Showing papers on "Photonic-crystal fiber published in 1979"
TL;DR: In twisted single-mode optical fibers the polarization of light is affected by an elastooptically induced optical activity and by a modification of any linear birefringence present.
Abstract: In twisted single-mode optical fibers the polarization of light is affected by an elastooptically induced optical activity and by a modification of any linear birefringence present. These effects are discussed theoretically and demonstrated experimentally. The activity/twist ratio is α/τ ≃ 0.13 … 0.16 universally in weakly guiding silica fibers. Twisted fibers may be used as polarization rotators. A fiber with a ±68° double twist operates as a fast/slow mode interchanger, suitable for delay equalization.
760 citations
TL;DR: Raman and Brillouin gains in fibers are a factor of 2 higher if linear polarization is maintained as mentioned in this paper.Birefringent single-mode fibers are used to demonstrate this gain difference.
Abstract: Raman and Brillouin gains in fibers are a factor of 2 higher if linear polarization is maintained. Birefringent single-mode fibers are used to demonstrate this gain difference. Threshold powers of 200 mW have been achieved in Raman oscillators.
285 citations
TL;DR: In this article, the state of polarization at the output end of a long nominally circular single-mode optical fiber is stabilized by an active control system, which contains a polarimeter and two electromagnetic fiber squeezers which introduce variable amounts of stress birefringence directly into the fiber.
Abstract: The state of polarization at the output end of a long nominally circular single‐mode optical fiber is stabilized by an active control system. It contains a polarimeter and two electromagnetic fiber squeezers which introduce variable amounts of stress birefringence directly into the fiber, compensating for the effects of changing intrinsic fiber birefringence.
184 citations
TL;DR: In this paper, a review of state-of-the-art low-loss optical fiber waveguides in both pulsed and steady state radiation environments is given, and the influence on radiation-induced transmission loss due to experimental parameters such as total dose, dose rate, time after irradiation, temperature, wavelength, injection conditions, light intensity and radiation history, and materials parameters, such as OH and impurity content and dopant type and concentration are described.
Abstract: A review of the behavior of state-of-the-art low loss optical fiber waveguides in both pulsed and steady state radiation environments is given. The influence on radiation-induced transmission loss due to experimental parameters such as total dose, dose rate, time after irradiation, temperature, wavelength, injection conditions, light intensity and radiation history, and materials parameters such as OH and impurity content and dopant type and concentration is described. Data are reported for both step and graded index doped silica core fibers and glass clad and polymer clad silica core fibers. Candidate fibers for deployment in certain specific, limited nuclear environments are identified.
137 citations
TL;DR: A three-parameter description of optical fiber material dispersion is proposed which fits the available data and reveals the key roles played by bond length, lattice structure, chemical valence, average energy gap, and atomic mass.
Abstract: A three-parameter description of optical fiber material dispersion is proposed which fits the available data and reveals the key roles played by bond length, lattice structure, chemical valence, average energy gap, and atomic mass. Using broadly applicable trends in electronic and phonon oscillator strengths, simple expressions are deduced for material dispersion including the zero crossover wavelength λc. These results impose severe constraints on fiber design which essentially limit the possibilities for significantly improving on pure silica to sulfates (particularly Li2SO4) and to BeF2. The predicted value of λc for the latter material is 1.05 μm.
127 citations
TL;DR: A birefringent single-mode optical fiber is twisted mechanically in alternating sense on successive half-wave fiber sections to permit continuous adjustment of the state of polarization at the fiber output.
Abstract: A birefringent single-mode optical fiber is twisted mechanically in alternating sense on successive half-wave fiber sections. This arrangement, applicable in-line to a fiber, permits continuous adjustment of the state of polarization at the fiber output.
60 citations
58 citations
TL;DR: In this article, the advantages of single-mode optical fiber transmission technology in the 1.0-1.8-m wavelength region are reviewed and the advantages and progress in fibers, fiber splicing, and devices are discussed.
Abstract: Single-mode optical fiber transmission technology in the 1.0-1.8-{\mu} m wavelength region is reviewed. Owing to low fiber loss in the spectral region and to wide-band single-mode fiber characteristics, longwavelength single-mode fiber transmission systems are capable of high data-rate transmission over tens of kilometers distance without intermediate repeaters. The advantages of the systems and progress in fibers, fiber splicing, and devices are reviewed in detail. Using low-loss fibers and recently developed semiconductor lasers, transmission performance is confirmed at 1.05, 1.1, and 1.5 \mu m wavelengths. At 1.3 {\mu} m, where fiber dispersion almost vanishes, gigabit-per-second pulse signals are successfully transmitted over 20 km without intersymbol interference. The maximum tested data rate is 1.6 Gbit/s, at which 13-km nonrepeatered transmission is confirmed. At 1.5 {\mu} m, where ultimate low-loss characteristics are expected in silica fibers, 100 Mbit/s transmission is successfully demonstrated over a 29-km repeater span. These high data-rate transmission capabilities over long fiber spans are attractive for future communications networks which may provide a variety of services at reduced system cost and with improved maintenance and installation convenience.
