optical fiber waveguids step index vs graded index step index vs graded index single mode vs...

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  • Slide 1
  • Optical fiber waveguids Step index vs graded index Step index vs graded index Single mode vs multimodes Single mode vs multimodes Glass fibers vs plastic fibers Glass fibers vs plastic fibers Specialty fibers: Specialty fibers: Dispersion shifted fibers Doped fibers Coated fibers
  • Slide 2
  • Optical fiber waveguids Specialty fibers: Specialty fibers: Dispersion Shifted Fiber (DSF) has zero dispersion around 1550 nm to help transmission at these wavelengths Dispersion Compensating Fiber (DCF) has highly negative dispersion at 1550 nm to compensate for a buildup of positive dispersion in that region in conventional fiber Large Effective Area Fiber allows the light to be transmitted in a larger total area of the fiber in order to reduce the concentration of high powers that may cause adverse nonlinear effects Non-Zero Dispersion Shifted Fiber (NZ-DSF) gives a small amount of dispersion in the 1550 nm region, which can reduce the effects of four-wave mixing All Wavelength Fiber removes the attenuation peak at 1400 nm to increase the range of possible wavelengths that can be transmitted at low loss
  • Slide 3
  • Fiber Manufacture Direct Fiber manufacture: Double Crucible Direct Fiber manufacture: Double Crucible Fiber Preforms Fiber Preforms External Deposition Internal Deposition Axial Deposition Fiber Draw Fiber Draw Step Index fibers Graded Index fibers
  • Slide 4
  • Preform Manufacturing External Deposition External Deposition External CVD, OVPO, OVD External CVD, OVPO, OVD Axial Deposition Axial Deposition AVD, VAD AVD, VAD Both step and graded index fibers Both step and graded index fibers
  • Slide 5
  • Preform Manufacturing Internal Deposition Internal Deposition Interbal CVD, MCVD, IVD Interbal CVD, MCVD, IVD 30-100 layers 30-100 layers Plasma-enhanced MCVD Plasma-enhanced MCVD
  • Slide 6
  • Fiber Drawing Speed: 1-10 m/s Speed: 1-10 m/s Coating: buffer needed to protect the fiber from moisture and strengthen it Coating: buffer needed to protect the fiber from moisture and strengthen it Proof-tested Proof-tested Preform is 1-6 cm in diameter, and 1-2 m in length Preform is 1-6 cm in diameter, and 1-2 m in length 15-100 km fiber 15-100 km fiber
  • Slide 7
  • Fiber Properties Attenuation Attenuation Light collection and propagation Light collection and propagation Dispersion Dispersion Information capacity Information capacity Nonlinear effects Nonlinear effects Brillouin scattering Raman Scattering Mechanical properties Mechanical properties
  • Slide 8
  • Properties: Light collection Step index Fiber Critical Angle Critical Angle Fractional refractive index, =(n 1 -n 2 )/n 1 Fractional refractive index, =(n 1 -n 2 )/n 1 Need for cladding Need for cladding Types of SIF Types of SIF Common size designation: 50/125, 62.5/125, 100/140 Common size designation: 50/125, 62.5/125, 100/140 Index profile Index profile
  • Slide 9
  • Properties: Light collection Step index Fiber NA NA Cladding modes Cladding modes Cladding modes can be suppressed by matched buffer Cladding modes can be suppressed by matched buffer Common specifications Common specifications
  • Slide 10
  • Properties: Light collection Graded index Fiber GRIN Index profile GRIN Index profile n(r)=n 1 [1-2(r/a) ] 1/2, ra n(r)=n 1 [1-2(r/a) ] 1/2, ra Light propagation Light propagation NA and acceptance angle NA and acceptance angle n(r)=n 1 [1-2 ] 1/2 =n 2, r>a n(r)=n 1 [1-2 ] 1/2 =n 2, r>a =(n 2 1 -n 2 2 )/2n 2 1 (n 1 -n 2 )/n 1 =(n 2 1 -n 2 2 )/2n 2 1 (n 1 -n 2 )/n 1 Layers model Layers model Figures charts images\step1.gif Figures charts images\step1.gif Figures charts images\step1.gif Figures charts images\step1.gif Figures charts images\grin1.gif Figures charts images\grin1.gif Figures charts images\grin1.gif Figures charts images\grin1.gif
  • Slide 11
  • Properties: Light collection Graded index Fiber GRIN NA and acceptance angle GRIN NA and acceptance angle n(r)=n 1 [1-2(r/a) ] 1/2, ra n(r)=n 1 [1-2(r/a) ] 1/2, ra n(r)=n 1 [1-(r/a) ], ra n(r)=n 1 [1-(r/a) ], ra n 2 =n 1 [1- ], r>a n 2 =n 1 [1- ], r>a Coupling function of r Coupling function of r SI Coupling > GRIN Coupling SI Coupling > GRIN Coupling When =2, core index: When =2, core index: When