Methods and apparatuses for monitoring the curing of a photocurable material

An apparatus for monitoring curing of photocurable material, the apparatus comprising:

• an ultraviolet cure light for curing photocurable material;
• an optical fiber having a terminal end and a coupling end;
• a probe light source optically coupled to the coupling end of the optical fiber such that the optical fiber emits a probe light from the terminal end and into the photocurable material;
• a detector optically coupled to the coupling end of the optical fiber;
• and
• a control unit communicatively coupled to the detector, the control unit comprising:
• a processor, and
• a memory storing logic comprising computer readable and executable instructions, which, when executed by the processor, cause the processor to:
• receive a detector signal, from the detector, indicative of the back reflectance of the probe light directed into the photocurable material through the optical fiber as the photocurable material is cured with the ultraviolet cure light;
• and
• determine a refractive index change of the photocurable material as the photocurable material is cured based on the detector signal
• wherein
• the optical fiber is a concentric core optical fiber comprising a terminal end, a coupling end, an inner core, and an outer core in direct contact with and at least partially surrounding the inner core;
• the ultraviolet cure light is optically coupled the outer core at the coupling end of the concentric core optical fiber;
• and
• the probe light source is optically coupled to the inner core at the coupling end of the concentric core optical fiber.