Fiber optics are an integral part of data collection, often used to transport visible and UV light to streaked spectrometers and photodetectors. Precisely measuring fiber-optic time delay (FOTD) is necessary for absolute data timing or fiber replacement. An optical time domain reflectometer (OTDR) can be used to measure the fiber-optic time delay. Commercial OTDR’s measure only the fiber in telecommunications wavelengths in the IR. To measure fibers at relevant wavelengths for inertial confinement fusion experiments, a solution using a free-space image relay was devised at the University of Rochester’s Laboratory for Laser Energetics (LLE), where readily available equipment has been used to measure the FOTD to within 2 ps at 526.5 nm as well as 351 nm, which is an order of magnitude better than the timing jitter between LLE’s Hardware Timing System and second-harmonic (526.5-nm) fiducial laser pulses.

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T. Filkins and J. Katz, "Design of a free-space image-relay optical time-domain reflectometer to measure fiber-optic time delays at inertial confinement fusion relevant wavelengths," Proc. SPIE 11114, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XXI, 1111417 (Presented at SPIE Optical Engineering + Applications: August 14, 2019; Published: 9 September 2019); https://doi.org/10.1117/12.2528806.