GDI FDM2-Fiber Hub / Fiber Optic Digital Modem


bulletFour Port Optical Star
bulletIntuitive Ring Status Display
bulletROS Memory System utilized to provide migration path
and upgradeability
bulletConfigurable Multiple Fiber Topology
bulletImmune to optical overloads
bulletKey-on-data (KOD) functionality

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The FDM2-Fiberhub is part of the Fiber Digital Modem series and provides active bi-directional, optical star communications to three optical ports. The FDM2-Fiberhubs can be ganged together either optically or electrically to provide further expansion. Two Auxiliary Data Ports are provided with full handshaking and Anti-Streaming capabilities. As with all FDM Series it shares the unique capabilities of being operated in many other topologies such as Point to Point, Daisy Chain and Dual Redundant Ring Formats. The  FDM2-Fiberhub is 100% compatible with all modems in the FDM Series, e.g. FDM1SA Stand Alone, FDM170 Plug-in for the 170 Controller and the FDM2070-6D Plug-in for the 2070 Controller.

A typical FDM2-Fiberhub application would be in a Daisy Chain or Dual Redundant Ring format at a point where two arterials, main and secondary intersect. The requirement here is to tie in the secondary optical branch  circuits into the main arterial fiber trunk. Another feature is the two Auxiliary Data Ports that can operate as a DTE or DCE with full handshaking. Connect one of these data ports into the local controller  plus add in another data branch circuit such as a Spread Spectrum Radio to bring in that orphaned controller on line.

The FDM2-Fiberhub represents a new generation of fiber optic modems utilizing a Replaceable Operating System. As ITS requirements change, or new features become available, a new ROS Memory System can be created so as to provide a Migration Path to upgrade the existing system.

When the FDM2-Fiberhub is operated in the DCRR format, it supports redundant communications paths, any single point of failure such as a modem failure or fiber cable cut, the system will automatically self heal around the point of failure making it the ideal choice for critical data communications.

Each modem has an Intuitive Ring Status Display that graphically mimics the switching status of the modem providing instant recognition as to the switching state of the modem and the ring system. Should a fold-back occur at a modem the display shows a pictorial view of the fold-back, its direction and all the other modems receive notification of this condition and flash the fold-back indication on their screens.

Automatic  Receive Fiber Identification will flash either a 1 or 2 to identify the Ring 1 or Ring 2 fiber.

 The Modem can operate over Multimode or Singlemode fibers, is immune to optical overloads and therefore does not require the insertion of optical attenuators. The modems ergonomic design has no internal adjustments and all connections, adjustable options and their labeling are on the external surfaces of the modem.

Activating the KOD function sets the FiberHub’s auxiliary data port(s) to act as a DTE device. Signals based on data received from the fiber system will generate an RTS handshake. This unique Key-On-Data capability is essential for communicating with a communications device that requires active RTS/CTS handshaking from a DTE device.

Anti-Streaming times are computer generated in precise, digitally programmed, 2 seconds increments starting from a base of 2 seconds to a maximum of 126 seconds to meet the demands for systems that require precise timing schemes.



Standalone Aux Data Port 1 DB9F Aux Data Port 2 RJ45 RS232/485/422

Data Rate Up to 115.2 Kbps (Asynchronous) Bit Error Rate Better than 1x10-9 within specified dynamic range MTBF In excess of 100,000 Hrs Control Lines RTS, CTS, KOD-RTS

Connectors ST, FC, SC
Dynamic Range 12db @ 1300nm MM. (Minimum) 24db @ 1310nm SM.


Anti-Streaming Clear (push button)

Note: The anti-streaming feature clears automatically when a normal condition returns but the ERROR indicator stays on until cleared manually with the front panel push button.

Daisy Chain Daisy Chain Configuration 2 Rings/1 Ring Ring configuration RS232/RS485 Data port operation selection RTS/CTS On/off CTS Delay time selection (0 or 8 ms) KOD RTS, Data Delay Anti-Streaming On/Off Anti-streaming Adjustable in 2 second increments from 2 to 126 seconds Data Rate Switch selectable 1200, 2400, 9600, 19200, 38400 56700, 115200 Bps Parity None, Odd, or Even

TX DATA Transmit RS232/485/422 RX DATA Received RS232/485/422 ANTI-STRM Anti–Streaming PWR DC Power FIBER STATUS Dual seven segment display


Stand Alone 2.306” W x 6.15” H x 8” D

Stand Alone 18-30 VDC

Optional External 115 VAC Supply External 220-240 VAC Battery Back-up (six hours)

Temperature -37 to +74o C Humidity 95% non-condensing


other Fiber Optic devices




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Contact     Bob Way 
Phone       916-783-1951 or 1-800-695-1951 
Fax           916-783-1952