Showing papers on "Photonic-crystal fiber published in 1981"
TL;DR: It is shown that whereas a conventionally twisted fiber possesses considerable optical rotation, a fiber which has a permanent twist imparted by spinning the preform during fiber drawing exhibits almost no polarization anisotropy, making it possible to virtually eliminate the commonly observed fiber linear birefringence.
Abstract: A theoretical and experimental analysis of the polarization properties of twisted single-mode fibers is presented. It is shown that whereas a conventionally twisted fiber possesses considerable optical rotation, a fiber which has a permanent twist imparted by spinning the preform during fiber drawing exhibits almost no polarization anisotropy. It is thus possible to virtually eliminate the commonly observed fiber linear birefringence. As a consequence, fibers made in this way are ideally suited for use in the Faraday-effect current transducer. It is further shown that a permanent twist of a few turns/meter effectively eliminates polarization mode-dispersion. The technique therefore appears attractive for enhancing the bandwidth of very long unrepeatered telecommunication links.
283 citations
TL;DR: Single-mode fiber couplers produced as fused biconical-taper structures are reported on that exhibit low loss, arbitrary branching ratio, polarization independence, and broadband operation in wavelength.
Abstract: Single-mode fiber couplers produced as fused biconical-taper structures are reported on. The devices exhibit low loss (0.5 dB), arbitrary branching ratio, polarization independence, and broadband operation in wavelength.
231 citations
TL;DR: A theoretical model is developed, and relevant fiber parameters are determined through intercomparison with experiment, both the magnitude of the photoinduced index change and its dependence on the writing power coupled into the fiber are determined.
Abstract: The fabrication of narrowband highly reflecting filters in single-mode step-index fibers was reported recently by Hill et al. [
Appl. Phys. Lett.32,
647 (
1978)]. The underlying effect on which these filters are based is a photoinduced refractive-index change in the GeO2 used as a core dopant SiO2 fibers. A study is reported aimed at the characterization of such optical fiber filters. A theoretical model is developed, and relevant fiber parameters are determined through intercomparison with experiment. In this way, both the magnitude of the photoinduced index change and its dependence on the writing power coupled into the fiber are determined.
221 citations
TL;DR: In this paper, the effects of twist in an elliptical core fiber gave rise to a polarization whose major axis points in an intrinsic direction with an azimuthal angle, where φ t is the torsion per unit length and z is the fiber length.
Abstract: Birefringence and polarization dispersion caused by: 1) elliptical core, 2) twist, 3) pure bending, 4) transverse pressure, and 5) axial tension are studied by treating these deformations as perturbations to step-index single-mode fiber with a round core. These effects ate formulated in terms of fiber structure and perturbation parameters and are compared comprehensively. Birefringence depends strongly on factors 1)-4), while polarization dispersion depends on factors 1), 3), and 4). Polarization performance of twisted elliptical core fibers was also studied. Twist in an elliptical core fiber gives rise to a polarization whose major axis points in an intrinsic direction with an azimuthal angle \phi_{t}z , where φ t is the torsion per unit length and z is the fiber length.
173 citations
128 citations
TL;DR: A new technique that utilizes birefringence for phase matching of stimulated parametric emission in a single-mode optical fiber and the frequency shift between the generated frequencies and the pump frequency can be controlled over a wide range by the magnitude of bireFringence built into the fiber.
Abstract: We describe a new technique that utilizes birefringence for phase matching of stimulated parametric emission in a single-mode optical fiber. The frequency shift between the generated frequencies and the pump frequency can be controlled over a wide range (approximately 1000 cm(-1)) by the magnitude of birefringence built into the fiber.
113 citations
TL;DR: In this article, three basic types of single-polarization single-mode (SPSM) optical fibers have been developed: elliptical-core fiber, stress-induced birefringent fiber, and side-pit fiber.
