Allen-Bradley OCM-DPR-85-D-ST Ruggedized Fiber Optic Module

Product Overview

Allen-Bradley OCM-DPR-85-D-ST Ruggedized Fiber Optic Communication Module for Harsh Industrial Environments

The Allen-Bradley OCM-DPR-85-D-ST is a dual-port, 850 nm ST-connector fiber optic communication module engineered for the Rockwell Automation PLC-5 programmable controller platform. Designed to operate reliably in the most demanding industrial conditions — including high-temperature process areas, high-humidity coastal facilities, dust-laden mining environments, and electrically noisy heavy manufacturing floors — this module delivers deterministic, EMI-immune data transmission across the full PLC-5 remote I/O network. Where copper-based communication links fail under electromagnetic interference from large variable frequency drives, motor control centers, or high-voltage switchgear, the OCM-DPR-85-D-ST maintains signal integrity without compromise.

In continuous production environments such as petrochemical refineries, offshore oil and gas platforms, and steel mill automation systems, communication reliability is not optional — it is a safety-critical requirement. The OCM-DPR-85-D-ST addresses this by converting electrical signals to optical pulses, completely isolating the PLC-5 processor from ground loops, surge transients, and radiated emissions that routinely disrupt copper-based remote I/O links. This galvanic isolation also protects the 1785-series PLC-5 processor rack from damage caused by ground potential differences between geographically separated control cabinets — a common failure mode in large-footprint facilities such as water treatment plants and power generation stations.

Rugged Specifications Table

Comprehensive Protection Solutions

The OCM-DPR-85-D-ST does not operate in isolation — it is a critical link in a broader Allen-Bradley PLC-5 control architecture. In a typical large-scale control cabinet deployment, the module interfaces directly with the 1785-L80B or 1785-L60B PLC-5 processor, extending the remote I/O network over multimode fiber to distributed 1771-series I/O chassis located hundreds of meters away on the plant floor. Each remote I/O chassis may house 1771-IFE analog input modules reading temperature and pressure transmitters, 1771-OFE analog output modules driving control valves, and 1771-IAD digital input modules monitoring field device status — all communicating reliably through the fiber optic link established by the OCM-DPR-85-D-ST.

In facilities where variable frequency drives such as the PowerFlex 700 or PowerFlex 4M generate significant conducted emissions on the plant power bus, the fiber optic isolation provided by the OCM-DPR-85-D-ST prevents these disturbances from corrupting I/O scan data. Similarly, in control panels where 1492-series terminal blocks and 700-series relay modules are densely packed alongside the PLC-5 rack, the module’s optical isolation eliminates the risk of common-mode noise coupling into the communication bus. For installations requiring safety-rated communication, the OCM-DPR-85-D-ST can be integrated alongside GuardLogix safety controllers and 1791DS-series safety I/O modules, with the fiber link providing the physical separation required by IEC 61508 functional safety standards.

Power supply integrity is equally important in harsh environments. The 1606-series industrial power supplies from Allen-Bradley provide the stable 24 VDC backplane power that the PLC-5 system — and by extension the OCM-DPR-85-D-ST — requires for uninterrupted operation. In high-vibration environments such as mining conveyors or offshore drilling platforms, the 1771-series I/O chassis mounting hardware and the fiber optic cable management system must be selected to match the mechanical demands of the site, ensuring that the optical connectors at both ends of the OCM-DPR-85-D-ST link remain securely seated under continuous vibration.

Application in Critical Infrastructure

In oil and gas upstream and midstream facilities, the OCM-DPR-85-D-ST enables PLC-5-based control systems to extend remote I/O networks across hazardous classified areas without introducing electrical ignition sources. Fiber optic links are inherently intrinsically safe in terms of ignition energy, making the OCM-DPR-85-D-ST a preferred communication solution for wellhead control panels, pipeline SCADA outstations, and compressor station automation systems operating in Class I, Division 2 or Zone 2 environments.

In underground coal and metal mining operations, where electromagnetic interference from high-power haulage equipment and blasting circuits is severe, the OCM-DPR-85-D-ST’s immunity to EMI ensures that the PLC-5 remote I/O network continues to deliver accurate process data to the surface control room without bit errors or communication timeouts. This reliability is essential for conveyor belt safety interlock systems, ventilation fan control, and dewatering pump automation — all of which are life-safety-critical applications where a communication failure can trigger an emergency shutdown or, worse, a missed alarm condition.

In electric power generation and transmission substations, the OCM-DPR-85-D-ST provides the galvanic isolation necessary to protect PLC-5 control systems from the high-energy transients generated by switching operations on high-voltage busbars. Water and wastewater treatment plants operating 24/7 rely on PLC-5 systems with OCM-DPR-85-D-ST modules to maintain continuous communication between the central SCADA system and remote pump stations, chemical dosing skids, and filtration control panels distributed across large treatment campuses. In steel and metals processing, where induction furnaces and rolling mill drives create extreme electromagnetic environments, the fiber optic link is the only communication medium that can guarantee data integrity across the plant floor.

Security & Quality FAQ

Q1: What does the 12-month warranty cover for the OCM-DPR-85-D-ST?
The 12-month warranty covers all manufacturing defects and functional failures under normal operating conditions from the date of shipment. If the module fails to perform its specified fiber optic communication function within the warranty period, TOPNLMS will provide a replacement or full refund. The warranty does not cover damage resulting from incorrect installation, overvoltage events beyond the module’s rated tolerance, or physical damage caused by improper handling.

Q2: How is the OCM-DPR-85-D-ST tested before shipment?
Every OCM-DPR-85-D-ST unit undergoes a full functional test prior to shipment. Testing includes power-on verification, optical transmitter and receiver output level measurement, and communication loop-back testing to confirm that both fiber optic ports are operating within Allen-Bradley’s original factory specifications. Units that do not pass all test criteria are quarantined and not shipped. A test report is available upon request for customers with quality management system requirements.

Q3: Is the OCM-DPR-85-D-ST compatible with all PLC-5 processor variants?
The OCM-DPR-85-D-ST is designed for use with the Allen-Bradley PLC-5 family, including the 1785-L11B, 1785-L20B, 1785-L40B, 1785-L60B, and 1785-L80B processors, as well as the PLC-5/250 and PLC-5/VME variants that support remote I/O communication. It is not compatible with ControlLogix or CompactLogix platforms, which use different communication architectures. If you are migrating from a PLC-5 system to a ControlLogix platform, TOPNLMS can advise on the appropriate 1756-series communication modules for your new architecture.

Q4: Can TOPNLMS guarantee long-term supply of the OCM-DPR-85-D-ST for ongoing maintenance programs?
Yes. TOPNLMS maintains dedicated inventory of legacy Allen-Bradley PLC-5 communication modules, including the OCM-DPR-85-D-ST, specifically to support customers with long-lifecycle industrial control systems that cannot be easily migrated. We source modules through verified supply channels and maintain stock levels to support both emergency replacement orders and planned preventive maintenance programs. Customers with annual maintenance contracts or multi-unit requirements are encouraged to contact us to discuss reserved stock arrangements and volume pricing.