Modern Trends in the Development of Network Synchronization Systems. From Plesiochronous to Coherent Networks

For new generations of communication networks, the tasks of increasing the speed and amount of transmitted information are being set, which requires the corresponding output from the network infrastructure. First of all, this concerns systems of clock and time network synchronization. The development processes of communication network technologies have led to the need for the evolution of the frequency (clock) synchronization system to time and frequency-time synchronization systems. And in the future, coherent systems of time-frequency support are already being considered. This article deals with the development of sources and the evolution of synchronization systems for telecommunication networks. It is based on the recommendations of the International Telecommunication Union and the authors' experience in this area of expertise.