Optical fiber connector types: An easy guide
The acronyms SC, LC, FC and ST refer to the most common types of optical connectors in FTTH applications and data networks. As for the PC/UPC/APC terminology, it refers to the type of polishing applied to the optical terminal (ferrule) which makes possible laser light pulses to cross through two optical fibers.
Then, for example, a typical FTTH pigtail with an SC/APC connector is referring to an SC connector with an APC polishing.
Before you start: A good practice is to keep clean the ferrules tips in order to optimize the optical link. If the connector gets dirty, an optical connector cleaner must be used to get rid of dust and spots.
Diagram of a typical SC-type optical fiber connector
- Most common optical connectors
- Polishing types
- Optical fiber connectors color chart
- Optical fiber cables color chart
Most common optical connectors
Detail of an FC optical connector (Ferrule Connector)
- “FC” stands for... Ferrule Connector.
- A brief history: It was the first optical connector using a ceramic ferrule, developed by Nippon Telephone and Telegraph. Its use is becoming less common in favor of SC and LC connectors.
- Features: The screwed fitting of the connector is vibration-proof; therefore it is used in applications under motion. It is also used in precision instruments (such as OTDR) and it is very popular in CATV.
- Optical features: For single mode fibers. Its insertion losses reach the 0.3 dB.
Detail of an ST (Straight Tip) optical connector
- “ST” stands for... Straight Tip.
- A brief history: Developed in the USA by AT&T and used in professional environments such as corporate networks as well as the military field.
- Features: Its shape reminds of the Japanese FC connector, except for its BNC-type fitting system (twist lock also called bayonet style fitting).
- Optical features: For multimode fibers. Losses of about 0.25 dB.
Detail of an LC optical connector (Lucent Connector or Little Connector)
- “LC” stands for... Lucent Connector or Little Connector.
- A brief history: Developed by Lucent Technologies and released in 1997.
- Features: Push-and-pull fitting (it reminds an RJ45). Safer and more compact that the SC-type, allowing even more density of connectors in racks, panels and FTTH.
- Optical features: For monomode and multimode fibres. Losses of 0,10 dB.
Detail of an SC optical connector (Subscriptor Connector or Square Connector)
- “SC” stands for... Suscriptor Connector or Square Connector
- A brief history: Developed by Nippon Telegraph and Telephone, it has become the most popular because of its decreasing production costs.
- Features: Quick push-and-pull fitting. It is compact, allowing a big density of connectors per instrument. It is used in FTTH, telephony, CATV, etc.
- Optical features: For single mode and multimode fibers. Losses of 0.25 dB.
Optical fiber ferrule polishing: PC, UPC and APC
- PC: Physical Contact. The ferrule is beveled and finished in a plain surface. This avoids empty spaces between the ferrules of the connectors being coupled, and achieves insertion losses among -30 dB and -40 dB. Its use is increasingly falling out.
- UPC: Ultra Physical contact. They are similar to the PC connectors, allowing decreasing return losses to a margin between -40 and -55 dB thanks to the sharper curve of the bevel. The current trend is using it in dead lines to allow operators to perform networks tests for example by using an OTDR.
- APC: Angled Physical Contact. The ferrule ends in a plain, 8 degree angled surface making it the connector that achieves a best optical link because it cuts down the return losses up the -60 dB thus allowing increasing the number of users in single mode fibers. For this reason, combined to its constantly decreasing manufacturing costs, APC has become the most used polishing type.
Optical fiber connectors color chart
|TYPE OF OPTICAL FIBER||CONNECTOR COLOR|
|50/125 laser optimized||Aqua|
|Single mode with APC polish||Green|
Optical fiber cables color chart
Optical fiber cables color code
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