Showing papers on "Single-mode optical fiber published in 1980"
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TL;DR: In a bent optical fiber, lateral internal stress induces a birefringence, betab, where r is the fiber radius and R is the bending radius.
Abstract: In a bent optical fiber, lateral internal stress induces a birefringence, betab. At lambda = 0.633 microm in a silica fiber, betab = 7.7 X 10(7) r2 /R2 deg/m, where r is the fiber radius and R is the bending radius.
543 citations
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TL;DR: In this article, the authors describe new single-mode fiber optic devices which are completely equivalent to fractional wave plates of classical optics and employ a very simple configuration which uses the stress birefringence induced by bending the fibre.
Abstract: We describe new single-mode fibre optic devices which are completely equivalent to fractional wave plates of classical optics. They employ a very simple configuration which uses the stress birefringence induced by bending the fibre. Several devices can be combined to control the polarisation inside any single-mode fibre.
541 citations
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TL;DR: The feasibility of maintaining a single-mode optical fiber interferometer in quadrature is demonstrated using a servo driven piezoelectrically stretched coiled fiber with stress voltage coefficient of ~27pi rad/V.
Abstract: The feasibility of maintaining a single-mode optical fiber interferometer in quadrature is demonstrated using a servo driven piezoelectrically stretched coiled fiber. The controller has a range of ~10(-5)-1000 rad with a stress voltage coefficient of ~27pi rad/V.
461 citations
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TL;DR: The spectral analysis is made highly accurate by the use of line-shape fitting techniques and mode group delays can be determined to a precision of +/-0.12 psec/km using a computation covering a 5-cm propagation path.
Abstract: Propagating beam solutions for optical waveguides can be made to generate such mode-related properties as propagation constants, relative mode powers, and group delays with high precision and considerable flexibility. These quantities are needed in the analysis of optical fiber dispersion. The technique requires the generation of correlation functions from the numerical solutions of a wave equation. These correlation functions are in turn Fourier-transformed with respect to axial distance z. The resulting spectra display sharp resonances corresponding to mode groups, and the positions and heights of these resonances determine the previously mentioned mode properties. The spectral analysis is made highly accurate by the use of line-shape fitting techniques. With this method, mode group delays can be determined to a precision of +/-0.12 psec/km using a computation covering a 5-cm propagation path.
319 citations
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TL;DR: In this article, a tunable coherent infrared (IR) source is presented, which utilizes the sideband produced by modulational instability of an optical signal in a fiber which results from a combination of anomalous dispersion and the nonlinear Kerr effect.
Abstract: A new tunable coherent infrared (IR) source is presented. It utilizes the sideband produced by modulational instability of an optical signal in a fiber which results from a combination of anomalous dispersion and the nonlinear Kerr effect. The generated frequency is in proportion to the square root of the optical pump signal. A coherent IR signal is generated by extracting the sideband.
275 citations
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29 Jul 1980
TL;DR: In this article, a method and apparatus for high speed multiaccess data communication using guided wave components and angular division multiplexing for parallel optical signal transmission over a multimode optical fiber is described.
Abstract: A method and apparatus are disclosed for high speed multiaccess data communication using guided wave components and angular division multiplexing for parallel optical signal transmission over a multimode optical fiber. A receiver at each station in the network comprises an optical coupler/demultiplexer, a pulse regenerator, an optical processor and detectors. The transmitter at each station comprises an array of lasers, a switching matrix for controlling emissions into the optical fiber and a multiplexer/coupler for coupling the laser emissions to the multimode optical fiber. The optical processor is directly coupled to the switching matrix. Preferably, the multiplexer/coupler comprises a graded-index planar lens, one major surface of which abuts the optical fiber and the other major surface of which is contacted by a plurality of single mode waveguides from the different lasers of the transmitter. As a result, the single mode signals introduced into the lens at different radial distances are coupled to different modal groups propagating in the optical fiber. The coupler/demultiplexer preferably comprises a graded-index lens and an array of concentric half-ring lasers. Annular cones of radiation propagating in the optical fiber are focused to an array of concentric rings near the half-ring lasers where they are converted into linear beams propagating in single mode guided wave structures.
