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AdV-DET (Phase camera (2 to be developed))
derossi, tacca, zendri - 16:03 Monday 30 August 2021 (53004) Print this report
Check of the powers on the PC splitting box
We checked the power on the PC splitting box in the laser lab atrium. We measured about 45 mW at the input of the AOM, about 14 mW transmitted by the AOM and about 12 mW summing the three outputs of the splitter. Therefore, most of the losses are at the level of the AOM. We will check the level of the voltage applied to it, to understand if it can explain the losses.
One of the three outputs (more than 4 mW) of the splitter is injected in another 50/50 splitter, the first output is sent to the EIB phase camera (planned at the beginning of AdV but never used and dismantled), the second one is sent to EQB1 for the SQZ PLL. We found that the former output delivers about 1 mW, while the latter about 0.2 mW, meaning that this splitter is not working properly. We will make further checks on this second splitter. Anyway, if more power is needed for the SQZ PLL, we can remove it.
Comments to this report:
zendri, Grimaldi, Tacca - 18:32 Wednesday 01 September 2021 (53032) Print this report

We made a systematic investigation of the optical losses occuring in the phase Cameras AOM box.

First of all we measured the insertion losses of the AOM as a function of the RF driver amplitude. With reference to figure 1 we first measured the power injected by optical fiber into the AOM box.  The  port “P1” input power results 52 mW while the AOM output port “P2” power is

RF Power [dBm] AOM output power [mW] Insertion losses [dB]
0 13.6 5.8
1 16 5.1
2 18.9 4.4
3 21.3 3.9
4 24 3.3
5 26.3 3
6 27.3 2.8

Notes:

- The AOM power is measured directly from the AOM fiber output after disconnecting it from the mating slave.

- RF power means the input power applied to the commercial driver of the AOM

- The RF power at which AOM has so far operated is 4 dBm

Conclusion: Considering that the manufacturer declares a typical insertion loss of 3.5-4 dB (not specific to which RF field amplitude) our AOM seems to work within the specifications.

Subsequently, in order to measure the losses associated with the mating slave, we connected the AOM output  port “P2” and an external 1 meter long optical fiber first to the mating slave “MS1” then to "MS2" and finally on an external mating slave "MSExt". The power measured at the 1 m. long fiber output is reported in the following table:

Mating Slave Fiber output power  [mW] Insertion losses [dB]
MS1 17 1.5
MS2 18 1.25
MSExt 18 1.25

The measurements are made with an RF power of 4 dBm so the insertion losses are calculated assuming  24 mW at the AOM output  (see first table)

The losses associated with the mating slaves  appear not too far from the value  specified by the manufacturer (<1dB.)  

Finally we have measured the value of the outputs of the 3 three branches of the 1x3 fiber splitter after connecting the AOM output to and the 1x3 splitter input to “MS1”. The power is measured at the output of the mating of the AOM box which are labelled respectively R (right) C (center) S (left):

Box Output Port Output power [mW]
MS_L 5
MS_C 4.3
MS_R 4.2

The total insertion loss is 10*Log(17/(5+4.3+4.2))=2 dB which is slightly higher   than what  expected  (order of 1 dB).

In conclusion, the losses associated with the AOM box are only slightly larger (order one dB) than the expected value. 

However we have noticed that the connection to the mating slaves is very delicate. Just shaking the connectors a little  the transmited power change significatly. The values reported are the maximum ones .

At the end of the tests we leave the system in the same configuration it was in initially.

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zendri - 18:46 Tuesday 14 September 2021 (53147) Print this report

Today I measured the RF output of the phase camera AOM driver. 

To do this in the time window between 10:10 and 11:10 UTC the phase camera signal has been turned off.

Measurements made in EE-room where the driver is located

-AOM driver input: -6 dBm

-AOM driver output  +20 dBm ( before injecting the signal into the spectrum analyzer the signal was attenuated by 10 dB. The reported value takes this attenuation into account. Moreover a 5 meter long RG58 cable was used to bring the AOM output signal to the analyzer)

Measurements made in Athrium where the  AOM is located

-AOM input: +19.8 dB  (in this case the 5 meter long cable is not used)

Conclusion: in our standard configuration (4 dBm input) about 30 dBm are applied to the AOM.

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