Optical Fiber Communication | FTTH
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A comprehensive look at Optical Fiber Communication and the technology headed our way - FTTH.
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Optical Fiber Communication | FTTH
- 2. CONTENTS Introduction to fiber optics and its Evolution Basics of optical fiber Color coating Wavelength bands-Transmission windows Types of optical fibers Advantages and Disadvantages Applications Connectors Adapters Attenuators Losses in optical fiber Splitters and types Field assembly connectors Cables and types Splicing and types Wavelength Division Multiplexing and Types
- 3. INTRODUCTION Communications systems that carry information through a guided fiber cable are called fiber optic systems. Use of optical fibers to replace conventional transmission lines and microwave wave-guide in telecommunication systems. Light is effectively the same as RF radiation but at a much higher frequency, theoretically the information-carrying capacity of a fiber is much greater than that of microwave radio systems. As they are not electrically conductive, hence very suitable for use in areas where electrical isolation and interference are severe problems.
- 4. EVOLUTION OF FIBER 1880 – Alexander Graham Bell 1930 – Patents on tubing 1950 – Patent for two-layer glass wave-guide 1960 – Laser first used as light source 1965 – High loss of light discovered 1970s – Refining of manufacturing process 1980s – OF technology becomes backbone of long distance telephone networks in NA.
- 5. OPTICAL FIBER Optical fiber is made from thin strands of either glass or plastic It has little mechanical strength, so it must be enclosed in a protective jacket Often, two or more fibers are enclosed in the same cable for increased bandwidth and redundancy in case one of the fibers breaks It is also easier to build a full-duplex system using two fibers, one for transmission in each direction
- 6. TOTAL INTERNAL REFLECTION Optical fibers work on the principle of total internal reflection With light, the refractive index is listed The angle of refraction at the interface between two media is governed by Snell’s law:
- 7. REFRACTION angle of incidence normal air glass angle of refraction
- 8. NUMERICAL APERTURE The angle of acceptance is twice that given by the numerical aperture
- 9. RAYLEIGH'S SCATTERING Rayleigh scattering is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. It can occur when light travels through transparent solids and liquids, but is most prominently seen in gases.
- 10. FRESNEL’S REFLECTION When light moves from a medium of a given refractive index n1 into a second medium with refractive index n2, both reflection and refraction of the light may occur. The relationship between these angles is given by the law of reflection:
- 12. WAVELENGTH BAND Fiber optic system transmit using infrared light, invisible to human eye, because it goes further in the optical fiber at those wavelength.
- 13. TRANSMISSION WINDOW Band Wavelength range Description O- band 1260 nm- 1360 nm Original band E- band 1360 nm- 1460 nm Extended band S- band 1460nm- 1530 nm Short wavelength band C- band 1530 nm- 1565 nm Conventional band L- band 1565 nm- 1625 nm Long wavelength band U- band 1625 nm- 1675 nm Ultra long wavelength band
- 14. FIBER COMPOSITION Core – thin glass center of the fiber where light travels. Cladding – outer optical material surrounding the core Buffer Coating – plastic coating that protects the fiber.
- 15. TYPES OF OPTICAL FIBERS OPTICAL FIBERS SINGLEMODE FIBERS MULTIMODE FIBERS STEP INDEX GRADED INDEX OM1/OM2/OM3 STEP INDEX
- 16. SINGLE-MODE STEP-INDEX FIBER Used to transmit one signal per fiber. Used in telephone and cable TV. They have small cores(9 microns in diameter) . Transmit infra-red light from laser.
- 17. MULTI-MODE STEP-INDEX FIBER Used to transmit many signals per fiber. Used in computer networks. They have larger cores(62.5/50 microns in diameter) Transmit infra-red light from LED.
- 18. MULTI-MODE GRADED-INDEX FIBER Core diameter : 50/62.5 microns. Cladding size: 125-140 microns. Refractive index changes continuously. Low dispersion. Core refractive index is made to vary as a function of the radial distance from the center of the fiber.
- 19. OM1/OM2/OM3 OM1: refer to the commonly used 62.5/125 multimode fiber. OM2: refer to the commonly used 50/125 cable. Both OM1 and OM2 easily supports applications ranging from Ethernet to gigabit Ethernet. OM3: Typically this fiber optic patch cable is with 50/125 multimode fiber, with aqua jacket. They support bandwidth up to 10GB upto 300 meters.