199 citations
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TL;DR: Both effects of Bend-induced retardation and twist-induced rotation in single-mode optical fibers were found highly reproducible and to have small temperature dependence.
Abstract: Bend-induced retardation and twist-induced rotation in single-mode optical fibers are important variables in the design of optical fiber current measurement systems. Bend-induced retardation varies with the square of the curvature and is believed caused by a waveguide geometry effect. Twist-induced rotation varies with the angle through which the fiber is twisted and is produced by torsional strain in the fiber. Both effects were found highly reproducible and to have small temperature dependence. Neither effect should significantly limit the performance of optical measurement systems using single-mode fibers.
192 citations
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TL;DR: A simple optical-pulse-equalization technique for minimizing pulse dispersion in a single-mode fiber transmission system utilizing the positive- and the negative-dispersion characteristics of single- mode fibers on both sides of a zero-chromatic-disPersion wavelength is described.
Abstract: We describe a simple optical-pulse-equalization technique for minimizing pulse dispersion in a single-mode fiber transmission system utilizing the positive- and the negative-dispersion characteristics of single-mode fibers on both sides of a zero-chromatic-dispersion wavelength.
186 citations
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TL;DR: Periodic phase changes in the 10(-6) -rad region have been induced and detected in a single-mode all-fiber Mach- Zehnder interferometer by stretching the fiber with a piezoelectric cylinder driven at frequencies between 40 and 10(4) Hz.
Abstract: Periodic phase changes in the 10(-6) -rad region have been induced and detected in a single-mode all-fiber Mach- Zehnder interferometer by stretching the fiber with a piezoelectric cylinder driven at frequencies between 40 and 10(4) Hz.
182 citations
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TL;DR: In this paper, the theory of backscattering was extended to single-mode fibers, and the result of the present investigation is nearly the same as for multimode fibers although the theory in the latter case is based on a ray optical approach.
Abstract: The theory of the backscattering method, which so far has been known only for multimode fibers, is extended to single-mode fibers. Under certain conditions the result of the present investigation is nearly the same as for multimode fibers although the theory in the latter case is based on a ray optical approach.
165 citations
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TL;DR: A technique is presented for the fabrication of high-quality single-mode fiber-optic polarizers that include extinction ratios in excess of 60 dB as well as low loss for the desired polarization.
Abstract: A technique is presented for the fabrication of high-quality single-mode fiber-optic polarizers. Properties of polarizers made using this technique include extinction ratios in excess of 60 dB as well as low loss for the desired polarization.
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TL;DR: It is experimentally clarified that the intensity in each longitudinal mode of a laser diode fluctuates, although the intensity for the total mode is constant, and this fluctuation causes degradation of the error rates after transmission through a long optical fiber.
Abstract: An evaluation of the influence of mode partition noise on error rate performance in a high bit rate optical fiber transmission system is presented. First, it is experimentally clarified that the intensity in each longitudinal mode of a laser diode fluctuates, although the intensity for the total mode is constant. It is also established that this fluctuation causes degradation of the error rate performance after transmission through a long optical fiber. The fluctuation is named "mode partition noise." Next a simple model for the fluctuation is proposed. The characteristics of the fluctuation are discussed on the basis of this model. Optical waveform fluctuation is found to be introduced by mode partition noise in the course of transmission through a long despersive transmission medium. This optical waveform fluctuation and its frequency spectrum are calculated. Finally, the error rate performance is evaluated and specifications required for a laser spectrum to attain a given repeater spacing are clarified.
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TL;DR: Polarization beat lengths down to 2.5 cm have been realized this way, providing excellent polarization holding.
