OPTIMAL TECHNOLOGIES FOR BUILDING FIBER-OPTIC ACCESS SYSTEMS
DOI:
https://doi.org/10.31891/2219-9365-2023-74-12Keywords:
digital signal processing, , analog-to-digital converter, coherent optics technology, fiber-optic telecommunication system, digital-to-analog converterAbstract
A study of technologies for the construction of optical transport networks and the architecture of access networks was carried out. The dominant optical transport technologies for the access environment are considered, in particular telecommunication digital access paths based on intensity modulation and direct detection (IM-DD). The identified characteristics and limitations of the considered telecommunication technologies are important for understanding the driving forces for the implementation of coherent optics in the access network as a long-term technological strategy.
The article discusses the schemes and principle of operation of IM-DD digital optical communication systems with various high-order modulation formats. The principles of generation, detection and recovery of PAM-4, CAP and DMT signals are also investigated. Digital signal processing (DSP), which plays a significant role in modern access systems, is considered.
The study presents digital optical transmission paths using IM-DD technology, including the direction of improvement of access systems using different high-order modulation formats and DSP means. A study of the principles of generation, detection and recovery of PAM-4, CAP and DMT signals for high-speed telecommunication access systems was carried out. In a high-speed IM-DD system, the DSP process becomes more and more important because the high-order modulation formats involved suffer from linear and non-linear channel distortions. Analysis and comparison of the complexity, performance and cost of optimal modulation formats was carried out. It has been determined that PAM signals exhibit lower complexity, simple implementation, and low power consumption when using DSP tools. Therefore, PAM-4 technology is widely used and standardized in various optical telecommunication systems. It is also determined that the transmission of information streams of 200G, 400G and more per channel becomes a rather difficult task for IM-DD systems, even with the use of the proposed high-order modulation formats. Thus, coherent optics technology will play a significant role in future high-speed optical access networks.
