Showing papers on "Single-mode optical fiber published in 2002"
TL;DR: In this paper, an out-of-plane coupler for butt-coupling from fiber to compact planar waveguides is proposed based on a short second-order grating or photonic crystal, etched in a waveguide with a low-index oxide cladding.
Abstract: We have designed and fabricated an out-of-plane coupler for butt-coupling from fiber to compact planar waveguides. The coupler is based on a short second-order grating or photonic crystal, etched in a waveguide with a low-index oxide cladding. The coupler is optimized using mode expansion-based simulations. Simulations using a 2-D model show that up to 74% coupling efficiency between single-mode fiber and a 240-nm-thick GaAs-AlO/sub x/ waveguide is possible. We have measured 19% coupling efficiency on test structures.
687 citations
TL;DR: In this paper, the authors describe the numerical verifications of a multipole formulation for calculating the electromagnetic properties of the modes that propagate in microstructured optical fibers and illustrate the application of this formulation to calculating both the real and the imaginary parts of the propagation constant.
Abstract: We describe the numerical verifications of a multipole formulation for calculating the electromagnetic properties of the modes that propagate in microstructured optical fibers. We illustrate the application of this formulation to calculating both the real and the imaginary parts of the propagation constant. We compare its predictions with the results of recent measurements of a low-loss microstructured fiber and investigate the variations in fiber dispersion with geometrical parameters. We also show that the formulation obeys appropriate symmetry rules and that these rules may be used to improve computational speed.
245 citations
TL;DR: The nature of modal cutoff in microstructured optical fibers of finite cross section is analyzed and the parameter subspace in which the fibers are single mode and an accurate value for the limit of the endlessly single-mode regime is established.
Abstract: We analyze the nature of modal cutoff in microstructured optical fibers of finite cross section In doing so, we reconcile the striking endlessly single-mode behavior with the fact that in such fibers all propagation constants are complex We show that the second mode undergoes a strong change of behavior that is reflected in the losses, effective area, and multipolar structure We establish the parameter subspace in which the fibers are single mode and an accurate value for the limit of the endlessly single-mode regime
192 citations
TL;DR: It is shown that the bandwidths of such mode converters can be tailored by suitably altering the design of the few-mode fibers, and the demonstration of strong mode conversion (>99%) with long-period fiber gratings over what is believed to be a record bandwidth of 63 nm.
Abstract: Control of the group-velocity differences between two distinct modes in a few-mode fiber can be used to define the spectral characteristics of long-period gratings written in them. Using this effect, we report the demonstration of strong mode conversion (>99%) with long-period fiber gratings over what is believed to be a record bandwidth of 63 nm. These novel spectra are obtained from gratings written in specially designed few-mode fibers in which the grating phase-matching condition is satisfied over a large spectral range. We show that the bandwidths of such mode converters can be tailored by suitably altering the design of the few-mode fibers. The polarization-dependent coupling for the mode converters varies by less than 0.004% over the entire spectrum.
173 citations
TL;DR: In this paper, a single-mode CW power of 7.1 mW has been achieved from an 8/spl mu/m diameter reflecting optical waveguide (ARROW) device with a far-field FWHM of 10/spl deg/
Abstract: Antiresonant reflecting optical waveguide (ARROW) techniques are employed in vertical cavity surface emitting lasers (VCSELs) to achieve high-power single-mode emission. Using the effective-index method and fiber mode approximation, the cold-cavity lateral modal behavior for the circular shaped ARROW VCSEL demonstrates significant reduction of radiation loss from that of a single antiguide, while maintaining strong discrimination against high-order modes. The circular-waveguide is created by selective chemical etching and two-step metal-organic chemical vapor deposition growth, with proton implantation used to confine the current injection to the low-index core region. A single-mode CW power of 7.1 mW has been achieved from an 8 /spl mu/m diameter ARROW device (index step /spl Delta/n = 0.05, emission at /spl lambda//sub 0/ = 980 nm) with a far-field FWHM of 10/spl deg/. Larger aperture (12 /spl mu/m) devices exhibit multimode operation at lower drive currents with a maximum single-mode continuous-wave output power of 4.3 mW.
