Fiber Attenuation Research Articles

An improved calibration procedure for accurate plastic scintillation dosimetry on an MR-linac.

Plastic scintillation dosimeters (PSDs) are highly suitable for real-time dosimetry on the MR-linac. For optimal performance, the primary signal (scintillation) needs to be separated from secondary optical effects (Cerenkov, fluorescence and optical fiber attenuation). This requires a spectral separation approach and careful calibration. Currently, the 'classic' calibration is a multi-step procedure using both kV and MV X-ray sources, requiring an uninterrupted optical connection between the dosimeter and read-out system, complicating efficient use of PSDs. Therefore, we present a more time-efficient and more practical novel calibration technique for PSDs suitable for MR-linac dosimetry.
Approach: The novel calibration relies on prior spectral information combined with two 10x10 cm2field irradiations on the 1.5 T MR-linac. Performance of the novel calibration technique was evaluated focusing on its reproducibility, performance characteristics (repeatability, linearity, dose rate dependency, output factors, angular response and detector angle dependency) and IMRT deliveries. To investigate the calibration stability over time, prior spectral information up to 315 days old was used. To quantify the time efficiency, each step of the novel and classic calibration was timed.
Main results: The novel calibration showed a high reproducibility with a maximum relative standard deviation of 0.3%. The novel method showed maximum differences of 1.2% compared to the gold-standard calibration, while reusing old classic calibrations after reconnecting fibers showed differences up to 3.0%. The novel calibration improved time efficiency from 105 to 30 minutes compared to the classic method.
Significance: The novel calibration method showed a gain in time efficiency and practicality while preserving the dosimetric accuracy. Therefore, this method can replace the traditional method for PSDs suitable for MR-linac dosimetry, using prior spectral information of up to a year. This novel calibration facilitates reconnecting the detector to the read-out system which would lead to unacceptable dosimetric results with the classic calibration method.

Distributed vibration and temperature sensing system by multiplexed fiber scattering spectra

A new, to the best of our knowledge, distributed optical fiber vibration and temperature hybrid sensing system is proposed and experimentally demonstrated. The proposed system only employs two signal channels, which is more compact and practical. Based on the structure of the optical time domain reflectometer (OTDR), the Rayleigh scattering light and the Raman anti-Stokes scattering light is extracted for vibration and temperature sensing, respectively. For vibration sensing, a new differential location algorithm based on polarization state analysis of the Rayleigh scattering light is proposed to locate the vibration events. It first rectifies the original OTDR traces by fiber attenuation compensation to make each position in it with the same pulse power level. And then, by difference of adjacent traces and threshold discrimination, the vibration positions are identified and located. For temperature sensing, a temperature calibration unit and algorithm are adopted to dynamically correct the trace data and reduce the temperature measurement error caused by the instability of the pulse laser source. The experiment is conducted with a fiber range of about 12 km and laser pulse width of 60 ns, and the experimental results show that the maximum error range for temperature measurement is −0.7∘C to 1.3°C, with a root mean square (RMS) error of 0.85°C in the entire temperature measurement range. Additionally, the spatial resolution (SR) for both vibration and temperature sensing is 6 m.

An advanced fabrication method for Yb3+-Doped optical fibers featuring AlPO4 core glass

Ytterbium (Yb)-doped fibers using aluminophosphosilicate (Yb-APS) host glass offer significant advantages over conventional aluminosilicate (Yb-AS) fibers, such as strong photodarkening resistance, higher RE-ion solubility and lower Numerical Aperture (NA), making them ideal for high-power laser applications. However, achieving optimal performance in Yb-APS fiber fabrication poses various challenges, including maintaining a precise Al3+/P5+ ratio (1:1), minimizing the central dip in the refractive index profile (RIP), ensuring proper dopant distribution, and reducing background loss. We introduce a new fabrication method for Yb-APS fiber to address these challenges. This approach entails first synthesizing amorphous Yb³⁺: AlPO4 particles, then incorporating them into the fiber core using a hybrid technique that merges Vapor Phase Delivery (VPD) with solution doping (SD). We extensively utilized various materials and optical characterizations, including XRD, FTIR, Raman spectroscopy, FESEM, and XPS, to fine-tune the composition of Yb³⁺: AlPO4. The optical characterization of the developed preform sample, including absorption, emission, and luminescent lifetime measurements, was conducted to assess the fabrication technique's suitability. The results confirmed the successful incorporation of Yb-ions into the preform core, with peaks consistent with reported values. The fiber's attenuation loss was measured, showing approximately 10 dB/km at 1200 nm. This indicates that the particles dissolved smoothly during preform and fiber processing, resulting in minimal scattering loss in the fiber core. The developed fiber demonstrated NA of 0.1, uniform RIP along the preform length with significant reduction of the central dip formation and improved spectral performance (∼1.7X broader bandwidth) compared with an equivalent Yb-AS fiber. These findings suggest the Yb-APS fiber's overall effectiveness and structural robustness, highlighting the potential of the proposed fabrication method for high-power fiber laser applications.

