With the considerable cost and performance advantages of fiber, in theory every network would have a completely fiber horizontal structure running from a fiber port on a data center switch to a fiber port on a PC. But in practice, copper is often installed simply because it is more familiar. Plus, many network devices have copper ports, and organizations cannot afford to replace the most expensive components (the electronics) of their networks to install fiber.
One simple and inexpensive solution is offered by the Media Converters. The media converter connects the Ethernet through an RJ-45 port to a fiber optic cable port (such as SC, ST, and LC) fiber connections. This connection retains the collision domain between the two Ethernet participants and means that status transparency exchanges between the two Ethernet interfaces. The port status multi-mode glass fibers allow distances of up to 5,000 m to be bridged without intermediate repeaters. Single-mode fibers can be used over distances of up to 40 km. Network backbone and long-distance applications have long taken advantage of fiber optic cable. However, horizontal fiber cabling has been widely regarded as impractical and too expensive for an application that doesn’t need to cover long distances or move vast amounts of data. Fiber is regarded as expensive and difficult to install while copper is still the dominant cable type in local networks. But times have changed and fiber is gaining an edge over copper, especially for new installations, and is now often the first choice even for horizontal cabling, which has traditionally been copper.
Media converters are the key to integrating fiber into a copper infrastructure, making it possible to migrate a local network to fiber while extending the productive life of existing infrastructure. On the most basic level, media converters are simple networking devices that make it possible to connect two dissimilar media types. Although the most common type of media converter connects UTP to fiber optic cable, media converters may also connect other cable types such as coax. Media converters are often used to connect legacy Ethernet equipment with copper ports to new fiber cabling. The converters may also be used in pairs to insert a fiber segment into a copper network to increase cabling distance.
Media converters may be simple devices, but they come in a dizzying array of types. Newer media converters are often really a switch, which confuses the issue even more. Ethernet media converters are available in many configurations, with the most common being UTP to multi-mode or single-mode fiber, although UTP to thin coax (thinnet), UTP to thick coax (standard Ethernet), thin coax to fiber, and UTP to SFP are also available. On the copper side, most media converters have an RJ-45 connector for 10BASE- T, 100BASE-T, and 1000BASE-T connectivity. The fiber side usually has a pair of SC or ST connectors, although newer compact connectors such as LC and MT-RJ are becoming increasingly common. Here is a 10/100/1000Base-TX to 1000Base-FX Media Converter in the picture below.
Media converters may support network speeds from 10 Mbps to 10 Gbps, thus there are Fast Ethernet media converters, Gigabit Ethernet media converters, and 10-Gigabit Ethernet media converters. Traditional media converters are purely Layer 1 devices that only convert electrical signals and physical media and do not do anything to the data coming through the link so they are totally transparent to data. These converters have only two ports—one port for each media type—and support one speed. Some media converters are more advanced Layer 2 Ethernet devices that, like traditional media converters, provide Layer 1 electrical and physical conversion. But unlike traditional media converters, these converters also provide Layer 2 services—in other words, they are really switches. This kind of media converter often has more than two ports, enabling the user to extend two or more copper links across a single-fiber link. These media converters usually feature auto-sensing ports on the copper side, making them useful for linking segments operating at different speeds. The introduction of Layer 2 converters has blurred the line between media converters and switches. The same device may be called a media converter or a switch by different vendors.
Media converters are available in standalone models that convert between two different media types, in chassis-based models that connect many different media types in a single housing, and in hybrid systems that feature standalone modules that also work in a chassis.
Standard media converters come with an AC power supply that plugs into a standard wall outlet. It may be 120V AC for domestic U.S. power only or may be an auto-sensing 120 to 240V AC power supply that can be used domestically or easily converted to European power with a simple plug adapter. When media converters are used in areas that do not have convenient power outlets, they may be powered by Power over Ethernet (PoE), which provides power to network devices over the same Category 5 or higher UTP cable used for data. PoE Media Converters may also provide power through PoE to a PoE-powered device such as a security camera or wireless access point. (A Fast Ethernet PoE Media Converter is shown in the picture below.)
Small standalone media converters intended mainly for Fiber-To-The-Desk (FTTD) applications may be USB powered, enabling them to draw their power from a PC’s USB port. In chassis-based media converter systems, media converters or media converter modules draw their power from the chassis, which avoids the clutter of individual media converters that must be individually powered. Industrial media converters have demanding power requirements. Because the power supplied to industrial sites varies greatly, industrial media converters are either sold entirely separately from their power supply or are available with a choice of power supplies. Unlike standard networking devices, industrial media converters often require you to select the correct power supply for both device and application.
Industrial, or hardened, media converters are intended for use outdoors or in areas that may be exposed to temperature fluctuations, moisture, dirt, and EMI. Industrial Media Converters are rated for a specific temperature range. Temperature tolerances from –13 ° F to 140 ° F (–25 ° C to 60 ° C) are common, and some media converters are rated for extreme temperatures from –40 ° F to 167 ° F (–40 ° C to 75 ° C). These media converters are usually housed in hardened metal cases that are sealed against contaminants including particulates such as airborne dust, moisture, and sometimes chemicals. Conformal coating is a special film or coating applied to electronic circuitry to provide additional protection from contaminants. Industrial media converters are often designed to be DIN rail mounted or have separate brackets for DIN rail mounting. The media converters for industrial applications are usually built to withstand higher EMI than those intended for office or data center use.
When a network device such a switch detects that a link is broken, the Link indicator on its front panel goes out, alerting the network administrator that the connection is lost. The situation becomes a bit more complicated, however, when the switch has a media converter between it and its primary link. In this case, the switch can detect that the link to the media converter is broken but can’t detect a broken link on the other side of the media converter. If the fiber link goes down, the switch does not notice because it still “sees” the media converter.
To counteract this problem, media converters commonly have a feature called link loss pass through, which simply means that the media converter passes the news of a broken link onward. In other words, when either a twisted-pair or a fiber link is broken, the information about this link loss is transferred to the other media link.
Fiber is already established for LAN backbone applications, and now fiber is making inroads in horizontal cabling. Fiber carries more data than copper, making it more suitable for high throughput applications such as streaming media and VoIP. Additionally, as the price of copper rises, the price of installing fiber continues to fall, making it an economical choice as well. Copper-to-fiber media converters help to ease the financial shock of migrating network equipment to fiber. These media converters are a simple, inexpensive solution for matching copper ports to fiber infrastructure. From the data center to the desktop, from the central office to the home, media converters are bringing fiber connectivity to areas where copper has long been the medium of choice.
In the data center, media converters extend the productive life of existing copper-based switches, providing a gradual migration path from copper to fiber. Chassis-based media converters mount in racks alongside network switches, enabling the conversion of copper ports on legacy switches to fiber. Media converters can also be used with new copper switches that have fixed RJ-45 ports, which are significantly less expensive than the equivalent fiber switches. Here, network managers can convert only selected copper ports for multi-mode or single-mode fiber as needed, bringing versatility to the data center while bringing overall costs down.
But factors stand in the way of migrating copper infrastructure to fiber. First of all, there is the familiarity factor; if an IT staff is familiar with copper, they are likely to continue to install copper even if copper is not the best choice. Another major factor preventing the migration to fiber is the cost of changing network devices out for fiber versions. An enterprise switch is a major investment, and there is also the cost of adding fiber Network Interface Cards (NICs) to desktop PCs as well as other networked devices such as printers and wireless access points.