Fiber optic patch cord APC-PC

Connecting an APC connector to a PC connector is generally not recommended due to mismatched end-face geometry, which can cause high back reflection and signal loss.

Connector Differences

• PC (Physical Contact) connectors have a slightly convex end-face designed to minimize air gaps between fibers, with typical return loss around 35–40 dB .
• APC (Angled Physical Contact) connectors have an 8° angled end-face that redirects reflected light into the cladding, achieving superior return loss of around 60 dB .
• Color Coding: PC/UPC connectors are usually blue, while APC connectors are green, making visual identification easier .

Compatibility Issues

Mating an APC connector to a PC connector is problematic because the angled end-face of the APC does not align properly with the flat or slightly convex PC end-face. This misalignment can result in:

• High back reflection, which may interfere with laser sources, especially in single-mode fiber systems .
• Increased insertion loss, reducing signal strength and potentially causing network instability .
• Physical stress on the ferrules, which can damage the fiber end-face over repeated connections .

Best Practices

• Avoid direct APC-to-PC connections. Use a patch cord with matching connector types on both ends (APC-to-APC or PC-to-PC) to maintain optimal performance .
• If a connection between APC and PC is unavoidable, consider using a hybrid adapter designed to mate APC and PC connectors safely, though this may still introduce some reflection and loss .
• Single-mode applications are particularly sensitive to return loss, so APC-to-PC connections should be avoided in high-speed or long-distance networks such as FTTx, WDM, or RF video systems .

Summary

While a fiber optic patch cord can physically connect an APC to a PC connector, it is not recommended due to mismatched end-face geometry, which can lead to high back reflection and signal degradation. For reliable performance, always match connector types or use a proper hybrid adapter designed for APC-to-PC connections.