ACables & Construction
ADSS Cable
All-Dielectric Self-Supporting aerial cable — no metal, so it can be strung on power-line towers without grounding. Span and sag are set by the cable’s aramid strength members.
Knowledge Base
Fiber optics glossary,A to Z.
Every acronym, rating, and unit that turns up in a fiber datasheet or quote — defined in a sentence or two. Filter by topic, or jump to a letter.
A–Z
Showing 39 of 39 terms
AConnectors & Termination
APC (Angled Physical Contact)
A connector polish with an 8° angled end-face that reflects stray light into the cladding instead of back down the core. Identified by a green body; standard for PON and CATV links.
ACables & Construction
Armored Fiber Cable
Cable with a steel or aluminum tape (or interlocking metal) layer under the jacket to resist rodents, crush, and direct-burial stress.
AFiber & Optics
Attenuation
The loss of optical power as light travels along a fiber, measured in dB/km. Modern single mode fiber attenuates roughly 0.35 dB/km at 1310 nm and 0.20 dB/km at 1550 nm.
BFiber & Optics
Bend-Insensitive Fiber (G.657)
Single mode fiber engineered to keep light in the core at tight bend radii — down to 7.5 mm or even 5 mm for G.657.B grades. The default choice for FTTH drops and indoor routing.
BCables & Construction
Breakout / Fan-Out Cable
A multi-fiber cable in which each fiber has its own jacketed sub-unit, so individual legs can be terminated and handled directly without splice trays.
CFiber & Optics
Cladding
The glass layer surrounding the fiber core, with a slightly lower refractive index. The index step traps light in the core by total internal reflection. Standard outer diameter is 125 µm.
CStandards & Safety
CPR Euroclass
The EU Construction Products Regulation fire rating for cables installed in buildings, from Aca (best) to Fca. Most commercial fiber installs in Europe require Cca or Dca with smoke/droplet sub-classes.
DFiber & Optics
dB & dBm
dB expresses a power ratio (loss or gain); dBm expresses absolute power referenced to 1 mW. A link budget subtracts dB losses from a transmitter’s dBm output to check the receiver still gets enough light.
DFTTH & PON
Drop Cable
The final cable from a distribution point into the subscriber’s premises. FTTH drops are typically flat 1–4 fiber cables with G.657 bend-insensitive fiber and a steel or FRP strength member.
FConnectors & Termination
Ferrule
The precision ceramic (zirconia) cylinder inside a connector that holds the fiber and aligns it against the mating connector. End-face geometry of the ferrule determines insertion and return loss.
FFTTH & PON
FTTH / FTTx
Fiber To The Home, and the umbrella FTTx family (FTTB building, FTTC curb, FTTR room). Describes how deep the fiber reaches toward the end user before copper or wireless takes over.
FConnectors & Termination
Fusion Splicing
Joining two fibers by melting them together with an electric arc. Typical loss is under 0.05 dB — lower and more reliable than any connector, at the cost of needing a splicer in the field.
GFTTH & PON
GPON
Gigabit Passive Optical Network (ITU-T G.984): 2.5 Gbps down / 1.25 Gbps up shared across up to 128 users via passive splitters. The workhorse of FTTH; XGS-PON is its 10 Gbps successor.
IFiber & Optics
Insertion Loss
The optical power lost when a component (connector, splice, splitter) is inserted into a link, in dB. A good connector pair adds ≤ 0.3 dB; every link budget is a sum of insertion losses.
IStandards & Safety
IP Rating (IP68)
Ingress Protection code for enclosures: first digit dust, second digit water. IP68 — dust-tight and continuously submersible — is the benchmark for outdoor closures and terminal boxes.
LConnectors & Termination
LC Connector
A small-form-factor connector with a 1.25 mm ferrule and latching tab. Its density made it the default on transceivers, patch panels, and data center equipment.
LCables & Construction
Loose Tube Construction
Cable design where fibers float in gel- or dry-filled buffer tubes, isolating them from tension and temperature swings. The standard for outdoor and high-count cables.
LStandards & Safety
LSZH (Low Smoke Zero Halogen)
A jacket compound that emits minimal smoke and no halogen acids when burning. Required in confined public spaces — tunnels, transit, offices — across most of Europe and Asia.
