Distributed fiber optic chemical and radiation sensors formed by coating the fibers with certain types of response materials are provided. For distributed chemical sensors, the coatings are reactive with the targets; the heat absorbed or released during a reaction will cause a local temperature change on the fiber. For distributed radiation sensors, coating a fiber with a scintillator enhances sensitivity toward thermal neutrons, for example, by injecting light into the fiber. The luminescent components in these materials are taken from conjugated polymeric and oligomeric dyes, metal organic frameworks with sorbed dyes, and two-photon-absorbing semiconductors. The compositions may exhibit strong gamma rejection. Other scintillators combining luminescent materials with neutron converters are available. With a multiple-layer coating, it may be possible to identify the presence of both neutrons and gamma rays, for example. Coatings may be applied during manufacture or in the field.

Distributed fiber optic chemical and radiation sensors formed by coating the fibers with certain types of response materials are provided. For distributed chemical sensors, the coatings are reactive with the targets; the heat absorbed or released during a reaction will cause a local temperature change on the fiber. For distributed radiation sensors, coating a fiber with a scintillator enhances sensitivity toward thermal neutrons, for example, by injecting light into the fiber. The luminescent components in these materials are taken from conjugated polymeric and oligomeric dyes, metal organic frameworks with sorbed dyes, and two-photon-absorbing semiconductors. The compositions may exhibit strong gamma rejection. Other scintillators combining luminescent materials with neutron converters are available. With a multiple-layer coating, it may be possible to identify the presence of both neutrons and gamma rays, for example. Coatings may be applied during manufacture or in the field.

The systems and methods of forming optical fiber coatings with reduced defects include moving a bare optical fiber through first and second coating sub-systems. The first coating sub-system forms a first coating on the bare optical fiber by depositing a first coating material and then curing the deposited first coating material with actinic light. This process also results in the formation of stray actinic light. The process also includes moving the coated optical fiber through a second coating sub-system to form a second coating on the first coating. A light-blocking device resides between the first and second coating sub-systems to block the stray actinic light. Without the light-blocking device, the stray actinic light can enter the second coating sub-system and reach the second coating material therein and form a gel therefrom, which in turn leads to defects in the coated optical fiber exiting the second coating sub-system.