Showing papers on "Dispersion-shifted fiber published in 2009"
TL;DR: A fiber-optical switch that is activated at tiny energies corresponding to a few hundred optical photons per pulse is demonstrated by simultaneously confining both photons and a small laser-cooled ensemble of atoms inside the microscopic hollow core of a single-mode photonic-crystal fiber.
Abstract: We demonstrate a fiber-optical switch that is activated at tiny energies corresponding to a few hundred optical photons per pulse. This is achieved by simultaneously confining both photons and a small laser-cooled ensemble of atoms inside the microscopic hollow core of a single-mode photonic-crystal fiber and using quantum optical techniques for generating slow light propagation and large nonlinear interaction between light beams.
442 citations
TL;DR: In this article, fundamental measurements of the properties of thulium-doped silica and power scaling studies of fiber lasers based on the material were described. But the results were limited to the case of a 25mum-diameter, 0.08 numerical aperture (NA) core.
Abstract: We describe fundamental measurements of the properties of thulium (Tm)-doped silica and power scaling studies of fiber lasers based on the material. Data on the high-lying Tm:silica energy levels, the first taken to our knowledge, indicate that pumping at 790 nm is unlikely to lead to fiber darkening via multiphoton excitation. Measurement of the cross-relaxation dynamics produces an estimate that, at the doping levels used, as much as 80% of the decay of the Tm level pumped is due to cross relaxation. Using a fiber having a 25-mum-diameter, 0.08 numerical aperture (NA) core, we observed fiber laser efficiencies as high as 64.5% and output powers of 300 W (around 2040 nm) for 500 W of launched pump power, with a nearly diffraction-limited beam. At these efficiencies, the cross-relaxation process was producing 1.8 laser photons per pump photon. We generated 885 W from a multimode laser using a 35-mum, 0.2-NA core fiber and set a new record for Tm-doped fiber laser continuous-wave power.
317 citations
Patent•
05 May 2009
TL;DR: In this paper, a singlemode optical fiber with bending losses of 0.15 dB/turn or less for a radius of curvature of 5 millimeters is presented, at a wavelength of 1550 nanometers.
Abstract: The present invention embraces a single-mode optical fiber that, at a wavelength of 1550 nanometers, has bending losses of 0.15 dB/turn or less for a radius of curvature of 5 millimeters.
257 citations
TL;DR: A 24 W liquid-cooled CW 3 microm fiber laser with a multimode-core Er-doped ZBLAN fiber with stable high-power operation was demonstrated, and this is the highest output power obtained by a 3 micron fiber laser.
Abstract: A 24 W liquid-cooled CW 3 microm fiber laser with a multimode-core Er-doped ZBLAN fiber has been developed. The output power of 24 W and an optical-to-optical efficiency of 14.5% (with respect to incident pump power) were obtained with 975 nm diode pumping. Efficient cooling was implemented by a combination of fluid cooling over the entire length of the fiber and conductive cooling at both end faces of the fiber. Consequently, stable high-power operation was demonstrated. To our knowledge, this is the highest output power obtained by a 3 microm fiber laser. Furthermore, the high power can be further scaled up, since the output power in the present work is limited only by the available pump power.
235 citations
Book•
23 Jun 2009
TL;DR: In this paper, the authors compare back-to-back and single-span transmission and multi-span long-haul transmission for a single-input single-output (SISO) system.
Abstract: Transmitters and Receivers.- Transmitter Design.- Receiver Configurations.- Effort Comparison.- System Performance.- System Simulation Aspects.- Fiber Propagation Effects.- Back-to-Back and Single-Span Transmission.- Multi-Span Long-Haul Transmission.- Performance Trends.
234 citations
TL;DR: It is shown that depending on the strength of the cavity birefringence, stable single-, dual- and triple-wavelength DSs can be formed in the laser.
Abstract: We report on the generation of multi-wavelength dissipative soliton (DS) in an all normal dispersion fiber laser passively mode-locked with a semiconductor saturable absorber mirror (SESAM). We show that depending on the strength of the cavity birefringence, stable single-, dual- and triple-wavelength DSs can be formed in the laser. The multi-wavelength soliton operation of the laser was experimentally investigated, and the formation mechanisms of the multi-wavelength DSs are discussed.
