Fiber Optic System Research Articles

Remote accessible/fully controllable fiber optic systems laboratory design and implementation

AbstractIn private and expensive experimental laboratory studies, there are problems such as difficulty in accessing measuring devices and materials, space and time problems, and insufficient technical support due to the need for expertise. In this study, a fiber optic laboratory (FOL), which can be used for educational and scientific research purposes, has high installation costs and has difficulty in accessing devices, was designed and realized as a remote accessible/fully controllable. All devices in the proposed laboratory have been virtualized on the MATLAB App Designer platform, and communication protocols have been defined and made remotely accessible and controllable. In the proposed system, the user accessed remotely can perform all device controls, record the measurement results, take the measurement average as much as he wants to increase the measurement accuracy, monitor the experimental setup with a camera, and receive expert support. Afterward, a sample experiment was set up on the system and the results were compared. The proposed laboratory has a high potential to establish international collaborations in remote/flexible work and scientific research. Finally, a scale was applied to FOL undergraduate, graduate, and doctoral student groups. The Cronbach α coefficient showing the reliability of the applied model was found to be .934.

Boosting SNR of cascaded FBGs in a sapphire fiber through a rapid heat treatment.

This Letter reports the performance of femtosecond (fs) laser-written distributed fiber Bragg gratings (FBGs) under high-temperature conditions up to 1600°C and explores the impact of rapid heat treatment on signal-to-noise ratio (SNR) enhancement. FBGs are essential for reliable optical sensing in extreme temperature environments. Comprehensive tests demonstrate the remarkable performance and resilience of FBGs at temperatures up to 1600°C, confirming their suitability for deployment in such conditions. The study also reveals significant fringe visibility improvements of up to ∼10 dB on a 1-m-long sapphire optical fiber through rapid heat treatment, representing a first-time achievement to the best of our knowledge. These enhancements are vital for improving the SNR and overall performance of optical fiber systems in extreme temperatures. Furthermore, the research attains long-term stability for the cascaded FBGs over a 24-hr period at 1600°C. This research expands our understanding of the FBG behavior in high-temperature environments and opens avenues for developing robust optical fiber systems for energy, aerospace, oil and gas, and high-temperature distributed sensing applications.

Compensating Chromatic Dispersion and Phase Noise using Parallel AFB-MBPS For FBMC-OQAM Optical Communication System

Filter Bank Multi-Carrier Offset-QAM (FBMC-OQAM) is one of the hottest topics in research for 5G multi-carrier methods because of its high efficiency in the spectrum, minimal leakage in the side lobes, zero cyclic prefix (CP), and multiphase filter design. Large-scale subcarrier configurations in optical fiber networks need the use of FBMC-OQAM. Chromatic dispersion is critical in optical fiber transmission because it causes different spectral waves (color beams) to travel at different rates. Laser phase noise, which arises when the phase of the laser output drifts with time, is a major barrier that lowers throughput in fiber-optic communication systems. This deterioration may be closely related among channels that share lasers in multichannel fiber-optic systems using methods like wavelength-division multiplexing with frequency combs or space-division multiplexing. In this research, we use parallel Analysis Filter Bank (AFB) equalizers in the receiver part of the FBMC OQAM Optical Communication system to compensate for chromatic dispersion (CD) and phase noise (PN). Following the equalization of CD compensation, the phase of the carriers in the received signal is tracked and compensated using Modified Blind Phase Search (MBPS). The CD and PN compensation techniques are simulated and analyzed numerically and graphically to determine their efficacy. To evaluate the FBMC's efficiency across various equalizers, 16-OQAM is taken into account. Bit Error Rate (BER), Optical Signal-to-Noise Ratio (OSNR), Q-Factor, and Mean Square Error (MSE) were the primary metrics we utilized to evaluate performance. Single-tap equalizer, multi-tap equalizer (N=3), ISDF equalizer with suggested Parallel Analysis Filter Banks (AFBs) (K=3), and MBPS were all set aside for comparison. When compared to other forms of Nonlinear compensation (NLC), the CD and PN tolerance attained by Parallel AFB equalization with MBPS is the greatest.

