User`s guide

Specifications Definition of Terms

34 Agilent 81560A, 81561A, 81566A, & 81567A Optical Attenuator Modules, First Edition

Relative Power Meter Uncertainty (where

applicable)

When changing the output power of attenuator, the relative power

meter uncertainty is the maximum error of the displayed output

power ratio to the actual output power ratio. This uncertainty is

caused by the internal power meter's nonlinearity and noise and by

errors in the sensing hardware, expressed as ± half the span of all

possible errors with an offset due to the noise level of the power

meter. Symbol RU.

Conditions: at constant polarization state, with random reference

power level taken at an arbitrary displayed attenuation, input power

and output power limitations as specified. This doesn't include the

accuracy of attenuator (nonlinearity).

Measurement: The nonlinearity is calculated using the displayed

power ratio D2 / D1 and the corresponding actual power ratio P2/P1:

The relative power meter uncertainty is then calculated using:

RU is then expressed in dB and the offset is expressed in pW.

NOTE Absolute power meter accuracy attainable with the help of an external

power meter.

⋅=

log10)2,1(

)2,1(max

±=