Optical fiber is a technology that transmits data using light signals instead of electricity.
It is widely used in internet, cloud, telecom, and data centers because it is:
- Very fast
- Long-distance capable
- Highly reliable
To achieve this performance, optical fiber is built in multiple protective and functional layers.
- The core is where data actually travels as light.
- It is the most important part of the fiber.
Key Points:
-
- Made of ultra-pure glass (silica) or plastic
- Has a higher refractive index than cladding
- Enables total internal reflection (TIR)
Types:
-
- Single Mode Fiber (SMF)
- Very thin (~8–10 µm)
- Used for long distances (WAN, telecom)
- Multimode Fiber (MMF)
- Thicker (~50–62.5 µm)
- Used for short distances (LAN, data centers)
- Single Mode Fiber (SMF)
- Surrounds the core and keeps light inside.
Key Points:
-
- Lower refractive index than the core
- Reflects light back into the core using TIR
Why it matters:
-
- Prevents signal leakage
- Reduces attenuation (signal loss)
- A protective layer over the core and cladding.
Key Points:
-
- Made of soft plastic (acrylate/silicone)
- Protects from:
- Moisture
- Bending stress
- Physical damage
Thickness:
-
- Typically around 250 µm
- Adds strength to the cable during handling.
Key Points:
-
- Made of Kevlar (Aramid fiber)
- Same material used in bulletproof vests
- Sometimes includes steel for heavy-duty cables
Why it matters:
-
- Prevents cable breakage
- Handles pulling and installation stress
- The outermost protective layer.
Key Points:
-
- Made of:
- PVC
- Polyethylene (PE)
- TPE
- Made of:
Protects Against:
-
- UV radiation
- Water
- Chemicals
- Physical damage
Color Coding:
| Fiber Type | Color |
|---|---|
| Single Mode | Yellow |
| Multimode (OM2) | Orange |
| Multimode (OM3/OM4) | Aqua |
| Indoor cables | Black / White / Gray |
|
Layer |
Material |
Function |
|
Core |
Glass or Plastic |
Transmits light signals |
|
Cladding |
Glass or Plastic |
Reflects light back into the core |
|
Buffer Coating |
Acrylate or Silicone |
Protects fibre from moisture and bending |
|
Strengthening Layer |
Kevlar (Aramid fibres) |
Prevents breakage during installation |
|
Outer Jacket |
PVC, PE, or TPE |
Shields fibre from environmental damage |