Fiber bragg grating reference sensor for precise reference temperature measurement

Abstract

A fiber Bragg grating reference module provides a precise temperature reference for a temperature probe, including a thermistor, located in close proximity thereto, and includes an optical fiber having a fiber Bragg grating therein, a glass element and a reference housing. The fiber Bragg grating has two ends and with a coefficient of thermal expansion. The glass element anchors the two ends of the fiber Bragg grating, and has a substantially similar coefficient of thermal expansion as the coefficient of thermal expansion of the fiber Bragg grating to ensure that the glass element does not substantially induce strain on the fiber Bragg grating as the ambient temperature changes. The reference housing has a cavity and also has a means for receiving and affixing one end of the fiber Bragg grating and for suspending the fiber Bragg grating in the cavity leaving the other end of the fiber Bragg grating free to move as the ambient temperature changes without inducing strain in the fiber Bragg grating. The glass element includes a glass tube collapsed over the entire length of the fiber Bragg grating. Alternatively, the glass element includes a glass tube locally collapsed at the two ends of the fiber Bragg grating over a part of length of the fiber Bragg grating.