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Work Group Active Fiber Modules

Scientific Profile/R&D Activities

Active fiber optic modules based on special optical fibers with very different compositions and geometry are the key components of numerous photonic systems in laser material processing, communication and information technology, and – increasingly – spectroscopy. These fiber light sources comprise both fiber lasers and amplifiers and fiber-based nonlinear frequency conversion (e.g., supercontinuum production and stimulated Raman scattering). Several specific characterization methods are available to produce and qualify fiber optic components and modules, comprehensive modeling methods, and specially-adapted assembly and connection technology.

Research Topics

The focal point of research is the different effects for the creation and conversion of light in special optical fibers. Fiber light sources with novel characteristics are based on versatile and innovative fiber technologies (MCVD, powder sintering, gas-phase doping, melted glass) and fiber structuring methods; they are researched in close cooperation with other work groups in the fiber optics department. Emphasis includes:

  • Fundamental testing of long-term stability and loss mechanisms (photodarkening, etc.)
  • Method development for the characterization of preforms, special optical fibers (microstructured, double core, laser active) and fiber components
  • Design and simulation of innovative effects in compact fiber modules, in particular utilizing nonlinear optical effects in special optical fibers
  • Research and development of novel fiber light sources (e.g., flexibly tunable fiber lasers or fiber light sources for new spectral ranges)

Current Goals

  • Spectral research of the photodarkening effect in ytterbium-doped fibers in the wavelength range from 0.6 µm to 1.1 µm, as well as tests on photodarkening in thulium-doped fibers
  • Research of a tunable fiber laser (with a repetition rate-independent wavelength) with regard to tunable bandwidth and multi-wavelength operation
  • Pulse power scaling in REPUSIL-based fiber amplifiers up to approximately 1 MW at good beam quality (M2 ≈ 1.5)
  • Development of an online-capable method for the modal analysis of few-mode optical fibers and fiber lasers
  • Supercontinuum production in the visible and near infrared range with optimized microstructured nonlinear fibers


  • Fiber design and characterization: Numerical modeling, spectral attenuation and absorption, fluorescence testing (spectrum and lifetime), refractive index profile, stress and birefringence, mode analysis, dispersion measurement, etc.
  • Fiber processing: Tapering and splicing special optical fibers (up to 2.5 mm in diameter), fiber coupling, numerical modeling
  • Laser design and characterization: Numerical modeling, spectral emission, efficiency, pulse characterization, beam analysis, photodarkening

Application Fields Addressed

  • Spectroscopy in the life sciences and other areas
  • Laser material processing
  • Sensor technology and remote sensing
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