81199A Datasheet, PDF (4/17 Pages) Keysight Technologies – Wideband Waveform Center

04 | Keysight | 81195A Optical Modulation Generator Software - Data Sheet
Real Time DSP Engine
The real time DSP engine on the AWG chip of the M8195A arbitrary waveform generator
consists of a fixed concatenation of pre-defined DSP functions and FIR filters, with
programmable coefficients. Coefficient memories of various sizes are available to
change the DSP characteristic upon external triggering or according to a repetitive
dynamic impairment pattern. Output triggers are generated in sync with the coefficient
patterns.
External
waveform /
symbol memory
FPGA
Trigger
Internal waveform
/symbol memory
Hardware encoding and real-time signal property synthesis
Trigger &
coefficients
AWG ASIC
16 tap
FIR
65
GSa/s
DAC
16 tap
FIR
65
GSa/s
DAC
16 tap
FIR
65
GSa/s
DAC
16 tap
FIR
65
GSa/s
DAC
Trigger
PSK/QAM encoder
For the real-time DSP operation, the AWG memory stores the
data pattern symbols which are then encoded using the PSK/
QAM encoder based on reconfigurable look-up tables (LUT),
instead of storing the pre-calculated waveform samples of the
desired signal.
IQ rotator
The IQ rotator consists of two identical blocks where an instan-
taneous rotation angle, controlled from a pre-programmed
coefficient pattern memory, is applied to the complex IQ signal
for both the X and Y polarization, emulating, for example,
carrier phase noise or a frequency offset.
Polarization controller
The polarization controller is a one-tap butterfly filter and alters
the state of polarization (SOP) by acting like a concatenation
of a circular and linear retarder. Rotation angle and retardation
can be controlled from a pre-programmed pattern memory,
which allows complex SOP trajectories on the Poincare sphere
to be synthesized.
PMD emulator
Based on the model of multi-segment concatenation of birefrin-
gent elements, the PMD emulator block is a complex FIR butterfly
structure in which its filter coefficients represent the optical
channel’s PMD impulse response.
Pulse shaper FIR
For a spectrally efficient transmission channels, the data symbols
can be filtered with a general 16-tap FIR filter to flexibly vary the
pulse shaping such as raised or root-raised cosine or the roll-off
factor.
Non-linear equalizer
The non-linear equalizer applies a non-linear transfer function
based on a broken line approximation algorithm to the data
signal, allowing, for example, the equalizer to compensate for the
transfer characteristic of an electro-optical modulator.