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Showing papers on "Single-mode optical fiber published in 1988"


Journal ArticleDOI
TL;DR: In this article, the effect of external feedback on a single-mode semiconductor laser is estimated by a numerical solution of the nonlinear rate equations, and it is found that the lasing mode with the minimum linewidth is most stable rather than the mode with minimum threshold gain.
Abstract: The effect of external feedback on a single-mode semiconductor laser is estimated by a numerical solution of the nonlinear rate equations. The analysis yields an excellent description of published experimental results. It is found that the lasing mode with the minimum linewidth is most stable rather than the mode with minimum threshold gain. The transition to the coherence-collapse regime is of particular interest. It usually occurs for feedback fractions approximately=10/sup -4/, but it can be shifted to considerably larger feedback levels either by increasing the emitted optical power or the laser length or by decreasing the linewidth enhancement factor alpha . >

266 citations


Journal ArticleDOI
TL;DR: In this paper, a method to determine the individual strain-optic coefficients in single-mode fibers is described, based on two photoelastic experiments, namely, the polarimetric measurement of optical activity induced by mechanical twist and the interferometric measurement of optic-path-length change induced by static longitudinal strain.
Abstract: A method to determine the individual strain-optic coefficients in single-mode fibers is described. It is based on two photoelastic experiments, namely, the polarimetric measurement of optical activity induced by mechanical twist and the interferometric measurement of optical-path-length change induced by static longitudinal strain. For fibers with pure silica core and B/sub 2/O/sub 3/ doped cladding, the optical activity per unit twist rate and the phase change per unit fiber elongation have been measured to be 0.1472 and 1.150*10/sup 7/ rad/m, respectively. The strain-optic coefficients have been measured to be p/sub 11/=0.113 and p/sub 12/=0.252, 7% lower than those of bulk silica. >

240 citations


Journal ArticleDOI
TL;DR: Measurements of the reshaping of 0.3-psec dark pulses due to their passage through 10 m of single-mode optical fiber suggest the formation of dark-pulse solitons, according to the predictions of the nonlinear Schr\"odinger equation.
Abstract: We report measurements of the reshaping of 0.3-psec dark pulses due to their passage through 10 m of single-mode optical fiber. The measurements were performed as a function of intensity and the observed strong reshaping agrees qualitatively with the predictions of the nonlinear Schr\"odinger equation which suggest that we have observed the formation of dark-pulse solitons.

231 citations


Proceedings ArticleDOI
27 Jan 1988
TL;DR: In this article, the behavior of a single mode Nd fiber laser with a double clad configuration is described in which light focused into the first cladding is absorbed by the neodymium core as the pump light proceeds down the fiber.
Abstract: The earlier glass lasers in both rod and fiber form were mostly side pumped.1 With the demonstration of single mode CW fiber lasers doped with Nd in low loss glass2 there followed considerable work with end pumped fiber lasers with many of the rare earths that had lased.3-6 In this paper, the behavior of a single mode Nd fiber laser with a double clad configuration is described in which light focused into the first cladding is absorbed by the neodymium core as the pump light proceeds down the fiber. This allows use of multimode pump sources and relatively simple focusing systems for efficient coupling.

229 citations


Journal ArticleDOI
Craig D. Poole1
TL;DR: Polarization dispersion in single-mode fiber with random polarization mode coupling is given a statistical treatment based on the recently proposed principal-states model and the variance is shown to have a linear dependence on length while the probability density function for the delay time approaches a Gaussian shape.
Abstract: Polarization dispersion in single-mode fiber with random polarization mode coupling is given a statistical treatment based on the recently proposed principal-states model. An expression for the ensemble variance of the differential delay time between the principal states of polarization is derived by using coupled-mode theory under the assumption of weak coupling. For long fiber lengths, the variance is shown to have a linear dependence on length while the probability density function for the delay time approaches a Gaussian shape.

