Multi-gigabit/sec coherent lightwave systems

Advantages, applications, and technological challenges of coherent lightwave are discussed for multigigabit-per-second systems, and recent experimental results are reviewed. An example of a passive hub interoffice network is given as an example of the powerful frequency-division-multiplexing capability of coherent communication. Optical modulation techniques such as amplitude-shift keying (ASK) frequency-shift keying (FSK), and phase-shift keying (PSK) are discussed. Transmission characteristics of optical fibers such as low loss, wide optical bandwidth, polarization fluctuations, chromatic dispersion and nonlinear effects are also discussed. The experimental results indicate that further improvements in the optical components will be needed for practical multigigabit-per-second coherent systems