Bachelor Defense by Alexander Rendlev Jensen

Construction of a fiber stretcher for stabilization of fiber length

In this project, we designed and constructed a fiber stretcher to stabilize long fiber delay lines in a highly unbalanced Mach-Zehnder interferometer. Long delay lines make the interferometer highly sensitive to external disturbances such as pressure and temperature changes. The goal of this project was to create a fiber stretcher that mitigates these fluctuations and maintains interferometric balance by altering the length of one of the fiber arms. The fiber stretcher’s flexural design was made in CAD and 3D printed. A piezoelectric actuator drives the expansion of the stretcher. Multiple prototypes were developed to enhance performance. The fibers were coiled to maximize expansion. Ensuring effective expansion of the fiber stretcher by the piezoelectric actuator posed a challenge, which was addressed by designing various compliant mechanisms. We tested the fiber stretcher in an unbalanced Mach-Zehnder interferometer with a 50-meter delay line, of which approximately 5 meters were coiled on the stretcher. The results demonstrated that our fiber stretcher performed well, achieving 37 wavelengths of actuation.