Technological aspects of manufacturing silica optical fibers with large central defect of graded refractive index profile for fiber optic sensors based on few-mode effects

• Published in: Nauchno-tekhnicheskiĭ vestnik informat͡s︡ionnykh tekhnologiĭ, mekhaniki i optiki mekhaniki i optiki, 2017-04, Vol.17 (2), p.224-233
• Main Authors: Demidov, V.V., Ter-Nersesyants, E.V., Bourdine, A.V., Burdin, V.A., Minaeva, A.Yu, Khokhlov, A.V., Komarov, A.V., Ustinov, S.V., Dukelskii, K.V.
• Format: Article
• Language: English
• Subjects: attenuation coefficient; chemical vapor deposition; few-mode effects; graded-index multimode fiber; graded-index profile; mechanical strength; microbending; optical fiber drawing; refractive index profile defect; silica optical fiber
• ISSN: 2226-1494; 2500-0373
• DOI: 10.17586/2226-1494-2017-17-2-224-233

The paper deals with results of the study on the main technological aspects relating to a full production cycle of silica multimode graded-index fibers with the refractive index profile having central defect in the form of a large dip. Preform synthesis conditions for implementation of the mentioned defect via MCVD method have been analyzed and optimized. We have carried out research of the effect of geometrical irregularities, induced by drawing optical fibers under the manual control of the outer diameter stability, on attenuation coefficient of the graded-index 50/125 μm optical fibers with a large dip in the center of the refractive index profile. It is shown that variations of the outer diameter within the limits ± 3.5 μm lead to an increase of attenuation by 2–5 dB/km at the wavelength λ = 1310 μm as compared to the optical fibers fabricated under the automatic maintenance of the outer diameter stability. It has been determined that in the latter case fibers with the parabolic refractive index profile, corresponding to numerical aperture of 0.20, and the dip depth equal to 0.0115 demonstrate the attenuation about 5 dB/km in the second and third optical fiber transmission windows. Applying the Weibull distribution, a statistical evaluation of mechanical properties of the optical fibers drawn at various temperatures has been carried out. Based upon measurements, tensile strength of the fibers was estimated to be 5.07–5.49 GPa, that is comparable with the strength properties of silica telecom fibers. The manufactured multimode fibers are attractive candidates for developing sensing elements of registering external influences in systems of fiber-optic sensor networks based on few-mode effects.