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 (Fiber 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.


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.


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.


(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 fiber optics, the surface where two materials meet, as in core-cladding interface, or fiber-to-fiber interface in a connector.


Abbreviation for International Organization for Standardization.