Germanate glass core fiber GDF-SM-3.5/125-50


Higly Ge-doped silica fibers are used for variety of nonlinear applications.

Please see frequently asked questions below.


Article GDF-SM-3.5/125-50


Typical loss spectrum




High germania core fiber 


Core diameter, µm 4 x 3 (elliptical)
Clading diameter, µm 125 ± 1
Coating diameter, µm 260 ± 10
Delta n 0.074
GeO2 concentration, % 50
Cutoff wavelength, µm ~ 1.92
Attenuation  (at 1060nm), dB/km 23
Attenuation  (at 1300nm), dB/km 12
Attenuation  (at 1550nm), dB/km 6.7
Attenuation  (at 1850nm), dB/km ~ 7
Attenuation  (at 2100nm), dB/km 49

Germanate glass core fiber (Article GDF-SM-3.5/125-50)



Is there any explanation why the GDF-SM-3.5/125-50 has a 4 x3 µm elliptical core?

Viscosity of glass with very high germanium concentration is much lower compared with silica glass of the support tube. So, during the high temperature preparation of the preform in MCVD process the core tends to have some ellipticity. It takes place not in every preform (and hence in fiber) but often enough. 

Is it already a PM fiber? Does it splice well to standard PM fiber?

Mayby yes but we did not study its PM properties.  

Do you have any advice about the best way how to splice this fiber?

This fiber is spliced well with the standard fiber like SMF-28. Maybe you have to decrease the power and/or duration of the arc in the splicing machine as much as possible.



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