EASA Fiber Optics

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Course Overview

• The nature of light• What are fiber optics• How it works• Signal loss• Types of fiber• Splicing fiber• Fiber optic data link components

Course Overview

• Fiber optic routing and installation• Fiber optic inspection• Fiber optic cleaning• Fiber optic testing

Course Activities

• Assemble D38999 connector activity

• Bundle tying activity• Assemble ARINC

connector activity• Cable routing activity• Fiber cleaning activity

• Fiber optic inspection activity

• Fiber testing activity• Remove cabling

activity• Disassemble D38999

connector activity• Disassemble ARINC

connector activity

The Nature of Light• Light• Electromagnetic spectrum• Wavelength and color• Reflection and refraction• Specular reflection• Lenses• Focal point and focal length• Dispersion

Light

• Light• Electromagnetic radiation in the form of a

wave• Travels fastest in a vacuum• Slows in transparent medium• A type of wave

Electromagnetic Spectrum

Wavelength and Color

• Shorter than 4,000 Angstrom are not visible (ultraviolet)

• Longer than 7,000 Angstrom are not visible (infrared)

• Colors change as the wavelength changeViolet Blue Green Yellow Orange Red

4,500 A 4,800 A 5,200 A 5,800 A 6,000 A 6,400 A

Wavelengths of light colors

Reflection and Refraction• Reflection

– Change in direction of lightwave returned to origin

• Refraction– Change in direction of lightwave passing

through a medium

Specular Reflection

• The normal• Angle of incidence

Lenses

• Lenses– Focus light for use

• Convex– Bulges toward light source and de-magnifies

• Concave– Bulges away from light source and magnifies

Focal Point and Focal Length

• Lens shape changes:– Focal point– Focal length

Dispersion

• Causes blurriness• Red light focuses further away than blue

light

What are Fiber Optics

• What are fiber optics• Optical fiber construction• History• Uses in aviation• Benefits of using fiber• Disadvantages of using fiber

What are Fiber Optics

• Thin glass fibers used to send data• Transmits data signal via beams of light

Optical Fiber Construction

• How It’s Made• Discovery Channel video

– http://www.youtube.com/watch?v=D4nGPI6DTLw

History

• 18th century puddles used to direct candle and sunlight for ambiance

• 19th century colored glass tubes filled with water used on stage for effects– Proved light could be bent using curved stream

• 20th century term “contained transmission of light” first used– First used to connect computers in the 70’s

Uses in Aviation

• In flight entertainment• Communications systems• Avionics systems• Flight management systems• Flight safety requires multiple

redundancies

Benefits of Using Fiber

• Weight– Carries equivalent data as 2 inch copper

bundle

• Bandwidth and speed• No electromagnetic interference• No cross talk• Uses less power• Signal security

Disadvantages of Using Fiber

• New technology• Components can be expensive• Lack of standardization in the industry• Fiber can be easily damaged if mishandled

How It Works

• How it works• Modes• Critical angle• Incident rays

How It Works

• Electrical data converted to optical signals• Signal travels down optical fiber• Optical signal converted back into useable

electrical data

Modes

• Determined by the angle the wave front makes with the axis of the fiber core

• Not entirely confined to the core• Low order modes

– Penetrate the cladding slightly

• High order modes– Penetrate further into the cladding

Critical Angle

• Maximum angle to axis that light is propagated

• Value of the angle depends on fiber properties

• Acceptance cone

Incident Rays

• Enter fiber outside acceptance cone• Light refracted into the cladding and lost

Signal Loss

• Attenuation• Discontinuity• Discontinuity demonstration

Attenuation

• Reduction in intensity• Absorption

– Imperfections– Impurities

• Scattering– Density fluctuations in the fiber

Attenuation

• Bending loss• Micro bends (pinching)

– Caused during cabling

• Macro bends– Bend radius of the cable

• Contamination• Defects

Discontinuity

• Broken or cracked optical fiber (bent straw)

