National Physical Laboratory

Spectral Attenuation

Calibration of the attenuation of single-mode fibre from 1200 nm to 1650 nm in 5 nm steps. Best measurement capability ± 0.03 dB. Calibration of the attenuation of multimode fibre from 800 nm to 900 nm and 1250 nm to 1350 nm in 5 nm steps. Best measurement capability ± 0.03 dB. UKAS accredited service.

The attenuation of optical fibre is the loss of optical power as it is guided through the fibre. Accurate measurement of power loss in an optical link is essential to maximise the distance between repeater stations.

The attenuation measurement service uses the internationally recognised reference test method known as the cut-back technique. Spectrally selected radiation is launched from a grating monochromator into the fibre under test and the power transmitted recorded as a function of wavelength. The fibre is then cut-back to a few meters without disturbing the launch conditions. The transmitted power through this short length of fibre is again recorded as a function of wavelength, to provide a reference level from which to calculate the spectral attenuation under test.

NPL can supply or measure customer's own fibre. Typical fibre types measured are:

  • Matched Clad (Single-mode)
  • Dispersion Shifted (Single-mode)
  • 50/125 µm multimode fibre
  • 62.5/125 µm multimode fibre

Also available is the NPL-designed Fibre Attenuation Standard which has proven attenuation stability to better than ± 0.03 dB.

A copy of a typical Calibration Certificate is available.

Fibre Type Measurement Range Wavelength Interval Typical Uncertainties
Single-mode 1200 nm to 1650 nm Usually 5 nm ± 0.03 dB
Multi-mode 800 nm to 900 nm
1250 nm to 1350 nm
Usually 5 nm ± 0.06 dB


Customer Service tel: +44 20 8943 8637

Last Updated: 25 Mar 2010
Created: 23 Jul 2007


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