Showing papers on "Polarization-maintaining optical fiber published in 2016"

Negative Curvature Hollow-Core Optical Fiber

Abstract: The background, optical properties, and applications of low-loss negative curvature hollow-core fiber are reviewed. Data on spectral attenuation are collated and extended.

Manipulation of Group-Velocity-Locked Vector Solitons From Fiber Lasers

Abstract: Manipulation of group-velocity-locked vector solitons (GVLVSs) is numerically proposed and experimentally demonstrated. A pseudo-high-order GVLVS could be generated from a fundamental GVLVS with the help of a polarization-resolved system. Specifically, a pseudo-high-order GVLVS with a two-humped pulse along one polarization and a single-humped pulse along the orthogonal polarization could be obtained. The phase difference between the two humps could be 180°.

Dense Space Division Multiplexed Transmission Over Multicore and Multimode Fiber for Long-haul Transport Systems

Abstract: In this paper, we review recent progress on space division multiplexed (SDM) transmission and our proposal of dense SDM (DSDM) with more than 30 spatial channels toward capacities beyond petabit/s. Furthermore, we discuss the requirements for realizing long-haul DSDM transport systems using multicore and/or multimode fiber, including power and space efficient amplification schemes, the use of fibers with large effective areas and transmission lines with low intercore crosstalk, low differential mode delay (DMD), and low mode dependent loss (MDL). Graded index heterogeneous 12-core × 3-mode fiber with low crosstalk, low DMD, and low MDL, parallel multiple-input and multiple-output signal processing, low mode dependent gain Erbium-doped fiber amplifiers, and MDL equalization technologies are significant as regards extending the reach of multicore and multimode transmission. We review our long-distance transmission experiment on polarization-division multiplexed 16-quadrature amplitude modulation signaling over 12-core × 3-mode fiber.

A New Type Circular Photonic Crystal Fiber for Orbital Angular Momentum Mode Transmission

Abstract: We proposed a new circular photonic crystal fiber (C-PCF), which can support 14 orbital angular momentum (OAM) modes transmission, with the good features of wide bandwidth, low confinement loss, and all OAM modes at the same size. At 1.55 μm, the designed C-PCF has a very low confinement loss of 3.434 × 10 -9 dB/m for HE41 mode and a relatively low nonlinear coefficient of 3.979 W -1 km -1 for EH 31 mode. The common bandwidth for the four orders of OAM modes is as large as 560 nm (about 1.25 μm-1.81 μm), which does cover all bands of optical fiber communication. Flat dispersion (a total dispersion variation of <;46.38 ps nm -1 km -1 over a 750-nm bandwidth from 1.25 μm to 2 μm for TE 01 mode) is another feature. With all these good features, the proposed C-PCF could be a well-promising OAM fiber for mode division multiplexing in high capacity fiber communication systems.

4 Tb/s Transmission Reach Enhancement Using 10 × 400 Gb/s Super-Channels and Polarization Insensitive Dual Band Optical Phase Conjugation

Abstract: In this paper, we experimentally demonstrate the benefit of polarization insensitive dual-band optical phase conjugation for up to ten 400 Gb/s optical super-channels using a Raman amplified transmission link with a realistic span length of 75 km. We demonstrate that the resultant increase in transmission distance may be predicted analytically if the detrimental impacts of power asymmetry and polarization mode dispersion are taken into account.

Narrow linewidth, single mode 3 kW average power from a directly diode pumped ytterbium-doped low NA fiber amplifier

Abstract: We report on a newly designed and fabricated ytterbium-doped large mode area fiber with an extremely low NA (~0.04) and related systematic investigations on fiber parameters that crucially influence the mode instability threshold. The fiber is used to demonstrate a narrow linewidth, continuous wave, single mode fiber laser amplifier emitting a maximum output power of 3 kW at a wavelength of 1070 nm without reaching the mode-instability threshold. A high slope efficiency of 90 %, excellent beam quality, high temporal stability, and an ASE suppression of 70 dB could be reached with a signal linewidth of only 170 pm.

