[Aritomi, Michael]

We measured the visibility between LO and BAB reflected from FC for 10s. The BAB was half detuned.

To know the BAB power during the measurement, we also measured the BAB pick off power in CCFC port. Fig 1 shows the BAB power before AMC and the BAB pick off power. From this measurement, we can know the calibration factor from the BAB pick off power to the BAB power before AMC (bottom plot in Fig 1). The calibration factor is 0.246. The LO power was 1.16V. The offset of visibility was 9mV and the offset of pick off was 5.8mV. Note that the offset subtraction is important for visibility calculation.

The measured visibility and BAB pick off are shown in Fig 2. The 10Hz modulation was applied to IR phase shifter. As you can see, both of visibility and BAB pick off are fluctuating. To calculate the visibility, we divided this data into 1000 segments with 0.01s step (Fig 3) and calculated the visibility in each segment (Fig 4). From the histogram, the visibility is 0.94(1) which corresponds to optical loss of 12(2)%.

In FDS measurement in PRL paper, we assumed that the visibility is 0.98 which corresponds to optical loss of 4%. It seems that the visibility got worse and we have 8% more loss than before...