Standard Single-mode Optical Fiber Research Articles

Total net-rate of 27.88 Tb/s full C-band transmission over 4,550 km using 150 km span length and high-gain EDFA amplification

We experimentally demonstrate a total net-rate of 27.88 Tb/s for C-band wavelength-division multiplexing (WDM) transmission over an ultralong span-length of 150 km. It is the largest net capacity × span-length product of 4182 Tb/s·km for C-band, single-core, standard single-mode optical fiber transmission over a length of more than 3,000 km. A total of 99 channels, spaced at 50 GHz intervals, are employed for transmitting 32 GBaud probabilistically constellation-shaped (PCS) 64QAM signals with an information entropy of 5.5. High gain amplifiers can achieve wavelength-division multiplexing (WDM) transmission with a bandwidth of 6.25 THz, at a noise figure below 4.3 dB, without the assistance of distributed Raman amplification.

Optical space division multiplexed heavy metals reflective sensors array coated with polyaniline/graphite nanofibers nanocomposite

Globally, water contamination with different types of heavy metals is a vital issue as it becomes poisonous and is considered a serious threat to human health. Three reflective standard single mode optical fiber (SSMF) sensors are developed for lead ions (Pb(II)) detection as a pollutant in water. The three SSMFs are etched with 40 µm diameter after that tapered with 13, 20, and 30 µm final diameter to produce an etched-tapered SSMF (ETSSMF). A nanocomposite of polyaniline/graphite nanofibers (PANI/GNF) nanocomposites is deposited on the three sensors to enhance their sensitivity towards the lead ions. Nanocomposite is investigated using SEM and a microscope. The three sensors are space division multiplexed using a 100 m length 4-core SMF for remote monitoring and measurements for remote monitoring for a wide geographical area coverage. The ETSSMF sensors exhibit response times of 84, 107, and 121 s and recovery times of 74, 81, and 87 s, respectively. The sensor with a smaller diameter shows a stronger response and higher sensitivity than the others. The sensors are linear and selective towards lead ions. The developed system can support the ability of real-time monitoring via the Internet from any place.

Fiber-optic temperature sensor based on glass Fabry–Perot interferometer

The paper presents a theoretical and experimental study of a fiber-optic all-glass microthermometer based on a Fabry–Perot interferometer. The interferometer is fabricated by applying borosilicate glass to the cleaved end of a standard telecom single-mode optical fiber using a microforge. According to the results of experimental studies, the spectral sensitivity of the fabricated interferometer was about 40 pm/°C. A mathematical model of the Fabry–Perot interferometer based on the method of scattering and transfer matrices is presented and verified, which makes it possible to calculate the spectral response of an interferometer with arbitrary structure parameters.

Layered Gallium Monosulfide as Phase‐Change Material for Reconfigurable Nanophotonic Components On‐Chip

AbstractThe demand for information processing at ultrahigh speed with large data transmission capacity is continuously rising. Necessary building blocks for on‐chip photonic integrated circuits (PICs) are reconfigurable integrated low‐loss high‐speed modulators and switches. Phase change materials (PCMs) provide unique opportunities for integration into PICs. Here, the investigation of layered gallium monosulfide (GaS) as a novel low‐loss PCM from infrared to optical frequencies is pioneered, with high index contrast (Δn ≈0.5) at the optical telecommunication band. The GaS bandgap switches from 1.5 ± 0.2 eV for the amorphous state to 2.1 ± 0.1 eV for the crystalline state. It is demonstrated that the reversible GaS amorphous‐to‐crystalline phase transition can be operated thermally and by picosecond green (532 nm) laser irradiation. The design of a reconfigurable integrated optical modulator on‐chip based on Mach‐Zehnder Interferometers (MZI) with the GaS PCM cell deposited on one of the arms for application is presented at the telecommunication wavelength of λ = 1310 nm, where the standard single mode optical fiber exhibits zero chromatic dispersion, and at λ = 1550 nm, where a minimum optical loss of 0.22 dB km−1 is obtained. This opens the route to applications such as reconfigurable modulators, beam steering using phase modulation, and photonic neural networks.

Study of the Feasibility of Decoupling Temperature and Strain from a ϕ-PA-OFDR over an SMF Using Neural Networks.

