| n: Abbreviation for nano. One billionth or 10-9. |
| N: Abbreviation for Newtons. Measure of force generally used to specify fiber optic cable tensile strength. |
| nA: Abbreviation for nanoamp. One billionth of an Amp or 10-9 Amps. |
| NA: See numerical aperture. |
| NAB: Abbreviation for National Association of Broadcasters. |
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| NA Mismatch Loss: The loss of power at a joint that occurs when the transmitting half has a numerical aperture greater than the NA of the receiving half. The loss occurs when coupling light from a source to fiber, from fiber to fiber, or from fiber to detector. |
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| National Electric Code (NEC): A standard governing the use of electrical wire, cable and fixtures installed in buildings; developed by the American National Standards Institute (ANSI), sponsored by the National Fire Protection Association (NFPA), identified by the description ANSI/NFPA 70-1990. |
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| NCTA: Abbreviation for National Cable Television Association. The major trade association for the cable television industry. |
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| NDSF: See non dispersion-shifted fiber. |
| Near-end Crosstalk (NEXT, RN): The optical power reflected from one or more input ports, back to another input port. Also known as isolation directivity. |
| Near Infrared: The part of the infrared near the visible spectrum, typically 700 nm to 1500 nm or 2000 nm; it is not rigidly defined. |
| NEMA: Abbreviation for National Electrical Manufacturers Association. |
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| NEP: See noise equivalent power. |
| Network: 1) An interconnection of three or more communicating entities and (usually) one or more nodes (illustrated). 2) A combination of passive or active electronic components that serves a given purpose. |
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| Network Topology: The specific physical, i.e., real, logical, or virtual, arrangement of the elements of a network. Common network topologies include a bus (or linear) topology, a ring topology, and a hybrid topology, which can be a combination of any two or more network topologies. Illustrated to the right is a bus topology utilizing tee couplers to connect a series of stations that listen to a single backbone of cable. |
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| NF: See noise figure. |
| NFPA: Abbreviation for National Fire Protection Association. Publisher of the National Electrical Code? and 300 other codes and standards through a full, open-consensus process. |
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| nm: Abbreviation for nanometer. One billionth of a meter or 10-9 meters. |
| Node: 1) A terminal of any branch in network topology or an interconnection common to two or more branches in a network. 2) One of the switches forming the network backbone in a switch network. 3) A point in a standing or stationary wave at which the amplitude is a minimum. |
| Noise: 1) An undesired disturbance within the frequency band of interest; the summation of unwanted or disturbing energy introduced into a communications system from man-made and natural sources. 2) A disturbance that affects a signal and that may distort the information carried by the signal. 3) Random variations of one or more characteristics of any entity such as voltage, current, or data. |
| Noise Equivalent Power (NEP): The noise of optical receivers, or of an entire transmission system, is often expressed in terms of noise equivalent optical power. |
| Noise Figure (NF): The ratio of the output signal-to-noise ratio to the input signal-to-noise ratio for a given element in a transmission system. Used for optical and electrical components. |
| Non Dispersion-shifted Fiber (NDSF): The most popular type of single-mode fiber deployed. It is designed to have a zero-dispersion wavelength near 1310 nm. |
| Nonlinearity: The deviation from linearity in an electronic circuit, an electro-optic device or a fiber that generates undesired components in a signal. Examples of fiber nonlinearities include SBS, SRS, FWM, SPM, XPM, and Intermodulation. |
| Non Zero-dispersion-shifted Fiber (NZ-DSF): A dispersion-shifted single-mode fiber that has the zero-dispersion wavelength near the 1550 nm window, but outside the window actually used to transmit signals. This strategy maximizes bandwidth while minimizing fiber nonlinearities. |
| NRZ: Abbreviation for nonreturn to zero. A common means of encoding data that has two states termed “zero?and “one?and no neutral or rest position. |
| ns: Abbreviation for nanosecond. One billionth of a second or 10-9 seconds. |
| NTSC: 1) Abbreviation for National Television Systems Committee. The organization which formulated the NTSC system. 2) Standard used in the U.S. that delivers 525 lines at 60 frames per second. |
| Numerical Aperture (NA): The light-gathering ability of a fiber; the maximum angle to the fiber axis at which light will be accepted and propagated through the fiber. NA = sin a, where a is the acceptance angle. NA also describes the angular spread of light from a central axis, as in exiting a fiber, emitting from a source, or entering a detector. |
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| nW: Abbreviation for nanowatt. One billionth of a Watt or 10-9 Watts. |
| Nyquist Frequency: The lowest sampling frequency that can be used for analog-to-digital conversion of a signal without resulting in significant aliasing. Normally, this frequency is twice the rate of the highest frequency contained in the signal being sampled. Also called Nyquist rate. |
| NZ-DSF: See non zero-dispersion-shifted fiber. |
