Showing papers on "Optical fiber published in 1991"
TL;DR: Erbium-doped fiber amplifiers are modeled using the propagation and rate equations of a homogeneous two-level laser medium, and numerical methods are used to analyze the effects of optical modes and erbium confinement on amplifier performance.
Abstract: Erbium-doped fiber amplifiers are modeled using the propagation and rate equations of a homogeneous two-level laser medium. Numerical methods are used to analyze the effects of optical modes and erbium confinement on amplifier performance, and to calculate both the gain and amplified spontaneous emission (ASE) spectra. Fibers with confined erbium doping are completely characterized from easily measured parameters: the ratio of the linear ion density to fluorescence lifetime, and the absorption of gain spectra. Analytical techniques then allow accurate evaluation of gain, saturation, and noise in low-gain amplifiers (G >
1,157 citations
TL;DR: In this paper, material-dependent properties influencing the performance of fiber amplifiers are reviewed together with the available data for Er/sup 3+/. The major glass types potentially useful in this application are considered and compared to silica.
Abstract: Material-dependent properties influencing the performance of fiber amplifiers are reviewed together with the available data for Er/sup 3+/. The major glass types potentially useful in this application are considered and compared to silica. The topics addressed include quenching processes and the solubility of rare-earth ions, transition strengths and bandwidths at the 1500-nm gain transition, and the characteristics at the 800-, 980-, and 1480-nm pump bands. Aluminum is shown to be an extremely useful codopant for silica, improving its ability to dissolve rare-earth ions and providing desirable spectroscopic properties for Er/sup 3+/. For some of the attributes considered, other glasses have advantages over Al silica, but only with respect to gain bandwidth and pumping performance at 800 nm is significantly better than expected from other glass compositions. >
871 citations
TL;DR: It is demonstrated the operation of a quadrature phase-shifted extrinsic Fabry-Perot fiber-optic sensor for the detection of the amplitude and the relative polarity of dynamically varying strain.
Abstract: We demonstrate the operation of a quadrature phase-shifted extrinsic Fabry–Perot fiber-optic sensor for the detection of the amplitude and the relative polarity of dynamically varying strain. Two laterally displaced single-mode fibers inserted within a hollow silica tube form the 90° phase-shifted sensing system. A multimode fiber, placed in the tube facing the two fibers, acts as a reflector, thereby creating an air gap that acts as a Fabry–Perot cavity. A theoretical description of the sensor is given, and its operation as a dynamically varying strain sensor is described. Strain sensitivities of 5.54° phase shift/microstrain cm−1 are obtained.
483 citations
01 Oct 1991
TL;DR: In this article, two complementary delineation criteria are presented which provide guidelines to the design of relatively short, low-loss tapered fibres and devices, which are used to explain anomalous loss effects in depressed-cladding and W-fibres, as well as the difficulty in fabricating low loss devices by tapering such fibres.
Abstract: Two complementary delineation criteria are presented which provide guidelines to the design of relatively short, low-loss tapered fibres and devices. They are used to explain anomalous loss effects in depressed-cladding and W-fibres, as well as the difficulty in fabricating low-loss devices by tapering such fibres. Practical application of the criteria to couplers, beam expanders and abrupt taper filters is summarised. The accompanying paper provides both experimental and theoretical justification for the delineation criteria.
447 citations
TL;DR: An amplifying nonlinear-optical fiber loop mirror is used as the gain element in an all-fiber ring laser, and the resulting double-loop structure resembles a figure eight.
Abstract: An amplifying nonlinear-optical fiber loop mirror is used as the gain element in an all-fiber ring laser. The resulting double-loop structure resembles a figure eight. The output of the amplifying nonlinear-optical fiber loop mirror is fed back to the input through an optical isolator to ensure unidirectional operation. The laser produces 2-ps transform-limited pulses. The pulse energy corresponds to that of the fundamental soliton in the fiber used.
367 citations
TL;DR: Cross-phase and self-phase modulation are used for self-sustained mode locking of a high-power neodymium glass fiber laser.
Abstract: Cross-phase and self-phase modulation are used for self-sustained mode locking of a high-power neodymium glass fiber laser. Stable pulses with a FWHM as short as 70 fs and pulse energies of as much as 1 nJ are generated at a wavelength of 1.064 microm.
340 citations
Journal Article•
TL;DR: In this article, the authors report on a large amount of work that reaches beyond simple glasses such as silica, and discuss recently discovered photoinduced effects in glass fibres, which include second harmonic generation and the formation of refractive index gratings.
