Time and spatial domains in ϕ-OTDR perturbation detection and recognition for pipeline and border security applications in very long fiber under test (FUT) environments have not been properly analyzed so far. We propose in this paper several issues and the corresponding solutions that should be considered in both domains when developing those applications. Solutions are based on: (1) the importance

Fiber to the home networks plays a substantial role in helping operators to satisfy the increasing bandwidth demands of their subscribers. The dissemination of these networks brings new challenges, mainly in terms of the reliability of the optical fibers, especially when deployed in aggressive environments. In this work, we study the aging behavior of optical fibers in the presence of sodium chloride

In this paper, aiming at the problem of vibration event classification based on phase sensitive optical time-domain reflectometer (Φ-OTDR), we propose an efficient multi class event recognition scheme based on Variational Mode Decomposition (VMD). The signals collected by optical fiber sensors are preprocessed by the VMD algorithm, and then the features of the signals are extracted by Mel Frequency

A fiber-optic humidity sensor based on microsphere resonators with graphene oxide (GO) coated is proposed. A variable pitch off-axis spiral structure (VPOASS) excites multiple higher-order cladding modes in single-mode fiber (SMF) and introduces a strong evanescent field. Hollow glass microspheres are deposited on the surface of the VPOASS, and the GO film coated on the surface of the microspheres

The vortex beam owns helical phase factor, orbital angular momentum, and hollow structure of intensity distribution. It is widely applied in information coding, optical manipulation and optical sensing. This paper attempts to design a fiber Bragg temperature sensor based on vortex light, including an orbital angular momentum (OAM) beam transmitted by fiber Bragg grating (FBG), an optical fiber path

The reflection spectrum characteristics of fiber Bragg grating are very important for its sensing applications. A method of “Feature Extraction-Support Vector Machine (FE-SVM)” to identify spectral types is developed and experimentally demonstrated. The reflection spectrum characteristics of fiber Bragg grating are analyzed and extracted based on theory and simulation calculation. The characteristic

Aiming at the requirement of high precision, high orbit and long-life in tasks of spacecraft, photonic crystal fiber (PCF) is used in the development of Interferometric Fiber Optic Gyroscope (IFOG). And in this paper, we introduced current work in development of this filed, of which the bias stability is 0.001°/h and operating range is ±20°/s. In addition, the technology included PCF used in our work

The fiber optic gyroscope (FOG) has been widely used in the field of dynamic angle measurement due to its characteristics of wide dynamic range and high precision. Considering the change of the installation state of the FOG and the inconvenience of the calibration of the scale factor in engineering, an error compensation of the angle measurement using FOG, which is based on the tilt sensor, is proposed

We numerically demonstrate the generation of a very high peak power femtosecond pulse train by splitting a 1 ps, 100 kW pulse of central wavelength 2 μm using a few meters length of a large mode area fiber. The input 1 ps pulse during the propagation splits into multiple femtosecond pulses of very high peak powers. Concurrently, the spectral domain of the pulse also witnesses multiple peak formation

FiWi network is a multi-domain network that integrates optical and wireless networks. Hybrid fiber-wireless (FiWi) access network endeavours at consolidating the huge amount of available bandwidth of optical networks and the ubiquity, mobility of wireless access networks with the motive of reducing cost and complexity. This manuscript entails investigations undertaken towards optimal placement of multiple

Fiber Bragg grating (FBG) is a promising technology for shape detection in medical surgery robots. Conventional optical fiber is prone to fracture due to bending and torsion, so it needs fiber encapsulation before use. However, the encapsulating materials and bonding materials bring strain transfer loss. For correcting error and improving measurement precision, the thin diameter no-substrate sensor

For optical networks, routing and resource allocation which considerably determines the resource efficiency and network capacity is one of the most important works. It has been widely studied and many excellent algorithms have been developed. However, theoretical analysis shows that routing and resource allocation belongs to the Nondeterministic Polynomial Complete (NP-C) problem no matter in wavelength

