Influence of Two-Frequency Radiation Intensity Fluctuations on the Output Signal of a Vortex Optical Fiber Forming OAM Address in Polyharmonic Sensor Technology

Abstract

A schematic diagram of a RoF radio-optic system with vortex signals is presented, in which the radio frequency is determined by the difference between the wavelengths of two lasers. It is assumed that the generation of a vortex signal can be performed through a vortex fiber-optic periodic structure, which can be obtained using a technology similar to the manufacture of long-period fiber Bragg gratings. The parameters of the grating are modeled assuming that the fundamental light-guide mode (LP01) is applied to the specified vortex element, and the higher-order mode (LP11) is reflected. It was found that the distortion of the vortex signal can be reduced by introducing apodization and chirping of this periodic structure. The following optimal parameters have been estimated: the apodization and chirp multiplier functions, at which the distortions of the amplitude and phase of the vortex signal, as well as the appearance of an unwanted angle distortion, will be minimal. It is shown that such gratings can be exploited in addressed sensors systems using the orbital angular momentum (OAM) of a lightwave as a unique sensor address.

A Nonlinear Radio-photon Conversion Device

“…Having analyzed the published works in the area under consideration [5][6][7][8], our scientific team has also performed an experimental study of this principle of generation using a periodically poled lithium niobate crystal -PPLN [3,4] and based on the model presented in [1], fig. 1.…”

“…In equations (11) and (12) we use the following designations:  11 ,  22 ,  33 ,  12 ,  13 ,  21 ,  23 ,  13 and  32 are the overlap integrals between the corresponding waves ( iv  for each pair of i th and v th modes), while we assume that  =  0,1 , where  0,i , are determined for the corresponding frequencies ωi and unperturbed values n0,i at these frequencies. The factor exp( ) j in (11) is determined by the difference of the topological charges (an integer) ℓi of the vortex beams for each of the waves and represents the projection of the orbital angular momentum (OAM) on the direction of propagation [1][2][3][4]; it is determined by the dependence of the electromagnetic field of the vortex beam on the azimuthal angle φ. If the waves have no OAM, then the specified multiplier is not taken into account, i.e.…”

“…Such tasks require both the use of new modulation formats and new physical layer technologies, which ensure, in particular, the "seamlessness" (absence of intermediate operations) of optical-radio conversion which is especially relevant in sub THz, THz systems where it is very difficult to generate high-frequency radio signals by electronic devices, and it also seems inefficient to decode a multichannel signal for subsequent conversion of its components [1][2][3][4]. Therefore, to ensure such seamlessness, in particular, for opticalradio conversion in two-frequency (or wavelengths λ: λ1, λ2) radio over fiber (RoF) networks transmitting vortex signals (carrying orbital angular momentum, OAM), a nonlinear converter was developed [1].…”

On the problem of forming a 3D refractive index profile in a fiber and compatible components and possible solutions

“…Figure 1. Illustration of a 3D profile of the refractive index of a light guide helical Bragg grating 1,2 .…”

A Nonlinear Radio-Photon Conversion Device

“…These channel requirements imply both the use of new modulation formats and physical layer technologies, which ensure, in particular, the "seamlessness" (absence of intermediate operations) of optical-radio conversion, which is especially relevant in sub-THz and THz systems, where it is very difficult to generate high-frequency radio signals by electronic devices, and it also seems inefficient to decode a multichannel signal for subsequent conversion of its components [2][3][4][5]. Therefore, to ensure such seamlessness, in particular, for optical-radio conversion in two-frequency (or wavelengths λ: λ 1 , λ 2 ) radio over fiber (RoF) networks transmitting vortex signals (carrying orbital angular momentum, OAM), a nonlinear converter was developed [2].…”