Industrial Serial to Fiber Media Converter & RS485 Extender

Engineered for harsh industrial environments, the VT-FB820 Industrial Serial to Fiber Converter provides zero-delay, point-to-point serial telemetry over single-mode fiber up to 20km. With absolute EMI immunity and native hard-decoding, it seamlessly bridges RS232, RS485, and RS422 signals without the latency of IP-based servers. 

Part No. VT-FB820
sku : IoT-OF102
INSTANT QUOTE

Industrial Serial to Fiber Extension

As a robust Industrial Serial to Fiber Converter, the VT-FB820 extends RS485, RS232, and RS422 signals up to 20km via Single-Mode SC fiber. It delivers 100% galvanic isolation against severe industrial EMI and ground loops.

VT-FB820 Product Show

Point-to-Point Topology

Functions as a transparent, invisible serial cable between remote PLCs and central SCADA servers. Ideal for continuous, high-speed polling environments.

Primary function point-to-point fiber topology
Industrial Application Scenarios for Serial to Fiber Bridge

Zero-Delay Hardware Decoding

Utilizes physical-layer hard-decoding for single-bit transmission. Achieves true zero-delay real-time communication, outperforming IP-based serial servers that buffer packets.

Low latency zero delay for data transfer in pairs
The difference between VT-FB810 Serial Server and VT-FB820 Media Converter

True Plug-and-Play

Auto-senses baud rates up to 115200 bps and adapts to all serial formats. No DIP switches, IP settings, or software configuration required.

Three interfaces RS232 RS485 RS422 Supported
Serial port parameter auto-adaptation is not required
You do not need to configure network parameters

Industrial Power & Mounting

Supports DC 9~24V wide voltage input via 5.5mm jack or terminal block. Features a compact SECC chassis with wall-mount flanges and optional DIN-rail compatibility.

Wide voltage DC 9 to 24V industrial power supply inputs
Power plug Standard power supply and Terminal power supply
Support Rail mount and Wall mount installation

Click to purchase Rail mounting clips

Status Indicators & Dimensions

Dedicated LED indicators for Power, Fiber Link, and Bi-directional Data (TX/RX) enable instant on-site diagnostics.

Rich Indicator light for diagnostics
VT-FB820 Outline dimensions schematic

Hardware & Interfaces
Serial Ports1x RS232 (DB9) / 1x RS485 & RS422 (Terminal Block)
Power Input9~24V DC (5.5mm Jack or Terminal Block)
Power Consumption357mA @ 9V
Fiber Optic Communication
Fiber TypeSingle-Mode, Single-Fiber, Bi-directional
Optical ConnectorStandard SC Interface
Transmission DistanceUp to 20 Kilometers
Wavelength (A-End)TX: 1310nm / RX: 1550nm
Wavelength (B-End)TX: 1550nm / RX: 1310nm
Serial Data Parameters
Baud RateAuto-adaptive up to 115200 bps
Data & Check Bits5~9 Data Bits. None, Odd, Even, Mark, Space
Mechanical & Environment
Dimensions9.4cm × 6.5cm × 2.5cm (L x W x H)
Operating Temp.-40°C to +85°C
VT-FB820 Key Advantages
✓ 20km Extension: Offers long distance serial telemetry over Single-Mode SC fiber easily overcoming standard RS232/RS485 distance limitations.
✓ Zero EMI Susceptibility: Provides complete galvanic signal isolation. Your serial data is converted to light, so you’ll have no ground loops or electromagnetic interference.
✓ Universal Serial Interface: Auto-sensing port with support for RS232, RS485 and RS422. No manual jumpers or software switching required
✓ True Plug & Play: Requires absolutely zero software configuration. It automatically adapts to your PLC’s baud rate and parity. Just plug in and power on.
✓ Zero-Delay Hardware Decoding: Unlike IP-based servers that must buffer 8-bit packets, the VT-FB820 hard-decodes single-bit data for real-time transmission. Perfect for high-speed SCADA polling.

Frequently Asked Questions

Why must the VT-FB820 be purchased and used in A/B pairs?
Because it uses a Single-Fiber core, it relies on Wavelength Division Multiplexing (WDM) to prevent signal collision. The A-End unit transmits at 1310nm and receives at 1550nm, while the B-End unit does the exact opposite (TX 1550nm / RX 1310nm). Two identical units cannot talk to each other.
What is the main difference between the VT-FB820 and the VT-FB810?
The VT-FB810 is a Serial Device Server; it converts serial data into TCP/IP network packets, which introduces a slight processing delay, but allows connection to Ethernet switches. The VT-FB820 is a pure physical layer media converter. It uses single-bit hardware decoding for true real-time, zero-delay transmission, acting exactly like a very long, invisible serial cable.
Can I use Multi-Mode fiber cables with this converter?
No. The VT-FB820’s laser optic module is strictly designed for Single-Mode (SM) fiber. Using multi-mode cables will result in severe modal dispersion, signal degradation, and link failure.
Do I need to configure the baud rate to match my PLC?
No configuration is needed. The VT-FB820 features an auto-sensing transparent bridge that automatically detects and adapts to baud rates up to 115200 bps, passing your serial payloads exactly as received.

[RS232 to Ethernet Cable Pinout: Two Common Wiring Diagrams] — Before your data travels across the optical fiber, you must physically connect your PLC to the VT-FB820’s serial port. Use this guide to ensure your RS232 DB9 (TX/RX) crossover wiring is correct at the terminal end.

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Available in A-End and B-End pairs. Fast global shipping included.

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