FC Connector
Direct Answer
The FC connector (Ferrule Connector / Fiber Channel, TIA-604-4 / FOCIS-4) is a heavy-duty optical connector designed by NTT. Utilizing a 2.5 mm ceramic ferrule inside a threaded round nickel-plated metal coupling nut, it provides extreme mechanical retention in high-vibration environments and optical test instrumentation.
Source: TIA-604-4-B (FOCIS-4) / IEC 61754-13
Specs
| Standard / FOCIS | TIA-604-4-B (FOCIS-4) / IEC 61754-13 |
| Ferrule Diameter | 2.5 mm |
| Ferrule Material | Zirconia ceramic |
| Latching Mechanism | Threaded screw-on metal coupling nut |
| Keying Mechanism | Adjustable / fixed alignment key |
| Fiber Modes Supported | Single-Mode (OS2) and Multi-Mode |
| Typical Insertion Loss | 0.15–0.30 dB |
| Polish Types Available | UPC (Flat metal body) and APC (Step-keyed / cone body) |
Threaded Retention and Precision Keying
The FC connector was the first optical connector to utilize a ceramic ferrule. Its threaded screw-on barrel and internal spring provide constant axial pressure regardless of cable pulling tension. A precision alignment key (available in standard wide-key 2.14mm or narrow-key 2.0mm tolerances) ensures exact angular repeatability.
Applications in Test and Measurement
While push-pull connectors (LC/SC) dominate enterprise datacenters, FC/APC and FC/UPC remain the standard physical interface on Optical Time-Domain Reflectometers (OTDRs), optical power meters, laboratory lasers, and aerospace avionics subject to high vibration.