Fiber fabric as an element of signal systems

Abstract

The article presents research materials for developing fiber-optic sensors that can be integrated into items of clothing or combat equipment of servicemen. The geometric, mechanical and functional characteristics of the sensors can be varied depending on the purpose of the signal element, which allows their integration into textile materials, which are the basis for the manufacture of military equipment. Replacement of areas of textile fabric in places where it covers the optical sensor with fabric elements made of optical fibers has a multifunctional purpose. First, due to its tissue structure, it expands the probing light beam from a spot (with a spatial dimension of 0D) into a 2D scan, thereby improving the spatial sensitivity diagram of the sensor. Second, it replaces the removed tissue on top of the sensor, thereby restoring the integrity of the tissue. Third, it performs a protective and masking function for the sensor. In terms of strength, elasticity and durability, such fabric materials are almost indistinguishable from traditional ones. The paper experimentally demonstrates that the system of quasi-parallel fibers, which can be part of the fabric elements of clothing or equipment of a serviceman, plays the role of a diffraction grating for a laser beam. The shape of the diffraction band strongly depends on the angle of incidence of the light beam relative to the normal to the grating. The shape of the diffraction band is linear if the incident ray is in a plane perpendicular to the plane of the system of quasi-parallel optical fibers and at the same time perpendicular to the direction of the fibers. If the incident ray is outside this plane, then in the general case, the shape of the diffraction band is described by a second-order curve. The effect of curvature of the diffraction band when the laser beam falls obliquely on the lattice is a consequence of the so-called conical diffraction of light, in which the diffracted rays propagate along the surface of the cone. In particular, if the incident ray is in a plane perpendicular to the plane of the fiber system (grating) and parallel to the direction of the fibers, then depending on the angle between the incident ray and perpendicular to the grating plane, the diffraction band is a hyperbola at angles of incidence smaller than 45o, parabola, when the angle of incidence is 45o or ellipse at angles of incidence larger than 45o. The case of small angles of incidence when the diffraction band is a hyperbola is demonstrated in the work. The property of changing the type of the second-order curve (hyperbola / parabola / ellipse) of the diffraction band and its orientation (curved to the right / left or up / down) when changing the angle of incidence of the light beam on the grating can be used to determine the position of the light source (laser sniper sight) with respect to the fiber optic grating integrated into the item of clothing or equipment of the serviceman.