Abstract
The expansion of digital coherent optical communication technologies to metro-area networks is
accelerating the development of compact and energy efficient transceivers. To meet the strong demands
for a smaller footprint and lower power consumption, such optical devices as tunable lasers, modulators,
and coherent receivers, which consist of coherent transceivers, must also be more compact and efficient.
This paper reviews the technologies of coherent transceivers and related optical devices by focusing on
the development of optical devices using InP-based monolithic integration technologies. We also
describe the current status of the development and the activities for the next generation networks with
higher bit rates, such 400 Gbit/s and 1 Tbit/s.
