In part, the disclosure relates to a lens assembly. The lens assembly can be used to direct light for sensing and imaging. In one embodiment, the lens assembly is a component of an intravascular data collection probe such as an optical coherence tomography probe. The lens assembly can include an optical fiber having a first diameter and a gradient index lens that includes a rod having a length L. The rod can include a substantial planar end and a polished end. The rod can include a longitudinal axis and a second diameter. The second diameter is greater than the first diameter in one embodiment. The substantially planar end is optically coupled to an endface of the optical fiber. The refractive index changes along the length L of the rod.