52 citations
46 citations
TL;DR: The use of a mode-locked color-center laser is described to demonstrate nearly distortionless propagation of ~5-psec-wide, Fourier-transform-limited pulses, at or near the zero-dispersion wavelength, in two fused-silica, singlemode fibers of 0.76- and 2.5-km length.
Abstract: We describe the use of a mode-locked color-center laser to demonstrate nearly distortionless propagation of ~5-psec-wide, Fourier-transform-limited pulses, at or near the zero-dispersion wavelength, in two fused-silica, singlemode fibers of 0.76- and 2.5-km length, respectively. We also report the detection of sharply defined cross correlations between pulses directly from the laser and those had been delayed many microseconds by passage through a fiber.
46 citations
TL;DR: These new devices utilize a composite structure wherein the fiber is embedded in a material of lower elastic modulus that serves to increase the stress and hence the optical phase shift, in the fiber for a given pressure.
Abstract: Fiber-optic acoustic sensors having sensitivity nearly 2 orders of magnitude greater than that of sensors using bare fiber are reported. These new devices utilize a composite structure wherein the fiber is embedded in a material of lower elastic modulus that serves to increase the stress, and hence the optical phase shift, in the fiber for a given pressure.
Patent•
14 Feb 1979
TL;DR: A fiber-to-fiber coupler is a single-mode or multimode, optical, fiber to fiber coupler which couples such fibers together so that an optical beam guided by one fiber is coupled to the other fiber through evanescent field coupling.
Abstract: A single-mode or multimode, optical, fiber-to-fiber coupler which couples such fibers together so that an optical beam guided by one fiber is coupled to the other fiber through evanescent field coupling. In coupling fibers together, the plastic coating is removed along a desired length of each fiber. The fibers are twisted or braided together and cladding is etched to a desired diameter in a suitable housing. After etching, the etchant is drained and the fibers and inside of the housing are cleaned by any suitable cleaning solution. Subsequent to cleaning, the housing is filled with a solution or material which has an index of refraction which is less than that of the core. It has been determined that coupling efficiency can be controlled simply by adusting the tension of the coupling fibers.
TL;DR: In this paper, a more than 50 percent high power coupling efficiency has been demonstrated between a multi-heterojunction GaAlAs LED and a taper-ended fiber, where the maximum improvement factor beyond the simple butt joint was 5.2.
Abstract: A more than 50 percent high power coupling efficiency has been demonstrated between a multiheterojunction GaAlAs LED (MH LED) and a taper-ended fiber. Optical power values coupled from the MH LED into a Corning silica fiber [numerical aperture (NA) = 0.18] and a Toshiba multicomponent glass fiber (NA = 0.27) were 360 and 560 μW, respectively, at 100 mA drive current. Maximum improvement factor beyond the simple butt joint was 5.2, which is larger than any reported values for edge emitting LED's. Modal power distributions in multimode fiber excited by MH LED with a taper-ended fiber launcher were measured to show the leaky mode contribution negligibly small. Coupling mechanical tolerance and the cladding effect in the tapered section on coupling efficiency are discussed.
Patent•
22 Oct 1979
TL;DR: In this paper, a method for fabricating a fiber with optical cores of diameters between 2 to 20 microns is described, where a preform is drawn into a conventional fiber by conventional techniques resulting in a fiber having an outer diameter of about 120 microns or larger.
Abstract: A method for fabricating a fiber with optical cores of diameters between 2 to 20 microns is depicted. A first step includes the fabrication of a step-index preform of predetermined dimensions. The preform is drawn into a conventional fiber by conventional techniques resulting in a fiber having an outer diameter of about 120 microns or larger. The fiber is then emplaced in a glass tube. The tube is collapsed on the fiber by heating the same resulting in a second preform. This preform is again drawn into a fiber by conventional techniques to obtain a final fiber having core dimensions indicative of single mode operation with compatible outer diameters.
TL;DR: In this article, the authors reported that the lasing spectra of semiconductor lasers coupled to optical fibers with end-butt joint show nearly random lasing at wavelengths decided only by the fiber length.
Abstract: This paper reports that lasing spectra of semiconductor lasers coupled to optical fibers with end-butt joint show nearly random lasing at wavelengths decided only by the fiber length. Wavelength spacing is found to coincide with the resonance wavelength spacing of the optical cavity formed by the optical fiber.