147 citations
TL;DR: A novel shape-adjustable narrowband optical filter utilizing stimulated Brillouin scattering in an optical fiber is proposed and demonstrated and a tunable optical notch filter is also realized by deamplification of the anti-Stokes wave.
Abstract: A novel shape-adjustable narrowband optical filter utilizing stimulated Brillouin scattering in an optical fiber is proposed and demonstrated. In this scheme, binary-phase-shift-keying modulation is applied to the pump wave to broaden and shape the Brillouin gain spectrum. By choosing an appropriate modulation data pattern, we realized a flat-top steep-cutoff optical bandpass filter with a 3-dB bandwidth of 1.5 GHz and a 10-dB bandwidth of 2 GHz is realized. In addition, a tunable optical notch filter is also realized by deamplification of the anti-Stokes wave.
145 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.
144 citations
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.
142 citations
TL;DR: It is established that Microstructured Optical Fibers have a fundamental mode cutoff, marking the transition between modal confinement and non-confinement, and insight into the nature of this transition is given through two asymptotic models that provide a mapping to conventional fibers.
Abstract: We establish that Microstructured Optical Fibers (MOFs) have a fundamental mode cutoff, marking the transition between modal confinement and non-confinement, and give insight into the nature of this transition through two asymptotic models that provide a mapping to conventional fibers. A small parameter space region where neither of these asymptotic models holds exists for the fundamental mode but not for the second mode; we show that designs exploiting unique MOF characteristics tend to concentrate in this preferred region.
114 citations
TL;DR: The results open the door to studies of the optical and electro-optical properties of photopolymerized guides doped by nonlinear optical chromophores and to possible applications in integrated optical devices.
Abstract: We investigated the condition of unique self-written channel and multichannel propagation inside bulk photopolymerizable materials. Light was introduced in the medium by a single-mode optical fiber. At a very low beam power of 5 µW, a unique uniform-channel waveguide without any broadening was obtained by polymerization. When the input power is increased to 100 µW, the guide becomes chaotic and multichannel. We connected two fibers separated by a 1-cm distance. The results open the door to studies of the optical and electro-optical properties of photopolymerized guides doped by nonlinear optical chromophores and to possible applications in integrated optical devices.
110 citations
TL;DR: In this article, a comprehensive theoretical investigation of the influence of instantaneous mode-competition phenomena on the dynamics of semiconductor laser systems is presented, based on numerical simulations of the multimode rate equations superposed by Langevin noise sources that account for the intrinsic fluctuations associated with the spontaneous emission.
Abstract: Comprehensive theoretical investigations of the influence of instantaneous mode-competition phenomena on the dynamics of semiconductor lasers are introduced. The analyzes are based on numerical simulations of the multimode rate equations superposed by Langevin noise sources that account for the intrinsic fluctuations associated with the spontaneous emission. Numerical generation of the Langevin noise sources is performed in such a way as to keep the correlation of the modal photon number with the injected electron number. The gain saturation effects, which cause competition phenomena among lasing modes, are introduced based on a self-consistent model. The effect of the noise sources on the mode-competition phenomena is illustrated. The mode-competition phenomena induce instantaneous coupling among fluctuations in the intensity of modes, which induce instabilities in the mode dynamics and affect the state of operation. The dynamics of modes and the characteristics of the output spectrum are investigated over wide ranges of the injection current and the linewidth enhancement factor in both AlGaAs-GaAs and InGaAsP-InP laser systems. Operation is classified into stable single mode, stable multimode, hopping multimode, and jittering single mode. Based on the present results, the experimental observations of multimode oscillation in InGaAsP-InP lasers are explained as results of the large value of the linewidth enhancement factor.
