Fiber-optic parametric amplifiers for signal regeneration in transmission systems with advanced modulation formats

• Applicants: Professor Dr.-Ing. Hans-Joachim Grallert; Professor Klaus Petermann, Ph.D.
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2010 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 175696353

The presently running project is devoted to the investigation of fiber-optic parametric amplifiers (FOPA) for low-noise phase-insensitive and phase-sensitive amplification in transmission systems. The project particularly focuses on the application of FOPAs in transmission system with high spectral efficiency which is achieved by means of advanced modulation formats. In addition to data signal amplification, it was begun to investigate basic signal processing functionalities, i.e. wavelength conversion, phase conjugation (mid-span spectral inversion) and regeneration.Up to now, regeneration was shown for a single wavelength channel with binary phase-shift keying (BPSK) in a black-box phase-sensitive FOPA. Such a black box setup consists of a phase-insensitive stage, in which a second phase locked pump wave is generated by mixing the signal with a first pump wave. Subsequently, regeneration takes place in the second phase sensitive stage. The drawback of this scheme is given by the fact that it is not format transparent, since different harmonics need to be generated in the first stage for different modulation formats. Moreover, it is difficult to implement multi-wavelength regeneration with this scheme.As significant extension of the tasks of the presently running project, parallel regeneration of nonlinear phase distortions of several wavelength channels will be investigated based on a format transparent scheme for advanced modulation formats such as 16-QAM in the framework of the project extension. This scheme is based on generation of phase conjugated copies at the transmitter and parallel transmission along the fiber link. Phase-sensitive FOPAs are used as inline amplifiers and provide phase regeneration.It is targeted to increase the nonlinear threshold of the fiber link and -if possible- also an enhanced spectral efficiency length product despite the fact that the spectral efficiency is reduced by a factor of two due to the transmission of the signals and their phase conjugated copies as well.Further tasks are motivated by the results of the presently running project to minimize the nonlinear distortions of the FOPA itself using an optimized design of the parametric amplifier with optical phase conjugation as well as to realize a polarization insensitive phase-sensitive FOPA.The project work will be continued by both research groups at TU Berlin to carry out the experimental work (Prof. Dr. Grallert) as well as the theoretical and simulative investigation (Prof. Dr. Petermann). In combination with the close collaboration with the Fraunhofer Heinrich-Hertz Institute unique studies on the implementation of FOPAs in optical transmission systems with advanced modulation formats such as 16-QAM are enabled.

• DFG Programme: Research Grants