220 citations


Book
01 Jan 1988
TL;DR: Physical Explanation of Waveguiding by Single-Mode Fibers by Electromagnetic Fields and Gaussian Beams is given in this paper, where the fundamental fiber mode and higher-order modes are discussed.
Abstract: Physical Explanation of Waveguiding by Single-Mode Fibers.- Electromagnetic Fields.- Gaussian Beams.- The Fundamental Fiber Mode.- Higher-Order Modes.- Launching of Modes.- Radiation from the Fiber End.- Joints Between Fibers.- Spot Size and Width of the Radiation Pattern.- Signal Transmission Through Single-Mode Fibers.- Components for Single-Mode Fibers.- Measuring Techniques.

214 citations


Journal ArticleDOI
Yasuhiro Aoki1, K. Tajima1, Ikuo Mito1
TL;DR: In this article, the authors investigated SBS gain and threshold characteristics with amplitude-shift-keying (ASK), frequency-shift keying (FSK), and phase-shiftkeying modulated lights to estimate the input power limitation.
Abstract: Stimulated Brillouin scattering (SBS) limits the optical power that can be transmitted through a single-mode fiber in long-distance optical communication systems, the authors have investigated SBS gain and threshold characteristics with amplitude-shift-keying (ASK), frequency-shift-keying (FSK), and phase-shift-keying (PSK) modulated lights to estimate the input power limitation set by SBS. It was shown that maximum fiber-input powers or the SBS thresholds for fixed-pattern (1010 . . .) ASK, FSK, and PSK modulated lights are 2, 4, and 2.5 times higher, respectively, than the threshold for unmodulated light. Theoretical predictions were experimentally verified by SBS gain measurements with FSK and PSK modulated lights. The first direct observation of SBS with FSK modulated light pumping is also described. >

210 citations


Journal ArticleDOI
TL;DR: The efficiency with which starlight can be coupled into a single-mode fiber optic that is placed in the focal plane of a telescope and the dependence on the f-ratio of the incident beam is explored.
Abstract: We have calculated the efficiency with which starlight can be coupled into a single-mode fiber optic that is placed in the focal plane of a telescope. The calculations are performed for a wide range of seeing conditions, with and without rapid image stabilization, and for a wide range of wavelengths. The dependence of coupling efficiency on the f-ratio of the incident beam is explored. Also, we calculate the coupling efficiency as a function of displacement for a perfect Airy pattern. We have also used a computer program which simulates atmospheric wavefronts to determine the variance of instantaneous coupling efficiency as a function of seeing. In perfect conditions, the maximum efficiency at the LP(11) mode cutoff is 78% due to the mismatch of the Airy pattern and the nearly Gaussian mode of the fiber. Maximum total coupled power is attained at d/r(0) = 4 with rapid image stabilization.

207 citations


Journal ArticleDOI
TL;DR: RefReflectively monitored Fabry-Perot interferometers which make use of dielectric mirrors in continuous lengths of single mode fiber are characterised for use as temperature and wavelength sensors as discussed by the authors.
Abstract: Reflectively monitored Fabry-Perot interferometers which make use of dielectric mirrors in continuous lengths of single mode fibre are characterised for use as temperature and wavelength sensors.

204 citations


Journal ArticleDOI
TL;DR: In this article, the first mixed-type solutions to the coupled nonlinear Schrodinger equations which govern optical pulse propagation in a birefringent fiber were presented, which are bound states of two solitary waves which separately have constant and uniform orthogonal linear polarizations.
Abstract: We present the first mixed-type solutions to the coupled nonlinear Schr\"odinger equations which govern optical pulse propagation in a birefringent fiber. These represent polarization-modulated pulses which, apart from the absolute phase, propagate unchanged in form. It is shown they are bound states of two solitary waves which separately have constant and uniform orthogonal linear polarizations. Furthermore, there exists a minimum-energy threshold for the formation of these bound states.

