Hollow core fiber Fabry-Perot interferometers with reduced sensitivity to temperature: erratum.

In the original publication of our research article "Hollow core fiber Fabry-Perot interferometers with reduced sensitivity to temperature" [Opt. Lett.47, 2510 (2022)10.1364/OL.456589OPLEDP0146-9592], we identified an error that requires correction. The authors sincerely apologize for any confusion that may have arisen from this error. The correction does not affect the overall conclusions of the paper.

Hollow-core fiber with stable propagation delay between -150°C and +60°C.

Optical fibers with a low thermal coefficient of delay (TCD) have been developed for frequency and timing transmission/distribution. However, their temperature sensitivity changes as a function of temperature and, to date, no study of such fibers has demonstrated improved performance over extended temperature ranges, especially at sub-zero temperatures. Here, we show that a hollow core fiber (HCF) with a thin acrylate coating can have a TCD within ±2.0 ps/km/°C over a broad temperature range from -150°C to +60°C. In addition, this thinly coated HCF can be fully insensitive to temperature around -134°C, making it of interest, e.g., for laser stabilization close to cryogenic temperatures.

Hollow-core fiber Fabry-Perot interferometers with reduced sensitivity to temperature.

We demonstrate a 3× thermal phase sensitivity reduction for a hollow-core fiber (HCF) Fabry-Perot interferometer by winding the already low temperature sensitivity HCF on to a spool made from an ultralow thermal expansion material. A record low room temperature fiber coil phase thermal sensitivity of 0.13 ppm/K is demonstrated. The result is of particular interest in reducing the thermal sensitivity of HCF-based Fabry-Perot interferometers (for which existing thermal sensitivity reduction methods are not applicable). Our theoretical analysis predicts that significantly lower (or even zero) thermal sensitivity should be achievable when a spool with a slightly negative coefficient of thermal expansion is used. We also suggest a method to fine-tune the thermal sensitivity and analyze it with simulations.

Efficacy of a Digital Sports Vision Training Program for Improving Visual Abilities in Collegiate Baseball and Softball Athletes.

SIGNIFICANCE: Dynamic reactive sports involve visual abilities such as visual acuity, depth perception, contrast sensitivity, and visual-motor reaction speed. This randomized, double-blinded control design showed no significant improvement in the visual parameters among athletes after training on a digital sports vision training program. PURPOSE: There is a need for evidence supporting the efficacy of recently developed digital training programs. METHODS: Thirty-two athletes from National Collegiate Athletic Association Division III softball and baseball teams were randomly divided into experimental and placebo training groups, undergoing three 20-minute training sessions per week for 3 weeks. The experimental group trained on procedures designed to improve dynamic visual acuity and depth perception, and the placebo group trained on procedures designed to have no direct impact on those same parameters. All measures were recorded at baseline, post-training, and after a month of no training. The athletes also completed a questionnaire to determine the efficacy of the placebo effect. RESULTS: There was no significant effect of evaluation type (post-training and follow-up) and condition (experimental and placebo) on any of the visual parameters. However, stereoacuity, contrast sensitivity, depth perception, and dynamic visual acuity showed minimum effect sizes of 0.5. Fifteen of 16 athletes in the placebo group thought they trained on experimental procedures. CONCLUSIONS: No significant improvement differences were seen between experimental and placebo training groups. However, stereoacuity, contrast sensitivity, and depth perception achieved minimum clinical relevance.

Compact micro-optic based components for hollow core fibers.

Using micro-optic collimator technology, we present compact, low-loss optical interconnection devices for hollow core fibers (HCFs). This approach is one of the key manufacturing platforms for commercially available fiber optic components and most forms of HCFs can readily be incorporated into this platform without the need for any substantial or complicated adaptation or physical deformation of the fiber structure. Furthermore, this technique can provide for very low Fresnel reflection interconnection between solid-core fiber and HCF and in addition provides a hermetic seal for HCFs, which can be a critical issue for many HCF applications. In this paper, several exemplar HCF components are fabricated with low insertion loss (0.5-2 dB), low Fresnel reflection (-45 dB) and high modal purity (>20 dB) using various state-of-the-art HCFs.

Composite material anti-resonant optical fiber electromodulator with a 3.5 dB depth.

