Technical Information

A selection of general technical information relating to LEMO products are to be found below.
Whilst much of this information is to be found in catalogues, extracts as shown are available to provide information quickly.
If the information you require is not available, please contact us by phone on 01903 234543 or email

Fibre optic contacts cleaning

The cleanliness of fibre optic contact end-faces is of critical importance to the successful performance of your fibre optic system. Maintaining LEMO fibre optic contacts is straightforward as seen in the demonstration video below.

Information on cleaning and inspection equipment is available in the LEMO Fibre Optic Cleaning guide.

Download Fibre Optic contacts cleaning guide leaflet





Alloy: A combination of two or more metal elements.

Alternating Current (A-C): Current in which the charge-flow periodically and regularly reverses in a cyclic manner.

American Society for Testing Materials (ASTM): An organization that tests materials and attempts to set standards on various materials for industry.

Ampere (A): The unit expressing the rate of flow of an electrical current. One ampere is the current flowing through one ohm of resistance at one volt potential.

Annealing: The process of heating to and holding at a suitable temperature and then cooling at a suitable rate, for such purposes as reducing hardness, improving machinability, facilitating cold working, producing a desired micro-structure or obtaining desired physical, mechanical or other properties.

Anodizing: An electrolytic process for producing a protective or decorative film on certain metals chiefly aluminum and magnesium.

ARIB: An acronym for Association of Radio Industry Broadcasters, a standards organization in Japan.

AWG: Abbreviation for American Wire Gauge, a measure of the size or diameter of a wire or conductor.

Back Reflection (Fibre Optic): A measure of the percentage of power reflected back by a discontinuity in a fiber optic line. It is expressed in dB.

Bandwidth: The frequency range over which the connector or device can operate without degradation of performance. Also the information carrying capacity of digital systems.

Base Metal: The metal from which the connector, contact or other metal accessory is made and on which one or more metals or coatings may be deposited.

Bend Radius: The maximum amount fibre or cable that can be bent without causing damage. Also called minimum safe bending radius.

Braid: The covering formed from textile yarn. Braids provide mechanical and thermal protection to plastic insulation, separate cable segments in multi-conductor cables and act as components in flame retardant cables. See also Shield.

Breakdown Voltage: The voltage at which the insulation between two conductors will break down.

Bundle (Fibre Optic): A number of fibres grouped together (rigid or flexible), usually carrying a common signal (or an image, or a conduit for transfer of light power).

Cable: An insulated conductor or group of individually insulated conductors in twisted or parallel configurations.

Cable Assembly: A completed cable and its associated hardware.

Center Conductor: The inner conductive member in a coaxial structure, such as center contacts.

Cladding (Fibre Optic): A layer of glass (or other material) surrounding the core of a fibre, forming the conduit that carries the light through the fibre. It has a refractive index slightly lower than the core.

Coaxial Line: A transmission line consisting of a center conductor suspended in a hollow cylindrical tube with or without a dielectric support. The hollow cylindrical tube is called the outer conductor.

Concentric: A central core surrounded by one or more layers of materials, all sharing a common central axis.

Conductor: A wire or combination of wires not insulated from one another, suitable for carrying electric current.

Connector: Used generally to describe all devices used to provide rapid connect/disconnect service for wires, cables, and fibres.

Contact Engaging & Separating Force: The force needed to either engage or separate pin and socket contacts when they are in and out of connector inserts.

Contact Inspection Hole: A hole in the cylindrical rear portion of contact used to check the depth to which a wire has been inserted.

Contact Plating: Plated-on metal coating applied to the basic contact metal to provide the required contact resistance and/or wear resistance.

Contact Resistance: The maximum permitted electrical resistance of pin and socket contacts when assembled in a connector under typical service use.

Contact Retention: Defines minimum axial load in either direction that a captive contact must withstand while remaining firmly fixed in its normal position within an insert.

Continuity Check: A test performed on a length of finished wire or cable to determine if the electrical current flows continuously throughout the length. Conductors may also be checked against each other to ascertain that there are no shorts between adjacent members.

Contacts: The conducting members of a connecting device that are designed to provide a separable through connection in a cable-to-cable, cable-to-box or a box-to-box situation.

