Photonics

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16 pages, 13035 KiB

Open AccessArticle

Influence of Optical Fiber Parameters on the Speckle Pattern and Spectral Observation in Astronomy

by Anzhi Wang, Jiabin Wang, Zhaoxv Gan, Gang Yue, Xvdong Chen, Qi Yan, Shengjia Wang, Yunxiang Yan, Tao Geng, Shuang Chen and Weimin Sun

Photonics 2024, 11(11), 1056; https://doi.org/10.3390/photonics11111056 - 11 Nov 2024

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Abstract

Optical fibers serve as a bridge to transmit starlight into the spectrograph in fiber spectral surveys. Due to the interference between multiple modes supported within the fiber, a granular speckle pattern appears on the end of the fiber and leads to an uneven [...] Read more.

Optical fibers serve as a bridge to transmit starlight into the spectrograph in fiber spectral surveys. Due to the interference between multiple modes supported within the fiber, a granular speckle pattern appears on the end of the fiber and leads to an uneven and random energy distribution in the spectrum. This effect is called mode noise, which reduces the accuracy of high-resolution spectral detection. This work investigates the influence of transmitted mode numbers on speckle patterns by using fibers with different core diameters and numerical apertures. A reciprocating mechanical scrambler is proposed for suppressing near-field speckles with negligible focal ratio degradation. We use centroid offset and radial power spectrum to quantitatively evaluate the characteristics of the speckles with and without scrambling. Experimental results show that more modes in a fiber with a larger core diameter reduce the centroid offset of the speckle and make the energy distribution more uniform. The mechanical mode scrambler significantly reduces the random centroid deviation caused by speckles, which is more obvious for large-core fibers. The standard deviation of centroid offset in 1000-cycle tests for the 160 µm core fiber is only 0.043 µm, which is one-tenth of that for the 16 µm core fiber. However, in solar spectrum measurement using these fibers, small-core fibers can more easily achieve higher spectral resolution and capture more spectral information. Therefore, large-core fibers are suitable for tasks requiring high accuracy, while fibers with a smaller core diameter should be applied for high-precision spectral measurement. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Sensing Technology)

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15 pages, 21934 KiB

Open AccessArticle

Improved Sparrow Search Algorithm for Rectangular Planar Array Synthesis

by Qiang Guo, Daren Li, Moukun Fang and Vladimir Tuz

Photonics 2024, 11(11), 1010; https://doi.org/10.3390/photonics11111010 - 26 Oct 2024

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Abstract

To optimize sparse rectangular planar array antennas under multiple constraints, including array aperture, number of elements, and minimum element spacing, an improved sparrow search algorithm (ISSA) is proposed. Initially, a position distribution matrix is generated using the Blackman window weighting method. The sparrow [...] Read more.

To optimize sparse rectangular planar array antennas under multiple constraints, including array aperture, number of elements, and minimum element spacing, an improved sparrow search algorithm (ISSA) is proposed. Initially, a position distribution matrix is generated using the Blackman window weighting method. The sparrow search algorithm (SSA) is then enhanced by incorporating Kent mapping for population initialization, which improves the initial population’s diversity. Additionally, the strategy for updating the discoverer’s position integrates elements from the sine cosine algorithm (SCA), along with a nonlinear sine learning factor, thereby enhancing global search capability. Finally, a crossover strategy is embedded into the SSA to refine the optimization accuracy by improving the search methodology used by the vigilantes. To verify the efficacy of our approach, we carried out simulation experiments. The results demonstrate that this method significantly enhances the performance of the array antenna by reducing the peak sidelobe level and minimizing the zero-trap depth. These findings validate the reliability and effectiveness of the suggested method. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Sensing Technology)

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17 pages, 6355 KiB

Open AccessArticle

Strain Sensing in Cantilever Beams Using a Tapered PMF with Embedded Optical Modulation Region

by Xiaopeng Han, Xiaobin Bi, Yundong Zhang, Fan Wang, Siyu Lin, Wuliji Hasi, Chen Wang and Xueheng Yan

Photonics 2024, 11(10), 911; https://doi.org/10.3390/photonics11100911 - 27 Sep 2024

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Abstract

This paper presents the design of a strain-sensitive, dual ball-shaped tunable zone (DBT) taper structure for light intensity modulation. Unlike conventional tapered optical fibers, the DBT incorporates a central light field modulation zone within the taper. By precisely controlling the fusion parameters between [...] Read more.

