Fiber Optics: Abbreviations, Acronyms and Terminology

Part 1: Fiber Types & Fundamentals

Optical Fiber (OFC): Thin strands of glass/plastic that guide light.

Mode: A single path for light to travel within the fiber.

Singlemode Fiber (SM / SMF): Fiber with a small core (~9µm) that allows only one mode of light. Used for long-distance, high-speed.

Multimode Fiber (MM / MMF): Fiber with a larger core (50 or 62.5µm) that allows multiple light modes. Used for short-distance.

• OM#: A classification (e.g., OM1-OM5) for MMF based on bandwidth and performance.

Step-Index Multimode Fiber: The first MMF design, now largely obsolete due to high dispersion.

Graded-Index Fiber: MMF where the core's refractive index decreases gradually, reducing modal dispersion.

Plastic Optical Fiber (POF): Large-core (~1mm) fiber used in short-distance consumer applications.

Core/Cladding/Coating/Jacket: The central light guide / outer optical layer / protective plastic layer / durable outer cable covering.

Mode Conditioning Cable: A patch cord used to launch singlemode signals into multimode fiber correctly.

Part 2: Network Architectures & Access (FTTX, PON)

Passive Optical Network (PON): A point-to-multipoint fiber network using passive splitters.

• GPON (Gigabit-capable PON): A predominant PON standard offering high-speed data, voice, and video.

Fiber to the X (FTTX): A generic term for fiber broadband deployment.

• FTTH / FTTB / FTTC / FTTN (Fiber to the Home / Building / Curb / Node): Defines how close the fiber gets to the end-user.
• FTTA (Fiber to the Antenna): Fiber used to connect cellular base station antennas.

Optical Line Terminal (OLT): The central office equipment in a PON that controls the network.

Optical Network Terminal / Unit (ONT / ONU): The customer-premises equipment in a PON that terminates the fiber.

LAN / WAN (Local / Wide Area Network): A network covering a small area / a large geographical area.

Part 3: Passive Components

Wavelength Division Multiplexer (WDM): A device that combines/separates multiple light wavelengths on one fiber.

• CWDM / DWDM (Coarse / Dense WDM): Uses wider / narrower channel spacing.

Coupler / Splitter: A device that splits optical power from one fiber to multiple fibers or combines it.

Fiber Distribution Panel (FDP) / Fiber Optic Panel (FOP): A panel for managing and interconnecting fiber cables.

Attenuator: A device that intentionally reduces signal power.

Part 4: Active Devices & Transceivers

Transceiver: A combined transmitter and receiver module.

• SFP (Small Form-factor Pluggable): A compact, hot-pluggable transceiver module.
• GBIC (Gigabit Interface Converter): An older, larger form-factor pluggable transceiver.

EDFA (Erbium-Doped Fiber Amplifier): An optical amplifier used to boost signal strength without electrical conversion.

Light Source / Transmitter: A laser or LED that converts electrical signals to optical signals.

Laser / LED (Light Emitting Diode) / E-LED (Edge-Emitting LED): Types of light sources with different characteristics.

Part 5: Connectors, Polishing & Interfaces

Connector: A mechanical device for demountable fiber connection (e.g., LC, SC, ST, FC).

Ferrule: The precision tube within a connector that holds and aligns the fiber.

Polishing Types: The finish of the connector ferrule end-face.

• PC (Physical Contact) / UPC (Ultra Physical Contact) / APC (Angled Physical Contact): Successively better polish types with lower back reflection (APC has an 8° angle).

MPO (Multi-fiber Push-On): A connector that terminates multiple fibers (e.g., 12, 24) at once.

Simplex / Duplex (SX / DX): A cable/connection for one signal / two signals (often Tx & Rx).

Part 6: Cables & Installation

Cable Construction:

• Strength Members / Armor: Aramid fibers (e.g., Kevlar) for tensile strength / metallic layer for crush and rodent protection.
• OFNP / OFNR (Optical Fiber Nonconductive Plenum / Riser): Cable ratings for use in air-handling spaces / vertical risers.
• Plenum Rated Cable: Cable with fire-retardant jacket for use in plenum spaces.

MIC (Multi-fiber Interconnect Cable): A cable assembly with multiple fibers.

Outside Plant (OSP): Installations outside buildings (aerial, underground, direct burial, submarine).

Conduit: A protective pipe through which cables are pulled.

Part 7: Performance & Measurement

Optical Power: The absolute strength of an optical signal, measured in dBm (decibels relative to 1 milliwatt).

Decibel (dB): A logarithmic unit expressing relative power ratios (e.g., loss or gain).

Attenuation / Loss: The reduction in optical power as it travels along the fiber (dB/km).

Insertion Loss / Splice Loss: The loss from inserting a component / from splicing two fibers.

Back Reflection / Optical Return Loss (ORL): Light reflected back toward the source (expressed in dB).

Dispersion / Chromatic Dispersion: The spreading of an optical pulse over distance, limiting bandwidth.

Bandwidth: The data-carrying capacity of the fiber.

Wavelength (nm) / Frequency: The "color" of light, commonly 850nm, 1310nm, 1550nm for fiber optics.

Numerical Aperture (NA) / Mode Field Diameter: Measure of light-gathering ability / effective diameter of the light mode in SMF.

Refractive Index (IOR): Ratio of the speed of light in vacuum to its speed in a material.

Bit-Error Rate (BER): The fraction of bits transmitted that are received in error.

Part 8: Testing, Installation & Practices

Splice: A permanent joint between two fibers.

• Fusion Splice / Mechanical Splice: Joining fibers by melting them together / using alignment hardware and adhesive.

Termination: The process of installing a connector on a fiber end.

Test Equipment:

• OTDR (Optical Time Domain Reflectometer): Sends a pulse to characterize fiber length, loss, and locate faults.
• Optical Power Meter / Light Source / OLTS (Optical Loss Test Set): Measures power / provides a test signal / combined kit for measuring loss.
• VFL (Visual Fault Locator): A red laser to check continuity and find macro-bends or breaks.

Link Loss Budget: The total permissible loss allocated for a fiber link.

Cleaver / Stripper: A tool for precisely scoring and breaking fiber / removing the coating.

Standards Bodies:

• IEC (International Electrotechnical Commission): Global standards organization for electrical/electronic tech.
• TIA (Telecommunications Industry Association): Develops cabling standards (e.g., TIA-568, TIA-606).
• Conclusion

The world of fiber optics may seem technical, but at its heart it remains a system of simple ideas: guiding light along a path, linking devices together through innovative network designs, and ensuring every connection works as intended. Whether it is through understanding the difference between singlemode and multimode fibers, or knowing how to test a splice correctly, the key is in the details. Over time, experienced technicians and engineers have honed these practices into a set of guidelines that keep our modern communications running reliably.

For all your fiber optic materials and components, trust the quality and reliability of Stanford Optics.