Abstract: Strictly speaking, an ordinary axially symmetrical single-mode fiber is a "two-mode" fiber because two orthogonally polarized HE 11 modes can be propagated in it. This fact results in the instability of the polarization state of the propagated mode when geometrical perturbation exists in the fiber, and also the so-called polarization mode dispersion. These are harmful in some applications of single-mode fibers to communication and measurement. To prevent these adverse effects, single-polarization single-mode (SPSM) optical fibers have been developed. Three basic types of the SPSM fiber are elliptical-core fiber, stress-induced birefringent fiber, and side-pit fiber. This paper describes the principles of these three types, performance obtained experimentally, theoretical approaches, and measurement techniques related to the SPSM fibers. Finally, relevant technical tasks in the future are mentioned.
103 citations
TL;DR: The local parameters of linear, circular, and elliptical birefringence of backscattered light along a single-mode fiber are analyzed, and the twist-bending-induced ellipticalbireferingence in an extremely low bireFringent single- mode fiber is measured using the backscattering method.
Abstract: The local parameters of linear, circular, and elliptical birefringence of backscattered light along a single-mode fiber are analyzed, and the twist–bending-induced elliptical birefringence in an extremely low birefringent single-mode fiber is measured using the backscattering method. The experimental results are in good agreement with the theoretical calculations. For a 130-μm-diameter fiber, twisted by 133°/m and wound around a drum of 15-cm radius, the induced elliptical birefringence is|Ω| = 18°/m at λ = 904 nm.
96 citations
TL;DR: The effects of group-velocity dispersion, thermal stability of polarization, and fiber birefringence are investigated, and it is concluded that resolution times shorter than 1 psec are possible in principle.
Abstract: Optical Kerr modulation of >100% is demonstrated in long birefringent optical fibers using low laser powers of ~1 W. We have experimentally investigated the effects of group-velocity dispersion, thermal stability of polarization, and fiber birefringence. Use of fiber Kerr modulation as a fast optical shutter is studied, and it is concluded that resolution times shorter than 1 psec are possible in principle.
90 citations
TL;DR: In this paper, the requirements of such a system are reviewed and interpreted in terms of individual components design, and it is concluded from these very promising results that a heterodyne-type communication system using single-mode fibers at 1.6 μm may offer repeater spacings of over 200 km in the near future.
Abstract: The unique performances attached to the heterodyne (or coherent) optical detection process can be fully exploited with single-mode fiber transmission. Strong improvement over direct detection is expected in terms of bit error rate (BER) or in terms of repeater spacing, especially for 1.6 μm operation. The requirements of such a system are reviewed and interpreted in terms of individual components design. The emission frequency stability of laser diodes, the ability of single-mode fiber cables to maintain polarization, and the availability of direct light amplifiers are found to be the most critical points, and recent theoretical and experimental results are reported. It is concluded from these very promising results that a heterodyne-type communication system using single-mode fibers at 1.6 μm may offer repeater spacings of over 200 km in the near future.
TL;DR: The effect of optical signal intensity at the wavelength of system operation on the recovery of the radiation-induced attenuation in optical fiber waveguides following exposure to a 3700-rad dose of ionizing radiation has been investigated.
Abstract: The effect of optical signal intensity at the wavelength of system operation (0.85 μm) on the recovery of the radiation-induced attenuation in optical fiber waveguides following exposure to a 3700-rad dose of ionizing radiation has been investigated. Photobleaching has been observed in both pure and doped silica core fibers, although the effect is more pronounced in the former.
TL;DR: A directional coupler using two single-mode fibers was designed showing a power extinction ratio from zero to more than 35 dB over a wide range of structure parameters with easy alignment operations and insertion loss lower than 1 dB.
Abstract: The core of a single-mode fiber can be reached by an optically controlled polishing technique which does not alter the fiber's mechanical strength. A directional coupler using two such fibers was designed showing a power extinction ratio from zero to more than 35 dB over a wide range of structure parameters with easy alignment operations and insertion loss lower than 1 dB.
