Exfo IQS-12002B Calibration System Manual de usuario descargar pdf (Pagina 75)

Calibration Methods

Calibration System 71

FTB-7000D and FTB-7000B-B OTDR Modules

The fiber section chosen for the loss measurement must be as far as

possible from the VOA to reduce errors due to recovery on the OTDR.

Usually, the fiber section is chosen to roughly emulate a 0.5-dB loss.

The initial measurement, performed at the minimum attenuation of the

VOA, is considered as the reference loss (A

ref

). Following measurements

are done at higher attenuation. The OTDR loss measurements (A

otdr

) must

meet the linearity criteria where nonlinearity (NL) is calculated this way:

The linearity specification must be met for a given attenuation range. This

range depends on the OTDR type, the pulse, and the wavelength. The

attenuation range is limited by noise on the trace or recovery after the VOA.

Note: There is no uncertainty value associated with this measurement.

1max −±=

ref

otdr

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Exfo IQS-12002B Calibration System Manual de usuario Pagina 75