152 citations


Journal ArticleDOI
TL;DR: In this paper, the conditions necessary for the amplitude or the temporal width of an N = 1 soliton to increase, remain constant, or decrease with distance on an axially nonuniform optical fiber are derived.
Abstract: The conditions necessary for the amplitude or the temporal width of an N = 1 soliton to increase, remain constant, or decrease with distance on an axially nonuniform optical fiber are derived. Numerical results for a step-index fiber with an axially tapered core are presented. The effects of such a fiber on higher-order solitons are also presented.

Journal ArticleDOI
TL;DR: In this paper, the authors presented an architecture for constructing reflective single-mode fiber-optic passive star couplers for high-speed optical local-area networks using simple components, e.g., 3-dB coupler and mirrors, and showed that the number of components needed to construct a reflective star is half of that needed for an equivalent transmissive star.
Abstract: Architecture arrangements for constructing reflective single-mode fiber-optic passive star couplers for high-speed optical local-area networks using simple components, e.g. 3-dB couplers and mirrors, are presented. Besides the savings of fibers, the number of components needed to construct a reflective star is shown to be half of that needed for an equivalent transmissive star. To avoid unpredictable interference effects, only structures that are free of multipaths are considered. >

Journal ArticleDOI
TL;DR: An ultrafast all-optical switching scheme utilizing the optical Kerr effect in two birefringent fibers concatenated with each fast axis crossed is proposed and the nondiagonal yx component of the nonlinear refractive index is determined to be 0.34 relative to the diagonal component xx.
Abstract: An ultrafast all-optical switching scheme utilizing the optical Kerr effect in two birefringent fibers concatenated with each fast axis crossed is proposed Stable optical Kerr modulation and all-optical demultiplexing of an ultrashort (30 ps) optical pulse train at 197 GHz from a gain-switched distributed-feedback laser diode (DFB LD) have been sufficiently demonstrated using CW mode-locking Nd:YAG laser pulses as a pump Switching speed and required pump powers are studied in terms of fiber bandwidth due to fiber birefringence, and combined effects of chromatic and polarization dispersions on Kerr modulation profiles By utilizing the optical Kerr modulation properties in the presence of dispersions, the nondiagonal yx component of the nonlinear refractive index is also determined to be 034 relative to the diagonal component xx The intrinsic stability and ultimate switching capabilities are discussed >

Journal ArticleDOI
TL;DR: Several resonance peaks owing to an interaction between light-wave and guided modes of longitudinal acoustic waves are observed in the Brillouin gain spectra for a single-mode fiber with a GeO2-doped core and pure silica cladding.
Abstract: Several resonance peaks owing to an interaction between light-wave and guided modes of longitudinal acoustic waves are observed in the Brillouin gain spectra for a single-mode fiber with a GeO2-doped core and pure silica cladding. Brillouin gain spectra measurements are carried out at 1286- and 1550-nm wavelengths. Longitudinal acoustic modes guided in the GeO2-doped core region are identified by applying the analysis of leaky modes in a fiber acoustic waveguide.

Journal ArticleDOI
TL;DR: In this paper, room temperature all-optical switching has been achieved in singlemode strip-loaded nonlinear directional couplers with a GaAs/AlGaAs multiple quantum well guiding layer.
Abstract: Room‐temperature all‐optical switching has been achieved in single‐mode strip‐loaded nonlinear directional couplers with a GaAs/AlGaAs multiple quantum well guiding layer. For low input intensities nearly complete (1:3–1:5) cross coupling occurs, while at high input intensities switching occurs so that most (>3:1) of the light stays in the input guide. The effects of carrier diffusion are minimized by the use of picosecond pulses. The response time and the recovery time of the nonlinear directional couplers are measured with pump‐probe experiments, and the origin of the nonlinearity is attributed to fast electronic effects.

