Customization of PM G.654 fibers involves precise preform design, stress element integration, mode field and numerical aperture optimization, and careful polarization alignment to ensure stable performance under environmental and power system stresses.

Fiber Design and Preform Fabrication

Polarization-maintaining fibers, such as the G.654 type, are designed to preserve the state of polarization (SOP) over long distances, which is critical in power system monitoring and high-speed optical communication. The customization process begins with preform fabrication, where the core and cladding materials are carefully selected for refractive index uniformity. Stress-inducing elements, such as PANDA (Polarization-maintaining AND Absorption-reducing) structures, are incorporated to break the degeneracy of the two principal polarization axes, creating a fast and slow axis for light propagation . These stress rods are precisely positioned to achieve high polarization extinction ratios and low polarization crosstalk.

Mode Field Diameter and Numerical Aperture Optimization

The mode field diameter (MFD) and numerical aperture (NA) are critical parameters for coupling efficiency and system integration. For G.654 fibers, which are optimized for low attenuation in the 1550–1625 nm range, the MFD is typically larger than standard single-mode fibers, reducing nonlinear effects and enabling high-power transmission . Customization involves measuring the effective numerical aperture (NAe2) for each fiber batch to ensure accurate coupling with optical components and minimize insertion loss .

Coating and Environmental Adaptation

To ensure reliability in power system environments, PM fibers are coated with polyimide or acrylate layers to enhance heat resistance, mechanical robustness, and bend tolerance . Customization may include small bend radius designs for compact installations in substations or aerial deployments, ensuring stable polarization maintenance even under temperature fluctuations, mechanical stress, or vibration.

Polarization Alignment and System Integration

A critical step in deployment is precise alignment of the fiber's polarization axis with the source laser's linear polarization. Misalignment can lead to elliptical polarization or partial depolarization, especially if the laser coherence length is shorter than the optical path difference between the two SOPs . Tools such as polarization analyzers and laser beam couplers are used to achieve high coupling efficiency and maintain the desired SOP. In power systems, dynamic polarization controllers may be integrated to compensate for polarization mode dispersion (PMD), polarization-dependent loss (PDL), and other environmental variations .

Testing and Quality Assurance

Customized PM fibers undergo rigorous testing for insertion loss, polarization extinction ratio, and environmental stability. Activation-induced loss and PDL are measured to ensure that feedback systems in dynamic polarization compensation do not degrade performance . Wide-bandwidth operation is verified for dense wavelength-division multiplexing (DWDM) systems, ensuring compatibility with high-speed monitoring and communication channels in power networks.

Summary

The customization of PM G.654 fibers for power systems involves:

• Preform design with integrated stress elements for polarization maintenance
• Optimization of MFD and NA for high-power, low-loss transmission
• Heat-resistant and bend-tolerant coatings for environmental robustness
• Precise polarization alignment with source lasers and dynamic compensation for PMD and PDL
• Comprehensive testing to ensure stable SOP and system reliability This process ensures that the fiber maintains high polarization fidelity, low loss, and reliable performance under the demanding conditions of modern power system optical networks .