ABSTRACT
Chapter 7 discussed the detection of optical signals by the direct conversion of optical signal power to electronic current in the photodiode followed by electronic amplifi cation. This chapter gives a fundamental understanding of coherent detection of optical signals that requires the mixing of optical fi elds of the optical signals and that of the local oscillator, a high-power laser, so that its beating product would result in modulated signals preserving both its phase and amplitude characteristics in the electronic domain. Optical preamplifi cation in coherent detection will be discussed in Chapter 10.