MData Center
MPO / MTP Connector
A multi-fiber push-on connector terminating 12, 16, or 24 fibers in one rectangular ferrule. MTP is US Conec’s premium MPO. The backbone of 40G/100G/400G data center trunks.
MData Center
MPO Polarity (Type A / B / C)
The fiber-position mapping through an MPO link that ensures each transmitter meets a receiver. Type A is straight-through, Type B reversed, Type C pair-flipped — mixing methods mid-link breaks the channel.
MFiber & Optics
Multimode Fiber (MMF)
Fiber with a 50 µm (or legacy 62.5 µm) core that carries many light modes. Cheap to drive with VCSELs but distance-limited by modal dispersion — the short-reach choice inside buildings and data centers.
OFTTH & PON
OLT (Optical Line Terminal)
The operator-side PON equipment in the central office or cabinet. One OLT port feeds a splitter tree serving dozens of subscribers’ ONTs.
OFiber & Optics
OM1–OM5 Ratings
ISO grades of multimode fiber. OM3 (300 m at 10G) and OM4 (400 m at 10G, 150 m at 40/100G) dominate today; OM5 adds wavelength-division support for SWDM. OM1/OM2 are legacy.
OFTTH & PON
ONT / ONU
The subscriber-side PON terminal that converts fiber to Ethernet/Wi-Fi. ONT and ONU are used near-interchangeably; ONT typically means the single-user device in the home.
OCables & Construction
OPGW
Optical Ground Wire — a grounded shield wire for high-voltage transmission lines with optical fibers inside. Does double duty: lightning protection for the power line, backbone capacity for the utility.
OFTTH & PON
Optical Splitter (PLC)
A passive component that divides one input across N outputs (1:2 to 1:128). Planar Lightwave Circuit splitters give uniform loss per branch — about 10·log₁₀(N) dB plus excess loss.
OFiber & Optics
OS2 Fiber
The ISO cabling grade for low-water-peak single mode fiber (ITU-T G.652.D), specified at ≤ 0.4 dB/km. What you should assume when a datasheet just says "single mode".
PConnectors & Termination
Patch Cord
A short factory-terminated jumper with connectors on both ends, used between panels and equipment. Factory polish and testing give consistently lower loss than field termination.
PConnectors & Termination
Pigtail
A short fiber with a factory connector on one end and bare fiber on the other, fusion-spliced onto incoming cable inside trays — combining factory-grade end-faces with splice-grade joints.
PStandards & Safety
Plenum Rating (OFNP)
The strictest NEC flame rating for cable run through air-handling spaces in North American buildings. OFNP cable can replace riser (OFNR) cable, never the reverse.
RFiber & Optics
Return Loss
How much light a component reflects back toward the source, in dB — higher is better. UPC connectors achieve ≥ 50 dB; APC ≥ 60 dB, which is why analog and PON systems specify APC.
SConnectors & Termination
SC Connector
A square push-pull connector with a 2.5 mm ferrule. Rugged and cheap to terminate, it remains the default on FTTH ONTs, splitter ports, and wall outlets.
SFiber & Optics
Single Mode Fiber (SMF)
Fiber with a ~9 µm core that carries one light mode, eliminating modal dispersion. Reaches from kilometers to oceans; G.652.D is the universal grade, G.657 its bend-tolerant cousin.
SFTTH & PON
Split Ratio
How many subscribers share one PON port via splitters — 1:32 and 1:64 are common. Each doubling of the ratio costs ~3 dB of optical budget and divides peak bandwidth.
TStandards & Safety
TIA-598 Color Code
The 12-color sequence (blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, aqua) identifying fibers and tubes by position. Counts above 12 repeat with stripes or ring marks.
TCables & Construction
Tight-Buffered Cable
Construction where each fiber gets a 900 µm plastic coating bonded directly to it — easier to strip and terminate, the standard for indoor and patch cable.
UConnectors & Termination
UPC (Ultra Physical Contact)
A dome-polished flat-contact connector end-face, identified by a blue body. The general-purpose polish for Ethernet and data center links; use APC where reflections matter.
WFiber & Optics
Wavelength (850 / 1310 / 1550 nm)
The operating "color" of light in a link. 850 nm drives multimode; 1310 nm offers zero dispersion and 1550 nm minimum attenuation on single mode — PON stacks up/downstream on separate wavelengths.
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