The hollow regions of an anti-resonant fiber (ARF) offer an excellent template for the deposition of functional materials. When the optical properties of such materials can be modified via external stimuli, it offers a method to control the transmission properties of the fiber device. In this Letter, we show that the integration of a ${{\rm MoS}_2}$MoS2 film into the ARF voids allows the fiber to act as an electro-optical modulator. We record a maximum modulation depth of 3.5 dB at 744 nm, with an average insertion loss of 7.5 dB.

Fabrication of tubular anti-resonant hollow core fibers: modelling, draw dynamics and process optimization.

The fabrication of hollow core microstructured fibers is significantly more complex than solid fibers due to the necessity to control the hollow microstructure with high precision during the draw. We present the first model that can recreate tubular anti-resonant hollow core fiber draws, and accurately predict the draw parameters and geometry of the fiber. The model was validated against two different experimental fiber draws and very good agreement was found. We identify a dynamic within the draw process that can lead to a premature and irreversible contact between neighboring capillaries inside the hot zone, and describe mitigating strategies. We then use the model to explore the tolerance of the draw process to unavoidable structural variations within the preform, and to study feasibility and limiting phenomena of increasing the produced yield. We discover that the aspect ratio of the capillaries used in the preform has a direct effect on the uniformity of drawn fibers. Starting from high precision preforms the model predicts that it could be possible to draw 100 km of fiber from a single meter of preform.

Triple-clad photonic lanterns for mode scaling.

We propose a novel triple-clad photonic lanterns for mode scaling. This novel structure alleviates the adiabatic tapering requirement for the fabrication of large photonic lanterns. A 10-mode photonic lantern with insertion losses ranging from 0.6 to 2.0 dB across all the modes and a record-low pairwise 4-dB mode-dependent loss at C-band was demonstrated.

Brain Injury Vision Symptom Survey (BIVSS) Questionnaire.

PURPOSE: Validation of the Brain Injury Vision Symptom Survey (BIVSS), a self-administered survey for vision symptoms related to traumatic brain injury (TBI). METHODS: A 28-item vision symptom questionnaire was completed by 107 adult subjects (mean age 42.1, 16.2 SD, range 18-75) who self-reported as having sustained mild-to-moderate TBI and two groups of reference adult subjects (first-year optometry students: mean age 23.2, 2.8 SD, range 20-39; and 71 third-year optometry students: mean age 26.0, 2.9 SD, range 22-42) without TBI. Both a Likert-style method of analysis with factor analysis and a Rasch analysis were used. Logistic regression was used to determine sensitivity and specificity. RESULTS: At least 27 of 28 questions were completed by 93.5% of TBI subjects, and all 28 items were completed by all of the 157 reference subjects. BIVSS sensitivity was 82.2% for correctly predicting TBI and 90.4% for correctly predicting the optometry students. Factor analysis identified eight latent variables; six factors were positive in their risk for TBI. Other than dry eye and double vision, the TBI patients were significantly more symptomatic than either cohort of optometry students by at least one standard deviation (p < 0.001). Twenty-five of 28 questions were within limits for creating a single-dimension Rasch scale. CONCLUSIONS: Nearly all of the adult TBI subjects were able to self-complete the BIVSS, and there was significant mean score separation between TBI and non-TBI groups. The Rasch analysis revealed a single dimension associated with TBI. Using the Likert method with the BIVSS, it may be possible to identify different vision symptom profiles with TBI patients. The BIVSS seems to be a promising tool for better understanding the complex and diverse nature of vision symptoms that are associated with brain injury.

Investigation of the Thermal Stability of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) Materials Proposed for Inert Matrix Fuel Applications.

Inert matrix fuels (IMF) consist of transuranic elements (i.e., Pu, Am, Np, Cm) embedded in a neutron transparent (inert) matrix and can be used to "burn up" (transmute) these elements in current or Generation IV nuclear reactors. Yttria-stabilized zirconia has been extensively studied for IMF applications, but the low thermal conductivity of this material limits its usefulness. Other elements can be used to stabilize the cubic zirconia structure, and the thermal conductivity of the fuel can be increased through the use of a lighter stabilizing element. To this end, a series of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials has been synthesized via a co-precipitation reaction and characterized by multiple techniques (Nd was used as a surrogate for Am). The long-range and local structures of these materials were studied using powder X-ray diffraction, scanning electron microscopy, and X-ray absorption spectroscopy. Additionally, the stability of these materials over a range of temperatures has been studied by annealing the materials at 1100 and 1400 °C. It was shown that the Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials maintained a single cubic phase upon annealing at high temperatures only when both Nd and Sc were present with y ≥ 0.10 and x + y > 0.15.