TL;DR: In this article, an apparently undocumented loss mechanism in monomode fibers with germanium doped cores is demonstrated and the constraints on fiber design as a consequence of this loss mechanism are discussed.
Abstract: An apparently undocumented loss mechanism in monomode fibers with germanium doped cores is demonstrated. This loss increases as the fiber drawing temperature and/or the germanium concentration increases. By consideration of this mechanism in the fiber design and fabrication, losses lower than previously reported have been achieved both in fiber with low germanium concentration (0.38 dB/km at 1.3 μm) and in higher doped, dispersion shifted fiber (0.37 dB/km at 1.55μm). The constraints on fiber design as a consequence of this loss mechanism are discussed.
Patent•
18 Jun 1981
TL;DR: In this article, the authors proposed a method to carry out the high-speed spinning of an optical fiber having high reliability using a very simple apparatus in combination with a high speed spinning apparatus, by passing the optical fiber immediately after spinning through an inorganic raw material gas, thereby reacting the gas at the surface of the fiber taking advantage of the remaining heat of the fibre.
Abstract: PURPOSE: To carry out the high-speed spinning of an optical fiber having high reliability using a very simple apparatus in combination with a high-speed spinning apparatus, by passing an optical fiber immediately after spinning through an inorganic raw material gas, thereby reacting the gas at the surface of the fiber taking advantage of the remaining heat of the fiber. CONSTITUTION: He gas (carrier gas) 11 is bubbled in liquid TiCl 4 13 stored in the bubbler 12, and the TiCl 4 vapor 14 is blasted through the nozzle 15 to the surface of the optical fiber 18 having a definite diameter immediately after being spun from the optical fiber preform 17 with the spinning furnace 16. The vapor 14 is decomposed at the surface of the optical fiber by the remaining heat of spinning, oxidized to TiO 2 , and deposited to the surface of the fiber 18 to form a coating layer. The optical fiber 18 cooled by the endothermic reaction is passed through the die 2 containing the thermosetting resin 19 for coating. The resin 19 attached to the surface of the optical fiber 18 is baked, and cured in the furnace 21. COPYRIGHT: (C)1982,JPO&Japio
TL;DR: Various types of polarization eigenstates of a twisted birefringent fiber are discussed, and the resulting group delay difference is derived.
Abstract: Real single-mode fibers generally exhibit elliptical birefringence caused by deviations of the core shape from circularity, by transverse internal stress, and by residual twist. These three contributions can be individually determined by analyzing on a Poincare sphere the wavelength dependence of the output state of polarization of a short section of fiber with fixed input polarization. Various types of polarization eigenstates of a twisted birefringent fiber are discussed, and the resulting group delay difference is derived.
TL;DR: Highly accurate determination of the outer diameter of unclad glass fibers has been achieved by analyzing, at fixed scattering angle, the wavelength dependence of elastically scattered radiation.
Abstract: Highly accurate determination of the outer diameter of unclad glass fibers has been achieved by analyzing, at fixed scattering angle, the wavelength dependence of elastically scattered radiation. The positions of resonance peaks in the scattering spectrum are strongly dependent on fiber diameter. The linewidths of the peaks are sensitive to the circularity of the fiber cross section and to optical loss within or on the fiber surface. This new technique may be useful for the characterization of optical-communication fibers.
TL;DR: A Faraday circulator or isolator that uses a silica-core, single-mode, birefringent fiber as the active medium and small permanent magnets for the magnetic field is demonstrated.
Abstract: We demonstrate a Faraday circulator or isolator that uses a silica-core, single-mode, birefringent fiber as the active medium and small permanent magnets for the magnetic field. Circulators were constructed for wavelengths of 632.8 and 830 nm using about 2 m of fiber. This is the first description to our knowledge of such potentially useful working devices made in birefringent fiber. Bandwidth and temperature dependence were also investigated.
