Systems and methods for installing an optical fiber in a downhole equipment system having multiple components that are installed in the field. Components such as sections of an ESP motor are assembled, forming a continuous sealed conduit that extends through the components. The conduit is sealed to prevent potentially damaging fluids from leaking into the conduit. After the conduit through the components is formed, an optical fiber is inserted into the conduit so that the fiber spans the connections between the components. The optical fiber may incorporate multiple sensors (e.g., fiber Bragg gratings) that can sense parameters such as temperature at multiple points in the different components. The passageways through the different components may have different diameters or tapered/chamfered edges to facilitate insertion of the optical fiber in the conduit.