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What color is single mode fiber cable?

Single mode fiber cable is a type of optical fiber cable designed to carry light waves through a small core diameter over long distances. It plays a vital role in high-speed, long-distance telecommunication networks. Knowing the standard color coding for single mode fiber helps identify and manage these cables efficiently.

Optical fiber cables carry information over long distances by guiding light through an inner glass core. Single mode fiber has a small core size (about 9 microns) that only allows one mode of light to propagate through at a time. This allows the light to travel farther without dispersion, enabling very high bandwidth applications.

To help installers identify and manage different types of cables, industry standards establish color codes for the cable jackets and fiber strands inside. For single mode fiber, these colors are most commonly yellow or blue. Here is an overview of the standard single mode fiber cable color coding:

Cable Component Standard Color
Cable jacket Yellow
Fiber strand jacket Blue

Knowing these standard colors allows quick visual identification of single mode fiber runs. It also enables installers to match up fiber ends and terminate connections properly. However, some variation can exist between cable manufacturers in the exact shade or material composition.

Jacket Color Coding

The overall cable jacket provides the first visual identifier of cable type. For single mode fiber with up to 12 strands, the standard exterior jacket color is yellow. This distinguishes it from multimode fiber, which has an orange jacket, or other cable varieties like CAT5 with blue jackets.

Within data centers, yellow cabling is ubiquitous for single mode backbone runs. However, some manufacturers offer alternative jacket colors for specific applications:

Jacket Color Application
Yellow Standard exterior for single mode up to 12 strands
Orange Used for single mode cables with over 12 strands
Blue Optional for external plant or aerial cables
Green Used for outdoor single mode in some networks

While optional colors exist, yellow remains the most common jacket for identifying single mode cable runs. The specific Pantone or RAL shade may vary slightly between manufacturers. But seeing a yellow jacket on fiber optic cabling generally indicates single mode transmission inside.

Fiber Strand Color

Inside the cable jacket, manufacturers color code the individual fiber strands for identification. For single mode cable, each fiber is coated with a tight buffer colored blue. This contrasts with orange or aqua coloring for multimode strands.

Looking at the strand coating color verifying it is blue is an essential verification step when terminating fiber optic patch panels or transceivers. It ensures the correct fiber strand is being worked on.

The blue coloring extends the length of the fiber strand from end to end. Some legacy cable varieties use other colors for fiber coding, but blue is the standard for modern single mode installs. Additionally, the fibers may have colored tracers or stripes added to denote position within the cable:

Fiber # Trace Color
1 Blue with blue tracer
2 Orange tracer
3 Green tracer
4 Brown tracer
5 Slate tracer

These tracers provide further identification between multiple fiber strands in a single jacket. But the core blue color remains constant across all single mode varieties.

Cable Labeling

In addition to colored jackets and fibers, installers often add printed labels on the cable for identification. Labels typically include details like:

  • Fiber type (single mode)
  • Fiber core and cladding size
  • Jacket material
  • Manufacturer name
  • Product or part number
  • Date manufactured
  • Length markings

Labels help clearly identify cable specifications after installation when just the jacket exterior may be visible. This provides maintenance teams all the details needed to manage and repair the cabling during its lifetime.

Connector Color Coding

The final component to consider for fiber optic color coding is the connector at termination points. While fibers have blue coatings, connectors use other standard colors to indicate transmission mode:

Connector Type Typical Color
LC – Single mode Blue housing
SC – Single mode Blue housing
ST – Single mode Black housing

Seeing blue connector housings provides a final visual check that single mode interfaces are being worked on. While black ST connectors lack clear color coding, the fiber strand jacket underneath should still be blue.

Non-Standard or Mixed Cable Colors

While yellow jackets and blue fibers provide a straightforward standard, exceptions exist in the field. Older legacy cables may use other color schemes that do not match current conventions. For example:

  • Early single mode used gray fiber coating
  • Short jumper cables might skip coloring entirely
  • Some installers use other jacket colors by preference

Ultimately it is the specific fiber’s core size and transmission specs that determine single mode capability, not just its color. But when working with non-standard cables, extra care is required to verify fiber types to avoid connection issues.

Additionally, hybrid single mode/multimode cables exist with both fiber types in one jacket. These resemble standard single mode but contain some orange multimode strands. Again, verification of each fiber is important for proper handling.

Core Size Verification

When working with non-standard or mixed fiber coloring, measuring the core size provides confirmation of fiber transmission mode. This can be done actively for live fibers, or by illuminating and magnifying cut fiber ends:

  • Single mode: 8-10 micron core
  • Multimode: 50-62.5 micron core

Most single mode cores will measure 9 microns. If core size does not match the expected result for fiber coloring, always default to verifying core size for the definitive fiber identification.


Standardized color coding makes identifying and working with single mode fiber cable more efficient. A yellow jacket and blue fiber coating offer simple visual verification of single mode cabling. Connector colors, labels, and strand tracers provide further detail for installation and maintenance.

However, exceptions can exist with older legacy or mixed cables. When unsure, core size measurement provides the definitive test to verify single mode transmission. Understanding these color coding conventions allows installers, technicians, and network engineers to more easily deploy and manage single mode cabling for maximized performance.