TL;DR: The efficient conversion of 1.06-μm radiation in a graded-index multimode optical fiber oscillator into a small number of spectral components propagating in specific modes of the fiber and falling in the spectral range spanning from the blue to 1.53 μm is reported.
Abstract: The efficient conversion of 1.06-μm radiation in a graded-index multimode optical fiber oscillator into a small number of spectral components propagating in specific modes of the fiber and falling in the spectral range spanning from the blue to 1.53 μm is reported. The effect is shown to result primarily from phase-matched four-photon mixing. The converted light is found to propagate as individual fiber modes which are identified. The wavelengths of the spectral components of the output of the oscillator are governed primarily by fiber geometry. Analysis of the results also indicates the presence and gives a measure of the fiber-core birefringence sensed by low-order modes of propagation of the graded-index multimode fibers we have studied. The efficiency of the oscillator source and the specific characteristic wavelengths available with common graded-index fibers suggest several possible applications, which are discussed.
Patent•
20 Nov 1981
TL;DR: In this paper, an optical fiber coupler is described for operatively coupling together two or more optical fibers, each coupler consists of several biconically tapered fibers and the biconical sections of each fiber are placed side by side or twisted around one another.
Abstract: An optical fiber coupler is described for operatively coupling together two or more optical fibers. Each coupler consists of several biconically tapered fibers. The biconical sections of each fiber are placed side by side or twisted around one another, and fused together. The couplers are typically made of optical fibers having a diameter in the range from about 100 to about 300 microns. The fiber comprises a core of glass having a high index of refraction and cladding of glass with a low index of refraction. The cladding of each biconical section has been reduced by chemical etching, plasma etching, ion-milling, abrasion or the like, to a thickness not exceeding 25 percent of the core diameter, more preferably less than 10 percent and most preferably from about 5 percent to about 10 percent of the core diameter. The couplers are of step or graded index optical fiber. The design can be adapted as multiport access couplers when more than two fibers are involved. The reduction of cladding thickness is essential to produce optical fiber couplers with a coupling coefficient of about 40 percent and an average loss of about 10 percent.
TL;DR: In this paper, a successful trial production of a 0.2 dB/km single-mode fiber (1.55 μm) by the MCVD method, a study on glass compositions of such very low-loss singlemode fiber suitable for mass production and a study of zero-dispersion fiber at the 1.5μm band are described.
Abstract: This paper introduces the recent development of single-mode optical fiber in Japan, with emphasis laid on experimental studies. A successful trial production of a 0.2 dB/km single-mode fiber (1.55 μm) by the MCVD method, a study on glass compositions of such very low-loss single-mode fiber suitable for mass production and a study of zero-dispersion fiber at the 1.5μm band are described. The paper further contains news about the success in trial manufacture of a continuous 100 km long single-mode fiber by the VAD method and gives a brief description of single-mode fiber splicing, centering on a fusion method, now under development.
TL;DR: The shape of a new type of low birefringence spun fiber, made by rapidly spinning a near circular preform in the pulling oven, was measured and a small ellipticity which rotated helically along the fiber was observed.
Abstract: A new, highly precise, optical fiber outer diameter measuring technique based on near-field resonant backscattered light is described. Relative accuracies of ±10−2μm were achieved in diameter measurements using Fabry-Perot resonances and ±10−3μm in average diameter measurements using dielectric surface-wave resonances for ∼100-μm fibers. The shape of a new type of low birefringence spun fiber, made by rapidly spinning a near circular preform in the pulling oven, was measured. We observed a small ellipticity which rotated helically along the fiber. The possibility of making absolute and real-time outer diameter measurements is discussed.
TL;DR: In this article, a 1.6 μm long wavelength semiconductor CW BH laser, low-loss single-mode optical fiber with a loss of 0.2 dB/km, and two thin z-cut LiNbO 3 modulators tilted 45° relative to each other was demonstrated by an electrooptical and electrical feedback system.