Abstract: Nonlinear properties include intensity-dependent refractive index, multiphoton absorption, second and third harmonic generation, stimulated Raman and Brillouin scattering, and associated phenomena such as self-focusing, self-phase modulation, optical phase conjugation, and optical bistability. We report on a large amount of work that reaches beyond simple glasses such as silica. Nonlinear optical phenomena have been investigated in materials ranging from oxide, halide, and chalcogenide glasses to glasses doped with semiconductor microcrystals, organic dyes, and metal particles and in forms varying from bulk materials to optical fibres and waveguides. We also discuss recently discovered photoinduced effects in glass fibres, which include second harmonic generation and the formation of refractive index gratings
329 citations
TL;DR: In this article, a nonlinear amplifying loop mirror was converted into a laser by feedback of the output to the input through a fiber-pigtailed optical isolator, and the pump powers were low enough that laser diodes could be used for pumping.
Abstract: A nonlinear amplifying loop mirror has been turned into a laser by feedback of the output to the input through a fibre-pigtailed optical isolator. After some optimisation, pulses as short as 314 fs were produced. The pump powers are low enough that laser diodes could be used for pumping.
320 citations
TL;DR: In this article, the authors analyzed the signal propagation and noise accumulation in lightwave systems using saturated optical amplifiers as repeaters and showed that a reach beyond 10000 km is possible with a 1.55-mu m system in the absence of fiber nonlinearities.
Abstract: Signal propagation and noise accumulation in lightwave systems using saturated optical amplifiers as repeaters are analyzed. Numerical simulations of amplified spontaneous emission in concatenated erbium-doped fiber amplifiers indicate that a reach beyond 10000 km is possible with a 1.55- mu m system in the absence of fiber nonlinearities. Distributed optical amplifiers are shown to have low noise, but require higher pump power than lumped amplifiers. Three operating modes of an amplifier lightwave system are identified and their relative signal power efficiency and noise performance are described. >
285 citations
Patent•
17 Jan 1991
TL;DR: Adaptive racking and distribution frame systems for handling optical fiber cables and including racking sections with wall portions that can be replaced without removing the section or displacing cables in the section as discussed by the authors.
Abstract: Adaptive racking and distribution frame systems for handling optical fiber cables and including racking sections with wall portions that can be replaced without removing the section or displacing cables in the section and further including housings with moveable shelves that can be adapted to hold optical fiber splices, optical fiber connectors or optical fiber storage spools.
Patent•
29 Jul 1991TL;DR: In this article, a backscattered light in response to receiving the coherent light pulses is produced and coupled into an optical receiving fiber, which is detected by a photodetector.
Abstract: Apparatus for sensing intrusion into a predefined perimeter comprises means for producing a coherent pulsed light, which is injected into an optical sensing fiber having a first predetermined length and positioned along the predefined perimeter. A backscattered light in response to receiving the coherent light pulses is produced and coupled into an optical receiving fiber. The backscattered light is detected by a photodetector and a signal indicative of the backscattered light is produced. An intrusion is detectable from the produced signal as indicated by a change in the backscattered light. To increase the sensitivity of the apparatus, a reference fiber and an interferometer may also be employed.
TL;DR: In this article, a method for measuring submicrometer distances with an asymmetric fiber Michelson interferometer having an LED as a source of radiation is described, which is compatible with time domain sampling at the Nyquist rate.
Abstract: We describe a method for measuring submicrometer distances with an asymmetric fiber Michelson interferometer having an LED as a source of radiation. By measuring the phase slope of the Fourier components in the frequency domain, it is possible to locate the position of reflections with nanometer precision even in the presence of sample dispersion. The method is compatible with time domain sampling at the Nyquist rate which assures efficiency in data acquisition and processing.
TL;DR: In this paper, it was shown both analytically and by numerical simulation that solitons can traverse great distances through a chain of lumped amplifiers connecting dispersion shifted fiber spans, and the resultant pulse distortions and dispersive wave radiation tend to be negligible, as long as the length scale of the variations in energy and dispersion are short relative to the soliton period.
Abstract: It is shown both analytically and by numerical simulation, that solitons can traverse great distances through a chain of lumped amplifiers connecting dispersion shifted fiber spans. The fiber spans can also have large fractional variations in D. The resultant pulse distortions and dispersive wave radiation tend to be negligible, as long as the length scale of the variations in energy and dispersion are short relative to the soliton period. >
TL;DR: In this article, the current status of fabrication methods, matching particular fibers for specific applications, together with optimizing the fiber for high efficiency, are presented, along with the current state of the art in fiber selection and fabrication.
