Media converter Black Box LMC270A-MM-ST 10/100 Mbps RJ45 to 100BASE-FX multimode ST

Black Box LMC270A-MM-ST is a compact media converter that converts 10/100 Mbps Ethernet (RJ45) to 100BASE-FX over multimode fiber with an ST connector. The device enables connectivity between copper-based Ethernet equipment and multimode fiber links, extending network segments beyond the limits of twisted-pair cabling and providing enhanced immunity to electrical noise and ground-loop problems. Its form factor fits rack or desktop environments in offices, campuses and industrial sites where fiber uplinks or segment extension are required.

Advantages

The converter supports automatic negotiation on the copper port and a fixed 100 Mbps fiber interface, ensuring straightforward integration with existing 10/100 Mbps equipment. By using multimode fiber and an ST connector, it allows longer transmission distances compared with copper and reduces susceptibility to electromagnetic interference. The unit's compact design and low power consumption simplify deployment in constrained spaces, while transparent Ethernet forwarding preserves VLAN and MAC-level traffic characteristics.

Suitable for

• Extending Ethernet links between buildings, floors or remote closets
• Connecting switches, routers or servers to a multimode fiber backbone
• Removing ground-loop or EMI issues on copper Ethernet runs
• Upgrading segments to fiber where fiber uplink ports are required

Key specifications

• Data rates: 10/100 Mbps on copper port; 100 Mbps on fiber port
• Copper interface: RJ45, auto MDI/MDIX, auto-negotiation supported
• Fiber interface: 100BASE-FX multimode with ST connector
• Fiber type: multimode (MM) for short- to medium-range links
• Network forwarding: transparent Ethernet layer 2 forwarding
• Power: low-voltage DC input (check product label for required adapter)
• Form factor: compact desktop/rack-friendly enclosure

How to use

Install the converter near the copper device or at the fiber termination point. Connect the RJ45 Ethernet cable from the copper device to the RJ45 port on the converter and insert the multimode ST fiber connector into the fiber port. Apply the appropriate DC power supply and verify link/activity LEDs to confirm a successful connection. If connecting to equipment with fixed speed settings, ensure the copper side is set to a compatible speed or uses auto-negotiation.

Usage recommendations

Place the converter in a ventilated, dry location away from strong electromagnetic sources. Use matched multimode fiber cable and quality ST connectors for reliable links, and verify distance limits for multimode fiber runs. When integrating into managed networks, document the converter location and link details to aid future troubleshooting.