EOMs Operating Manual
Ref. Ed. 0
–
08/02/2021
22
3.4
Residual Amplitude Modulation (RAM)
The purpose of any phase modulator is to modulate the phase of light. On an integrated optical
structure like a Lithium Niobate modulator, a perfect phase modulation is true in theory, but also
yields to undesired side effects. Indeed, the optical phase modulation yields a very weak optical
amplitude modulation. The residual amplitude modulation parameter (dB) is defined by the ratio
of the measured AC to DC intensity components at the optical output of the modulator (see the
following set up and graph):
Fig. 34
𝑅𝐴𝑀 = 10 × log
10
(
𝐴𝑚𝑝𝑙𝑖𝑡𝑢𝑑𝑒
𝑀𝑎𝑥.
𝑎𝑚𝑝𝑙𝑖𝑡𝑢𝑑𝑒
)
