Scientific Profile

For several decades, the Leibniz-IPHT has combined research into materials and the development of technologies for the production of innovative optical glass fibers in a unique way in Europe. Great expertise and excellent infrastructural facilities in such diverse areas as material and preform production, fiber drawing, fiber functionalization, fiber and material characterization, as well as modeling and simulation were brought together 2021 in the Competence Center for Special Optical Fibers (CSF) to push new developments in the field of special glass fibers at Leibniz-IPHT and to further enhance efficiency.

For the development and manufacturing of innovative fiber concepts, the CSF is scientifically at the forefront and actively supports all research units of the Leibniz-IPHT as well as external partners from research and industry in joint R&D projects.

Preform development

Preforms are the base of optical glass fiber manufacturing. For preform production/manufacture our team of experienced technologists uses established processes as for example MCVD for the deposition of ultrapure fused silica and doping elements from gaseous or vaporable precursors (rare earth elements, aluminum, germanium, phosphorus, boron). At the same time alternative material and preform technologies are implemented to enable completely novel fiber structures and functionalities.

  • Chemical gasphase deposition (MCVD – solution and gasphase doping)
  • Powder based sintering and crucibel melting technology
  • Polishing of glass tubes inner surface using plasma torch
  • Fully equipped glassblower workshop as well as laboratory for optical quality grade mechanical manipulation of glass (cutting, grinding, polishing)
  • Glasmaker lathe i.a. for adaption of glass tubes and rods by collapsing, blowing up, stretching, compressing, overcladding, glazing
  • Gas pressure sintering system, isostatic presses and processing furnaces
  • Clean room facility – for staking of glass rods and capillaries made at Leibniz-IPHT to preforms for microstructured and multicore fibers

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Drawing technology for specialty fibers, rods and canes

Modern special optical fibers have complex, often filigree internal structures or combine extreme material combinations. The many years of experience of the specialists at the CSF at Leibniz IPHT is complemented by several individually optimized and adaptable fiber drawing lines and thus enables the realization of even the most complex fibers.

  • Wide range for setting geometric and kinematic parameters for drawing preforms into fibers, rods and canes; Preform rotation
  • Wide temperature range for drawing fused silica and other oxide, optical glasses
  • Various preform-based drawing processes, e.g. stack-and-draw, rod-in-tube, powder-in-tube drawing processes
  • High-precision pressure and vacuum control of structured preforms during the drawing process for defined manipulation of the target geometry
  • Application-specific fiber coating (up to triple coating) with different high and low refractive index coating materials through photochemical and / or thermal curing

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Fiber-Post-Processing und functionalization

Special optical glass fibers made at Leibniz-IPHT consist of very different glass and crystal materials and have unusual structures and geometries in order to perform special photonic tasks. At the CSF, diverse possibilities for the further functionalization of glass fibers are researched, developed and established as tailored system solution for industrial use.

Laser-based refractive index structuring for the generation of fiber Bragg gratings (FBG) or waveguide structures

  • Structuring wavelengths: 248 nm to 800 nm (ns and fs)
  • Structuring of fused silica, non-oxide glasses, crystals, ceramics
  • High grating wavelength flexibility continuously over the wavelength range from VIS to MIR by means of interferometric inscription processes
  • FBG length and position selection over a wide range
  • FBG reflectivity adjustable according to application requirements
  • Spectrally broadband FBGs, e.g. using chirped phase masks
  • FBG inscription during the fiber drawing process (drawing tower grating)


Fiber Post Processing

  • Preparation of fiber end faces (polishing of fiber end faces, cleaving of fibers, assembly of special fibers)
  • Manufacturing of fiber tapers: bi-directional and single-directional drawing processes using an arc or filament-based heat source
  • Design and manufacturing of adapted fiber optic components (splitter, combiner, mode field adapter)
  • Splicing of special fibers (including laser fibers, microstructured fibers, endcaps)
  • Recoating of individual sensor elements up to the entire fiber length
  • Post-processing laboratory (virtual tour)


Fiber optic sensor systems

  • Advice on and development of tailored fiber optic sensor systems based on fiber Bragg gratings up to industrial production readiness
  • Sapphire fiber Bragg grating based sensor concepts for high temperature diagnostics
  • Optimized evaluation routines for:
    • Temperature sensors (3K to 2000 ° C)
    • Strain sensors (0.0001% to 5%)
    • Fast measurement for vibration analysis (> 10kHz)

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Characterization methods

At CSF extensive characterization setups and many years of experience in the investigation of optical and structural properties of materials, preforms and glass fibers are available. This ensures close support and optimization of the manufacturing processes. In addition, research groups in the institute that are increasingly using optical fibers in their own research areas, as well as external partners from industry and research, are also supported.

  • Highly resolved determination of refractive index and stress curves in optical preforms as well as fibers
  • UV-VIS-NIR absorption measurements on compact glass samples
  • Light microscopy with image processing for geometrical analysis of fine structural elements in fibers
  • Optical characterization of simple as well as most complex glass fiber structures (attenuation, cut-off wavelength, bending losses, incl. sub-structures)
  • Temporally and spectrally resolved fluorescence measurements on volume and glass fiber samples
  • Measurement of tensile strength of fibers
  • Defect analysis using OTDR

As well as in close cooperation:

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Design and simulation of specialty optical fibers

Modern glass fibers are often supposed to show very specific innovative photonic properties. To do this, many optic and material parameters must be precisely calculated and balanced with one another. Our simulation experts use optimized scripts and routines based on commercial software such as MATLAB®, COMSOL Multiphysics®, ZEMAX®, Optiwave® but also specially developed program libraries.

  • Ray optical simulations (laser fibers, FBG inscription)
  • Wave optical properties in fibers (modal profiles of real refractive index profiles, micro structured and hollow core fibers)
  • Design and simulation of fiber optic modules in special optical fibers
  • Close cooperation with characterization enables refined measurement methods and interpretation of results

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Areas of application

Fibers made in Leibniz-IPHT are used in applications in medical technology, sensors, biophotonics, quantum optics, fiber lasers, information technology / telecommunications

  • Fiber laser and amplifiers (e.g. with Yb-, Er- or Tm-doping)
  • Temperature and strain measurement with fiber Bragg gratings (process and infrastructural monitoring)
  • Imaging (e.g. endospopy)
  • Spectroscopy (e.g. liquid and gas analysis)
  • Catheters in medical technology

Research Insights

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