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2009
Book Article
Titel
Receiver configurations
Abstract
This chapter describes receiver configurations for the detection of optical signals with high-order modulation. At the beginning of the chapter, receiver key components (filters, delay line interferometer, optical hybrids) are discussed. Afterwards, receivers are detailed for three different detection schemes: direct detection, homodyne differential detection and homodyne synchronous detection. A complete analytical description of the optical and electrical receiver parts is thereby provided, starting with optical frontends and ending with electrical data recovery. Direct detection receivers are shown to be capable of detecting arbitrary modulation formats with differentially encoded phases such as DPSK and Star QAM formats. Subsequently, homodyne receivers with differential detection are presented and shown to be suitable for detecting the same signals as is possible with direct detection. Finally, homodyne synchronous detection which is appropriate for arbitrary high- order modulation formats is highlighted. A particular stress is laid on carrier synchronization, which was traditionally performed using an optical phase locked loop. Its current state is briefly reviewed. Digital phase estimation schemes are discussed in more detail, because digital coherent receivers gain more and more interest due to high-speed digital signal processing newly available.