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Keysight N4917BSCB 400G Optical Receiver Test Application User Guide
3
Concepts and Features of N4917BSCB Software
Automated Calibration
One of the main features of the N4917BSCB solution software is the
automated calibration of stressed receiver conformance test signal as
specified in the IEEE specification.
The signal metrics and the calibration procedure is very similar to those of
NRZ-based 100GBASE transmission standards (as defined in IEEE
802.3ba) but there are noticeable differences:
• A new TDECQ/SECQ metric is employed to characterize the quality of a
transmitted/received signal instead of the traditional eye mask
analysis.
• A digital reference equalizer is required to compute various signal
metrics during transmitter performance testing or during stress signal
calibration for receiver stress testing.
Therefore, achieving accurate, stable and repeatable stress signal
calibration, to ensure reliable transceiver performance test and
qualification, has become even more challenging. Optical receiver stress
test procedures, defined by the IEEE, are performed using several
instruments such as a bit error ratio tester, digital sampling oscilloscope,
optical reference transmitter and tunable laser source. The purpose of the
test is to generate a stable and repeatable stressed optical signal with
specific characteristics, and send it to the receiver under test to measure
the resulting bit error ratio. However, achieving this is not a trivial task as
the combination of different stress factors (inter symbol interference, jitter,
sinusoidal interferences, Gaussian noise, optical power level) gives rise to
complex dependencies on the target metrics.
Composition of IEEE 802.3bs Stressed Receiver Conformance Test Signal
The N4917BSCB software calibrates the stressed receiver conformance
test signal according to the definitions in the IEEE 802.3bs clauses 120,
121, 122, and 124 (for 400GBASE and 200GBASE). Note that you can
change the target values of the metrics to be optimized (select
Debug
in
the
Configure
tab).
The M8045A BERT pattern generator generates a test pattern with the
signal parameters listed in the following table. The calibration procedure
then performs the following steps to create an impaired signal using the
specified stress components and measuring the stress signal calibration
metrics listed in the following table.
