Anritsu MN4765B, Operation Manual

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O/E Module MN4765B OM PN: 10410-00742 Rev. H 3-1
Chapter 3 — Operation
3-1 Introduction
This chapter provides information on the operation of the MN4765B O/E
Calibration Module. The illustrations provided for Vector Network Analyzer
connections use the Anritsu VectorStar VNA as an example. Other Anritsu
VNAs use similar connections, but the resulting performance data will be
slightly different.
3-2 E/O Measurements
E/O converters modulate an electrical signal onto light to be sent over fiber
links. The performance of modulators and optical transmitters is key to
determining the maximum data rate achievable in an optical communication
link. These devices are generally characterized in terms of:
• Modulation Bandwidth (transfer function or responsivity)
• Return Loss
• Phase Linearity
• Group Delay
The optical stimulus to the modulator is provided by an external laser source.
The VNA supplies a swept microwave signal over the frequency range of
interest to the modulator. The MN4765B then converts the modulated optical
signal back to an electrical signal that is measured by the VNA. An electrical
calibration is first performed on the VNA to remove the unwanted effects of
the VNA, cables, and other components in the measurement path.
The next step is to remove (de-embed) the photodiode’s known response to
reveal the performance of the E/O converter. The de-embedding of the
photodiode response is performed using the VNA’s internal E/O application
menu. This process requires a characterization file for the photodiode in the
s2p format.
The characterization file is provided on USB memory device along with the
Anritsu MN4765B O/E Calibration Module. Once the response of the
photodiode is removed, the S21 measurement displays the modulator’s
transfer function (ratio of modulated optical output to the electrical input
signal). The 3 dB bandwidth, phase linearity, and group delay of the
modulator can be determined from this transfer function.