Glass fiber is coated with a protective plastic covering called the “primary buffer coating” that protects it from moisture and other damage. More protection is provided by the “cable” which has the fibers and strength members inside an outer protective covering called a “jacket”. Most indoor fiber optic cables are tight buffer design, usually they consist of the following components:
So, based on these basic components, indoor fiber cables are available with following standard structures:
Tight Buffered Fiber features a secondary layer of coating applied directly to their initial 250mm layer(bare fiber). The second layer acts as reinforcement to the individual fibers and makes them easier to handle and terminate. Tight buffer fibers are indoor used or outdoor used in fiber enclosures.
Simplex Fiber Cable is a cable contains a single tight buffer fiber inside, and is used in applications that only require one-way data transmission. Simplex fibers are available in single-mode, multimode, laser optimized OM3, OM4 types.
Duplex Fiber Cable consist of two separate Tight buffer fibers. Duplex fiber cables are formatted in the ‘zipcord’ styling, where each fiber has independent coatings that are linked together with a thin layer of coating material. This design can allow for a duplex cable to be pulled apart and used as two simplex cables. Duplex is most used where require simultaneous, bi-directional data transmission, i.e. one fiber transmits in one direction while the other fiber transmits in the opposite direction.
Distribution Fiber Cable is usually bundles 2 to 24 fibers(tight buffered) into one cable jacket with only a single aramid strength member around all the fibers. For cable with 24 fiber or more, the tight buffer fibers will be bundled into subunits of 6 fibers, 8 fibers or 12 fibers, and each subunit with its own aramid yarns, then the subunits were bundled into total 24, 36, 48, 72, 96 or 144 fibers with taps and outer jacket. Distribution cables are popular indoor use cables in backbone cabling in dater centers, FTTH and are available plenum and riser rated.
Breakout Cables contains individual fiber with its own aramid strength aramid yarns and jacket. Beyond this, breakouts are known for their rugged and tough design, considerable crush resistance, and tensile strength. Because each fiber is reinforced, breakout cables allow users to “breakout” inner fibers directly at any point along the run and continue to route the remainder to another point.
To meet different installation environment, the cable jackets will be flame retardant and built with LSZH, riser(OFNR) or Plenum(OFNP) rated PVC materials.
Indoor Optical Fiber Cables are mainly used in building wiring applications. As patch cables, they could be installed in network racks, cabinet, patch panels, and other fiber enclosures. As backbone fiber cables, they could be installed in walls, between floors, in plenum air handling ducts and under data center floors.
For identification purposes, multimode fiber, and also singlemode fiber, is often referred to by its performance level identified by ISO/IEC (International Organization of Standards and International Electrotechnical Committee), which is based on the fibers bandwidth capabilities.
| Fiber Types and Typical Specifications
(OM/OS refers to TIA types, B refers to IEC types, G refers to ITU types)
|@850/1300 nm||@850/1300 nm|
|50/125 microns (OM2)||3/1 dB/km||500/500 MHz-km||Laser-rated for GbE LANs|
|50/125 microns (OM3)||3/1 dB/km||2000/500 MHz-km||Optimized for 850 nm VCSELs|
|50/125 microns (OM4)||3/1 dB/km||3600/500 MHz-km||Optimized for 850 nm VCSELs, higher speed|
|62.5/125 microns (OM1)||3/1 dB/km||160-200/500 MHz-km||LAN fiber|
|100/140 microns||3/1 dB/km||150/300 MHz-km||Obsolete|
|9/125 microns (OS1 B1.1 or G.652)||0.4/0.25 dB/km||HIGH!||Singlemode fiber, most common for Telco/CATV/high speed LANs|
|9/125 microns (OS2, B1.2 or G.652)||0.4/0.25 dB/km||HIGH!||Low water peak fiber|
|9/125 microns (B2 or G.653)||0.4/0.25 dB/km||HIGH!||Dispersion shifted fiber|
|9/125 microns (B1.2 or G.654)||0.4/0.25 dB/km||HIGH!||Cutoff shifted fiber|
|9/125 microns (B4 or G.654)||0.4/0.25 dB/km||HIGH!||Non-zero dispersion shifted fiber|
|@850 nm||@850 nm|
|200/240 microns||4-6 dB/km||50 MHz-km||Slow LANs & links|
|POF (plastic optical fiber)|
|@ 650 nm||@ 650 nm|
|1 mm||~ 1 dB/m||~5 MHz-km||Short Links & Cars|
OM3 fiber is designed to accommodate 10 Gigabit Ethernet up to 300 meters, and OM4 can accommodate it up to 550 meters. Therefore, many users are now choosing OM3 and OM4 over the other glass types. In fact, nearly 80% of 50 micron fiber sold is OM3 or OM4.
If you require higher data rates or plan on upgrading your network in the near future, laser optimized 50 micron (OM3 or OM4) would be the logical choice.