Brief Introduction Of Optical Adapter | Types SC LC FC ST UPC APC--ETU-LINK

Brief introduction of optical adapter

August 22. 2016

In fiber optic cabling, many engineers ask:

What is an optical adapter?

What are the types of fiber adapters?

What is the difference between SC, LC, FC, ST, APC, UPC?

This article explains definitions, types, features, polishing types, and applications to help you select correctly.

Optical adapter ( known as Flange plate), are also called optical connector and Widely used in optical distribution frame (ODF), optical communication equipment, instrument etc, with superior, stable and reliable performance.

Optical adapters (fiber couplers) are core passive components for butt connection of fiber connectors, ensuring precise alignment of fiber cores and stable transmission. They are widely used in ODF, data centers, FTTH, switches, and test equipment.

I. What Are the Main Types of Optical Adapters?

Product types: Optical adapter’s types : SC,FC,ST,LC,MTRJ,E2000 etc.

As following shows:

Optical adapters are classified by connector interface, polishing type, and structure to meet different wiring needs.

II. What Do SC, LC, FC, ST Stand For?

SC represents Standard Connector。

ST represents Straight Tip。

FC represents Fiber Connector。

The connector of “SC” is normative square shape, using engineering-plastics, having the advantages of high temperature resistance and not easy to oxidize.

The shape of “LC” connector is similar to SC, a little smaller than SC.

The connector of “FC” is metal.

The pluggable times of metal connector is more than plastic.

(1).SC: Square push‑pull, widely used in FTTH, PON, enterprise networks

(2).LC: Compact small square, high‑density data centers, SFP modules
(3).FC: Metal threaded, high stability for test & long‑haul
(4).ST: Round bayonet, legacy multimode LAN

(5).MTRJ/E2000: Special compact or self‑shutter design

III. What Are UPC and APC Optical Adapters?

Optical adapters are also divided by end‑face polishing: UPC and APC, which directly affect return loss and application scenarios.

Item	UPC Adapter	APC Adapter
Polishing	0° convex, ultra physical contact	8° angled polishing
Color	Blue	Green
Return Loss	~ -50dB	~ -65dB
Typical Use	Data center, LAN, Ethernet	CATV, PON, FTTx, broadcast

UPC is for general digital transmission; APC is for reflection‑sensitive analog & long‑distance systems. Never mix UPC and APC to avoid damage and high loss.

IV. What Are the Key Features of Optical Adapters?

Product features:

※ Lower loss when inserting , Less than 0.2db when connecting.

※ Good Interchangeability

※ Good Repeatability

※High precision zirconia ferrule for stable alignment

※High and low temperature resistance (-40℃~85℃)

※Plug‑and‑play, long service life (≥1000 times)

※Available in simplex, duplex, quad for high density

V. What Are the Application Scenarios of Optical Adapters?

Application range:

※ Optical communication system

※ CATV (or Cable network )

※ LAN, optical domain network

※ FTTH

※ Video transmission

※ Test instruments

※ Data center cabling & high‑speed Ethernet
※ 5G base station fronthaul & backhaul
※ Industrial & intelligent building optical networks
※ Switch/router/transmission equipment ports

FAQ: Common Questions About Optical Adapters
1) What is another name for optical adapter?
Also called fiber flange, fiber coupler, fiber adapter panel.
2) What is the difference between UPC and APC adapter?
UPC: blue, 0° polish, for data centers; APC: green, 8° polish, for CATV/PON. Do not mix.
3) Which adapter is best for data center?
LC UPC – small size, high density, low loss.
4) Can different adapters be used together?
Only same type: SC↔SC, LC↔LC; use hybrid adapter for cross-type conversion.
5) What is insertion loss of optical adapter?
Typically ≤0.2dB, ensuring high‑quality transmission.

Optical adapters are essential for fiber connections. Choosing the right type (SC/LC/FC/ST) and polishing (UPC/APC) ensures low loss, stability, and long service life in your network.
ETU-LINK provides full series optical adapters: SC, LC, FC, ST, UPC/APC, simplex/duplex/quad, suitable for data centers, FTTH, enterprise networks, and communication equipment.

Please tell us know if any questions or requirements for the above optical adapters. We sincerely look forward to hearing from you!

Last updated: May 27, 2026

Get a Quote/Datasheet

If you are interested in our products and want to know more details,please leave a message here,we will reply you as soon as we can.