News and Updates

MIO Continues - October 13, 2016

After two successful workshops in 2014 and 2015 and close to one hundred participant last year, the next edition of the Munich Workshop on Information Theory of Optical Fiber (MIO) will take place on December 5 and 6, 2016. You can find more details about MIO 2016 on the official website.

Paper Accepted in JLT - July 28, 2016

That was quick! Within just six weeks since the initial submission, our paper "On probabilistic shaping of quadrature amplitude modulation for the nonlinear fiber channel" has been accepted for publication in Journal of Lightwave Technology. You can find the full text here or under publications.

New Preprint Available - June 14, 2016

A new preprint entitled "On probabilistic shaping of quadrature amplitude modulation for the nonlinear fiber channel" is available on arxiv. The paper is joint work with Alex Alvarado and Georg Böcherer.

ECOC Papers Accepted - June 13, 2016

Time for some pleasant news. The ECOC notifications are out: all papers I had the pleasure to be involved in were accepted as oral presentations, including a joint work with Chalmers University of College were I was first author. You can find the paper titles and author lists under publications.

PTL Accepted - December 31, 2015

Over the summer, I did experiments on mismatched probabilistic shaping with experts from University College London. The paper that resulted from these experiments has now been accepted for publication in Photonics Technology Letters. You can find a preprint on arxiv.

OFC 2016 - December 14, 2015

Our paper on "Improved achievable information rates by optimized four-dimensional demappers in optical transmission experiments" was accepted to OFC 2016 as an oral presentation. The paper is joint work with Chalmers University of Technology and University College London. You can find a PDF version under publications.

MIO 2015 - November 4, 2015

The Institute for Communications Engineering is organizing a "Munich Workshop on Information Theory of Optical Fiber" (MIO), and I am a happy to be involved as a member of the local organizing committee. The main topics will be capacity of nonlinear channels, nonlinear Fourier transform, coded modulation, and signal processing in general. For more information, please visit the workshop web page.

Teaching Award - November 2, 2015

At the recent "day of the department" of electrical engineering at TUM, I was awarded the teaching award of the student association for my tutorials in Digital Transmission Technology. Many thanks to the students who nominated me and the jury who picked me as their winner! I'm very happy that my style of teaching seems to be well received with the students!

Web page online - October 21, 2015

Welcome to my personal web page! My last one was created in 1999 and taken offline around 2001; a new one is more than overdue. So much has changed in how web pages are created nowadays. It's not frames and tables any more, but div's and css all over the place. Interesting stuff and a lot for me to learn, but it will take me some time. I will add more content over the next days and weeks and also make everything look nicer.

Contact

Tobias Fehenberger

Dipl.-Ing. Tobias Fehenberger
Research and Teaching Assistant
Institute for Communications Engineering
Technical University of Munich (TUM)
Tel: +49-89-289-23477
Email: tobias.fehenberger@tum.de

About Me

Personal

The lovely city of Munich, Germany, is the place I've been calling "home" my entire life. Since Munich offers not only the mountains at our doorstep or the Oktoberfest but also a great technical university, I started studying electrical engineering and communication technology at TUM in 2005. From 2008 to 2010, I studied, lived and worked in Beirut, Lebanon, to get a first-hand experience of a different life style and culture. At some point in 2010, I decided to finish my Master and returned to Munich in mid 2010. After finishing all my courses, I had the opportunity to do the research for my master's thesis ("Diplomarbeit") with Prof. Polina Bayvel's Optical Networks Group at University College London (UCL), UK, and Prof. Norbert Hanik from TUM. I finished my thesis in December 2011 and Prof. Hanik became my Ph.D. supervisor just two months later. Since then, I've been enjoying working, teaching, and doing research at the Institute for Communications Engineering in the cite center of Munich.

Outside the academic world, I enjoy nature: hunting, hiking, and fishing.

My Research

Optical communication systems have become the backbone of the digital age. Virtually all IP-based traffic of Internet is transmitted over optical fibers, enabling high data rate services such as HD video streaming and cloud storage. The low loss of optical fibers over a huge spectrum of several THz and optical wideband amplifiers are key technologies that allow optical communication systems to transmit several trillion bits (Terabits) per second over thousands of kilometers of single-mode optical fiber with a core thinner than a human hair. Although these capacities seem huge, a steady demand for increased throughput has been observed for the past decades, with no end in sight. High-order modulation formats and advanced forward error correction schemes are potential options to achieve larger data rates. My research addresses these two entities jointly, a field known as coded modulation.

