[Gerardo Koji]

Summary

Yesterday Gerardo put the OFI back in the OFI SUS and pre-aligned. Today, the in-situ optical isolation test [LHO ALOG 39359] of the OFI has been carried out. The isolation was measured to be 38.7+/-0.3dB. This clearly passes the requirement of 30dB. The temperature of the OFI at LVEA was 21.4 degC while the OFI was adjusted at 22.7degC at the optics lab.

Method

The fiber coupled beam launcher [LHO ALOG 39357] was used for the test (Attachment 1). The beam launched from HAM6 was aligned carefully with regard to the two irises on the OFI. Once the beam is aligned, the optical power of the transmission (leakage) and the incident beams was measured with a power meter (Thorlabs S140C integrating sphere with Si PD). The power meter was held by a flexible arm attached on the ISI table with a clip (Attachment 2). The power meter leakage was aligned to the leakage beam using a temporary HWP attached on the rear port of the faraday to make the leakage visible.

Result

The temperature of the OFI faraday rotator body measured with Fluke 68 mini was 70.5degF = 21.4degC.

1st meas.: Offset = -0.01 uW, Leakage = 2.39 +/- 0.01 uW, Incident 16.8 +/- 0.1 mW
2nd meas.: Offset = -0.01 uW, Leakage = 2.18 +/- 0.01 uW, Incident 16.9 +/- 0.1 mW
==> 38.7 +/- 0.3 dB
This number well qualifies the requirement of 30dB.

Note that the error is dominated by the systematic error.