Fiber Connectors and Polish Types

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Connector Types

SC - This acronym is commonly known as:

  • Subscriber Connector
  • Square Connector
  • Standard Connector

The connector itself is a “Snap-In” or “Push/Pull” type that snaps into place when inserted into an SC style receptacle. It has a 2.5mm ferrule and is commonly used in both simplex and duplex configurations.

ST - Know as a “Straight Tip” connector, usually found on MultiMode cables and networks. The connector body is a bayonet type that twists to lock or unlock itself, it has a 2.5mm ferrule that protrudes from the connector body.

FC - FC can stand for either “Ferrule Connector” or less commonly “Fiber Channel”. This connector is a screw on type that is commonly used in the datacom/telecom industries, but is becoming less popular and is being superseded by the SC or LC types. It has a 2.5mm ferrule like SC and ST connectors.

LC - This acronym is commonly known as:

  • Lucent Connector
  • Little Connector
  • Local Connector

These connectors are Snap-In just like the SC connector but are half the size, and therefore has a 1.25mm ferrule. They are commonly used to connect SFP, CFP modules etc.

MTRJ - This connector is only used for MultiMode cables and (sort of) looks like an RJ 45 connector on a regular copper patch cable. The acronym stands for “Mechanical Transfer Registered Jack”, or “Media Termination Recommended Jack”. It has a single ferrule that both fibers are mounted in.

Polish Types

It may seem a little strange to see the word “polish” associated with a fiber patch cord, but the following section will describe what the term means.

The polish “type” refers to how the end of the fiber that is inside the connectors is shaped. The mechanism that is used to shape the end is “polishing” the end until it is the desired shape, as well as being smooth so that the light entering or exiting it is not refracted.

To make a fiber optic connection as efficient as possible “back reflection”, especially for higher speed connections, must be at a minimum. Back reflection refers to the amount of light that gets reflected back to the source, the more light that is reflected back, the lower the efficiency of that connection.

Ask you can imaging the shape of the end of a fiber, and the accuracy of that shape, dictate how efficiently the light travels through two connected fibers.

So why are there different polish types? If one polish type is more efficient than the others, why have the others? As with everything it is down to time and money. The more efficient types are simply more expensive to produce, and not always necessary for the application at hand.

There are three “Polish” types for fiber patch cables, each type is described below:

PC - Physical Contact. Has a slight dome at the end of the ferrule, this helps to maximize the signal being transmitted.

UPC - Ultra Physical Contact. More extensive polishing than the PC type, this creates a better contact/signal than the PC type.

APC - Angled Physical Contact. Polished at an angle instead of a dome shape. This polish type is the most effective of the three.

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