Showing papers on "Dispersion-shifted fiber published in 2015"

2.15 Pb/s transmission using a 22 core homogeneous single-mode multi-core fiber and wideband optical comb

Abstract: We use a wideband optical comb source with 10THz bandwidth for 2.15 Pb/s transmission over 31km of a new, homogeneous 22-core single-mode multi-core fiber using 399 × 25GHz spaced, 6.468 Tb/s spatial-super-channels comprising 24.5GBaud PDM-64QAM modulation in each core.

Controllable all-fiber orbital angular momentum mode converter.

Abstract: We present a scheme to realize a controllable, scalable, low-cost, and versatile all-fiber orbital angular momentum (OAM) converter. The converter consists of a two-mode fiber (TMF) with its input terminal welded with a single-mode fiber, a mechanical long-period grating (LPG), a mechanical rotator, metal flat slabs, and a fiber polarization controller. The LPG is employed to convert the fundamental fiber mode to higher-order modes and the flat slabs are used to stress the TMF to adjust the relative phase difference between two orthogonal higher-order modes. Selective conversion from the LP(01) mode to the LP(11a), LP(11b), OAM(-1), or OAM(+1) mode is demonstrated in the experiment.

Compact fiber-optic curvature sensor based on super-mode interference in a seven-core fiber.

Abstract: A compact, low loss, and highly sensitive optical fiber curvature sensor is presented. The device consists of a few-millimeter-long piece of seven-core fiber spliced between two single-mode fibers. When the optical fiber device is kept straight, a pronounced interference pattern appears in the transmission spectrum. However, when the device is bent, a spectral shift of the interference pattern is produced, and the visibility of the interference notches changes. This allows for using either visibility or spectral shift for sensor interrogation. The dynamic range of the device can be tailored through the proper selection of the length of the seven-core fiber. The effects of temperature and refractive index of the external medium on the response of the curvature sensor are also discussed. Linear sensitivity of about 3000 nm/mm−1 for bending was observed experimentally.

Topological Insulator Solution Filled in Photonic Crystal Fiber for Passive Mode-Locked Fiber Laser

Abstract: We first reported that the topological insulator (TI) nanosheets solution filled in photonic crystal fiber can operate as an effective saturable absorber (SA) with the merits of low-insertion loss ( $\sim 0.42$ dB), long interaction length (>10 cm), and high-power tolerance. This SA device exhibited a saturable intensity of 14.9 MW/ $\mathrm{cm}^{2}$ , modulation depth of 19.1%, and nonsaturable loss of 25% at 1060 nm. Upo employing, this device rendered us to establish an ytterbium-doped all-fiber laser oscillator, where stable evanescent wave mode-locking operation has been achieved. This letter provided a new way of utilizing the unique nonlinear optical property of TI.

High Power Random Fiber Laser With Short Cavity Length: Theoretical and Experimental Investigations

Abstract: In this paper, we make a comprehensive study on a highly efficient half-open cavity design for high power random fiber laser (RFL). With the theoretical analysis, we optimize the cavity's fiber length for getting higher output power within the scheme, i.e., shorter fiber length is preferred for efficiently harvesting the first order random lasing at the open end of the cavity. As the verification of the theory, we experimentally demonstrate a high output power (7 W), highly efficient (70% optical conversion efficiency) RFL working at 1140 nm, using 10 W 1090 nm laser as the pump source and only 1 km standard single-mode fiber as the distributed cavity.

100 Gbit/s WDM transmission at 2 µm: transmission studies in both low-loss hollow core photonic bandgap fiber and solid core fiber

Abstract: We show for the first time 100 Gbit/s total capacity at 2 µm waveband, using 4 × 9.3 Gbit/s 4-ASK Fast-OFDM direct modulation and 4 × 15.7 Gbit/s NRZ-OOK external modulation, spanning a 36.3 nm wide wavelength range. WDM transmission was successfully demonstrated over 1.15 km of low-loss hollow core photonic bandgap fiber (HC-PBGF) and over 1 km of solid core fiber (SCF). We conclude that the OSNR penalty associated with the SCF is minimal, while a ~1-2 dB penalty was observed after the HC-PBGF probably due to mode coupling to higher-order modes.