Journal ArticleDOI
TL;DR: In this paper, a singlemode resonator is constructed by joining together the ends of the coupled fiber of a 2 × 2 directional single-mode optical fiber coupler, and analytical expressions are obtained for the resonance conditions.
Abstract: A single-mode resonator is constructed by joining together the ends of the coupled fiber of a 2 × 2 directional single-mode optical fiber coupler. Analytical expressions are obtained for the resonance conditions. The effects of different kinds of losses are investigated. The variation of the phase at resonance and the problem of mismatch are discussed. A formula for the finesse of the resonator is also given. Unlike reentry fiber resonators, this kind of resonator needs a directional coupler with only a small coupling coefficient. It is possible to achieve a high finesse and symmetrical outputs. Applications of such a resonator are discussed.

Patent
09 Sep 1988
TL;DR: In this article, an optical fiber comprising a transparent core having a maximum refractive index n 1 and a radius a surrounded by a layer of transparent cladding material has been designed such that the difference between |d(Vb)/dV| j, the normalized delay time of the jth mode, is less than about 5×10 -2 over a wide range of V-values where j is equal to 1 or 2 and represents the highest order mode that propagates with a low loss, 0 represents the fundamental mode, b is the propagation constant and V is the
Abstract: The present invention pertains to an optical fiber comprising a transparent core having a maximum refractive index n 1 and a radius a surrounded by a layer of transparent cladding material having a refractive index n 0 which is less than n 1 . The refractive indices n 1 and n 0 , the radius a, and the refractive index profile of the core are designed such that: (a) Δτ j , the difference between |d(Vb)/dV| j , the normalized delay time of the jth mode and |d(Vb)/dV| 0 , the normalized delay time of the fundamental mode, is less than about 5×10 -2 over a wide range of V-values where j is equal to 1 or 2 and represents the highest order mode that propagates with a low loss, 0 represents the fundamental mode, b is the propagation constant and V is the normalized frequency, and (b) the normalized waveguide dispersion Vd 2 (Vb)/dV 2 is about equal to or less than 0.2 at V-values near V 1 c , the normalized cutoff frequency of the first higher order mode. A fiber exhibiting characteristics (a) and (b) is capable of providing mode equalized two-mode or three-mode and low dispersion single-mode operation.

Journal ArticleDOI
TL;DR: In this article, several guided acoustic modes are identified to be responsible for the stimulated backward Brillouin scattering (SBBS) in single-mode optical fibres (SMFs), and the dependence of SBBS gain spectra on acoustic properties of SMF is discussed.
Abstract: Several guided acoustic modes are identified to be responsible for the stimulated backward Brillouin scattering (SBBS) in single-mode optical fibres (SMFs). The dependence of SBBS gain spectra on acoustic properties of SMF is discussed.

Journal ArticleDOI
TL;DR: In this paper, a method of obtaining tapered single mode fiber cores by controlled thermal diffusion of the dopant is described, which shows an increased tolerance to longitudinal and transverse offsets.
Abstract: A method of obtaining tapered single mode fibre cores by controlled thermal diffusion of the dopant is described. The mechanical fibre dimensions are maintained during this process. Extended tapers have been produced, which show an increased tolerance to longitudinal and transverse offsets. Such tapers will prove useful for a range of optical fibre components.

Patent
02 Dec 1988
TL;DR: In this paper, a distributed black reflector which reflects a laser beam to the double-hetero structure is provided on a semiconductor substrate common with the laser beam emitting part and in the region where an optical waveguide is formed.
Abstract: PURPOSE:To improve the conversion factor and reduce the size of a semiconductor light emitting device by a method wherein a distributed black reflector which reflects a laser beam to a laser beam emitting part side is provided on a semiconductor substrate common with the laser beam emitting part and in the region where an optical waveguide is formed CONSTITUTION:An optical waveguide 36 which is made of nonlinear optical material and guides a laser beam and converts a part of the laser beam into a 2nd harmonic beam is provided and integarated on a common substrate 20 and on the side of the end surface of the semiconductor laser 22 of a double- hetero structure 24 through which the laser beam enters and comes out A distributed black reflector 38 which reflects the laser beam to the double-hetero structure 24 side is provided in the region where the optical waveguide 36 is formed so as to constitute a resonator of a semiconductor light emitting device for the emitted laser beam and to transmit the 2nd harmonic beam With this constitution, a single mode oscillation can be realized and the conversion factor can be improved and, moreover, the size of the semiconductor light emitting device can be reduced