Mueller matrix analysis of spun wave plate for arbitrary SOP conversion.

The developments in polarized light have spawned a multitude of novel applications in optical fiber systems, but the design and fabrication of practical fiber wave plates with high degree of integration still remain a challenging issue. To address this problem, an all-fiber spun wave plate (SWP) for arbitrary state of polarization (SOP) conversion is proposed in this work, and its principle is analyzed with Mueller matrix. Simulations are conducted to exhibit the arbitrary SOP conversion capability of the proposed SWP, and two key parameters, including the maximum spinning rate (ξmax) and linear birefringence (δ), are investigated for efficient conversion of desired SOP. Different functions to increase the spinning rate ξ from 0 to ξmax, computational efficiency and accuracy related to N are discussed in detail. Furthermore, the depolarization effect caused by retardation of SWP is also considered. The results of this research suggest that the proposed SWP exhibits promising performance in arbitrary SOP conversion, and the meticulous analysis of the numerical computation, design, and implementation of SWP presented in this work can provide novel insights for devloping fiber wave plates.

Optical fiber systems performance signature based on dispersion compensated methods in dense wavelength division multiplexing systems

Optical fiber systems performance signature based on dispersion compensated methods in dense wavelength division multiplexing systems

Temperature Demodulation for an Interferometric Fiber-Optic Sensor Based on Artificial Bee Colony–Long Short-Term Memory

Demodulation methods play a critical role in achieving high-performance interferometric fiber-optic temperature sensors. However, the conventional passive 3 × 3 coupler demodulation method overlooks certain issues, such as the non-1:1:1 splitting ratio of the coupler, resulting in a non-ideal phase difference in the three output interference signals. These problems significantly impact the measurement results of interferometric temperature sensors. In this paper, we propose a novel arc-tangent method based on a 3 × 3 coupler and a demodulation algorithm combining long short-term memory (LSTM) with an artificial bee colony (ABC). The arc-tangent method is employed to enhance the input phase signal of the ABC-LSTM network model and establish a nonlinear mapping between the phase signal and temperature, effectively preventing the influence of the spectral ratio and phase difference of the 3 × 3 coupler on temperature demodulation. The proposed ABC-LSTM method achieves high-resolution measurements with an interval of 0.10 °C, and the absolute error is below 0.0040 °C within the temperature range of 25.00–25.50 °C. To demonstrate the stability and adaptability of the proposed method under long-term constant temperature conditions, we conducted measurements for approximately three hours in a controlled temperature environment set at 25.00 °C. Experimental results indicate that the maximum error of LSTM-ABC method remains around 0.0040 °C, outperforming the conventional algorithm (0.0095 °C). Furthermore, when comparing the average error values of the conventional passive 3 × 3 coupler method (0.0023 °C), LSTM model (0.0019 °C), and ABC-LSTM model (0.0014 °C), it is evident that the demodulation results of the ABC-LSTM method exhibit the highest level of stability. Therefore, the ABC-LSTM method enhances the accuracy and reliability of interferometric fiber-optic temperature-sensing systems.

