Glass optical fiber RS485 repeater – TVV/1M

TVV/1M is a glass optical fiber RS485 repeater, with a low voltage supply. It consists of a glass fiber-optic master section with a screw-type connector and an electrical section with an RS485 output. It can be used to extend the transmission distance of a serial communication or to isolate network branches. It can be mounted on a control panel with a 35 mm DIN rail and is very compact, as it occupies only 2 modules.

The glass optical fiber RS485 repeater accepts a wide range of low-voltage AC and DC power supplies; it is fully Plug & Play and requires no drivers or DIP switches. This repeater operates in half-duplex mode and automatically detects data direction and transmission speeds up to 250 kbps, making it easy to install in any new or existing system.

Working principle

TVV/1M glass optical fiber RS485 repeater consists of a master optical section, where the received signal is retransmitted by the slave optical section. The signal is simultaneously converted and transmitted by the RS485 electrical slave section. The response packets received from the slave optical terminals are retransmitted to the master terminals. However, these packets are not converted by the RS485 electrical slave section.

In an installation, it is good practice to install a converter at the beginning of a multi-mode fiber run and an glass optical fiber RS485 repeater such as the TVV/1M on each floor. This helps reduce issues related to ground potential differences or possible power supply voltage spikes. Optical fiber is a perfect electrical insulator and therefore protects the RS485 bus from the propagation of lightning strikes or other atmospheric discharges.

Optical fiber isolates various branches of a network (such as the floors of a hotel or sections of a photovoltaic system) from electromagnetic interference (EMI) and power surges. Electromagnetic interference is common in these environments; therefore, it is good practice to install two or more optical-to-electrical converters to ensure signal integrity.

Furthermore, a glass optical fiber RS485 repeater allows for the regeneration of the electrical signal, thereby improving communication quality.

Use cases

A glass optical fiber RS485 repeater is typically used to integrate multi-mode optical fiber segments into an RS485 serial bus network. There are also environments where electrical equipment is prohibited, such as swimming pools, saunas, and buildings at risk of fire, where optical fiber therefore becomes necessary.

The transmission speed is certainly higher than synthetic fiber, but both are still more than sufficient for the few Mbps required in industrial applications. In building automation, controlling modules on an RS485 bus requires a few hundred kbps, and glass optical fiber is definitely recommended for isolating different zones of a system.

Protocol

TVV/1M glass optical fiber RS485 repeater is completely independent of the protocol used. This means that the repeater is transparent to the communication and can be used with protocols such as Modbus, BACnet, or any proprietary protocol.

This is possible because the repeater operates on electrical levels rather than at the protocol level itself. Therefore, this glass optical fiber RS485 repeater can also be used in complex networks where multiple protocols are present simultaneously on the same RS485 bus.

Installation

Glass optical fiber undoubtedly performs better than synthetic optical fiber, but it is usually more expensive and more complicated to install. It requires termination at both ends, and specialized tools must be used for this operation. Once terminated, however, the bayonet connector is clearly easy to use.

For these reasons, glass optical fiber is often used only as a backbone for communication, while plastic optical fiber (POF) is preferred for shorter runs because it is easier to install.

Versatility

TVV/1M glass optical fiber RS485 repeater is also available with other combinations of serial standards and optical fiber, or as a simple converter. The TSS/1M and TQQ/1M repeaters, for example, accept synthetic optical fiber with screw or VersaLink connector, respectively. The TVV/1F and TVV/1R, on the other hand, are suitable for various serial standards, namely RS422 and RS232.

CMM/1V industrial serial converter can be used to terminate an optical bus. All combinations of serial standards, fiber optics, and power supply are available in the catalog; however, special requests (such as higher speeds) can be made via the contact form.