@@ -247,9 +247,15 @@ Another reason of concern about HoQI2 behaviour is that it is not consistent wit
...
@@ -247,9 +247,15 @@ Another reason of concern about HoQI2 behaviour is that it is not consistent wit
\label{hoqi2}
\label{hoqi2}
\end{figure}
\end{figure}
\paragraph*{Intensity fluctuations}
\paragraph*{Power variations}
%Another noise we noticed from the datasheets of the laser modules is the intensity fluctuations: in particular, laser2 is more affected by this noise than laser1 (compare the datasheets reports in Fig. ...). This in part explains why HoQI2 is in general noisier than HoQI1, as shown in the following sections.
The datasheets of the laser modules put in evidence that the power modulation is different for the two lasers: in particular, for laser2 it is higher than laser1 (compare the datasheets reports in \cite{rio} and \cite{riologbook}). This might in part explain why HoQI2 is in general noisier than HoQI1. We monitored the power of both in-loop lasers: according to the datasheet, the power modulation of laser 2 is about 1.56 times higher than for laser 1. In Fig. \ref{power}, the power variation measured at HoQIs input during frequency modulation for the two lasers is consistent with the datasheet. The higher power variations of laser 2 might induce higher intensity fluctuations, which could affect HoQI2.
We also monitored the power of the lasers
\begin{figure}[h!]
\centering
\includegraphics[scale=0.45]{images/power.jpg}
\caption[Power variations of RIO Orion lasers]{Power measured at the input of the two HoQIs, after the polarizing beam splitter (PBS) over 1 hour of data. Laser 2 shows a higher power variation over the same time with respect to laser 1, for a change about 1.56 higher. This is consistent with the datasheet statements, and might also be a reason for the higher noise into HoQI2. However, for practical reasons the power photodiode has been placed after the PBS, a contribution of this optic in this effect is not excluded: there might be internal imperfections which could be accounted for possible polarization variations there on in the fibres.}
\label{power}
\end{figure}
\subsection{Loop performances}
\subsection{Loop performances}
The behaviour of the two HoQIs has been tested in loop and out of loop, to check if they are detecting and responding correctly to the injection of the controller filters through the input modulation of the laser modules. The expectation is that the HoQIs output in out-of-loop mode should show the injection of the gain: Fig. \ref{looptest} shows that the expectations are satisfied.\\
The behaviour of the two HoQIs has been tested in loop and out of loop, to check if they are detecting and responding correctly to the injection of the controller filters through the input modulation of the laser modules. The expectation is that the HoQIs output in out-of-loop mode should show the injection of the gain: Fig. \ref{looptest} shows that the expectations are satisfied.\\