Abstract: Erbium-doped fiber has become the central component of nearly all optical amplifiers. Applications reported include repeaters, power amplifiers, preamplifiers, and distributed amplifiers. To date, nearly all the fiber used in these devices has been silica based and fabricated by variations on the major telecommunications fiber technology. Disadvantages of the silica-based host glass, such as low solubility of the rare-earth ions and narrowband fluorescence, have been carefully addressed and solutions have been found to overcome these potential drawbacks. Details of the current status of fabrication methods, matching particular fibers for specific applications, together with optimizing the fiber for high efficiency, are presented. >
TL;DR: This work proposes what is to their knowledge the first use of a Pr(3+)-doped fluoride fiber amplifier as a practical amplifier operating at the 1.3-microm band, based on a demonstration of signal amplification and a spectroscopic investigation.
Abstract: We propose what is to our knowledge the first use of a Pr3+-doped fluoride fiber amplifier as a practical amplifier operating at the 1.3-μm band, based on a demonstration of signal amplification and a spectroscopic investigation. The feasibility of the fluoride fiber amplifier is confirmed.
Journal Article•
TL;DR: In this article, an accurate model for the erbium-doped fiber amplifier is presented, which is used to design the index profile of the doped fiber, optimizing with regard to efficiency for inline-and preamplifiers as well as for power booster amplifiers.
Abstract: An accurate model for the erbium-doped fiber amplifier is presented. The model is used to design the index profile of the doped fiber, optimizing with regard to efficiency for inline- and preamplifiers as well as for power booster amplifiers. The predicted pump efficiencies (maximum gain to pump power ratios) are in agreement with experimental results presented in the literature. The choice of codopant is shown to be very significant for the pump efficiency when pumping in the 0.98 mu m. The pump efficiency in the 0.98- mu m pump band is shown to be twice the pump efficiency in the 1.48- mu m pump band. >
TL;DR: In this paper, a method for the generation of high-quality soliton trains at a high repetition rate of gigahertz to tera-hertz range was presented, where a train of practically noninteracting fundamental solitons is formed.
Abstract: The authors present a method for the generation of high-quality soliton trains at a high repetition rate of gigahertz to terahertz range During nonlinear propagation of a continuous-wave (CW) dual-frequency signal through a fiber with effective amplification, a train of practically noninteracting fundamental solitons is formed It is shown that the effective amplification can be achieved as in usual fibers with an actual amplification as well as in fibers with nonuniform parameters along the fiber axis The method is demonstrated experimentally Dual-frequency 25 ps pulses at lambda =155 mu m are reshaped into 02 THz combs of 049 ps solitons in fiber with slowly decreasing dispersion It is also shown that stimulated Brillouin scattering (SBS) can prevent a CW soliton train transmission through optical fibers, and suggests a method for suppression of SBS >
Patent•
25 Jan 1991TL;DR: In this paper, a unique fiber optic sensor which is able to conduct multiple assays and analysis concurrently using a plurality of different dyes immobilized at individual spatial positions on the surface of the sensor is presented.
Abstract: The present invention provides a unique fiber optic sensor which is able to conduct multiple assays and analysis concurrently using a plurality of different dyes immobilized at individual spatial positions on the surface of the sensor. The present invention also provides apparatus for making precise optical determinations and measurements for multiple analytes of interest concurrently and provides methods of detection for multiple analytes of interest which can be correlated with specific parameters or other ligands for specific applications and purposes.
TL;DR: In this paper, the effect of weak refractive-index nonlinearity of optical fibers on pulse shape was investigated using computer simulations of long-distance transmission and the analysis was confined to normal pulses and does not consider solitons.
Abstract: The effect of the weak refractive-index nonlinearity of optical fibers on pulse shape is investigated using computer simulations of long-distance transmission. Fiber losses are canceled by periodically spaced optical amplifiers whose spontaneous emission noise is, however, not included in the simulations. The analysis is confined to normal pulses and does not consider solitons. Several conclusions are drawn. (1) If wavelength division multiplexing (WDM) of two channels is used in a uniform fiber without dispersion fluctuations, catastrophic buildup of four-wave mixing occurs if one primary channel is located at the zero-dispersion wavelength. (2) If two pulses with different carrier frequencies collide in a uniform fiber with no gain or loss discontinuities, their four-wave mixing products reach a peak during complete pulse overlap, but this spurious power dies away as the pulses separate. (3) Two-channel WDM transmission of light modulated in amplitude-shift keying format appears feasible at 2.5 GB/s over distances of 7500 km. >
Patent•
25 Mar 1991TL;DR: In this article, the composite buffer type is used for single-and multi-fiber cables with a central optical waveguide fiber, a layer of fill compound surrounding the optical fiber, and a plastic jacket surrounding the layer of aramid fiber.
