Algorithm Design and Engineering

Digital signal processing (DSP) in the electrical domain is an enabling technology for coherent optical transport systems. It is employed for carrier recovery and mitigation of linear as well as nonlinear impairments in digital coherent receivers. In future flexible networks, efficient DSP will be a key element of software-defined transponders.

The Digital Signal Processing Group has wide experience in the development and real-time implementation of DSP algorithms for coherent optical systems. Expertise ranging from offline processing to VHDL and FPGA-based implementation is regularly demonstrated in laboratory experiments and field-tests.

Research in the area of DSP for coherent optical systems at the Submarine & Core Systems Group focuses on the following aspects:

- Development of algorithms for

  • Blind and data-aided carrier recovery for advanced modulation formats
  • Blind and data-aided channel estimation
  • Linear and nonlinear impairment mitigation
  • Linearization of electrical and optical components

- DSP-based performance monitoring and component characterization
- Real-time implementation

Software-defined transponder

DAC: digital-to-analog converter
ADC: analog-to-digital converter
DP-I/Q MOD: dual-polarization inphase and quadrature modulator

DSP algorithms for impairment mitigation and equalization of advanced modulation formats

1.8 Tb/s PDM-16QAM transmission experiment

Publications

Experimental Investigation of 126-Gb/s 6PolSK-QPSK Signals
J. K. Fischer, S. Alreesh, T. Tanimura, R. Elschner, F. Frey, C. Meuer, L. Molle, C. Schmidt-Langhorst, and C. Schubert
Optics Express, vol. 20, no. 26, pp. B232-B237, December 2012

Experimental Demonstration of a Format-Flexible Single Carrier Coherent Receiver using Data-Aided Digital Signal Processing
R. Elschner, F. Frey, C. Meuer, J.K. Fischer, S. Alreesh, C. Schmidt-Langhorst, L. Molle, T. Tanimura, C. Schubert
Optics Express, vol. 20, no. 27, pp. 28786-28791, Dec. 2012

Bandwidth-variable transceivers based on 4D modulation formats for future flexible networks
J. K. Fischer, S. Alreesh, R. Elschner, F. Frey, M. Nölle, C. Schubert
Proc. 39th European Conference on Optical Communication (ECOC), September 22-26, September 2013, London (United Kingdom), paper Tu.3.C.1 (invited)