Showing papers on "Dispersion-shifted fiber published in 2002"
TL;DR: This work demonstrates photonic crystal fibers with ultra-flattened, near zero dispersion with micro-structured fibers showing dispersion of 0 +/- 0.6 ps/nm from 1.24 microm-1.6 microm wavelength.
Abstract: We demonstrate photonic crystal fibers with ultra-flattened, near zero dispersion. Two micro-structured fibers showing dispersion of 0 ± 0.6 ps/nm.km from 1.24 μm-1.44 μm wavelength and 0 ± 1.2 ps/nm.km over 1 μm-1.6 μm wavelength have been measured.
523 citations
TL;DR: The fabrication and properties of soft glass photonic crystal fibers for supercontinuum generation have zero or anomalous group velocity dispersion at wavelengths around 1550 nm, and approximately an order of magnitude higher nonlinearity than attainable in comparable silica fibers.
Abstract: We report the fabrication and properties of soft glass photonic crystal fibers (PCF's) for supercontinuum generation. The fibers have zero or anomalous group velocity dispersion at wavelengths around 1550 nm, and approximately an order of magnitude higher nonlinearity than attainable in comparable silica fibers. We demonstrate the generation of an ultrabroad supercontinuum spanning at least 350 nm to 2200 nm using a 1550 nm ultrafast pump source.
338 citations
TL;DR: An overlay material was deposited by the Langmuir-Blodgett technique onto a single-mode optical fiber containing a long-period grating that exhibits characteristic attenuation bands in its transmission spectrum whose central wavelengths were observed to depend on the optical thickness of the overlay material.
Abstract: An overlay material was deposited by the Langmuir–Blodgett technique onto a single-mode optical fiber containing a long-period grating. The long-period grating exhibits characteristic attenuation bands in its transmission spectrum whose central wavelengths were observed to depend on the optical thickness of the overlay material, even for materials that have a refractive index higher than that of silica.
272 citations
TL;DR: It is shown that the constructive supermodes, each of which has a single output in a different port, build up automatically because of the dense longitudinal-mode, length-unbalanced laser array with unbalanced port loss.
Abstract: Coherent addition of fiber lasers coupled with an intracavity fiber coupler is reported. Almost a single output is obtained from one of the fiber ports, which one can switch simply by unbalancing the losses in the ports. We show that the constructive supermodes, each of which has a single output in a different port, build up automatically because of the dense longitudinal-mode, length-unbalanced laser array with unbalanced port loss. High addition efficiencies of 93.6% for two fiber lasers and 95.6% for four fiber lasers have been obtained.
251 citations
TL;DR: Tests in a controlled environment indicate that the novel concept for an intrinsic relative humidity (RH) sensor that uses polyimide-recoated fiber Bragg gratings has a linear, reversible, and accurate response behavior.
Abstract: A novel concept for an intrinsic relative humidity (RH) sensor that uses polyimide-recoated fiber Bragg gratings is presented. Tests in a controlled environment indicate that the sensor has a linear, reversible, and accurate response behavior at 10-90% RH and at 13-60 degrees C. The RH and temperature sensitivities were measured as a function of coating thickness, and the thermal and hygroscopic expansion coefficients of the polyimide coating were determined.
246 citations
TL;DR: In this article, the authors proposed a new concept to produce switchable multiwavelength oscillations with a cascaded fiber Bragg grating overlapping cavity erbium-doped fiber laser.
Abstract: We propose a new concept to produce switchable multiwavelength oscillations with a cascaded fiber Bragg grating overlapping cavity erbium-doped fiber laser. The laser can be designed to operate in multiwavelength or in wavelength switching modes. The different lines have different thresholds. For three-wavelength oscillation, the output powers are linear or piecewise linear functions of the input pump power. An output with a variation of only 1.5 dB has been achieved with an input pump power of 100 mW. For wavelength switching, three single-wavelength and two dual-wavelength operation regions have been obtained toy adjusting the input pump levels.