227 citations
Patent•
29 Oct 2009
TL;DR: In this article, a modular, compact and widely tunable laser system for the efficient generation of high peak and high average power ultrashort pulses is proposed, where the output of the fiber amplifiers can be expanded by using optimized pulse shapes, as well as dispersively broadened pulses.
Abstract: A modular, compact and widely tunable laser system for the efficient generation of high peak and high average power ultrashort pulses. Modularity is ensured by the implementation of interchangeable amplifier components. System compactness is ensured by employing efficient fiber amplifiers, directly or indirectly pumped by diode lasers. Peak power handling capability of the fiber amplifiers is expanded by using optimized pulse shapes, as well as dispersively broadened pulses. Dispersive broadening is introduced by dispersive pulse stretching in the presence of self-phase modulation and gain, resulting in the formation of high-power parabolic pulses. In addition, dispersive broadening is also introduced by simple fiber delay lines or chirped fiber gratings, resulting in a further increase of the energy handling ability of the fiber amplifiers. The phase of the pulses in the dispersive delay line is controlled to quartic order by the use of fibers with varying amounts of waveguide dispersion or by controlling the chirp of the fiber gratings. After amplification, the dispersively stretched pulses can be re-compressed to nearly their bandwidth limit by the implementation of another set of dispersive delay lines. To ensure a wide tunability of the whole system, Raman-shifting of the compact sources of ultrashort pulses in conjunction with frequency-conversion in nonlinear optical crystals can be implemented, or an Anti-Stokes fiber in conjunction with fiber amplifiers and Raman-shifters are used. A particularly compact implementation of the whole system uses fiber oscillators in conjunction with fiber amplifiers. Additionally, long, distributed, positive dispersion optical amplifiers are used to improve transmission characteristics of an optical communication system. Finally, an optical communication system utilizes a Raman amplifier fiber pumped by a train of Raman-shifted, wavelength-tunable pump pulses, to thereby amplify an optical signal which counterpropogates within the Raman amplifier fiber with respect to the pump pulses.
227 citations
Patent•
21 Aug 2009TL;DR: In this article, a bending loss of the Holey fiber is shown to be less than 5 dB/m at a wavelength within the operation wavelength band when the fiber is wound at a diameter of 20 millimeters.
Abstract: An optical transmission system includes an optical transmitting unit that outputs at least one optical signal having a wavelength included in an operation wavelength band and a holey fiber that is connected to the optical transmitting unit. The holey fiber includes a core and a cladding formed around the core. The cladding includes a plurality of holes formed around the core in a triangular lattice shape. The holey fiber transmits the optical signal in a single mode. A bending loss of the holey fiber is equal to or less than 5 dB/m at a wavelength within the operation wavelength band when the holey fiber is wound at a diameter of 20 millimeters.
193 citations
TL;DR: This is the first demonstration of mode-locked 2 mum fiber laser using shorter than 1-m-long active fiber, which paves the way for the demonstration ofmode-locked fiber laser at 2 mum with gigahertz fundamental repetition rate.
Abstract: We report self-starting passively mode-locked fiber lasers with a saturable absorber mirror using a piece of 30-cm-long newly developed highly thulium (Tm)-doped silicate glass fibers. The mode-locked pulses operate at 1980 nm with duration of 1.5 ps and energy of 0.76 nJ. This newly developed Tm-doped silicate fiber exhibits a slope efficiency of 68.3%, an amplified spontaneous emission spectrum bandwidth (FWHM) of 92 nm, and a gain per unit length of greater than 2 dB/cm. To the best of our knowledge, it is the first demonstration of mode-locked 2 μm fiber laser using shorter than 1-m-long active fiber, which paves the way for the demonstration of mode-locked fiber laser at 2 μm with gigahertz fundamental repetition rate.
185 citations
TL;DR: A spectrally asymmetric resonator with usual Fiber Bragg gratings is designed to minimize the laser power lost into the unwanted direction, even when the effective reflectivity of the rear fiber Bragg grating becomes as low as 81.5%.
