We report the theoretical analysis of the coupling optics involving laser diode to single-mode circular core graded index fiber excitation via upside down tapered parabolic microlens on the fiber in presence of possible transverse and angular misalignments. We use the relevant ABCD matrix appropriate for such type of coupling device in order to prescribe analytical expressions of coupling efficiencies

Two ultra-broadband polarization filters based on Structure 1 and Structure 2 are reported and characterized in terms of attenuation, crosstalk, bandwidth, and polarization filtering properties by the finite element method. Structure 1 is formed by introducing partial elliptical air holes in the first layer of the square-lattice gold-filled photonic crystal fiber. Based on the design solution of Structure

A joint optical signal-to-noise ratio (OSNR) monitoring and modulation format identification (MFI) is proposed based on signal amplitude histograms (AHs) by using convolutional neural network (CNN). By the use of the proposed scheme, the OSNR monitoring accuracy can be achieved 97.6%, 100%, and 100% for 28GBaud QPSK, 8-QAM, and 16-QAM respectively within a wide OSNR range (10–26 dB). Similarly, the

In order to provide high accuracy in shape measurement with multicore optical fibres, characterization and calibration procedures are an important part of sensor preparation. Some procedures can be considered mandatory for adequate shape reconstruction, while others can help to enhance the measurement accuracy. Several of such procedures are discussed and experimentally applied for demonstrating the

We experimentally report a high-order-mode (HOM) suppression effect which may bring dips in transmission spectrum of a large-size (with core diameter > 10 µm) six-hole helical microstructured fiber (HMSF). Firstly, we performed rigorous theoretical analysis in helical frame to demonstrate that high loss peaks do not appear in fundamental mode. However, this phenomenon suppressed at special wavelengths

We report the generation of h-shaped pulses and rains in a fiber laser with a Fabry–Perót (F–P) subcavity. An h-shaped pulse state composed of a sharp spike as a leading edge and a long flat-top bunch as a tailing one could be switched to an h-shaped pulse rain state by adjusting the polarization controllers (PCs). F–P filtering was found to play a crucial role in the formation of the h-shaped pulses

A side-polished single mode optical fiber based on conventional long-range surface plasmon resonance (cLRSPR) sensor and symmetrical long-range surface plasmon resonance (sLRSPR) sensor was proposed and experimentally demonstrated. The proposed structure of cLRSPR is composed of optical fiber/dielectric buffer layer (DBL)/Ag film while for sLRSPR is consisted of optical fiber/DBL/Ag film/DBL. Magnesium

To accomplish single-longitudinal-mode (SLM) output and continuous wavelength selection, an erbium-doped fiber (EDF) quad-ring (QR) laser is presented and experimentally examined. The designed QR scheme can induce a mode-filter effect to compress dense multi-mode oscillation, narrow laser linewidth and flatten power output simultaneously. Hence, the attained optical signal to noise ratio (OSNR) and

This study, based on the Next Generation Ethernet Passive Optical Network (NG-EPON) facing more complex and changeable network, develops a flexible and efficient resource allocation algorithm. First, a differentiated polling interleaved scheduling (DPIS) framework is designed based on dynamic awareness, significantly reducing idle time slots, improving channel upstream utilization, and performing

A two-dimensional cantilever vibration sensor based on Fiber Bragg Grating (FBG) is proposed. The proposed sensor consists of a section of optical fiber with double FBGs and three different beams. After theoretical analysis and experimental verification, the proposed sensor has a high sensitivity response. The experimental result shows that the natural frequency of the sensor in the x/y direction of

In this paper, we experimentally proposed and demonstrated the application of thin-film saturable absorber (SA) based on 8-Hydroxyquinolino cadmium chloride hydrate (8-HQCdCl2H2O) material as both Q-switcher and mode-locker in the cavity of erbium-doped fiber laser (EDFL). The 8-HQCdCl2H2O was embedded in polyvinyl alcohol (PVA) to fabricate the thin-film, which has then employed in the Q-switched

