Communication Modules | Allen-Bradley 1786-RPFM

The 1786-RPFM is an Allen-Bradley ControlNet modular repeater medium-distance fiber optic module engineered to extend ControlNet network segments while maintaining high signal integrity. It converts copper coaxial signals into optical signals over a dual fiber optic channel, providing galvanic isolation and immunity against electromagnetic interference (EMI) across complex industrial control layouts.

Network Topology & Optical Transmission

Equipped with dual fiber optic channels, the module supports point-to-point, star, and redundant ring network architectures. It operates at an optical wavelength of 1300 nm and is optimized for 62.5/125 µm multimode fiber optic cables. The dual-channel design permits signal propagation up to 3000 m (9843 ft) across connected repeater links with a maximum allowable attenuation limit of 13.3 dB.

Backplane Integration & Module Compatibility

The 1786-RPFM functions as a daughter module designed to attach directly to a 1786-RPA ControlNet repeater adapter module. A single 1786-RPA base adapter supports up to four 1786-RPFM or mixed repeater modules, powered directly via the adapter backplane. The complete repeater assembly mounts onto standard 35 mm DIN rail enclosures.

Technical Specifications

Installation & Wiring Considerations

Before installing or servicing the fiber module, ensure power to the parent 1786-RPA adapter is disconnected to prevent optical transceiver degradation or electrical fault. Remove protective dust caps from the fiber optic connectors only when connecting pre-terminated 62.5/125 µm fiber cables. Maintain proper bend radius for all fiber cabling inside the cabinet to avoid excessive optical power loss.

Frequently Asked Questions

Q: Can the 1786-RPFM operate as a standalone repeater module?A: No, the 1786-RPFM is a modular extension module and requires a 1786-RPA repeater adapter to handle backplane power distribution and coaxial media interface.

Q: What type of optical cable is required for the 1786-RPFM?A: The module requires 62.5/125 µm multimode fiber optic cabling operating at a 1300 nm transmission wavelength.

Q: How many 1786-RPFM modules can be attached to a single 1786-RPA adapter?A: Up to four 1786-RPFM modules can be combined on a single 1786-RPA repeater adapter, subject to the maximum total current limit of 1.6 A at 5 VDC across all connected expansion modules.