Abstract: We report a more than 150 W spectrally-clean continuous wave Raman fiber laser at 1120 nm with an optical efficiency of 85%. A ~30 m standard single mode silica fiber is used as Raman gain fiber to avoid second Stokes emission. A spectrally asymmetric resonator (in the sense of mirror reflection bandwidth) with usual fiber Bragg gratings is designed to minimize the laser power lost into the unwanted direction, even when the effective reflectivity of the rear fiber Bragg grating becomes as low as 81.5%.
183 citations
TL;DR: To the best of the knowledge, this work has for the first time fabricated a hexagonal core fiber by soft glass with such a small core size, and has demonstrated a large influence of the holey region on the dispersion, nonlinear coefficient and supercontinuum generation for such fiber.
Abstract: Tellurite glass microstructure fibers with a 1 µm hexagonal core were fabricated successfully by accurately controlling the temperature field in the fiber-drawing process The diameter ratio of holey region to core (DRHC) for the fiber can be adjusted freely in the range of 1–20 by pumping a positive pressure into the holes when drawing fiber, which provides much freedom in engineering the chromatic dispersion With the increase of DRHC from 35 to 20, the zero dispersion wavelengths were shifted several hundred nanometers, the cutoff wavelength due to confinement loss was increased from 1600 nm to 3800 nm, and the nonlinear coefficient γ was increased from 39 to 57 W-1/m Efficient visible emissions due to third harmonic generation were found for fibers with a DRHC of 10 and 20 under the 1557 nm pump of a femtosecond fiber laser One octave flattened supercontinuum spectrum was generated from fibers with a DRHC of 35, 10 and 20 by the 1064 nm pump of a picosecond fiber laser To the best of our knowledge, we have for the first time fabricated a hexagonal core fiber by soft glass with such a small core size, and have demonstrated a large influence of the holey region on the dispersion, nonlinear coefficient and supercontinuum generation for such fiber
TL;DR: In this paper, a cladding-pumped ytterbium-doped fiber laser was demonstrated to achieve 2.1 kW of continuous-wave output power at 1.1 µm.
Abstract: We have demonstrated a highly efficient cladding-pumped ytterbium-doped fiber laser, generating >2.1 kW of continuous-wave output power at 1.1 µm with 74% slope efficiency with respect to launched pump power. The beam quality factor (M2) was better than 1.2. The maximum output power was only limited by available pump power, showing no evidence of roll-over even at the highest output power. We present data on how the beam quality depends on the fiber parameter, based on our current and past fiber laser developments. We also discuss the ultimate power-capability of our fiber in terms of thermal management, Raman nonlinear scattering, and material damage, and estimate it to 10 kW
TL;DR: In this paper, a new ultra-low bending loss single-mode fiber with ring comprising nanometer sized features is designed and manufactured, and a bend radius of 5 mm is demonstrated.
Abstract: A new ultra-low bending loss single-mode fiber with ring comprising nanometer sized features is designed and manufactured. Bending loss less than 0.1 dB/turn at 1550 nm and a bend radius of 5 mm is demonstrated. Other optical parameters of the fiber are fully compatible the standard telecommunications grade single-mode fibers.
TL;DR: A simple linear cavity erbium-doped fiber laser based on a Fabry-Perot filter which consists of a pair of fiber Bragg gratings is proposed for tunable and switchable single-longitudinal-mode dual-wavelength operation.
Abstract: A simple linear cavity erbium-doped fiber laser based on a Fabry-Perot filter which consists of a pair of fiber Bragg gratings is proposed for tunable and switchable single-longitudinal-mode dual-wavelength operation. The single-longitudinal-mode is obtained by the saturable absorption of an unpumed erbium-doped fiber together with a narrow-band fiber Bragg grating. Under the high pump power (>166 mW) condition, the stable dual-wavelength oscillation with uniform amplitude can be realized by carefully adjusting the polarization controller in the cavity. Wavelength selection and switching are achieved by tuning the narrow-band fiber Bragg grating in the system. The spacing of the dual-wavelength can be selected at 0.20 nm (approximately 25.62 GHz), 0.22 nm (approximately 28.19 GHz) and 0.54 nm (approximately 69.19 GHz).
TL;DR: By optimizing glass composition and using a multistage dehydration process, a ternary 80TeO(2)-10ZnO-10Na(2)O glass is obtained that shows excellent transparency in the wavelength range from 0.38 microm up to 6.10 microm and on the fabrication of a single-mode solid-core tellurite glass fiber with large mode area and low loss.
