Fiber Converter

A Fiber Converter (also known as a media converter or fiber optic transceiver) is a device that converts electrical signals from copper-based communication interfaces (such as Ethernet, RS‑232, RS‑485, or fieldbus protocols) into optical signals for transmission over fiber optic cables, and vice versa. In AGL applications, fiber converters are deployed to extend communication distances far beyond the limits of copper cabling (typically 100 m for Ethernet) while providing complete galvanic isolation and immunity to electromagnetic interference (EMI) from high-voltage AGL power circuits, lightning, and nearby RF transmitters. They are essential for connecting remote CCR substations, field junction boxes, and sensor nodes back to the central ALCMS control room, enabling robust, high-speed, and secure data communication across the entire airfield.

The fiber converter exists to solve two problems copper cabling can't handle well on an airfield: distance and electrical noise. Copper Ethernet is limited to roughly 100 metres before signal quality degrades, far short of what's needed to reach CCR substations and field cabinets scattered across a large airfield, and copper runs near high-voltage AGL circuits or exposed to lightning strikes are vulnerable to induced surges that can damage sensitive control electronics.

By converting to optical signals for the long-haul run, the converter both extends communication reach well beyond copper's practical limit and provides complete galvanic isolation between the remote field equipment and the central control room, protecting both ends of the link from electrical faults or transients that might otherwise propagate through a continuous copper connection.

Fiber converters are deployed throughout the airfield wherever long-distance, noise-immune communication is required. Key applications include:

• ALCMS Network Backbone: Connecting the central ALCMS server to remote substations and field controllers over fiber optic rings or point-to-point links.
• CCR Substation Connectivity: Providing Ethernet or fieldbus communication between the main PLC cabinet and remote CCR units located at runway ends or substations.
• Remote I/O Networks: Extending fieldbus or Ethernet communication to distributed Remote I/O modules located in runway edge cabinets, junction boxes, and approach light shelters.
• RWSL (Runway Status Light) Systems: Linking RWSL sensors, stop bar controllers, and processing units to the central control system.
• Approach Lighting Control: Communicating with remote approach light control cabinets and sequencer modules.
• Airfield Sensor Networks: Connecting weather sensors, wind measurement systems, visibility sensors, and RVR systems to the ALCMS.
• Surveillance & Radar Systems: Transmitting radar and surveillance data from remote sensor locations to ATC and control centers.
• Inter-building Links: Connecting terminal buildings, ATC towers, maintenance facilities, and fire stations to the airfield communication network.

Converters are DIN-rail mounted inside the field cabinet or shelter at each end of the fibre run, paired with a matching unit at the ALCMS server room or the remote substation it connects to. Fibre entry to the cabinet is via a dedicated gland or patch panel kept separate from the copper power and signal glands, with enough slack coiled inside the cabinet to allow re-termination without pulling more cable from the duct run; outdoor cabinet installations use a sealed, temperature-rated converter rather than an indoor-only unit. The copper (Ethernet or fieldbus) side connects to the local PLC, Remote I/O, or switch on a short patch cable, keeping the electrically-isolated fibre run as the only long-distance link between the two ends.

The fiber converter operates by translating electrical signals into optical pulses and vice versa. Key functional aspects include:

• Signal Conversion: On the electrical side, the converter interfaces with copper media (e.g., RJ‑45 Ethernet, RS‑485 terminals) and extracts the digital data stream. On the optical side, it drives a laser or LED (light-emitting diode) to transmit corresponding light pulses over single-mode or multi-mode fiber.
• Wavelength Management: Fiber converters operate at specific wavelengths—typically 850 nm (multi-mode), 1310 nm, or 1550 nm (single-mode)—depending on the fiber type and distance. Some models support wavelength division multiplexing (WDM) to send and receive data on a single fiber.
• Media Independence: Converters are protocol-agnostic at the physical layer, supporting a wide range of protocols including Ethernet (10/100/1000BASE-T), Profibus, Modbus, RS‑232, RS‑485, and others, making them versatile for various AGL applications.
• Galvanic Isolation: The optical link provides complete electrical isolation between the two ends, protecting sensitive control equipment from ground loops, voltage surges, and lightning-induced transients that are common on airfield copper cabling.
• Distance Extension: Fiber converters enable communication over distances up to 2 km (multi-mode) or 80+ km (single-mode), far exceeding the 100 m limit of copper Ethernet.
• Diagnostics & Monitoring: Advanced converters provide link status LEDs, optical power monitoring, and link-loss alarm contacts, enabling proactive maintenance and rapid fault isolation.

Fiber converters are typically powered by 24 VDC (airfield standard) or 12 VDC, and are housed in rugged industrial enclosures suitable for outdoor or substation environments.

The fiber converter sits at the transition point between a short copper Ethernet run at a piece of equipment (a CCR cabinet, remote substation, or field enclosure) and the fibre backbone that carries the signal the longer distance across the airfield. It is protocol-transparent — whatever frames arrive on the copper side are re-encoded as optical pulses and sent unchanged, so from the ALCMS server's perspective the converter is invisible and the PLC or switch on the far end appears to be on the same local segment. A matching converter at the far end restores the signal to copper before it reaches the destination switch or device. Because the airfield's fibre backbone is what actually links physically separated equipment rooms, substations, and the central ALCMS, a converter or fibre fault at any one point breaks connectivity for everything downstream of it on that run, independent of whether the copper-side equipment itself is healthy.

The converter is built into a compact extruded-aluminium or plastic DIN-rail housing sized to fit alongside other control-cabinet devices, with the electrical interface (RJ-45, terminal block, or fieldbus connector) on one face and the fibre-optic connectors (SC, ST, or LC) on the opposite face to keep copper and optical cabling physically separated. The optical transceiver is a sealed SFP or fixed-pigtail module mounted directly to the internal circuit board, isolating the copper-side electronics from the fibre link and providing the galvanic isolation the device is chosen for. Internal electronics are conformally coated against dust and humidity, and where the unit must be field-mounted outside a cabinet, it is housed in a sealed IP65 enclosure with cable glands for the copper conductor entry and a sealed fibre feedthrough. Power terminates at a screw-clamp terminal block rated for the 24 VDC (or 12 VDC) nominal supply, with a chassis earth stud provided for cabinet grounding.