Six-Core GeO2-Doped Silica Microstructured Optical Fiber with Induced Chirality

Abstract

This work presents a fabricated silica few-mode microstructured optical fiber (MOF) with a special six GeO2-doped core geometry, an outer diameter of 125 µm (that corresponds to conventional commercially available telecommunication optical fibers), and improved induced twisting up to 500 revolutions per 1 m (under a rotation speed of 1000 revolutions per meter with a drawing speed of ~2 m per minute). The article discusses some technological aspects and issues of manufacturing the above-described twisted MOFs with complicated structures and geometry as GeO2-doped silica supporting elements for them. We present results of some measurements performed for fabricated samples of chiral silica six-GeO2-doped-core few-mode MOFs with various orders of twisting and both step and graded refractive indexes of “cores”. These tests contain research on MOF geometrical parameters, attenuation, and measurements of the far-field laser beam profile.

Twisted Silica Few-Mode Hollow GeO2-Doped Ring-Core Microstructured Optical Fiber

“…In previously published papers [84][85][86][87][88][89][90], we described in detail all previous successfully performed stages of drawing the tower modifications that provide improvements to the twisting of the fabricated MOF from the initial weak 10 revolutions per meter (rpm) up to 66 rpm [84,85], and then further 100, 400, and 500 rpm [89,90]. We chose to develop the method proposed in [1]: the rotation of the optical fiber preformed during the drawing process.…”

“…At the same time, we tested, verified, and determined the full-cycle technique of the twisted MOF fabrication: from the MOF stack formation, it was redrawn to the MOF cane and then followed the MOF drawing from the cane with twisting under specified excess pressure and at a specified drawing temperature [84,85]. During this stage, we successfully fabricated the following MOFs with twisting from 10 rpm (with a rotation speed of 20 revolutions per minute with an MOF drawing speed of 2 m per minute) up to 66 rpm (with a rotation speed of 200 rpm and an MOF drawing speed of 3 m per minute): hexagonal geometry with shifted core [84,85]; hexagonal geometry, that provides the quasi-ring radial mode field distribution [84,85]; equiangular spiral six-ray geometry [89,90]. Furthermore, by combining the maximal rotor rotation speed of 200 revolutions per minute and a low drawing speed of 0.9 m per minute, the typical hexagonal geometry MOF with a shifted core under the pitch of 0.65…0.700 and 3…4 spatially guided modes were manufactured with twisting of 217 rpm, which was ultimately the maximum chirality order for equipment described above that could be possibly induced.…”

“…Therefore, to improve the MOF chirality, during the next stage, we replaced the stepper engine by a new commutator motor with a maximal rotation speed of 2000 revolutions per minute, and carried out a series of engineering and research and technological works on a second set of drawing tower modifications [89,90]. In addition to the design, fabrication, and installation of a new carrier for motor fixing on the feed unit chuck, a new drive belt with an improved length due to the increasing distance between the commutator motor shaft and feed unit chuck, a new special supporting pad with the fixed commutator motor, protective shroud, and driving system in the drawing tower feed unit, outside control panel, connected to power supply and driver for the commutator motor, we proposed and manufactured a special device for the additional fixing of an MOF cane to prevent its Therefore, to improve the MOF chirality, during the next stage, we replaced the stepper engine by a new commutator motor with a maximal rotation speed of 2000 revolutions per minute, and carried out a series of engineering and research and technological works on a second set of drawing tower modifications [89,90].…”

“…Therefore, to improve the MOF chirality, during the next stage, we replaced the stepper engine by a new commutator motor with a maximal rotation speed of 2000 revolutions per minute, and carried out a series of engineering and research and technological works on a second set of drawing tower modifications [89,90]. In addition to the design, fabrication, and installation of a new carrier for motor fixing on the feed unit chuck, a new drive belt with an improved length due to the increasing distance between the commutator motor shaft and feed unit chuck, a new special supporting pad with the fixed commutator motor, protective shroud, and driving system in the drawing tower feed unit, outside control panel, connected to power supply and driver for the commutator motor, we proposed and manufactured a special device for the additional fixing of an MOF cane to prevent its Therefore, to improve the MOF chirality, during the next stage, we replaced the stepper engine by a new commutator motor with a maximal rotation speed of 2000 revolutions per minute, and carried out a series of engineering and research and technological works on a second set of drawing tower modifications [89,90]. In addition to the design, fabrication, and installation of a new carrier for motor fixing on the feed unit chuck, a new drive belt with an improved length due to the increasing distance between the commutator motor shaft and feed unit chuck, a new special supporting pad with the fixed commutator motor, protective shroud, and driving system in the drawing tower feed unit, outside control panel, connected to power supply and driver for the commutator motor, we proposed and manufactured a special device for the additional fixing of an MOF cane to prevent its unacceptably strong vibrations in the horizontal plane with further destruction, occurring at a rotation speed of more than 300 revolutions per minute.…”

“…In addition to the design, fabrication, and installation of a new carrier for motor fixing on the feed unit chuck, a new drive belt with an improved length due to the increasing distance between the commutator motor shaft and feed unit chuck, a new special supporting pad with the fixed commutator motor, protective shroud, and driving system in the drawing tower feed unit, outside control panel, connected to power supply and driver for the commutator motor, we proposed and manufactured a special device for the additional fixing of an MOF cane to prevent its unacceptably strong vibrations in the horizontal plane with further destruction, occurring at a rotation speed of more than 300 revolutions per minute. This fixing device contains a ring stand with a clamped piece of fluoroplastic tube with a corresponding diameter, which was mounted between the tower feed unit and the tower furnace [89,90].…”