Journal ArticleDOI
TL;DR: A new optical-optical switching technique is proposed and demonstrated with a probe-pump scheme, utilizing nonlinear differential phase shift between two spatial modes in a highly elliptical-core fiber.
Abstract: A new optical–optical switching technique is proposed and demonstrated with a probe–pump scheme, utilizing nonlinear differential phase shift between two spatial modes in a highly elliptical-core fiber. The probe beam is switched from one intensity-lobe position of the fiber output radiation pattern to the other in a 33-m-long fiber at a pump power of 1.6 W.

Journal ArticleDOI
TL;DR: Pulses launched with their central wavelength in the region of the minimum-dispersion wavelength of a single-mode optical fiber exhibit a distinct spectral splitting due to the nonlinearity, in qualitative agreement with theoretical prediction.
Abstract: Pulses launched with their central wavelength in the region of the minimum-dispersion wavelength of a single-mode optical fiber exhibit a distinct spectral splitting due to the nonlinearity. As a solitary wave evolves, the corresponding central wavelength of this component frequency downshifts while the dispersive wave is upshifted, in qualitative agreement with theoretical prediction.

Journal ArticleDOI
TL;DR: In this article, a novel design for symmetric Y-junctions using two abrupt-bend structures with relatively large tilt angles was proposed. But the proposed Y-junction has a relatively low refractive index region operating as a phase-front accelerator and is shown to have loss significantly reduced in comparison with a conventional Y junction with a large branching angle.
Abstract: We report a novel design for symmetric Y-junctions using two abrupt-bend structures with relatively large tilt angles. The proposed Y-junction has a relatively low refractive index region operating as a phase-front accelerator and is shown to have loss significantly reduced in comparison with a conventional Y-junction with a large branching angle.

Journal ArticleDOI
TL;DR: In this article, an approximate method for analyzing planar optical Y-junctions is presented, where the junction structure is replaced by a discrete succession of bounded waveguide segments, and the presence of waveguide bends is assumed.
Abstract: An approximate method for analyzing planar optical Y-junctions is presented. The junction structure is replaced by a discrete succession of bounded waveguide segments, and the presence of waveguide bends is assumed. Using this approximation, single-mode symmetrical Y-junctions operated as power dividers are investigated numerically. It is shown that strong mode conversion occurs between the guided and radiation modes of the local normal mode. A perturbation analysis shows that reflected fields are negligible. Reliable values of the transmitted power are obtained. >

Journal ArticleDOI
TL;DR: In this article, the frequency chirps of the first-Stokes Raman (1.12-μm) and fundamental Raman radiation were measured through various lengths of single-mode optical fiber.
Abstract: The frequency chirps of the first-Stokes Raman (1.12-μm) and fundamental (1.06-μm) picosecond (~100-psec) pulses propagated through various lengths of single-mode optical fiber have been measured. The fiber lengths were varied from a regime in which walk-off was significant to a regime where it could be neglected. Besides being of positive sign and substantially greater than that of the fundamental, the chirp of the Raman radiation was found to be highly nonlinear, in good qualitative agreement with theoretical predictions.

Patent
08 Sep 1988
TL;DR: In this paper, an optical communication system includes an optical transmitter for transmitting a subcarrier multiplexed optical signal through a single mode optical fiber to an optical receiver, where the light beam is modulated with a composite modulation signal to provide the optical signal for transmission.
Abstract: An optical communication system includes an optical transmitter for transmitting a subcarrier multiplexed optical signal through a single mode optical fiber to an optical receiver. The optical transmitter includes a semiconductor laser diode for generating a light beam. The laser diode is preferably a high speed InGaAsP laser diode emitting in a spectral range of 1.3-1.6 micrometers. The light beam is intensity modulated with a composite modulation signal to provide the optical signal for transmission. The composite modulation signal includes multiple modulated microwave carriers that cover a total bandwidth greater than one octave. Harmonics and intermodulation products do not interfere with transmission, and a favorable signal-to-noise ratio or bit error rate is maintained when the bandwidth of the composite modulation signal exceeds one octave.