Microsurgery of chronic laryngeal diseases using fiber optic lasers. A review

Background. The treatment of chronic diseases of the larynx is an urgent issue. Chronic larynx masses account for up to 5570% of the upper respiratory tract proliferative diseases. The incidence of vocal apparatus disorders is stable due to increased load on the vocal apparatus, neuro-emotional stress, non-compliance with voice hygiene (smoking, alcohol consumption), nasal and pharyngeal inflammatory diseases, sensibilization, and gastrointestinal disorders. Dysphonia, voice timbre changes, and vocal fatigue are presented in 712% of otorhinolaryngologist patients. Delayed treatment of chronic larynx diseases can lead to upper respiratory obstruction, reduced exercise and self-care tolerance, and disablement in people with voice and speech professions.
 Aim. To address current treatment methods for chronic diseases of the larynx. Modern surgical and non-surgical treatments of chronic larynx diseases aim to restore voice quality and respiratory function. Over the past 50 years, laser-assisted phonosurgery has gained popularity due to the many benefits of biological tissue exposure to electromagnetic energy and low rates of intra- and postoperative complications.
 Materials and methods. The literature review was performed using electronic medical libraries and professional printed papers. According to local and foreign data, laryngeal laser surgery is highly precise, minimally invasive, associated with no blood loss, and highly effective. Historically, CO2 laser has been used for the longest time in laryngeal surgery. Modern medical technology has recently introduced surgical systems with novel technicalities for clinical use. In such devices, the laser energy is transmitted through a flexible optical fiber instead of a mirror system, as in the CO2 laser, which has made new surgical high-energy systems more affordable for equipping medical institutions. Currently, the following fiber-optic laser systems are most often used to treat chronic diseases of the larynx: potassium-titanyl-phosphate, diode laser, and "blue" laser with a wavelength of 445 nm.
 Results. The literature review and analysis of surgical treatment outcomes using fiber-optic laser devices in patients with chronic larynx diseases showed high safety and effectiveness of modern treatments, providing fast recovery of voice and respiratory function.
 Conclusion. The development of laser devices, including domestic ones, with new wavelengths, makes it possible to work in contact mode in an inert gas environment, which opens up new opportunities for phonosurgery.

End-to-End Deep Learning of Joint Geometric Probabilistic Shaping Using a Channel-Sensitive Autoencoder

In this paper, we propose an innovative channel-sensitive autoencoder (CSAE)-aided end-to-end deep learning (E2EDL) technique for joint geometric probabilistic shaping. The pretrained conditional generative adversarial network (CGAN) is introduced in the CSAE which performs differentiable substitution of the optical fiber channel model under variable input optical power (IOP) levels. This enables the CSAE-aided E2EDL to design optimal joint geometric probabilistic shaping schemes for optical fiber communication systems at varying IOPs. The results of the proposed CSAE-aided E2EDL technique show that for a dual-polarization 64-Gbaud signal with a transmission distance of 5 × 80 km, when the modulation format is a 64-quadrature amplitude modulation (QAM) or a 128-QAM, the maximum generalized mutual information (GMI) level learned via CSAE-aided E2EDL is 5.9826 or 6.8384 bits/symbol under varying IOPs, respectively. In addition, the pretrained CGAN, as a substitution for optical fiber transmission model, accurately characterizes the distortion of signals with different IOPs, with an average bit error ratio (BER) difference of only 1.83%, an average mean square error (MSE) of 0.0041 and an average K-L divergence of 0.0046. In summary, this paper delivers new insights into the application of E2EDL and demonstrates the feasibility of joint geometric probabilistic shaping-based E2EDL for fiber optic communication systems with varying IOPs.

Integrated Sensor-Optics Communication System Using Bidirectional Fiber and FSO Channels and Hybrid Deep Learning Techniques.

This paper introduces a new bidirectional integration approach that combines fiber sensor/free space optics (FSO) communication using an intensity and wavelength division multiplexer (IWDM) techniques-based long-distance fiber Bragg grating (FBG) sensor strain-sensing system. By implementing coarse wavelength division multiplexing (CWDM), the system achieves the simultaneous transmission of optical communication and fiber optical sensor (FOS) sensing signals, resulting in a highly capable, flexible, and cost-effective solution. The proposed FSO transmission technique addresses complex fiber cable installation concerns with topographical limitations. This bidirectional structure ensures the reliability and stability of the long-distance FBG sensor system, supported by extensive research and experimentation. A hybrid stacked gated recurrent units and long short-term memory (SGRU-LSTM) model is proposed to enhance strain measurement accuracy by predicting and measuring the central wavelength of overlapped strain-sensing FBG sensor signals. The results demonstrate the superiority of the proposed model in peak wavelength detection accuracy. The primary benefit of integrating communication and sensing is the significant reduction in construction costs by eliminating the requirement for two individual fiber optic systems, as the integration allows for a single system to fulfill both functions, resulting in more efficient and cost-effective implementation. Overall, this paper contributes to advancing long-distance FBG sensor systems by integrating fiber sensor/FSO communication and deep learning techniques, improving transmission distance, multiplexing capacity, measurement accuracy, system survivability, and cost-effectiveness.