Highly-sensitive gas pressure sensor using twin-core fiber based in-line Mach-Zehnder interferometer

Abstract: A Mach-Zehnder interferometer based on a twin-core fiber was proposed and experimentally demonstrated for gas pressure measurements. The in-line Mach-Zehnder interferometer was fabricated by splicing a short section of twin-core fiber between two single mode fibers. A micro-channel was created to form an interferometer arm by use of a femtosecond laser to drill through one core of the twin-core fiber. The other core of the fiber was remained as the reference arm. Such a Mach-Zehnder interferometer exhibited a high gas pressure sensitivity of −9.6 nm/MPa and a low temperature cross-sensitivity of 4.4 KPa/°C. Moreover, ultra-compact device size and all-fiber configuration make it very suitable for highly-sensitive gas pressure sensing in harsh environments.

Multipoint Two-Dimensional Curvature Optical Fiber Sensor Based on a Nontwisted Homogeneous Four-Core Fiber

Abstract: We have implemented a multipoint two-dimensional curvature optical fiber sensor based on a nontwisted homogeneous four-core fiber. A theoretical approach to model the mechanical behavior of these fibers under curvature conditions has been developed. Two shape sensors composed of an array of FBGs inscribed in the four-core fiber have been implemented to corroborate the theoretical analysis with the experimental results. The characterization of the proposed shape sensors showed their ability to measure the curvature radius, the curvature direction, and any external applied force related to both uniform and nonuniform curvatures with high accuracy.

High-density multicore fiber with heterogeneous core arrangement

Abstract: A 30-core fiber with heterogeneous cores that achieved large spatial multiplicity and low crosstalk of less than −40 dB at 100 km was demonstrated. The correlation lengths were estimated to be more than 1 m.

Distributed Strain and Vibration Sensing System Based on Phase-Sensitive OTDR

Abstract: A system based on phase-sensitive optical time domain reflectometry is proposed for simultaneously strain and vibration sensing. The strain of fiber is detected by comparing the patterns of signal for different laser frequencies, and the vibration of fiber is detected simultaneously from the signals for any certain laser frequency. During the measurement, frequencies of the probe optical pulses are modulated sequentially in ascending or descending order. Using the signals generated by optical pulses with the same frequency, the vibration of fiber is detected with fast response speed; using that with different frequencies, the strain of fiber is detected with high resolution. In our experiment, a sensing system with 2-m spatial resolution, up to 1-kHz frequency measurement range and 10- $\text{n}{{\varepsilon }}$ strain resolution is realized for a 9-km sensing fiber length.

Ultrafast Pulsed All-Fiber Laser Based on Tapered Fiber Enclosed by Few-Layer WS 2 Nanosheets

Abstract: We demonstrate all-fiber mode-locked laser based on a tapered optical fiber saturable absorber (SA) enclosed in tungsten disulfide (WS2) nanosheets. Tapered fibers were fabricated using the standard flame brushing method to an interaction length of 3 mm with waist diameters of 10 and 15 $\mu \text{m}$ . WS2 nanosheets were prepared via a liquid phase exfoliation method to form a uniform dispersion. Subsequently, the WS2 nanosheets were optically deposited along the interaction length of the tapered fibers by evanescent field interactions. We built a ring laser including the fabricated mode-lockers. The SA with a 10- $\mu \text{m}$ taper diameter delivers the pulses with a pulse duration of 369 fs and 3-dB spectral bandwidth of 7.5 nm; on the other hand, the output pulses using the mode-locker with 15- $\mu \text{m}$ waist diameter were found to have 563-fs pulse duration and 5.2 nm of 3-dB bandwidth. It is shown that the smaller waist diameter of tapered fiber causes wider spectral bandwidth of the ultrafast pulses and narrower 3-dB bandwidth.

Demonstration of ultra-low NA rare-earth doped step index fiber for applications in high power fiber lasers.

Abstract: In this paper, we report the mode area scaling of a rare-earth doped step index fiber by using low numerical aperture. Numerical simulations show the possibility of achieving an effective area of ~700um2 (including bend induced effective area reduction) at a bend diameter of 32cm from a 35μm core fiber with a numerical aperture of 0.038. An effective single mode operation is ensured following the criterion of the fundamental mode loss to be lower than 0.1dB/m while ensuring the higher order modes loss to be higher than 10dB/m at a wavelength of 1060nm. Our optimized modified chemical vapor deposition process in conjunction with solution doping process allows fabrication of an Yb-doped step index fiber having an ultra-low numerical aperture of ~0.038. Experimental results confirm a Gaussian output beam from a 35μm core fiber validating our simulation results. Fiber shows an excellent laser efficiency of ~81%and aM2 less than 1.1.

2.05 Peta-bit/s super-nyquist-WDM SDM transmission using 9.8-km 6-mode 19-core fiber in full C band

Abstract: We demonstrate ultra-dense SDM transmission of 360-channel Super-Nyquist-WDM DP-QPSK signals over 9.8-km 6-mode 19-core fiber, achieving the record fiber capacity of 2.05 Pbit/s (360WDM×114SDM×50Gbit/s) with the highest aggregate spectral efficiency of 456 bit/s/Hz.

