Fiber Dopants

LASER COMPONENTS offers fiber designs with various dopants – for example, germanium fibers that are insensitive to bending, erbium/ytterbium-doped double clad fibers, and erbium-doped fibers with different absorption and cut-off wavelengths. Each of these designs has specific advantages required in clearly defined applications.

Strongly Germanium-Doped Fibers

The cores of these fibers contain five times more germanium than commercial telecom fibers. Therefore, they can be inscribed with FBGs without being enriched with hydrogen. Such optical fibers have a high numerical aperture and thus low bending losses. Therefore, they are used in particular for the production of FBG arrays that are insensitive to bending. The versions with low cladding diameters of 50 µm or 80 µm can be wound particularly tightly. Due to their long service life, strong germanium dopants are used, for example, in optical hydrophones and geophones.

Upon request, we can also provide you with special coating types which do not have to be removed if the fibers are inscribed with FBGs.

Double-Clad Fibers with Erbium/Ytterbium Doping

Erbium/ytterbium-doped double-clad fibers were designed as amplifying fibers to make high-power communication possible. They consist of an erbium, ytterbium, and phosphorus-doped core surrounded by a fused silica cladding. This design directs the pump light. The result is a bundled and pumped beam of light. The boundary for the pump light is formed by a second, fluorinated silica cladding. Thus, the entire fiber consists of silicon dioxide. Polymers with low refractive indices are not used. This makes the fiber particularly resistant. They function at any temperature and ambient humidity. In addition, double-clad fibers do not need to be recoated after stripping, cleaving, or splicing.

Erbium-Doped IsoGain Fibers

Fibercore manufactures erbium-doped fibers with numerous absorption and cut-off wavelengths under the brand name IsoGain. These values are crucial for the performance of erbium-doped fiber amplifiers – so-called EDFAs. For example, C-band EDFAs require fibers with low absorption values. In contrast, high absorption values are required for the L-band. Large core diameters and high cut-off wavelengths are used to achieve high pumping power and non-linear effects.

All IsoGain fibers are surrounded by a double acrylate layer. The design of their cores is designed to produce a strongly flattened wavelength range.

Polarization-Maintaining Erbium-Doped Fibers

Fibercore combines the bow-tie geometry of highly birefringent PM fibers with the core design of IsoGain fibers for PM fibers with erbium doping. This type of fiber has been developed with mode-coupled fiber lasers in mind and is suitable for all products in which polarization must be maintained. It has a high peak absorption value as required for erbium-doped fiber amplifiers (EDFAs) with short amplification lengths.

Other Doped Fibers

Depending on the application, doping with neodymium, erbium, or ytterbium is used for laser and telecommunications applications with wavelengths between 1030 nm and 1550 nm.

• DF1000: The advantage of these neodymium-doped fibers is their low laser threshold. Thus, low-cost laser diodes such as those used in CD players are also suitable as a light source. They are the ideal introduction to fiber laser technology.
• DF1100: This strongly ytterbium-doped SM fiber is the best solution for the pumping of lasers with wavelengths between 915 nm and 980 nm. Its high absorption rate makes it the ideal solution for preamplifiers or short amplification lengths in mode-locked light ring lasers in the femtosecond range.
• DF1500Y: Through a mixture of erbium and ytterbium, the pump absorption band of this fiber is extended from 915 nm to 980 nm. Up to a peak value of 980 nm, the absorption rate is relatively low. This also makes it possible to use inexpensive, non-stabilized 940 nm pumps. The output power is less susceptible to temperature-dependent fluctuations in the pump wavelength.

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