Hello,
This marks my fourth week at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder, working alongside Dmitri Vorobiev. Throughout this week, Hugh and I have continued the fiber cutback experiment. Although we’ve been utilizing the same fiber over the past week, we suspected it had become fractured. Optical fibers are highly sensitive to tension and must be handled with extreme care due to their fragility. A sudden and significant decrease in light transmission confirmed our suspicion that the fiber had fractured.
Consequently, we prepared a new fiber segment, opting for an initial length of four meters to ensure sufficient length for subsequent cutbacks. After cutting and testing this new fiber segment, we observed notably low light transmission levels. This necessitated a series of backfills—a process involving reducing the vacuum chamber pressure to approximately 300 torr and then gradually returning it to near atmospheric pressure. This procedure effectively removes residual oxygen and water vapor from the fiber, both of which strongly absorb ultraviolet (UV) radiation, our target wavelength. After approximately six backfill cycles, we achieved satisfactory light transmission.
Attached is a microscope image illustrating the cleaved end of the fiber. Inspecting the fiber end under a microscope post-cleavage is essential to confirm a clean cut and optimal light transmission.
Also attached is an image of the fiber positioned within the vacuum chamber. We consistently document this setup following each fiber cutback, as the curvature significantly influences light transmission. Maintaining and standardizing the curvature radius within the vacuum chamber is crucial for ensuring reliable and reproducible results.
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