Beam loss detection based on generation of Cherenkov light in optical fibers in the CERN Linear Electron Accelerator for Research

Cherenkov optical beam loss monitors (oBLMs) based on optical fibers are a revolutionary achievement among the monitoring systems in particle accelerators. Due to the nature of the Cherenkov phenomenon and the intrinsic characteristics of optical fibers, the photon production and fiber light transmission need to be studied to deduce the total amount of Cherenkov photons detected by the photosensors attached at the end of the system. Simulations of the Cherenkov oBLM detector system have been implemented using the software with postprocessing considering the light attenuation and capture factors in the optical fiber. In addition, the study includes the longitudinal beam loss localization of the controlled beam losses produced along the CERN Linear Electron Accelerator for Research (CLEAR) test facility line. In this paper, the Cherenkov photon detection by an oBLM installed in the CLEAR facility is simulated, analyzed, and compared with experimental data. Published by the American Physical Society 2024

Tunable fiber attenuator for electrically wet-driven micromirrors

Herein we report an electronically controlled tunable fiber-optic attenuator that leverages the microfluidic electro-wetting effect, which enables a fine-tuning of the solid-liquid interface wetting angle to control the micro-reflector, thus regulating the lens fiber coupling efficiency. Theoretical calculations indicated an optical attenuation regulation effect of 0–45.0 dB in the voltage range of 0–30.0 V. Experimental results align closely with theoretical calculations, demonstrating an attenuation range of 0.59–43.0 dB within a voltage variation range of 0–25.0 V, with control accuracy of 0.56 dB. Our study unveils the potential for designing fiber-optic attenuators with varying tuning accuracy by precisely adjusting the solid-liquid interface wetting angle.

Study of polysterene based scintillator ageing in the DANSS experiment

DANSS is a spectrometer for reactor antineutrinos based on plastic scintillator. The sensitive volume of the detector is made of 2500 polystyrene based scintillator plates with wavelength shifting (WLS) fiber readout (strips). We present a study of the light yield of strips during 6.5 years of DANSS continuous running. Overall ageing at the rate 0.55 ± 0.05 (syst.) % per year is observed that is considerably smaller than in other similar experiments. We also observe the WLS fiber attenuation length shortening at the rate 0.26 ± 0.04(stat.) % per year.

Measurement of radiation induced attenuation in irradiated active fibers using optical frequency domain reflectometry

Radiation induced attenuation (RIA) is a major factor affecting the performance of fiber laser systems operated in adverse environments. To investigate the output characteristics of lasers with irradiated active fibers, measurement of detailed RIA profiles is required. Here, a novel method is proposed to explore the attenuation characteristics of irradiated active fibers using optical frequency domain reflectometry (OFDR), which enables propagation loss measurement by acquiring the spatial-resolved backscattered optical signals. With this technique, the RIA data of Yb-doped fibers (YDFs) under uniform radiation is derived by linear fitting of the OFDR traces. And, conventional optical transmission (OT) method is also exploited for comparison. Analysis show that the measured results of the two approaches are consistent. Then, the capability of OFDR is further verified for non-uniform RIA profile measurement of YDFs. For a pump bleached YDF, an upward parabolic RIA profile is attained by taking derivative of the smoothed polynomial fitting of the OFDR trace. Finally, the impacts of RIA profile on the output characteristics of Yb-doped fiber lasers are examined theoretically with a multiphysics thermal model, further validating the necessity of RIA profile measurement.