197 citations
TL;DR: The guidance of dry micron-sized dielectric particles in hollow core photonic crystal fiber using an Argon ion laser beam operating at a wavelength of 514 nm is reported.
Abstract: We report the guidance of dry micron-sized dielectric particles in hollow core photonic crystal fiber The particles were levitated in air and then coupled to the air-core of the fiber using an Argon ion laser beam operating at a wavelength of 514 nm The diameter of the hollow core of the fiber is 20 m A laser power of 80 mW was sufficient to levitate a 5 m diameter polystyrene sphere and guide it through a ~150 mm long hollow-core crystal photonic fiber The speed of the guided particle was measured to be around 1 cm/s
173 citations
TL;DR: In this paper, a swept-wavelength source is created by connecting four elements in series: a femtosecond fiber laser at 1.56 μm, a nonlinear fiber, a dispersive fiber and a tunable spectral bandpass filter.
Abstract: A swept-wavelength source is created by connecting four elements in series: a femtosecond fiber laser at 1.56 μm, a non-linear fiber, a dispersive fiber and a tunable spectral bandpass filter. The 1.56-μm pulses are converted to super-continuum (1.1–2.2 μm) pulses by the non-linear fiber, and these broadband pulses are stretched and arranged into wavelength scans by the dispersive fiber. The tunable bandpass filter is used to select a portion of the super-continuum as a scan-wavelength output. A variety of scan characteristics are possible using this approach. As an example, an output with an effective linewidth of approximately 1 cm-1 is scanned from 1350–1550 nm every 20 ns. Compared to previous scanning benchmarks of approximately 1 nm/μs, such broad, rapid scans offer new capabilities: a gas sensing application is demonstrated by monitoring absorption bands of H2O, CO2, C2H2 and C2H6O at a pressure of 10 bar.
164 citations
TL;DR: A high-power double-clad Tm-doped silica fiber laser, pumped by two beam-shaped and polarization-coupled diode bars at 787 nm, was wavelength tuned by use of an external cavity containing a diffraction grating.
Abstract: A high-power double-clad Tm-doped silica fiber laser, pumped by two beam-shaped and polarization-coupled diode bars at 787 nm, was wavelength tuned by use of an external cavity containing a diffraction grating. The Tm fiber laser produced a maximum output power of 7 W at 1940 nm for 40 W of incident diode power and was tuned over a wavelength range of 230 nm from 1860 to 2090 nm, with >5-W output power over the range 1870-2040 nm. The prospects for further improvement in performance and extension of the tuning range are discussed.
159 citations
TL;DR: In this paper, the authors demonstrated near-complete wavelength exchange between two signals at 1573.4 and 1579.9 nm with two 0.25-W pumps in a 1-km-long highly nonlinear dispersion-shifted fiber.
Abstract: With a suitable arrangement of two pumps and two signals with respect to the zero-dispersion wavelength of a fiber, simultaneous wavelength exchange between two signals can be realized by four-wave mixing in the fiber. We have demonstrated near-complete wavelength exchange between two signals at 1573.4 and 1579.9 nm with two 0.25-W pumps in a 1-km-long highly nonlinear dispersion-shifted fiber. We also have evaluated the bit-error-rate performance of wavelength exchange with a 10-Gb/s signal, and obtained a power penalty of less than 1 dB for the exchanged signal.
154 citations
TL;DR: In this article, the authors demonstrate optical parametric oscillation based on four-wave mixing in microstructure fiber, which is the first time to the best of our knowledge that such an approach has been used.
Abstract: We demonstrate, for the first time to our knowledge, optical parametric oscillation based on four-wave mixing in microstructure fiber. The measured wavelength-tunability range of the device (40 nm) and the threshold-pump peak power (34.4 W) are in good agreement with the theory of four-wave mixing in optical fibers. The ellipticity of the fiber's polarization modes allows the device to be implemented in a relatively simple Fabry-Perot configuration. Spectral peaks that are due to cascaded-mixing processes are easily observed in our setup, which may provide a way to extend the tunability range of existing high-power lasers.
