Patent ID: 8768112

Claim:
A system, comprising: an electrical generator comprising a stator, a rotor, and a gas coolant path through an interior of the electrical generator; and at least one fiber optic purity sensor configured to sense a gas purity of a flow of a gas coolant through the gas coolant path, wherein the at least one fiber optic purity sensor comprises: a fiber core; a refractive index periodic modulated grating structure positioned about the fiber core; a fiber cladding positioned around the refractive index periodic modulated grating structure; and a multilayered sensing film positioned about the fiber cladding, wherein the multilayered sensing film comprises: a modulated structure of multiple high refractive index and low refractive index material layers; a first coating configured to enable detection of a hydrogen level in air; a second coating configured to enable detection of a hydrogen level in carbon dioxide; and a third coating configured to enable detection of a carbon dioxide level in air.