Core: (1) In cables, a term used to express a component or assembly of components over which other materials are applied, such as additional components, shield, sheath, or armour; (2) In fibre optics, the transparent glass or plastic section with a high refractive index through which the light travels by internal reflections.

Corrosion: Corrosion is the slow destruction of materials by chemical agents and electrochemical reactions. The most common kind of corrosion is that of rusting.

Coupler: An intermediate device to provide for attaching special accessories or to provide special mounting means. the method for connecting two connectors that cannot intermate.

Creepage Path: The path electricity must travel across the surface of a dielectric between two conductors. Lengthening the creepage path reduces the possibility of arc damage or tracking.

Crimp Termination: A connection in which a metal sleeve is secured to a conductor by mechanically crimping the sleeve with pliers, presses or automated crimping machines. Splices, terminals and multi-contact connectors are typical terminating devices attached by crimping. Suitable for all wire types.

Current (I): The rate of transfer of electricity, usually expressed in amperes.

Current Rating: The maximum continuous electrical flow of current recommended for a given wire in a given situation. Expressed in amperes (AMPS).

Cycle: The complete sequence including reversal of the flow of an alternating electric current.

dB: (1) Abbreviation for decibel; (2) The loss of a signal in a conductor expressed in decibels, denoting the ratio of the power input to output; (3) One tenth of a bel.

Delay Line: A cable made to provide a very low velocity of propagation with a long electrical delay for transmitted signals.

Derating Factor: A factor used to reduce a current-carrying capacity of a wire when used in environments other than that for which the value was established.

Dielectric: (1) Any insulating medium that intervenes between two conductors and permits electrostatic attraction and repulsion to take place across it; (2) A non-conductive insulator. An "insert" material.

Dielectric Constant (K): That property of a dielectric that determines the electrostatic energy stored per unit volume for unit potential gradient. Also called permittivity and specific inductive capacity.

Dielectric Strength: The voltage which an insulating material can withstand before breakdown occurs, usually expressed as a voltage gradient (such as volts per mil).

Direct Current (D-C): An electric current that flows in only one direction, substantially constant in value.

Durometer: A measurement used to denote the hardness of a substance, usually an elastomer.

Eccentricity: A measure of the center of a conductor's location with respect to the circular cross-section of the insulation surrounding it, expressed as a percentage of center displacement of one circle within the other.

Elastomer: A material which at room temperature, stretches under low stress to at least twice its length and snaps back to original length upon release of stress. Example: rubber.

Electroplating: The electrode position of an adherent metal coating on a conductive object for protection, decoration, or other purposes.

Engaging and Separating Force: The amount of force needed to engage and/or separate contact elements in mating connectors. See "Contact Pressure."

Environmentally Sealed: A connector provided with gaskets, seals, potting, or other devices to keep out moisture, dirt, air, or dust which might lower its performance.

Epoxy Resin: Plastic materials that become hard, infusible solids upon the addition of a hardening agent. Epoxy resins have excellent adhesive action, high chemical, solvent, and thermal resistance, and low shrinkage on curing.

Extraction Tool: A small, hand-held tool used to extract contacts from a connector.

Feed-Thru: A connector or terminal block usually having double-ended terminals which permit simple distribution and bussing of electrical circuits. Also used to describe a bushing in a wall or bulkhead separating compartments at different pressure levels with terminations on both sides.

Ferrule: A short tube used to make solder-less connections to shielded or coaxial cable. In fibre optics, a tube with a central hole that holds the fibre in a connector.

Fibre (Fibre Optic): A short tube used to make solder-less connections to shielded or coaxial cable. In fibre optics, a tube with a central hole that holds the fibre in a connector.

Fibre Optics (F.O.): A general term describing a lightwave or optical communications system. In such a system, electrical information is converted to light energy, transmitted to another location through optical fibres and is there converted back into electrical information.

Flange: A mechanical shoulder on the outside housing, enabling attachment to a panel; can also allow for seals with gaskets or o-rings.

Flexible: That quality of a cable or cable component which allows for bending under the influence of outside force, as opposed to limpness, which is bending that occurs due to the cable's own weight.