TL;DR: In this paper, a Holey fiber with very complex hole geometry is studied by means of a numerical simulator for modal analysis based on the finite element method (FEM) and the results show a good agreement with experimental ones reported in literature.
Abstract: A holey fiber (HF), having very complex hole geometry, is studied by means of a numerical simulator for modal analysis based on the finite-element method (FEM). Polarization and dispersion properties as well as the full vector field distribution of the fundamental mode are investigated. The obtained numerical results show a good agreement with experimental ones reported in literature.
TL;DR: In this article, the authors measured the loss-per-pass and the ring-down time of the light pulses in the fiber and splice connector and showed that light pulses traveling through the fiber-loop are detected using a photomultiplier detector.
Abstract: Pulsed, visible and near-infrared laser light is coupled into an optical fiber, which is wound into a loop using a fiber splice connector. The light pulses traveling through the fiber-loop are detected using a photomultiplier detector. It is found that once the light is coupled into the fiber it experiences very little loss and the light pulses do a large number of round trips before their intensity is below the detection threshold. Measurements of the loss-per-pass and of the ring-down time allow for characterization of the different loss mechanisms of the light pulses in the fiber and splice connector. This method resembles “cavity ring-down absorption spectroscopy” and is well suited to characterize low-loss processes in fiber optic transmission independent from power fluctuations of the light source. It is demonstrated that by measuring the ring-down times one can accurately determine the absolute transmission of an optical fiber and of the fiber connector. In addition it is demonstrated that the tech...
TL;DR: Fiber couplers made with photonic crystal fibers (PCF) are reported and, with a fiber that had five hexagonally stacked layers of air holes, a 33/67 coupling ratio was obtained, and with a one-layer four-hole fiber, a 48/52 coupling ratios were obtained.
Abstract: Fiber couplers made with photonic crystal fibers (PCF) are reported. Two types of PCF were fabricated by means of stacking a group of silica tubes around a silica rod and drawing them. The fiber couplers were made by use of the fused biconical tapered method. With a fiber that had five hexagonally stacked layers of air holes, a 33/67 coupling ratio was obtained, and with a one-layer four-hole fiber, a 48/52 coupling ratio was obtained. The fabrication processes and the characteristics of the PCFs and the PCF couplers are presented.
TL;DR: A multimode, double-clad, Yb-doped fiber amplifier that produces diffraction-limited, 0.8-ns pulses with energies of 255 muJ and peak powers in excess of 300 kW at a repetition rate of ~8 kHz is reported.
Abstract: We report a multimode, double-clad, Yb-doped fiber amplifier that produces diffraction-limited, 0.8-ns pulses with energies of 255 muJ and peak powers in excess of 300 kW at a repetition rate of ~8 kHz . Single-transverse-mode operation was obtained by bend-loss-induced mode filtering of the gain fiber.
TL;DR: Efficient repetitive passive Q switching of a cladding-pumped Er-Yb fiber laser has been demonstrated by use of an external-cavity configuration containing a Co(2+): ZnS crystal as a saturable absorber.
Abstract: Highly-efficient repetitive passive Q-switching of a cladding-pumped Er-Yb fiber laser has been demonstrated by employing an external cavity configuration containing a Co2+:ZnS crystal as saturable absorber. Energies up to 60µJ in pulses of duration as short as 3.5ns (FWHM), corresponding to a peak power >10kW, have been generated, and the maximum slope efficiency with respect to absorbed pump power was 13%. Using a bulk diffraction grating in Littrow configuration to provide wavelength selective feedback, the passively Q-switched fiber laser was tuned over 31nm from 1532nm to 1563nm. The prospects for further improvement in performance will be discussed.
TL;DR: It is experimentally demonstrate that a short length of highly nonlinear holey fiber (HF) can be used for strong L(+) -band (1610-1640-nm) Raman amplification and ultrafast signal modulation.