A large area of thick unconsolidated stratum layer overlying the coal seam of eastern China, which brought the regional disaster prevention issue under the circumstance of unconsolidated layer settlement triggered by mining activities. In this paper, the multi-point monitoring system based on fiber Bragg grating (FBG) sensors array was implemented into the deep unconsolidated layer to realize a long-term

Spent coffee ground (SCG) was demonstrated as saturable absorber (SA) for Wideband Q-switched fiber lasers generation. The SCG SA has a broad linear absorption that covers from 1000 nm to 2000 nm wavelength and a modulation depth of 30% at 1.55-µm region. Through purification process, the finer SCG powder is obtained, and be embedded with a polyvinyl alcohol for thin film formation. To realize Q-switching

A Weigh in Motion (WIM) system is proposed, employing two fiber Bragg grating (FBG) sensors to evaluate the strain at a point on a prototype bridge due to a moving vehicle. The FBG's are fixed at two different longitudinal girders of bridge along the line of motion at different orientations. The parameters of investigation include strain developed in the proximity of FBG’s and speed of the vehicle

In this article, lasing characteristics of a newly designed ytterbium-doped modified hybrid multi trench fiber (YDMHMTF) has been numerically investigated for strongly pumped conditions. The designed YDMHMTF is maintained single-mode condition with an effective mode area of 1300μm2 at the wavelength of 1064 nm for the compact bending radius of 7.5 cm. The radius of doped region is varied up to a maximum

In recent years, distributed fiber optic sensing (DFOS) has been widely used for structural deformation monitoring. Conventional deformation monitoring methods using DFOS have a limitation in that they are based on the conventional assumptions in continuum mechanics such as uniformity and continuity. These methods are unsuitable for cracked concrete structures that exhibit discontinuity (discrete body)

Advancements in fabrication of miniaturized optical scanners would benefit from micrometer sized optical fiber tips. The change in the cross section of an optical fiber tip is often accompanied with the presence of a longer tapered area. The reduction of the cross section of double clad optical fibers (DCFs) with a flat interface surface at the region where a change in the cross section takes place

The unsteady-state thermal conduction process in several photonic crystal fibers (PCFs) was studied theoretically by the explicit finite-difference method using the thermochemical SiOx production model. The threshold power Pth for fiber fuse propagation in these PCFs was one order of magnitude higher than that for conventional single-mode optical fibers (SMFs). These results agreed with the experimental

In this paper, a temperature sensor based on a second-order PbS fiber Solc-Sagnac interferometer is presented. The PbS fiber and the two sections of single-mode fiber (SMF) are spliced together, it is named SMF-PbS-SMF structure. The light passes through the coupler and is divided into two beams of equal power, which are propagated in the Sagnac loop and travel through the two PbS fibers. The interference

One of the common techniques to increase data bitrate using visible light communication (VLC) fibers system is to use wavelength division multiplexing (WDM). However, the implementation of WDM requires additional devices and more power consumption which can limit the system performances. To overcome these problems, we propose a new approach for designing an RGB multiplexer based on multicore polymer

In this paper, a new circular photonic crystal fiber (PCF) is designed, which can support stable transmission of 30 orbital angular momentum (OAM) modes. It is composed of 4 rings of air holes in the cladding and a large air hole in the center. The numerical results show that the fiber has good features. In the wavelength range of 1.35–1.8 μm, dispersion variations are less than 27.99 ps/nm/km when

The degradation of quality-of-transmission (QoT) due to the dispersion effect is a critical issue in elastic optical networks (EONs). To satisfy the required quality of transmission, a robust modulation level needs to be adopted. Thus, the number of required slots for spectrum allocation is increased. Although dispersion compensation devices reduce the effect of dispersion, they require an additional

Due to the expansion of telecommunication services, the demand for technologies that improve transmission quality has been growing in recent years. One of these technologies is optical transport networks (OTNs), which works as a layer above the DWDM (Dense Wavelength Division Multiplexing) network to enable the most efficient use of resources. This work proposes an OTN network planning solution over

