A satellite box prototype was delivered to NAOJ last week, and was insitu revised/modified, having discussions with AEL group.

So the prototype circuit in NAOJ is not the final version; some capacitaces are removed due to their wrong assembly directions, D101 diodes are removed due to similar reason, and a Q101 transistor of Ch1 is removed during the investigation of the circuits.

Anyway, a basic measurement, the noise level of the output of the circuit is preliminarily measured. A PD (S1223-01) in a old design holder is connected to the circuit with a barrack conversion board, and the output's differential outputs are directly connected to a FFT analyzer (Agilent 35670A) with a front end setup of DC float.

The measurement are done during the room lights are turned off as much as possible, and the PD is covered by an easy carton box. So far, for some reason (probably large 50Hz signal), the FFT's range should be set no less than 158 mV, and the most of the measured data are buried under the measurement system noise.

Anyway, the vertical axis is converted to input equivalent current noise density; divided by 2 due to its differential output, and divided by 38.3k Ohm of the transimpedance; see http://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=3499

Note that this is not a test for OSEM but just a basic measurement of the circuit itself. To say something about OSEM, the output should be calibrated to the unit of "m/rtHz".

I'm wondering why the 50Hz apperas such large in the circuit; comparing to the measurement result of an oplev driver so far, it appears a little bit too large...