Fiber Cables Explained!
Selecting the correct Fiber Optic cable for your data center or network can be challenging. There are a several factor to consider before making a purchase: Fiber Count, Fiber Type, Jacket Rating, Connector Type and Polarity method. Luckily, C2G put all the information you need in 1 quick and easy blog post!
Fiber Trunk Cable Types
There are four main cable types that are prevalent for data center and LAN applications:
Selecting the correct cable will depend on the application. Tight buffered distribution and indoor/outdoor cables are typically used in various LAN installations, commercial office spaces and campus environments. They are typically field terminated with discrete connectors like the LC or SC connectors.
The micro array data center loose tube cable works well in data center and SAN applications. Their small diameter allows for denser fiber routing than traditional tight buffered cables.
Loose tube indoor/outdoor dry block sub-unitized cables can be terminated with MTP/MPO connectors. These cables are ideal for campus environments, private networks and local area networks because they can be run indoor and outdoor; without any additional components or installation.
Tight Buffered Distribution cable is a great choice for LANs, including commercial buildings, and is commonly used as the intra-building backbone and cabling from the service entrance to telco closets. It can be used as an inter-building backbone, as long as it is installed in a conduit, since it is not specifically rated as an outdoor cable. Tight buffered cables are typically not used with MTP/MPO connectors. These would be pre-terminated at the factory since MTP/MPO connectors are not easily field-terminated.
Indoor/Outdoor sunlight resistant tight buffer plenum optical fiber cables are ideally suited for installations that require partial or complete routing of pathways outside the building. The tight buffer design of these indoor/outdoor cables eliminates the need for breakout kits and/or other special termination equipment associated with loose tube cables. The outer jacket is comprised of a rugged UL listed sunlight resistant polymer that allows the cable to be exposed to direct sunlight without the concern for material jacket degradation.
Trunk Cable Fiber Type Options
The selection of the type of fiber used in pre-terminated cabling systems is most often based on the applications that will be supported. The most common types are 3 multimode fiber options and 2 single mode options. Although there are new fibers being developed, such as wide band multimode fiber (WBMMF)
Multimode fiber is typically used in LAN applications and short haul data centers, both backbone and horizontal. Single-mode fiber is typically used in long-haul applications but is also common in SANs, PON/POLs and today’s emerging mega data centers.
OM1 fiber is a 62.5µm core multimode fiber that will support 1Gb/s up to 275 m at 850nm or 550 m at 1300nm. Since OM1 supports 10G up to only 33m at 850nm wavelengths, which is the most common application, any network that will need to support applications above 1G/s should use OM3 or OM4 fibers.
OM3 and OM4 are both 50 µm core laser optimized multimode fibers (LOMF). Both have the same cable attenuation but vary in bandwidth (see the top table). Although both OM3 and OM4 support 10G and 40/100G for at least 100 meters, because of its better bandwidth, OM4 supports each application at longer distances as shown at the bottom of chart.
There are basically two options for single mode fibers OS1/OS2 or OS2 (ITU G.657.A1). The first, OS1/OS2, is listed with both general types of single mode because the type of fiber will be determined by the type of cable that is selected. If a tight-buffered single mode cable is selected, then the fiber will meet OS1 specifications. If a loose-tube single mode cable is selected, the fiber will meet OS2 specifications. OS2 is the better grade of single mode fiber and has a low attenuation coefficient in the around 1383 nm wavelength window. OS2 will have an attenuation (loss) of 0.4 dB/Km and OS1 has an attenuation of 0.7 dB/Km. OS2 (ITU G.657.A1) grade is often used in passive optical network applications.
Trunk Cable Connector Design Options
There are many options for fiber optic connector styles. This includes the options for end-face polish of the ferrule tips on the connectors themselves. A PC type (physical contact or polished convex connector) is the “standard” polish for Multimode fiberconnectors that have radius end-face on the ferrule tip. The physical contact of the actual glass fiber cores using these connectors helps to eliminate the air gap between mated connectors thereby decreasing the insertion loss and reflections at a mated pair interface.
A UPC (ultra polish connector) is a better quality radius polish than the PC polish with even less back reflection. APC is an (angle polish) which is the ultimate in reduced reflections at a connector mated pair interface. UPC and APC polished connectors are commonly used for Single-mode fiber applications to reduce the reflections back at the laser light source which can cause noise in the transmitted communication signals.
MPO style connectors are multi-fiber array (or ribbon) connectors that have been adopted for parallel optical fiber transmission or for high density connections in data center applications. Typically, these connectors are used with 12 fibers in one plug (8 fiber base applications leave the four middle positions un-terminated/unused). Recently, 24 fiber MPO connectors are being employed for higher channel capacity links at 40 gigabits/sec and 100 gigabit per second.
MPO connectors will be either male or female (pinned vs. unpinned) and an end-face ferrule polish of PC or APC. APC polish is used with single-mode MPO connectors and a PC polish is typical for multimode MPO connectors
Discrete (single fiber ferrule) connectors are most often LC, SC and ST connector types. The LC is a “small form factor” connector that is available in a duplex uniboot footprint (2 connectors joined together), a simplex footprint and a reconfigurable duplex uniboot footprint so that the two connectors can be repositioned to alter the A-B (transmit/receive) polarity in the field. A duplex uniboot LC connector takes up about the same physical space as a simplex SC connector. These connectors can also be polished with PC, UPC or APC type polishes depending on the application requirements.
The ST simplex connector is an older bayonet style connector with either a PC or UPC polish.
The choice of connector is dependent on the application. MPO, LC and SC connectors are recognized in the TIA standards for new installations and ST is recognized for legacy installs.