[Izumi, Sugimoto, Yokogawa]

The fringe in fiber transmitted beam

Yesterday, we found fringe in fiber transmitted beam (log6044). We attempted to clean fiber end face and change fiber coupler.

Cleaning of fiber end face

We tried cleaning the end face of the optical fiber but it was ineffective.

Fiber coupler

We change fiber coupler from PAF2-5A to PAF-X-5-A. PAF2-5A is a new type of PAF-X-5-A and the focal length of colimate lens does not change. The fringe disappeared.

However, We don't konw why fringe occur when using a new type of coupler. Perhaps the compatibility between the new type and the old type may be bad because the old type is used for input side.

Before the change

After the change

Measurement beam mode

We completed the optics on POP table and measured beam mode after the mode match lens. If this beam is incident on X aem cavity, mode matching coefficient is 85% in my calculation.

Alignment of green beam

We aign green beam to hit the center of beam target in front of PR2.  We achieved our goal this week!

Next; align green beam using the steering mirror with picomotor (one in PR2 chamber and the other on POP table).