Allen-Bradley 1786-RPFM ControlNet Modular Repeater Medium-distance Fiber Module

Configured for optical media conversion and distance extension in ControlNet industrial networks, the Allen-Bradley 1786-RPFM (1786-RPFM ControlNet Modular Repeater Medium-distance Fiber Module) provides direct physical execution of coaxial-to-fiber signal transition across segments up to 3 km.

Hardware Specifications

Deterministic Backplane Bus & Fiber Physical Layer Behavior

The 1786-RPFM interfaces directly with a 1786-RPA adapter via the backplane bus to maintain 5 Mbps deterministic network execution across extended fiber links. Up to four 1786-RPFM modules can be attached to a single 1786-RPA adapter, provided total backplane current draw remains within the 1.6 A @ 5 VDC threshold. The optical transceiver operates at a 1300 nm wavelength, translating electrical ControlNet signals into optical pulses to prevent ground loops, eliminate cross-talk, and maximize noise immunity in high EMI industrial environments. Fiber link integrity depends on keeping optical attenuation below the maximum budget of 13.3 dB across all connectors, splices, and cable runs.

Frequently Asked Questions

Q: How many 1786-RPFM modules can be attached to a single 1786-RPA base adapter?

A: A maximum of four 1786-RPFM repeater modules can be attached to one 1786-RPA base adapter, provided the total combined current draw of all expansion modules does not exceed 1.6 A @ 5 VDC from the backplane.

Q: What determines the maximum achievable distance of a fiber segment using the 1786-RPFM module?

A: While the typical segment length is rated up to 3 km (9843 ft), actual distance limits are defined by the optical loss budget. The total signal attenuation across the OM-1 62.5/125 micron fiber cable, connectors, and splices must not exceed 13.3 dB at 1300 nm.

Field Installation Guidelines

1. Enclosure Requirements: Install the module inside an IP54 or NEMA Type 4 rated industrial enclosure accessible only via tool usage to prevent direct exposure to live electrical backplane components.
2. Mounting Orientation: Secure the module on a standard DIN rail or panel surface using vertical or horizontal mounting orientation. Ensure adequate clearance around the backplane bus header for solid mechanical latching with the 1786-RPA base module.
3. Fiber Cable Handling: Use 62.5/125 micron OM-1 multimode fiber optics terminated with ST connectors. Ensure minimum bend radius limits specified by the cable manufacturer are strictly observed to avoid micro-bends that induce optical signal loss.
4. Connector Maintenance: Clean all ST optical connectors and receiver/transmitter ports with lint-free optical wipes and isopropyl alcohol prior to insertion. Dust caps must remain installed on unused ports at all times.
5. Attenuation Testing: Perform an Optical Time-Domain Reflectometer (OTDR) test or optical power meter verification after installation to confirm total link loss remains well under the 13.3 dB maximum threshold before applying power.