Low-birefringence fiber for circularly polarized light

Spun optical fiber explained


What is low-birefringence spun fiber?
Low-birefringence optical fiber is produced by spinning fiber preform during drawing. That way all preform non-uniformities are spread out around all directions. As a result all polarization errors (retardations) accumulated by the propagating signal cancel each other out.

How is spun fiber different from regular PM fibers?
Highly birefringent fibers, such as Panda or Bow-tie maintain only linear polarization, while low-birefringence spun fiber maintains both linear and circular polarization states. Also because of spun fiber's uniformity there's no need to align the fiber when coupling light in our out.

Do spun fiber axes have to be aligned when splicing (similar to PM fibers)?
No, proper fiber orientation is not critical to polarimetric accuracy when using low-birefringent fiber.


Why does spun fiber have high local birefringence?
High local (internal) birefringence is created in spun fiber by creating stress in the cladding or employing elliptical core. This high birefringence negates other pressure or bend-induced polarization effects, but since its axis is rotated uniformly it introduces virtually no error into output signal.

What is the difference between spun fiber and twisted fiber?
Spun fiber preform is rotated during drawing, so the fiber cools down without residual torsional stress. Twisting the fiber after drawing results in similar polarization-maintaining qualities, and both types of fiber can be used to produce fiber-optic components, such as chiral fiber polarizers.

Does spun fiber have to be annealed?
No. Fiber high local birefringence makes it insensitive to other stress-induced effects.

What is the minimum bending radius for spun fiber?
Spun fiber's bend tolerance is determined largely by its diameter, beat length and pitch. Fibers with 5mm beatlength can be bent into 1cm coils without introducing unwanted birefringence.

What polarimetric accuracy can be achieved with spun fiber?
There is a balance between fiber bend tolerance and accuracy. Fibers with short beat length can withstand significant bends but high internal birefringence will introduce small retardation error. Longer beat length fibers are more sensitive to bending but provide better accuracy.

What is pitch?
Pitch (spin period) is the longitudinal period of fiber rotation. It is beneficial to have pitch as short as possible to achieve quality averaging.

Is there a way to measure pitch?
While there is no reliable way to measure pitch through polarimetry, but it can be estimated by inspecting stripped parts of the fiber.

What about cleaving, splicing and connectorizing spun fibers?
Low-birefringence fibers can be spliced, cleaved and terminated in exactly same way as the regular telecom fibers.

Do you offer connectorization?
Yes, we can terminate low-birefringence fibers with most fiber-optic connectors.

What about spun fiber configurations not listed in the datasheet?
It is certainly possible to arrange a custom draw of low-birefringence fiber. In fact, most of our spun fibers are tailored to a specific device or aplication. Options include optimized beat length, specific wavelength cut-off, reduced cladding and polyimide coating.



Spun optical fiber
LB650 | LB1060 | LB1300 | LB1300RC | PME1300-10