National Physical Laboratory

Chromatic Dispersion

Calibration of the chromatic dispersion in single-mode optical fibres, between 2 km and 50 km in length.  Measurements are possible over the wavelength range 1270 nm to 1640 nm. UKAS accredited service.

The time taken for radiation to propagate down a single-mode fibre depends on the wavelength of the radiation. This arises from the wavelength-dependent properties of the fibre materials and guiding structure. Sources used in communications systems typically emit pulses made up of a range of wavelengths. Thus a pulse broadens as it propagates down the fibre and this limits the minimum usable pulse length and spacing. The variation of propagation time with wavelength is known as dispersion or dispersion coefficient and it sets an intrinsic limit on the information carrying capacity of the fibre. As the lengths and bit-rates of fibre-optic links increase, accurate knowledge of dispersion properties become more important in determining system performance.

Facilities are available at NPL for making measurements of chromatic dispersion on conventional, dispersion shifted and dispersion flattened fibres from 1270 nm to 1640 nm using a variation of the phase shift technique. A handout outlining the techniques used the measure chromatic dispersion in single-mode fibres (PDF File PDF 25 KB) is available to download.

Zero dispersion wavelength and the dispersion slope at zero dispersion wavelength can also be measured. Fibre lengths measured are typically from 2 km to 50 km, with 12 km being ideal. Bare, cabled and connectorised fibre can be accommodated.

Typical fibre types measured are:

  • Standard ITU-T G.652 fibre which has zero dispersion around 1300 nm
  • Dispersion shifted ITU-T G.653 fibre which has zero dispersion around 1550 nm
  • Non-zero dispersion shifted (NZDS) ITU-T G.655 fibres

Dispersion flattened and dispersion compensating fibres can also be measured.

A copy of a typical Calibration Certificate is available to download.

Fibre Type Measurement Range Quantity Typical Uncertainty
Single-mode 1270 nm to 1640 nm Dispersion
Zero dispersion wavelength
Dispersion slope at zero dispersion
± 1.5 %
± 0.1 nm
± 1.5 %


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Last Updated: 18 Aug 2015
Created: 26 Jul 2007


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