• Found using visual fault locator

• Light escapes cable jacket

Discontinuity Demonstration

• Cable with broken fiber• Connect visual fault locator• Red light escapes jacket

Types of Fiber

• Single Mode• Multimode• Identifying fiber optic cables• Safety

Single Mode

• Small core typically 8 to 10 micrometers (um)

• Allows lowest order of modes• Lower signal loss due to low dispersion

Multimode

• Larger core typically 50 to 100 micrometers (um)

• The larger the core the more modes it can propagate

• Easier to launch light into fiber• Easier to make connections (splices)• Higher dispersion

Identifying Fiber Optic Cables

• Color coded cables• Color coded flagging

Safety

• Damage to eyes• Safety glasses• Pistoning fiber• Dust caps• Lockout/Tagout

Splicing Fiber

• Mechanical splice• Fusion splice• Cleaving• Problems with splices

Mechanical Splice

• Manual fiber alignment and connection

• Permanent

Fusion Splice

• Uses localized heat• Melts the two ends

together

Cleaving

• Used to cut optical fiber

• Creates perfectly flat endface

• Critical for a successful splice

Problems With Splices

• Fiber separation• Lateral misalignment• Angular misalignment• Core and cladding diameter mismatch• Poor fiber end preparation

– Not cut square– Rough polish

Fiber Optic Data Link Components

• Transmitter• Optical Cable• Connectors• Receiver

Transmitter

• Converts electrical data to light signal• Generally uses LED or lasers

Signal in Driver Source Connector Fiber

ReceiverTransmitter

Optical Cable

• Core– Made of glass– Transmits the light

• Cladding– Made of glass– Reflects light into core– Lower index of refraction

Optical Cable

• Buffer coating– Helps trap light

• Strengthening fibers– Provides axial strength

• Jacket– Outer cover– Purple for aviation

Optical Cable

• Terminus– Holds fiber in connector

• Ferrule– Holds stripped end of fiber

• End face– Polished end of a fiber

• Polish– Shape of end face

Connectors

ARINC D38999 SC

ST

Receiver

• Converts optical signal back into useable electrical data

Signal outConnector Detector Output circuit

ReceiverTransmitter

Fiber

Assemble D38999 Connector Activity• Verify proper cable placement• Install terminus into connector inserts• Install cable clamps• Cable diagram

Step 1: Verify Proper Cable Placement

• Ensure cables installed in proper connector insert

• Refer to diagram

Step 2: Install Terminus Into Connector Inserts

• Partially insert by hand• Finish using insertion tool

Step 3: Install Cable Clamps (Backshells)• Wrap cables for protection

Fiber Cable Diagram

ABCDE

ABCDE

12345

89101112

Bundle Tying Activity

• Bundle tying• Zip tie• Adhesive tie• String tie

Bundle Tying

• Wrap bundle with protective tape• Use clove hitch knot• Adhesive ties• No crossed cables

Zip Tie

• Protect cables• 4 wraps of protective

tape• Cut off excess tie flush

Adhesive Tie

• No protection tape needed

• Use Scotch Super 20• 3 wraps• Edges within .05

inches

String Tie

• Clove hitch knot• 4 wraps of protective tape• Wrap string around

bundle twice• Cross tail over other end• Stick loose end through

crossover• Pull tight• Tie square knot to secure

Assemble ARINC Connector Activity• Install inserts• Install terminus into connector inserts• Assemble Connector• Install cable clamp• Fiber cable diagram

Step 1: Install the Inserts

• Use both an A and a B insert• Align keyways• Do not force into shell if obstructed

Step 2: Install Terminus Into Connector Inserts

• Partially insert by hand• Finish using insertion tool

Step 3: Assemble Connector

• Install shell polarization keys and keyways• Use retention nut wrench to torque

jackscrew retention nut– 7 +/- 1 inch pounds

Step 4: Install Cable Clamp

• Push cable clamp onto rear surface until touching shell

• Install clamp retention nut over the end of the jackscrew

• Tighten retention nut using retention nut wrench– Torque to 7 +/- 1 inch pounds