Linearly polarized high sub-mode excited long-beaked fiber optic transmission and tracking particulate system

Micro/nano optical fibers are playing an increasingly important role in the fields of targeted drug therapy and biological cell analysis. To achieve fast and stable particle delivery, we designed a long beak-shaped fiber probe that not only increases the fiber optical field gradient force but also enhances the evanescent field around the probe. The evanescent field at the side of the fiber is further enhanced by exploiting the symmetrically distributed four-wave flap mode field of the linearly polarized high sub-mode in the weakly guided fiber, thus ensuring stable particle capture in the axial direction while improving the stability of lateral capture. We conducted a series of experiments using a long-beaked micro-nano fiber in LP21 mode to deliver polystyrene particles, and the results show that the probe can deliver particles rapidly at low input power, verifying the superiority of the long-beaked fiber probe. Finally, we built an FPI interference model to monitor the transport position of the particles in real-time. By processing the interference fringes, we plotted the motion profile of the particles, which helps to further manipulate the motion of the particles.

Recent advancement in composite material structurally integrated fibre optic damage assessment system

The idea of using fractures as guiding markers for the implantation of optical fibre implants, serving as sensors to detect damage, has been advanced by numerous specialists across numerous industries. This method examines impact damage in depth, including its underlying causes and outcomes. It has been found that crucial matrix cracking caused by stress and shear might act as a warning sign for errors in embedded systems. The discussion includes the most recent developments in sensor technology and their possible uses. The evaluation of any systemic effects that may result from using such a technique is another crucial component. The results of an early-stage assessment system that used fibre optic technology to assess damage in an aircraft wing's leading edge are presented in this study. A thorough literature review is also done to investigate how embedded sensors affect the characteristics of materials. Although it might not have all the features of computer-aided design (CAD) software, its simplicity makes it a good option for making simple prototypes of transparent structures. Before investing money in more complex projects, this economical strategy allows for a preliminary investigation. During conduction of the experiments, our results show that Kevlar/epoxy panels show resistance to damage unless impacts are specifically focused on the implanted optical fibres. The fragility of these optical fibres can be altered strategically to fit particular applications. It demonstrate the capability of modifying the damage sensitivity of optical fibres through our work. This makes it possible for us to identify the root causes and efficiently track the development of damage zones in response to stress loading.

Slope Monitoring of a Road Embankment by Using Distributed Optical Fibre Sensing Inclinometer

Distributed Optical Fibre Sensor (DOFS) is a versatile sensor considering that it can be used to measure various parameters, such as detection of small strains over large areas and long distances. The application of DOFS is currently being explored as an early warning system, particularly for slope movement detection. In this paper, an embankment slope at Sungai Rual, Jeli, Kelantan, Malaysia was selected to determine the best monitoring layout for landslide detection. Two methods of installation for vertical Fibre Optic (FO) inclinometers (using conventional casing with a special grove) were installed to monitor subsurface horizontal ground movements. The first method of FO inclinometer installation uses concrete (grade 35) grouting, and the second method uses a bentonite mixture. It was found that the first method was unsuccessful due to the fibre breakage during the hardening process of concrete and hence not recommended. However, the measurement was successfully taken for the bentonite mixture method. The displacement reading was taken using both the FO and conventional inclinometer probe. The reading for the 9.5 m depth of the inclinometer casing were recorded for the comparison between FO and conventional inclinometer probes. A comparison between FO and conventional systems showed almost similar results to the conventional method. The FO inclinometer developed in this project shall provide vital information to assist designers and operators, as well as inform stakeholders on the integrity of their structures.