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: 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 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: The experiments illustrate the application of a dynamical encoding and information recovery scheme that is robust to perturbations of the communication channel, a standard single mode fiber.
Abstract: The fast, irregular, fluctuations of the state of polarization of light output from an erbium doper fiber ring laser are used to communicate digital information. The experiments illustrate the application of a dynamical encoding and information recovery scheme that is robust to perturbations of the communication channel, a standard single mode fiber. A fiber-optic polarization analyzer was used to measure and visualize the polarization dynamics at nanosecond time scales on the Poincare sphere.
TL;DR: In this article, a new optical modulation format chirp-free return-to-zero differential phase shift keying (CF-RZ-DPSK) is presented, which enables WDM transmission at 10 Gb/s/ch at a channel spacing of 100 GHz over 3000 km without significant impairments due to cross-phase modulation (XPM).
Abstract: We present a new optical modulation format chirp-free return-to-zero differential phase shift keying (CF-RZ-DPSK), which enables wavelength-division-multiplexing (WDM) transmission at 10 Gb/s/ch at a channel spacing of 100 GHz over 3000 km without significant impairments due to cross-phase modulation (XPM). A transmitter setup is presented, which allows a simple implementation of CF-RZ-DPSK with two Mach-Zehnder modulators in push-pull operation. The robustness toward XPM is shown theoretically with the help of a simple analytical model for the XPM-induced phase modulation. The superior performance of CF-RZ-DPSK over other modulation formats [RZ-ampfitude shift keying (ASK), nonreturn-to-zero (NRZ)-DPSK, and NRZ-ASK, respectively] is clarified. Finally, simulation results for CF-RZ-DPSK in comparison to RZ-ASK show the superior performance of the newly proposed modulation format in a dense WDM setup.
TL;DR: In this paper, the authors developed a dynamical model suitable for the description of two mutually coupled semiconductor lasers in a face-to-face configuration, considering the propagation of the electric field along the compound system as well as the evolution of the carrier densities within each semiconductor laser.
Abstract: We develop a dynamical model suitable for the description of two mutually coupled semiconductor lasers in a face-to-face configuration. Our study considers the propagation of the electric field along the compound system as well as the evolution of the carrier densities within each semiconductor laser. Mutual injection, passive optical feedback, and multiple reflections are accounted for in this framework, although under weak to moderate coupling conditions. We systematically describe the effect of the coupling strength on the spectrum of monochromatic solutions and on the respective dynamical behavior. By assuming single-longitudinal-mode operation, weak mutual coupling and slowly varying approximation, the dynamical model can be reduced to rate equations describing the mutual injection from one laser to its counterpart and vice versa. A good agreement between the complete and simplified models is found for small coupling. For larger coupling, higher-order terms lead to a smaller threshold reduction, reflected itself in the spectrum of the monochromatic solutions and in the dynamics of the optical power.
TL;DR: In this paper, a dual asymmetric core dispersion compensating optical fiber (DCF) is proposed to control or compensate the chromatic dispersion of optical links, where the dispersion coefficient was measured to be ǫ−1800 ps/(nm·km) in the 1.55-μm low-loss window.
Patent•
06 Dec 2002TL;DR: In this article, the subject invention relates to a method and apparatus for spatial domain modulation in optical wavelengths, which can be used with single mode and multi-mode waveguide structures, for example, single modes and multi modes optical fibers.
Abstract: The subject invention pertains to a method and apparatus for multiplexing in optical fiber communications. The subject invention relates to a method and apparatus for spatial domain modulation in optical wavelengths. In a specific embodiment, the subject invention relates to a spatial domain multiplexer (SDM) for use with an optical fiber. Preferably, the input channels coupled into the fiber optic cable include collimated laser beams. The techniques of the subject invention can be utilized with single mode and multi mode waveguide structures, for example, single mode and multi mode optical fibers. The subject invention is applicable to step index optical fiber and to graded index optical fiber. Applications of the subject technology can include secure data links, for example, which can modulate data such that if the data is intercepted, the data cannot be interpreted. The subject methods and apparatus can also be used in conjunction with other multiplexing techniques such as time-domain multiplexing.
