High Tensile Strength & Temperature Stable Fiber Optic Jumper

Return Loss Fundamentals

High tensile strength temperature stable fiber optic jumpers must maintain good return loss performance. Return loss measures how much light reflects back toward the source. Reflections can disrupt laser operation and cause signal errors. Connector end face geometry primarily determines return loss. Understanding these relationships enables better jumper selection.

• Reflection Mechanisms

Fresnel reflection occurs at glass-air interfaces within the connector. Physical contact connectors aim to eliminate the air gap. Angled physical contact connectors use 8-degree angles to redirect reflections. Any endface imperfection creates additional reflections. Reflection sources must be controlled for low return loss.

• Return Loss Specifications

Standard PC connectors achieve 40-50dB return loss. Ultra PC (UPC) connectors achieve 50-55dB. Angled PC (APC) connectors achieve 60dB or higher. Temperature stable jumpers maintain specs across temperature range. Specification levels match different application requirements.

Endface Geometry Parameters

Interferometric measurements quantify critical endface geometry. Several parameters affect return loss.

• Radius of Curvature

The spherical curve of the polished endface affects physical contact. Radius of 10-25mm is typical for PC/UPC connectors. Too flat reduces contact pressure and increases loss. Too steep reduces contact area similarly. Radius control ensures proper fiber-to-fiber contact.

• Apex Offset

Apex offset measures how far the fiber is from the endface center. The fiber should be within 50 microns of the apex. Larger offset increases insertion loss and return loss. Offset varies with polishing process consistency. Apex centering is critical for low reflection connections.

Environmental Effects on Return Loss

Temperature changes affect connector geometry and return loss. Understanding these effects guides product selection.

• Thermal Expansion Effects

Different materials in the connector expand at different rates. The ferrule, adhesive, and fiber have different coefficients. Temperature changes can alter fiber position within the ferrule. This changes apex offset and return loss. Thermal stability requires matched material coefficients.

•  Mechanical Stress Effects

Cable tension can change connector geometry. Bending near the connector affects fiber alignment. Temperature cycling combined with stress causes permanent changes. Ruggedized jumpers resist these environmental effects. Mechanical robustness maintains return loss under real-world conditions.

Return Loss Testing Methods

Several methods measure return loss for quality verification. Each has advantages and limitations.

• Optical Continuous Wave Reflectometer

OCWR uses a directional coupler and power meter. It measures total reflected power from the device. This method is simple but cannot locate reflection sources. It works for finished jumper testing. OCWR testing is standard for production quality control.

• Optical Low Coherence Reflectometry

OLCR provides distance-resolved return loss measurements. It can identify individual reflection points along the jumper. Spatial resolution of 10-50 microns is typical. This method costs more than OCWR. OLCR analysis helps diagnose specific reflection sources.

FAQs

1. What is the difference between UPC and APC connectors?
UPC has a slightly domed endface with return loss of 50-55dB. APC has an 8-degree angle with return loss >60dB. APC connectors are typically green-colored for identification. UPC connectors are blue for single-mode. APC is preferred for analog video and high-reflection sensitive applications.

2. Can I mate a UPC connector with an APC connector?

No, mating UPC with APC damages both connector endfaces. The geometry mismatch prevents proper physical contact. Insertion loss increases dramatically, possibly over 1dB. Return loss degrades to worse than PC specifications. Only mate connectors of the same polish type.

3.  How often should jumpers be cleaned to maintain return loss?

Clean before every connection for critical applications. For less critical uses, clean when loss increases. Inspection before cleaning determines if cleaning is needed. Contamination is the main cause of return loss degradation. Document cleaning procedures and frequency for quality records.

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