This paper presents the design of a strain-sensitive, dual ball-shaped tunable zone (DBT) taper structure for light intensity modulation. Unlike conventional tapered optical fibers, the DBT incorporates a central light field modulation zone within the taper. By precisely controlling the fusion parameters between single-mode fiber (SMF) and polarization-maintaining fiber (PMF), the ellipticity of the modulation zone can be finely adjusted, thereby optimizing spectral characteristics. Theoretical analysis based on polarization mode interference (PMI) coupling confirms that the DBT structure achieves a more uniform spectral response. In cantilever beam strain tests, the DBT exhibits high sensitivity and a highly linear intensity–strain response (R² = 0.99), with orthogonal linear polarization mode interference yielding sensitivities of 0.049 dB/με and 0.023 dB/με over the 0–244.33 με strain range. Leveraging the DBT’s light intensity sensitivity, a temperature-compensated intensity difference and ratio calculation method is proposed, effectively minimizing the influence of light source fluctuations on sensor performance and enabling high-precision strain measurements with errors as low as ±6 με under minor temperature variations. The DBT fiber device, combined with this innovative demodulation technique, is particularly suitable for precision optical sensing applications. The DBT structure, combined with the novel demodulation method, is particularly well-suited for high-precision and stable measurements in industrial monitoring, aerospace, civil engineering, and precision instruments for micro-deformation sensing. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Sensing Technology)

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19 pages, 6503 KiB

Open AccessArticle

Analysis of the Temperature Field Characteristics and Thermal-Induced Errors of Miniature Interferometric Fiber Optic Gyroscopes in a Vacuum Environment

by Zicheng Wang, Xiuwei Xia, Wei Gao and Xiangjun Zhang

Photonics 2024, 11(9), 869; https://doi.org/10.3390/photonics11090869 - 16 Sep 2024

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Abstract

This paper investigates the mechanism of thermal-induced errors in interferometric fiber optic gyroscopes (IFOGs) caused by temperature changes in a vacuum environment, proposing a method for calculating thermal-induced errors in small fiber coils. Firstly, based on the Shupe effect and the thermal stress [...] Read more.

This paper investigates the mechanism of thermal-induced errors in interferometric fiber optic gyroscopes (IFOGs) caused by temperature changes in a vacuum environment, proposing a method for calculating thermal-induced errors in small fiber coils. Firstly, based on the Shupe effect and the thermal stress caused by temperature changes around the fiber coil, a three-dimensional thermal-induced error model for small fiber coils is established. Secondly, a spatial fiber optic inertial measurement unit (IMU) model is designed using the Creo 3D modeling software (creo 7.0.0). The model is then imported into the Ansys finite element simulation software (ANSYS Workbench 15.0), where a temperature field is applied to the IMU based on actual temperature profiles to obtain the temperature distribution of the fiber coil at different times in a vacuum state. These data are then used in the three-dimensional thermal-induced error model to calculate the thermal-induced error of the FOG. Finally, a thermal vacuum experimental platform is set up to collect temperature variation data from the inertial measurement components. The experimental data are compared with the three-dimensional error model proposed in this paper as well as traditional error models. The root mean square error is approximately 33% lower than that of traditional error calculation methods, which also proves the theoretical accuracy. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Sensing Technology)

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14 pages, 3679 KiB

Open AccessArticle

Optical Fibers Use in On-Chip Fabry–Pérot Refractometry to Achieve High Q-Factor: Modeling and Experimental Assessment

by Mohamed Abdelsalam Mansour, Alaa M. Ali, Frédéric Marty, Tarik Bourouina and Noha Gaber

Photonics 2024, 11(9), 852; https://doi.org/10.3390/photonics11090852 - 10 Sep 2024

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Abstract

This paper investigates the integration of optical fibers into an on-chip Fabry–Pérot (FP) resonator to achieve high-quality (Q) factors, which is favorable in sensing applications. Initially designed for high-speed data transmission, optical fibers are now utilized in sensing applications because of their flexibility [...] Read more.

This paper investigates the integration of optical fibers into an on-chip Fabry–Pérot (FP) resonator to achieve high-quality (Q) factors, which is favorable in sensing applications. Initially designed for high-speed data transmission, optical fibers are now utilized in sensing applications because of their flexibility and sensitivity to optical phenomena. This article focuses on the role of single-mode fibers (SMF) and the geometry of different structures in enhancing light confinement within FP resonators. Two distinct on-chip designs utilizing SMFs are demonstrated, modeled, and experimentally evaluated. One achieves a Q-factor higher than 5200, demonstrating significant improvement in light confinement, while the other maximizes the spectral range between the resonant modes’ peaks, maximizing the sensing range through the wavelength shift. This is supported by visualized simulation and coupling efficiencies calculations for fundamental and higher-order modes for comprehensive analysis. Comparison with existing literature is also made, underscoring the advancements achieved by the presented approaches. The findings contribute to the development of microscale refractive index sensing applications, highlighting the vital role of optical fiber integration for high-performance sensing. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Sensing Technology)

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10 pages, 3674 KiB

Open AccessArticle

An S-Shaped Core M-Z Interferometer Induced by Arc-Discharging for Strain Sensing

by Xiaoyang Li, Jiarui Chen, Shengjia Wang, Yongjun Liu and Tao Geng

Photonics 2024, 11(9), 816; https://doi.org/10.3390/photonics11090816 - 30 Aug 2024

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Abstract

In this study, a kind of in-fiber Mach–Zehnder interferometer (MZI) is designed and experimentally examined. The MZI is composed of two in-fiber S-shaped cores (SSCs), which enhance strain sensitivity. To prepare the SSCs, a high-frequency CO₂ laser is first utilized to polish [...] Read more.

