Apodized Fiber Bragg Grating Research Articles

Chirped apodized fiber Bragg gratings inverse design via deep learning

Overcoming inverse design problems in fiber Bragg gratings (FBGs) can be challenging due to the significant nonlinearity of the problem and the intricate relationship between structural properties and optical characteristics. Here, we present a novel artificial intelligence-based approach that effectively addresses these challenges. We introduce a methodology centered on applying deep learning (DL) to estimate the reflective spectrum of FBGs. The results highlight DL’s exceptional capability in designing chirped apodized FBGs, with our model demonstrating significantly enhanced computational efficiency relative to traditional numerical simulations. Notably, our DL-based approach exhibits the remarkable ability to tackle the inverse design challenges of FBGs, thereby eliminating the reliance on trial-and-error or empirical methodologies. The predictive losses for both the forward and inverse models are impressively minimal, with low loss values of 2.2 × 10-2 and 1.6 × 10-2, respectively. The FBG configurations derived via DL are ideally suited for optical communications, heralding significant advancements in all-optical signal processing.

Optimization and analysis of apodized fiber Bragg grating properties for quasi-distributed sensing

An apodized fiber Bragg grating (FBG) is introduced with a proposed apodization function for the effective quasi-distributed sensing estimation of the temperature and the strain. FBG features such as reflectivity, side lobes, and bandwidth have been optimized for the designed apodized grating to upgrade the effectiveness of FBG for properly measuring the variations in the Bragg wavelength. Based upon the simulation, a comparative analytical study on FBG properties with different apodization function profiles has been demonstrated to achieve the optimum profile with high reflectivity, narrow bandwidth and minimal range of side lobes for quasi-distributed sensing estimation of parameters. A strong linearity has been noted for the sensitivity of designed FBG with different apodization profiles for the temperature and the strain estimation subsequently. It has been reported that the obtained sensitivity of measurands for the FBG with proposed apodization profile are higher as compared with the other profiles. The wavelength division multiplexing (WDM) based quasi-distributed network of four optimized FBGs have been implemented for different apodization profiles to illustrate the impact of apodization to prevent overlapping between neighbouring FBG spectrums in the sensing network with spatial resolution of 2 nm. The maximal detectable temperature/strain sensitivity estimation of 153 °C/1439 μϵ have been obtained for the proposed apodized FBG along with minimal detectable temperature/strain ranges of −102 °C/−1345 μϵ in the quasi-distributed network. The achieved ranges with optimum resolution can be implemented effectively in quasi-distributed based sensing application for condition observation of civil infrastructures in any complex circumstances.

Optical fiber fronthaul segment in open radio access 5G networks: enhanced performance utilizing AFBG

In open Radio access network (oRAN) 5G networks, a fronthaul segment between virtual Distribution unit (vDU) edge cloud and other external Remote radio units (RRUs) sites is very important to transmit high data rate to achieve 5G requirements. Performance parameters such as Quality factor (Q-factor) and Bit error rate (BER) of an optical fiber fronthaul segment are the main important parameters to enhance latency and bit rate. An Apodized fiber bragg grating (AFBG) is utilized with different apodization profiles to optimize linewidth of an optical signal leading to enhance performance. The designed AFBG is used with a data rate of 25 Gb/s optical Ethernet module at the vDU edge cloud to optimize the linewidth of the optical signal between the vDU and the RRU in the fronthaul optical fiber segment. The AFBG is investigated at different connections pre, post, and symmetrical connections, where different apodization functions are used in the AFBG design. It is found that the best results for the maximum Q-factor and minimum BER are 9.2 and 2.72e− 21, respectively, obtained from uniform function in the symmetrical connection. Finally, the proposed model linewidth is 0.408 nm, which is better than 1.56 nm that is evaluated by related work.