Numerical solving of nonlinear Schrödinger equation is performed for a self-similar femtosecond fiber laser cavity in order to investigate the effect of its key parameters (e.g., output coupling rate, net dispersion of cavity, and modulation depth) on the energy and the spectral bandwidth of output pulse in the stable mode-locking state. The calculations indicate that by decreasing the output coupling

In this paper, we propose an in-band optical signal-to-noise ratio (OSNR) monitoring method based on support vector machine (SVM). This method is tailored for the analysis of polarization-division multiplexing (PDM) m-ary quadrature amplitude modulation (m-QAM) signals. OSNR-related features are extracted from the numerical characteristics of Stokes parameters, while modulation-order related features

Nowadays, free space optics (FSO) is becoming popular and is very competitive to the fiber optic technology for providing broadband services at very high data rates without the requirement of any spectrum licensing. FSO links can be installed within a few hours and at a very low cost. As compared to the optical fiber, FSO links do not have any problem of faults during digging and maintenance of roads

The resonant wavelength is an important parameter of fiber Bragg grating (FBG). When FBGs are fabricated by femtosecond (fs) laser direct writing, it can be fine-tuned through the process of stress annealing. By changing applied stress, it can be permanently fine-tuned in the range of 20.76 nm relative to the original one, and the tunable sensitivity is 1.48 nm/MPa. Besides, the elastic limit strength

There is an increasing interest among the researcher community, and industries on the design, and development of a combined distributed acoustic sensing, and a pattern recognition system to detect, and classify potentially dangerous intrusion events. In this work, we describe the design, and optimization of a distributed intrusion sensing system using Rayleigh-phase sensitive optical time domain reflectometry

A strain gauge sensor based on Fiber Bragg Grating (FBG) for diameter measurement is proposed and experimentally demonstrated. The sensor is easily fabricated inserting the FBG on the strain gauge—it was fabricated using a 3D printer—and fixing the FBG in two points of this structure. The idea is to vary the diameter of the structure. We developed two experimental setups, the first one is used to evaluate

When using distributed optical fibers for structural health monitoring, in order to ensure the survival rate of the optical fibers, it is usually necessary to insert the optical fibers into the structure for protection. The coupling performance between the optical fibers and the structure determines the accuracy of the monitoring results. In order to explore the strain transfer law of optical fibers

The Vernier effect is an effective way of magnifying the sensitivity of the sensor for higher resolution sensing. The Fiber-optic cascaded Fabry-Perot Interferometric (CFPI) temperature sensor has been theoretically studied and experimentally investigated in this paper base on Vernier effect. It has been manufactured by a segment of pure silica hollow-core fiber (HCF) fused between two sections single-mode

The response of a quasi-distributed fiber optic sensing system to a short interrogation pulse can be considered as a sparse signal in the time domain. This attribute can be exploited to enhance its performance beyond the commonly accepted limits. The work described here is analogous to some compressed sensing systems, which can be adequately sampled at sub-Nyquist rates, based on knowledge of their

Humidity is an important parameter in many industry fields and accurate humidity measurement is of great significance to improve production efficiency and ensure product quality. This paper presents a sensing model and scheme for utilizing thermoplastic polyimide (PI) coated fiber Bragg grating (FBG). The humidity sensitive PI layer was firstly prepared and coated on the FBG. The humidity calibration

The growing traffic demand in data center interconnections (DCIs) requires high-speed and low-cost transceivers that can flexibly adapt to different transmission distances up to 80 km or further. In this paper, based on the double-side electro-absorption modulated laser (DS-EML), we propose a transmitter with a fixed 90-degree phase rotation on one side of the DS-EML that can realize quasi-linear complex

We demonstrated passively Q-switched 1-, 1.5-, and 2-μm fiber lasers by exploiting ferroferric-oxide nanoparticles (FONPs) as a broadband saturable absorber (SA). FONPs were prepared by a method of thermal decomposition, and then were mixed with sodium carboxymethylcelluose (NaCMC) to form a FONPs film. The FONPs film was sandwiched between two fiber ferrules to fabricate the FONPs SA, which had a