This work reports the implementation and experimental performance analysis of innovative 5G new radio (NR) photonically-amplified mobile backhauls and fronthauls. We claim to utilize fiber-optic links not only for data transmission and transport but also for amplifying ultrawideband radiofrequency (RF) signals from all mobile communication generations, including the current 5G and future 6G networks

This paper is devoted to the study of an acoustic sensor system based on linear fiber optic Sagnac interferometer. An improved threshold denoising algorithm combined with the wavelet theory is proposed. Furthermore, a hybrid scheme based on the improved algorithm with bandpass filter is explored, and experimental verification of theoretical investigation is accomplished as well. Taking the measured

Optical fiber based sensors capable of measuring temperature distribution over a given length are particularly attractive in the biomedical field, especially in the case of real-time monitoring of minimally invasive hyperthermal treatments of tumors, such as laser ablation, given their intrinsic multiplexing along a single fiber span and the unique properties of optical fibers in terms of flexibility

Concrete structures are easy to produce cracks which seriously affect the safety of the structures. Rayleigh based distributed optical fiber sensing technique has been used to measure the strain field evolution associated with crack initiation and growth in concrete structures. A reinforced concrete beam has been tested under four-point loading test with optical fibers both pasted on the surface and

We propose a novel method of THz 4-ary pulse amplitude modulation (PAM-4) signal generation by a modulator driven by binary scheme with different driving voltages without a digital-to-analog converter (DAC). We experimentally demonstrate the transmission over 1-m wireless link employing 4-GBaud PAM-4 signal at 400–450-GHz in the photonics aided wireless terahertz-wave system. A cost-effective solution

We present a new type of few-mode fiber which features an elliptical ring-core with two stress rods. This type of few-mode fiber can separate the adjacent modes from each other. By using the high refractive index difference of 0.03 between the core and cladding and the birefringence caused by stress rods and elliptical ring core, 10 modes can be obtained. And the minimal effective refractive index

This research demonstrates that fiber Bragg grating (FBG) strain sensors can survive and provide useful strain information when integrated into a woven fabric subjected to ballistic impact testing. In this work, FBGs were integrated into a single-layer, Kevlar® fabric, sensing mat, placed between a 30-layer Kevlar® fabric shoot pack and clay backing material, and then impacted with an 8.23 g, 12.69 mm

This work proposed and demonstrated stable passive mode-locking in a thulium-holmium doped fiber laser (THDFL) using molybdenum oxide (MoOx) deposited onto a tapered fiber as a saturable absorber (SA). The SA was fabricated using the optical deposition technique for 2.0 µm region operation. The modulation depth, saturation intensity and non-saturable loss of MoOx SA were measured to be ~24.3%, ~0.01 MW/cm2

An ultra-broadband surface plasmon resonance (SPR) sensor with high sensitivity adopting four-core photonic crystal fiber is designed. The impacts of fiber structure parameters on the sensing performance are theoretically studied in detail. The investigation results demonstrate that, the average wavelength sensitivity of our proposed sensor is up to 1.135 × 104 nm/refractive index unit (RIU) within

A refractive index (RI) sensor is demonstrated using dual paralleled Fabry-Perot (FP) cavities and applied to silica colloidal sol aging monitoring in situ. Due to the Vernier effect, a 22-fold enhancement of spectral envelope wavelength variation in response to RI change is achieved compared with single FP sensor. The high RI sensitivity (-20811 nm/RIU at RI from 1.3337 to 1.3409) and excellent static

The emerging cloud computing, IoT, bulk-data store-and-forward datacenter applications are dominating the Internet traffic, which contains the commercial and business data services and behaves periodically. The traffic peak remains high during a certain time each day (known as peak traffic hours). This results in heavy load on the network, leading to higher level of connections blocking. In order to

A novel design for dispersion compensation based on dual core liquid crystal photonic crystal fiber (DC-LCPCF) is reported and analyzed. The new structure is based on the optical coupling between the dual cores of the suggested PCF. The full vectorial finite element method (FVFEM) is used to study the dispersion characteristics of the DC-LCPCF. A very large negative chromatic dispersion of 27101.8 ps/(nm-km)