Low loss Ge-As-Se chalcogenide glass fiber, fabricated using extruded preform, for mid-infrared photonics

Abstract: Chalcogenide glass fibers have attractive properties (e.g. wide transparent window, high optical non-linearity) and numerous potential applications in the mid-infrared (MIR) region. Low optical loss is desired and important in the development of these fibers. Ge-As-Se glass has a large glass-forming range to provide versatility of choice from continuously varying physical properties. Recently, broadband MIR supercontinuum generation has been achieved in chalcogenide fibers by using Ge-As-Se glass in the core/clad. structure. In the shaping of chalcogenide glass optical fiber preforms, extrusion is a useful technique. This work reports glass properties (viscosity-temperature curve and glass transition) and optical losses of Ge-As-Se fiber fabricated from an extruded preform. A robust cut-back method of fiber loss measurement is developed and the corresponding error calculation discussed. MIR light is propagated through 52 meters of a fiber, which has the lowest loss yet reported for Ge-As-Se fiber of 83 ± 2 dB/km at 6.60 μm wavelength. The fiber baseline loss is 83-90 dB/km across 5.6-6.8 μm, a Se-H impurity absorption band of 1.4 dB/m at 4.5 μm wavelength is superposed and other impurity bands (e.g. O-H, As-O, Ge-O) are ≤ 20 dB/km. Optical losses of fiber fabricated from different positions of the extruded preform are investigated.

Generation of 8 nJ pulses from a normal-dispersion thulium fiber laser

Abstract: We report a study of a mode-locked thulium (Tm) fiber laser with varying normal dispersion. It is difficult to reach the high-energy dissipative-soliton regime due to the anomalous dispersion of most fibers at 2 μm. With large normal dispersion, the laser exhibits elements of self-similar pulse evolution, and is the first Tm fiber laser to achieve the performance benefits of normal-dispersion operation. The laser generates 7.6 nJ pulses, which can be dechirped to 130 fs duration. The resulting peak power is 4 times higher than that of previous Tm fiber lasers.

Design of eight-mode polarization-maintaining few-mode fiber for multiple-input multiple-output-free spatial division multiplexing.

Abstract: We propose a polarization-maintaining few-mode fiber (FMF) that features an elliptical ring shaped core with a high refractive index contrast ∼0.03 between the core and the cladding. This fiber design alleviates the usual trade-off between the number of guided modes and the achievable birefringence that is usually observed in conventional elliptical-core FMFs. Through numerical simulations, we show that this fiber design can support up to 10 guided vector modes over the entire C band while providing large birefringence. Except for the two fundamental modes, the eight higher-order vector modes are all separated from their adjacent modes by effective index differences >10⁻⁴, which is the typical birefringence value of single-mode polarization maintaining fibers. The designed fiber targets applications in spatial division multiplexing of optical channels, without multiple-input-multiple-output (MIMO) digital signal processing, for short-reach optical interconnects.

Lossy Mode Resonance (LMR) Based Fiber Optic Sensors: A Review

Abstract: In the past few decades, surface plasmon resonance (SPR) phenomenon along with optical fiber technology has emerged as a major area of research among the fiber optic sensing research groups. On the other hand, lossy mode resonance (LMR) is another kind of resonance phenomenon recently exploited for fiber optic sensing. LMR has several advantages over the well established SPR such as, free from specific polarization of light and capability of multiple LMR generation. Since LMR phenomenon is nascent for researchers and there are no review articles available till date, in this paper, we review the LMR phenomenon in applications involving sensing and wavelength filtering.

Dual-Wavelength Single-Longitudinal-Mode Tm-Doped Fiber Laser Using PM-CMFBG

Abstract: We have demonstrated a dual-wavelength thulium-doped fiber laser with single-longitudinal-mode (SLM) operation at $\sim 2$ - $\mu \text{m}$ region. A polarization-maintaining chirped Moire fiber Bragg grating was employed as a polarization-dependent narrow-band filter, to suppress multilongitudinal-mode oscillation. Single-and dual-wavelength switchable operation was achieved by simply adjusting the polarization controller. We also showed that the laser lines retained SLM operation with the additional benefit of single polarization. Meanwhile, the dependence of each laser wavelength on the pump power was also investigated in detail.

Optical fiber design with orbital angular momentum light purity higher than 99.9.