Despite several existing techniques for distributed sensing (temperature and strain) using standard Single-Mode optical Fiber (SMF), compensating or decoupling both effects is mandatory for many applications. Currently, most decoupling techniques require special optical fibers and are difficult to implement with high-spatial-resolution distributed techniques, such as OFDR. Therefore, this work's objective is to study the feasibility of decoupling temperature and strain out of the readouts of a phase and polarization analyzer OFDR (ϕ-PA-OFDR) taken over an SMF. For this purpose, the readouts will be subjected to a study using several machine learning algorithms, among them Deep Neural Networks. The motivation that underlies this target is the current blockage in the widespread use of Fiber Optic Sensors in situations where both strain and temperature change, due to the coupled dependence of currently developed sensing methods. Instead of using other types of sensors or even other interrogation methods, the objective of this work is to analyze the available information in order to develop a sensing method capable of providing information about strain and temperature simultaneously.

Distributed optical strain sensing measurements down to cryogenic temperatures.

Rayleigh backscattering (RBS)-based distributed fiber sensors technology is becoming more and more crucial in various fields such as aerospace and defense, automotive, civil, and geotechnical. This technology is measuring the naturally occurring Rayleigh backscatter level in the optical fiber core; thus, any standard single-mode telecom optical fiber can be used. The application of distributed optical fiber strain sensing in the harsh environments of the European Organization for Nuclear Research required several mechanical tests to study the accuracy of strain sensing in cryogenic conditions. This study compares the performance of a RBS-based distributed optical fiber strain sensing down to cryogenic temperatures (4.2K) with previously validated instrumentations such as electrical strain gauges and fiber Bragg grating technologies.

Switchable Dual-Wavelength Tm-Doped All-Fiber Laser Integrating a Fiber Tip Modal Interferometer

A switchable dual-wavelength thulium-doped all-fiber laser incorporating a fiber tip modal interferometer (FTMI) is reported. The FTMI relies on the splice joint between a standard single-mode optical fiber and a tapered microfiber with 60- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> uniform waist diameter, providing a spectral reflection response that allows the laser to emit beyond 2000 nm, specifically at 2009.20 nm and 2013.65 nm, under a dual-wavelength operation regime. Besides, switching between both laser lines is also observed and controlled by adjustments of the intracavity polarization state, obtaining the ability to operate in a single-wavelength regime at either 2009 nm or 2013 nm. Laser emission lines exhibit linewidths of around 50 pm, side-mode suppression ratios higher than 50 dB and maximum output power of 13.4 mW.

Realization of optical fiber regenerated gratings by rapid cooling and split annealing.

Rapid cooling,or quenching,during regeneration of seed gratings in standard single-mode silica optical fiber is explored. It is shown that regeneration can be broken up into stages in time. The novel, to the best of our knowledge, method of "split annealing" offers a unique tool for optimizing regeneration and studying fundamental glass science within a one-dimensional bi-material system. We demonstrate regeneration at temperatures as high as T = 1200°C for the first time as well as opening up an approach suited to batch processing of regenerated gratings.

Detailed spatial-spectral numerical characterization of axially symmetric broadband ultrasonic resonances in standard optical fibers

Standard single mode optical fibers (SMFs) have been widely employed to generate and measure ultrasonic signals in remarkable applications. In particular, optoacoustic fiber sensors provide unique features for microscale high resolution ultrasound imaging in biomedicine. However, at specific resonance frequencies, SMFs work as acoustic filters inducing relevant geometrical attenuation bands higher than 10 dB, which limit the sensors’ sensitivity and frequency operation, causing image distortions and artifacts. We have numerically demonstrated high frequency axially symmetric ultrasonic resonances inside an optical fiber for the first time. The propagation of resonant axially symmetric acoustic modes along 1 cm fiber is investigated by means of 2D and 3D finite element techniques up to 80 MHz. The dispersion of the modes and induced beatlengths are characterized from the complex multimode interference with the 2D Fourier transform. The simulated spectra are validated with the renowned Pochhammer-Chree analytical equations. The frequency response of the acoustically induced strains in the fiber core is evaluated, and important acoustic parameters relevant for the modulation of phase, wavelength and power in optical fibers and diffractive gratings are derived and discussed. The results show that these resonances are strongly dependent on the modal beatlengths. Solutions to improve the operation of fiber-based devices are proposed, pointing out new alternatives to advance broadband optoacoustic sensors and monolithic acousto-optic modulators.

Enhanced dispersion reduction using apodized uniform fiber Bragg grating for optical MTDM transmission systems

The aim of this work is to propose a model for enhancing chromatic dispersion compensation in standard single mode optical fibers (SSMFs). The proposed model consists of a single stage Apodized Uniform Fiber Bragg Gratings (AUFBG) in a post-compensation scheme. It is based on the Maximum Time Division Multiplexing (MTDM) technique. The performance of the proposed model is evaluated through the quality factor (Q-factor) and Bit Error Rate (BER) in four cases, in a comparative study. In case one, the system performance is evaluated without using UFBG. The other cases study the effect of the proposed model with using different connections schemes and the most common apodization functions. For simulation, the proposed model is connected in a 10 Gbps WDM 70 km link under ordinary operating parameters. The simulation and evaluation process is conducted by Optisystem 7.0. In the pre-compensation scheme, the best results are obtained as a maximum Q-factor of 9.2 and a minimum BER of 3.25 × 10–20, using a tanh apodization function. The proposed model realizes an improvement over the related work by at least ~ 68%.

