Contents: Introduction -- Theory of optical communication -- Fiber devices for optical communication systems -- Integrated devices for optical communication systems -- Direct detection optical communication systems -- Coherent systems: Structure and ideal performance -- Performance degration sources in coherent optical systems -- Multilevel coherent optical systems -- Multichannel optical systems -- Present-day systems implementations -- Appendix A: The Marcum Q function -- Appendix B: Distribution of hermitian quadratic forms of gaussian random variables -- Appendix C: The Cauchy equation and its approximations -- Appendix D: Principal states of polarization in a single-mode fiber.