The 405 nm Single Mode Patch Cord from DK Photonics is a precision‑engineered fiber optic jumper designed specifically for short‑wavelength applications in the near‑UV and violet spectral region. Unlike generic telecom patch cords optimized for 1310 nm or 1550 nm, this cable is built around specialty single mode fiber (such as S405‑XP class fibers) that maintains true single‑mode performance around 405 nm. This ensures a clean, well‑defined mode field, excellent focusability, and superior beam quality for demanding photonics setups in laboratories, industrial systems, and OEM instruments.

Each patch cord is manufactured with tight control over insertion loss and return loss to provide stable, repeatable optical performance. High return loss minimizes back reflections that can destabilize lasers or introduce noise into sensitive detection systems, while low insertion loss helps preserve source power and maximize system signal‑to‑noise ratio. Combined with robust connector polishing (PC or APC) and strict quality control, the cable delivers excellent long‑term stability and reliability, even in setups requiring frequent reconnection or reconfiguration.

The 405 nm Single Mode Patch Cord is available with a variety of connector options, including FC, LC, and SC in both PC and APC polish styles, to seamlessly integrate with common fiber‑based components such as laser sources, couplers, circulators, isolators, and measurement instruments. FC/APC connectors with a narrow 2.0 mm key are frequently chosen for precision, low‑back‑reflection coupling in laser and metrology environments, while FC/PC, SC/PC, or LC/PC variants support general laboratory and OEM usage. The mode field diameter is carefully matched to the wavelength regime, supporting efficient coupling into and out of 405 nm diode lasers, fiber‑coupled sources, and collimators.

In systems such as fiber lasers, optical transmitters, transceivers, and fiber‑optic instruments, stable performance at 405 nm is critical. This patch cord offers excellent mechanical and environmental robustness, supported by options such as 0.9 mm loose‑tube protection or larger jacket diameters for improved handling and strain relief. The standard length tolerance of ±5 cm is suitable for most applications, and DK Photonics can further tighten or modify this tolerance when more precise fiber routing is required, for example in interferometric setups or compact OEM modules.

The product is particularly suitable for use as a fiber I/O port for laser heads, spectrometers, fluorescence excitation systems, confocal microscopes, and other imaging or sensing platforms operating in the violet region. High return loss and low insertion loss help maintain laser linewidth and stability, reduce parasitic feedback into the source, and support accurate, repeatable measurements. In research and development environments, the combination of low loss, repeatable connector geometry, and carefully specified mode field characteristics enables reliable coupling into micro‑optics, photonic devices, and fiber‑based interferometers.

Because 405 nm single mode fibers are more sensitive to bending and handling than standard telecom fibers, the patch cord is designed to maintain performance over its service life when used within recommended bend radius guidelines. The excellent stability and reliability make it a strong choice not only for laboratory benches but also for integration into production equipment and long‑term deployed systems where downtime and drift must be minimized. Each assembly is typically tested for insertion loss and return loss at the specified wavelength, providing users with confidence that the patch cord will perform as expected right out of the box.

The ordering structure for this series allows users to specify grade, fiber type, buffer or jacket size, length, and connector configuration. A typical example, such as SMPC‑405‑P‑S40‑90‑20‑FA, would denote a 405 nm single mode patch cord with performance grade “P,” S405‑type single mode fiber, 0.9 mm loose‑tube buffer, 2 m length, and FC/APC connectors on all ports. For non‑standard lengths, special connector combinations, tighter tolerances, or integration into complex fiber assemblies, the platform supports extensive customization with short lead times, making it suitable for both one‑off experimental setups and large‑scale OEM deployment.