Abstract: Polarization control of the light output from single-mode fiber systems is very important in order to connect it to polarization-dependent integrated optical circuits and applications using a heretodyne detection system. In this paper, automatic control of the polarization of light transmitted through the fiber was demonstrated by an electrooptical and electrical feedback system. In this system, we used a 1.6 μm long wavelength semiconductor CW BH laser, low-loss single-mode optical fiber with a loss of 0.2 dB/km, and two thin z -cut LiNbO 3 modulators tilted 45° relative to each other. The output light from this polarization controller was maintained to be linear while that from the single-mode fiber was unstable and elliptically polarized.
TL;DR: In this paper, the authors examined the performance of fused silica optical fibers with a view toward use in fiber-coupled spectrographs and found that the smaller fibers yielded better performance with respect to focal ratio preservation.
Abstract: Fused silica optical fibers were examined with a view toward use in fiber-coupled spectrographs. The emphasis of the investigation was on how well the input focal ratio was preserved during transmission down a long fiber. The best overall performance was given by the Galite 4000 series and the Maxlight 150 micron fibers. The Valtec products also yielded good results when cabled so that stress could not be easily induced. It was found that the smaller fibers yielded better performance with respect to focal ratio preservation.
TL;DR: A method is described for the nondestructive determination of the state of polarization of the guided light at an arbitrary point along a single-mode fiber using elasto-optic polarization modulation.
Abstract: A method is described for the nondestructive determination of the state of polarization of the guided light at an arbitrary point along a single-mode fiber. The fiber is squeezed laterally with a small, periodic (75-Hz) force. The azimuth of the force is varied. The resulting elasto-optic polarization modulation is detected at the fiber end and is evaluated for the azimuth and ellipticity of the polarization at the point of modulation.
Patent•
04 Nov 1981
TL;DR: In this article, a length of optical fiber is jacketed with or attached to piezoelectric material that is poled perpendicular to the length of the fiber, resulting in a shift in the optical phase.
Abstract: The invention relates to a technique for detecting electric fields by modulating the phase of an optical beam. A length of optical fiber is jacketed with or attached to piezoelectric material that is poled perpendicular to the length of the fiber. An electric field is applied across the piezoelectric element, i.e. in the direction of poling, resulting in a change in the element thickness and a change in the axial dimension, which, in turn, changes the length of the optical fiber. The change in fiber length is accompanied by a smaller change in the refractive index of the fiber. The result is a shift in the optical phase.
TL;DR: In this paper, the effects of light signals propagating within a fiber optic waveguide on the magnitude, spectral character and stability of radiation-induced optical absorption have been investigated for typical state-of-the-art optical fibers.
Abstract: The effects of light signals propagating within a fiber optic waveguide on the magnitude, spectral character and stability of radiation-induced optical absorption have been investigated. In particular, the prospects for the utilization of photobleaching techniques to increase the radiation hardness of fiber optic links has been assessed for typical state-of-the-art optical fibers. Both steady state and pulsed light sources have been employed. Fibers fabricated both from high purity synthetic silica and selectively doped silicas have been utilized. The nature of the photo-bleaching process in silica-based glasses is discussed and the characteristics of the photoluminescence accompanying the bleaching process are reported. It is concluded that the selective use of optical bleaching in irradiated fiber optic waveguides provides a useful method for increasing the operational hardness of a data link. This can be accomplished at modest power levels achievable with present day solid state light sources, and the system can be configured such that the transmitted and bleach signals are identical. The technique is most effective in pure silica core materials and promises to primarily impact systems with modest length requirements in which high light intensities can be launched throughout the link. Second generation waveguides with lower intrinsic losses will make the photobleaching approach useful even for extended ranges. The possibility of self-photobleaching waveguides containing luminescent ions is also discussed.