C-Band Q-Switched Fiber Laser Using Titanium Dioxide (TiO 2 ) As Saturable Absorber

Abstract: We demonstrate a passively Q-switched erbium fiber laser using titanium dioxide (TiO 2) as a saturable absorber. The TiO 2 saturable absorber was fabricated as a polymer composite film and sandwiched between fiber ferrules. Q-switched pulsing starts with the assistance of physical disturbance of the laser cavity (by lightly tapping the cavity to induce instability) at 140 mW and lasts until 240 mW. The repetition rate increases with the pump power from 80.28 to 120.48 kHz. On the other hand, the pulsewidth decreases from $2.054\ \mu\text{s}$ until it reaches a plateau at $1.84\ \mu\text{s}$ . The Q-switched fiber laser exhibits two competing modes: at 1558.1 and 1558.9 nm as the pump power increases. A high signal-to-noise ratio of 49.65 dB is obtained.

High-order random Raman lasing in a PM fiber with ultimate efficiency and narrow bandwidth.

Abstract: Random Raman lasers attract now a great deal of attention as they operate in non-active turbid or transparent scattering media. In the last case, single mode fibers with feedback via Rayleigh backscattering generate a high-quality unidirectional laser beam. However, such fiber lasers have rather poor spectral and polarization properties, worsening with increasing power and Stokes order. Here we demonstrate a linearly-polarized cascaded random Raman lasing in a polarization-maintaining fiber. The quantum efficiency of converting the pump (1.05 μm) into the output radiation is almost independent of the Stokes order, amounting to 79%, 83%, and 77% for the 1(st) (1.11 μm), 2(nd) (1.17 μm) and 3(rd) (1.23 μm) order, respectively, at the polarization extinction ratio >22 dB for all orders. The laser bandwidth grows with increasing order, but it is almost independent of power in the 1-10 W range, amounting to ~1, ~2 and ~3 nm for orders 1-3, respectively. So, the random Raman laser exhibits no degradation of output characteristics with increasing Stokes order. A theory adequately describing the unique laser features has been developed. Thus, a full picture of the cascaded random Raman lasing in fibers is shown.

Single multimode fiber endoscope

Abstract: An example multimode fiber endoscope may include an elongated body having a proximal end and a distal end; a multimode fiber disposed within the elongated body and extending from the proximal end to the distal end of the elongated body; a light source disposed relative to the proximal end of the elongated body; a light detector disposed relative to the proximal end of the elongated body; and multiple optical elements disposed between the light source and the multimode fiber. One or more of the optical elements are configured to direct light from the light source into the multimode fiber. One or more of the optical elements are configured to direct light from the multimode fiber to the detector. In some embodiments, the multimode fiber may be a single multimode fiber.

High Sensitivity Twist Sensor Based on Helical Long-Period Grating Written in Two-Mode Fiber

Abstract: We demonstrate the fabrication of the helical long-period grating (HLPG) in a two-mode fiber (TMF) with CO2 laser. The torsion characteristics of the helical gratings are experimentally investigated. It was found that the resonance wavelength of the TMF-HLPG linearly shifts with a twist sensitivity of 0.47 nm/(rad/m), which is an order magnitude higher than that of the conventional long-period fiber gratings (LPFGs). The temperature sensitivity of the TMF-HPFG was measured to be 23.9 pm/°C, which is one third of that of the conventional LPFGs. The proposed TMF-HLPG-based twist sensor would have a promising application for the twist monitor.

Diode-pumped narrow linewidth multi-kilowatt metalized Yb fiber amplifier

Abstract: We investigate high brightness pumping of a multi-kilowatt Yb fiber amplifier in a bi-directional pumping configuration. Each pump outputs 2 kW in a 200 μm, 0.2 NA multimode fiber. Gold-coated specialty gain fibers, with a 17 μm mode field diameter and a 5 dB/m pump absorption, have been developed. The maximum fiber amplifier output power is 3.1 kW, limited by multimode instability, with 90% O-O efficiency and M2<1.15. The fiber amplifier linewidth is 12 GHz.

