1. NET 436 optical Network Tutorial Lecture #4
Networks and Communication Department
Lab 4

2. Structure of Fiber-Optic Cables
Core
Cladding
Coating

3. General Structure of Fiber-Optic Cables

4. Cladding Cylindrical material made of glass or specialized plastic
Central portion of the fiber
Light signal carrying the information travels through the core
The diameter of the core can range from a couple of micrometers (µm-one millionth of a meter) to a couple of millimeters (mm-one thousandth of a meter)
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Networks and Communication Department

5. Jacket
Insulates and protects the fiber from physical damage and environmental effects, such as moisture, that might interfere with the inner workings of the cable
Usually made of opaque plastic or another type of material
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6. Layered Structure (continued):
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7. Layered Structure:
Inner core – glass or plastic fibers at the center that carry laser pulses or an LED light used for data transmission
Cladding – a layer of plastic or glass around the fibers that reflects the light back to the core
Plastic buffer – an opaque layer that protects the cladding and the core and absorbs any light that escapes
Plastic sheath – providing the overall cable protection
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8. Layered Structure (continued):
Two types of fiber with different propagation modes:
Single-mode fiber:
only single mode is permitted
small core diameter: 8.3(core)/125(cladding) µm
Multi-mode fiber:
several modes are permitted
large core diameter: 50~62.5(core)/125(cladding) µm
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9. Layered Structure (continued):
Glass (silicon dioxide, also called silica) is used usually for optical fibers.
An optical fiber consists of core and cladding, having less refractive index.
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10. Propagation modes
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11. Types of Fiber-Optic Cables
Single-mode fiber
Multi-mode fiber
Step index fiber
Graded index fiber
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12. Single-mode fiber Dispersion is minimal in the single-mode fibers.
The core diameter of a single-mode fiber is less than 10 µm.
A typical single-mode optical fiber, showing diameters of the component layers.
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13. Single-mode fiber
Very small core diameter, on the order of a few micrometers (μm); less than that of a human hair
The cladding diameter is tens of micrometers, making it much larger than the core
Single-mode fiber can transmit information at very high data rates across large distances
The small diameter restricts only a single mode of light to carry all of the information
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Networks and Communication Department

14. Multi-Mode Fiber
Has a much larger core diameter, ranging from tens to hundreds of micrometers
Used for lower-bandwidth, shorter-distance applications than single-mode fibers
Information-carrying capacity is less than that of single-mode fibers due to the physical effects they impose on the signals traveling through them
24-Feb-19
Networks and Communication Department