- 20. ADVANTAGES Wide bandwidth Light weight and small size Immunity to electromagnetic interference Lack of EMI cross talk between channels Lack of sparking Compatibility with solid state sources Low cost No emission licenses
- 21. DISADVANTAGES High investment cost Need for more expensive transmitters and receivers Fragility Opaqueness Requires special skills
- 22. APPLICATIONS Telecommunications Local Area Networks Cable TV CCTV Optical Fiber Sensors Video Surveillance Links
- 23. FIBER OPTIC CONNECTORS Terminates the fibers Connects to other fibers or transmission equipment
- 24. FIBER CONNECTOR TYPE E 2000 LC SC FC MT- RJ MPO FSMA FDDI ST BICONIC
- 25. FERRULE POLISH To avoid an air gap Ferrule is polished flat, or Rounded (PC—Physical Contact), or Angled (APC) Reduces reflectance Cannot be mated with the other polish types
- 28. ATTENUATORS VARIABLE ATTENUATORS Ideal for adjusting OEM systems in production and lab applications. These attenuators also exhibit low back reflection and good temperature stability. FIXED ATTENUATORS Fixed attenuators can limit, or attenuate. The amount of light passing through to the exact level your project. Used in applications where a pre-determined amount of light loss is specified. Most commonly used for test and measurement, optical sensors, and telecommunications applications.
- 30. LOSS MECHANISM
- 31. DISPERSION
- 32. MODAL DISPERSION Modal dispersion is a distortion mechanism occurring in multimode fibers and other waveguides, in which the signal is spread in time because the propagation velocity of the optical signal is not the same for all modes.
- 33. POLARIZATION MODE DISPERSION A special case of modal dispersion is polarization mode dispersion (PMD), a fiber dispersion phenomena usually associated with single-mode fibers. PMD results when two modes that normally travel at the same speed due to fiber core geometric and stress symmetry, travel at different speeds due to random imperfections that break the symmetry
- 34. CHROMATIC DISPERSION Dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency. Dispersion is sometimes called chromatic dispersion to emphasize its wavelength-dependent nature.
- 35. SPLITTERS A splitter is a device used to split the cable signal if the signal must be sent to two or more devices. Optical splitters are also known as couplers. They are base on the type of cable management product they will be using. Performance specifications of the splitters are given by the ITU- T G671 standard.
- 37. FUSED BICONICAL TAPER SPLITTER These are also known as singlemode splitters.. Operating wavelength is 1310nm or1550nm and the passband is 80nm. The coupling ratio can change from 1:99 to 50:50. Low insertion loss. Low excess loss. High directivity. Low polarization related loss. More channels.
- 38. PLANAR LIGHTWAVE CIRCUITS These type of splitters are smaller in footprint. They offer slightly better losses across their split ratios than FBTs Low insertion loss. Low excess loss. High directivity. High stability.
- 39. FIELD ASSEMBLY CONNECTORS Designed for simple and fast field termination of single fibers, without polishing or adhesives. The heart of the Quick-SC fast connector is a pre-polished ferrule and a mechanical splice inside the connector body. Compatible with conventional SC and LC connector. Easy and fast assembly without special tool Reliable assembly with Assembly Jig and Fiber Holder appended to connector kit
- 40. CABLES Fiber optic "cable" refers to the complete assembly of fibers, strength members and jacket. Fiber optic cables come in lots of different types, depending on the number of fibers and how and where it will be installed. There are classified as : Cables (armored) Cables (unarmored) Distribution cables Drop cables
- 45. SPLICES Splices are a permanent join of two fibers Lower attenuation and reflectance than connectors Stronger and cheaper than connectors Easier to perform than connectorization Mass splicing does 12 fibers at a time, for ribbon cables SPLICER
- 46. FUSION SPLICING Melts the fibers together to form a continuous fiber Expensive machine Strongest and best join for singlemode fiber May lower bandwidth of multimode fiber
- 47. MECHANICAL SPLICING Mechanically aligns fibers Contains index-matching gel to transmit light Equipment cost is low Per-splice cost is high Quality of splice varies, but better than connectors Fiber alignment can be tuned using a Visual Fault Locator
- 48. COMPARISON Mechanical splicing Reflection losses (-45 db to -55 db) Insertion loss (0.2 db) cost – high Fusion splicing No reflection losses Very low insertion loss (0.1 db to .15 db) Comparatively less
- 49. WAVELENGTH DIVISION MULTIPLEXING Data from each TDM channel is loaded on one optical frequency (or wavelength, ) of a particular wavelength band These wavelengths are then multiplexed onto one fiber with the help of WDM multiplexers Other side of the network these wavelengths are demultiplexed by using either optical filters, gratings or WDM demultiplexer
- 50. DENSE WAVELENGTH DIVISION MULTIPLEXING Can achieve high system capacity by multiplexing more WDM channels, each with relatively low data rate Consist of a WDM combined with an optical amplifier, to allow multiple wavelengths on a single fiber and also avoid individual regeneration equipment for each wavelength by use of line amplifiers
- 51. COARSE WAVELENGTH DIVISION MULTIPLEXING o The total CWDM optical span to somewhere near 60 km for a 2.5 Gbit/s signal. oCWDM is also being used in cable television networks, where different wavelengths are used for the downstream (1310 nm) and upstream (1550 nm) signals. o Signals are not spaced appropriately for amplification by EDFAs. o Passive CWDM is an implementation of CWDM that uses no electrical power and separates the wavelengths using band pass filters and prisms.
- 52. ANY QUESTIONS OR COMMENTS?