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3-101

Performance Tests

SDH Transmit/Receive Jitter Amplitude Accuracy

Speciﬁcations

Please refer to the SDH Tx/Rx Jitter Speciﬁcations given in the Speciﬁcations

document provided.

Description

The HP 37718A Transmitter SDH Output is looped to the SDH Input and the signal

is also monitored on the Spectrum Analyzer. The HP 37718A Jitter modulation

frequency is set to a Jitter Amplitude/Frequency check point for the selected SDH

Rate and the Spectrum Analyzer set to observe the displayed spectrum centered at

half this bit rate. The HP 37718A jitter Modulation amplitude is adjusted to known

modulation levels using Carrier to Sideband Ratio, Bessel Null and Peak

Deviation methods for reference. The jitter Amplitude (UI pk-pk) displayed on the

HP 37718A Transmitter and Receiver is checked to ensure it is within speciﬁed

limits. The test is repeated for various Jitter Amplitude/Frequency points to check

the TX and RX ranges.

The Optical SDH rates are tested in a similar way. In this case the HP 37718A

Optical Transmit signal is split using an optical coupler. Part is looped back via an

Optical Attenuator to the HP 37718A Receiver. The split signal is passed through an

O/E Converter to provide an electrical version of the signal for Spectrum Analysis.

Because the SDH Data signal is scrambled this is switched off to observe the

spectral components at half bit rate. A special Calibration test signal is selected

which sets the output pattern to alternating 1/0.

WARNING Safety precautions must be observed when handling the HP 37718A Optical

Modules as these generate laser signals which can cause injury. The guidelines

below must be followed:

Check the connector conﬁguration of the Fiber Optic Interfaces. If these are

ﬁtted with a connector interface other than FC/PC then remove the existing

connector interface and ﬁt the FC/PC connector interface.

Check for any damage to the HP 37718A Fiber Optic Interface spring loaded

aperture covers and connectors. Do not power up the instrument if in any doubt

about the integrity of these connectors.

HP 37718A User Manual

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