Principle of Coherence Optical Systems-Current Applications and Future Challenges

This paper reviews the concept of coherent optical systems as future digital optical communication systems having capacity of achieving 100Gbps speed. While the transmission capacity increases in wavelength-division multiplexed (WDM) system, coherent technologies have been in large interest in recent years. The interest lies in finding methods of increasing the bandwidth demand with multilevel modulation formats based on coherent technologies. We also discuss about requirements and challenges in implementation of respective digital receivers and associated signal processing.