Performance Analysis of Gaussian Apodized Fiber Bragg Grating (GA-FBG) Dispersion Compensator for a Long Haul Optical Fiber Link

This examination gives a complete analysis of the GA-FBG, a generally involved grating for dispersion compensation across a 150 kilometer optical link, from each point. The essential objective of this study is to distinguish how long the GA-FBG can work as an independent dissemination reimbursement gadget and how well it acts in various compensation settings. In this review, the GA-FBG is utilized as an option in contrast to the exorbitant Dispersion-Reimbursing Fiber inside the association to give a more safe optical link. The investigation delves into three specific compensation methods and studies the GA-FBG grating boundaries in light of the relative abundance of real imperatives associated with a Fiber Bragg Grating (FBG) in the design phase. Using a Piece Blunder Rate analyzer to examine the streamlined links' exhibition highlights allows us to evaluate their productivity. Results show that the GA-FBG exhibits a common dispersion compensation adequacy when the link's channel boundaries are tuned. Using gearbox over distances easily exceeding 500 km, the balanced compensation strategy delivers a remarkable Q-factor respect. Utilizing OptiSystem programming, we validate the proposed system's functional viability. The results of our study indicate that the GA-FBG is capable of efficiently counteracting dispersion, leading to an optical link that is both more economical and effective, with significant potential for extended transmission ranges.

Design of an Apodized Fiber Bragg Grating Sensor for Sensitivity Analysis of Physical Parameters using Support Vector Machine

Design of an Apodized Fiber Bragg Grating Sensor for Sensitivity Analysis of Physical Parameters using Support Vector Machine

All-optical modulation of Fano-like resonances in apodized fiber Bragg grating using Er/Yb doped fiber

A novel all-optical scheme for fast modulation of Fano-like resonance using Er/Yb doped fiber (EYDF) is proposed and demonstrated experimentally. In the integrated system, an apodized fiber Bragg grating (AFBG) is inserted into one arm of the fiber Mach–Zehnder interferometer (MZI), and the asymmetric Fano-like resonances is generated by the interference between the MZI mode and AFBG mode. In addition, a section of EYDF is inserted into the other arm of the MZI to control the phase difference between the two arms of the MZI. By adjusting the power of optical pump applied to the EYDF, the transmission spectrum lineshapes of the integrated device can be effectively modulated into asymmetric Fano-like resonances, symmetric transmission dip or electromagnetically induced transparency-like resonances, which has a fast response speed. The proposed all-optical Fano-like modulation scheme is simple in structure, and has advantages of remote control and long-term stability, providing potential applications in the fields of fast and slow light, optical filters and fiber sensing.

Enhanced sensing performance of tapered profile in the apodized fiber Bragg grating for detection of cancerous cells utilizing their refractive index.

Tapered profiles are introduced in Bessel and Blackman apodized fiber Bragg grating, and their sensing performance is theoretically estimated. Reflectivity equation of proposed apodized tapered profiles is obtained using transfer matrix method and coupled mode theory. Since the effective refractive index (RI) of proposed waveguides varies with core radius therefore amplitude distribution and penetration depth of light in surroundings are modified. It is found that the exponential tapered profile with Bessel apodization shows a higher sensitivity of 682.5 nm/RIU, detection accuracy of 3858.45, and quality parameter 1718.02/RIU with minimum full width at half maxima (FWHM) 0.3972 nm of the reflection spectra. The spectral response of the tapered fiber Bragg grating is also analyzed through a group delay study. Again, exponential profile was found to be particularly effective, producing less group delay ripples 2.98 ps and is maximum slope of 42.43°. Hence, exponential tapered profile is demonstrated for detection of cancer cells lies between the refractive index of 1.3333-1.4412.

Sensitivity Enhancement of Apodized Fiber Bragg Grating for Temperature Measurement

Sensitivity Enhancement of Apodized Fiber Bragg Grating for Temperature Measurement

Theoretical investigation of the impact of apodized fiber Bragg grating and machine learning approaches in quasi-distributed sensing

