Even for future proofing as fibre optical digial cable is the modern future proofing option if deciding to spend more than this. They're impossible to fit RJ12 plugs so they use fakes with strandsinstead of solid wiring like mine!
eBay
Single mode dual fibre ST 20 km.
eBay
1 x Open SFP (MSA Compliant). Manufacturer Product Type Startech Other Interface/Add-On Cards. It converts a fiber network link to a PoE-enabled copper RJ45 Ethern. Fiber optic connector SFP. Power over Ethernet (PoE) Yes.
eBay
This listing is for a vintage Allied Telesyn MC13 Ethernet Media Converter, designed to convert 10Base-T Ethernet (RJ45) to 10Base-F Fiber Optic. A great item for networking enthusiasts, collectors, or those maintaining legacy systems. Power adapter not included
eBay
Fibre to ethernet converter. Serial numbers have been noted.
eBay
The StarTech GbE Copper to Fiber Converter SM LC 20km (ET91000SM20) is a robust and versatile solution for extending Gigabit Ethernet networks over long distances using single-mode fibre optic cable. ... Click the "See full description" link below for more details.
eBay
Data transmission speed: 100M. Due to different lighting and screen settings, the color of this item may be slightly different from the picture. Compressive strength: 250P. Tensile strength: 1000N.
eBay
Manufacturer Product Type Startech Other Interface/Add-On Cards. Fiber ports quantity 1. Product colour Silver. Fiber optic connector LC. Fiber ethernet cabling technology 1000BASE-LX. Ethernet LAN (RJ-45) ports 1.
eBay