Technological Training

CWDM & DWDM: Fundamentals, Technology, New Test Needs, MARKET and TRENDS

Course Summary:

WDM technology (Wavelength Division Multiplexing) has revolutionized the telecommunications market in the whole world by offering a phenomenal cost-effective increase in the fiber transmission capacity. It is the best alternative to satisfy the growing demand for bandwidth current seen in worldwide telecom networks.
DWDM (Dense WDM) became commercial in 1995 while CWDM (Coarse WDM) emerged after 2000, stimulated by the telecom crisis.
CWDM brings simpler technological concepts as compared to DWDM, cutting down prices, but fits just the lower transmission capacity markets, such as the metro and enterprise networks. More than 90% of the long distance fiber links in the US and Europe already makes use of DWDM technology. Applications of C&D WDM in metropolitan, enterprise and cable television networks are also growing. The worldwide market of WDM equipments was about US$ 8,9 billion in 2000, with an annual growth (CAGR) of 73%. In 2001, annual growth rate was of 43%. Between 2001 and 2004, the market went through a deep crisis. Its recovering in the last years on its way.

Course Contents:

Review of optical communications:

Introduction
Evolution of optical communications
Some essential components

Optical fibers (types, attenuation and dispersion characteristics)
Optical splitters, combiners and couplers
Optical filters, multiplexers, demultiplexers
Transmitters and receivers

Usual multiplexing techniques in optical communications

TDM - Time-Division Multiplexing
WDM - Wavelength Division Multiplexing

SDH & SONET - Synchronous Digital Hierarchy
Other transmission protocols and respective data rates

Impairments in Optical Communications:

Optical attenuation
Chromatic dispersion
Polarization Mode Dispersion - PMD
Optical non-linearities
Optical signal to noise ratio (OSNR) and EDFA noise
Optical amplification

Fundamental characteristics
Basic configurations
Semiconductors amplifiers
Praseodymium doped fiber amplifiers (1.3mm)
Erbium doped fiber amplifiers (1.5mm)
Applications

Chromatic dispersion compensation in high capacity optical transmission systems

WDM Technology:

DWDM and CWDM driving factors
Alternatives for increasing transmission capacity
Evolution of the WDM technology
Wide-Band WDM (WWDM), Coarse WDM (CWDM) and Dense WDM (DWDM)
DWDM - Technical, economical and logistic advantages

Bandwidth, scalability, transparency to bit-rate and modulation format, cost, investment risks, installation, future proof

Technologies that made DWDM technology possible

EDFA optical amplifiers
DFB Lasers with narrow and stable line widths
Fiber Bragg gratings
AWG - Arrayed Waveguide Grating

Main DWDM network components

Fixed and tunable transmitters
Optical receivers
Flat gain EDFA amplifiers
Wavelength multiplexers and demultiplexers
Fixed and configurable optical Add-Drop multiplexers
Optical Cross-Connects

Bidirectional DWDM
Considerations about channel separation and channel selection

Channel selection and cross-talk
Channel spacing and channel count
Differences between DWDM and CWDM channel spacing
ITU standardization and frequency grid

Chromatic dispersion management and dispersion compensation in WDM systems
WDM impairments due to optical non-linearities

Raman Scattering and Brillouin Scattering
Self phase modulation and cross phase modulation
Four-wave mixing

CWDM - Characteristics, standardization and applications
CWDM - Technical, economical and logistic advantages
Comparisons between DWDM and CWDM
Network investments - important evaluations in the decision making process
New optical fibers for DWDM and CWDM - Which to choose?

Dispersion characteristics, effective area, second order dispersion
Advantages and disadvantages in DWDM and CWDM

TDM versus CWDM & DWDM, STM-16 versus STM-64 and STM-256*

Which and/or when each alternative is better

Open architecture versus closed architecture in DWDM
Protection, restoration and reliability in the optical layer
CWDM & DWDM solutions available in the market
Interoperability between suppliers
Network design methodology
Case studies

Tests and Measures in WDM Networks:

Spectral measurements in WDM
Essential characteristics of the OSA
Technologies of spectral analysis

The Optical Spectrum Analyzer (OSA)
Wavelength Meter
Tunable filter based equipments

Required tests and measurement parameters

Components
System performance
Field installation and maintenance

Use of OSA in the installation, monitoring and fault repairing of WDM networks
WDM test equipment suppliers
Specialized diagnostics of optical networks
PMD audits in the American, Swedish and Brazilian fiber plants

Technological trends in WDM optical networks:

Networks centered in voice services versus networks centered in data services
IP and ATM over WDM
The optical internet and MPLS
DWDM and CWDM in Metropolitan Area Networks (MAN's)
The LAN invades the WAN and WAN invades the LAN
CWDM in 850nm and multimode optical fibers
L-band EDFA optical amplifier (1570-1620nm)
Ultra-wide band EDFA optical amplifier (1530-1620nm)
Raman optical amplifiers
DWDM in dispersion shifted (DS) fibers
Dispersion compensation in DWDM systems using fiber Bragg gratings (FBG)
40 Gbit/s TDM systems
Optical TDM - OTDM
Link PMD
PMD compensation
Forward Error Correction - FEC
DWDM in CATV networks
FSO (Free Space Optical) communication systems - the optical wireless success
Photonic or all optical networks

Optical routing, network architectures, evolution, optical layer
Elements of second-generation networks

Optical add-drops, optical routers
Electrical cross-connects, optical cross-connects, wavelength converters

CWDM & DWDM Market:

DWDM & CWDM market driving factors
Market euphoria, crisis and recovering
World-wide DWDM market
World-wide CWDM market
CWDM & DWDM - Main world-wide system supliers
CWDM & DWDM system cost

Duration: 24 Hours

Instructor: Sergio Barcelos, PhD

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