A novel kind of near-infrared communication window of photonic crystal fiber (PCF) polarization filter based on filled silver nanowire is proposed in this paper. The silver nanowire is selectively filled in a air hole of the cladding, and the performance of this PCF is analyzed by changing the diameter d2 of the near-core small air holes by finite element method (FEM). It is found that the confinement

Statistical distribution of single mode fiber (SMF) coupling efficiency ηc with atmospheric compensation is important to evaluate the bit error rate performance of the satellite to ground laser communication (SGLC). The statistical distribution of SMF coupling efficiency with adaptive optics (AO) compensation under different turbulence strength is investigated. When the AO is turned on, the signal

In short reach intensity modulated and direct detected (IM/DD) optical multiple-input multiple-output (MIMO) systems linear equalization strategies are commonly applied. However, the square-law detector inherently is a non-linear system element. This work investigates this discrepancy and shows for which laser types and under which mode coupling conditions baseband linearity applies for the first time

We report experimentally a multi-wavelength Thulium-doped fiber (TDF) laser based on all-fiber theta cavity and a dual biconical taper filter without isolator. The dual biconical taper with waist of 50 μm and length of 188.05 mm is implemented as a narrow band filter. Three stable laser output states are successfully obtained with one, two or three wavelengths by increasing the pump power and properly

The 5G wireless communication systems promise to utilize the RF spectrum more efficiently and use advanced modulation and access techniques to provide ultra-high data rate speeds. Millimeter wave (MMW) signals and MMW based systems are playing a fundamental role in achieving these requirements. The modules and devices, proposed for these systems, are intended to use the robust capabilities of photonic

Online monitoring the ice-coating status along the overhead transmission lines under extreme weather is important for the safe operation and pre-warning of power-communication system. For the loose-tube composite fiber-optic ground wire, the external strain applied on the cable caused by the coated ice are directly measured and the ice-coating status are estimated based on the spontaneous Brillouin

In this paper, a curvature sensor based on fiber ring laser with Sagnac loop is proposed and experimentally demonstrated. The Sagnac loop is inserted into a fiber ring laser used as the sensing element and the filter. The intracavity sensing is induced in the fiber laser with the filtering characteristic of the Sagnac loop modulated by the curvature. The intracavity sensing system is used to narrow

This paper studies the load-balanced routing and admission control for point-to-multipoint traffic flows in elastic optical networks (EONs). EONs have emerged as a promising technology to provide high capacity for next-generation networks. Elastic bandwidth allocation promotes the spectrum utilization efficiency. We consider the problem of constructing bandwidth-guaranteed trees for on-demand point-to-multipoint

In previous experiments, the authors demonstrated that strain values collected from fiber Bragg gratings (FBG) integrated into a single layer of Kevlar fabric, placed between a soft armor test specimen and backing material, could be related to the time dependent back-face deformation (BFD) of the armor sample. In this paper, we investigate the specific fabric deformation and failure mechanisms that

A simple, high-sensitivity strain sensor based on a sealed optical microfiber coupler (OMC) was proposed and demonstrated. Affected by the strain, the effective refractive index (RI), microfiber length, microfiber diameter changes the coupling coefficient of the OMC. Due to the uneven force of the port3 and port4, the strain sensitivity after encapsulation will improve, which is proved in the experiment

For the cladding removed multimode fiber, when the refractive index of the external solution is close to the fiber core, it will cause refractive-index-matched coupling effect. In this work, the appearance of two index-matched points was observed. One of the index-matched point located at short wavelength, which had not been reported previously. Then, magnetic fluid was used as the external solution

A low-cost real time load measurement system employing fiber Bragg grating as a strain sensor and long-period grating as an edge filter for structural health monitoring is being reported in the present work. The shift in Bragg wavelength due to applied load on a prototype bridge is converted to corresponding change in optical power using edge filter technique. Further, this change in the optical power

