A. S. Belanov

Single-mode fibers with an additional ring lightguide for two-channel data transmission

For the first time, two-channel concentric-core optical fibers consisting of a broadband central single-mode lightguide for the wavelength of 1.3 micrometers and a ring multimode lightguide, 10 micrometers in thickness, have been developed. The outer fiber diameter is 125 micrometers . The fibers are meant for two-channel communication systems. Optical losses of less than 1 dB/km for the both cores have been achieved, the channel-to-channel crosstalk being less than -40 dB. A dependence of optical losses in the ring lightguide on the radius of curvature and strain of a coiled fiber has been revealed. The optimal refractive index profile of the ring core has been found to minimize optical losses in coiled and straightened fibers. A fiber-optic communication link, 12 km in length, has been constructed, and the loss distribution along the link has been investigated using the OTDR-technique. It is shown that there is no distributed coupling between the two cores and the channels remain independent even at large distances.

Reduction of dipersion in three-layer fiber waveguides

An analysis is made of some of the methods for reducing disperison in three-layer optical fiber waveguides with a step-like distribution of the refractive index. In particular, a calculation is made of the fiber parameters which ensure that the four lowest modes have the same group velocities. The results are given of a calculation of the material and waveguide dispersions in one-mode two- and three-layer waveguides. It is shown that the material and waveguide dispersions can be mutually compensated in a wide range of wavelengths (λ = 0.6 – 2.5 μ) and normalized waveguide frequencies (V = 1–6).