Google Scholar profile
ResearchGate profile

Education

  • 2005: Abitur (A-level or high school diploma equivalent), Karlsgymnasium München-Pasing
  • 2011: Dipl.-Ing. (M.Sc. equivalent) in Electrical Engineering and Communication Technology, TUM
  • Since 2012: Research and Teaching Assistant with Prof. Norbert Hanik (TUM)

Stipends and Distinctions

  • 2008: TUM future@home innovation prize
  • 2011: Scholar of the Heinrich und Lotte Mühlfenzl foundation to carry out my master's thesis in London
  • 2011: Erasmus exchange student at UCL
  • 2014: Prof. Dr. Ralf Kötter memorial award for my master's thesis [German newspaper article (PDF)]
  • 2015: Teaching award of the TUM electrical engineering student association ("Dozentenpreis der Fachschaft") [Image 1] [Image 2]

Teaching

Publications

2016

  • T. Fehenberger, A. Alvarado, G. Böcherer, and N. Hanik, "On probabilistic shaping of quadrature amplitude modulation for the nonlinear fiber channel," Journal of Lightwave Technology, vol. 34, no. 22, pp. 5064-5074, Nov. 2016. [PDF] [ DOI] [ arxiv]
  • T. Fehenberger, M. Mazur, T. A. Eriksson, M. Karlsson, and N. Hanik, "Experimental analysis of correlations in the nonlinear phase noise in optical fiber systems," accepted for presentation at the European Conference on Optical Communication (ECOC), Düsseldorf, Germany, Sep. 2016. [PDF]
  • T. A. Eriksson and T. Fehenberger, "Mutual information characterization of nonlinear fiber channels [invited]," accepted for presentation at the European Conference on Optical Communication (ECOC), Düsseldorf, Germany, Sep. 2016.
  • A. Alvarado, L. Szczecinski, T. Fehenberger, M. Paskov, and P. Bayvel, "Improved soft-decision forward error correction via post-processing of mismatched log-likelihood ratios," accepted for presentation at the European Conference on Optical Communication (ECOC), Düsseldorf, Germany, Sep. 2016.
  • R. Maher, D. Lavery, G. Liga, M. Paskov, A. Alvarado, T. Fehenberger, and P. Bayvel, "Capacity approaching transmission using probabilistic shaping and DBP for PFE constrained submarine optical links," accepted for presentation at the European Conference on Optical Communication (ECOC), Düsseldorf, Germany, Sep. 2016.
  • M. P. Yankov, F. Da Ros, E. P. da Silva, T. Fehenberger, L. Barletta, D. Zibar, L. K. Oxenløwe, M. Galili, and S. Forchhammer, "Experimental study of nonlinear phase noise and its impact on WDM systems with DP-256QAM," accepted for presentation at the European Conference on Optical Communication (ECOC), Düsseldorf, Germany, Sep. 2016.
  • T. A. Eriksson, A. Lorences-Riesgo, P. Johannisson, T. Fehenberger, P. A. Andrekson, and M. Karlsson, "Achievable rates comparison for phase-conjugated twin-waves and PM-QPSK," Proc. Optoelectronics and Communications Conference (OECC), Niigata, Japan, Jul. 2016.
  • T. Fehenberger and N. Hanik, "Multi-dimensional demappers for optical fiber systems with soft-decision forward error correction [invited]," Proc. International Conference on Transparent Optical Networks (ICTON), Trento, Italy, Jul. 2016. [PDF] [ DOI]
  • T. A. Eriksson, T. Fehenberger, P. A. Andrekson, M. Karlsson, N. Hanik, and E. Agrell, "Impact of 4D channel distribution on the achievable rates in coherent optical communication experiments," Journal of Lightwave Technology, vol. 34, no. 9, pp. 2256-2266, May 2016. [ DOI] [ arxiv]
  • T. Fehenberger, T. A. Eriksson, A. Alvarado, M. Karlsson, E. Agrell, and N. Hanik, "Improved achievable information rates by optimized four-dimensional demappers in optical transmission experiments," Proc. Optical Fiber Communication Conference (OFC), Anaheim, CA, USA, March 2016. [PDF]
  • T. Fehenberger, D. Lavery, R. Maher, A. Alvarado, P. Bayvel, and N. Hanik, "Sensitivity gains by mismatched probabilistic shaping for optical communication systems," Photonics Technology Letters, vol. 28, no. 7, pp. 786-789, Apr. 2016. [PDF] [ DOI] [ arxiv]