Abstract: The purity of the synthesized orbital-angular-momentum (OAM) light in the fiber is inversely proportional to channel crosstalk level in the OAM optical fiber communication system. Here the relationship between the fiber structure and the purity is firstly demonstrated in theory. The graded-index optical fiber is proposed and designed for the OAM light propagation with the purity higher than 99.9%. 16 fiber modes (10 OAM modes) have been supported by a specific designed graded-index optical fiber with dispersion less than 35 ps/(km∙nm). Such fiber design has suppressed the intrinsic crosstalk to be lower than -30 dB, and can be potentially used for the long distance OAM optical communication system.

A Stable Dual-wavelength Thulium-doped Fiber Laser at 1.9 μm Using Photonic Crystal Fiber.

Abstract: A stable dual-wavelength thulium-doped fiber laser operating at 1.9 μm using a short length of photonic crystal fiber (PCF) has been proposed and demonstrated. The photonics crystal fiber was 10 cm in length and effectively acted as a Mach-Zehnder interferometry element with a free spectral range of 0.2 nm. This dual-wavelength thulium-doped fiber laser operated steadily at room temperature with a 45 dB optical signal-to-noise-ratio.

Watt-level passively mode-locked Er(3+)-doped ZBLAN fiber laser at 2.8 μm.

Abstract: We experimentally demonstrated a stable, high-average-power, continuous-wave (CW) passively mode-locked Er3+-doped ZBLAN fiber laser at 2.8 μm based on a semiconductor saturable absorber mirror. A stable mode-locked laser with a signal-to-noise ratio of 52 dB and a slope efficiency of 14% was obtained. The highest average output power in excess of 1 W was generated at the incident pump power of 8.2 W, with a pulse repetition rate of 22.56 MHz and pulse duration of 25 ps. To the best of our knowledge, this is the highest average output power of a CW mode-locked ZBLAN fiber laser in the mid-infrared wavelength regime up to now.

Linearly polarized random fiber laser with ultimate efficiency.

Abstract: Linearly polarized pumping of a random fiber laser made of a 500-m PM fiber with PM fiber-loop mirror at one fiber end results in generation of linearly polarized radiation at 1.11 μm with the polarization extinction ratio as high as 25 dB at the output power of up to 9.4 W. The absolute optical efficiency of pump-to-Stokes wave conversion reaches 87%, which is close to the quantum limit and sets a record for Raman fiber lasers with random distributed feedback and with a linear cavity as well. Herewith, the output linewidth at high powers tends to saturation at a level of 1.8 nm.

Dissipative Soliton Resonance in a Wavelength-Tunable Thulium-Doped Fiber Laser With Net-Normal Dispersion

Abstract: We demonstrate an all-fiber figure-eight mode-locked thulium-doped fiber laser with a wide tunable range in both pulsewidth and wavelength A 45-m-long ultrahigh numerical aperture fiber is used to manage the cavity dispersion, and the net cavity dispersion is calculated to be 08585 ps 2 at 1900 nm With net-normal dispersion, the experimental laser, operating in a dissipative soliton resonance region, generates stable rectangular pulses The pulsewidth varies from 480 ps to 619 ns with the increasing pump power, and its center wavelength has a 2895-nm tunable range (from 194022 to 196917 nm) by properly adjusting the polarization controllers The maximum of average output power and pulse energy is 6073 mW and 1951 nJ, respectively The rectangular pulses have a clamped peak power of about 316 W The wavelength-tunable fiber laser with high-energy output operating at 2 μm has great potential in various application fields

Bending sensor combining multicore fiber with a mode-selective photonic lantern

Abstract: A bending sensor is demonstrated using the combination of a mode-selective photonic lantern (PL) and a multicore fiber. A short section of three-core fiber with strongly coupled cores is used as the bend sensitive element. The supermodes of this fiber are highly sensitive to the refractive index profiles of the cores. Small bend-induced changes result in drastic changes of the supermodes, their excitation, and interference. The multicore fiber is spliced to a few-mode fiber and excites bend dependent amounts of each of the six linearly polarized (LP) modes guided in the few-mode fiber. A mode selective PL is then used to demultiplex the modes of the few-mode fiber. Relative power measurements at the single-mode PL output ports reveal a high sensitivity to bending curvature and differential power distributions according to bending direction, without the need for spectral measurements. High direction sensitivity is demonstrated experimentally as well as in numerical simulations. Relative power shifts of up to 80% have been measured at radii of approximately 20 cm, and good sensitivity was observed with radii as large as 10 m, making this sensing system useful for applications requiring both large and small curvature measurements.

