Low insertion loss high temperature stable fiber Bragg grating sensor and method for producing same

An optical waveguide with an inscribed Bragg grating prepared according to a method comprising the steps of:

• providing the optical waveguide;
• providing electromagnetic radiation from an ultrashort pulse duration laser, wherein the electromagnetic radiation has a pulse duration of less than or equal to 5 picoseconds, and wherein the wavelength of the electromagnetic radiation has a characteristic wavelength in the wavelength range from 150 nm to 2.0 microns;
• irradiating the optical waveguide with the electromagnetic radiation to form a Bragg grating, the electromagnetic radiation incident on the optical waveguide being sufficiently intense to cause a permanent Type II change of the index of refraction within a core of the optical waveguide when exposed to laser pulses, wherein the irradiating step is carried out for at least a number of pulses sufficient to form first a non-permanent Bragg grating having a Type I characteristic spectrum with low cladding mode resonance and low scattering loss within the core of the optical waveguide, and wherein the irradiating step is terminated prior to erasure of a Bragg resonance associated with the first non-permanent Bragg grating, and prior to the formation of permanent high scattering loss Type II change of the index of refraction due to the irradiation;
• and
• heating the optical waveguide to a temperature and for a duration sufficient to substantially remove the non-permanent Bragg grating formed in the optical waveguide by the irradiating step until the formation as a result of heating the optical waveguide of a newly formed Bragg grating having a permanent low scattering loss Type II change of the index of refraction.