The standard color sequence for the four fibers in a single-mode 4-core optical cable is Blue, Orange, Green, and Brown.

Fiber Color Sequence

For a 4-core single-mode optical cable, each fiber is individually color-coded according to the TIA-598-C standard to ensure proper identification during splicing, termination, and network deployment. The first four fibers follow this sequence:

1. Blue
2. Orange
3. Green
4. Brown This sequence is consistent across single-mode cables and is critical for maintaining correct duplex links or redundancy configurations, such as two duplex links or one duplex link plus two backup fibers .

Outer Jacket Color

The outer jacket color of a single-mode cable is typically yellow, which universally indicates single-mode fiber (OS1 or OS2). This helps technicians quickly distinguish single-mode cables from multimode cables, which often have orange or aqua jackets .

Cable Construction Notes

• Buffer Tubes: In loose-tube constructions, the tube holding the fibers may be blue or white, while the fibers inside follow the Blue/Orange/Green/Brown order .
• Strength Members: Steel wire or aramid yarn (Kevlar) is used to prevent stretching.
• Outer Jacket Material: PE (Polyethylene) for outdoor use or LSZH (Low Smoke Zero Halogen) for indoor safety.

Practical Application

Knowing the correct color sequence is essential for:

• Splicing and termination: Ensures proper alignment of transmit and receive fibers.
• Network maintenance: Prevents misidentification and reduces troubleshooting errors.
• Redundancy setups: Supports backup fibers without confusion. By following the TIA-598-C standard, technicians can maintain consistent, safe, and reliable fiber identification across installations .