These spun optical fibers are specialty, high-birefringent fibers designed for demanding applications like Fiber Optic Current Sensors (FOCS) and Optical Current Transformers (OCT). Unlike traditional polarization-maintaining fibers, these fibers are created by spinning a bow-tie style, single-mode preform during the draw process, resulting in fibers that preserve circular polarization. This unique manufacturing process makes the output polarization insensitive to thermal and vibrational noise, as well as drift from stress-induced birefringence.
Key Features:
- Spun Design: The bow-tie rotates along the fiber’s axial direction.
- Wavelength Options: Available for 1310 nm (Item #’s SHB1250G80 and SHB1250) and 1550 nm (Item # SHB1500) laser sources.
- Polarization Stability: Preserves circular polarization; output polarization is stable against environmental factors.
- Application Focus: Ideal for AC and DC current sensing with FOCS and OCT.
How it Works (Faraday Effect):
These fibers capitalize on the Faraday effect, where a magnetic field causes a rotation in the polarization state of light. In current sensing, the current-carrying conductor generates the magnetic field. Because the magnetic field’s strength is proportional to the current, the polarization rotation is also proportional to the current. Coiling the fiber around the conductor increases sensitivity.
Benefits:
- Electrical Isolation: The fiber is isolated from voltage lines, reducing electrical noise.
- Sensitivity and Responsiveness: Fibers offer high sensitivity, fast response times, and are lightweight and compact.
Specifications:
| Fiber | SHB1250G80 | SHB1250 | SHB1500 |
|---|---|---|---|
| Operating Wavelength | 1310 nm | 1550 nm | |
| Cut-Off Wavelength | ≤1250 nm | ≤1500 nm | |
| Numerical Aperture | 0.13 – 0.17 | 0.13 – 0.16 | |
| Mode Field Diameter | 6.2 – 8.4 µm @ 1310 nm | 7.9 – 9.9 µm @ 1550 nm | |
| Attenuation | ≤5 dB/km @ 1310 nm | ≤3 dB/km @ 1550 nm | |
| Circular Beat Length | 63 – 125 mm @ 1310 nm | 72 – 144 mm @ 1550 nm | |
| Nominal Spin Pitcha | 4.8 mm | ||
| Proof Test | 100 kpsi (1%) | ||
| Cladding Diameter | 80 ± 1.5 µm | 125 ± 1 µm | |
| Core-Cladding Concentricity | 1.0 µm | ||
| Coating Diameter | 170 ± 10 µm | 245 ± 15 µm | |
| Coating Type | Dual Acrylate | ||
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