An apodized fiber Bragg grating (FBG) is designed to investigate the impacts of side lobe elimination in quasi-distributed sensing for the estimation of measurands (like temperature and strain) to assess the condition of civil structures, such as bridges. The adjacent FBG spectrums may overlap with each other because of the impacts of temperature and strain due to the presence of a high range of side lobes in a quasi-distributed sensing network. Therefore, elimination of side lobes is necessary, by introducing a method of apodization. The sensitivity of the designed apodized FBG is estimated by analyzing the variations in the Bragg wavelength due to the impacts of temperature and strain. The changes in Bragg wavelength due to the measurands can affect the grating period and the grating index of the FBG. The period of the grating and the grating index of the FBG are simultaneously varied by temperature and strain. To measure the physical parameters effectively, it is essential to distinguish whether the changes in the Bragg wavelength are owing to the impacts of temperature or to the impacts of strain. The effect of cross-sensitivity between the temperature and the strain is a key problem in any FBG-based sensing application as both the measurands can affect the Bragg wavelength. In this work, machine learning methods (the support vector machine, K-nearest neighbors, logistic regression, naïve Bayes, decision tree, and ensemble models) are introduced to differentiate between the effects of temperature and strain on a single Bragg wavelength shift measurement. An artificial neural network is used for the predictive analysis of physical parameters, to identify any measurements of potential concern. It has been noted that the performance of the proposed ensemble model is higher compared to other models for the classification of temperature and strain.

Sensing performance of apodized fiber Bragg gratings having linearly tapered profile

Sensing performance of apodized fiber Bragg gratings having linearly tapered profile

Photonic reservoir computing using a self-injection locked semiconductor laser under narrowband optical feedback.

Photonic time-delay reservoir computing (TDRC) using a self-injection locked semiconductor laser under optical feedback from a narrowband apodized fiber Bragg grating (AFBG) is proposed and numerically demonstrated. The narrowband AFBG suppresses the laser's relaxation oscillation and provides self-injection locking in both the weak and strong feedback regimes. By contrast, conventional optical feedback provides locking only in the weak feedback regime. The TDRC based on self-injection locking is first evaluated by the computational ability and memory capacity, then benchmarked by the time series prediction and channel equalization. Good computing performances can be achieved using both the weak and strong feedback regimes. Interestingly, the strong feedback regime broadens the usable feedback strength range and improves robustness to feedback phase variations in the benchmark tests.

Femtosecond laser inscribed fiber Bragg gratings based on precise spatial apodization.

Plane-by-plane femtosecond laser fabricated apodized fiber Bragg gratings (FBG) are demonstrated for the first time, to the best of our knowledge. The method reported in this work provides a fully customizable and controlled inscription that can realize any desired apodized profile. By using this flexibility, we experimentally demonstrate four different apodization profiles (Gaussian, Hamming, New, Nuttall). These profiles were chosen to evaluate their performance with regard to the sidelobe suppression ratio (SLSR). Usually, a higher reflectivity of a grating fabricated with a femtosecond laser will result in a greater difficulty to achieve a controlled apodization profile due to the nature of the material modification. Therefore, the goal of this work is to fabricate high-reflectivity FBGs without sacrificing the SLSR and provide a direct comparison with apodized low-reflectivity FBGs. In our weak apodized FBGs, we also consider the background noise introduced during the femtosecond (fs)-laser inscription process which is fundamental when multiplexing FBGs within a narrow wavelength window.

Novel Apodized Fiber Bragg Grating Applied for Medical Sensors: Performance Investigation

Sensors play an important role in shaping and monitoring human health. Exploration of methods to use Fiber Bragg Grating (FBG) with enhanced sensitivity has attracted great interest in the field of medical research. In this paper, a novel apodization function is proposed and performance evaluation and optimization of the same have been made. A comparison was conducted between various existing apodization functions and the proposed one based on optical characteristics and sensor parameters. The results evince the implementation of the proposed apodization function for vital sign measurement. The optical characteristics considered for evaluation are Peak Resonance Reflectivity level, Side Lobes Reflectivity level and Full Width Half Maximum (FWHM). The proposed novel apodization novel function has better FWHM, which is narrower than the FWHM of uniform FBG. Sensor characteristics like a quality parameter, detection accuracy and sensitivity also show improvement. The proposed novel apodization function is demonstrated to have a better shift in wavelength in terms of temperature and pulse measurement than the existing functions. The sensitivity of the proposed apodized function is enhanced with a Poly-dimethylsiloxane coating of varying thickness, which is 6 times and 5.14 times greater than uniform Fiber Bragg grating and FBG with the proposed novel apodization function, respectively, enhancing its utilization in the field of medicine.

