CMM/1S is a RS485 synthetic optical fiber converter that converts RS485 electrical serial bus standard to plastic optical fiber with a screw-type connector. 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 it’s very compact, only 1 DIN module.

CMM/1S RS485 synthetic optical fiber converter accepts a wide range of low-voltage AC and DC power supplies; it is fully Plug & Play and requires no drivers or DIP switches. The RS485 serial interface 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.

Use cases

A RS485 synthetic optical fiber converter is typically used to integrate multi-mode optical fiber links 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 fiber optics therefore become necessary.

The transmission speed is certainly more limited than glass fiber, but it is 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 synthetic optical fiber is definitely recommended for isolating different zones of a system.

Advantages

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

Fiber optics isolate 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, so it is good practice to install two or more optical-to-electrical converters to ensure signal integrity.

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

Protocol

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

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

Ease of installation

Multi-mode synthetic optical fiber has several advantages over glass fiber; for example, it is more economical and easier to install. It does not need to be terminated; simply use a sharp utility knife to make a clean cut at the ends.

The maximum recommended transmission distance for synthetic optical fiber is 100 m. As long as you stay within these specifications, use good-quality plastic optical fiber, and maintain appropriate bend radius, simply cut the fiber as indicated. Then simply insert the fiber into the adapter and gently screw the connector on with your fingers, no special tools are needed. There’s no need to over-tighten the connectors, as this risks breaking them or damaging the fiber. This speeds up installation and maintenance, which can even be performed by non-specialized personnel.

In more challenging situations, where a few extra meters can make a difference, or where the fiber is not of the highest quality, additional steps may be necessary to minimize insertion loss. You can polish the ends with fine-grit sandpaper, although this is not necessary in the vast majority of cases.

Versatility

The RS485 synthetic optical fiber converter is available with other combinations of serial and fiber optic standards, or with a 230 V power supply. The CMM/1V and CMM/1Q converters, for example, accept glass fiber with a bayonet connector or synthetic fiber with a Versatile Link connector, respectively. The CRM/1S and CFM/1S, on the other hand, are suitable for various serial standards, namely RS232 and RS422.

The CMP/1S  RS485 synthetic optical fiber converter is functionally identical to CMM/1S but operates on 230 V AC. All combinations of serial standards, optical fiber types, and power supply options are available in the catalog; however, special requests (such as higher data rates) can be made via the contact form.

Main features

RS485

Screw

Mechanical features

Working conditions