Photonic integration allows for the development of compact and relatively cheap
laser Doppler vibrometers (LDVs). Optical amplification could enhance the performance of
these on-chip LDVs, but the intrinsic noise of optical amplifiers could be detrimental for the
limit of detection (LOD) of the displacement of the LDV. Recent developments in heterogeneous
integration of semiconductor optical amplifiers (SOAs) on the silicon-on-insulator platform allow
for compact and relatively cheap development of on-chip LDVs with SOAs. In this paper, we
study the influence of an SOA on the LOD of an on-chip homodyne laser doppler vibrometer.
We describe the influence of the shot noise and SOA-noise on the LOD of the vibrometer. SOA
intrinsic phase noise depends on the optical power in the SOA, causing the position of the SOA
to have a large influence on the performance. From the analysis, it is shown that SOAs can
improve the performance of a homodyne LDV when there are large losses in the measurement
arm. These losses occur due to the coupling of light from the chip towards the target and back
into the on-chip waveguides.
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