Convolutional modulation spectra of soliton molecular complexes in ultrafast laser

Optical soliton molecules are common pulse states in dissipative system, and they can combine with each other to form soliton molecular complexes which exhibit cumbersome spectral characteristics. As there is an intrinsic connection between the spectra of the soliton molecules and soliton molecular complexes, we demonstrate that the spectra of soliton molecular complexes are the results of quadratic modulation between component solitons, through experimental verification and simulation analysis. Specifically, two strongly bound solitons modulate to form soliton molecules, and then the soliton molecules modulate with weakly bound soliton pairs to form soliton molecular complexes, which is called convolutional modulation. The results obtained have vital significance to better understanding of the intrinsic nature and interaction of the solitons. The formation of quadratic modulated spectra plays an inspiring role in the fields like modern fiber-optic communication systems, optical frequency combs and its related precision measurements and various practical applications.

Water hammer detection based on FIV online analysis using a distributed fiber optic sensor.

In long-distance oil pipelines, the abnormal flow state of the fluid in the pipeline can cause continuous water hammer effects, which can damage the pipeline and even cause leakage or collapse. Based on this phenomenon, this paper proposes a new, to the best of our knowledge, detection method based on sensing optical fiber and phase-sensitive optical time-domain reflectometry (φ-OTDR) system to solve the problem of continuous water hammer detection in long-distance pipelines. The method uses a non-invasive, low-cost, real-time approach to monitor pipeline wall deformation characteristics and assess flow-induced vibration (FIV) intensity by statistically distinguishing water hammer signals from normal vibration signals and calculating the peak-to-average ratio (PAR) of these signals. Experimental results show that the FIV status of different types of pipelines can be effectively monitored by calculating the PAR of water hammer signals and vibration signals. The measured PAR based on the φ-OTDR system has high consistency with the PAR variation trend of simulation results, the distributed fiber optic sensor is less affected by environmental factors, and its detection distance and anti-interference ability are better than those of high-precision commercial triaxial acceleration sensors.

Gain Maximization of BDFA between the Wavelength of 1700nm to 1800nm

Fiber optic communication technology is becoming increasingly important in various fields, and high-speed, large-capacity fiber optic transmission systems are urgently needed. The design of fiber amplifiers is influenced by both fiber length and doping concentration. Although the Erbium-doped fiber amplifier (EDFA) is one of the most widely used components in fiber optic communication systems, its working area cannot meet the growing demand for network traffic.This paper presents a new fiber amplifier operating in the spectral region of 1700-1800 nm, pumped by commercially available laser diodes, highlighting the potential benefits of developing optical amplifiers for new spectral regions.This paper constructs a model to optimize gain at the central wavelength by finding relevant parameters, fitting a binary function of gain as a function of doping concentration and fiber length using Matlab, and optimizing the maximum gain using a simulated annealing algorithm. The proposed fiber amplifier has potential applications in telecommunications, sensing, and spectroscopy. The design of the amplifier has been optimized to achieve high gain and low noise figures, which are crucial for practical applications. Furthermore, the amplifier can be easily integrated into existing fiber optic networks, making it a promising candidate for future optical communication systems.

Maximum gain optimization of thulium-doped fiber amplifier based on genetic algorithm for peak gain spectrum at 1800- 2000nm

The optical fiber amplifier doped with rare earth elements has the characteristics of high gain, high doping concentration and short length. Compared with other fiber optic systems, the fiber used is shorter, also known as lumped fiber amplifier. At present, Er, Pr, Tm, Nd and Yb doped fiber amplifiers and lasers are mainly studied more. To further extend the transmission distance, improve the transmission quality and increase the transmission capacity, it is very important for the research of fiber amplifier. In this research, using a two-level structure, we investigate the maximum of the peak gain of the gain spectrum of a thulium-doped broadband fiber amplifier in the 1800-2000 nm wavelength range. Signal gain is inversely proportional to fiber length, doping concentration, and pump power in both the absorption spectrum and the emission spectrum, as shown by the relationship diagram of signal gain with these variables. And through the genetic algorithm data optimization, we get that when the fiber length is 2.2 m, the maximum gain is 42.7 dB.