Experimental Study of the Airflow Field and Fiber Motion in the Melt-Blowing Process.

The melt-blowing process involves high velocity airflow and fiber motion, which have a significant effect on fiber attenuation. In this paper, the three-dimensional airflow field for a melt-blowing slot die was measured using the hot-wire anemometry in an experiment. The fiber motion was captured online using a high-speed camera. The characteristics of the airflow distribution and fiber motion were analyzed. The results show that the melt-blowing airflow field is asymmetrically distributed. The centerline air velocity is higher than that around it and decays quickly. The maximum airflow velocity exists near the die face, in the range of 130-160 m/s. In the region of -0.3 cm < y < 0.3 cm and 0 < z < 2 cm, the airflow has a high velocity (>100 m/s). As the distance of z reaches 5 cm and 7 cm, the maximum airflow velocity reduces to 70 m/s. The amplitude of fibers is calculated, and it increases with the increase in air dispersion area which has a significant influence on fiber attenuation. At z = 1.5 cm, 2.5 cm, 4 cm, and 5.5 cm, the average fiber amplitudes are 1.05 mm, 1.71 mm, 2.83 mm, and 3.97 mm, respectively. In the vicinity of the die, the fibers move vertically downward as straight segments. With the increase in distance from the spinneret, the fiber appears to bend significantly and forms a fiber loop. The fiber loop morphology affects the velocity of the fiber movement, causing crossover, folding, and bonding of the moving fiber. The study investigated the interaction between the fiber and airflow fields. It indicates that the airflow velocity, velocity difference, and dispersion area can affect the motion of fiber which plays an important role in fiber attenuation during the melt-blowing process.

The effect of frozen-in stress on fiber attenuation and a preparation method for ultra-low loss fiber

As the data-rate of the optical fiber communication system evolves to 400 Gb/s or even 1 Tb/s, higher requirements are put forward for transmission rate and repeater distance. To meet the requirements, further decreasing the optical fiber attenuation coefficient is one of the effective methods. In this paper, we did research on the relationship between the distribution of elements and frozen-in stress in the core layer and the cladding. Subsequently, their effect on optical fiber attenuation is also investigated. The results show that the co-doping of germanium, fluorine, and chlorine in the core layer can improve the stress matching between the core layer and the optical cladding. In addition, based on our research, the outer cladding with a high softening point can restrain the stress mismatch between the core layer and the optical cladding. Furthermore, the thickness of the second cladding will also affect the stress mismatch. Eventually, ultra-low loss fibers with the optimal attenuation of 0.156 dB/km at 1550 nm were prepared successfully by analyzing the stress distribution inside the optical fiber and adjusting the doping amount of germanium, fluorine, chlorine and other elements in the core layer, optical cladding, and outer cladding to maintain that the core layer and the optical cladding share the same stress.

Cost analysis of ultrawideband transmission in optical networks

We examine the cost associated with increasing traffic on a reference transport network for both single- and multiband systems, with a total transmission bandwidth ranging from 4.8 to 20 THz (S2 + S1 + C + L-band, where S2 and S1 are the two halves of the S-band). The number and cost of amplifiers, transceivers, and fibers are considered. To ensure stable transmission power and simplified network management, we take noise loading into account. The optimal combination of transmission bands—for each system—is evaluated based on the maximization of the capacity calculated from the minimum per-band generalized signal-to-noise ratio of each band. The results reveal that, despite the lower spectral efficiency due to the higher fiber attenuation and band MUX/DEMUX insertion losses, multiband systems can effectively reduce the number of fibers needed, thus postponing the deployment of new fibers. The most cost-effective solution depends on the fiber and S-band amplifier costs and the forecast of the required network capacity. When additional fibers are freely available or fiber costs are minimal, employing a C-band-only system proves to be the most economical choice. As fiber costs increase, additional bands gradually become more appealing, progressing from the C-band-only to the C + L-band, and then to the addition of half of the S-band (S1 + C + L-band) or the whole S-band (S2 + S1 + C + L). Furthermore, multiband transmission systems are more attractive when considering higher traffic loads. We also propose an optimal order of deployment of transmission bands in a pay-as-you-grow approach. The corresponding cost evolution demonstrates that this approach is a viable solution to mitigate excessive costs during the initial stages of a network operation, even though it leads to an increased number of fibers and transceivers used before all transmission bands are enabled. Additionally, we show that the S1- and S2-bands have worse optical performance, making them more suitable for shorter lightpaths. Consequently, operating the S-band in single-hop links and simplifying the add-drop multiplexer architecture could be beneficial.