Dual-Wavelength Soliton Mode-Locked Fiber Laser With a WS 2 -Based Fiber Taper

Abstract: Recently, few-layer WS2, as a novel two-dimensional (2D) material, has been discovered to possess both the saturable absorption effect and the huge nonlinear refractive index. In experiment, by taking advantage of the unique optical properties of 2D WS2, we fabricated a highly nonlinear photonic device using the pulsed laser beam to deposit the WS2 film onto a fiber taper. With the WS2-based fiber taper, we have demonstrated the single- and dual-wavelength soliton pulses in the erbium-doped fiber laser (EDFL) by properly adjusting the pump strength and the polarization state. According to the soliton theory, the pulse width is $\sim 220$ fs for the single-wavelength soliton, and $\sim 585$ and $\sim 605$ fs for the dual-wavelength soliton, respectively. The dual-wavelength soliton fiber laser exhibits the maximum output power of 10.1 mW and the pulse energy of $\sim 1.14$ nJ, when the pump power is increased to $\sim 420$ mW. Our findings suggest that WS2-based fiber taper could operate as both an excellent saturable absorber for obtaining a femtosecond pulse and a promising highly nonlinear photonic material for the multi-wavelength generation.

Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide

Abstract: A polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer (MZI) coated with graphene oxide (GO) film was proposed. The MZI was constructed by fusion splicing a ∼15-mm long polarization maintaining fiber (PMF) between a waist-enlarged taper and a core-offset. The cladding of the PMF was etched off 10 μm, A GO film with the maximum thickness of 4–5 μm was coated on the etched cladding by optically driven deposition. With the strong hydrophilic of the GO and the characteristics of the MZI, the maximum sensitivity of 0.349 dB/%RH with a good stability at the RH range of 60–77% was obtained, which has a linear correlation coefficient of 98.9%.

Actively mode-locked all fiber laser with cylindrical vector beam output

Abstract: We demonstrated an all fiber actively mode-locked laser that emits a cylindrical vector beam. An intra-cavity few-mode fiber Bragg grating inscribed in a short section of four-mode fiber is employed to provide mode selection and spectrum filtering functions. Mode coupling is achieved by offset splicing between the single-mode fiber and the four-mode fiber in the laser cavity. A LiNbO3 Mach-Zehnder modulator is used to achieve active mode-locking in the laser. The laser operates at 1547 nm with 30 dB spectrum width of 0.2 nm. The mode-locked pulses have a duration of 2 ns and repetition of 12.06 MHz. Through adjusting the polarization state in the laser cavity, both radially and azimuthally polarized beams have been obtained with high mode purity.

Optical vortex generation with wavelength tunability based on an acoustically-induced fiber grating.

Abstract: We presented a method to actualize the optical vortex generation with wavelength tunability via an acoustically-induced fiber grating (AIFG) driven by a radio frequency source. The circular polarization fundamental mode could be converted to the first-order optical vortex through the AIFG, and its topological charges were verified by the spiral pattern of coaxial interference between the first-order optical vortex and a Gaussian-reference beam. A spectral tuning range from 1540 nm to 1560 nm was demonstrated with a wavelength tunability slope of 4.65 nm/kHz. The mode conversion efficiency was 95% within the whole tuning spectral range.

All PM Fiber Laser Mode Locked With a Compact Phase Biased Amplifier Loop Mirror

Abstract: An Yb-doped, all-polarization-maintaining fiber laser oscillator with a nonlinear amplifying loop mirror is presented in this letter. A new compact non-reciprocal phase shifter biased fiber loop mirror was engaged inside the fiber laser, which results in a low threshold and stable mode locking. With a 2.8-nm filter inside the cavity, the mode locked output power is 4.1 mW with the repetition rate of 31.35 MHz at the pump power of 80 mW. The spectral bandwidth of the pulse is 3.1 nm. The pulsewidth of the direct output and the dechirped pulse are 2.13 ps and 538 fs, respectively. The filter bandwidth plays a significant role in the spectrum bandwidth and the direct output pulse width.

Broadband high birefringence and polarizing hollow core antiresonant fibers

Abstract: We systematically study different approaches to introduce high birefringence and high polarization extinction ratio in hollow core antiresonant fibers. Having shown the ineffectiveness of elliptical cores to induce large birefringence in hollow core fibers, we focus on designing and optimizing polarization maintaining Hollow Core Nested Antiresonant Nodeless Fibers (HC-NANF). In a first approach, we create and exploit anti-crossings with glass modes at different wavelengths for the two polarizations. We show that suitable low loss high birefringence regions can be obtained by appropriately modifying the thickness of tubes along one direction while leaving the tubes in the orthogonal direction unchanged and in antiresonance. Using this concept, we propose a new birefringent NANF design providing low loss (~40dB/km) and high birefringence (>10−4) over a record bandwidth of ~550nm, and discuss how bandwidth can be traded off to further reduce the loss to a few dB/km. Finally, we propose a polarization mode-stripping technique in the birefringent NANF. As a demonstration, we propose a polarizing birefringent NANF design that can achieve orthogonal polarization loss ratios as large as 30dB over the C-band while eliminating any undesirable polarization coupling effect thereby resulting in a single polarization output in a hollow core fiber regardless of the input polarization state.

