Today’s society relies on fast and reliable exchange of information. Advanced communication systems support the
operation of industries, businesses and banks; vehicles and transportation systems; household entertainment electronics and the global flow of news and knowledge. High-quality transmission of real-time video reduces the need for energy-consuming transportation of documents and people, thereby contributing to a sustainable environment. Numerous emerging services and applications, for example, medical diagnosis and treatment, traffic safety and guidance and the Internet of things, are waiting around the corner, stretching the needs for high-capacity communications even further. The long-term trend is illustrated in the figure attached, which shows the dramatic growth of global Internet traffic, according to Cisco’s statistics and predictions.
The information highways that make these services possible consist almost exclusively of optical fibers. No other
known medium can support the massive demands for data rate, reliability and energy efficiency. After pioneering
experiments in the 1960s and 70s, optical fibers were laid down for commercial deployment in the 1980s and 90s,
replacing the older copper wires and communication satellites for long-distance transmission. The race for ever better performance continues and the capacity of a single fiber has been boosted by several orders of magnitude, from a few Gb/s in 1990 to hundreds of Tb/s today, so far more or less keeping up with society’s rapidly growing demands.
The tremendous progress in optical communications research is the fruit of the combined efforts of researchers from
diverse disciplines. The expertise needed to design a high-performance optical communication system ranges from physics to photonics and electronics, from communication and signal processing algorithms to network technologies. The purpose of this roadmap article is to survey the state-of-the-art in optical communications from multiple viewpoints, and envision where this rapidly evolving field might progress in the future. Due to the broad, interdisciplinary character of the research field, the article is a joint effort by many researchers, each one being a leading expert in a certain subfield of optical communications.Together we aim to provide a broad overview of optical communications as a whole.
The roadmap can be coarsely divided in four blocks, covering the optical communications field: hardware,
algorithms, networks and emerging technologies. After an initial historical overview, the first block will cover the optical hardware needed for high-speed, low-loss lightwave transmission. This block will consist of four sections, covering in turn optical fibers, optical amplification, spatial division multiplexing and coherent transceivers. Then to follow is the block on communication and signal processing algorithms, which will describe how to efficiently encode digital data onto lightwaves and to recover the information reliably at the receiver. The five sections in this block will cover, respectively, modulation formats, digital signal processing (DSP), optical signal processing, nonlinear channel modeling and mitigation and forward error correction (FEC). The third block will lift the perspective from point-to-point links to networks of many interconnected links, where the three sections cover the technologies needed in different kinds of networks: long-haul, access and data center networks. In the fourth and last block, finally, some emerging technologies will be described,which are currently undergoing intense research and may potentially provide disruptively different solutions to future optical communication systems. These technologies are optical integration and silicon photonics, optical wireless communication (OWC) and quantum communication (QC).