Fiber Cable Diagram

ABCDE

ABCDE

12345

89101112

Fiber Optic Routing and Installation

• Route for protection• Precautions• Bundle tying requirements

Route for Protection

• Ensure cables do not contact sharp surfaces

• Do not use protective wrap in lieu of proper routing

• Route cables away from contact with structures, hardware and equipment

• May be routed with electrical wiring• Minimum bend radius of 1.5 inches

Route for Protection

• Use approved attach/support points• Rake cables

Clamp Ring post

Precautions

• Do not push or pull on cable• Do not kink• Maintain minimum 1.5 inch bend radius• Do not stress area where cable attaches to

connector

Bundle Tying Requirements

• Use minimum number of ties necessary

• Use protective wrap under ties

• Space 8-12 inches apart– String– Zip tie– Adhesive tie

Cable Routing Activity

• Route cable bundle on project board according to diagram

• Attach bundle using clamps and/or ring posts

• Remember to protect the cable!• Drip loops• Attach connectors

Fiber Optic Inspection

• Inspection criteria• Contamination• CleanBlast• Fiber scope

Inspection Criteria

• Cable for kinks and other damage• Use 200X magnification• No film in mating area• No particles in mating area• Few light scratches ok• No cracks in core• No pits in core

Contamination

CleanBlast

• Displays image on video screen

• Use correct adapters

Fiber Scope

• 200-400 power magnification• Use 200 power

Fiber Optic Inspection Activity

• Fiber scope– Connect fiber to scope– Identify types of contamination

• CleanBlast– Power up machine– Insert inspection probe

• Use adapter on ARINC connector

– Identify types of contamination

Fiber Optic Cleaning

• CleanBlast• Lint Free Wipe• Cleaning Swab• Pen

CleanBlast

• Uses high pressure solvent and vacuum to clean termini

• Requires adapter for connector

Lint Free Wipe

• Use clean wipe on uninstalled termini• Lay wipe flat• Isopropyl alcohol if required• Keep termini perpendicular• Wipe end face on clean area• Install dust cap immediately

Cleaning Swab

• Use each swab only once

• Use light circular motion

• Too much pressure can scratch

• Use isopropyl alcohol if required

• Install connector/dust cap immediately

Pen

• Use correct pen for ferrule size• Push straight down until it clicks• If crooked can break ferrule

Fiber Optic Cleaning Activity

• Wipes• Swabs• Pens• CleanBlast

Lint Free Wipe

• Use clean wipe on uninstalled termini• Lay wipe flat• Isopropyl alcohol if required• Keep termini perpendicular• Wipe end face on clean area• 3 or 4 passes usually enough• Inspect

Cleaning Swab

• Use each swab only once• Use light circular motion• Use isopropyl alcohol if required• Inspect

Pen

• Use correct pen for ferrule size

• Push straight down until it clicks

• If crooked can break ferrule

• Inspect

CleanBlast

• Use correct attachment• Requires adapter for ARINC

connector• Purge before use

Fiber Optic Testing

• Light source• Light meter• Test Leads• Safety reminder

Light Source

• Used to perform insertion loss measurement

• Produces light• Test cable

Light Meter

• Used with light source to measure optical power

Test Leads

• Have a known level of attenuation• Compare results with your cable

Safety Reminder

• Leave dust caps on until immediately prior to mating connectors

• Do not look at end of cable when connected to light source

Step 1: Fiber Optic Testing Activity

• Connect test lead to light source• Connect test lead to light meter• Turn on light source and light meter• Zero light meter

Step 2: Fiber Optic Testing Activity

• Connect test lead to light source• Connect test lead to light meter• Connect test leads to cable to be tested

Remove Cabling Activity

• Remove connectors from board• Remove cables from clamps and posts• Remove all ties

Disassemble D38999 Connector Activity• Remove backshell• Use removal tool carefully disengage

termini

Disassemble ARINC Connector Activity• Untie cables from connector• Use removal tool carefully disengage

termini• Remove backshell• Disassemble shell

FINAL EXAM