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    EE 230: Optical Fiber Communication Lecture 4 Fiber Dispersion

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    mofiw
    This document discusses fiber dispersion in optical fiber communication. There are four main types of dispersion: modal, material, waveguide, and polarization mode dispersion. Fiber dispersion causes pulses to broaden as they propagate through the fiber due to the fact that different wavelength components of the pulse travel at different speeds. Dispersion-shifted and dispersion-flattened fibers were developed to reduce dispersion effects and allow for higher data rates over longer distances. The document provides examples of dispersion characteristics for different fiber types.

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    EE 230: Optical Fiber Communication Lecture 4 Fiber Dispersion

    Uploaded by

    mofiw
    62 views17 pages
    This document discusses fiber dispersion in optical fiber communication. There are four main types of dispersion: modal, material, waveguide, and polarization mode dispersion. Fiber dispersion causes pulses to broaden as they propagate through the fiber due to the fact that different wavelength components of the pulse travel at different speeds. Dispersion-shifted and dispersion-flattened fibers were developed to reduce dispersion effects and allow for higher data rates over longer distances. The document provides examples of dispersion characteristics for different fiber types.

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    Lecture 4

    Original Title

    Lecture 4

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    This document discusses fiber dispersion in optical fiber communication. There are four main types of dispersion: modal, material, waveguide, and polarization mode dispersion. Fiber dispersion causes pulses to broaden as they propagate through the fiber due to the fact that different wavelength components of the pulse travel at different speeds. Dispersion-shifted and dispersion-flattened fibers were developed to reduce dispersion effects and allow for higher data rates over longer distances. The document provides examples of dispersion characteristics for different fiber types.

    Copyright:

    © All Rights Reserved
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    62 views17 pages

    EE 230: Optical Fiber Communication Lecture 4 Fiber Dispersion

    Uploaded by

    mofiw
    This document discusses fiber dispersion in optical fiber communication. There are four main types of dispersion: modal, material, waveguide, and polarization mode dispersion. Fiber dispersion causes pulses to broaden as they propagate through the fiber due to the fact that different wavelength components of the pulse travel at different speeds. Dispersion-shifted and dispersion-flattened fibers were developed to reduce dispersion effects and allow for higher data rates over longer distances. The document provides examples of dispersion characteristics for different fiber types.

    Copyright:

    © All Rights Reserved
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    of 17

    EE 230: Optical Fiber Communication Lecture 4

    Fiber Dispersion

    From the movie


    Warriors of the Net

    Types of Dispersion
    Modal dispersion: different modes
    propagate at different group velocities
    Material dispersion: the index of
    refraction of the medium changes with
    wavelength
    Waveguide dispersion: index change
    across waveguide means that different
    wavelengths have different delays
    Polarization mode dispersion: if
    waveguide is birefringent

    Definitions
    Group velocity
    Group delay
    Dispersion


    vg

    c k

    Wave Packet Construction

    Group and Phase Velocity

    Transform Limited Frequency Spread

    Rectangular Pulse

    Pulse modulated Sine wave

    Gaussian modulated Sine wave

    Optics-Hecht & Zajac

    Spectral properties of digitally modulated


    signals1
    0

    1
    NRZ
    Encoded
    Data
    RZ
    Encoded
    Data

    Pow
    er

    Bit
    Time T

    Time

    1/T

    2/T
    3/T
    Frequency

    No spectral component at the clock frequency


    For Non-Return to Zero Encoded Data

    Pulse Propagation through Fibers

    Response of a multi-mode fiber to a single


    short pulse

    Broadening of a short pulse after transmission


    through different types of fibers

    Fundamentals of Photonics - Saleh and Teich

    Material Dispersion
    Refractive Index of Pure Silica and its derivatives

    Material Dispersion Parameter for pure silica


    and germanium doped silica
    Optical Fiber Communications-Keiser

    Fiber Optic Communications-Palais

    Zero Dispersion Slope

    Fiber Optics Communication Technology-Mynbaev & Scheiner

    Fiber Dispersion
    Dispersion:The change in speed of propagation with wavelength

    Pulse Degradation from Dispersion

    Typical fiber Dispersion Curve


    Ray optics View of the origin of waveguide dispersion

    Polarization Mode Dispersion

    Polarization Maintaining Fiber

    Non-Polarization Maintaining Fiber

    Random power transfer occurs between different polarization modes


    as the pulse propagates, if the two modes have different propagation velocities
    then the pulse will broaden

    Representative Fiber Characteristics

    Dispersion for various Fiber Types

    Dispersion Shifted and Dispersion


    Flattened Fibers

    Chromatic Dispersion Parameters of


    a singlemode fiber

    Fundamentals of Photonics - Saleh and Teich

    Waveguide Dispersion mechanism


    AsMode field diameter
    More of the mode travels in the cladding.
    Cladding index is lower so pulse velocity
    resulting in dispersion

    Comparison of Dispersion Characteristics

    Propagation of Gaussian Pulses

    Input Pulse

    Output Pulse
    chirped and broadened

    2<0 for standard single mode silica fiber


    and Ld ~ 1800 km at 2.5 Gb/s and ~115 km at 10 Gb/s

    Input Pulse
    Already Positively
    Chirped

    After some distance


    the chirp is removed
    and the pulse assumes its
    minimum possible width

    Upon further propagation


    the pulse will continue to broaden
    and acquire chirp.

    Optical Networks a Practical Perspective-Ramaswami and Sivarajan

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