National Physical Laboratory

Fibre optic power meters and sources

Facilities have been developed for the calibration of fibre optic power meters. Measurements are made with laser diode sources at standard wavelengths of 850 nm, 1310 nm, 1550 nm and 1625 nm at a power level of 100 µW (- 10 dBm), 10 µW (- 20 dBm) or 5 µW (- 23 dBm). Alternatively measurements are possible with a suitable source provided by the customer at a small additional cost. Calibrations are carried out by direct comparison with specially developed secondary standards suitable for use with optical fibre which have been calibrated against the standards trap detectors. Measurements can be made with single mode fibre at 1310 and 1550 nm and with multimode fibre at 850 and 1300 nm.

The calibration can be extended to other power levels in the range 100 mW to 1 pW (+20 to -90 dBm) by direct comparison of the response of the meter with a detector whose linearity has been determined previously. Measurements are normally carried out at two power levels per decade.

Power meters fitted with FC/PC-type connectors can be calibrated with typical uncertainties as shown in the table below. Other types such as SC/PC, FC/APC, SC/APC and ST-style connectors can also be accommodated but the associated measurement uncertainties are likely to be higher.

Power meters can also be characterised at power levels greater than + 20 dBm and at wavelengths other than those stated here.

Measurement Range Typical Uncertainties

Absolute Response - Power levels of 100 µW (- 10 dBm), 10µW (- 20 dBm) or 5 µW (- 23 dBm)

850 nm ± 30 nm (Multimode fibre) ± 1.0%
1300 nm ± 25 nm (Multimode fibre) ± 1.0%
980 nm ± 10 nm (Single-mode fibre) ± 1.0%
1300 nm ± 25 nm (Single-mode fibre) ± 1.0%
1500 nm ± 35 nm (Single-mode fibre) ± 1.0%
1550 nm ± 20 nm (Single-mode fibre) ± 1.0% (± 0.04 dB)
1620 nm ± 20 nm (Single-mode fibre) ± 1.0%

Linearity of Response

100 mW to 10 mW (+20 dBm to +10 dBm) ± 0.7%
10 mW to 1 pW (+10 dBm to -90 dBm) ± 0.3%

Further information can be downloaded from the following data sheet (PDF File PDF 562 KB)

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

Relative spectral responsivity calibrations are not normally carried out using optical fibre and are carried out by the Optical Radiation Measurement Group at NPL. But for small area detectors which require the radiation coupled by fibre, special measurements can be made.


The emission characteristics of laser diodes and LED sources for use in fibre optic systems can be measured using an optical spectrum analyser, the wavelength setting of which has been calibrated with spectral lines from lasers and gas discharge lamps. Measurements can be made of the spectral content and centre wavelength of the source. In addition, the stability of the source can be characterised over a two-hour period after switch-on.

For high accuracy measurements of single-line, DFB and frequency stabilised sources, click here for more information.

Measurement Range Typical Uncertainties
Effective centre wavelength of a laser diode or LED source (800 nm to 1700 nm) ± 0.3 nm
Spectral halfwidth of laser diode or LED source (0.07 - 50 nm) ± 0.1 nm
Output power stability of fibre optic light sources ± 0.004 dB


Customer Service tel: +44 20 8943 6151

Last Updated: 18 Nov 2014
Created: 23 Jul 2007


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