Design and performance investigation of Gaussian apodized FBG as hybrid dispersion compensation module for long-haul optical link

Abstract A hybrid dispersion compensation module design, using Gaussian apodized fiber Bragg grating and 11 km long dispersion compensation fiber, is proposed for a 111 km long optical link. The proposed module is examined successively with four different chirping techniques. Further, the design is investigated thoroughly in pre-, post- and symmetrical-compensation modes. The performance characteristics of the optimized links are evaluated orderly by quality-factor (Q-factor) values, Eye-diagram and pulse width reduction percentage (PWRP). To further enhance the Q-factor value, optimal parameters of FBG are determined comprehensively by varying the effective refractive index and grating length values. The results show that the proposed dispersion compensation module using Gaussian apodized fiber Bragg grating works well for the quadratic chirping technique. The Q-factor values attained in pre-, post- and symmetrical-compensation modes are 40.5, 49 and 50, respectively, far higher than the values proposed in the literature to date. Thus the proposed technique is best suited for symmetrical and post-compensation modes. The workability of the proposed system is verified using OptiSystem software.

Dispersion compensation using cascaded apodized CFBGs under MTDM transmission technique: Enhanced system performance

This study focuses on compensating chromatic dispersion affecting the propagated signal in a standard single mode optical fibers (SSMFs). We propose a model that consists of an identical four stages cascaded linear chirped apodized fiber Bragg gratings (CFBGs) in a post-compensation scheme under Maximum Time Division Multiplexing (MTDM) technique. MTDM is free of the limitations resulting from the fiber nonlinear effects. It, thus, effectively utilizes optical wavelength and operating in various network of different distances and capacities. Therefore, MTDM is designed to be used in the high-capacity and high-speed transmission systems. The evaluation of the proposed model performance is performed through a comparative study using different connections and the most common apodization functions. This comparative study includes three cases based on the used connection scheme. A 10 Gbps Wavelength Division Multiplexing (WDM) 70 km link is simulated under ordinary operating parameters. Optisystem 7.0 is used for the simulation and evaluation process, in terms of two metrics which are quality factor (Q-factor) and bit error rate (BER). In the pre-compensation scheme, the highest results are: Q-factor = 7.664 and BER = 8.99 × 10–15, using the raised cosine apodization function. Using the raised sine apodization in the post-compensation connection realizes the best performance: Q-factor = 8.58 and BER = 4.77 × 10–18. In the symmetrical-compensation scheme and using the raised sine apodization, the proposed model attains the highest Results: Q-factor = 7.49 and BER = 3.53 × 10–14. The proposed model achieves at least 92.6% improvement in BER and 3.75% in Q-factor over the related works. The study is a simulation work and is performed through Optisystem ver. 7.

Spectral response of apodized fiber Bragg gratings as strain and temperature sensor

In this paper, the spectral response of uniform and apodized (Gaussian, hyperbolic tangent, apod1, sine, and raised sine) FBGs is analyzed for sensing applications. The reflectivity at Bragg wavelength as well as for sidelobes was assessed as a function of grating length and apodization profiles. The FBG strain and temperature sensors were simulated and a linear response between applied strain or temperature and the wavelength shift is observed. The results indicate that the sensitivity of the sensor is found to be affected both by the grating length and apodization type. The typical strain and thermal sensitivity values are 1.223 pm/[Formula: see text] and 13.60 pm/[Formula: see text]C, respectively. The results suggest that Gaussian, sine, and raised sine profiles have lower sidelobe strength and reliable sensitivities. The key finding from this study specifies that the ideal grating length must be preferably between 5 and 10 mm for a good sensing behavior.

High-precision Microwave Frequency Measurement Based on Stimulated Brillouin Scattering With Simple Configuration

We propose and implement a microwave frequency measurement (MFM) scheme based on stimulated Brillouin scattering (SBS) and an apodized fiber Bragg grating (AFBG), achieving high accuracy in a wide range of measurement with a highly simplified configuration. By sweeping a reference frequency during SBS process, a frequency-to-power mapping between the reference frequency and the monitored output optical power of the MFM system is established. Unknown frequencies can be identified through a specific numerical relationship among the unknown frequency, reference frequency, and Brillouin frequency shift (BFS). The transmission and reflection properties of the AFBG are exploited to offer pump light and probe light simultaneously for SBS process, thereby reducing complexity of the MFM system. It can be derived theoretically that all frequencies larger than one BFS can be measured except for 3/2 BFS. This measurement blind spot can be eliminated by utilizing two segments of single-mode fibers with different BFSs. A measurement error of less than ±1 MHz within 10.68 GHz to 20 GHz is achieved in a proof-of-concept experiment of the proposed MFM approach. This method has also been proved to be applied to dual microwave frequency measurements.

