Professional Manufacturer of Fiber Optic Products

Different Types Of Fiber Optic Adapter FC

Fiber optic adapter FC is developed to mate two FC fiber optic connectors. It has a metal housing and can be fastened by a turnbuckle, is very easy to operate and can keep the optic link in good status for a long time. So it is widely used as an equipment/instrument’s interface. And it is also widely used in ODF, patch panels.

Fiber optic adapter FC can be typically divided into square type, oval type, round type, and rectangle type in single-mode and multimode versions.

Square FC fiber optic adatper

Square FC fiber optic adatper

Oval FC fiber optic adatper

Oval FC fiber optic adatper

Round FC Fiber optic adapter

Round FC fiber optic adapter

Rectangle FC Fiber Optic Adapter

Rectangle FC fiber optic adapter

Fiber optic Adapters FC Round type, is D-hole mounting. It has two options: single D and double D. Single D is that the adapter has only one plane milling while double D has two.


Round type also can be divided into two subtypes according to flange diameter: small D and Big D.  Small D means the flange diameter is 11mm, while Big D is 13mm.


So fiber optic adapter FC Round types can be divide into four sub-types:

1. Small D single D

2. Small D double D

3. Big D single D

4. Big D double D


Another feature of Fiber optic Adatper FC is the key slot, which is mated with the key of the FC fiber optic connector. It has four options(K option) according to the standard. Respectively, the FC connector has four options too.

Simplex Adapter Interface

K Option Min Max
K=1 (FC/PC) 2.15
K=2 (Wide Key Slot FC/APC) 2.15 2.2
K=3 (Narrow Key Slot FC/APC) 2.03 2.08
K=4 (Either) 2.16 2.18


Connector Interface Option

K Option Min Max
K=1 (FC/PC) 2.14
K=2 (Wide Key FC/APC) 2.09 2.14
K=3 (Narrow Key FC/APC) 1.97 2.02
K=4 (Either) 2.13 2.15


From the tables above, you can see there are 2 options recommended for FC/APC. We named it wide key and narrow key.

Flat FC/PC connectors are significantly less alignment sensitive than their angled FC/APC counterparts, So the four options are acceptable for FC/PC adapter,  even K=1 option adapter mate with K=3 option connector it is also acceptable.

But for FC/APC, It is alignment sensitive we recommend wide key(Adapter&Connector) and narrow key(Adapter&Connector). Wide key or narrow key, which one should be chosen, it depends on the instrument/equipment or your detail requirements.


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