Abstract: Single fiber cables of the composite buffer type are provided which include: (a) a central optical waveguide fiber; (b) a layer of fill compound surrounding the optical fiber; (c) a layer of aramid fiber surrounding the fill compound; and (d) a plastic jacket surrounding the layer of aramid fiber. Multi-fiber cables are also provided which include: (a) a plurality of optical waveguide fibers; (b) a layer of aramid fiber surrounding the optical fibers; (c) fill compound in contact with the inner surface of the layer of aramid fiber and with the optical fibers; and (d) a plastic jacket surround the layer of aramid fiber. Methods for producing cables of these types are disclosed.
TL;DR: In this article, the field evolution along longitudinally nonuniform finite-cladding fibers of circularly symmetric cross section was analyzed in terms of coupled modes, where local modes were used for abruptly tapered fibers, whereas linear-index fiber modes provided the expansion basis for Kerr-type nonlinear-index fibers.
Abstract: Field evolution along longitudinally nonuniform finite-cladding fibers of circularly symmetric cross section is analyzed in terms of coupled modes. Local modes are used for abruptly tapered fibers, whereas linear-index fiber modes provide the expansion basis for Kerr-type nonlinear-index fibers. Convergence of the results suggests in both cases that only a finite number of bound modes is sufficient to describe the field adequately. A comparison with simulations given by a finite-difference beam-propagation method that was developed for circularly symmetric waveguides confirms the validity of this assumption.
Journal Article•
TL;DR: In this paper, periodic phase changes in the 10−6 -rad region were 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.
TL;DR: In this article, a model for PMD with random mode coupling was developed, and an explicit equation for the time-of-flight distribution was presented, and the coupling length on the order of 20-30 m was estimated.
Abstract: Polarization mode dispersion (PMD) in short and long single-mode fibers was measured by a polarization-maintaining Michelson interferometer. A nonnegligible PMD was found in some standard fibers. The sensitivity enables PMD to measure the bend-induced PMD of a fiber rolled on a 28-cm diameter drum. A theoretical model for PMD with random mode coupling is developed, and an explicit equation for the time-of-flight distribution is presented. Comparison between measurements on short and long fibers with residual birefringence leads to an estimation of the coupling length on the order of 20-30 m. >
TL;DR: Gain narrowing of the Stokes spectrum is observed as the input laser power is increased, and large stochastic fluctuations are observed in theStokes output intensity.
Abstract: We have investigated the statistical properties of stimulated Brillouin scattering (SBS) in a single-mode optical fiber. Gain narrowing of the Stokes spectrum is observed as the input laser power is increased, and large stochastic fluctuations are observed in the Stokes output intensity. The experimental results can be described well by a theoretical model that includes the spontaneous nature of the initiation of SBS.
TL;DR: In this paper, an interferometric fiber-optic sensor using a light-emitting diode (LED) as the optical source is analyzed and demonstrated using two Fabry-Perot interferometers (FPIs) in series, one for sensing and one which serves as a reference.
Abstract: An interferometric fiber-optic sensor using a light-emitting diode (LED) as the optical source is analyzed and demonstrated. The sensor arrangement employs two Fabry-Perot interferometers (FPIs) in series, one for sensing and one which serves as a reference. The optical output from the LED is spectrally modulated by reflection from the sensing FPI. Then, reflection or transmission by the reference FPI produces an interferometric beat response similar to that observed when a laser is used with the sensing interferometer alone. Best fringe visibility is obtained when the optical path lengths of the two interferometers are matched, and the fringes disappear when the path length difference becomes substantially greater than the coherence length of the LED. >
24 Jun 1991
TL;DR: In this paper, a second-generation Fabry-Perot interferometer for the near-infrared spectral region was constructed using silicon micro-micromachining techniques, which provided a sharp optical transmission peak which can be used as wavelength division demultiplexers in optical fiber communications systems.
Abstract: The techniques of silicon micromachining have been used to fabricate a second-generation Fabry-Perot interferometer for use in the near-infrared spectral region. These devices provide a sharp optical transmission peak which can be used as wavelength division demultiplexers in optical fiber communications systems. The wavelength tuning and parallelism control of the mirror elements are achieved electrostatically, by varying the voltage between control electrodes. This second-generation device includes a thin, etch-stopped corrugated diaphragm as the suspension for the movable element. >
TL;DR: A novel method of squeezing with optical pulses in a fiber ring reflector is demonstrated experimentally and detection is at low frequencies and is unaffected by guided-acoustic-wave Brillouin scattering.
Abstract: A novel method of squeezing with optical pulses in a fiber ring reflector is demonstrated experimentally. Squeezing of greater than 5 ± 0.3 dB has been observed. The pump is separated from the squeezed radiation with a fiber ring reflector and can be reused, in principle fully, as the local oscillator. The detection is at low frequencies (35–85 kHz) and is unaffected by guided-acoustic-wave Brillouin scattering.