Abstract: We experimentally demonstrate that a short length of highly nonlinear holey fiber (HF) can be used for strong L+-band (1610–1640-nm) Raman amplification and ultrafast signal modulation. We use a pure silica HF with an effective area of just 2.85 µm2 at 1550 nm, which yields an effective nonlinearity ∼15 times higher than in conventional silica dispersion-shifted fiber. Using a 75-m length of this fiber, we obtained internal Raman gains of more than 42 dB and a noise figure of ∼6 dB under a forward single-pump scheme, and the Raman gain coefficient was experimentally estimated to be 7.6×10-14 m/W. Also, an 11-dB signal extinction ratio in a Raman-induced all-optical modulation experiment was achieved with the same fiber.
TL;DR: The thermo-optic coefficient of the core material of a fiber is analyzed by use of a pair of long-period fiber gratings and is calculated by repetition of the measurement at different temperatures.
Abstract: The thermo-optic coefficient of the core material of a fiber is analyzed by use of a pair of long-period fiber gratings. First the effective index difference between the core and the cladding modes is measured from the peaks of the interference fringe generated by the grating pair. The order of the cladding mode is decided by the cutoff wavelength and the numerical aperture of the fiber. The material index of the fiber core is obtained in terms of wavelength. At each wavelength the index is chosen to minimize the difference between the measured and the calculated spectra of the grating pair. Finally the thermo-optic coefficient of the fiber core is calculated by repetition of the measurement at different temperatures. With a germanosilicate-core fiber and a boron codoped germanosilicate-core fiber, the thermo-optic coefficients were 1.1x10(-5)/( degrees )C and 0.75x10(-5)/( degrees )C, respectively.
TL;DR: The results highlight the compatibility of the rapidly developing holey fiber technology with short pulse Ytterbium (Yb)-doped fiber lasers for wide application.
Abstract: We report linear dispersion compensation, soliton pulse formation, soliton compression, and ultra-broad supercontinuum generation in a holey fiber with anomalous dispersion at wavelengths above 800nm. The holey fiber was seeded with ultrashort pulses from a diode pumped, Ytterbium (Yb)-doped fiber source operating at 1.06 μm. The results highlight the compatibility of the rapidly developing holey fiber technology with short pulse Yb-doped fiber lasers for wide application.
TL;DR: In this paper, the authors reported continuous-wave operation of singly resonant fiber optical parametric oscillators in a cavity formed by 100 m of highly nonlinear fiber and two fiber Bragg gratings, the pump power threshold was 240 mW; the output wavelength could be tuned over 80 nm by tuning the pump.
Abstract: We report continuous-wave operation of singly resonant fiber optical parametric oscillators. In a cavity formed by 100 m of highly nonlinear fiber and two fiber Bragg gratings, the pump power threshold was 240 mW; the output wavelength could be tuned over 80 nm by tuning of the pump. We also obtained an internal conversion efficiency of 30%, compared with the maximum theoretical value of 50%, by use of a 1-km-long cavity.
TL;DR: A method for introducing and dynamically tuning birefringence in a microstructured optical fiber that corresponds to a phase change of 6pi for a 1-cm length of fiber is demonstrated.
Abstract: We demonstrate a method for introducing and dynamically tuning birefringence in a microstructured optical fiber. Waveguide asymmetry in the fiber is obtained by selective filling of air holes with polymer, and tunability is achieved by temperature tuning of the polymer’s index. The fiber is tapered such that the mode field expands into the cladding and efficiently overlaps the polymer that has been infused into the air holes, ensuring enhanced tunability and low splice loss. Experimental results are compared with numerical simulations made with the beam propagation method and confirm birefringence tuning that corresponds to a phase change of 6π for a 1-cm length of fiber.
TL;DR: In this paper, a new scheme for simultaneous measurement of temperature and strain using fiber Bragg grating (FBG) and a thermochromic material is presented, which consists of a dual system with two different sensing elements included in the same fiber.
Abstract: A new scheme for simultaneous measurement of temperature and strain using fiber Bragg grating (FBG) and a thermochromic material is presented. It consists of a dual system with two different sensing elements included in the same fiber: a fiber Bragg grating to measure the strain and a thermochromic effect based optical fiber sensor to measure the temperature variations and to compensate the cross sensitivity of the fiber Bragg grating with temperature. Experimental results of the optical dual system are shown and discussed.