Development and investigation of the sensitive element of the amplitude fiber-optic temperature sensor based on superimposed chirped Bragg gratings

In this paper we study an original technique for creating an amplitude temperature sensor based on n-pairs of chirped fiber Bragg gratings (CFBGs). The scalable design of the sensor allows to increase the range of the measured signal. The use of the amplitude interrogation technique ensures high speed, elementary nature of the scheme and simple operating conditions. The application of superimposed CFBGs as a sensitive element of an amplitude temperature sensor is investigated. As a result of the work, a method for measuring temperature with a fiber-optic sensitive element based on n-pairs of CFBGs is tested. Two superimposed CFBGs are inscribed in a standard telecommunication single-mode optical fiber using a KrF excimer laser system and Talbot interferometer. One of the superimposed structures is used as a reference element of the sensor and the second – as a sensitive element and is placed in a brass tube, where it is fixed on one side with an adhesive joint. The sensor has an accuracy of 0.48 °C and a sensitivity of 0.20 µW/°C for temperature measurement in the range of 30–70 °C. The results obtained are of great importance in the development of fiber-optic temperature control systems. Implementation of the sensor based on n-pairs of CFBGs allows scaling the power of signal, increasing the ability to detect a slight change in ambient temperature. The created sensor works according to the amplitude polling technique, which is characterized by high accuracy and speed of measurement, minimized scheme, simplified use and easy processing of the detected signal. In addition, the implemented interrogation method corresponds to the trend of developing low-cost fiber-optic systems without losing their main advantages.

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.

Advantages of using few-mode and multimode fibers in Phase Sensitive OTDR measurement system due to the modulation instability deferment

We discuss the possible advantages of using few-mode and multimode fibers in coherent optical time-domain reflectometry sensing systems. We show that the application of few-mode and multimode fibers decreases nonlinear effects and impedes modulation instability. In comparison to standard single-mode optical fiber, few-mode and multimode fibers may help to increase signal power at the receiver. We also show that few-mode fibers may potentially increase sensing distance.

Experimental study of saturable and reverse saturable absorption of Zn nanoparticles photodeposited onto etched optical fibers

In this paper, the non-linear optical response of photodeposited zinc nanoparticles onto an etched optical fiber is reported. Through chemical etching, 20 mm of the cladding of a standard single-mode optical fiber was removed to expose its core and subsequently, photodeposit zinc nanoparticles on it at different times (1, 5 and 10 min) by using a continuous wave laser at 1550 nm. The non-linear optical response was obtained by the P-scan technique using a high-gain pulsed amplifier with a pulse duration of 10 ns at a wavelength of 1550 nm. The experimental results showed that it is possible to get the effects of reverse saturable absorption (RSA) at irradiances less than 380 MW/cm 2 and saturable absorption (SA) for higher values. Consequently, the analysis of the results obtained shows that the third-order non-linear susceptibility x3 of the RSA is 2.2130 × 10−06 (esu) for 10 min of photodeposition, which decreases for shorter photodeposition times; On the other hand, the third-order non-linear susceptibility x3 of the SA is −5.8955 × 10−07 (esu) for 10 min of photodeposition, which increases for shorter exposure times. Finally, the experimental results obtained show that it is possible to make a photonic device with desired non-linear absorption properties by the photodeposition of metallic nanoparticles onto etched fibers, which makes it ideal for applications in optical communications.

A proposal for linear and nonlinear discrete and distributed sensing of mechanical strain with graphene-decorated optical fibers

We propose a novel optical sensor for the linear and nonlinear measurement of discrete and distributed mechanical strain, capable of discriminating longitudinal (traction) from transverse (compression) forces. The sensor is based on a standard single-mode optical fiber whose cladding is removed and its core is coated with graphene. The transduction scheme works by monitoring changes experienced in the linear absorption and the nonlinear coefficient of the graphene-decorated fiber when subject to said forces. Further, we show that the distributed sensing of strain can be easily performed by means of conventional optical time-domain reflectometry. Last, we introduce a two-piece sensor design capable of discriminating the type of strain by straightforward loss measurements.

