A pinboard by
Aazar Saadaat Kashi

PhD Student, Queen's University


digital signal processing for transmitters and receivers in coherent optical fiber transmission

According to Cisco VNI global IP traffic forecast, global IP traffic will increase nearly threefold over the next five years, and will have increased 127-fold from 2005 to 2021. Fulfilling the traffic requirements involves increasing both the capacity and achievable transmission distance in optical communication systems. These requirements also imply the need to be able to allocate the capacity intelligently based on the traffic demands, distance, and user requirements. As a consequence of increase in bit rate to meet the traffic demands, systems performance becomes less tolerant to fiber impairments such as fiber nonlinearities. Thus, mitigating the transmission impairments is essential to achieve high capacity transmission, since the capacity is ultimately limited by nonlinear effects. Through this evolution of optical networks towards higher capacity, it is inevitable to be able to continuously monitor various performance parameters. Real-time performance monitoring, particularly regarding to the signal quality measured in terms of signal-to-noise ratio, or estimation of various channel impairments across the network is called optical performance monitoring (OPM). Simplicity in implementation of the OPM technique and the demand for the low cost and the ability to monitor multi-impairment while accommodate different system types, are the key features for the OPM techniques. Among all impairments, fiber Kerr nonlinearities are major impairments since the capacity is ultimately limited by nonlinear effects. OPM techniques can be employed in order to quantify the amount of distortions introduces and possibly compensating these impairments. This research will provide the following contributions to the field of fiber-optic communication: 1. a fundamental understanding of the characteristics of the OPM techniques; 2. the application of these techniques to improve the system performance by compensating the nonlinear effects in network; and 3. a step forward in flexible networks by devising the new techniques to monitor the system in real-time and fulfill the requirements of the system based on the traffic demands, distance, and user requirements. My research in this area has already shown great promise, thus, I am excited to develop this leading edge research from the idea stage to quantified performance. The resulting insights for my PhD research can benefit the application of flexible optical transceivers as a key subsystem for future optical networks.