Abstract: Coiling a single-mode fiber of radius r under tension onto a cylinder of radius R produces a linear birefringence of βtc ≃ 28 × 107∊2r/R deg/m in the fiber at λ = 0.63 μm, where ∊z is the relative fiber elongation. Polarization beat lengths down to 2.5 cm have been realized this way, providing excellent polarization holding.
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TL;DR: In this article, a hemispherical microlens is fabricated on the end of a single-mode fiber by an electric arc discharge technique, which improves coupling efficiency between InGaAsP lasers with buried heterostructure geometry and singlemode fiber.
Abstract: A hemispherical microlens is fabricated on the end of a single-mode fiber by an electric arc discharge technique. It improves coupling efficiency between InGaAsP lasers with buried heterostructure geometry and single-mode fiber. The lowest coupling loss of 2.9 dB is achieved with the optimum lens radius of 8.5 μm. This loss is 4.4 dB lower than that with a butt joint. Experimental results of coupling efficiency and alignment tolerances in coupling with different lens radii in the range of 3.5-17 \mu m are discussed in detail. The results are in good agreement with theoretical values derived by Gaussian beam and paraxial ray approximations.
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CNET1
TL;DR: In this paper, the polarization state evolution of light propagating in long, birefringent, single-mode fibres in the presence of mode coupling was studied and the applicability of coupled power equations was discussed and it was shown that they cannot be used with only two propagating modes.
Abstract: In this paper we look at the polarization state evolution of light propagating in long, birefringent, single-mode fibres in the presence of mode coupling. We show first that there always exist two orthogonal linear input polarizations which lead to linear output polarization for monochromatic light. The applicability of the coupled power equations is discussed and it is shown that they cannot be used with only two propagating modes. A more detailed analysis is then carried out for a uniform coupling and the effect of the spectral width of the source is investigated. Some insight into the time-dependent propagation is also given. Experimental results illustrate the theoretical considerations.
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TL;DR: In this article, a new refractive-index distribution for realising a single-polarization single-mode optical fiber is proposed, which features two pits, on either side of the core.
Abstract: A new refractive-index distribution for realising a single-polarisation single-mode optical fibre is proposed. This distribution features two pits, on either side of the core. The propagation characteristics are calculated by the two-dimensional finite-element method. The relative birefringence δβ/βav is 1 ∼ 2.5 × 10−4 when core/cladding index difference is 1%.
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TL;DR: In this paper, the scattering process in single-mode optical fibres is considered in terms of wave optics rather than geometrical optics, which is inadequate in this case, and the result for the backscattering signal at the input end of the fibre is nearly the same as for multimode fibres.
Abstract: The scattering process in single-mode optical fibres is considered in terms of wave optics rather than geometrical optics, which is inadequate in this case. Surprisingly, however, the result for the backscattering signal at the input end of the fibre is nearly the same as for multimode fibres.
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04 Oct 1980TL;DR: In this article, the diameter of a single mode optical fiber is determined based on the difference between refractive indices n and n2 of the core and cladding, and the diameter is determined according to this value.
Abstract: In a single mode optical fiber comprising a core made of glass and a cladding surrounding the core and made of glass, when a difference A between refractive indices n. and n2 of the core and cladding is expressed by the refractive indices n, and n2 are determined to satisfy a relation 1.0 < A < 3.6 and a diameter of the core is determined according to this value of A. When the refractive index difference A and the diameter of the core are determined in this manner, the optical fiber would have a wider band transmission characteristics than the prior art optical fiber, thus enabling higher degree of wavelength multiplexing.
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TL;DR: In this paper, the difference between propagation constants of two polarization modes caused by elliptical core deformation and stress anisotropy was given for single-mode optical fibers subject to an externally applied uniaxial pressure.
