Transcript of "EASA Part 66 Module 5.10 : Fibre Optic"
5.10 FIBRE OPTIC
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 Receiver Transmitter Optical Coupling (Light (Light Source) Detector)Transmitters: Light-emitting diodes (LEDs) and Injected Lasers Convert electrical signal to optical signal. To send the optical signal over an optical fibreReceivers: Photodiodes and Phototransistors. To convert optical signal back to an electrical signalOptical 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 smoothThe light diffuse reflection if surface is irregular/rough
REFRACTIONBending of light when passes through other medium Air 1 00 Diamond 2 42 Ethyl Alcohol 1 36 Fused Quartz 1 46 Glass 1 55 - 1 9 Optical Fibre 15 Water 1 33 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 STRUCTUREHigh strength and tension resistanceTypically cable made in length of 1-3 km without splices. Core - glass, polystyrene, polymethylmethacrylic. Cladding - glass, silicon or Teflon.
TYPE OF CABLE Wide graded index multimode optical fibre Single mode step index optical fibre Large-core plastic-clad silica optical fibre
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 = sin A
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 light 2. 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