Optical fiber cable Advantages of OFC Light weight
Optical fiber cable
Advantages of OFC ØLight weight ØSmaller in size and flexible ØNon conductive ØHighband width and low loss ØNo short circuit ØNo internal noise/cross talk ØWithstand moisture / temperature ØNo need of ground and voltage problem ØHighly secure communication
Total Internal Reflection I. If θ < θc, the ray will split. II. If θ =θc, the ray passes through the core cladding interface. III. If θ > θc, the entire ray reflects from the boundary. This is called total internal reflection.
When θ =θc According to Snell's law n 1 sin θc = n 2 sin 90 sin θc = n 2 /n 1 θc = sin-1 n 2 /n 1
Physical Structure of OFC
Expression for numerical aperture and acceptance angle At core cladding interface
Types of OFC 1. Based on materials (Glass and Plastic) 2. Based on number of modes (Single Mode and Multimode) 3. Based on Refractive Index (Step index and Graded index)
S. No Single Mode fiber Multimode fiber 1 Only one mode at a time is possible More than one mode at a time is possible 2 Structure Core dia = 5 – 10 μm Cladding around 125μm NA = 0. 08 to 0. 1 Bandwidth = more than 50 MHzkm 3 Properties i. Only one mode can be propagated ii. Smaller core dia and RI between the core and cladding is small. iii. High band width 4. Advantages Disadvantages i. No dispersion i. more dispersion ii. Since the information transmission capacity is inversely proportional to dispersion, these fibres used for longer distance communication short distance communication Core dia = 50 – 350 μm Cladding =125 - 500 μm NA = 0. 12 to 0. 5 Bandwidth = less than 50 MHzkm i. More than one can be propagated ii. larger core dia and RI between the core and cladding is relatively high. iii. low band width
S. No Single Mode fiber Multimode fiber 5. Disadvantages i. Launching and connecting of fibers are difficult ii. Fabrication is difficult as it is more costly Advantages i. Launching and connecting of fibers are easy ii. Less cost 6 Applications Band width is small so it can be used Used for short distance for long distance communications (LAN)
S. No Step index fiber Graded index fiber 1 Both single mode and multimode fibers Only multimode fibers 2 The light propagation is in the form of meridional rays and it passes through the fiber axis. The light propagation is in the form of skew rays and it will not cross the axis 3 The light rays take zig – zag path Helical path 4 Lower band width (multimode) Higher band width 5 Distortion is more Less 6 Number of mode Nstep = 4. 9(dx. NA/λ)2 = V 2/2 Ngrade = V 2/4 = N step/2
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