2015

  • M. P. Yankov, T. Fehenberger, L. Barletta, and N. Hanik, "Low-complexity tracking of laser and nonlinear phase noise in WDM optical fiber systems," Journal of Lightwave Technology, vol. 33, no. 23, pp. 4975-4975, Dec. 2015. [ DOI]
  • T. Fehenberger, M. P. Yankov, L. Barletta, and N. Hanik, "Compensation of XPM interference by blind tracking of the nonlinear phase in WDM systems with QAM input," Proc. European Conference on Optical Communication (ECOC), Valencia, Spain, Sep. 2015. [PDF] [ DOI]
  • T. A. Eriksson, T. Fehenberger, N. Hanik, P. A. Andrekson, M. Karlsson, and Erik Agrell, "Four-dimensional estimates of mutual information in coherent optical communication experiments," Proc. European Conference on Optical Communication (ECOC), Valencia, Spain, Sep. 2015. [PDF] [ DOI]
  • T. Fehenberger, T. A. Eriksson, P. Johannisson, M. Karlsson, and N. Hanik, "On the impact of carrier phase estimation on phase correlations in coherent fiber transmission," Proc. Tyrrhenian International Workshop on Digital Communications (TIWDC), Florence, Italy, Sep. 2015. [PDF] [ DOI]
  • T. Fehenberger and N. Hanik, "Analysis of forward error correction and achievable rates for optical fiber systems [invited]," Proc. International Conference on Transparent Optical Networks (ICTON), Budapest, Hungary, Jul. 2015. [PDF] [ DOI]
  • T. Fehenberger, A. Alvarado, P. Bayvel, and N. Hanik, "On achievable rates for long-haul fiber-optic communications," Optics Express, vol. 23, no. 7, pp. 9183-9191, Apr. 2015. [PDF] [ DOI]
  • T. Fehenberger, G. Böcherer, A. Alvarado, and N. Hanik, "LDPC coded modulation with probabilistic shaping for optical fiber systems," Proc. Optical Fiber Communication Conference (OFC), Los Angeles, CA, USA, Mar. 2015. [PDF] [ DOI]

2014

  • T. Fehenberger and N. Hanik, "Digital Back-Propagation of a Superchannel: Achievable Rates and Adaption of the GN Model," Proc. European Conference on Optical Communication (ECOC), Cannes, France, Sep. 2014. [PDF] [ DOI]
  • T. Fehenberger and N. Hanik, "Estimates of Constrained Coded Modulation Capacity for Optical Networks," Proc. 15. ITG Fachtagung Photonische Netze, Leipzig, Germany, May 2014. [PDF] [ http://ieeexplore.ieee.org/xpl/articleDetails.jsp?&arnumber=6839977]

2013

  • T. Fehenberger and N. Hanik, "Information quality (IQ) factor as soft-decision decoding threshold for optical communications," Proc. European Conference on Optical Communication (ECOC), London, UK, Sep. 2013. [PDF] [ DOI]
  • T. Fehenberger and N. Hanik, "Comparison of performance limits by mutual information and practical realizations for optical long-haul coded modulation communication systems [invited]," Proc. International Conference on Transparent Optical Networks (ICTON), Cartagena, Spain, Jun. 2013. [PDF] [ DOI]

2012

  • S. Kilmurray, T. Fehenberger, P. Bayvel, and R. Killey, "Nonlinear transmission performance of reduced guard interval OFDM and quasi-Nyquist WDM," Proc. Signal Processing in Photonic Communications (SPPCom), paper SpTu1A.3, Colorado Springs, CO, USA, Jun. 2012. [ DOI]
  • S. Kilmurray, T. Fehenberger, P. Bayvel, and R. Killey, "Comparison of the nonlinear transmission performance of quasi-Nyquist WDM and reduced guard interval OFDM," Optics Express, vol. 20, no. 4, pp. 4198-4205, Feb. 2012. [ DOI]

Source Code

In this section, you find some Matlab™ source code that I found useful for my research. If you find an error or have a question, please let me know via email.

Achievable Rates: MI and GMI

Calculate Mutual Information (MI): calcMI_MC.m (Sep 10, 2015)
Calculate Generalized Mutual Information (GMI): calcGMI.m (May 29, 2015)

When to use (symbolwise) MI and when to use GMI

For a given input and a memoryless channel, the MI is the largest achievable rate. If you do not want to make restrictions on the receiver and its decoder, use MI. If you consider a receiver with binary decoding and iterations between demapper and decoder are not allowed, GMI is an achievable rate (MI is in general not!).

Gaussian Noise (GN) Model

Calculate (O)SNR according to the GN model: calcOSNR_GNmodel.m (April 28, 2015)