Order now 1786-RPFM to eliminate electromagnetic interference and extend your industrial network over medium distances with absolute signal stability. The Allen-Bradley 1786-RPFM is a high-performance Fiber Optic Repeater Module designed for the ControlNet modular repeater system. Specifically engineered for medium-distance communication, this module converts electrical ControlNet signals into optical pulses, allowing data to travel through fiber optic cabling that is completely immune to the high-voltage noise and grounding issues prevalent in heavy industrial environments. The 1786-RPFM is a plug-in module that must be paired with a 1786-RPCD or 1786-RPCH adapter. By utilizing fiber optics, this module supports segment lengths of up to 3,000 meters (approx. 9,840 feet) using 62.5/125 micron multi-mode fiber. This capability is essential for connecting remote I/O racks in separate buildings or across large factory floors where standard coaxial cable would suffer from significant signal attenuation or data corruption due to nearby variable frequency drives (VFDs) and large motor starters.
What Is the 1786-RPFM?
The 1786-RPFM is a medium-distance fiber optic repeater module that provides a single fiber port (one transmit, one receive) using standard ST connectors. It operates as a transparent signal regenerator within the ControlNet physical layer. When an electrical signal reaches the repeater rack via a 1786-RPCD adapter, the 1786-RPFM converts it to light for transmission. At the other end of the fiber link, another 1786-RPFM converts the light back into an electrical signal. This process is deterministic and does not introduce measurable latency into the 5 Mbps ControlNet sweep, ensuring that time-critical safety and control data arrive exactly when expected, regardless of the physical distance or the presence of intense EMI/RFI noise.
Key Technical Specifications
- Part Number: 1786-RPFM
- Manufacturer: Allen-Bradley / Rockwell Automation
- Fiber Type: 62.5/125 micron Multi-mode Fiber
- Maximum Distance: 3,000 meters per segment
- Wavelength: 820 nm
- Optical Budget: 13.3 dB
- Connector Type: ST (Straight Tip) connectors
- Communication Rate: 5 Mbps
- Status Indicators: Dual LEDs for module status and port activity
Fiber Optic Advantages in ControlNet
The primary advantage of the 1786-RPFM is total electrical isolation. In many industrial sites, ground potential differences between buildings can destroy standard copper-based communication modules. Fiber optics solve this by removing the electrical path between segments. Additionally, because the signals are transmitted as light, they cannot be affected by the massive magnetic fields generated by industrial machinery. This makes the 1786-RPFM the ideal choice for mining, wastewater treatment, and power generation facilities where reliability in harsh conditions is a non-negotiable requirement.
Installation Advice
When installing the 1786-RPFM ST connectors, absolute cleanliness is paramount. Even a microscopic dust particle on the fiber end can cause significant signal loss (decibel drop), leading to intermittent network timeouts. Always use lint-free swabs and 99% isopropyl alcohol to clean the fiber tips before insertion. Furthermore, ensure that you respect the minimum bend radius of your fiber optic cable; over-bending can cause micro-fractures in the glass core, which may not fail immediately but will degrade the signal over time, causing mysterious network drops that are difficult to diagnose without specialized optical time-domain reflectometry (OTDR) equipment.
Frequently Asked Questions
Q: Can I mix 1786-RPFM and 1786-RPFS modules in the same rack?
A: Yes, the 1786 modular repeater system allows for a mix of fiber and coaxial modules. This allows you to tailor each port to the specific distance and environment of the connected segment.
Q: What does a solid red LED on the 1786-RPFM indicate?
A: A solid red LED typically indicates a hardware fault or a complete loss of optical signal (Link Loss). Check the fiber integrity and ensure the remote end is powered and transmitting.
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