V. V. Voloshin

Effect of metal coating on the optical losses in heated optical fibers

The effect of heating in air on the optical losses in metal-coated fibers has been studied. Two fibers were drawn from the same silica preform and coated by different metals (copper and aluminum). Dependences of a change in the optical losses on the temperature were measured in a 20–400°C range at a 50°C step. The optical losses of metal-coated fibers heated to temperatures below 300°C change mostly due to the microbending contribution. At temperatures above 300°C, the main contribution to increasing optical losses is due to the absorption on OH groups. It is established for the first time that the contribution to optical losses due to the OH groups is much more pronounced in Al-coated fibers than in Cu-coated ones. In addition, the Al-coated fibers exhibit growth in the optical losses above 300°C due the absorption on molecular hydrogen.

Optical fiber with distributed Bragg-type reflector

Optical fiber (OF) with a relatively high level of the backward signal at a certain wavelength is developed and studied. An increase in the backward signal is reached due to the recording of multiple weak fiber Bragg gratings (FBGs) in the course of fiber pulling. A scheme that is simpler than the direct FBG recording through a phase mask is proposed and implemented. Fibers with FBG recorded with different ratios of the region with recorded gratings to the total length of OF are fabricated. An increase in the level of the backward signal relative to the level of the Rayleigh scattering by more than 30 dB is reached. Results of experimental study of the proposed OFs and examples of practical application are presented.

Absorption Loss at High Temperatures in Aluminum- and Copper-coated Optical Fibers

Thermally induced variations in the optical loss of optical fibers with metal (copper and aluminum) coatings are studied. It is demonstrated that an increase in the loss related to the OH groups depends on the medium in which the annealing takes place (an increase in the loss related to the OH groups in argon is greater than the increase in air) and on the dopant (an increase in the loss in the core doped with GeO2 + P2O5 is greater than the increase in GeO2).

Radiation resistant optical fiber with a high birefringence

A radiation resistant optical fiber with a high birefringence is fabricated on the basis of nitrogen-doped silica glass using the PANDA technology and studied. The loss in this fiber for an absorbed @[gamma]-radiation dose of 2–10 kGy does not exceed 5–10 dB/km, which is an order of magnitude lower than that of standard telecommunication fibers with a germanium silicate core.

N-doped-silica-core polarization maintaining fibre for gyros and other sensors for application in space industry

PANDA-type optical fibre with nitrogen-doped silica as core and pure silica as cladding material is fabricated and tested. The fibre demonstrates birefringence as high as 5·10-4, polarization holding h-parameter 2·10-5 m-1, loss 1.5 dB/km at a wavelength of 1.56 microns and 250 dB/km at 0.4 microns. Gamma radiation induced loss is found not exceeding 5-10 dB/km at a dose of 2-10 kGy, which is by an order of magnitude lower as compared to similar fibre with Ge-doped silica in the core.

Simulation of the properties of microstructured optical fibers

A new method for calculating the radiation loss and chromatic dispersion of leaky modes propagating in microstructured (holey) optical fibers (MOFs) with circular air-filled channels is proposed and implemented numerically. It is shown that the results are in good agreement with both the known numerical data and with the experimental data obtained for two types of fabricated MOFs that contain, respectively, 30 and 60 channels.