A-4
PN: 10410-00742 Rev. H
O/E Module MN4765B OM
A-2 Optical Measurement Considerations
Supplemental Information
Modulator Bias Control
Lithium Niobate modulators are generally biased using a modulator bias
controller (MBC) to control the operating point of the modulator. When biased
in quadrature, the input RF signal linearly modulates the optical carrier.
Note that when an MBC is applied, it must be designed for small signal
operation. The default power of the Anritsu VNA providing 70 GHz is such
that most commercial modulators will be well within their small signal
regime with the VNA’s drive level. When lower frequency VNAs are used, the
output power should be checked against the RF power compression limits of
the modulator being used.
A DC power supply can be used in place of an MBC. However, the stability of
the S21 measurement may be degraded due to drift in the modulator’s bias
point.
Summary of Contents for MN4765B
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