Systems with Higher-order Modulation
The chapter covers concepts, systems aspects, and key components for higher-order modulation. The introductory section presents relevant variants of higher-order modulation formats and includes coherent detection and coherent optical orthogonal frequency-
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Systems with Higher-order Modulation Yaakov Achiam, Arkady M. Kaplan, and Matthias Seimetz
Abstract The chapter covers concepts, systems aspects, and key components for higher-order modulation. The introductory section presents relevant variants of higher-order modulation formats and includes coherent detection and coherent optical orthogonal frequency-division multiplexing as well. The next section is devoted to system configurations with particular emphasis on transmitter structures and receiver concepts, whereas the subsequent chapter focuses on key components. Included are LiNbO3 -based quadrature modulators, integrated coherent receivers, in particular 90° hybrids, ranging from new concepts to proven implementations. A treatment of integrated balanced four-branch receivers ranges from theoretical analysis to the presentation of commercially available devices. The chapter concludes with a discussion of system trends and expected future developments.
8.1 Introduction The emerging demand for digital video over the Internet, as well as the need for storage networking, carrier wholesaling, and science applications, is prompting an exploding need for optical data transmission capacity and is transferring the Internet granularity from 10 Gbit=s to 100 Gbit=s. Yaakov Achiam (¬) 4 Tseelas St., Omer 8496500, Israel e-mail: [email protected] Arkady Morris Kaplan CeLight Inc., 12200 Tech Road, Silver Spring, 20904 MD, USA e-mail: [email protected] Matthias Seimetz Beuth Hochschule für Technik Berlin, FB VII: Elektrotechnik – Mechatronik – Optometrie, Luxemburger Str. 10, 13353 Berlin, Germany e-mail: [email protected]
H. Venghaus, N. Grote (eds.), Fibre Optic Communication – Key Devices Optical Sciences 161. DOI 10.1007/978-3-642-20517-0_8, © Springer-Verlag Berlin Heidelberg 2012
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With the objective of reducing cost per information bit in optical communication networks, per-fiber transmission capacities and optical transparent transmission lengths have been stepped up by the introduction of new technology in recent years. The innovation of the Erbium-doped fiber amplifier (EDFA) at the beginning of the nineties facilitated long distances to be bridged without electro-optical conversion. Furthermore, the wavelength division multiplex (WDM) technology, which allows a lot of wavelength channels to be simultaneously transmitted over one fiber and to be amplified by one EDFA with high bandwidth, cut the cost of the transport network and offered wide bandwidth. Since there is no drive for high spectral efficiency at that moment, the modulation format is straightforward “on-off keying” (OOK). The Internet traffic growth during the nineties required increasing transmission rates which were limited by the transmission properties of the optical fiber. In that context, the application of differential binary phased shift keying (DBPSK) became an issue, providing for a higher robustness against nonlinear effects [1]. Moreover, the transmission behavior of binary intensity modulation
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