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Fiber-Optic Cable

 Consists of a glass or plastic core

 Carries pulses of light

Fiber-Optic Cable

 Consists of a glass or plastic core

 Carries pulses of light

Total Internal Reflection

n1sin(θ1) = n2sin(θ2)

where:

n1 is the refractive index of the medium the light is leaving

θ1 is the incident angle between the light beam and the normal

(normal is 90° to the interface between two materials)

n2 is the refractive index of the material the light is entering

θ2 is the refractive angle between the light ray and the normal

Total Internal Reflection

n1sin(θ1) = n2sin(θ2)

Total Internal Reflection

CH3CHOHCH2OH

44.35° Critical Angle =

arcsin(1.0003/1.4310)

n1sin(θ1) = n2sin(θ2)

Total Internal Reflection

Ultra-pure glass

(SiO2)Cladding

Analog to Digital Signal

Characteristics of Fiber-Optic Cable

 Provides for data security

 Immune to electromagnetic interference

 Lightweight and small in diameter

 Safety

 Wide bandwidth

 Corrosion- and water-resistant

 Supports data transmission over longer distances than copper core cable

The Nature of Light

 Form of energy

 Classified as electromagnetic wave

 Identified in the electromagnetic wave spectrum chart

 Light wave pattern is described using the term

wavelength

Electromagnetic Wave Spectrum

Single-Mode Fiber-Optic

Cable: 1310nm/1550nm

Multimode Fiber-Optic

Cable: 850nm/1300nm

Fiber-Optic Cable Construction

 Composed of glass

or plastic core

surrounded by

cladding

 Classified as loose

tube or tight buffer

 National Electrical

Code (NEC) is

referred to for

building

specifications or

standards

Attenuation in Fiber-Optic Cable Transmission

 Scattering—The loss of signal strength due to

impurities in the core material.

 No core is 100% pure, hence scattering

 Dispersion—The distortion of the light wave

pattern as it reflects off the core cladding

 Main factor in limiting length of fiber-optic cable; longer

cable means more dispersion

Attenuation in Fiber-Optic Cable Transmission

 Extrinsic losses—Signal losses caused by

physical factors outside the normal core, such as

splices, connectors, and bends in the fiber core

 Main reasons for signal loss

 Fresnel reflection loss—A type of signal loss that

commonly occurs at connection points in fiber-

optic cabling and is due to refraction property

differences in the core material, the connector

materials used for sealing the connector, and air.

 Minimized by sealing material

Fiber-Optic Cable Specifications

 Multimode Fiber-Optic

Cable

 Single-Mode Fiber-

Optic Cable

Fiber-Optic Cable Specifications

 Multimode Fiber-Optic Cable

 Multi-mode systems usually cost less.

 Cable runs are much shorter than with single-mode,

but still much greater than coaxial cable. 2

kilometers seems to be the maximum

recommended distance.

 Multi-mode bandwidth is smaller than single-

mode—up to 1 GHz vs 100,000 GHz—but still

enough transmit a large amount of A/V signal, data,

or controls.

Fiber-Optic Cable Specifications

 Single-Mode Fiber-Optic Cable

 Light travels a longer distance inside single-mode

cable than it does inside multi-mode. Single-mode

signal can survive up to 30 kilometers.

 The bandwidth (amount of information in the signal)

of single-mode is higher than multi-mode, as much

as 100,000 GHz.

 Since the entrance pupil of single-mode is so small

(~9 microns), single-mode connectors must be kept

very, very clean. Even a microscopic particle

blocking the pupil can partially or completely block

signal.

Fiber-Optic Cable Specifications

 Graded-index multimode fiber-optic cable

 Varying grade of core material. It is designed for maximum light

conduction at the center of the core and gradually diminished light

conduction toward the cladding.

 Step-index multimode fiber-optic cable

Fiber-Optic Cable Specifications (Cont.)

IEEE 802.3 Standards

IEEE 802.3 Standards (Cont.)

Fiber Distributed Data Interface (FDDI)

 Constructed as a pair of rings

 Uses token passing media access method

 Guarantees continuous communication

 If one ring fails, the other ring automatically

provides path for communication

FDDI Fault Tolerance

Fiber-Optic Cable Connectors

Fiber-Optic Cable Connector Description

ST Round. Uses a push and twist connection

SC Square. Uses retaining clips

FC Round. Uses screw threads

LC (single) Square. Small form factor.

LC (duplex) Two single LC connectors held together with a clip

MTRJ Incorporates two fiber-optic cores into one assembly

Fiber-Optic Cable Connectors (Cont.)

Installing Fiber-Optic Cable Connectors

 Slices, couplings, and connections require special

equipment and techniques

 To cut glass core fiber-optic cable:

 Scribe the core with a sharp, cleaving tool

 Apply pressure to the scribed area

 Plastic core fiber-optic cable is cut with a sharp

cutting tool—it is not cleaved

Fusion Splice

 Before splicing, the outer sheath must be

removed from cable end

 Splice area must be clean, to avoid signal loss

 End of the fiber-optic core is cleaved, not cut

through

 Two ends of fiber core are aligned, melted

together, covered, and crimped

Fiber-Optic Cable Meters

 Power meter and light source—Most commonly used meter for testing short runs in cable  Used to calculate short runs and power loss

 Optical Time Domain Reflectometer (OTDR)  Measures and records the effects of attenuation

 Can measure cable length, locate breaks, and find faults in the cable and at its connections

 https://www.youtube.com/watch?v=8VrG3YEm0y A

https://www.youtube.com/watch?v=8VrG3YEm0yA

Questions?