MEASUREMENTS

• Attenuation:

The reduction in optical power as it passes along a fibre, usually expressed in decibels (dB).

• Bandwidth:

The range of signal frequencies or bit rate within which a fibre optic link or network will operate.

• Chromatic dispersion:

A property of optical fibre due to which different wavelengths travel at different speeds and arrive at different times, resulting in spreading of a pulse in an optical waveguide.

• Decibels (dB):

A unit of measurement for optical power which indicates relative power. A -10 dB means a reduction in power by 10 times.

• dBm:

Absolute Power, Optical power referenced to 1 milliwatt.

• Nanometer (nm):

A unit of measure used to measure the wavelength of light (meaning one one-billilonth of a meter)

• Optical Loss:

The amount of optical power lost during transmission of through fiber, splices, couplers, etc. expressed in dB.

• Optical Power:

It is measured in "dBm", or decibels referenced to one miliwatt of power. While loss is a relative reading, optical power is an absolute measurement, referenced to standards. Absolute power is measured to test transmitters or receivers and relative power to test loss.

• Optical Return Loss, back reflection:

Light reflected from the cleaved or polished end of a fibre caused by the difference of refractive indices of air and glass.

• Power budget:

The total amount of power lost in the link. Often used in terms of the maximum amount of loss that can be tolerated by a given link.

• Polarization Mode Dispersion:

The spreading of a pulse in an optical waveguide by virtue of different light paths lengths is called Modal dispersion.

• Refractive index:

A measure of the speed of light in a material, a property of optical materials that relates to the velocity of light in the material

• Scattering:

The change of direction of light after striking small particles that causes loss in optical fibres and is used to make measurements by an OTDR

• Wavelength:

A term for the colour of light, usually expressed in nanometres (nm) or microns (m). Fibre is mostly used in the infrared region where the light is invisible to the human eye.