Fluorinated Ethylene Propylene (FEP): FEP is similar to polytetrafluoroethylene (PTPE) but has a melting point of about 50? C lower and slightly different physical properties.

Frequency: The number of times an alternating current repeats its cycle in one second, expressed in cycles per second, or Hertz (Hz).

Front Mounted: A connector is front mounted when it is attached to the outside or mating side of a panel. A front mounted connector can only be installed or removed from the outside of the equipment.


Gasket: A component made from an elastomer, such as rubber, to provide an environmental seal in the interface of a connector pair. Also called a "grommet".

Giga: A numerical prefix denoting one billion (109)

Graded Index Fiber (Fiber Optic): A multimode fiber whose core refractive index increases in controlled fashion outward from the axis and matches the cladding refractive index at the core-clad interface. Has greater bandwidth than step index fibre, but less bandwidth than single mode fiber.

Ground (GRD): An electrical term meaning to connect to the earth or other large conducting body to serve as an earth, thus making a complete electrical circuit. Sometimes at zero potential or voltage.

Hard Clad Silica (Fibre Optic): Abbreviated HCS, it is a structure in fibers where the cladding around the glass core is a hard plastic, as opposed to a "PCS," which is a soft plastic cladding.

Heat Shrinkable: The term describing tubes, sleeves, caps, boots, films, or other forms of plastic which shrink to encapsulate, protect or insulate connections, splices, terminations, and other configurations.

Hermetic: Permanently sealed by fusion, soldering, or other means to prevent the transmission of air, moisture vapor, and all other gases. Hermeticity is usually expressed as the rate of leakage volume of tracer gas (such as helium) per second in time.

Hertz (Hz): Unit of frequency equal to one cycle per second.

High Definition Television: Abbreviated as HDTV, a recent form of broadcast of television signals in a significantly higher resolution providing images of superior quality. HDTV signals in the studios and arenas are normally carried over optical fibers due to the high bandwidths required for the digitized signal data.

Hi-pot: A test designed to determine the highest potential that can be applied to a conductor without breaking through the insulation.

High Voltage: Generally, a wire or cable with an operating voltage of over 600 volts.

Holding Strength: The ability of a connector to remain assembled to a cable when under tension.

Housing: The main or largest portion of a connector to which other portions are attached or enclosed.

Impedance (Z): The total opposition that a circuit offers to the flow of alternating current or any other varying current at a particular frequency. It is a combination of resistance R and reactance X, expressed in ohms and designated by Z.

Infrared (Fibre Optic): Light with wavelengths 700-1000 nm, invisible to the eye, and felt as heat.

Inner Conductor: The central conductive member in a coaxial structure, such as the center contact in a coaxial connector.

Insert: That part which holds the contacts in their proper arrangements and electrically insulates them from each other and from the shell. Also called dielectric, insulator, or dielectric support.

Insert Retention: The axial load in either direction that an insert must withstand without being dislocated from its normal position in the connector shell.

Insertion Loss: The loss in load power resulting from the insertion of a cable, component, or device. It is expressed in decibels as the ratio of power received at the load before insertion to the power received at the load after insertion.

Insertion Tool: A small, hand-held tool used to insert contacts into a connector.

Insulation: A material which offers high electrical resistance, making it suitable for covering components, terminals, and wires. This prevents the possible future contact of adjacent conductors resulting in a short circuit.

Insulation Resistance: The ratio of the applied voltage to the total current between two electrodes in contact with a specific insulator.

Interface: (1) A shared boundary;(2) The two surfaces on the contact side of both halves of a multiple-contact connector that face each other when the connector is assembled; (3) In fibre optics, the surface where two materials meet, as in core-cladding interface, or fibre-to-fibre interface in a connector.

IP (Ingress Protection): The International Electrotechnical Commission "Degrees of protection provided by enclosures (IP Code)." The definition of degree of protection (IP code) IEC 60529 outlines an international classification system for the sealing effectiveness of enclosures of electrical equipment against the intrusion into the equipment of foreign bodies (i.e., tools, dust, fingers) and moisture. This classification system utilizes the letters IP (Ingress Protection) followed by two digits; i.e., IP68 where 6 = Dust-tight and 8 = Protection against complete continuous submersion in water (up to 1 meter deep for 15 minutes).

