86108B Auxiliary Input

This 86108B Option 400 front-panel input can provide improved performance in the following situations:

• Marginal Input Signals
• Improved Phase Noise Measurements
• Measurements on Data Rates Above the 14.2 GBd Channel Input Limits

Marginal Input Signal

The Auxiliary Input can be used to reduce unwanted jitter that can occur on the recovered clock under the following situations:

• Low amplitude data or clock signals input to the CH1/CDR− or CH2/CDR+ front-panel input connectors.
• Signals that have excessive noise on slow edges.

This unwanted jitter is caused by AM-to-PM conversion inside the 86108A and can appear on measurements of the input signal. To reduce this effect, provide a separate, synchronous signal to the front-panel Aux Input. This provides a larger signal from which to recover a clock. The result is a cleaner recovered clock signal and lower measured jitter.

Improved Phase Noise Measurements

When using the 86100D-400 PLL and Jitter Spectrum software, you can use the Aux Input to yield more accurate phase noise measurements. Since the Aux Input bypasses the pick-off circuits used on the CH1/CDR− or CH2/CDR+ input, a larger signal is provided to the clock-recovery circuit.

Measurements on Data Rates Above 14.2 GBd Channel Input Limits

For clock recovery, the maximum input to the front-panel CH1/CDR− or CH2/CDR+ input connectors is 14.2 GBd. To perform measurements on signals having higher symbol-rate, connect a sub-rate reference clock to the Aux Input (for example, 468.75 MHz sub-rate clock for 15 GBd data). This technique can also be used for low-amplitude input signals. The input range for the Aux Input is 50 MBd to 14.2 GBd.