《光纤通信课程设计》课件：Class7-03.pptVIP

Fiber Optic Network DesignX. Wu, M. Y. Li, C. S. YanDept. of Opt. Engr., ZJU2011Class 7 ?Raman Fiber AmplificationEDFAStructureParametersSelectionGain flatteningExercise Reasons to use the optical amplifiers: Broadband: possible for the S-band and even 2nd windowExcellent for ultra long-haulHigh channel count (more than 80)High modulation speed (40Gbit/s)Low noiseLonger distances between regeneration Raman Fiber Amplifier Amplification Mechanism SRS Stimulated Raman ScatteringElastic scatteringInelastic scatteringA lower frequency signal photon Induces!!! the inelastic scattering of a higher-frequency pump photon in an optical medium in the nonlinear regime. Raman Effect: Inelastic scattering of a photonDiscovered by C. V. Raman in 1928, Nobel Prize in 1930 When light is scattered from an atom or molecule, most photons are elastically scattered (Rayleigh scattering), a small fraction of the scattered light (approximately 1 in 10 million photons) is scattered by an excitation, with the scattered photons having a frequency different from, and usually lower than, the frequency of the incident photons. In a gas, Raman scattering can occur with a change in vibrational or rotational energy of a molecule. Occurs in liquids, gases, and solids Raman Effect: Inelastic scattering of a photon Raman Effect in Silicate GlassOne signal photon in, two out! Raman Fiber Amp: Characteristics No need of doped fiber，transmission fiber-gain medium Nonlinear effect Detune 100nm, amplify any band by choosing appropriate pump wavelengths Multi-pump configuration - flat-gain broadband amplification Simple structureDisadvantagesStrong pumping powerRaman effect: conversion from higher - lower frequency - cross-talk - noise Raman Effect: Inelastic scattering of a photonDiscovered by Sir Chandrasekhara Venkata Raman, Nobel Prize in 1930 When light is scattered from an atom or molecule, most photons are elastically scattered (Rayleigh scattering), a small fraction of the scattered light (appro