RESEARCH

Here is a short description of the research activities in which we are currently involved or have been involved in the past, and of some research activities that we carry out in collaboration with other research groups at TECIP Institute.

Current research topics

• Optical fiber nonlinearity

The optical fiber channel is characterized by the presence of nonlinear effects, which have no parallel in other communication channels and raise many challenging (and still unsolved) theoretical and practical issues. In particular, we are currently working on:

• Channel modeling (perturbation methods, nonlinear Fourier transform, ...)
• Computation of system performance and capacity limits
• Nonlinearity mitigation
• High-capacity optical systems

The available bandwidth in a fiber-optic link is orders of magnitude wider than that available in other communication media. Nevertheless, this is barely sufficient to feed the insatiable appetite of the telecom market. A more efficient use of the available bandwidth is, therefore, highly desirable. With this goal in mind, we look for spectrally-efficient modulation formats that are specially suitable for the specific requirements of optical fiber systems, such as low complexity and resilience to propagation impairments. We are especially interested in the new paradigm of non-orthogonal signaling (and, in particular, in its specific form known as time-frequency packing) as compared to more traditional formats based on orthogonal signaling (e.g., Nyquist-WDM and OFDM)

Other research topics

• Polarization mode dispersion
• Optical equalization
• Impact and mitigation of laser phase noise (digital coherence enhancement)
• Multicanonical Monte Carlo simulation techniques
• Performance of optically-amplified direct-detection systems

Experiments

Whenever possible, we try to validate our theoretical results by means of transmission experiments, either in the lab or in the field, often in collaboration with the High-Capacity Optical Communications area.

Applications to optical networks

Our research, performed at a system level, often finds its natural application in the design and control of optical networks. In collaboration with the Networks and Services area, we investigate physical impairments in optical networks, efficient transmission techniques for flexible and elastic networks, and network defragmentation techniques.