Strain sensing in underwater acoustics with a hybrid π-shifted FBG and different interrogation methods

Although Piezo-Electric Transducers (PZT) hydrophones are widely accepted and technologically mature in the field of Acoustic Emissions (AE) strain sensing underwater, optical fiber-based sensors are gaining more attraction due to their multiplexing capability, small size, high resolution, high sensitivity and immunity to Electromagnetic Interference (EMI). In this paper, we propose a hybrid Fiber Bragg Grating (FBG) system based on combining two apodized FBGs (AFBGs); named Nuttall and Cos8, separated by a pi-phase shift to apply it for underwater strain sensing. This combination results in optimum performance in terms of the reflection properties including high peak reflectivity, narrow Full Width at Half Maximum (FWHM), remarkable side lobes suppression, high roll-off rate, good Ripple Factor (RF) and high Detection Accuracy (DA) as well. In addition, an excellent multiplexing capability, high temperature and strain sensitivities and a stable operation over increased temperatures, strain and pressure levels (up to 250 °C, 1000 µstrain and 100 MPa) are achieved. Moreover, mechanical analysis and comparisons revealed that the Polymer Optical Fiber (POF) recorded the highest sensitivity among other fiber types and their coatings with a value of 1.43 pm/µstrain, making it applicable in the strain sensing in underwater acoustics. Furthermore, in this work, a detailed comparative study is performed between several types of interrogators targeting an optimum interrogator for the strain sensing application in underwater acoustics. The obtained results reveal that the linear edge absorption filter detection method achieves better results among the other types. But, unfortunately, when talking about the multiplexing capability, it shows a remarkable failure. Whereas, the Mach–Zehnder. Interferometry (MZI) comes in the second place with higher resolution range (103–104) with tunable sensitivity, fast measurement speed, good long-term stability, high multiplexing capability and medium cost. Accordingly, it could be applicable in the application understudy.

Performance Optimization of Apodized FBG Biomedical Sensor for Variation in Temperature and Presence of Noise

In this work, comprehensive analysis on single and dual mode, uniform and apodized Fiber Bragg Grating (FBG) based gas concentration measurement sensor performance in the presence of noise and temperature variations is presented. Different scenarios are formulated. Firstly, the indirect sensing method for gas concentration measurement is presented, followed by the discussion on single and dual mode uniform FBG sensor design. Thereafter single and dual mode Gaussian apodized FBG sensor design and its pros and cons are discussed. The effect of temperature variations and noise on FBG sensor is also discussed. Afterwards as per referred literature the simulation results for uniform and apodized FBG in the presence or absence of noise, temperature variations and strain applications are validated. The quantitative analysis shows that the single mode apodized FBG has highest side lobes suppression ratio which is 88.21%. In terms of FWHM single mode apodized FBG has narrowest bandwidth of amplitude 0.18. While dual mode apodized FBG has highest reflectivity, that is, −0.20571. It is observed that reflection spectrum of uniform FBG sensor contains large strength of side lobes at adjacent wavelength. Moreover, the dual mode FBG sensor performance is more affected by variation in temperature and noise but dual mode FBG sensor works better as compared to single mode FBG sensor in context of minimum side lobes, high absorption depth and enhanced reflectivity. The presented investigation will be helpful to prescribe the correct amount of dosage for biomedical application. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Point-by-point inscription of chirped apodized fiber Bragg gratings for application as ultrashort pulse stretchers

There are special requirements for chirped fiber Bragg gratings used as stretchers in ultrafast fiber lasers. The benefits of fabricating fiber stretchers by the femtosecond point-by-point single-shot technique are described. For the first time, apodization and arbitrary nonlinear chirp are embedded in chirped fiber Bragg gratings point-by-point inscription process. A significant reduction of the amplitude ripple of the grating reflection spectrum is demonstrated.