Patent
28 Apr 1988
TL;DR: In this paper, a birefringent single-mode optical fiber (200) which propagates light into orthogonal polarization modes is subjected to a series of second order traveling flexural waves for propagation within the fiber.
Abstract: A birefringent single-mode optical fiber (200) which propagates light into orthogonal polarization modes is subjected to a series of second order traveling flexural waves for propagation within the fiber (200). An acoustic wave generator (202) applies a periodic lateral squeezing force to the fiber (200), thus causing a second order flexural wave to propagate within the fiber (200). The wavelength of the second order flexural wave is selected to cause light propagating in one polarization mode to be coupled to the orthogonal polarization mode. The optical signal in the second orthogonal propagation mode has a frequency which is equal to either the sum of or the difference between the frequency of the optical signal in the first propagation mode and the frequency of the traveling flexural wave. The frequency of the optical signal in the second orthogonal propagation mode is shifted upward of or downward from the frequency of the optical signal in the first propagation mode as determined by the direction of propagation of the first optical signal with respect to the direction of propagation of the traveling flexural wave, and as also determined by whether the phase propagation velocity of the optical signal in the first propagation mode is greater or less than the propagation velocity of the optical signal in the second propagation mode. The centripetal couple of squeezing forces is preferably oriented at an angle of substantially 45° with respect to the axes of birefringence of the fiber (200).

Journal ArticleDOI
Yasuhiro Aoki1, Kazuhito Tajima1
TL;DR: In this paper, the threshold of the stimulated Brillouin scattering (SBS) in a long single-mode fiber excited with a multimode pump laser was investigated, and it was theoretically shown that when the mode spacing of the pump laser is larger than the Brilloughin-gain bandwidth, each Stokes mode experiences gain from only one pump mode and builds up independently in the long fiber with long interaction length.
Abstract: The threshold of the stimulated Brillouin scattering (SBS) in a long single-mode fiber excited with a multimode pump laser is investigated. It is theoretically shown that when the mode spacing of the pump laser is larger than the Brillouin-gain bandwidth, each Stokes mode experiences gain from only one pump mode and builds up independently in a long fiber with long interaction length. On the basis of this fact, the SBS threshold with an N-multimode pump with equal intensities is predicted N times greater than that with a single-mode pump. The theoretical predictions are verified by an experiment in which the number of longitudinal modes of a 1.32-μm Nd:YAG laser is changed.

Journal ArticleDOI
TL;DR: In this paper, the chromatic dispersion of a 70km single-mode fiber with 1.3μm zero dispersion wavelength is compensated for using a microstrip line equaliser in the intermediate frequency band.
Abstract: Compensation of fibre chromatic dispersion in coherent optical fibre transmission is demonstrated. The chromatic dispersion of a 70km single-mode fibre with 1.3μm zero dispersion wavelength is compensated for using a microstrip line equaliser in the intermediate frequency band. Amplitude distortion due to fibre chromatic dispersion at 1.55μm wavelength is reduced to below 2.5% with the equaliser.

Journal ArticleDOI
TL;DR: The experimental behavior of the reflector with different levels of stress applied to the fiber loop and different lengths of highly birefringent fiber spliced into the loop are compared and confirm the initial postulate that stray bireFringence degrades the performance of the single-mode fiber Sagnac reflector.
Abstract: It is postulated that stray birefringence degrades the performance of the single-mode fiber Sagnac reflector. An expression for the birefringence dependence of reflector performance is derived using the Jones calculus and is used as the basis for a theoretical model of the spectral response of a real Sagnac reflector. The experimental behavior of the reflector with (1) different levels of stress applied to the fiber loop and (2) different lengths of highly birefringent fiber spliced into the loop are compared with the model. This comparison confirms the initial postulate.