# Towards fully commercial, UV-compatible fiber patch cords

## TL;DR

This paper develops and analyzes methods to produce UV-compatible fiber patch cords with stable long-term transmission at high powers, addressing a critical gap for scientific and industrial applications.

## Contribution

It introduces two pathways for manufacturing solarization-resistant, hydrogen-passivated, polarization-maintaining UV fiber patch cords with detailed fabrication, handling, and mitigation techniques.

## Key findings

- Stable transmission over months at 313 nm with >10 kJ energy exposure.
- Polarization extinction ratios between 15 dB and 25 dB at 313 nm.
- Particle deposition effects can be mitigated by nitrogen purging.

## Abstract

We present and analyze two pathways to produce commercial optical-fiber patch cords with stable long-term transmission in the ultraviolet (UV) at powers up to $\sim$ 200 mW, and typical bulk transmission between 66-75\%. Commercial fiber patch cords in the UV are of great interest across a wide variety of scientific applications ranging from biology to metrology, and the lack of availability has yet to be suitably addressed. We provide a guide to producing such solarization-resistant, hydrogen-passivated, polarization-maintaining, connectorized and jacketed optical fibers compatible with demanding scientific and industrial applications. Our presentation describes the fabrication and hydrogen loading procedure in detail and presents a high-pressure vessel design, calculations of required \Ht\ loading times, and information on patch cord handling and the mitigation of bending sensitivities. Transmission at 313 nm is measured over many months for cumulative energy on the fiber output of > 10 kJ with no demonstrable degradation due to UV solarization, in contrast to standard uncured fibers. Polarization sensitivity and stability are characterized yielding polarization extinction ratios between 15 dB and 25 dB at 313 nm, where we find patch cords become linearly polarizing. We observe that particle deposition at the fiber facet induced by high-intensity UV exposure can (reversibly) deteriorate patch cord performance and describe a technique for nitrogen purging of fiber collimators which mitigates this phenomenon.