Photobleaching Effects on the Radiation-Induced Attenuation of Germanosilicate Optical Fibers at Low Temperature

Photobleaching Effects on the Radiation-Induced Attenuation of Germanosilicate Optical Fibers at Low Temperature

Temperature Cycling Effects on Infrared Radiation-Induced Attenuation of Silica-based Optical Fibers

Temperature Cycling Effects on Infrared Radiation-Induced Attenuation of Silica-based Optical Fibers

Influence of Hydrogen on the Radiation-Induced Attenuation of Ge-doped Optical Fibers

Influence of Hydrogen on the Radiation-Induced Attenuation of Ge-doped Optical Fibers

Optimizing ODP Device Placement on FTTH Network Using Genetic Algorithms

Currently the problem of Optical Distribution Point (ODP) infrastructure is important in fiber to the home (FTTH) network access because ODP infrastructure development is no longer dependent on demand, so placing ODP manually without a systematic method can cause an increase in the value of optical fiber attenuation. on the length of the cable and cause the cable distribution to be irregular. This study aims to optimize the placement of ODP devices in PT BCV's FTTH network by using the Traveling Salesman Problem (TSP) scheme with the genetic algorithm (GA) approach and using hybrid GA, testing is carried out using Matlab software. Testing with development using Hybrid GA gets the best path with a fitness value of 28.6457 and a computation time of 89.93 seconds.

Comorbidity of cardiorespiratory and locomotor dysfunction following cervical spinal cord injury in the rat.

Cervical spinal cord injury interrupts supraspinal pathways innervating thoracic sympathetic preganglionic neurons and results in cardiovascular dysfunction. Both respiratory and locomotor functions were also impaired due to damages of motoneuron pools controlling respiratory and forelimb muscles, respectively. However, no study has investigated autonomic and somatic motor functions in the same animal model. The present study aimed to establish a cervical spinal cord injury model to evaluate cardiorespiratory response and locomotor activity in unanesthetized rats. Cardiovascular response and respiratory behavior following laminectomy or cervical spinal contusion were measured using noninvasive blood pressure analyzer and plethysmography systems, respectively. Locomotor activity was evaluated by an open-field test and a locomotor rating scale. The results demonstrated that mean arterial blood pressure and heart rate were significantly reduced in contused rats compared with uninjured rats at the acute injured stage. Tidal volume was also significantly reduced during the acute and subchronic stages. Moreover, locomotor function was severely impaired, evidenced by decreasing moving ability and locomotor rating scores from the acute to chronic injured stages. Retrograde neurotracer results revealed that cervical spinal cord injury caused a reduction in number of phrenic and triceps motoneurons. Immunofluorescence staining revealed a significant attenuation of serotonergic, noradrenergic, glutamatergic, and GABAergic fibers innervating the thoracic sympathetic preganglionic neurons in chronically contused rats. These results revealed the pathological mechanism underlying the comorbidity of cardiorespiratory and locomotor dysfunction following cervical spinal cord injury. We proposed that this animal model can be used to evaluate the therapeutic efficacy of potential strategies to improve different physiological functions.NEW & NOTEWORTHY The present study establishes a preclinical rodent model to comprehensively investigate physiological functions under unanesthetized condition following cervical spinal cord contusion. The results demonstrated that cervical spinal cord contusion is associated with impairments in cardiovascular, respiratory, and locomotor function. Respiratory and forelimb motoneurons and neurochemical innervations of sympathetic preganglionic neurons were damaged following injury. This animal model can be used to evaluate the therapeutic efficacy of potential strategies to improve different physiological functions.

