Friday, June 4, 2010

Glossary of Common Fiber Optic Terms: M - P

Common Fiber Terms A-E

Common Fiber Terms F-L

Common Fiber Terms: M-P


In an optical fiber, all macro deviations of the axis from a straight line.

Material Dispersion
The dispersion associated with a non-monochromatic light source due to the wavelength dependence of the refractive index of a material or of the light velocity in this material.

Mating Sleeve
A mechanical media termination device designed to align and join fiber optic connectors of the same type. Often referred to as a coupling, bulkhead, or interconnect sleeve.

Mechanical Splicing
Joining two fibers together by permanent or temporary mechanical means (vs. fusion splicing or connectors)

Megahertz (MHz)
A unit of frequency that is equal to one million cycles per second.

Meridional Ray
A ray that passes through the axis of a fiber while being internally reflected (in contrast with a skew ray) and is confined to a single plane.

Microbending Loss
In an optical fiber, loss caused by sharp curvatures involving local axial displacements of a few micrometers and spatial wavelengths of a few millimeters. Such bends may result from fiber coating, cabling, packaging, installation, etc.

A unit of length equal to one-millionth (10 E-6) of a meter (same as a micrometer).

Modal Dispersion
Pulse spreading due to multiple light rays traveling different distances and speeds through an optical fiber.

A stable condition of oscillation in a laser. A laser can operate in one mode (singlemode) or in many modes (multimode). The theoretical underpinnings are extremely complex; the main practical implications are in beam quality.

Mode Changing
In a optical fiber, the exchange of power among modes.

Mode Conditioning Patchcord
a duplex multimode cord that has a small length of singlemode fiber at the start of the transmission leg. The basic principle behind the cord is that you launch your laser into the small section of single mode fiber. The other end of the singlemode fiber is cou­pled to multimode section of the cable with the core offset from the center of the multimode fiber. The laser light thus misses the "dip" and this new launch condition more closely mimics a standard LED launch. The bonus is that you still retain the speed advantages of using a laser.

Mode Filter
A device to remove high order modes to simulate equilibrium mode distribution in a short length of optical fiber.

Mode Scrambler
A device for inducing mode coupling in an optical fiber.

Coding of information onto the carrier frequency. This includes amplitude, frequency, or phase modulation techniques.

See Singlemode

Multifiber Cable
In general usage, a fiber optic cable which containsmany fibers which transmit signals independently and are housed in separate substructures within the cable or otherwise isolated from one another. This term is usually not applied to bundles of fibers which together transmit single signal.

An optical waveguide with a relatively much larger core (commonly 50 to 62.5 micron) than the singlemode waveguide core (2 to 9 microns) and which permits approximately 1000 modes to propagate through the core compared to only one mode through a singlemode fiber.

A device which combines two or more separate signals for transmission through a single fiber. Optical multiplexers combine signals at different wavelengths. Electronic multiplexers combine signals electronically before being converted into optical form.


One-Billionth of a meter (10 E-9) (same as a millimicrometer).

Non-Silica Glasses
A glass in which the primary constituent is a material other than silica (silicon dioxide). The term is sometimes applied to mean non-oxide glasses, those which do not contain oxide compounds. In fiber optics, some of these materials are used for fibers transmitting mid-infrared wavelengths.

Numerical Aperture
NA The numerical aperture of an optical fiber defines a characteristic of the fiber in terms of it's acceptance of light. The "degree of openess", "light gathering ability" and "acceptance cone" are all terms describing this characteristic.


Optical Fiber, Non-conductive, Plenum rated.

Optical Fiber, Non-conductive, Riser rated.

OM1 Fiber Classification (FDDI)
OM1 is legacy (FDDI) grade fiber originally designed for use with LEDs and tend to be 62.5/125 types.  OFL Bandwidth (LED) 850/1300nm ( is 200 / 500.  

OM2 Fiber Classification (50/125)
OM2 fibers enable maintenance and extension to existing 50/125 cabling.  OFL Bandwidth (LED) 850/1300nm ( is 500 / 500

OM3 Fiber Classification (10Gb/s)
OM3 fibers can support 10 Gb/s over 300 meters and are recommended for all new network builds for link distances up to 300 meters. OFL Bandwidth (LED) 850/1300nm ( is 1500 / 500, and Effective Laser Launch Bandwidth at 850nm is 2000  

Optical Attenuation Meter (Attenuator)
Device which measures the loss or Attenuation of an optical fiber, fiber optic cable, or a fiber optic system. Measurements generally are made in decibels.

Optical Break
The breaking of an optical fiber in such a way which predictably produces flattened surfaces that are perpendicular to the longitudinal axis of the fiber. Sometimes referred to as a mirror-like surface across the entire end surface.

Optical Return Loss (ORL)
a reflection that travels down the fiber back to the source. In high speed systems this is undesirable because it can interfere with the transmission. Also referred to as “back reflection”.

Optical Time Domain Refectometer (OTDR)
A method for characterizing a fiber via an optical pulse transmitted through the fiber. The resulting backscatter and reflections are measured as a function of time. The OTDR is useful in measuring attenuation, in distance and identification of defects and other losses.

Output Power (LED)
Radiant power expressed in watts.


Patch Panel
Flat strip of material with adapters for interconnections. Generally 6, 8, or 12 per panel. See Rack Panels

A length of cable with connectors at both ends. Also known as jumpers.

Abbreviation used to denote polyethylene. A type of plastic material used for outside plant cable jackets.

A diode designed to produce photocurrent by absorbing light. Photodiodes are used for the detection of optical power and for the conversion of optical power into electrical power.

A short length of optical fiber with one connector on one end and no connector on the other end.

Pin Photodiode
A semiconductor diode light detector in which a region of intrinsic silicon separates the p and n materials. It offers particularly fast response and is often used in optic systems.

Plastic Clad SiIica (PCS)
A step index optical fiber in which a silica core is covered by a transparent plastic cladding of lower refractive index that of the core. The plastic cladding is usually a soft material, although hard-clad versions have recently been introduced. Offers good radiation resistance.

Plastic Fibers
Optical fibers in which both core and cladding are made of plastic material. Typically their transmission is much poorer than that of glass fibers, and their lowest losses are in the visible region.

An air-handling space such as that found above drop-ceiling tiles or in raised floors. Also, a fire code rating for indoor cable.

Polarization-Maintaining Fiber
A singlemode optical fiber which maintains the polarization of the light which entered it, normally by including some birefringence within the fiber itself. Normal singlemode fibers, and all other types, allow polarization to be scrambled in light transmitted through them.

A step in the connectorization process that creates a flat even surface on the ferrule face. Quality is measured in terms of back reflection reduction. Also referred to as “finish”

Polyethylene (PE)
A type of plastic material used for outside plant cable jackets.

Polyvinyl-chloride (PVC)
A type of plastic material used for cable jacketing. Typically used in flame-retardant cables.

Pulse Dispersion (pulse spreading)
The separation or spreading of the input characteristics of the optical signal that appears along the length of the optical fiber and limits the useful transmission bandwidth of the fiber. Expressed in time and distance a nanoseconds per kilometer. Three basic mechanisms for dispersion are the material effect, the waveguide effect, and the multimode effect.

Pulse Suppressor
A launching fiber used to take up the unmeasurable beginning (dead zone) of an OTDR.

Abbreviation used to denote polyvinyl-chloride. A type of plastic material used for cable jacketing. Typically used in flame-retardant cables.

Abbreviation used to denote polyvinyldiflouride. A type of material used for cable jacketing. Often used in plenum-rated cables.

Common Fiber Terms R-Z