TL;DR: In this paper, the polarization characteristics in cabled single mode fibers were studied using 4.15 km long fibers and a single frequency AlGaAs double-heterostructure laser, interference fringes were observed.
Abstract: Polarization characteristics in cabled single mode fibers were studied. By using 4.15 km long fibers and a single frequency AlGaAs double-heterostructure laser, interference fringes were observed.
01 Oct 1979
TL;DR: In this article, the light from a semiconductor laser is coupled efficiently into a tapered hemispherical-end optical fiber obtained by drawing in an arc discharge, achieving a maximum coupling efficiency of 83 percent for the graded index fiber having a 60µm core diameter.
Abstract: The light from a semiconductor laser is coupled efficiently into a tapered hemispherical-end optical fiber obtained by drawing in an arc discharge. The maximum coupling efficiency of 83 percent is achieved for the graded index fiber having a 60-µm core diameter. Permissible transverse displacement for a 1-dB decrease of coupling is about 19 µm.
TL;DR: In this paper, the authors used a fiber optic waveguide as the dispersing element in a time-of-flight optical spectrometer to measure the transport time and pulse broadening within an 1100m optical fiber.
Abstract: Transit time and pulse broadening within an 1100-m optical fiber have been studied with single photon time-correlation techniques at a number of wavelengths. The results confirm that a fiber optic waveguide can be used as the dispersing element in a time-of-flight optical spectrometer. 4 figures.
TL;DR: The air bubbles sometimes observed at the splicing point in fusion splices were avoided by preparing fiber ends with a laser-scribing method.
Abstract: Mirror-finished end preparation and low-loss splicing of silica fiber arrays by means of a CO(2) laser are demonstrated. Eight-fiber linear arrays of multimode fibers with 60-microm core diam and 150-microm outer diam were laser scribed and fractured, then butted and spliced with 3.0-W laser power output, 1.0-mm beam-spot diam, and 15-microm/sec fiber array driving speed. Average splice losses for 20x splicings (160 splices) in step- and graded-index fibers were 0.12 db and 0.10 dB, respectively. The air bubbles sometimes observed at the splicing point in fusion splices were avoided by preparing fiber ends with a laser-scribing method.
TL;DR: From the measured data, the optimum profile parameter on the GeO(2)-P(2)O(5)-doped silica graded-index fiber could be estimated to be 1.88 at 1.27 microm of the material dispersion free wavelength region and 1.82 at 1% of the lowest-loss wavelength region in silica-based optical fiber waveguides.
Abstract: To study the material dispersion effects on graded-index fibers, a method for measuring the material dispersion in optical glass fibers has been developed. Nanosecond pulses in the 0.5-1.7-microm region are generated by a nanosecond optical pulse radiator and grating monochromator. These pulses are injected into a GeO(2)-P(2)0(5)-doped silica graded-index fiber. Relative time delay changes between different wavelengths are used to determine material dispersion, core glass refractive index, material group index, and optimum profile parameter of the graded-index fiber. From the measured data, the optimum profile parameter on the GeO(2)-P(2)O(5)-doped silica graded-index fiber could be estimated to be 1.88 at 1.27 microm of the material dispersion free wavelength region and 1.82 at 1.55 microm of the lowest-loss wavelength region in silica-based optical fiber waveguides.
TL;DR: A sensitive, nondestructive, and noncontacting method is described for obtaining structural information on the preforms from which optical fibers are produced and results and implications are presented along with a theoretical analysis of the observations.
Abstract: A sensitive, nondestructive, and noncontacting method is described for obtaining structural information on the preforms from which optical fibers are produced. The technique allows the determination of the core size and the core eccentricity from direct observation of light traversing the preform normal to its axis. Also observable are the core–cladding interface structure, individual deposition layer structure and variations, imperfections within the core and the cladding, and the presence of an axial refractive-index depression. Results and implications from a variety of multimode and single-mode preforms are presented along with a theoretical analysis of the observations.
01 Jan 1979
TL;DR: In this article, the feasibility of using polycrystalline alkali halides as waveguides with predicted losses as low as 0.01 dB/km at selected near-infrared wavelengths was investigated.
Abstract: Recent advances in the technology of fabricating infrared optical-fiber waveguides together with advances in the development of highly transparent infrared window materials show great promise for the development of ultra low-loss infrared transmitting fiber-optical waveguides suitable for communication links. Theoretical calculations indicate the feasibility of using polycrystalline alkali halides as waveguides with predicted losses as low as 0.01 dB/km at selected near-infrared wavelengths.
TL;DR: This paper considers the signal bandwidth of germanium- and phosphorus-doped fibers with ideal power law refractive index profiles and investigates how the bandwidth as a function of wavelength (bandwidth spectrum) is changed as the ideal index profile is distorted.