TL;DR: In this article, a more comprehensive model of excitation and propagation of acoustic vibrations, electrostrictively induced in optical fibres by laser pulses, is presented, and an analytic expression for the acoustic response function of the refractive index in a standard single-mode fiber is derived.
Abstract: A revised, more comprehensive model of excitation and propagation of acoustic vibrations, electrostrictively induced in optical fibres by laser pulses, is presented. An analytic expression for the acoustic response function of the refractive index in a standard single-mode fibre is derived. Response functions are found for a standard fibre as well as for a single-mode double-clad fibre, which offers much promise for fibreoptic communication lines and where the effective area of mode-field cross section is increased with respect to a standard fibre. It is shown that the intensity of excited sound waves in double-clad fibres is usually several times higher than that in standard fibres. This intensity is determined mainly by the shape of the radial distribution of the electromagnetic field in the pulse, which is different for the fibres considered in this paper.
TL;DR: It is shown that for short fiber lengths (approximately 2 m) two-photon excitation efficiency at the fiber output can be substantially improved by single-mode propagation in a large-area multimode fiber instead of a standard 5.5-microm core fiber.
Abstract: Multiphoton excitation through optical fibers is limited by pulse broadening caused by self-phase modulation. We show that for short fiber lengths (approximately 2 m) two-photon excitation efficiency at the fiber output can be substantially improved by single-mode propagation in a large-area multimode fiber (10-µm core diameter) instead of a standard 5.5-µm core fiber. Measurements and numerical simulations of postfiber spectra and pulse widths demonstrate that the increase in efficiency is due to a reduction of nonlinear pulse broadening. Single-mode propagation in a large-core fiber is thus suitable for multiphoton applications for which pulse recompression is not possible at the fiber end.
TL;DR: In this article, the change in the chromatic dispersion of optical fiber with temperature is studied for 40-Gb/s systems and an equation for the change with a temperature is derived.
Abstract: The change in the chromatic dispersion of optical fiber with temperature is an important design parameter for 40-Gb/s systems. We derive an equation for the change in dispersion with a temperature that is more general than what has previously been published. We present experimental results for the change in fiber dispersion with temperature for six commercially available fiber types of interest for 40-Gb/s communication systems. In addition, we demonstrate that the empirical model developed by Ghosh et al in 1994 for the temperature-dependent index of refraction of SiO/sub 2/ can be used to accurately model the temperature dependence of the chromatic dispersion of a wide variety of optical fibers.
TL;DR: An atomic force microscope for nanocantilevers measuring from a few 100 nm to a few μm in length was implemented in this article, where the probe beam of the Doppler interferometer was guided to the nano-vertex by a single mode polarization-maintaining optical fiber terminated by a collimating lens, a quarter wave plate, and a focusing lens.
Abstract: An atomic force microscope for nanocantilevers measuring from a few 100 nm to a few μm in length was implemented. The natural frequencies of the nanocantilevers lie in the range of 1 MHz to 1 GHz, and optical detection schemes adapted to their size and frequency range was selected. A helium neon laser with a beat frequency of 890 MHz was used as the laser source. The beat was shifted to 1090 MHz by an acousto-optical-modulator, and used as the carrier for heterodyne laser Doppler measurement. This enabled velocity measurement up to around 100 MHz. The probe beam of the Doppler interferometer was guided to the nanocantilever by a single mode polarization-maintaining optical fiber terminated by a collimating lens, a quarter wave plate, and a focusing lens. Reflected light was collected by the same optics and mixed with the reference beam. Self-excitation of the nanocantilever at its lowest natural frequency was implemented for an amplitude of 1 nmp-p at 36 MHz. The Q factor of the cantilever was 8000. Noise...