ISO: Abbreviation for International Organization for Standardisation.

Jacket: An outer non-metallic protective covering applied over an insulated wire or cable.

Key: A short pin or other projection which slides in a mating slot or groove to guide two parts being assembled. Generally used in round, shell-enclosed connectors to prevent mating wrong connectors and to assist in polarisation.

Keyway: The slot or groove in which a key slides.

Kilo: A numerical prefix denoting 1000 (10³)

Laser (Fibre Optics): An acronym for "light amplification by stimulated emission of radiation," a device that generates intensified light, usually very directional and over a narrow range of wavelengths. Often a source of light in fibre optic systems.

Light (Fibre Optic): An electromagnetic radiation in the wavelength range including infrared, visible, ultraviolet, and X rays, usually the range visible to the human eye, i.e., the energy that enables vision. Light travels in a vacuum at 300,000 km/sec. (186,281 miles per second).

Lightguide (Fibre Optic): A fiber or a flexible bundle of fibres used to transmit light.

Loose Buffer (Fiber Optic): Also called "loose tube," a protective tube loosely surrounding a cabled fibre, often filled with a gel.

Loss: Energy dissipated without accomplishing useful work, attenuation, usually expressed in dB.

Lug: A mechanical termination, usually crimped or soldered to the conductor, with provision for threading on to a terminal; hardware.


Mate: To join two connector halves in a normal engaging mode.

Mega: A numerical prefix denoting one million (106).

Meter: Unit of length, equal to 39.37 inches.

Micro: A numerical prefix denoting one-millionth (10-6).

Micrometer: One millionth (10-6) of a meter, a unit of length. Used to specify wavelengths.

Micron: (Short for the preferred form "micrometer"): a measure of length equal to 10-6. Used to specify wavelength, it is equal to 1000 nanometers, the preferred term.

Mil: (0.001"): A unit used in measuring the diameter of wire or thickness of insulation over a conductor.

Milli: A numerical prefix denoting one thousandth (10-3).

Mode (Fibre Optic): One of the components of a general configuration of a propagating wave front. Mode is characterized by a particular geometrical pattern and propagation constant.

Moisture Resistance: The ability of a material to resist absorption of moisture.

Multimode Fibre (Fibre Optic): A fibre that transmits many modes.

Nano: A numerical prefix denoting one-billionth (10-9).

Near Infrared: The part of the infrared electromagnetic spectrum near visible wavelengths, in the range of 700 to 1500/2000 nm.

O-Ring: An elastomer gasket enabling a moisture seal, having a circular cross section. See Rubber.

Ohm: Unit of electrical resistance. Resistance of a circuit in which a potential difference of one volt produces a current of one ampere.

Outer Conductor: The external conductive member in a coaxial structure, such as the housing in a coaxial connector.

Overall Diameter: Finished diameter over wire or cable.

Oxidation: Oxidation can be considered the simple addition of oxygen to a metal, e.g., the addition of atmospheric oxygen to iron to form familiar rust. See Corrosion.

PTFE: Abbreviation for polytetrafluoroethylene, commonly known as Teflon.

Phosphor Bronze: This strong and relatively hard alloy is used to fabricate metal parts and springs. Phosphor bronze is resistant to corrosion.

Photon: A quantum of electromagnetic radiation, a unit of light. Light can be viewed as a series of photons.

Physical Contact (Fiber Optic): Abbreviated as PC, this is a design feature of fiber optic connectors, where the mating contacts' faces are in contact and under pressure provided by springs, resulting in lower loss.

Pico: A numerical prefix denoting one-millionth of one-millionth (10-12).

Pin Contact: A male-type contact, usually designed to mate with a socket or female contact. It is normally connected to the "dead" side of a circuit.

Pinholes: Small holes visible on the surface of soldered joints, which generally indicate the presence of a larger void within the joint. Typically caused by the generation of gas during solidification due to presence of salts and water. Sometimes called blowholes.

Plastic Clad Silica (Fiber Optic): A fibre structure where the cladding around the core is a soft plastic, abbreviated PCS.

Plastic Fiber: An optical fibre made of plastic alone.