Temperature Sensor Based on Fiber Ring Laser With Sagnac Loop

Abstract: In this letter, a temperature sensor based on a fiber ring laser with a reflective Sagnac loop is proposed. The reflective Sagnac loop inserted into the fiber ring laser through a downlead optical fiber is used as the filter and sensing head to supply high temperature sensitivity. As the temperature varies, the transmission spectrum of Sagnac loop changes, leading to the shift of emission wavelength of a fiber ring laser. We obtain a temperature sensor system with a high temperature sensitivity of 1.739 nm/°C, a narrow 3-dB bandwidth less than 0.05 nm, and a high signal-to-noise ratio $\sim 50$ dB. Moreover, it is convenient to achieve the remote sensing by changing the length of the downlead optical fiber.

Design and fabrication of elliptical-core few-mode fiber for MIMO-less data transmission

Abstract: We propose a design strategy of elliptical core few-mode fiber (e-FMF) that supports three spatial modes with enhanced mode spacing between LP11a and LP11b, to suppress intra-mode coupling during mode-division multiplexing (MDM) transmission. Our theoretical investigations show that there exist two optimization regimes for the e-FMF, as a comparison with traditional circular core FMF(c-FMF). At the regime of three-mode operation, there occurs a trade-off between mode spacing and bending-induced loss. Meanwhile, in terms of five-mode regime, a trade-off between mode spacing and high-order mode crosstalk happens. Finally, we fabricate 7.94 km e-FMF with the optimal parameters, based on the commercial fiber manufacture facility. The primary characterizations at 1550 nm show that three spatial modes of e-FMF can be transmitted with a loss less than 0.3 dB/km. Meanwhile, −22.44 dB crosstalk between LP11a and LP11b is observed, even when the 2 km e-FMF is under stress-induced strong perturbation.

Ultra-compact strain- and temperature-insensitive torsion sensor based on a line-by-line inscribed phase-shifted FBG

Abstract: A novel temperature- and strain-independent optical fiber torsion sensor based on a phase-shifted fiber Bragg grating (PSFBG) inscribed by the line-by-line (LbL) technique in a standard single-mode fiber with a femtosecond laser has been proposed and experimentally demonstrated. The strong birefringence created by the LbL inscription technique leads to the significant polarization splitting of the transmission peak of the PSFBG. By simply monitoring the variation of the amplitude difference between the two polarization-peaks, the fiber torsion angle and the fiber torsion direction can be simultaneously deduced without temperature and strain confusion. The torsion sensor exhibits a high torsion sensitivity of up to -1032.71 dB/(rad/mm), with the distinct advantages of low manufacture cost, small dimension (just ~1.72mm), and extremely robust and simple structure, which make it very attractive for practical applications. To the best of our knowledge, this is the smallest torsion sensor ever reported.

105.1 Tb/s power-efficient transmission over 14,350 km using a 12-core fiber

Abstract: We demonstrate the use of MCF for power efficient ultra-high capacity long haul transmission. Feasibility of 105.1 Tb/s transmission over 14,350 km is shown using 12-core fiber and power equivalent of a single pump laser.

Ultrasensitive Refractive-Index Sensors Based on Tapered Fiber Coupler With Sagnac Loop

Abstract: A kind of compact and highly sensitive refractive-index sensor based on reflective tapered fiber coupler is proposed. The sensing structure is fabricated by fusing and tapering a twisted optical fiber. The achieved maximum sensitivity is 3617 nm/RIU for measuring refractive index ranging from 1.33 to 1.41. Comparing with other similar reflective devices, the transmission loss is relatively low ( $\sim 2$ dB), which is assigned to the employed Sagnac loop mirror to enhance the reflection of the system. Besides the intrinsic advantages of the reflective configuration, the proposed sensing structure has the additional advantages of compactness, low-cost, and ultrahigh sensitivity. It is also promising and cost effective for other all-fiber device applications.

