Fiber Optic Terms Explained: Cable, Connectors and Transceivers

Fiber with a 9 micron core that carries one path of light, so it runs for kilometers with low loss. OS2 is the low water peak grade used for outside plant and long links. OS1 is the older indoor grade.

Fiber with a 50 micron core for short links inside buildings and data centers. OM4 carries 100G SR4 links up to 100 meters, against 70 meters on OM3. OM5 adds support for several wavelengths on one fiber.

The ITU-T standard for ordinary single-mode fiber with low water peak. It is the default glass in most outside plant cable.

Bend-insensitive single-mode fiber. G.657A1 is rated to a 10mm bend radius, A2 to 7.5mm and B3 to 5mm. The A grades splice to G.652D without issue, which is why A1 and A2 are common in drop, indoor and high count ribbon cable.

Fibers sit loose inside buffer tubes, which are gel-filled or dry-blocked, so the cable can stretch and change temperature without stressing the glass. The standard build for outdoor duct, burial and aerial routes.

Fibers are bonded side by side in ribbons of 12 or 16, so a mass fusion splicer joins a whole ribbon at once instead of one fiber at a time.

Ribbon bonded only at intervals, so it can roll up into a bundle. It packs more fibers into a smaller cable and still mass fusion splices. At 20mm OD, flat ribbon carries 432F and rollable carries 864F.

Usually 864 fibers and above in one cable. Cloud and colocation routes run 864F to 1728F, and hyperscale campuses run 3,456F to 6912F.

All-dielectric self-supporting aerial cable. It carries its own weight between poles with no messenger wire and no metal, so it can hang near power lines.

Aerial cable with a steel messenger wire built into the jacket, so in cross section it looks like the number 8.

Small diameter cable that is blown into microduct with compressed air instead of being pulled. More fiber can be added later by blowing new cable into spare ducts.

The last link from the street to a home or business in an FTTH network, often a flat cable with 1 to 12 fibers.

All-dielectric cable has no metal, so it needs no grounding and is safe near power. Armored cable adds a steel or dielectric layer against rodents and crushing.

Optical fiber nonconductive plenum. The highest indoor fire rating under the NEC, required in air-handling spaces such as ceiling voids. OFNP can be used wherever OFNR is allowed, but not the other way round.

Optical fiber nonconductive riser. Rated for vertical runs between floors, but not for plenum spaces.

Low smoke zero halogen jacket. It gives off little smoke and no corrosive halogen gas in a fire, and is the common indoor standard outside North America.

The two most common single-fiber connectors. LC uses a 1.25mm ferrule and is the standard in switches and patch panels. SC uses a 2.5mm ferrule with a push-pull body.

The polish on a connector end face. APC is angled at 8 degrees and is usually green, which cuts back reflection and is why it is used in FTTH and PON. UPC is flat and usually blue. The two do not mate with each other.

Multi-fiber connectors that terminate 8, 12, 16 or 24 fibers in one plug, used for data center trunks and 400G and 800G links. MTP is a branded, higher-spec version of MPO, and the two intermate.

How fiber positions are mapped from one end of an MPO trunk to the other, so each transmitter reaches a receiver. The type must match the cassettes and patch cords on the link.

A trunk is a factory-terminated multi-fiber cable between panels. A harness breaks an MPO out to single-fiber connectors such as LC. A cassette does the same inside a panel.

A sealed, weatherproof connector for outdoor FTTH terminals, so drops can be plugged in without splicing in the field.

Joining two fibers by melting them together with an electric arc. Mass fusion splicing joins a whole ribbon of 12 or 16 fibers in one pass.

The module that turns electrical signals in a switch or network card into light on the fiber and back again. It is the active part of the optical path, at the very end of each link.

Transceiver form factors, roughly in order of speed. SFP and SFP28 carry 1G to 25G, QSFP28 carries 100G, QSFP-DD and OSFP carry 400G and 800G, and OSFP carries 1.6T.

Cables with the modules built on. An active optical cable (AOC) uses fiber for runs of up to around 100 meters. A direct attach copper cable (DAC) is cheaper but only reaches a few meters.

Any cable that runs outdoors: in duct, direct buried or aerial on poles. OSP cable is built for water, temperature swings and pulling loads.

Fiber to the home, usually built as a passive optical network (PON), where one fiber from the central office is split to serve many homes.

Fiber that is installed but not lit by any equipment. Buyers lease or buy it and light it with their own transceivers.

Cable made to your count, fiber type and jacket after the order is placed, rather than pulled from fixed stock. It is how most high count and specialty cable is supplied.