10 Gigabit Ethernet (IEEE 802.3ae) over optical fiber has made significant inroads in enterprise LANs and data centers. There are numerous physical-layer interconnects, defined by IEEE 802.3, available on the market to achieve 10Gbit/s data transmission over single-mode and laser-optimized multimode fibers, such as 10GBase-LR, 10GBase-ER, 10GBase-SR, and 10GBase-LRM, etc. With all these options, it can be a difficult process to sort through the requirements of a specific implementation. Today, I’d like to introduce an efficient 10G Ethernet multimode optical solution—10GBase-LRM.
In September 2006, the IEEE 802.3aq defined an interface—10GBase-LRM, which can help upgrade campus and building backbone links regardless of the fiber type already installed. 10GBase-LRM (long reach multimode) is a port type terminated with LC connector which can support the wavelength of 1310 nm at the speed rate of 10.3125Gbit/s. It achieves the link lengths of 220 m on standard fiber distribute data interface (FDDI) grade multimode fiber. To make sure that specifications are met over FDDI-grade, the transmitter should be coupled through a mode conditioning patch cord over OM1 and OM2 fibers, while OM3 and OM4 do not require. The following image shows Cisco SFP-10G-LRM.
Due to the adaptive equalization technology, also known as electronic dispersion compensation (EDC), 10GBase-LRM can cost-effectively provide a long-distance solution based on multimode fiber. EDC, which works on a way to offer a long-distance multimode solution that operates with a single wavelength, is deployed as an integrated circuit that acts like a complex filter on the received signal from the optical fiber. The purpose of EDC is to remove inter-sysmbol interference (ISI) that would normally make the incoming signal impossible to use, thus extending the maximum supportable distance.
At the first stage of standardization, 10G Ethernet standard defined two interfaces that can use multimode fiber (MMF), namely 10GBase-SR and 10GBase-LX4. Why does IEEE 802.3 define another MMF interface 10GBase-LRM? The following part will give an explanation.
- Distance: Only with high-bandwidth OM3 fiber, 10GBase-SR can achieve the length of up to 300 m. And with lower-bandwidth OM1 or OM2 fibers, 10GBase-SR can only be used in machine room for the interconnections between devices. However, 10GBase-LRM, depending on the EDC technology, can support the transmission distance of 220 meters over both OM1 and OM2 fibers, which makes it suitable for LAN networks within buildings.
- Cost: 10GBase-LRM devices cost less than 10GBase-LX4 equipment on many aspects. For example, 10GBase-LX4 relies on more complex and expensive coarse wavelength division multiplexing (CWDM) technology to support 300 m over three cable types, so it will cost more than other 10G solutions. Besides, 10GBase-LRM substitutes the low-cost silicon for the optical complexity of LX4 which greatly decreases the cost.
- Size: 10GBase-LX4 uses four lasers, laser drivers, four photodiodes and preamplifiers, making 10GBase-LX4 module a big size, while the 10GBase-LRM module, which uses the same optical component footprint as other 10G modules, is more compact.
As a preferable 10G solution for multimode fiber, 10GBase-LRM has attracted much industry attention and press. Based on the above content, we can have a better understanding of 10GBase-LRM and know why it is called as the ideal 10G solution for multimode fiber. Besides 10GBase-LRM transceiver, FS.COM provides various other types of 10GBase modules, like 10GBase-LR, 10GBase-ER, etc. Other compatible brands, such as Cisco, Brocade, Arista are also available here. If you have related requirement, please visit FS.COM.
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