The standard color sequence for a 4-core optical fiber cable is Blue, Orange, Green, and Brown.

Standard Color Sequence

According to the TIA-598-C standard, the first four fibers in a multi-fiber cable are always color-coded as follows:

1. Blue
2. Orange
3. Green
4. Brown This sequence applies to both single-mode (OS1/OS2) and multimode (OM1/OM2/OM3/OM4) fibers, ensuring consistent identification for splicing, termination, and troubleshooting .

Cable Structure Context

A typical 4-core optical fiber cable consists of:

• Optical Fibers: Four individual fibers capable of independent data transmission.
• Strength Members: Aramid yarn (Kevlar) for indoor cables or steel wire for outdoor cables to prevent stretching.
• Buffer Tubes: Loose tubes (gel-filled) or tight buffers to protect the fibers.
• Outer Jacket: PE (Polyethylene) for outdoor use or LSZH (Low Smoke Zero Halogen) for indoor safety . In loose tube constructions, the tube itself is often blue or white, while the fibers inside follow the Blue/Orange/Green/Brown order .

Practical Applications

• Duplex Links: A 4-core cable can support two separate duplex links (one fiber for transmit, one for receive).
• Redundancy: Often configured as one duplex link plus two backup fibers.
• Single-mode vs Multimode: Jacket colors may vary (yellow for single-mode, orange or aqua for multimode), but the internal fiber color sequence remains the same .

Summary

For any technician working with a 4-core optical fiber cable, the Blue, Orange, Green, Brown sequence is the standard reference for identifying individual fibers, ensuring proper splicing, termination, and network reliability .