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What is a polarizing FIBER?
A polarizing fiber (often abbreviated as a PZ fiber) is a highly specialized single-mode specialty optical fiber designed to guide only one specific linear state of polarization while rapidly suppressing or attenuating the orthogonal polarization state. Unlike standard polarization-maintaining (PM) fibers that preserve two orthogonal states of light traveling at different speeds, a polarizing fiber functions as a continuous, distributed inline polarizer.
Its primary purpose is to deliver a fundamentally pure, single polarization output over a broad wavelength window, eliminating the need for bulk optical polarization components in high-precision setups.
HOW a Polarizing FIBER Works
The filtering mechanism of a polarizing fiber is achieved by combining extreme internal stress with deliberate waveguide leakage, following three main operational steps:
High Birefringence Generation
The fiber features an asymmetric internal structure, such as an integrated "Tiger" or Panda-style stress geometry near the core. This intentional structural asymmetry generates high birefringence, splitting the light into two distinct polarization modes: the guided mode and the suppressed mode.
Selective Cut-Off and Leakage
Through careful optimization of the waveguide design and glass composition, the refractive index profile is tailored so that the fundamental cut-off wavelengths for the two polarization modes are separate. This forces the unwanted polarization state to fall outside its guidance limits, turning it into a leaky mode that radiates out into the cladding.
Coiling-Enhanced Attenuation
When the fiber is deployed—often optimized by wrapping it into a specific coil diameter—the micro-bending loss for the leaky polarization state increases exponentially. The desired polarization state continues down the core with minimal attenuation, resulting in an exceptionally high polarization extinction ratio (PER) at the fiber output.