A Mach-Zehnder interferometer (MZI) based on tapered photonic crystal fiber (PCF) for simultaneous temperature and relative humidity (RH) is proposed. It consists of two sections of single-mode fiber (SMF) fused with a section of tapered PCF. The temperature and RH sensitivities are improved by adding a taper in the middle of the PCF. The experimental results show that the temperature sensitivities

Elastic optical networks (EONs) have realized high-speed data transmission with attractively efficiency and flexibility in resource utilization. In order to guarantee the reliability and increase the efficiency of the multicast transmission in EONs, we propose a multiple leaf-ringing based protection algorithm with spectrum defragmentation (MLRP-SD) in this article. The proposed algorithm firstly sorts

Optical fiber tendencies are pushing for changes towards upgrading scalability, agility, and unwavering quality for multi-hungry bandwidth applications. In the quest for future proof of those multi-hungry bandwidth applications, is vital to take advantage of new multiplexing technologies as the surge of network traffic that soon will overwhelm the capacity of multimode fiber (MMF). Due to the issue

In this paper, we have reported a radio-over-fiber (ROF) system with 18-tuple frequency optical millimeter-wave using external modulator and four-wave mixing (FWM) in semiconductor optical amplifier (SOA). Signal lightwave and pump with frequency interval of 6fRF are generated by adjusting the parameters of the Mach-Zehnder modulator (MZM). After FWM in SOA and filtering, 18-tuple frequency millimeter-wave

Special equipment is prone to crack damage due to long-term pressure bearing during service. If the cracks in the structure are not detected in time and maintenance work is conducted, severe safety risks will be incurred. To overcome these problems, it is necessary to conduct full-time and full-domain structural on-line monitoring for special equipment to effectively prevent cracking of the special

In this study, to measure the frequency drift characteristics of the narrow-linewidth laser, we provide a method with high accuracy and adjustable measuring range that can be applied in a resonant optical gyro (ROG) system. In an ROG system, the laser frequency drift characteristics, such as fluctuation range and frequency, influence the performance of the closed-loop frequency-locked module. To measure

In this paper, an 85 GHz MM-wave signal is demonstrated in the fiber and MM-wave converged system in W-band. It is known to us, this is the first experimental demonstration that the pre-equalizaiton (PE) and probabilistic shaping (PS) techniques are applied to the fiber and MM-wave converged system. BER of 4.4 × 10−3 is achieved by using those method after 4-m wireless transmission and 25-km Standard

In recent years, the technology to narrow the gap between the achievable information rate and the Shannon capacity limits attracts increasing attention. In this paper, a probabilistic shaping coding method based on multi-repeat mapping is proposed. By applying block coding to the information sequences with our method, we transform the modulated constellation points from a uniform distribution to the

We present an optical fiber gas pressure sensor based on two cascaded Fabry-Perot interferometer cavities, one is a section of capillary tube spliced with single mode fiber at its two ends and the other consists of a pair of in-fiber reflection mirrors inscribed by use of femtosecond laser micromachining. The cavity length difference of the two Fabry-Perot interferometers can be precisely controlled

A weakly-coupled taper-based seven core fiber (TSCF) structure sensor for refractive index (RI) and temperature measurement with a fiber ring cavity laser in 2 μm band was proposed and demonstrated. The TSCF fiber structure acts as both the sensing head and the filter of the laser. Compared with the conventional broadband sensing system, the laser sensing system we proposed has a higher optical signal

On the basis of coherent optical orthogonal frequency-division-multiplexing (CO-OFDM), CO-OFDM/ offset quadrature amplitude modulation (CO-OFDM/OQAM) improves the spectrum efficiency by utilizing specially designed filter banks to eliminate the cyclic prefix (CP) inserted between consecutive OFDM blocks and decreases the demanding of guard band between two channels, being a promising candidate for

