FC circular interface

The FC circular interface is a threaded fiber optic connector designed for secure, low-loss connections in high-vibration environments.

Overview

The FC (Ferrule Connector or Fiber Channel) connector is a fiber optic interface featuring a circular, threaded coupling mechanism that ensures stable and vibration-resistant connections . Originally developed by NTT in the late 1970s as the "Field-Assembly Connector," it was the first connector to use a ceramic ferrule, typically 2.5 mm in diameter, to hold the fiber end securely . The ferrule is polished to a physical contact (PC) or ultra-polished (UPC/APC) finish, allowing the fiber cores to touch directly, minimizing insertion loss and back-reflection .

Design Features

• Threaded Coupling: The circular screw design prevents accidental disconnection and provides high mechanical stability, making it ideal for single-mode fibers and high-vibration applications .
• Ferrule Material: Zirconia ceramic or stainless steel ferrules ensure precise alignment and durability .
• Active Core Alignment (ACA): Some modern FC connectors, like those from DIAMOND SA, use ACA technology to reduce core eccentricity and optimize optical performance .
• Tuning Capability: Certain FC connectors allow rotation of the ferrule to fine-tune insertion loss, enhancing signal quality .
• Compatibility: FC connectors are compatible with adapters and other standard interfaces, though they are gradually being replaced by LC and SC connectors in high-density networks .

Applications

FC circular interfaces are widely used in:

• Telecommunications and CATV networks
• LAN, MAN, and WAN systems
• Test and measurement equipment
• Industrial, medical, and military environments
• Single-mode and polarization-maintaining fiber systems

Variants

• FC/PC: Standard physical contact polish
• FC/SPC: Super polish for lower insertion loss
• FC/UPC: Ultra polish for minimal back-reflection
• FC/APC: Angled polish for high-performance applications requiring very low return loss

Summary

The FC circular interface provides a robust, threaded fiber optic connection with precise ferrule alignment, low insertion loss, and high vibration resistance. Its design makes it suitable for demanding optical systems, though it is less common in modern high-density networks compared to LC and SC connectors .