TL;DR: In this article, a fiber OPA with peak signal gain of 9 /spl plusmn/ 0.2 dB when the signal polarization angle was varied from 0/spl deg/ to 90 /spl deg/. Power penalty of less than 1 dB was measured in a 10Gb/s transmission system.
Abstract: One-pump fiber optical parametric amplifiers (OPAs) can be rendered polarization independent by using a polarization-diversity technique. We have experimentally demonstrated a fiber OPA with peak signal gain of 9 /spl plusmn/ 0.2 dB when the signal polarization angle was varied from 0/spl deg/ to 90/spl deg/. Power penalty of less than 1 dB was measured in a 10-Gb/s transmission system.
TL;DR: In this paper, the authors proposed and demonstrated a simple and novel technique to get multi-wavelength operation in the L-band by using an elliptical core erbium-doped fiber.
Abstract: In this letter, we propose and demonstrate a simple and novel technique to get multiwavelength operation in the L-band by using an elliptical core erbium-doped fiber. The principle of operation is based on the anisotropic gain effect in a polarization-maintaining fiber. Stable multiwavelength operation is achieved at room temperatures. The lasing lines may be controlled by a polarization controller.
TL;DR: In this article, the authors demonstrate all-optical switching of picosecond pulses between the output ports of a microstructure-fiber-based polarization Sagnac interferometer.
Abstract: In this letter, we demonstrate all-optical switching of picosecond pulses between the output ports of a microstructure-fiber-based polarization Sagnac interferometer. High contrast switching of 2.6-ps FWHM signal pulses due to cross-phase modulation induced by 4.9-ps pump pulses in a 5.8-m long microstructure fiber is achieved at wavelengths near 1550 and 780 nm. The spectral and temporal behavior of the switching device are investigated and compared with numerical simulations based on coupled-wave theory.
TL;DR: In this article, the authors demonstrate a high performance fused-type mode selective coupler that couples the LP/sub 11/mode in one fiber and the L 1/sub 01/ mode in another using highly elliptical core two-mode fibers.
Abstract: In this letter, we demonstrate a high performance fused-type mode selective coupler that couples the LP/sub 11/ mode in one fiber and the LP/sub 01/ mode in another using highly elliptical core two-mode fibers. The phase-matching condition was achieved by etching and prepulling portions of two-mode fibers. The coupling efficiency and the mode extinction ratio of 56% to 80% and 22-32 dB, respectively, were achieved with high temperature stability over 1515- to 1595-nm wavelength range.
Proceedings Article•
01 Jan 2002
TL;DR: A process of nonlinear generation of very high-order UV modes by pumping cobweb microstructured optical fibers with 100 fs Ti:sapphire pulses through a mechanism distinct from supercontinuum generation is described.
