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Descripción
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| The Coarse Wavelength Division Multiplexing technology (CWDM) enables carriers to transport more services over their existing optical fiber infrastructure by combining multiple wavelengths onto a single optical fiber. CWDM is technologically simpler and easier to implement and is a good fit for access networks and many metro/regional networks. ITU-T G.694.2 defines 18 wavelengths for CWDM, using the wavelengths from 1270 nm through 1610 nm with a channel spacing of 20 nm. This channel spacing allows to use, in CWDM systems, low-cost and uncooled lasers, e.g. direct modulated laser (DML). The high output power of commercial 1.55- ?m DMLs can provide a power budget that allows for amplifier/regenerator spacing of 80?100 km. However, the frequency chirp characteristics of DMLs significantly limit the maximum achievable transmission distance over standard single-mode fibers (SMF). A number of approaches have been used to improve transmission performance using directly modulated lasers, including cutting down the chirp externally using a narrow bandpass filter and the deployment of a negative dispersion fiber. However, typical metro and access networks are made up of a conventional single-mode fiber (SMF) and because of the cost and difficulty (or lack of feasibility) in changing embedded fiber links, a method that enhances system performance requiring only the modification of one or both of the endpoints of a link is a critical requirement. In this chapter, by means of a commercial Optical Communication System Design Software, we evaluate the interaction of fiber dispersion with the laser chirp in context of positive and negative dispersion coefficient. We evaluate two types of laser, with different characteristics and we determine optimal optical output power in every case. We have demonstrated that enhanced system performance, which uses a positive dispersion fiber, can be achieved if positive chromatic dispersion in the optical fiber is equalized by SPM, whereas laser transient chirp can be compensated using a negative dispersion fiber. | |
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Internacional
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Si |
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DOI
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10.5772/29852 |
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Edición del Libro
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1 |
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Editorial del Libro
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InTech |
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ISBN
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978-953-307-954-7 |
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Serie
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Título del Libro
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Optical Fiber Communications and Devices |
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Desde página
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55 |
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Hasta página
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76 |