easa part 66 module 5.10 : fibre optic
DESCRIPTION
What is fibre optic and application on aircraft Other presentation canbe found at http://part66.blogspot.comTRANSCRIPT
WHAT IS FIBRE OPTIC
• Flexible, transparent fiber made of a pure glass (silica).
• It functions as light pipe, to transmit light between the two ends of the fiber.
• It is an opto-electronic component (sensitive to infrared, ultra violet that convert to electrical signal)
• Use in medical, telecomunication and aviation field.
ADVANTAGE
• Larger data carry – up to 3300MHz• Low loss of signal• Smaller diameter, lighter-weight cables• Cross talk negligible – no effect to other cable(signal)• Immunity to electromagnet interference• Greater security – immune to wiretapping• Greater safety – free from spark• Low cost – material sand• Long life span – double from conventional cable• Greater reliability – resistance to corrotion and temp
DISADVANTAGE
• Installation cost high• Fragile than wire• Required special equipment for testing• Required special skill and equipment to
splicing it
OPERATION
Transmitter (Light Source)
Receiver (Light
Detector)
Optical Coupling
Transmitters: Light-emitting diodes (LED's) and Injected Lasers Convert electrical signal to optical signal.
To send the optical signal over an optical fibre
Receivers: Photodiodes and Phototransistors.To convert optical signal back to an electrical signal
Optical Coupling:Opto-isolators and Optical fibres
LIGHT
• Light wave more shorter than electromagnetic wave (radio/radar).
• Velocity 3x108m/s, change depend on medium.
• Propogation of light :– Reflection– Refraction– Dispersion
REFLECTIONThe light reflect back with same angle if surface is smooth
The light diffuse reflection if surface is irregular/rough
REFRACTIONBending of light when passes through other medium
Air 100
Diamond 242
Ethyl Alcohol 136
Fused Quartz 146
Glass 155 - 19
Optical Fibre 15
Water 133
Index of refraction
DISPERSION
• Seperation of white light to the various color.• Different color have a different wavelength,
different velocity and different index of refraction.
CABLE STRUCTURE
Core - glass, polystyrene, polymethylmethacrylic.Cladding - glass, silicon or Teflon.
High strength and tension resistanceTypically cable made in length of 1-3 km without splices.
TYPE OF CABLE
Wide graded index multimode optical fibre
Single mode step index optical fibre
Large-core plastic-clad silica optical fibre
HOW IT WORKSingle Mode
Multimode
ACCEPTANCE ZONE
NUMERICAL APERTURE
• Its a colecting power of an optical fibre• Its value from 0 to 1, • Larger NA mean the greater amount light
accepted by fibre.• NA is function of refractive index of the fibre.• Define as NA = sinA
PULSE SPREADING
• The amount of acceptance signal have a limited frequency due to the pulse(light) is being dispers inside the cable.
• Dispersion tend to slow down the speed of the light.• Two form of dispersion :
– Chromatic disepersion : Different speed due to color
– Modal dispersion : Zigzag ray reach the end of cable later than straight ray
• Total Dispersion = Chromatic + Modal
CONSEQUENCES
• The fastest the pulse travel, the worse spreading its get.
• Need to limit the frequency of the signal travel
ATTENUATION
• Reduction of signal strength due to :1. Atomic Absorption :
Atom of material absorb some of the light2. Scatering by Flaw and Impurities :
Depend on size of scatering particle inside the cable
3. Reflection by Splices and Conector : Some light are reflected back even for
perfect splice or conector.
JOINING OPTICAL FIBRE
– Fusion Splicing• Allign manually using micromanipulators and
microscope system.• End of fibre are melt together using electric arc.• Near perfect splice can lose as low 0.2dB
– Mechanical Splicing• Two fibre end held together in splice equipment which
automatically allign the two fibre.• Clamp it and expose to ultra-violet light to cures the
cement
SPLICING ERROR
• The end of fibre must be precisely line each other to enable light pass from one fibre to another.
• Typicall allignment error :
FIBRE OPTIC CONNECTOR2 Type Conector A and B, both have :- Allignment key and grooves- Guide pin and cavities- Color bands- Three start threads
A type :- 3 or 5 optical fibre - Multichannel- very low loss
B type :- For LRU- Multichannel- For more frequent conection and disconection
FIBRE OPTIC IN AIRCRAFT
• Advantage on aircraft :– Can carry more data– Less weight– Immune to electromagnetic radiation
• Purpose:– Network system: (OLAN),(AVLAN),(CABLAN)
AIRCRAFT NETWORK SYSTEM
• Flight attendent– Keep sales data– Enable and disable passenger functions– Control the distribution of video entertainment– Select boarding music
• Passenger– Video and menu screen– Games– Inflight sales catalogue– Instruction for telephone call– Ground to airplane telephone pages– Special video channel selection
ONBOARD LAN
CABIN LAN