• Micon Automation Systems Private Limited

Multi-Mode Fibre Optic Modem, 277mm

Micon Automation Systems offers a Multi-Mode Fibre Optic Modem, Model 277MM, designed to provide the most versatile connection possible between any asynchronous serial equipment using fibre optic cable. It allows any two pieces of asynchronous serial equipment to communicate full or half-duplex over two fibres at typical distances up to 2.5 miles. The converter can also be set up in "repeater" mode to create a multi-drop master/slave configuration, allowing one serial device to talk to multiple slave devices around a fibre ring. RS-232 data signals at up to 115.2K bps and RS-422, or RS-485 data signals at up to 115.2K bps are supported. Different standards can be mixed and matched to allow RS-232 devices to connect to your RS-422 or RS-485 system. This means the Model 277MM can replace converters and isolators when connecting remote devices, while providing the EMI/RFI and transient immunity of optical fibre. The modem supports both the transmit and receive data lines, and provides full hardware control of the RS-422/485 driver with automatic Send Data Control circuit. Timeouts are dip-switch selectable between 0.10 and 2.2 ms. All serial connections are provided on the same DB-25 female connector, while the multimode fibre is connected via two ST connectors. The unit is powered by 9 V DC at 140 mA max. The most important consideration in planning the fibre optic link is the “power budget” of the fibre modem. This value represents the amount of loss in dB that can be present in the link between the two modems before the units fail to perform properly. This value includes line attenuation as well as connector loss. For this model the typical connector-to-connector power budget is 12.1 dB. Because 62.5/125 µm cable typically has a line attenuation of 3 dB per km at 820 nm, the 12.1 db power budget translates into 2.5 miles. This assumes no extra connectors or splices in the link. Each extra connection would typically add 0.5 dB of loss, reducing the possible distance by 166 m (547 ft). The actual loss should be measured before assuming distances.