• What is GMX?
• Who Uses GMX?
• How is GMX Deployed?
• GMX Links

What is GMX?
The MRV Gigabit Multimode Extender solution applies a unique technology that allows the transmission of high-speed signals over Multimode fibers to distances much longer than the standard.  Standard 802.3z Gigabit Ethernet, 1000-BaseSX, allows distances up to 550 meters.  With MRV's GMX technology, Gigabit Ethernet Multimode fiber-optic networks can extend up to 2km.  This allows for the use of high-speed backbone protocols over fibers that were originally used for FDDI rings.  The simplicity of the solution ensures new service benefits with a low-cost deployment and an efficient use of existing fiber infrastructure.  It also provides for a low-hassle upgrade to Gigabit Ethernet from an existing FDDI backbone.
 
The GMX technology also works at 100Mbps, extending to distances of up to 8km over Multimode fiber.  Typical 100Mbps distances are 2km over Multimode fiber.  This dramatically increases the available fiber plants that can be used to support 100Mbps Ethernet.
 
GMX technology can even be deployed in Wave-Division Multiplexing (WDM) environments.  MRV's FiberDriverT line of products includes 4- and 8-channel WDM systems providing up to 8Gbps full duplex bandwidth to a guaranteed distance of 2km over multimode cabling!
 
The technology works by a combination of active and passive components.  By coupling more optical power into the fiber, GMX technology raises the signal-to-noise ratio much higher than in typical Multimode fiber-optic links.  This improved signal strength in turn allows longer distances of fiber-optic cabling to be used.


Who Uses GMX?
GMX is primarily used where Multimode fiber is already installed.  In most cases, the fiber-optic plant was previously used for a lower-speed technology where the allowed distance over multimode cabling was higher.  In these cases, when upgrading to new, faster protocols, these fiber-optic cables would normally have to be replaced by expensive, single-mode cabling.  Worse yet, the cost of the optical transmission equipment for single-mode, even for a few kilometers, is much higher than for multimode solutions.  GMX comes to the rescue by providing a long distance extension capability without either changing the cabling plant or requiring high-cost single-mode optics.
 
GMX technology is often used to upgrade FDDI networks.  Many FDDI networks rely on the 2km distance over multimode cabling that FDDI allows.  When upgrading these networks to Gigabit Ethernet, the installer has previously had to change the cabling, which can be prohibitive.  With GMX technology, no change to the infrastructure is necessary.  The same multimode fiber that works with FDDI to 2km will also work with Gigabit Ethernet, using GMX, up to the same distance.  This capability greatly simplifies this common network upgrade, making it even more effective to switch to Gigabit Ethernet.
 
GMX technology is also deployed as a cost-savings method.  In many cases, for either 100Mbps or Gigabit Ethernet, the required distance is beyond the standard multimode cabling distance, but is not so much that high-power single-mode optics are required.  In these cases, GMX provides a very cost-effective bridge between short-distance multimode and long-distance single-mode options.


How is GMX Deployed?
GMX is deployed just like any other fiber-optic system.  The existing multimode cabling plugs into the GMX module of either the OptiSwitchT or FiberDriverT product.  The switch or media converter does all the work; GMX is plug-and-play.
 
When upgrading an FDDI network to Gigabit Ethernet, it is important to remember to use GMX modules in the OptiSwitchT chassis whenever links of greater than 550m are deployed.  Typically, FDDI networks operate as dual-redundant rings.  In this case, there are several options.  First, the administrator can use redundant Gigabit Ethernet modules for the OptiSwitchT, providing exactly the same functionality as FDDI.  Second, these redundant links could be used together with Link Aggregation to provide more bandwidth on the network backbone (using 2 fiber-pairs, up to 2Gbps of switched bandwidth would replace the 100Mbps of shared bandwidth using FDDI).  And finally, these extra links could be used for other network technologies as a parallel network backbone.


GMX Links

• OptiSwitchT and FiberDriverT Product Pages
• Using GMX to Upgrade FDDI to Gigabit Ethernet
• Extending the Life of Multimode Fiber