A High-Security Probabilistic Constellation Shaping Transmission Scheme Based on Recurrent Neural Networks

In this paper, a high-security probabilistic constellation shaping transmission scheme based on recurrent neural networks (RNNs) is proposed, in which the constellation point probabilistic distribution is generated based on recurrent neural network training. A 4D biplane fractional-order chaotic system is introduced to ensure the security performance of the system. The performance of the proposed scheme is verified in a 2 km seven-core optical transmission system. The RNN-trained probabilistic shaping scheme achieves a transmission gain of 1.23 dB compared to the standard 16QAM signal, 0.39 dB compared to the standard Maxwell-Boltzmann (M-B) distribution signal, and a higher net bit rate. The proposed encryption scheme has higher randomness and security than the conventional integer-order chaotic system, with a key space of 10,163. This scheme will have a promising future fiber optic transmission scheme because it combines the efficient transmission and security of fiber optic transmission systems.

Low-Cost Fiber-Optic Sensing System with Smartphone Interrogation for Pulse Wave Monitoring

Pulse wave measurement is a highly prominent technique used in biomedical diagnostics. The development of novel cost-effective pulse wave sensors will pave the way to more advanced healthcare technologies. This work reports on a pulse wave optical fiber sensor interrogated by a smartphone. The sensor performance was tested in terms of signal to noise ratio, repeatability of demodulated signal and suitability of demodulated signals for the extraction of information about direct and reflected waves. The analysis showed that the observed fluctuations of signal parameters are caused by variability of the state of the cardiovascular system and not by the system noise.

Resonant collisions among X-type, multi-lump, generalized breathers, N-solitons and rogue waves in plasma

This paper studies the (1+1)-dimensional Kuramoto–Sivashinsky equation (1D-KSE) also known as canonical evolution equation within the context of flame front propagation, plasma instabilities, and phase turbulence in reaction–diffusion systems. We use Hirota’s derivatives to formulate bilinear equations and subsequently compute various types of solitons. We obtain lump solution, lump one strip, lump two strip, X-type, lump periodic solution, generalized breather and rogue wave solutions for our governing model with the help of Hirota bilinear method (HBM) and the ansatz approach. Breathers solutions may be used to improve the efficiency of fiber optic communication systems and solitons in plasma waves. Rogue wave solutions may be used for the safety of oil platforms and ships while lump wave solutions can be utilized in manipulating and controlling laser beams for materials processing or laser surgery. We also discuss one, two and other soliton interactions for 1D-KSE under some constraint conditions. These interactions may be discussed in plasma stability and confinement, which can control fusion as a future energy source.

High-power, low noise, high gain few-mode fiber amplifier

The few-mode erbium-doped fiber amplifier (FM-EDFA) is a necessary component for high-capacity long-haul mode-division multiplexing (MDM) fiber optic communication systems. In this paper, an all-fiber few-mode amplifier based on erbium-ytterbium co-doped double-clad fiber is designed and demonstrated. We have developed a fiber-optic pump beam combiner and a few-mode isolator. Combined with the two-stage cascade method, an all-fiber few-mode fiber amplifier with high-power, high-gain and low-noise is realized. Simultaneous amplification of 6 modes (LP01, LP11a, LP11b LP21a, LP21b and LP02) are achieved in the 1535–1565 nm range with average modal gain greater than 40 dB, maximum saturated output power up to 29.5 dBm, differential modal gain (DMG) of ∼3 dB and minimum noise figure (NF) of 4.69 dB.