Multiparameter Sensor Based on Single High-Order Fiber Bragg Grating Made With IR-Femtosecond Radiation in Single-Mode Fibers

Abstract

Narrowband multiple high-order Bragg resonances from a single Bragg grating structure inscribed using a femtosecond IR laser and a 4.28 m pitched phase mask are used to demonstrate a multiparameter sensor in standard low cutoff wavelength optical fiber. Six high reflectivity resonances that are observed in the wavelength range from 1 to 2 m can be used to monitor up to six sensing parameters. Temperature and strain coefficients of the grating at each of the high-order Bragg resonances are evaluated.

Femtosecond pulse written fiber gratings: a new avenue to integrated fiber technology

“…Thus, the remaining FBG is of Type II. Naturally, in-fiber Type II gratings that are operable up to close to the melting point of a glass fiber are ideal for sensors in harsh environments (e. g. [43,53,61,65,[92][93][94][95][96]). …”

“…In IR-femtosecond pulse written FBGs, significantly strong reflections resulting from Δn 2 up to Δn 4 could be measured [46,82,125]. With longer periods, Fourier orders from Δn 7 to Δn 12 could be exploited for single mode reflection [95]. Recently, in a bulk piece of fused silica, a volume Bragg grating was inscribed that reflected at wavelengths corresponding from Δn 1 to Δn 7 [126].…”

“…Here, sampling several higher Fourier order peaks (as detailed in Sect. 3.5) can help to decouple both quantities [95]. Another approach could be to use multimode fibers and measure the coupling strength of higher-order modes for determining the bend [93,94].…”

High temperature multiparameter sensor

“…1 While such responses make FBGs useful as sensors, steps are required to provide sufficient distinction between spectral shifts resulting from strain and those induced by variations in temperature. Several examples are available in the literature, including components utilizing Moire gratings 2 , a single grating in multimode fiber 3 , birefringent gratings 4,5 as well as FBGs that capitalize on blackbody radiation in addition to wavelength shift 6 .…”

Study of the effect of source signal bandwidth on ratiometric wavelength measurement

“…Wavelength measurements are very important in many optical systems, such as dense wavelength division multiplexing optical communication systems and sensing systems [1][2][3][4][5][6][7]. Ratiometric wavelength measurement (RWM) is a simple, high-speed, and cost effective technique compared to wavelength scanning based active techniques [8][9][10][11][12][13].…”