Abstract
Polarizing Panda-type W-fibers, practical realizations are presented for fiber-optic gyroscope (FOG) sensing coil (500-m length, 8-μm fundamental mode field diameter) and for polarization/modal filtering at the FOG loop interferometer input (∼1-m length, 10-μm fundamental mode field diameter). Using these fibers, two different mathematical models for light propagation are tested and applied for further dichroism spectral band spreading of polarizing W-fibers with fundamental mode field diameter (MFD) of 6 to 10 μm for FOG coil and at least with MFD=8 to 10 μm for input filtering in loop interferometer. Also, some fibers with large MFD are considered, which may be useful for high-power fiber lasers, requiring the low nonlinear effects. One is a practically realized single-mode 200-m W-fiber Panda with dichroism and MFD=12.4 μm at 1.06 μm, which is bend resistant for 60-mm diameters. For further MFD increase a straight 100-mm length modal and polarization filters are suggested with MFD=30 to 70 μm at 1.06 μm, based on a pure silica core fiber, narrow/shallow fluorine cladding, and stress-applying parts. The latter are used for core refractive index regulation by birefringence (W-profile forming), which is more precise than with core germanium doping.
Highlights
In single-mode (SM) fibers there are two mutually orthogonal fundamental polarization modes (x- and y-modes)
Recently,[20] we described PZ-fiber Panda based on highaperture core W-profile (Δnþ þ Δn− ∼ 0.015) and narrow, deep enough depressed clad (DC) (χ ∼ 1.7, Λ ∼ 0.6), where 2ρ 1⁄4 8.3 μm
We considered PZ-fibers based on refractive index W-profile
Summary
In single-mode (SM) fibers there are two mutually orthogonal fundamental polarization modes (x- and y-modes). A stable polarization is required in fiber communication lines[1] and fiber sensors.[2] It will improve the high-power fiber lasers’ performance.[3] fibers are necessary, polarizing (PZ) at least within a certain spectral range (window). For this dichroism window, we assume that within it, x-mode loss does not exceed 0.1 dB and y-mode loss is above 30 dB on a fiber whole length (10 dB for higher-order x-mode and fundamental y-mode losses in high-power fiber laser modal and polarization filters).
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