Plating: The overlaying of a thin coating of noble metal on metallic components to improve conductivity, provide for easy soldering or prevent rusting or corrosion.

Plug: The part of the two mating halves of a connector that is free to move when not fastened to the other mating half. The plug is usually thought of as the male portion of the connector. The plug may have female contacts if it is the "free to move" member.

Polarisation: The arrangement of mating connectors such that the connectors can be mated in only one orientation.

Polarising Pin, Key, or Keyway: A device incorporated in a connector to accomplish polarisation.

Polishing (Fibre Optic): The act of smoothing ends of fibers to an "optically smooth" finish, generally using abrasives. Optically smooth surfaces allow maximum transmission of light between fibres at connections, and minimize coupling loss.

Polyethylene: A thermoplastic with toughness, flexibility at low temperatures, resistance to chemicals and moisture, processability, and relatively low price.

Polytetrafluoroethylene (PTFE): This is the most thermally stable and chemically resistant of all carbonaceous insulating compounds. It is unaffected by sunlight, moisture, and practically all chemicals. Temperature range is -90° to +250° C and electrical properties are very constant over the temperature range and a wide range of frequencies.

Potting: The sealing of a cable termination or other part with a liquid composition that hardens into an elastomer or solid plastic material.

Pre-Tinned Solder Cup: Solder cups whose inner surfaces have been pre-coated a small amount of tin lead solder.

Press-fit Contact: An electrical contact that can be pressed into a hole in an insulator, printed board (with or without plated-through holes), or a metal plate.

Printed Circuit: This term is in common use with at least two meanings:

1. A generic term to describe a printed board produced by any of a number of techniques used to fabricate electrical interconnect systems.

2. A circuit obtained by printing and comprising printed components.

Quadrax: An abbreviation of quadraxial, a concentric cable having a center conductor, two intermediate conductors, and an outer shield, all separated by insulation.

Quick Disconnect: A type of connector shell that permits rapid locking and unlocking of two connector halves.

Radio Frequency (RF): The frequency range is technically broad, from about 25 kHz to 100 GHz, but the term is normally used to define the low range band of frequencies used for broadcast radio signals (including broadcast television) and extends from about 500 kHz to a few hundred megahertz.

Rear Mounted: A connector is rear mounted when it is insta1led from the inside of a box onto a panel. It can only be removed from the inside of the equipment. See Back Mounted.

Receptacle: Usually the fixed or stationary half of a two-piece multiple contact connector. Also the connector half usually mounted on a panel and containing socket contacts.

Reflection Loss (Fibre Optic): Energy reflected back toward a cable source. The reflections occur because the signal strikes a non-uniformity in the shield or conductor.

Resistance: A measure of the difficulty in moving electrical current through a medium when voltage is applied. It is expressed in ohms.

Return Loss: A measure of the percentage of the incident power that is reflected back down the transmission line. Return loss is the percentage reflected power expressed in dB notation.

RG/U: Abbreviation for Radio Guide, Universal. RG is the military designation for coaxial cable.

RMS or rms: Abbreviation for root-mean-square. When the term is applied to alternating voltage and current, it means the effective value; i.e., it produces the same heating effect as a direct current or voltage of the same magnitude. It is also a means of expressing a-c voltage in terms of d-c, usually approximately 70% of the a-c peak voltage.

Rubber: An elastic (natural or synthetic) material (e.g. silicone) used to provide waterproofing or moisture resistance. See O-ring.


Sheath: The outer covering or jacket of a multi-conductor cable.

Shield: In cables, a metallic layer placed around a conductor or group of conductors to prevent electrostatic or electromagnetic interference between the enclosed wire and external fields. See "Braid".

Shield Effectiveness: The ability of a shield to screen out undesirable signals and prevent leakage.

SI: The standard international system of metric units of measurement.

Silica Glass (Fibre Optic): Glass made mostly from silica (silicon dioxide, SiO2) used to make fibers.

Simplex Cable (Fibre Optic): A single fibre cable.

Single Mode Fiber (Fiber Optic): Abbreviated as SMF, a fibre having a small core diameter (approximately 9 microns) with a cladding having a refractive index very close to that of the core. Will transmit light in a single mode that enters at a narrow angle but will transmit over very wide bandwidths.

