Optical cables can be distinguished by their core type, sheath material, size, and intended application, with single-mode and multimode fibers being the primary categories.

Core Type: Single-Mode vs Multimode

• Single-mode fiber (SMF) has a very thin core (8–9 µm) that carries a single light signal, ideal for long-distance transmission with minimal signal loss ( ).
• Multimode fiber (MMF) has a larger core (50–62.5 µm) that carries multiple light signals simultaneously, suitable for shorter distances and high-speed local networks ( ).
• The core size and the number of modes are the most reliable indicators of the fiber type.

Sheath and Outer Material

• Indoor cables typically use polyvinyl (PVC) or flame-retardant PVC, which should appear smooth, bright, and flexible ( ).
• Outdoor cables often have a black polyethylene (PE) sheath, smooth and uniform in thickness, resistant to UV and environmental damage ( ).
• Inferior cables may have rough surfaces, bubbles, or pits due to recycled or low-quality materials.

Fiber Quality Indicators

• High-quality optical fibers are usually A-grade cores from reputable manufacturers, with consistent color and clarity ( ).
• Low-quality fibers may be damp, discolored, or mixed (e.g., single-mode fibers mixed with multimode), often from unknown sources.
• Proper testing equipment is required to verify fiber quality, as visual inspection alone may not detect internal defects.

Connector and Application Differences

• Fiber optic cables come with various connectors (e.g., SC, LC, ST) that are designed for specific environments and space constraints ( ).
• The choice of cable also depends on network speed, bandwidth requirements, and transmission distance ( ).

Summary

To distinguish optical cables effectively:

1. Check the core size to identify single-mode or multimode fiber.
2. Examine the sheath material for indoor or outdoor suitability.
3. Assess fiber quality by clarity, color, and manufacturer grade.
4. Consider the connector type and intended application to ensure compatibility. By combining these physical and performance characteristics, you can reliably identify and select the appropriate optical cable for your networking needs ( ).