TL;DR: In this article, an electric arc-induced long-period fiber gratings with low insertion loss (<0.2 dB) and high isolation peaks (−24 dB) have been fabricated in standard singlemode fiber (Corning SMF28).
24 May 2002
TL;DR: In this paper, a 135 W CW ytterbium doped fiber laser has been demonstrated with measured M/sup 2/ < 1.05 and the stimulated Raman scattering imposed the major limit on the output power.
Abstract: Reliable 135 W CW ytterbium doped fiber laser has been demonstrated with measured M/sup 2/ < 1.05. The stimulated Raman scattering imposed the major limit on the output power. No thermal distortions or damage of the fiber core was observed.
TL;DR: Numerical simulations are performed to obtain statistical and spectral characteristics of stimulated Brillouin scattering initiated by Gaussian noise in single-mode optical fibers and reveal how the probability function of Stokes power, the power-correlation function, and the SBS spectra evolve as key parameters of the model vary, leading to a modification of Stoke field statistics.
Abstract: We performed numerical simulations to obtain statistical and spectral characteristics of stimulated Brillouin scattering (SBS) initiated by Gaussian noise in single-mode optical fibers. Recently published experimental spectra of SBS power [e.g., Phys. Rev. Lett.85, 1879 (2000)] are explained completely by a one-dimensional SBS model. We give a clear physical insight into the problem and, for what is to our knowledge the first time, reveal how the probability function of Stokes power, the power-correlation function, and the SBS spectra evolve as key parameters of the model vary, leading to a modification of Stokes field statistics.
TL;DR: An all-optical neural network is presented that is based on coupled lasers that is particularly robust against input wavelength variations and the winner take all (WTA) neural-network behavior of a system of many lasers.
Abstract: An all-optical neural network is presented that is based on coupled lasers. Each laser in the network lases at a distinct wavelength, representing one neuron. The network status is determined by the wavelength of the network's light output. Inputs to the network are in the optical power domain. The nonlinear threshold function required for neural-network operation is achieved optically by interaction between the lasers. The behavior of the coupled lasers is explained by a simple laser model developed in the paper. In particular, the winner take all (WTA) neural-network behavior of a system of many lasers is described. An experimental system is implemented using single mode fiber optic components at wavelengths near 1550 nm. A number of functions are implemented to demonstrate the practicality of the new network. The neural network is particularly robust against input wavelength variations.
TL;DR: In this article, the authors demonstrate continuous-wave parametric amplification using modulational interaction between two spectrally distant optical pumps and a single section of uniform fiber, which is used to synthesize flat parametric gain over more than 22nm bandwidth.
Abstract: The authors demonstrate continuous-wave parametric amplification using modulational interaction between two spectrally distant optical pumps and a single section of uniform fiber. The proposed configuration is used to synthesize flat parametric gain over more than 22-nm bandwidth.
TL;DR: In this paper, a 5×13 TTD unit with a fiber grating prism (FGP) and three discrete fiber Bragg grating (FBG) delay lines is proposed.
TL;DR: In this paper, the authors introduce a general designing procedure that allows us, for any given photonic crystal slab, to create an appropriate line defect structure that possesses single-mode bands with large bandwidth and low dispersion within the photonic band gap region below the light line.
Abstract: We introduce a general designing procedure that allows us, for any given photonic crystal slab, to create an appropriate line defect structure that possesses single-mode bands with large bandwidth and low dispersion within the photonic band gap region below the light line. This procedure involves designing a high index dielectric waveguide that is phase matched with the gap of the photonic crystal slab, and embedding the dielectric waveguide as a line defect into a crystal in a specific configuration that is free of edge states within the guiding bandwidth. As an example, we show a single mode line defect waveguide with a bandwidth approaching 13% of the center-band frequency, and with a linear dispersion relation throughout most of the bandwidth.