MX10B, MX40B Series of Optical Transmitters
Chapter 4: Operating Instructions
Page 12
TTN048897-D02
4.3 Bias Settings Page
To get to the Bias Settings page tap the Bias monitors pane on the Home page. The Bias page contains the settings for controlling
the modulator bias and operating modes. There are four modes for MZM bias control: 1) Quadrature, 2) Peak, 3) Null, and 4)
Manual. The screen shot below is an example of how the bias settings page opens up if the controller is in the Quadrature mode.
The blue buttons enable switching between modes.
Figure 18
Bias Settings Page
Active control of the MZM bias point is essential as the modulator is temperature sensitive and will drift over time. The
Quadrature, Peak, and Null modes use a dither tone as part of a lock-in control scheme to keep the MZM bias stable. The dither
tone allows the control algorithm to track the drifting, but at the cost of decreased signal-to-noise ratio (SNR) due to the injection
of a single frequency tone into the MZM bias.
The first time you turn on the MZM Bias control, the instrument will perform a calibration routine to determine the approximate
bias voltages required for the various MZM operating points. This allows the instrument to quickly and effectively switch between
Bias modes. The user may perform this calibration anytime by pressing the Reset Auto Bias button on the right side of the Bias
Settings page. This button is not available if the Bias is off or in Manual mode.
Figure 19
Buttons to Manually Initiate Modulator Calibration Routine
Tap to select Peak Mode
Tap to select Quadrature Mode
Tap to select Null Mode
Tap to select Manual Mode
Tap to turn Bias On/Off
Tap to Reset Modulator Bias
New set points will be stored
