What is low-birefringence
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
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
What is the minimum bending radius for spun
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
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
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
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
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.