Abstract: A formula for the difference between propagation constants of two polarization modes caused by elliptical core deformation and stress anisotropy is given for single-mode optical fibers. Birefringence in circular and elliptical core fibers subject to an externally applied uniaxial pressure are measured. Birefringence caused by elliptical core deformation and stress anisotropy are experimentally separated by measuring their wavelength dependences. A value of 3.36 \times 10^{-10} cm2/gram weight (gw) (= 3.43 \times 10^{-12} m2/N) is obtained for the stress-optical constant of silica fibers. Residual stress corresponding to external pressure of 240 gw/cm is observed for a fiber with 0.35 core ellipticity.
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TL;DR: The generation of modal noise caused by the random interference of fiber modes in the presence of a mode-selective loss is described theoretically and confirmed experimentally and the results permit quantitative prediction ofmodal noise in optical systems.
Abstract: The generation of modal noise caused by the random interference of fiber modes in the presence of a mode-selective loss is described theoretically and confirmed experimentally. The results permit quantitative prediction of modal noise in optical systems.
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TL;DR: In this paper, the authors investigated mode coupling coefficients and impulse responses in a multimode graded-index fiber, both experimentally and theoretically, and found that the mode coupling coefficient change due to nylon coating is relatively small.
Abstract: Mode coupling coefficients and impulse responses in a multimode graded-index fiber are investigated both experimentally and theoretically. Mode coupling coefficient measurements at 1.27 μm are made for a fiber before and after nylon coating. The fiber is 10 km in length and has no splicing point. The mode coupling coefficient change due to nylon coating is found to be relatively small. In the nylon-coated fiber, the coefficient increases monotonically as increasing a principal mode number, and the tendency is in good agreement with the theoretical prediction considering random bends along the fiber axis. With the increase in mode coupling coefficient and 0.01 dB/km of excess loss by nylon coating, 2.7 percent of increase in 3-dB bandwidth is observed. This increase in 3-dB bandwidth is explained by the theoretical calculation. The length dependence of 3-dB bandwidth exhibits a small mode mixing effect in the fiber. By the theoretical predictions based on the experimental mode coupling coefficients, the coupling length is estimated to be 25 km. It is also clarified that the length dependence of 3-dB bandwidth shows the L-0.5characteristic for L > 200 km.
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23 Jul 1980
TL;DR: In this paper, a 3dB optical directional coupler is used to split a laser beam into two beams which in turn are launched into single mode optical fibers of different lengths, and a phase difference is produced between the beams transmitted through the optical fibers.
Abstract: In an optical sensing system a laser beam is split by a 3dB optical directional coupler into two beams which in turn are launched into single mode optical fibers of different lengths. Since the two single mode optical fibers are maintained at the temperature to be measured, a phase difference is produced between the beams transmitted through the optical fibers. The beams passing through the optical fibers are synthesized by the 3dB optical directional coupler to form an interference pattern comprised of "light" and "dark" regions. The wavelength of the light beam is monotonically varied over a predetermined range so as to cause these regions to vary in position. This variation in position is manifested at a given point in the interference pattern as a variation in signal amplitude, and this variation in signal amplitude is detected to infer the temperature to be measured.
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TL;DR: In this paper, a low-loss single-mode fiber pumped with a 1.3?m Q-switched Nd:y.a. laser was used to generate new waves at multiple wavelengths with total spectral range extended as wide as 660 cm.
Abstract: In a low-loss single-mode fibre pumped with a 1.3 ?m Q-switched Nd:y.a.g. laser, an injected weak (~ 1 mW) signal has been strongly amplified and mixed efficiently with the pump (~ 70 W) to generate new waves (?1 W) at multiple wavelengths with total spectral range extended as wide as 660 cm?1.
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TL;DR: Elastic and elastooptic coefficients used to predict acoustic response sensitivity for two single-mode optical fibers have been determined from Brillouin scattering measurements, finding that this assumption introduces no more than a 5% error in the pressure sensitivity for a low numerical aperture (N.A.) fiber.
