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"Companies and research labs worldwide are racing to develop Dense Wavelength Division Multiplexing (DWDM) technology, a far-reaching advancement in the fiber optical communications field. To help you keep pace with these latest developments, this all-in-one resource brings you a clear, concise overview of the technology that is transporting and processing vast amounts of information at the speed of light. Until now, no book offered a practical introduction to DWDM advances.
INTRODUCTION TO DWDM TECHNOLOGY will help you learn all the essentials for this emerging field:
* Principles of physics underlying optical devices
* Optical components needed to design optical and DWDM systems
* Coding and decoding techniques used in optical communications
* Overview of DWDM systems
* State-of-the-art research trends
Complete with four-color illustrations to show how devices work, this comprehensive book provides an invaluable discussion of DWDM basics necessary for practicing electrical engineers, optical systems designers, technical managers, and undergraduate students in optical communications.
Go to htttp://www.ieee.org/organizations/pubs/press/Kartfm.pdf for a complete Table of Contents and a look at the Introduction. You can check out Chapter 5, "Optical Demultiplexers" by clicking on http://www.ieee.org/organizations/pubs/press/KartCh5.pdf
About the Author
Stamatios V. Kartalopoulos is currently on the staff of the Optical Networks Group of Lucent Technologies, Bell Labs Innovations, formerly known as AT&T. His research interests include ATM and SONET/SDH systems, ultrafast pattern recognition, IP and DWDM, access enterprise systems, local area networks, fiber networks, satellite systems, intelligent signal processing, neural networks, and fuzzy logic. He holds several patents of which six patents (and six pending) are in communications and optical communications systems."
IEEE Communications Society
"...this all-in-one resource helps you keep pace with latest developments, gives a clear concise overview of the techonolgy & offers a practical introduction to DWDM advances."
Advantages of EFDAs
Disadvantages of EFDAs
EDFAs have found applications in long-haul as well as in wavelength division multiplexing (WDM) transport systems. A fiber span (hundreds of kilometers long) consists of fiber segments (tens of kilometers each). Optical amplifiers are placed at the interconnecting points to restore the attenuated optical signal. Thus, there may be several EDFAs along the fiber span (typically up to 8). However, three issues be come important: (a) gain flatness (all wavelengths at the EDFA output should have the same optical power); (b) dynamic gain; and (c) low noise.
All wavelengths are not amplified through EDFAs in the same way; that is, the gain is not exactly flat. This issue is addressed with gain flattening optical filters. These devices are passive in-line filters with low insertion loss, low dispersion, and stable performance over a wide range of temperatures.
The power pumped in an EDFA is shared by all wavelengths. The more the wavelengths, the less power per wavelength, and vice versa. This has an undesirable effect in optical add-dropped multiplexing (OADM) VVDM with EDFAs. As wavelengths are dropped by an OADM and not added, EDFAs (in series with OADM) amplify fewer wavelengths more, and as wavelengths are added by another OADM, they are amplified less. That is, the gain does not remain at the same level from one OADM to the next. This is addressed by engineering the WDM system and dynamic gain control.
Noise is addressed differently. When engineering a fiber-optic path, it should be remembered that optical noise sources are cumulative and that the spontaneous emission of EDFAs introduces noise that degrades the S/N ratio. Thus, one may think that a strong optical signal launched into the fiber could overcome this. However, near the zero-dispersion wavelength region, four-wave mixing could become dominant and it could degrade the S/N ratio.
The selection of power (per channel) launched into the fiber becomes a puzzle: amplifier noise restricts the minimum power of the signal, and four-wave mixing limits the maximum power per channel launched into the fiber. This implies that a power level that lies between a lower and an upper limit must be selected. To determine the power level, many other parameters must be taken into account so that the required quality of signal is maintained. Some of these parameters are:
Praseodymium-Doped Fiber Amplifiers
PDFAs have a high gain (-30 dB), a high saturation power (20 dBm), and are suitable in the region 1280 to 1340 nm, where EDFAs are not. However, PDFAs require a non-silica fiber (fluoride) that is not very common, and a high-power (up to 300 mW) pump laser at 1017 nm (not the popular 980 nin or 1480 nm). Thus, presently PDFA technology is not popular or well developed yet.
