mated pair):

 

SOC Connector:

Mating Loss .4 dB + Per Splice Loss<.05 dB = .5 dB total loss

 

Field-Polished Connector:

Mating Loss .75 dB + 0 Splice Loss = .75 dB total loss

 

Back reflection considerations are greatly improved by factory UPC polish (-55 dB) versus typical hand-polish PC (-40 dB).

Using fusion spliced APC connectors provides a distinct advantage of -65 dB back reflection, ensuring high data-rate performance. Field mechanical APC mated connectors require a cleave angle of 8 degrees that increases insertion loss but will reduce the back reflection.

 

SOC’s also provide a significant advantage over another “fusion splice” termination method, namely fiber optic pigtails. Unlike pigtails, SOC’s do not require an external splice protection sleeve or splice tray, which saves rack space.

 

SOC’s are available from a variety of manufacturers including:

  •   • Fiber Instrument Sales (Cheetah SOC)
  •   • AFL (FuseConnect )
  •   • Sumitomo (Lynx 2)
  •   • Fitel and Seikoh Giken also offer SOC’s

 

Epoxy Connector Options

With epoxy connectors, the field fiber is permanently bonded to the connector ferrule, providing a very reliable connection. Epoxy connectors offer two options:

 

Epoxy Option 1

Field Polished Connector

 

With this termination method, the field fiber is routed through the connector body and ferrule, then field-polished as part of the ferrule endface. Since no splicing is involved, there is no “termination” loss as defined earlier.

 

Advantages:

  •   • Capable of low insertion loss and low back reflection
  •   • High quality and reliability when installed properly
  •   • Lowest cost per connector

 

Disadvantages:  

  •   • Special tools for curing epoxy and hand- polishing
  •   • Long assembly time (including epoxy cure time)
  •   • High level of training is required
  •   • Precise endface geometry difficult to achieve by hand polishing

 

Most field-polished epoxy connectors use industry-standard epoxy. The 3M Hot Melt Connector uses a proprietary adhesive that does not require curing time.

 

Epoxy Option 2

 

Factory Polished Connector

 

Epoxy connectors can be purchased with factory-polished endfaces and are typically sold as...

 

Pre-terminated Cable Assemblies – Custom cable assemblies pre-terminated with connectors of your choice.

Connectorized Pigtails – Factory-polished connectors can be purchased that have attached pigtails for splicing to the field fiber.

 

Advantages:

 

  • The precision endface finish can provide lower loss than that achieved by hand-polishing
  • Less training than for hand-polished connectors
  • Quick installation

Disadvantages:

  • More complicated cable management
  • Pre-polished connectors cost considerably more per unit than hand-polished connectors (materials costs are higher but labor costs are lower)
  • Connectorized pigtails have a higher equipment cost (a fusion splicer is required).