Optical driving, spin initialization and readout of single SiV− centers in a Fabry-Perot resonator

Large-scale quantum communication networks require quantum repeaters due to the signal attenuation in optical fibers. Ideal quantum repeater nodes efficiently link a quantum memory with photons serving as flying qubits. Color centers in diamond, particularly the negatively charged silicon vacancy center, are promising candidates to establish such nodes. Inefficient connection between the color center’s spin to the optical fiber networks is a major obstacle, that could be resolved by utilizing optical resonators. Here, we couple individual silicon vacancy centers incorporated in a nanodiamond to a hemispherical, stable Fabry-Perot microcavity, achieving Purcell-factors larger than 1. We demonstrate coherent optical driving between ground and excited state with a Rabi-frequency of 330 MHz, all-optical initialization and readout of the electron spin in magnetic fields of up to 3.2 T. Spin initialization within 67 ns with a 80 % fidelity and a lifetime of 350 ns are reached. Our demonstration opens the way to realize quantum repeater applications.

FTTH NETWORK DISTURBANCE ANALYSIS BASED ON ATTENUATION AND RECEPTION POWER ON THE INDIHOME SINGKAWANG NETWORK

Optical fiber is a transmission medium that allows it to meet human needs to be able to transfer data faster because it uses light as a conductor. There is a damping problem in optical fiber, it needs to be accommodated so as to minimize the occurrence of attenuation in optical fiber. With this research, it can be known the magnitude of the value of a fiber optic transmission attenuation through the method of measuring attenuation values and receiving power at the customer's home using OPM, identifying fiber optic channel attenuation that affects the quality of internet services, and knowing the comparison of OPM measurement results with OT data reading. This study uses an analytical descriptive approach where the research will describe what it is about a variable that is processed, as well as the symptoms and conditions to be identified. So the results of the study can be obtained, namely, the amount of attenuation measured in the customer's home is influenced by the attenuation measured in ODP. Attenuation at ODP is small with an average optical power value of -18.39 dB, this makes attenuation in customers' homes, namely ONT, tend to be smaller with an average optical power value of -20.04 dB. There is an additional value of -1.65 dB per transmission. So it is known that the longer the cable used for fiber optic transmission, the greater the attenuation produced so that the optical power emitted by the sender will weaken along with the length of the cable. This is what will affect the quality of internet services.

Theoretical and experimental investigation of the steady-state power distribution in multimode step-index plastic optical fibers

In this work we have examined theoretically and experimentally the influence of mode coupling on steady-state distribution (SSD) in step-index plastic optical fiber (SI POF). Numerical and analytical solution of the PFE under steady-state conditions are compared to our experimental results. A numerical solution of the power flow equation (PFE) has been obtained by the explicit finite difference method (EFDM). We demonstrated that SSD in the SI POF is achieved at length of 140 m, which is much shorter length compared to the case with silica fibers. The reported results appear to be particularly important since none of the main optical properties of an optical fiber (attenuation, bandwidth) can be accurately determined until the transmitted optical power reaches its SSD, due to strong influence of mode coupling phenomena that occur during the transmission process. These results are important for employment of the SI POFs as a part of communication or sensory systems.

Optimization of signal‐to‐noise ratio of laser heterodyne radiometer

AbstractThe ground‐based laser heterodyne radiometer (LHR), which exhibits the advantages of small size, high spectral resolution, and easy integration, has been used for the remote sensing detection of several gases to meet a wide range of needs. This study aims to optimize the laser heterodyne system for detecting CO2 gas by focusing on existing research. Firstly, using the all‐fiber laser heterodyne detection system built by our research group, the power spectrum associated with the radio frequency signals of the detection system is discussed under different conditions: under no irradiation, under sunlight only, under sunlight and laser irradiation at the absorption peak, and under a filter in the spectrum range of 185–270 MHz. Signal‐to‐noise ratios (SNRs) of the high‐resolution spectrum have been obtained using different filter bands of 185–270, 225–270, and 225–400 MHz. Finally, the filter in the 225–270 MHz band, which has the highest SNR, is selected. Consequently, the resolution is improved and the system is further optimized. Furthermore, an optical fiber attenuator is used to change the power of the local oscillator light entering the system, and hyperspectral spectra with varying percentages of input energy and total energy are obtained. When the laser attenuation reaches 40%, the optimal SNR of the system is 486 and can be further improved to meet the expected requirements. This study will provide insights for improving the applicability of laser heterodyne technology in atmospheric sounding.

Performance Analysis of Fiber Attenuation in Passive Optical Networks

Performance Analysis of Fiber Attenuation in Passive Optical Networks