In this study, a kind of in-fiber Mach–Zehnder interferometer (MZI) is designed and experimentally examined. The MZI is composed of two in-fiber S-shaped cores (SSCs), which enhance strain sensitivity. To prepare the SSCs, a high-frequency CO₂ laser is first utilized to polish grooves on the symmetrical surface of a single-mode fiber (SMF). The polished area is then subjected to arc-discharging by a commercial fusion splicer, and the core of the fiber bends towards the polished grooves due to the self-roundness of the cladding and the heating effect of discharge. The results of the experiments demonstrate that the sensor achieves high strain sensitivities of −66.5 pm/με and −40.1 pm/με within the strain range of 0 με to 350 με. By solving the matrix equation, simultaneous online measurements of temperature and strain can be performed. With the advantages of easy fabrication, low cost, high sensitivity, and compactness, the proposed sensor is a competitive candidate in strain sensing. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Sensing Technology)

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14 pages, 1121 KiB

Open AccessArticle

Low-Cost High-Speed Fiber-Coupled Interferometer for Precise Surface Profilometry

by Sebastian Hagemeier, Yijian Zou, Tobias Pahl, Felix Rosenthal and Peter Lehmann

Photonics 2024, 11(7), 674; https://doi.org/10.3390/photonics11070674 - 19 Jul 2024

Viewed by 1098

Abstract

Due to their contactless and fast measuring capabilities, laser interferometers represent an interesting alternative to tactile stylus instruments for surface profilometry. In addition to these outstanding attributes, acquisition costs play a major role in industry, limiting the frequent use of optical profilometers, which [...] Read more.

Due to their contactless and fast measuring capabilities, laser interferometers represent an interesting alternative to tactile stylus instruments for surface profilometry. In addition to these outstanding attributes, acquisition costs play a major role in industry, limiting the frequent use of optical profilometers, which are significantly more expensive than tactile profilometers. We present a low-cost laser distance-measuring interferometer featuring axial repeatability below 1 nm at acquisition rates of 38,000 height values per second. The sensor’s performance is validated on several surface standards, achieving lateral scan velocities up to 160 mm/s. Further to high scan velocities, the high acquisition rate enables improved measurement accuracy by averaging measured height values. For example, the standard deviation of 625 pm for repeated measurements can be reduced to 265 pm at the expense of the data rate. However, the sensor concept provides the potential for further improvements in data rate and measurement repeatability. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Sensing Technology)

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14 pages, 2222 KiB

Open AccessArticle

Impacts of Hydrostatic Pressure on Distributed Temperature-Sensing Optical Fibers for Extreme Ocean and Ice Environments

by Scott W. Tyler, Matthew E. Silvia, Michael V. Jakuba, Brian M. Durante and Dale P. Winebrenner

Photonics 2024, 11(7), 630; https://doi.org/10.3390/photonics11070630 - 2 Jul 2024

Viewed by 799

Abstract

Optical fiber is increasingly used for both communication and distributed sensing of temperature and strain in environmental studies. In this work, we demonstrate the viability of unreinforced fiber tethers (bare fiber) for Raman-based distributed temperature sensing in deep ocean and deep ice environments. [...] Read more.

Optical fiber is increasingly used for both communication and distributed sensing of temperature and strain in environmental studies. In this work, we demonstrate the viability of unreinforced fiber tethers (bare fiber) for Raman-based distributed temperature sensing in deep ocean and deep ice environments. High-pressure testing of single-mode and multimode optical fiber showed little to no changes in light attenuation over pressures from atmospheric to 600 bars. Most importantly, the differential attenuation between Stokes and anti-Stokes frequencies, critical for the evaluation of distributed temperature sensing, was shown to be insignificantly affected by fluid pressures over the range of pressures tested for single-mode fiber, and only very slightly affected in multimode fiber. For multimode fiber deployments to ocean depths as great as 6000 m, the effect of pressure-dependent differential attenuation was shown to impact the estimated temperatures by only 0.15 °K. These new results indicate that bare fiber tethers, in addition to use for communication, can be used for distributed temperature or strain in fibers subjected to large depth (pressure) in varying environments such as deep oceans, glaciers and potentially the icy moons of Saturn and Jupiter. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Sensing Technology)

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