Abstract: Elastic and elastooptic coefficients used to predict acoustic response sensitivity for two single-mode optical fibers have been determined from Brillouin scattering measurements. These measurements were made on two ITT single-mode fiber preforms currently of interest in the fabrication of fiber-optic acoustic sensors. Previous predictions of acoustic sensitivity assumed the optical fiber waveguides as homogeneous fused silica cylinders. It was found that this assumption introduces no more than a 5% error in the pressure sensitivity for a low numerical aperture (N.A.) fiber and a 30% error for a high N.A. fiber.
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TL;DR: The method makes it possible to characterize a fiber from a simple measurement of the HE(11) mode spot size without making difficult index profile and core radius measurements, and it is found that the step-index distribution is suitable for single-mode fibers.
Abstract: A method is proposed whereby the propagation characteristics of a single-mode fiber having an arbitrary refractive-index profile may be expressed in terms of a newly defined equivalent step-index profile. The theory is based on the fact that the field distribution of the HE11 mode of a fiber closely resembles the Gaussian profile. The method makes it possible to characterize a fiber from a simple measurement of the HE11 mode spot size without making difficult index profile and core radius measurements. It is also found that the step-index distribution is suitable for single-mode fibers.
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TL;DR: A new method for producing microlenses on the ends of single-mode optical fibers by dipping the fiber end into a negative photoresist while the fiber core carries greater, similar0.1 mW of He-Ne laser light.
Abstract: A new method has been devised for producing microlenses on the ends of single-mode optical fibers. A lens is formed by dipping the fiber end into a negative photoresist while the fiber core carries ≳0.1 mW of He–Ne laser light. The photoresist lenses require no developing or rinsing. The lenses are shown to transform the near-Gaussian beam emitted by the fiber into another near-Gaussian beam with a reduced waist diameter. The size of the new waist can be selected by varying the number of times the fiber is dipped into the photoresist. The waist reduction is shown to increase coupling into single-mode optical waveguides.
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20 Mar 1980
TL;DR: In this article, a fiber optic energy sensor and optical demodulation system is described where the signal energy to be sensed or detected causes an etched single mode fiber to be stretched or compressed which causes the optical path length for electromagnetic radiation traveling in the core of the optic fiber to change.
Abstract: A fiber optic energy sensor and optical demodulation system is disclosed wherein the signal energy to be sensed or detected causes an etched single mode fiber to be stretched or compressed which causes the optical path length for electromagnetic radiation traveling in the core of the optic fiber to change. The change in optic path length modulates the electromagnetic radiation traveling in the fiber. There is also disclosed novel methods of manufacturing the novel type of fiber optic energy sensor and optical demodulation system.
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TL;DR: In this paper, a body of birefringent material is mounted in the area in which the material has been removed in close proximity to the core of the fiber, which modifies the propagation of two polarization modes within the fiber in such manner that one of the modes is coupled to a bulk wave mode and removed from the guide, while the second mode excites no bulk waves and remains guided.
Abstract: Apparatus and method for changing the degree of polarization of light in a waveguide such as an optical fiber. A portion of the cladding of a strand of fiber optic material is removed, and a body of birefringent material is mounted in the area in which the material has been removed in close proximity to the core of the fiber. The birefringent material modifies the propagation of two polarization modes within the fiber in such manner that one of the modes is coupled to a bulk wave mode and removed from the guide, while the second mode excites no bulk waves and remains guided.
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TL;DR: A new method is proposed for the determination of the spot size of a monomode fiber based on the theory of splice losses and involving measurements of the transmitted power as a function of misalignments of the fiber axes.
Abstract: A new method is proposed for the determination of the spot size of a monomode fiber based on the theory of splice losses and involving measurements of the transmitted power as a function of misalignments of the fiber axes.
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TL;DR: In this paper, the output light of a singlemode optical fiber was controlled and stabilised by an electro-optical feedback system consisting of two LiNbO3 crystals and voltage controllers.
Abstract: The polarisation of the output light of a single-mode optical fibre was controlled and stabilised by an electro-optical feedback system consisting of two LiNbO3 crystals and voltage controllers. Using this system, polarisation mismatching loss was reduced to 0.2 dB.