Abstract: By optimizing glass composition and using a multistage dehydration process, a ternary 80TeO2-10ZnO-10Na2O glass is obtained that shows excellent transparency in the wavelength range from 0.38 µm up to 6.10 µm. Based on this optimized composition, we report on the fabrication of a single-mode solid-core tellurite glass fiber with large mode area of 103 µm2 and low loss of 0.24~0.7 dB/m at 1550 nm. By using the continuous-wave self-phase modulation method, the non-resonant nonlinear refractive index n2 and the effective nonlinear parameter γ of this made tellurite glass fiber were estimated to be 3.8×10-19 m2/W and 10.6 W-1·km-1 at 1550 nm, respectively.
TL;DR: An efficient and simple approach for converting pulsed near-IR laser radiation into visible and mid-IR light by exploiting degenerate four-wave-mixing in an endlessly single-mode, large-mode-area photonic-crystal fiber is presented.
Abstract: An efficient and simple approach for converting pulsed near-IR laser radiation into visible and mid-IR light by exploiting degenerate four-wave-mixing in an endlessly single-mode, large-mode-area photonic-crystal fiber is presented. Coupling a 1 MHz, 200 ps, 8 W average power pulsed source emitting at 1064 nm into this fiber results in average powers of 3 W at 673 nm signal wavelength and of 450 mW at 2539 nm idler wavelength, respectively. The excellent pulse energy conversion efficiencies of 35% for the signal and 6% for the idler wavelength are due to the unique combination of characteristics of this type of fiber.
TL;DR: A wavelength-swept fiber laser with high speed and wide tuning range, and its application to fiber sensors is reported, based on the dispersion tuning technique, which does not require any optical tunable filter in the laser cavity.
Abstract: We report a wavelength-swept fiber laser with high speed and wide tuning range, and its application to fiber sensors. The laser is based on the dispersion tuning technique, which does not require any optical tunable filter in the laser cavity. By directly modulating the semiconductor amplifier and adjusting the dispersion in the cavity, a wide wavelength tuning range of 178.7 nm and a fast tuning rate of over 200 kHz are obtained. The wavelength-swept laser source is applied to a dynamic fiber Bragg grating sensing system. Dynamic measurement of a 150 Hz sinusoidal strain is demonstrated with a measuring speed as fast as 40 kHz.
TL;DR: To the authors' knowledge, these are the highest output powers generating from active photonic bandgap fibers, as well as from ytterbium-doped fiber lasers at these wavelengths.
Abstract: Ytterbium-doped solid-core photonic bandgap fiber amplifiers operating at the long-wavelength edge of the ytterbium gain band are reported. The low-loss bandgap transmission window is formed in the very low gain region, whilst outside the bandgap, large attenuation inhibits the exponential growth of amplified spontaneous emission in the huge-gain 1030-1100 nm region. Hence parasitic-lasing-free, high-power amplification with a marked efficiency is enabled. A 32 W output at 1156 nm with a 66% slope efficiency and 30 W output at 1178 nm with a 58% slope efficiency were successfully obtained. To our knowledge, these are the highest output powers generating from active photonic bandgap fibers, as well as from ytterbium-doped fiber lasers at these wavelengths.
TL;DR: The fabrication of a monolithic fiber Fabry-Perot interferometer whose cavity is a microscopic air bubble is reported, which exhibited low thermal sensitivity, high mechanical strength, broad operation wavelength range, and fringe contrast in the 8-12 dB range.
Abstract: We report on the fabrication of a monolithic fiber Fabry-Perot interferometer whose cavity is a microscopic air bubble. The latter is formed when splicing together a conventional single-mode fiber and an index-guiding photonic crystal fiber with the standard arc-discharge technique. Spherical microcavities with diameters ranging from 20 to 58 microm were fabricated with such a technique. The interferometers exhibited low thermal sensitivity (less than 1.0 pm/ degrees C), high mechanical strength, broad operation wavelength range, and fringe contrast in the 8-12 dB range. The applications of the interferometers for strain sensing (up to 5000 micro(epsilon) is demonstrated.
