Industrial Serial to Fiber Converter

Q: Will converting RS485 to fiber add delay and cause my Modbus RTU to timeout?

The VT-FB820 uses pure hardware decoding for zero-delay transparent transmission, preventing timeouts. The VT-FB810 converts to TCP/IP, but packet intervals can be set to 0ms to optimize speed.

Q: Can I connect the VT-FB820 directly to the SFP port on my Ethernet switch?

No. The VT-FB820 is a transparent serial modem and does not output Ethernet packets. To connect serial to an Ethernet fiber switch, you must use the VT-FB810.

Q: How do I connect my old SCADA software to the VT-FB810 if it only has COM1/COM2 settings?

Use the included VirCom software to map the IP data stream to a Virtual COM port (e.g., COM5) on your Windows PC. Legacy software can then connect to it seamlessly.

Q: Do I need to buy A and B units if I am using the VT-FB810 Serial Server?

Yes. The devices use Single-Mode Single-Fiber (WDM) technology, requiring a matched A-end (TX:1310) and B-end (TX:1550) pair to establish a connection.

Extend RS485 & RS232 over 20km with Absolute EMI Immunity

Stop changing burnt RS485 comm cards. Divide your PLCs, VFDs, and smart meters over large factory floors and substations. Select zero delay hardware decoding for pure extension or fancy Modbus TCP / IP gateways for seamless network integration.

Select Architecture Request A Quote

Engineering Decision: Which Architecture Do You Need?

Architecture 1

Pure Physical Extension

I just need to run my existing RS485/232 wires further than 1200m or through a highly noisy electrical area. I do not want to mess with IP addresses or network switches.

Zero-Delay Hardware Decoding
No IP Configuration Required
Transparent to all Serial Protocols

→ Solution: VT-FB820 (Transparent Modem)

Architecture 2

SCADA / Network Integration

I need to take serial data from a field sensor, push it over fiber, and plug it directly into my company’s Ethernet switch so my SCADA software can read it via TCP/IP.

On-board TCP/IP Stack
Modbus RTU to Modbus TCP
Virtual COM (VirCom) Software Support

→ Solution: VT-FB810 (Fiber Serial Server)

Serial Media Converter Matrix

Both series utilize Single-Mode Single-Fiber (WDM) and must be deployed in A/B pairs to function.

Hardware Series	Device Type & Logic	Interface (3-in-1)	Optical Wavelength	Action
VT-FB820 (A/B Pair) Requires both A & B units	Transparent Modem Zero-Delay Hardware Decoding	RS232 RS485 RS422	SC Port (20km) A:1310/1550nm \| B:1550/1310nm	Select Model
VT-FB810 (A/B Pair) Requires both A & B units	Fiber Serial Server / Gateway Modbus RTU/TCP & Virtual COM	RS232 RS485 RS422	SC Port (20km) A:1310/1550nm \| B:1550/1310nm	Select Model

Built for Extreme Reliability

Whether choosing transparent transmission or TCP gateway logic, both models share the same heavy-duty Valtoris hardware DNA.

Eliminate Ground Loops

RS485 networks traversing different buildings are notorious for destructive ground loops. Optical fiber provides infinite galvanic isolation, permanently solving voltage difference failures.

Universal 3-in-1 Serial Ports

Both models feature industrial terminal blocks for RS485/RS422 and a standard DB9 interface for RS232. Support broad baud rates from 1200 bps to 115200 bps.

Industrial Power Options

Powered by a flexible 9~24V DC input. We provide both a secure 5.08mm terminal block connection for cabinet DIN-rail setups and a 5.5mm DC plug for desktop use.

Harsh Environment Rated

Designed without internal cooling fans (which act as points of failure). Reliable operation from -40°C to 85°C housed inside an anti-radiation metal enclosure.

Simplify Your Serial Automation Architecture

If you require a pure transparent Modbus extension or a complete gateway to integrate legacy PLCs into your TCP network, our engineers will help you specify the right A/B pair.

Talk to an Engineer

Technical FAQs

Will converting RS485 to fiber add delay and cause my Modbus RTU to timeout?

A: Depends on the architecture you choose. If you choose the VT-FB820 (Transparent Modem), it’s all hardware decoding. It does not encapsulate data to IP packets, so transmission delay is almost zero (nanosecond range) assuring no Modbus timeouts. If you choose the VT-FB810 (Gateway), it buffers the data to convert it to TCP/IP, but you can adjust the “Packet Interval” to 0ms via its web interface to optimize serial speed.

Can I connect the VT-FB820 directly to the SFP port on my Ethernet switch?

A: No. The VT-FB820 is a raw serial physical-layer converter. It does not speak Ethernet/IP. If you plug its fiber cable into an IT network switch, the switch will not understand the data. If you need to plug a serial device into an Ethernet fiber switch, you must use the VT-FB810, which packages the serial data into standard TCP/IP network packets.

How do I connect my old SCADA software to the VT-FB810 if it only has COM1/COM2 settings?

A: You use our included VirCom (Virtual COM) software. You install VirCom on your SCADA PC (Windows). It captures the IP data coming from the VT-FB810 over the network and creates a “fake” local COM port (e.g., COM5) on your computer. Your legacy software connects to COM5 exactly as if the RS485 wire was plugged directly into the back of the PC.

Do I need to buy A and B units if I am using the VT-FB810 Serial Server?

A: Yes. Both the VT-FB810 and VT-FB820 utilize Single-Mode Single-Fiber (WDM) technology to save cabling costs. Because they transmit and receive over one strand of glass using different light colors, you must always order an A-end (TX:1310) and a B-end (TX:1550) to complete the link.