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Overcoming OM3 Performance Challenges

Jul 1st 2015 at 9:00 PM

10 Gigabit Ethernet (10GbE) introduces a challenging 2.6 dB insertion loss limit on OM3 fiber cabling. This tight limit has led some industry observers to suggest it’s not possible to meet the standard using regular, as opposed to low-loss, MTP cassettes. These observers have also suggested it’s not possible to run fiber cabling the full 300-meter distance specified in the 10GBASE-S standard when using MTP cassettes, whether standard or low-loss.

To test these assumptions, Leviton contracted with Intertek Testing Services (ETL) to perform benchmark testing of OM3 fiber system performance. The testing proved that the 10GBASE-S standards can easily be met with the latest generation of OM3 fiber systems using standard MTP cassettes and up to the full 300-meter length limit. In addition, the results show that Fiberstore’s OM3 system will support future migration to 40GbE/100GbE applications. We can offer you different types of OM3 fiber, such OM3 MTP LC fiber patch cable, OM3 LC SC fiber optic cable, OM3 ST fiber patch cable, ect.

Multimode Fiber – Standards, Applications, and Challenges

For many years 62.5/125 μm (OM1) and conventional 50/125 μm (OM2) multi-mode fiber have dominated shorter distance communication applications, such as within a building or on a single-site campus. The fibers easily support applications ranging from 10 Megabit Ethernet (MbE) to Gigabit Ethernet (GbE). Their relatively large core sizes simplify connections and are ideal for use with low cost light-emitting diode (LED) transmitters.

With the introduction of, and demand for, 10 Gigabit Ethernet (10GbE), typical in data centers, the physical limitations and properties of multimode optical fiber are being severely tested. Multimode fiber provides many allowable paths for light to travel down the fiber, and due to intermodal dispersion not all pulses arrive at the destination simultaneously. This characteristic, as well as other issues, ruled out the use of OM1 and OM2 fiber with 10GbE.

To address this, the Institute of Electric and Electronic Engineers (IEEE) created the 10GBASE-S (the S stands for short wavelength) multimode fiber specification with the goal of providing 10GbE operating distances of 300 meters. Laser-optimized OM3 fiber was specified in TIA-492AAAC to support both the IEEE standard and economical vertical cavity surface emitting lasers (VCSELs) that operate at the 850 nm and 1300 nm wavelengths. Fiber that meets the standards delivers an effective modal bandwidth of 2000 MHz*km at the 300 meter distance.

The TIA-568-C.0 standard allows for a maximum 2.6 dB insertion loss and 300 meter length with OM3 fiber cabling systems. While manufacturers frequently submit their copper cables for third-party testing to verify performance that meets or exceeds applicable standards, they typically have not had fiber cabling systems, including OM3, tested. As a result, designers and operators of OM3 fiber networks are uncertain what the true parameters are in designing premises applications. 10G OM3 Patch Cables provide sufficient bandwidth to support 10 Gigabit Ethernet up to 300 meters via 50/125µm laser-optimized OM3 fiber, which is 5 times faster than standard 50/125µm OM2 fiber. The 10G OM3 fiber patch cables work with both VCSEL laser and LED sources. Here, Fiberstore offers 10G OM3 fiber patch cables terminated with different fiber optic connectors (LC/SC/ST/FC/MTRJ/MU/E2000/SMA). These cables can be Simplex or Duplex and Customized in optional lengths. Such as 10G OM3 LC multimode fiber patch cable, OM3 LC SC fiber patch cable, OM3 ST SC fiber patch cable, ect.

For example, the maximum insertion loss for MTP-LC cassettes or modules as stated in the TIA specification is 1.5 dB, as shown in Figure A below. An unusually complicated (but not extreme) configuration might consist of four cassettes with a total of eight mated pairs. If each of these cassettes were at the headroom limit then the insertion loss at 6.0 dB would exceed the allowable limit. Some vendors have addressed this possibility by offering low-loss cassettes. However, these cassettes come at a considerable cost premium – approximately 50%.

Channels approaching the 300-meter maximum allowable distance for 10GbE have the same potential issue. Insertion loss for OM3 cable is typically 3.0 dB per kilometer. The TIA standard allows 0.75 dB insertion loss per connector mated pair. For example, a 300-meter channel configuration with six mated pairs could have a maximum insertion loss of 3.9 dB, well above the 2.6 dB limit. Undoubtedly, this explains why some vendors have recommended that users stay well below the 300-meter length limit.

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