TL;DR: This is the first report about a soft glass microstructure fiber which has such a small core together with four rings of holes for the dispersion engineering and it was found that this fiber has a much more flattened chromatic dispersion.
Abstract: We have fabricated a highly nonlinear complex microstructure tellurite fiber with a 1.8 micron core surrounded by four rings of holes. The cane for the fiber was prepared by combining the methods of cast rod in tube and stacking. In the process of fiber-drawing a positive pressure was pumped into the holes of cane to overcome the collapse of holes and reshape the microstructure. The correlations among pump pressure, hole size, surface tension and temperature gradient were investigated. The temperature gradient at the bottom of the preform’s neck region was evaluated quantitatively by an indirect method. The chromatic dispersion of this fiber was compared with that of a step-index air-clad fiber. It was found that this fiber has a much more flattened chromatic dispersion. To the best of our knowledge this is the first report about a soft glass microstructure fiber which has such a small core together with four rings of holes for the dispersion engineering. The SC generation from this fiber was investigated under the pump of a 1557 nm femtosecond fiber laser. Infrared supercontinuum generation, free of fine structure, together with visible third harmonic generation was obtained under the pump of a femtosecond fiber laser with a pulse energy of several hundred pJ.
TL;DR: The physical mechanisms limiting optical fiber resonator length are analyzed and the longest ever laser cavity, reaching 270 km, is reported, which shows a clearly resolvable mode structure with a width of approximately 120 Hz and peak separation of approximately 380 Hz in the radio-frequency spectrum.
Abstract: We analyze the physical mechanisms limiting optical fiber resonator length and report on the longest ever laser cavity, reaching 270 km, which shows a clearly resolvable mode structure with a width of ~120??Hz and peak separation of ~380Hz in the radio-frequency spectrum.
TL;DR: In this paper, the experimental observation of two types of phase-locked vector solitons in weakly birefringent cavity erbium-doped fiber lasers was reported.
Abstract: We report on the experimental observation of two types of phase-locked vector soliton in weakly birefringent cavity erbium-doped fiber lasers. While a phase-locked dark-dark vector soliton was only observed in fiber lasers of positive dispersion, a phase-locked dark-bright vector soliton was obtained in fiber lasers of either positive or negative dispersion. Numerical simulations confirmed the experimental observations and further showed that the observed vector solitons are the two types of phase-locked polarization domain wall solitons theoretically predicted.
Patent•
23 Jun 2009
Abstract: The present wavelength multiplexed optical system includes a multimode optical fiber that transmits wavelength multiplexed optical signals and a plurality of multimode modal dispersion compensation optical fibers. Each modal dispersion compensation optical fiber can transmit one of the multiplex wavelengths, and each modal dispersion compensation optical fiber has an optimized index profile such that the modal dispersion for the transmitted wavelength is approximately inversely equal to the modal dispersion induced in the multimode optical fiber. The wavelength multiplexed optical system facilitates an increased bitrate without reducing bandwidth.
TL;DR: Saturated absorption spectroscopy reveals the narrowest features so far in molecular gas-filled hollow-core photonic crystal fiber, and its wavelength-insensitive transmission is suitable for high-accuracy frequency measurements.
Abstract: Saturated absorption spectroscopy reveals the narrowest features so far in molecular gas-filled hollow-core photonic crystal fiber. The 48-68 μm core diameter of the kagome-structured fiber used here allows for 8 MHz full-width half-maximum sub-Doppler features, and its wavelength-insensitive transmission is suitable for high-accuracy frequency measurements. A fiber laser is locked to the 12C2H2ν1 + ν3 P(13) transition inside kagome fiber, and compared with frequency combs based on both a carbon nanotube fiber laser and a Cr:forsterite laser, each of which are referenced to a GPS-disciplined Rb oscillator. The absolute frequency of the measured line center agrees with those measured in power build-up cavities to within 9.3 kHz (1 σ error), and the fractional frequency instability is less than 1.2 × 10 −11 at 1 s averaging time.
Patent•
04 Feb 2009
TL;DR: In this paper, the optical phase between the individual fiber amplifier elements of the fiber array is measured and controlled using a variety of phase detection and compensation techniques, which can be used for EUV and X-ray generation as well as pumping of parametric amplifiers.