SMPTE: An acronym for "Society of Motion Picture & Television Engineers," a USA standards organization.

Socket Contact: A female contact designed to mate with a male contact. It is normally connected to the "live" side of a circuit.

Solder: A metal or metal alloy, usually having a low melting point, used to join other metals having higher melting points than the solder.

Solder Cup: A tubular end of a terminal in which a conductor is inserted prior to being soldered. It is also the hollow cylinder at the rear of a solder contact where a wire is inserted and soldered in place.

Solid Conductor: A conductor consisting of a single wire.

Spring Finger Action: Design of a contact as used in a printed circuit connector or a socket contact, permitting easy, stress-free spring action to provide contact pressure and/or retention.

Step Index Fibre (Fibre Optic): A multimode fibre consisting of a core of uniform refractive index surrounded by cladding of a slightly lower refractive index. Accepts light rays over wider angle, but has smaller bandwidth than single mode fiber. See also Graded Index Fibre and Single Mode Fibre.

Stranded Conductor: A conductor composed of groups of wires twisted together.

Surface Mounting: The electrical connection of components to the surface of a conductive pattern without utilizing component holes in a circuit board.

Temperature Rating: The maximum temperature at which a material may be used in continuous operation without a loss of its basic properties.

Temper: (1) The hardness and strength produced by mechanical or thermal treatment or both. It is characterized by a certain structure, mechanical properties or reduction in area during cold working.
(2) A measurement of the degree of hardness or lack of ductility in a metal.

Threaded Coupling: A means of coupling mating connectors by engaging threads in a coupling ring with threads on a receptacle shell.

Tight Buffer (Fibre Optic): A material surrounding a fibre in a cable, holding it firmly in place.

Tinning: Coating of a terminal, lead or conductive pattern with tin or solder alloy to improve or maintain solderability or to aid in the soldering operation.

Total Internal Reflection (Fibre Optic): The phenomenon of light rays reflecting at the core-clad boundary of an optical fiber, allowing transmission along the length of the fibre. It occurs when the angle of incidence is lower than the critical angle.

Transceiver: A device that combines both a transmitter and a receiver.

Transmission: The transfer of electric energy from one location to another through conductors or by radiation or induction fields.

Triaxial: Refers to a three conductor cable with one conductor in the center, a second circular conductor shield concentric with the first, and the third circular conductor shield insulated from and concentric with the first and second, usually with insulation.

Tubing: A tube of extruded non-supported material.

Twisted Pair: A pair of wires twisted together, usually standard low-speed communications wire cables.

UG: The two-letter designation that precedes the number on connectors for coaxial cable. It is an abbreviation for Universal Government.

UL: Mark of approval issued by Underwriters Laboratories, Inc.

Ultraviolet (Fibre Optic): A range of electromagnetic waves in the non-visible spectrum, with wavelengths from 10 to 400 nm (shorter than visible light).

UPC (Fibre Optic): A term describing a specific fiber optic contact polishing protocol (process), yielding improved return loss.

Volt (V): Unit of electromotive force. It is the difference of potential required to make a current of one ampere flow through a resistance of one ohm.

Voltage: The term most often used in place of electromotive force, potential, potential difference or voltage drop, to designate electric pressure that exists between two points and is capable of producing a flow of current when a closed circuit is connected between the two points.

Voltage Breakdown: A test to determine maximum voltage across an insulated wire before electrical current leakage occurs through the insulation.

Voltage Rating: The highest voltage that may be continuously applied to a wire or cord in conformance with standards or specifications.

Voltage Standing Wave Ratio (VSWR): The ratio of the maximum effective voltage to the minimum effective voltage measured along the length of a mismatched radio frequency transmission line.

Watt (W): Unit of power or work done at rate of one joule per second or rate of work represented by current of one ampere under a pressure of one volt (volt-ampere).

Wavelength: The distance measured in the direction of propagation of a repetitive electrical pulse or waveform between two successive points that are characterized by the same phase of vibration (one cycle).

Wiping Action: The action that occurs when contacts are mated with a sliding action. Wiping has the effect of removing small amounts of contamination from the contact surfaces, thus establishing better conductivity.