Method for making polarization-maintaining fiber optic patch cords

Polarization-maintaining fiber optic patch cords are made by carefully aligning PM fibers with connectors to preserve the light's polarization along a defined axis, using precision polishing and testing to ensure minimal loss and high extinction ratios.

Fiber Selection

Use Panda-type P

M fibers, which have stress rods that induce birefringence, locking the polarization along a slow or fast axis. The fiber must be single-mode and designed to maintain linear polarization over the desired wavelength range ( ).

Connector Alignment

Identify the PM axis of the fiber (slow or fast axis). Active alignment: During assembly, the fiber's major axis is aligned with the connector key using an interferometric or optical alignment station to ensure the polarization is preserved ( ). Connector types: Common connectors include FC/APC, LC, SC, and MPO/MTP.

The choice depends on system requirements and density ( ).

Termination and Polishing

Use butt-style or precision ferrule termination to minimize insertion loss. Ultra-fine end-face polishing reduces back-reflection and maintains signal integrity ( ). Ensure the fiber is free from stress or microbends during termination, as these can degrade polarization performance ( ).

Testing and Quality Control

Extinction Ratio (ER): Measure the ratio of power along the aligned axis versus the orthogonal axis to verify polarization preservation.

High-quality P

M patch cords typically have ER > 20 dB ( ). Insertion Loss (IL) and Return Loss (RL): Test each cord to ensure low optical loss and minimal reflection. Axis Verification: Confirm that the slow or fast axis orientation matches the system requirements.

Packaging and Handling

Cleanroom packing prevents contamination. Labeling: Include axis orientation, fiber type, and connector type for traceability. Avoid tight bends and mechanical stress during installation to maintain polarization integrity ( ).

Summary

The key steps in making PM fiber optic patch cords are: selecting the appropriate PM fiber, precisely aligning the fiber axis with the connector key, performing high-quality termination and polishing, and conducting rigorous testing for extinction ratio, insertion loss, and return loss. Proper handling and packaging ensure the cord maintains its polarization properties in demanding optical systems ( ).