Low loss and broadband low back-reflection interconnection between a hollow-core and standard single-mode fiber.

We report simultaneous low coupling loss (below 0.2 dB at 1550 nm) and low back-reflection (below -60 dB in the 1200-1600 nm range) between a hollow core fiber and standard single mode optical fiber obtained through the combination of an angled interface and an anti-reflective coating. We perform experimental optimization of the interface angle to achieve the best combination of performance in terms of the coupling loss and back-reflection suppression. Furthermore, we examine parasitic cross-coupling to the higher-order modes and show that it does not degrade compared to the case of a flat interface, keeping it below -30 dB and below -20 dB for LP11 and LP02 modes, respectively.

Low-κ, narrow linewidth III-V-on-SOI distributed feedback lasers with backside sampled Bragg gratings.

We demonstrate a heterogeneously integrated III-V-on-SOI distributed feedback laser with a low grating strength (κ < 40 cm-1) and a narrow linewidth of Δν = 118 kHz. The laser operates single mode with a side-mode suppression ratio over 45 dB, provides a single-sided waveguide-coupled output power of 22 mW (13.4 dBm) and has a wall-plug efficiency of 17%. The dynamic characteristics were also evaluated, obtaining an intrinsic 3 dB modulation bandwidth of 14 GHz and a photon lifetime of 8 ps. Large-signal intensity modulation using a 231-1 PRBS pattern length revealed open eye diagrams up to 25 Gb/s and a penalty on the dynamic extinction ratio lower than 1 dB after transmission over a 2 km standard single mode optical fiber.

Influence of surface roughness on the sensitivity of a D-shaped optical fiber-based refractive index sensor

This paper presents the evaluation of the influence of surface roughness on the performance of a refractive index sensor based on a D-shaped optical fiber. In addition, the manufacturing process of D-shaped sections on standard silica single-mode optical fibers with different rms roughness values is described. The surface roughness morphology generated by the abrasive process is measured by processing microscopic images using the Gwyddion software. A model for the surface roughness, using the third order Weierstrass fractal function, is proposed and simulated with COMSOL Multiphysics. Experimental and simulation results are presented. The results show that the surface roughness increases the device insertion loss, as expected, but contributes positively to the sensitivity of the refractive index sensor, reaching sensitivity levels of 148.87 dB/RIU with a resolution of 10−4 RIU. The good agreement between the computational and experimental results is highlighted. Due to the good figures of merit obtained, the optical sensor has potential of application in biochemical sensing.

Demonstration of Coherent Interference between Acoustic Waves Using a Fiber Ring Resonator.

Optical fibers were previously demonstrated to propagate and detect acoustic modes that were converted from Lamb waves for structural health-monitoring applications; typically, a fiber Bragg grating sensor in the optical fiber is used to detect acoustic modes. Acoustic modes can transfer from one fiber to another through a simple adhesive bond coupler, preserving the waveform of the acoustic mode. This paper experimentally investigates the coherence of acoustic waves through the adhesive coupler, using a fiber ring resonator (FRR) configuration. This configuration was chosen because the wave coupled to the second fiber interferes with the original wave after it encircles the fiber ring. We performed this experiment using different geometries of optical fibers in the ring, including a standard single-mode optical fiber, a hollow silica capillary tube, and a large-diameter multi-mode fiber. The results demonstrate that the acoustic wave, when transferring through an adhesive coupler, interferes coherently even when the main and ring fibers are of different types. Finally, we demonstrate that the FRR can be applied for sensing applications by measuring the mode attenuations in the ring due to a changing external environment (water-level sensing) and measuring the optical-path length change in the ring (temperature sensing).

Digital OPLL-based distributed Brillouin sensing system in optical fibers.

A digital optical phase-locked loop (OPLL) has been implemented to develop a distributed Brillouin sensing system in optical fibers. In our experiment, two commercial semiconductor lasers are phase-locked to each other with a highly flexible offset frequency using field programmable gate array (FPGA)-based electronics. Then, the difference frequency between the two lasers is highly stabilized and scanned by a desired step frequency in the vicinity of the Brillouin frequency of standard single-mode optical fibers. Consequently, the distribution of Brillouin frequency shift over a 50 km-long sensing fiber has been successfully measured by a very simple and low-cost Brillouin optical time-domain reflectometry (BOTDR) sensing system without any penalty in the sensing performance. The measurement repeatability at 50 km position of sensing fiber with a 5 m spatial resolution was measured be 4.5 MHz under fast measurement conditions: the number of trace averaging of 2000 and the frequency scan step of 12.8 MHz, showing the figure-of-merit of 3.0.