In this paper, a novel hybrid hexagonal Photonic Crystal Fibre(PCF), which harnesses the golden ratio for its elliptical core design, is proposed. This work aspires to exploit circular air holes in the construction of PCF. It aids not only to achieve the desired properties but also to curtail the extravagant efforts needed for the fabrication. The Finite Element Method is used to analyze the properties

A new fiber temperature sensor is proposed based on dual-longitudinal mode laser self-mixing interference effect in a distributed Bragg reflector fiber laser. The temperature analytical model is established by use of the three-mirror cavity model and the interference superposition theory of the multi-longitudinal mode laser. It is indicated that this preferable model is sufficient to real-time track

We propose a novel scheme of 8-ary pulse amplitude modulation (PAM-8) signal generation by a dual-polarization Mach-Zehnder modulator (DP-MZM) driven by binary data with different driving voltages without digital-to-analog converter (DAC). The transmission over 1-km dispersion-shifted fiber (DSF) employing 39.72-GBaud PAM-8 signal is successfully demonstrated in the bandwidth-limited system, satisfying

Here we propose a simulation model based on a previously reported analytical description of the Brillouin gain, that takes into account pump depletion, which allows us to make very accurate calculations for Brillouin fiber lasers (BFLs) working both in a single and cascaded multi-wavelength configurations. Output powers and conversion efficiencies are analyzed and compared with experimental results

Routing, spectrum assignment are key issues and the hot focus area in multi-domain elastic optical networks (EONs). When the EONs with multi-cores, more challenges will be faced, such as core allocation, crosstalk, etc. To tackle these challenges, we establish a mixed integer linear programming model with the maximum index used frequency slots (MIUFS) to be minimized, which is used to determine the

All optical wavelength converter (AOWC) play important functionalities to enhance the network reconfiguration, efficient wavelength routing and assignment, non-blocking capacity in future dynamic optical access networks. In optical access networks, bandwidth limitation and wavelength continuity constraints lead to inefficient utilization of wavelength resources. AOWCs are the premier option to cope

The nonlinear characteristics of the electro-optic components are the major limiting factor to realize a multi-level signal transmission. Cascaded multi-modulus algorithm (CMMA) is a popular blind equalization scheme that can compensate for only linear distortions without using any training sequence. In this paper, a modified CMMA is proposed to blindly adapt the tap weights of a receiver-side nonlinear

Given the importance of multicast traffic in current optical networks, many effective multicast routing and spectrum assignment (MRSA) algorithms have been proposed to achieve efficient multicast transmission in elastic optical networks (EONs). However, most of these MRSA algorithms were focus on optimizing only the spectrum resources allocated to multicast service requests, but ignored some fragmented

In many distributed Brillouin fiber-optic sensing systems, Stokes and anti-Stokes scattering have to be separated. Conventionally, optical filtering is adopted for the separation and inevitably incurs loss of the scattering signal due to the close frequency spacing between Stokes and anti-Stokes scattering. In this paper, a new technique to separate Stokes and anti-Stokes scattering is proposed based

In an immunoassay test, which is a representative analytical method for evaluating the performance of a biosensor, the change of the sensor’s output with respect to the continuous change of the measurement target concentration is represented by a graph and defined as the characteristic curve of the sensor. In most studies using biosensors (disposable or not disposable), the characteristic curve of

A low-cost liquid level sensor capable of continuous liquid level sensing is proposed in this work. The sensor is based on twisted tapered plastic optical fibers (POFs) which is fabricated by twisting the tapered POFs around each other. The tapered structure could enhance the evanescent field and the light transmission from one POF to the other. The changes of liquid level can lead to the variations

Brillouin optical correlation-domain reflectometry (BOCDR) is one of the fiber-optic Brillouin-based distributed sensing techniques for strain and temperature with single-end accessibility. Since the first proposal of the basic concept in 2008, the performance of BOCDR has been drastically improved from a variety of aspects including high-speed operation. Here, we focus on one of the high-speed BOCDR

