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• ADM - Add/drop multiplexer
• AWG - Arrayed waveguide grating
• Attenuator - A passive optical component that intentionally reduces the optical power propagating in a fiber.

• Bend Loss - The result of macrobends (curvature of fiber) or microbends (small distortions in the fiber ) producing increased attenuation by coupling light energy from the fiber core to the cladding.
• Bandpass - A range of wavelengths over which a component will meet specifications.

• CATV - Cable TV
• CWDM - Coarse Wavelength-Division Multiplexing
• Center Wavelength(s) - The nominal operating wavelength(s).
• Cladding - The outer concentric layer that surrounds the fiber core and has a lower index of refraction.
• Core - The central, light carrying part of an optical fiber; it has an index of refraction higher than that of the surrounding cladding.
• Coupler - A passive device that distributes optical power among two or more ports. (Can be in various ratios.) Commonly called a splitter.
• Coupling Ratio — The percentage of light transferred to a receiving output port with respect to the total power of all output ports.

• dB (Decibel) - Unit of measurement of signal strength.
• Decibel- A standard logarithmic unit for the ratio of two powers, voltages, or currents. In fiber optics, the ratio is power.
• Dispersion- A general term for those phenomena that cause a broadening or spreading of light as it propogates through an optical fiber. The three types are modal, material, and waveguide.
• Directivity — Also referred to as near-end crosstalk, it is the amount of power observed at a given input port with respect to an initial input power.
• Demultiplex — The process of separating optical channels.

• EDFA - Erbium-doped fiber amplifier.
• Erbium - doped fiber amplifier- A type of fiber that amplifies 1550-nm optical signals when pumped with a 980- or 1480-nm light source.
• Excess Loss - The ratio of the total output power of a passive component with respect to the input power.

• Fused Coupler - A method of making a multimode or single-mode coupler by wrapping fibers together, heating them and pulling the fibers to form a central unified mass so that light on any fiber is coupled to all output fibers.

• Index of Refraction - The ratio of the velocity of light in free space to the velocity of light in a given material. Symbolized by N.
• Insertion Loss (IL): - Attenuation expressed in dB for a particular path through a component. Insertion loss for Gould couplers includes excess loss, coupling loss and polarization effects.
• ISO - International Standard Organization.
• Isolation - Also referred to as far-end cross-talk or far-end isolation. Predominantly used in reference to WDM products, it is a measure of light at an undesired wavelength relative to the desired wavelength.

• Multiplex — The process of combining optical channels.

• Pigtail - A short length of fiber permanently attached to a component, such as a source, detector, or coupler.
• Pistoning - The movement of a fiber axially in and out of ferrule and, often caused by changes in temperature.
• Polarization Sensitivity - The variation in insertion loss as the polarization state of the input light is varied.

• Return Loss - Also called back reflection; is light that is reflected back along the path of transmission, from either the coupling region, the connector or a terminated fiber.
• Return Reflection - Reflected optical energy that propagates backward to the source in an optical fiber.

• Single - mode fiber- An optical fiber that supports only one mode of light propagation above the cutoff wavelength.
• Star Coupler - A fiber-optic coupler in which power at any input port is distributed to all output ports.
• Strength member - That part of a fiber-optic cable composed of Kevlar aramid yarn, steel strands, or fiberglass filaments that increase the tensile strength of the cable.

• Tap Loss - In a fiber optic coupler, the ratio of power at the tap port to the power at the input port.
• Tap Port - A coupler in which the splitting ratio between output ports is not equal, the output port containing the lesser power.
• TDM- Time-division multiplexing
• Temperature Stability - A measure of insertion loss variation as the device undergoes changes in temperature.

• Uniformity - The maximum insertion loss difference between output ports of a coupler.

• Wavelength - The distance between the same two points on adjacent waves; the time required for a wave to complete a single cycle.
• Wavelength Dependence - The variation in an optical parameter caused by a change in the operating wavelength.
• Wavelength - Division Multiplexing- A transition technique by which separate optical channels, distinguished by wavelength, are multiplexed onto an optical fiber for transmission.
• WDM - Wavelength-division multiplexing