Stimulated Raman and Stimulated Brillouin Scattering Amplifiers
Stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) amplifiers arc non-doped fiber amplifiers, as already described in Sections 3.20.1 and 3.20.2, that employ pump lasers to take advantage of the nonlinearity properties of the fiber. The most important feature of Raman amplifiers is that they have a wide bandwidth range that can extend over the complete useful spectrum from the 1300 nm to 1600+ nm (500 optical channels at 100-Ghz spacing) that enable a multiTerabit transmission technology, also referred to as Raman super-continuum. On the negative side, Raman amplification requires very long fibers (in the order of several kilometers) and pump lasers with high optical power (>I watt). Thermal management issues as well as safety issues are yet to be resolved.
Classification of Optical Fiber Amplifiers
Optical fiber amplifiers (OFAs) are classified in electronic amplifiers, electronic systems, and wireless systems as power amplifiers, pre-amplifiers, and line amplifiers.
Optical fiber amplifiers should be applied properly to minimize several factors that may affect the integrity of the channel and the transmitted signal due to nonlinearities, polarization, and other effects. ITU-T has recommended parameter limits as well as applications of optical fiber amplifiers in G.662 and G.663.
An OFA capable of increasing the optical power of the modulated photonic source (i.e., the optical transmitted signal) is called an optical power amplifier An optical power amplifier acts like a booster. It is placed right after the source, and thus may also be integrated with it. It receives a large signal (from the laser source) with a large signal-to-noise ratio and boosts its power to levels about - 10 dBm or higher...
FUNDAMENTALS OF LIGHT.
The Nature of Light.
Interaction of Light with Matter.
The Optical Waveguide: The Fiber.
Optical Spectral Filters and Gratings.
Other Optical Components.
Optical Add-Drop Multiplexers.
CODING OPTICAL INFORMATION.
Digital Transmission and Coding Techniques.
Decoding Optical Information.
DENSE WAVELENGTH DIVISION MULTIPLEXING.
Engineering DWDM Systems.
DWDM CURRENT ISSUES AND RESEARCH.
State of the Art.
Acronyms and Abbreviations.
About the Author.
Sunlight rays crossing the morning dew droplets formed a rainbow of colors. Thus the sun rays, composed of many colors, were demystified-what a simple observation! Sun rays, when reflected with shining bronze shields, were redirected to selected points called estiai or foci. Furthermore, concentrated rays had so much energy that they could warm up things or burn them. Soon thereafter, the glassy optical lens was produced.
It was found that rays passing through a spherical lens did not create the best focal point; today, this imperfection is known as lens sphericity. It was also discovered that shapes based on hyperbolas or parabolas were better suited to optical applications than those based on circles or spheres.
Simple experiments and observations of the past have helped our understanding about the nature of things. Yesterday's science fiction is today's reality. The electronic properties of conductors and semiconductors help to create or detect light. Three crystals, each with different impurities and fused together, created a transistor, which within a few years revolutionized the way we live. The wrist-size communicator is no longer just fantasy in comic books. Pocket-size powerful computers and credit-card-size communication devices are a reality. Low earth orbit satellite (LEOS) communication networks are not "pie in the sky," but they are roaming the silent skies. At the click of a button, one can access virtuallyany part of the globe and hear and see events as they happen. Optical fiber has wrapped around the globe like a ball of yam connecting all continents and transporting data at the speed of light. Direct-to-satellite communication enables anytime-wireless connectivity between any two places in the world, as well as providing global positioning services with accuracy of a few feet or inches! A single optical fiber can transport the information of hundreds of thousands of volumes within a second.
Posted August 19, 2003
This is one of the most poorly written and edited books I have ever read. The author's grasp of English grammar is nil, and some of the erroneous technical statements demonstrate his poor grasp of optical and semiconductor physics. Nevertheless, there are some good, if poorly explained, descriptions of several aspects of fiber optics, if one can put up with the poor grammar and editing. A much better book on the topic is Hecht's 'Understanding Fiber Optics'.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.