The optical fiber acoustic emission (AE) sensing system with high sensitivity is stabilized for long-term detection in this paper. The high linear slope window of the phase-shifted fiber Bragg grating (PS-FBG) spectrum is tracked by the tunable laser source (TLS) to maintain high AE detection sensitivity. The experimental results show that the proposed method successfully solves the problem of PS-FBG

The high-precision strain calibration of a fiber Bragg grating (FBG) is critical to the engineering application of fiber grating sensors. In this paper, a strain calibration method based on the optical lever is proposed for the FBG sensor. The optical lever is used to measure a tiny displacement through optical amplification. Comparing with traditional strain calibration using a beam structure and

Elastic optical networks have recently emerged as one of the most promising technologies for creating next-generation optical core networks thanks to the adaptive spectrum allocation mechanism. In order to achieve higher spectrum efficiency and exploit elastic optical networking technology, in this paper, we introduce a novel perspective on re-designing dedicated path protection for elastic optical

The demodulation system is a very critical component of the seismic exploration, which determines the response speed and accuracy of data acquisition of the detection system. Here, we demonstrate a simulation and hardware implementation of demodulation system based on linear edge filtering method for fiber optic seismic sensor. The system is implemented mainly by an edge filter (long period fiber grating)

In this paper, a tree growth optimization (TGO) algorithm is introduced to diminish the computational complexity of the partial transmit sequence in exploring the optimal phase factors. The proposed TGO algorithm is an efficient method for reducing the high peak-to-average power ratio of optical orthogonal frequency division multiplexing signals. The problem of the peak-to-average power ratio causes

All-fiber humidity sensor based on Michelson interferometer with hyaluronic acid (HA) and polyvinyl alcohol (PVA) composite film is investigated. The interferometer is fabricated by fusing 691 μm thin-core fiber (TCF) with single mode fiber (SMF) together and melting the other end of the TCF into a circular shape. The outer of the interferometer is coated with HA and PVA composite film. As far as we

In this paper, applying the Deep Multilayer Perceptron Neural Network (MLPNN) to the Sum-Product Algorithm (SPA) for decoding the Modified Welch-Costas (MWC) coded Optical Code Division Multiple Access (OCDMA) system with Low-Density Parity-Check (LDPC) code is analyzed. The goal is to train the MLPNN-SPA through the stochastic gradient descent (SGD) to learn and optimize the weights to each edge of

Optical label switching (OLS) is regarded as one promising solution for the packet-based optical switching. In this paper, a novel modulation, i.e., Manchester code + NRZ modulation is proposed for OLS. The Manchester coded payload signal the NRZ label signal are combined and then modulated onto an optical carrier by only one ASK modulator. The Manchester coded payload signal and the NRZ label signal

Fiber Bragg Gratings (FBGs) are extensively used as strain and temperature sensors in various industrial applications. The key task for FBG based sensing system is to convert the optical sensing data into user friendly information that can be interpreted with ease. Edge filter detection (EFD) interrogation technique is commonly used to convert wavelength encoded sensing data into optical power variation

We have demonstrated a high-sensitivity Fabry-Perot curvature sensor. The main components of its sensing fiber are hollow silica tube and single-mode fiber (SMF). When the sensor is bent, the length of the FPI changes with curvature. Hereby, we can achieve vector curvature measurement through cavity length demodulation. The convex and concave bending sensitivities are 151.30 nm/m−1 and −333.89 nm/m−1

Fiber Bragg gratings (FBGs), with smaller size, are suitable to measure the tooth root strain of ring gear which is an ideal signal for fault diagnosis of planetary gearboxes. In order to identify the fault features in the strain signal, a high-speed and high-resolution FBG interrogator is needed. Compared with wavelength-scanning interrogation approach, the edge-filter approach can achieve such a

Sinkhole is a unique geological disaster, which has the characteristics of concealment in space, accumulation in the development process and sudden collapse caused by roof instability, and the whole development process contains deformation and vibration information. This paper presents a distributed optical fiber strain-vibration joint system based on distributed optical fiber strain and vibration