Abstract: This paper presents some thoughts on how to improve the bandwidth spectrum of multimode optical fibers. We consider the signal bandwidth of germanium- and phosphorus-doped fibers with ideal power law refractive index profiles and investigate how the bandwidth as a function of wavelength (bandwidth spectrum) is changed as the ideal index profile is distorted. We also study what happens if two fibers with different undistorted power law profiles are used in cascade. Examples are also given of bandwidth calculations of fibers made with a mixture of germanium and phosphorus dopants. It is shown that such fibers are capable of realizing a bandwidth which exceeds 5 GHz·km over a wavelength range from 0.8 μm to 1.45 μm. Finally, bandwidth vs wavelength curves are computed for several real fibers whose refractive index profiles were measured.
TL;DR: The wavelength of minimum dispersion of monomode fibers is shown to depend on the refractive properties of the core glass as well as of the cladding glass and on the fiber parameter V, providing a wide choice of operating wavelengths for high-capacity communication systems.
Abstract: The wavelength of minimum dispersion of monomode fibers is shown to depend on the refractive properties of the core glass as well as of the cladding glass and on the fiber parameter V. Minimum-dispersion wavelengths in the 1.27-microm < lambda < 1.6-microm range are readily obtained with fibers made of fused silica and fused silica doped with GeO(2) and B(2)O(3), thus providing a wide choice of operating wavelengths for high-capacity communication systems.
TL;DR: In this paper, the authors investigated the transmission characteristics of graded-index fibers at 1.27 μm and showed that the optimum profile at 0.83 μm is 2.98.
Abstract: Transmission characteristics of graded-index fibers at 1.27 μm are investigated. Bandwidth measurements are made in the frequency domain by using a CW GaInAsP laser diode modulated by a sinusoidal signal. For a germanium pbosphosilicate fiber, the optimum index profile at 1.27 μm is determined as 1.98. It is shown that optimum profile at 0.83 μm is 2.08 and there exists a large profile dispersion effect: for example, the experimental maximum 3-dB bandwidth at 1.27 μm decreases to one-third at 0.83 μm. Length dependence of bandwidth is investigated for 48 km long spliced graded-index fibers at 1.27 μm. It is verified that using a simplified transmission model in which mode conversion is assumed at splicing points, the bandwidths of long spliced fibers are predicted with satisfactory accuracy in terms of unit fiber transfer functions.
TL;DR: It was confirmed that the spliced fiber also has a wavelength-dependent characteristic, and that the interfiber compensation of the intermodal dispersion actually occurs in the wavelength region between the optimum wavelengths at which the individual fibers have maximum bandwidths.
Abstract: Profile dispersion affects the bandwidth of graded-index multimode fibers. In this paper, two graded-index multimode fibers of nearly 2-km length, of different index profile, and the combined fiber obtained by splicing them are examined by the swept-frequency method. It was confirmed that the spliced fiber also has a wavelength-dependent characteristic, and that the interfiber compensation of the intermodal dispersion actually occurs in the wavelength region between the optimum wavelengths at which the individual fibers have maximum bandwidths. Moreover, transverse displacement of the fibers in the splice was found to have a wavelength-dependent effect on the bandwidth.
TL;DR: In this paper, the effects of changing the shape of the refractive-index profile of the fiber core on the secondary maxima were investigated, and the power distribution of the light propagating in the core region is compared to the refraction-index distribution.
Abstract: Photoelectric and photographic techniques have been used to measure and display the intensities and positions of as many as six secondary maxima in the far-field radiation patterns of a variety of low V-number optical fibers. The effects of changing the shape of the refractive-index profile of the fiber core on the secondary maxima are investigated. The power distribution of the light propagating in the core region is compared to the refractive-index distribution.
TL;DR: In this paper, general mathematical and numerical results for graded-index optical fibers excited by parallel beams are given, and the relevance of the results to other problems such as fiber excitation by partially coherent sources and the appearance of fiber output faces is discussed.
Abstract: General mathematical and numerical results are given for graded-index optical fibers excited by parallel beams. The excitation of bound and tunneling rays and their influence on power transmission and impulse response are described. The relevance of the results to other problems such as fiber excitation by partially coherent sources and the appearance of fiber output faces is discussed. The graded-index fiber equivlent of the black-band phenomena in step-index fibers is described and an application to profile determination is considered.
TL;DR: In this article, the current state of the art in optical communication fiber waveguide fabrication is reviewed, and the relative advantages and disadvantages of different fiber fabrication techniques are discussed in the summary.
Abstract: The current state of the art in optical communication fiber waveguide fabrication is reviewed. Details of the two main technologies—multi-component glasses and high-silica glasses—are described, followed by brief details of other fiber fabrication techniques. The relative advantages and disadvantages of the different fiber fabrication techniques are discussed in the summary.