A compact optical fiber sensor by embedding fiber Bragg gratings (FBGs) in strongly coupled multicore fiber (SCMCF) is proposed for multipoint and multiparameter sensing. To build the device, two FBGs with different peak wavelengths were inscribed in a segment of SCMCF. Then one end of the SCMCF was fusion spliced to a single-mode fiber (SMF) and the other end of the SCMCF was cleaved. In the SMF-SCMCF

5G mobile fronthaul (MFH) network requires data transmission with large bandwidth and ultra-low latency. Orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) passive optical network (PON) system is the 5G MFH solution with low spectrum efficiency and large bandwidth. The OFDM/OQAM-PON transmission performance will be undermined by intrinsic imaginary interference

We experimentally demonstrate strain-induced speckle variation. When we take the whole speckle into consideration, the correlation function under different strain decreases dramatically at the beginning, and then it saturates as strain increasing. This tendency has nothing to do with the input wavelength and the length of multimode fiber (MMF), thus the operating cost will be largely reduced if multimode

Aiming at the problem that traditional peak-seeking algorithms cannot directly detect multiple reflections of Fiber Bragg Grating (FBG) sensing systems, this paper proposes a multi-peak detection algorithm. A seven-point moving average filter is used to process the FBG reflection spectral signal, reduce the high-frequency noise in the spectral signal, and determine the optimal segmentation spectral

Generally, broadband absorbers has much non-saturable loss and low laser damage threshold, which limits the average output power of the fiber lasers mode locked by broadband absorbers. Exceptions are the absorbers in evanescent wave mode locking, in which way only weak laser passes through the absorber section. However, evanescent wave mode locking method needs to change the original structure of the

In this review paper, we systematically summarize the various tapered optical fiber geometries and their sensing applications based on MZI. In addition, these geometries exploit strong evanescent field by giving appraise of the current issues with their sensing applications. The main advantage of these geometries is to minimize the size of optical devices, also it offers the possibility of enhanced

The nonlinear mapping characteristic of artificial neural network (ANN) is suitable for temperature extraction from Brillouin scattering spectra in optical fiber sensing system. To further improve the generalization ability of neural network, an optimized method for ANN training is proposed in this paper. Firstly, a set of noisy training data with different linewidth under various temperatures and

A type of total internal reflection photonic crystal fiber (TIR-PCF) with high birefringence and multiple zero dispersion wavelengths is presented. The optical characteristics are numerically investigated by using the full-vector finite element method. Results show that, by setting the geometrical parameters, the mode birefringence can reach to 2.28 × 10−2 at the wavelength of 1.55 μm, and two zero-dispersion

The measurement of pressure by using distributed optical fiber sensors has represented a challenge for many years. While single-point optical fiber pressure sensors have reached a solid level of technology maturity, showing to be very good candidates in replacing conventional electrical sensors due to their numerous advantages, distributed sensors are still a matter of an intense research activity

Transmission–Reflection Analysis (TRA) is an inexpensive technique used in distributed monitoring systems for single perturbation tracking. However, TRA is limited to long distance applications (~km), since it has poor spatial resolution (~m) when combined to standard silica fibers. This paper proposes the use of a magnesium and erbium co-doped optical fiber in conjunction with the TRA technique. The

In this paper, characteristics of tunable slow light of different modes based on intramodal stimulated Brillouin scattering in a few-mode fiber are calculated by the full-vector finite element method. In addition, the influences of doping concentration (GeO2 doped) on the effective refractive index, effective mode area, Brillouin frequency shift, Brillouin threshold, time delay and pulse broadening

Optical fiber based sensor systems often utilize thin dielectric films coated on non-planar surfaces are needed to be inspected for quality assurance. However, non-destructive optical characterization of these films is not a simple method especially on curved large surfaces. In this study, we propose a real time procedure to estimate the optical properties of sub-wavelength transparent dielectric films