1 / 10

4. ATTENUATION

4. ATTENUATION. 4.1 Classification 4.2 Intrinsic Losses 4.3 Extrinsic Losses 4.4 Nonlinear Effects 4.5 Total Losses. 4.1 CLASSIFICATION. 1st Classification Intrinsic: inherent to the material (unavoidable) Extrinsic: due to manufacture processes (avoidable) 2nd Classification

rufin
Download Presentation

4. ATTENUATION

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 4. ATTENUATION 4.1 Classification 4.2 Intrinsic Losses 4.3 Extrinsic Losses 4.4 Nonlinear Effects 4.5 Total Losses

  2. 4.1 CLASSIFICATION • 1st Classification • Intrinsic: inherent to the material (unavoidable) • Extrinsic: due to manufacture processes (avoidable) • 2nd Classification • Absorption: photons’ energy is taken up by matter • Scattering: photons are deviated from a straight trajectory • Radiation: light is radiated outside • 3rd Classification • Linear Processes: spectrum maintains its shape • Nonlinear Processes: spectrum’s shape changes

  3. 4.2 INTRINSIC LOSSES (I) • Rayleigh Scattering • Linear, intrinsic, scattering • Due to refractive index thermal fluctuations • Inversely proportional to 4

  4. 4.2 INTRINSIC LOSSES (II) • Why Is the Sky Blue? We see blue light from Rayleigh scattering off the air (L) L  -4 blue (f, )  L red (f, )  L Why is the sunset reddened? SUN SUN

  5. 4.2 INTRINSIC LOSSES (III) • Intrinsic Absorption • Ultraviolet absorption • Interaction photon/atom • Photon excites an electron (jumps to conduction band) • It decreases when λ is higher • Infrared absorption • Interaction photon/molecule • Photon energy is converted into atomic vibration • It increases when λ is higher • Intrinsic losses limit available fiber windows

  6. 4.2 INTRINSIC LOSSES (IV) • Intrinsic Losses Graphic

  7. 4.3 EXTRINSIC LOSSES • Absorption Losses • Losses by ion resonance. E.g. OH─ (→water) • Water is extremely hard to eliminate • Absorption peaks: 1380, 950, 720 nm • Purity requirements: 1 ion per million → 1 dB/km more (950 nm) • Fiber Bending • More rays escape into the cladding • Limits bend radius • Criterion: r  10 (: total diameter, including coating)

  8. 4.4 NONLINEAR EFFECTS • Fundamentals • They limit system capacity • Causes • Interactions between photons and fiber • Refractive index varies with power (power density) • Types • Four-Wave Mixing: several waves mix → intermodulation products • Stimulated Brillouin Scattering: mechanical (acoustic) vibrations • Stimulated Raman Scattering: molecular vibrations • Management • Several wavelengths will mix (FWM) • Singlemode (small core) has higher power densities • Maintain power levels under threshold (3 mW avoids nonlinearities)

  9. 4.5 TOTAL LOSSES (I) • Total Losses Calculation TOTAL LOSSES MINIMUM AT 1550 nm

  10. 4.5 TOTAL LOSSES (II) • Attenuation Windows

More Related