Abstract: High power parallel fiber arrays for the amplification of high peak power pulses are described. Fiber arrays based on individual fiber amplifiers as well as fiber arrays based on multi-core fibers can be implemented. The optical phase between the individual fiber amplifier elements of the fiber array is measured and controlled using a variety of phase detection and compensation techniques. High power fiber array amplifiers can be used for EUV and X-ray generation as well as pumping of parametric amplifiers.
TL;DR: Based on highly Er/Yb codoped phosphate fibers, the authors implemented all-fiber-based narrow-linewidth single-mode (SM) pulsed fiber laser in master oscillator and power amplifier configuration.
Abstract: Based on highly Er/Yb codoped phosphate fibers, we have implemented all-fiber-based narrow-linewidth single-mode (SM) pulsed fiber lasers in master oscillator and power amplifier configuration. Two approaches were used to achieve the narrow-linewidth pulsed fiber laser seeds: 1) an all-fiber-based active Q-switched fiber laser using an actuator and 2) a directly modulated single-frequency continuous-wave fiber laser. Both the fiber laser seed pulses from the two approaches have the transform-limited spectral linewidth. Based on a newly developed large-core SM highly Er/Yb codoped phosphate fiber, the peak power of SM pulses can be scaled to more than 50 kW with transform-limited linewidth and diffraction-limited beam quality. These high-power narrow-linewidth SM fiber laser pulses have been successfully used to generate coherent terahertz (THz) waves based on parametric processes in a nonlinear optical crystal. The peak power of this fiber-based THz source can reach 26.4 mW.
TL;DR: A high power picosecond laser is constructed in an all fiber master oscillator power amplifier (MOPA) configuration and octupled the repetition rate to about 478 MHz though a self-made all fiber device before amplification.
Abstract: A high power picosecond laser is constructed in an all fiber master oscillator power amplifier (MOPA) configuration. The seed source is an ytterbium-doped single mode fiber laser passively mode-locked by a semiconductor saturable absorber mirror (SESAM). It produces 20 mW average power with 13 ps pulse width and 59.8 MHz repetition rate. A direct amplification of this seed source encounters obvious nonlinear effects hence serious spectral broadening at only ten watt power level. To avoid these nonlinear effects, we octupled the repetition rate to about 478 MHz though a self-made all fiber device before amplification. The ultimate output laser exhibits an average power of 96 W, a pulse width of 16 ps, a beam quality M2 of less than 1.5, and an optical conversion efficiency of 61.5%.
TL;DR: In this article, an optical low-coherence interferometry technique has been used to simultaneously resolve the mode profile and to measure the intermodal dispersion of guided modes of a few-mode fiber.
Abstract: An optical low-coherence interferometry technique has been used to simultaneously resolve the mode profile and to measure the intermodal dispersion of guided modes of a few-mode fiber. Measurements are performed using short samples of fiber (about 50 cm). There is no need for a complex mode-conversion technique to reach a high interference visibility. Four LP mode groups of the few-mode fiber are resolved. Experimental results and numerical simulations show that the ellipticity of the fiber core leads to a distinct splitting of the degenerate high-order modes in group index. For the first time, to the best of our knowledge, it has been demonstrated that degenerate LP11 modes are much more sensitive to core shape variations than the fundamental modes and that intermodal dispersion of high-order degenerate modes can be used for characterizing the anisotropy of an optical waveguide.
TL;DR: In this paper, a novel dispersion compensating photonic crystal fiber (DC-PCF) for wide-band high-speed transmission systems is proposed, which can obtain a larger negative dispersion coefficient, better dispersion slope compensation, and confinement losses less than 10 −4 ǫdB/m in the entire S+C+L telecommunication band.
Abstract: This paper reveals a novel dispersion compensating photonic crystal fiber (DC-PCF) for wide-band high-speed transmission systems. The finite-difference method with an anisotropic perfectly matched absorbing layers boundary condition is used to investigate the guiding properties. The designed novel DC-PCF shows that it is possible to obtain a larger negative dispersion coefficient, better dispersion slope compensation, and confinement losses less than 10 −4 dB/m in the entire S+C+L telecommunication band by using a modest number of design parameters. The proposed module can be used in 40 Gb/s dense wavelength division multiplexing (DWDM) systems in optical fiber communication networks.