Fiber Optic Connector Types and Their Impact on Insertion Loss and Return Loss

Introduction

In fiber optic communication systems, maintaining signal integrity is critical. Two key performance indicators used to assess the quality of fiber connections are Insertion Loss (IL) and Return Loss (RL). While many factors influence these losses, the type of fiber optic connector used plays a crucial role. This article explores various connector types—such as SC, LC, FC, ST, APC, and UPC—and analyzes how their design and polishing affect IL and RL performance.

review Insertion Loss and Return Loss

• Insertion Loss (IL): Measures the amount of optical power lost at a connection point, typically expressed in decibels (dB). A lower IL value indicates better performance.
• Return Loss (RL): Indicates the amount of light reflected back toward the source, also in dB. A higher RL value is preferable, as it represents less reflection.

For detailed introduction, please refer to the previous post：Insertion Loss vs Return Loss in Fiber Optics: Definitions, Formulas, Standards, and Causes

Why Connector Type Matters

Fiber connectors are not just mechanical interfaces—they influence how well two fibers align, how much light is lost or reflected, and ultimately the network’s performance. The two most significant factors are:

1.Ferrule alignment and concentricity

2.End-face geometry and polishing style (UPC vs APC)

Common Fiber Optic Connector Types

UPC vs APC: The Polishing Matters

The angled surface of APC connectors helps reflect stray light into the cladding, reducing return loss significantly. However, APC and UPC connectors should never be mated together, as this leads to severe performance degradation.

How Connector Selection Affects IL/RL

1.SC/LC Connectors:

• LC connectors often provide slightly lower IL due to smaller ferrules and better alignment.
• Both support APC/UPC polishing for improved RL.

2.MPO/MTP Connectors:

• Designed for multi-fiber environments.

• Generally exhibit higher insertion loss due to alignment complexity across 12 or 24 fibers.

• Premium low-loss MPOs can reduce IL to below 0.35 dB.

3.Connector Wear and Contamination:

• Dirty or worn connectors significantly degrade IL/RL.

• Always inspect and clean before testing or installation.

Conclusion

The type and quality of fiber optic connectors directly impact network performance through insertion loss and return loss. By selecting the right connector types—SC, LC, APC, or MPO—and maintaining them properly, network designers can ensure minimal signal loss and optimal reflection control. As fiber networks evolve toward higher speeds and densities, understanding these impacts becomes essential for reliable infrastructure.