Measurement of phase and group refractive indices and dispersion of thermo-optic and strain-optic coefficients of optical fibers using weak fiber Bragg gratings

Cruz, J.L.; Barmenkov, Yuri O.; Dı́ez, A.; Andrés, Miguel V.

doi:10.1364/ao.418049

Cited by 6 publications

(2 citation statements)

References 32 publications

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“…In practice, however, the fringe visibility tends to depart from unity as is increasing, which is resulting in a slight underestimation of the actual , and thus a slight overestimation of . This effect is accentuated for stronger FBGs, so that it is preferable to inscribe weak FBGs for this characterization 19 , 20 . When the spectra of the FBGs are only measured in transmission due to the lack of fiber couplers (i.e.…”

Section: Methodsmentioning

confidence: 99%

“…Another method that has been applied to highly sensitive silica-on-silicon waveguides is to write an array of weak FBGs to infer their dispersion from the measurement of their effective refractive index from 800 nm to 1600 nm 19 . In silica optical fibers, this method has only been limited to a mere 50 nm spectral bandwidth 20 , and its demonstration on a larger scale or in non-photosensitive fiber has yet to be made.…”

Section: Introductionmentioning

confidence: 99%

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Probing the dispersive properties of optical fibers with an array of femtosecond-written fiber Bragg gratings

Boilard

Vallée

Bernier

2022

Sci Rep

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We propose an efficient method to determine the effective refractive index of step-index optical fibers from the visible to the mid-IR and thus allowing to infer their dispersive properties over a broad spectral range. The validity of the method, based on the writing of an array of fiber Bragg gratings (FBGs) with known periods using the fs scanning phase mask technique, is first confirmed with a standard silica fiber, then applied to various fluoride glass fibers to determine their effective refractive index and dispersion over more than three octaves, i.e. from 550 to 4800 nm.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Probing the dispersive properties of optical fibers with an array of femtosecond-written fiber Bragg gratings

Boilard

Vallée

Bernier

2022

Sci Rep

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Accurate compensation and prediction of the temperature cross-sensitivity of tilted FBG cladding mode resonances

Imas

Zamarreño

et al. 2023

Appl. Opt.

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The temperature dependence of core mode resonance has been thoroughly studied in fiber Bragg gratings (FBGs), but it is not the case for cladding mode resonances in multi-resonance gratings such as tilted FBGs (TFBGs). In this work, the temperature sensitivity of ultraviolet written TFBGs in SMF-28 fibers is assessed, demonstrating in the first, to the best of our knowledge, place that a single gauge factor K T = 6.25 ⋅ 10 − 6 ± 0.02 ⋅ 10 − 6 ∘ C − 1 can be employed to characterize the response to temperature of the resonances over the full spectrum in the 10°–50°C range. Then, a simulation model is obtained, enabling to predict TFBG spectra in the 10°–50°C range with high accuracy. This requires a calibration of the core index and dispersion of the TFBG measured in air at 25°C, and determination of the glass refractive index thermo-optic coefficient ( d n / d T = 8.46 ⋅ 10 − 6 ± 0.1 ⋅ 10 − 6 ∘ C − 1 , common to both core and cladding glasses), leading to a mean error on the wavelength position of resonances between 1 and 3 pm. This mean error can be further reduced (less than 1 pm) by considering a linear dependence with temperature of d n / d T . Therefore, this model will enable to completely remove the temperature-induced shifts of all resonances in TFBG sensing applications and measure with great accuracy the variables of interest by using the scaled averages of groups of resonances instead of (less accurate) individual shifts.

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Modal group refractive index measurement of few-mode fibers based on time-domain cross-correlation

Wang,

Huang,

Yan

2024

Appl. Opt.

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We propose a measurement method based on the time-domain cross-correlation technique, combined with the cut-back method, enabling the measurement of group refractive indices (n g ) in few-mode fibers (FMF). A Mach–Zehnder interferometric system, equipped with high-precision and extensive range delay devices, is established. The system records off-axis holograms of spatial reference light at various delays interfering with the emitted light from the fiber under test. The interference energy is extracted from these holograms, and a time-domain mode energy curve is developed utilizing the principle of cross correlation. Optimal holograms at each of the curve peaks are used to reconstruct the modal field distribution, effectively separating and accurately identifying each mode within the FMF. By integrating the cut-back method, the n g corresponding to each mode is calculated based on the changes in group delay before and after fiber cutting. The n g of modes in the two-mode fibers was measured and the differential group delay calculated from the measurement agrees with the manufacturer’s specifications. The measured n g of a standard single-mode fiber aligns with the manufacturer’s specifications. Furthermore, the n g of the higher-order modes in four-mode fibers were measured by exciting them at different angles and validating the wave optics theory that the n g of the fiber modes is independent of the excitation angle. This method can simultaneously measure the n g of several modes in a fiber, providing support for the development and application of FMFs.

show abstract

Measurement of phase and group refractive indices and dispersion of thermo-optic and strain-optic coefficients of optical fibers using weak fiber Bragg gratings

Cited by 6 publications

References 32 publications

Probing the dispersive properties of optical fibers with an array of femtosecond-written fiber Bragg gratings

Probing the dispersive properties of optical fibers with an array of femtosecond-written fiber Bragg gratings

Accurate compensation and prediction of the temperature cross-sensitivity of tilted FBG cladding mode resonances

Modal group refractive index measurement of few-mode fibers based on time-domain cross-correlation

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