Education of the republic of uzbekistan tashkent state technical university named after islam karimov

Keywords:
 fiber light guide, polarization, ellipticity angle, external load, reflectometric sensors 
Introduction 
 
Optical fiber is very often used in medicine in the field of diagnostics. Since optical fibers 
are very thin, they can be twisted into flexible filaments, and can be used in studies of blood 
vessels, lungs and other human organs. Fiber-optic research is extremely necessary in the field 
of medicine. The field of application of optical fibers in medical practice and research 
continues to grow rapidly every day [1]. 
Fiber Bragg grating (VBR) is one of the most frequently used elements for the 
development of smart textiles for medical purposes (VBR placed in a textile bandage), due to 
its good sensitivity to deformation. This characteristic makes it possible to develop a variety of 
configurations, both point-based and sequentially and in parallel distributed, based on 
measuring the magnitude of compression/stretching strain of the VBR when monitoring 
respiration, when monitoring heart rate or pulse[2]. 
The results of studies of low-mode optical optical fibers with the preservation of 
polarization quite convincingly indicate the high sensitivity of the low-mode mode of operation 
of the optical fiber to anisotropic external influences, compared with the single-mode mode of 
operation of the same fiber. This result is of great practical value in the development and 
manufacture of highly sensitive fiber-optic sensors of various physical quantities. 
The results obtained and their discussion 
 
We have conducted studies of the parameters of fiber optical fibers with the preservation of 
polarization under external influence. Figure 1 shows the characteristic dependence of the 
phase shift δ or the ellipticity angle ψ on the load value F for uniaxial transverse deformation of 
a fiber fiber with a length of l = 32 mm. It can be seen that these dependencies fit into a linear 
dependence within the experimental error (~1%), however, there is a rather significant 
difference in the experimental data obtained for different sections of the fiber. This difference 
is due to the fact that different sections of the fiber are subjected to deformation, in which the 
elliptical core is oriented differently relative to the direction of uniaxial-transverse deformation, 

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