Abstract: We report generation of high-order spatial modes in the UV range through nonlinear frequency conversion of the femtosecond 800 nm radiation in microstructured fibers. The process is distinct from Supercontinuum generation and is sensitive to fiber tip morphology. One of the manifestations of the unusual nonlinear properties of the microstructured (PCF) fibers is the robust supercontinuum generation from a few centimeters of the fiber with femtosecond oscillator pumping around 800 nm. Even though the fiber can be multimode at wavelengths down to the fundamental, supercontinuum is usually observed exiting the fiber in the fundamental mode. Recent experiments, however, evidenced the existence of other nonlinear effects in PCFs indicating critical role of phase matching between various spatial modes of the fiber. When the PCF is pumped by the 1550 nm femtosecond pulses, distinct visible bands are generated at the output belonging to distinct spatial modes of the fiber. Here we report that similar nonlinear mechanism exists when PCF is pumped by Ti:Sapphire femtosecond oscillator near 800 nm central wavelength. In this case, however, higher-order modes are generated in the UV range with observed wavelengths up to 310 nm, Fig. 1. Moreover, the effect is observed only when the input tip ofmore » the fiber has a non-flat surface, that is freshly cleaved fiber is prepared by melting the tip as described. The experiment consists of a femtosecond oscillator delivering 150-fs pulses with average power of up to 1.3 W to the fiber tip. After the attenuator, Faraday isolator and polarization control optics, the light is focused on the tip of the PCF with an aspheric lens. The fiber was a high-air-filling fraction single strand fused silica suspended by a honeycomb web of silica pellicles running along the length of the fiber, which was a few tens of centimeters in our experiments. The diameter of the core was approximately 2.5 microns which makes the fiber highly multimode at 800 nm. At low pump powers coupled to the freshly cleaved fiber typical supercontinuum is observed at the output. When the input power is increased further a threshold is reached at near 1.1W when the supercontinuum generation suddenly ceases. This was later identified as the melting of the fiber tip by SEM analysis and transverse guiding scans, shown in Fig. 3. Generation of the UV modes is observed after the fiber tip melt at various input power levels but was found to be very sensitive to the input polarization of the fundamental. Two images of the output UV mode profiles are shown in Fig. 2. These findings strongly suggest that launching the fundamental light into a higher-order spatial mode was critical for the process. The aforementioned threshold corresponds to the melting of the fiber tip after which the tip is no longer flat but rather works as a phase mask for the coupling of the input light. Such a mask decreases the efficiency of the fundamental mode excitation leading to the disappearance of the supercontinuum and increases the efficiency of higher-mode excitation which results in the UV generation through phase matching to even higher-order modes.« less
Patent•
01 Nov 2002
TL;DR: In this paper, a distribution optical fiber sensor system was proposed to measure distortion and temperature of a structure with a high spatial resolution, where a light source emits a first pulse light having a pulse width longer than a transient response of an acoustic phonon and a second pulse light after a time interval during which vibration of the acoustic phonons is maintained thereby supplying the pulse lights to the optical fiber.
Abstract: A distribution optical fiber sensor system measures distortion and temperature of a structure with a high spatial resolution. The system has an optical fiber on an object to be measured. A light source emits a first pulse light having a pulse width longer than a transient response of an acoustic phonon and a second pulse light after a time interval during which vibration of the acoustic phonon is maintained thereby supplying the pulse lights to the optical fiber. A detector detects scattering gain spectra of a Brillouin-scattered light created in the optical fiber by the second pulse light at intervals corresponding to twice the time obtained by equally dividing the pulse width of the second pulse light. A controlling/calculating unit calculates distortion and/or temperature based on the scattering gain spectra for sections of the optical fiber corresponding to the scattering gain spectra at the respective time intervals.
TL;DR: The first gain and noise-figure measurements of a fiber optical parametric amplifier pumped by a simple frequency-modulated source are presented and the maximum gain and average noise figure are presented.
Abstract: We present what are to our knowledge the first gain and noise-figure measurements of a fiber optical parametric amplifier pumped by a simple frequency-modulated source. The maximum gain was 27.2 dB and the average noise figure was 4.2 dB. We achieved the low noise figure by filtering the pump to remove the broadband amplified spontaneous-emission pedestal on the pump spectrum.
TL;DR: This work reports on the development of what it considers to be a practical and highly stable stretched-pulse laser based on Yb(3+) -doped silica fiber, which uses nonlinear polarization rotation as the mode-locking mechanism, and a semiconductor saturable-absorber mirror to ensure robust self-starting.
Abstract: We report on the development of what we consider to be a practical and highly stable stretched-pulse laser based on Yb3+-doped silica fiber. The Fabry–Perot cavity uses nonlinear polarization rotation as the mode-locking mechanism, and a semiconductor saturable-absorber mirror to ensure robust self-starting and incorporates a diffraction grating pair to compensate for the normal dispersion of the fiber. Use of a single-mode grating-stabilized telecommunications-qualified pump laser diode ensures reliable, low-noise operation (∼0.05% amplitude fluctuations at 10-Hz measurement bandwidth). The laser generates high-quality, 60-pJ pulses of <110‐fs duration at a repetition rate of ∼54 MHz (3-mW average power).