Fiber Optic :: Glossary :: N - O

NA - Numerical Aperture - The light gathering ability of a fiber optic cable. This defines the maximum angle to the fiber optic cable axis at which light will be accepted and propagated down the fiber optic cable. NA= SIN F, where F is the acceptance angle. NA is also used to describe the angular spread of light from the central axis - as in exiting from the fiber optic cable, emitting from a source of entering a detector.

NA mismatch loss - The loss of power at a joint that occurs when the transmitting half has an NA greater than the NA of the receiving half. The loss occurs when coupling light from a source to a fiber optic cable, from fiber optic cable to fiber optic cable or from fiber optic cable to a detector.

NM - Nanometer 1 billionth of a meter.

NEC - National Electrical Code. Defines building flammability requirements for indoor cables.

NEXT - Near End cross-talk.

NIR - Near Infrared.

NIU - Network Interface Unit.

NLO - Non-Linear Optics.

NRZ - On-Off signaling code.

Numerical Aperture - See NA-Numerical Aperture. This is the imaginary cone which defines the acceptance area for the fiber optic cable core to accept light rays.

Open Standard Interconnect - A 7-layer model defined by ISO for defining a data communication network. It provides means for executing the blue print of the network architecture.

Optical cable - An assembly of fiber optic cables and other material providing mechanical and environmental protection.

Optical fiber - Synonym for fiber optic cable.

Optical fiber coupler - This is used in 2 contexts. In the first it refers to a device whose purpose is to distribute optical power among 2 or more ports. In the second it refers to a device whose purpose is to couple power between a fiber optic cable and a source or detector.

Optical link - Any optical transmission channel designed to connect 2 end terminals or to be connected in series with other channels. Sometimes terminal hardware i.e. transmitter and receiver, is included in the definition.

Optical time domain reflectometry - A method of evaluating fiber optic cables based upon detecting backscattered (reflected) light. It is used to measure attenuation, evaluate splice and connector joints and locate faults.

Optical waveguide - Synonym for fiber optic cable.

Optical window - Wavelength range of a fiber optic cable with a very low attenuation. Fiber optic data links using LED sources work in the 1^st window at 850 nm or in the 2^nd window at 1300 nm. Fiber optic data links using laser sources work in the 2^nd window at 1310 nm or in the 3^rd window at 1550 nm.

OPTI-GIGA™ - Graded index plastic fiber optic cable developed by Boston Optical Fiber.

OPTI-LUX™ - Step index plastic fiber optic cable developed by Boston Optical Fiber.

OPTI-MEGA™ - Step index plastic fiber optic cable developed by Boston Optical Fiber.

Opto-electrical Converter - Converts an optical signal into an electrical signal.

Opto-electronics - The range of materials and devices that generate light (lasers and light-emitting devices), amplify light (optical amplifiers), detect light (photodiodes) and control light (electro-optic circuits). Each of these functions requires electrical energy to operate and depends upon electronic devices to sense and control this energy. In a broader sense it means pertaining to a device that responds to optical power, emits or modifies optical radiation or utilizes optical radiation for its internal operation. It is any device which functions as an electrical to optical transducer or optical to electrical transducer.

OSI - Open Standards Interconnect.

OTDR - Optical Time Domain Reflectometer. A method of characterizing a fiber optic cable wherein an optical pulse is transmitted down the fiber optic cable and the resulting backscatter and reflections are measured as a function of time. The OTDR is useful in estimating the attenuation coefficient as a function of distance and identifying defects and other localized losses.