Fiber optic probes allow for in situ characterization of cultural heritage objects and analysis of materials that are difficult to access. Positioning these probes is challenging in terms of focal distance, angle of analysis, and stability. Modifications to improve control include stabilizing the probe against a stationary surface, typically mediated by a tripod, or against the artifact itself with a distance regulating sheath that fixes the focal point at the object surface. The first makes the system less portable, while the second eliminates depth profiling capability. An adjustable working distance adapter was created that allows the operator to position a fiber optic probe against the surface of a transparent artifact and move the working distance up to 6mm into the material while excluding ambient light. The hollow adapter contains no optical fiber, lenses, or windows, so optics are dictated by the fiber optic probe. The tool was created to study the polymeric interlayers in laminated safety glass used in early 20th century aviation and also could be applied to contemporary laminated glass, other multilayer transparent objects, and substances in transparent containers.