Ultra-dense spatial-division-multiplexed optical fiber transmission over 6-mode 19-core fibers.

Abstract: Ultra-dense spatial-division multiplexing (SDM) is achieved by mode multiplexed technique with multiple cores in a single fiber, namely few-mode multi-core fiber. Using a 9.8-km six-mode nineteen-core fiber, we demonstrate an ultra-dense SDM transmission of 16-channels wavelength-division-multiplexed (WDM) dual-polarization quadrature phase shift keying signals, achieving a record spatial multiplicity of 114. With the help of ultra-dense Super-Nyquist WDM techniques in the 4.5-THz bandwidth of the full C-band, we demonstrate 2.05 Pbit/s transmission over 9.8-km six-mode nineteen-core fibers. In this experiment, the highest aggregate spectral efficiency of 456 bit/s/Hz is achieved.

Off-axis ultraviolet-written fiber Bragg gratings for directional bending measurements

Abstract: Off-axis fiber Bragg gratings are inscribed by ultraviolet irradiation limited to expose only a portion of the fiber core cross section. The coupling to cladding modes is significantly increased, and the amplitude of the cladding mode resonances becomes sensitive to bending in magnitude and direction. Sensitivities ranging from +1.17 dB/m(-1) to -1.25 dB/m(-1) were obtained for bending in different directions relative to the offset direction of the grating, for curvatures from 0 to 1.1 m(-1), a range ideal for the shape sensing of large structures. The bending sensor response is also shown to be independent of temperature and the surrounding refractive index.

Low-Differential-Mode-Group-Delay 9-LP-Mode Fiber

Abstract: We report the optimization of a few-mode fiber, adapted to multiple-input multiple-output mode division multiplexing, that supports 9 LP modes (15 spatial modes). The fiber is fabricated using standard multimode processes, which allows for tight process tolerances, yielding low differential mode group delays (<155 ps/km) with low attenuations (<0.22 dB/km), large effective areas (≥95 μm2) and low bend losses.

Low-loss and Low-DMD few-mode multi-core fiber with highest core multiplicity factor

Abstract: We demonstrate 246 μm cladding 6-mode 19-core fiber and realize twice the spatial density of other multi-core fiber with more than 100 channels, while achieving the lowest loss and differential mode delay of 0.33 ns/km.

Design and Analysis of a Microstructure Ring Fiber for Orbital Angular Momentum Transmission

Abstract: In this paper, we propose a novel microstructure fiber with annular core for transmitting optical orbital angular momentum (OAM), and the OAM modes are calculated under different structure parameters of the fiber. Compared with the previous hollow step-index ring fiber, the proposed fiber brings higher refractive index contrast between the ring core and the cladding region by using only the single material of silica. The designed fiber can support more well-separated OAM modes with both thin and thick rings. Simulation results show that the novel microstructure ring fiber is promising to be applied in fiber-based OAM multiplexing in order to improve communication capacity.

Long-Range Distributed Fiber Vibration Sensor Using an Asymmetric Dual Mach–Zehnder Interferometers

Abstract: An asymmetric dual Mach–Zehnder interferometry (ADMZI) design is proposed to achieve distributed fiber vibration sensing at long range. In this structure, we utilized two distributed feedback laser beams and dense wavelength-division multiplexing to significantly reduce the influence of Rayleigh backscattering noise, which will seriously deteriorate the signal noise ratio (SNR) in traditional dual Mach–Zehnder interferometer (DMZI) sensor. At the sensing length of 61 km, the SNR achieved using the ADMZI design is 20 dB higher than that using the DMZI design. Using a positioning algorithm based on the time–frequency analysis, the positioning mean square error can reach 52.5 m at this distance.

Wavelength-switchable fiber laser based on few-mode fiber filter with core-offset structure

Abstract: We propose a wavelength-switchable erbium-doped fiber ring laser based on the few-mode fiber filter with core-offset structure. The filter is constructed by splicing a section of few-mode fiber with two segments of single mode fiber. Meanwhile, the excited modes are effectively selected by controlling the core-offset splicing carefully. The novel filter is based on the interference between fundamental mode and LP 11 mode. The single-, dual-, triple- and quad-wavelength fiber laser is accomplished by adjusting the states of polarization controller at room temperature. The principle of operation is mainly based on the saturated spectral hole-burning effect and the balance between the gain and loss in the cavity.