Coaxial fiber optic connector inner and outer conductors

A coaxial connector features a central inner conductor that carries the signal, surrounded by an outer conductor that acts as a shield, with a dielectric separating them to maintain signal integrity.

Inner Conductor

The inner conductor is the core of the coaxial connector and is responsible for carrying the electrical or RF signal. It is typically made of solid copper, stranded copper, or copper-plated steel to ensure good conductivity and minimal signal loss . In fiber optic coaxial hybrid systems, the inner conductor may also interface with optical components, but in traditional RF coaxial connectors, it directly transmits the signal. The diameter and uniformity of the inner conductor are critical for maintaining the characteristic impedance of the cable and ensuring efficient signal propagation .

Outer Conductor

The outer conductor, also called the shield, surrounds the inner conductor and the dielectric. It is usually made of braided copper, aluminum foil, or a combination of both . Its primary functions are:

• Electromagnetic shielding: It prevents external electromagnetic interference (EMI) from affecting the signal carried by the inner conductor .
• Signal containment: It confines the electromagnetic field within the coaxial structure, reducing radiation losses .
• Ground reference: The outer conductor is typically held at ground potential, providing a stable reference for the inner conductor voltage .

Dielectric and Conductor Spacing

Between the inner and outer conductors lies a dielectric insulator, which can be made of plastic materials like PTFE or air . This dielectric maintains a precise spacing between the conductors, which is essential for controlling the cable's impedance and minimizing signal reflections and losses . The concentric design ensures that the inner and outer conductors share the same geometric axis, which is critical for high-frequency signal transmission.

Summary

In a coaxial fiber optic or RF connector:

• The inner conductor carries the signal.
• The outer conductor shields the signal and provides a ground reference.
• The dielectric separates the two conductors and maintains impedance.
• The coaxial design confines the electromagnetic field, reduces interference, and ensures efficient signal transmission . This structure allows coaxial connectors to transmit high-frequency signals reliably while minimizing losses and external interference.