Few-Mode Erbium-Doped Fiber Amplifiers: A Review

Abstract: Space-division multiplexing has brought a fresh perspective to the optical fiber community over the last three years and many global players around the world have been involved with both the theoretical and the experimental questions raised by this promising approach. If this technology is to be introduced in the future optical fiber networks, this implies that most of the optical components of the transmission line, including the popular Erbium-doped fiber amplifiers that lie at the heart of fiber communications need to be reexamined. This study reviews the way the new generation of Erbium-doped fibers affects the recent findings on few-mode fibers and how they may further play a central role in the deployment of this technology.

Dissipative soliton generation in Er-doped fiber laser mode-locked by Sb2Te3 topological insulator.

Abstract: We report on the generation of dissipative solitons in an Er-doped fiber laser mode-locked by antimony telluride (Sb2Te3) topological insulator in the near-zero dispersion regime. Layers of Sb2Te3 were deposited on a side-polished (D-shaped) fiber using a pulsed magnetron sputtering technique. Sub-170-fs pulses with 34-nm full width at half-maximum (FWHM) and 0.21 nJ of pulse energy were obtained from an all-fiber, ring-shaped laser cavity after the compression in a single-mode fiber.

Widely tunable mid-infrared fiber laser source based on soliton self-frequency shift in microstructured tellurite fiber.

Abstract: A turnkey fiber laser source generating high-quality pulses with a spectral sech shape and Fourier transform-limited duration of order 100 fs widely tunable in the 1.6–2.65 μm range is presented. It is based on Raman soliton self-frequency shifting in the suspended-core microstructured TeO2-WO3-La2O3 glass fiber pumped by a hybrid Er/Tm fiber system. Detailed experimental and theoretical studies, which are in a very good agreement, of nonlinear pulse dynamics in the tellurite fiber with carefully measured and calculated parameters are reported. A quantitatively verified numerical model is used to show Raman soliton shift in the range well beyond 3 μm for increased pump energy.

Passively Q-Switched 1.89-μm Fiber Laser Using a Bulk-Structured Bi2Te3 Topological Insulator

Abstract: We experimentally demonstrate that a bulk-structured Bi 2 Te 3 topological insulator (TI) film deposited on a side-polished fiber can act as an effective Q-switch for a 1.89-μm laser. Our bulk-structured Bi 2 Te 3 TI film with a thickness of ~31 μm, was prepared using a mechanical exfoliation method, and the fabricated film was transferred onto a side-polished SM2000 fiber to form a fiberized saturable absorber based on evanescent field interaction. By incorporating the saturable absorber into a thulium (Tm)-holmium (Ho) co-doped fiber-based ring cavity, it is shown that Q-switched pulses with a minimum temporal width of ~1.71 μs can readily be produced at a wavelength of 1.89 μm. The output pulse repetition rate was tunable from ~35 to ~60 kHz depending on the pump power. The maximum output pulse energy was ~11.54 nJ at a pump power of 250 mW. The output performance of our laser is compared to that of the 1.98-μm Q-switched fiber laser based on a nanosheet-based Bi 2 Se 3 TI demonstrated previously by Luo et al.

Dispersion Engineering of Highly Nonlinear Chalcogenide Suspended-Core Fibers

Abstract: Chalcogenide optical fibers are currently undergoing intensive investigation with the aim of exploiting the excellent glass transmission and nonlinear characteristics in the near- and mid-infrared for several applications. Further enhancement of these properties can be obtained, for a particular application, with optical fibers specifically designed that are capable of providing low effective area together with a properly tailored dispersion, matching the characteristics of the laser sources used to excite nonlinear effects. Suspended-core photonic crystal fibers are ideal candidates for nonlinear applications, providing small-core waveguides with large index contrast and tunable dispersion. In this paper, the dispersion properties of As 2 S 3 suspended-core fibers are numerically analyzed, taking into account, for the first time, all the structural parameters, including the size and the number of the glass bridges. The results show that a proper design of the cladding struts can be exploited to significantly change the fiber properties, altering the maximum value of the dispersion parameter and shifting the zero-dispersion wavelengths over a range of 400 nm.

Tm-based fiber-laser system with more than 200 MW peak power.

Abstract: Tm-based fiber-laser systems are an attractive concept for the development of high-performance laser sources in the spectral region around 2 μm wavelength. Here we present a system delivering a pulse-peak power higher than 200 MW in combination with 24 W average power and 120 μJ pulse energy. Key components enabling this performance level are a Tm-doped large-pitch fiber with a mode-field diameter of 65 μm, highly efficient dielectric gratings, and a Tm-based fiber oscillator operating in the stretched-pulse regime.