Showing papers on "Photonic-crystal fiber published in 1983"
TL;DR: In this article, the basic birefringences that couple the two modes and change the polarization state along the fiber are reviewed, and three cases of uniform, phase-matched, and random coupling are considered.
Abstract: The polarization state of light in single-mode fibers is very sensitive to any perturbation which is not symmetric about the fiber axis. While this is a source of noise, drift, or signal fading in some applications, it can also be exploited in novel guided-wave devices. The basic birefringences that couple the two modes and change the polarization state along the fiber are reviewed. The three cases of uniform, phase-matched, and random coupling are considered. Polarization preservation in both low- and high-birefringence fibers is achieved by reducing this coupling. In addition to polarization-state changes, bireftingent fibers can quickly reduce the polarization degree of nonmonochromatic light if both modes are excited, a characteristic that greatly simplifies evaluation of the degree of polarization preservation in these fibers. Current evaluations of the birefringence and the polarization-holding ability of state-of-the-art fibers are discussed, and it is concluded that fibers with good polarization-holding properties are becoming available.
492 citations
Patent•
27 Jul 1983TL;DR: In this paper, the authors used a multiplexing coupler to combine the signal to be amplified and illumination from a pumping illumination source onto a single optical fiber, where the pumping illumination inverts the neodymium ions within the ND:YAG crystal.
Abstract: An amplifier for use with fiber optic systems comprises a neodymium YAG crystal placed in series with a signal-carrying optical fiber. The ND:YAG crystal is supplied by the optical fiber with both the signal to be amplified, and pumping illumination. The pumping illumination is coupled onto the optical fiber by a multiplexing coupler which is used to combine the signal to be amplified and illumination from a pumping illumination source onto a single optical fiber. The pumping illumination inverts the neodymium ions within the ND:YAG crystal. The signal to be amplified propagates through this crystal to stimulate emission of coherent light from the neodymium ions, resulting in amplification of the signal. Because this arrangement permits the ND:YAG crystal to be end-pumped with pumping illumination, and because the length of the ND:YAG crystal may be substantially greater that the absorption length for the crystal at the wavelength of the pumping illumination, virtually all of the pumping illumination may be absorbed within the ND:YAG crystal and used for amplification of the signal carried by the optical fiber.
287 citations
TL;DR: In this paper, the principles of operation, the design, and performance of a fiber-optic temperature-distribution sensor are discussed, which uses optical time-domain reflectometry (OTDR) to detect temperature-induced changes of backscatter power at many separate locations in the fiber.
Abstract: The principles of operation, the design, and performance of a fiber-optic temperature-distribution sensor are discussed. The sensor uses optical time-domain reflectometry (OTDR) to detect temperature-induced changes of backscatter power at many separate locations in the fiber. In liquid-core fibers, a sensitivity of 2.3 \times 10^{-2} dB/°C (0.54 percent° C-1) was observed. A measurement accuracy of 1°C with a spatial resoltuion of 1 m is attainable over a fiber length of 100 m.
188 citations
TL;DR: By use of the stimulated Raman process, optical solitons can be amplified and reshaped while they propagate through a glass fiber to allow the separation between two repeaters (amplifiers) to be decided by the fiber loss rather than by the Fiber dispersion.
Abstract: By use of the stimulated Raman process, optical solitons can be amplified and reshaped while they propagate through a glass fiber. When an appropriate level is chosen for the pump power (10–100 mW for 10-psec solitons), the solitons can be reshaped adiabatically. The method allows the separation between two repeaters (amplifiers) to be decided by the fiber loss rather than by the fiber dispersion.
146 citations
TL;DR: The importance of photoelastic effect in controlling polarization in optical fibers is discussed in this article, where measurements of the stress-optic coefficient, its dispersion, and temperature dependence are reported using a fiber measurement method.
Abstract: The importance of the photoelastic effect in controlling polarization in optical fibers is discussed. Measurements of the stress-optic coefficient, its dispersion, and temperature dependence are reported using a fiber measurement method. The results compare closely to data obtained for bulk silica by an extrapolation technique. It is shown that the dispersion of the stress-optic coefficient can have a significant effect on the performance of birefringent fibers and of fiber birefringent devices. Furthermore, the temperature dependence is sufficiently large to be troublesome in fiber sensors.
145 citations
TL;DR: In this article, a fiber polarizer with high modal birefringence (4.7 \times 10−4 ) was proposed to split the two polarizations of the fundamental mode and an ellipitcal depressed-index cladding to provide a steep wavelength-dependent tunneling loss to the fast axis mode.
Abstract: We report an oPtical fiber which guides only one polarization. This fiber polarizer utilizes high modal birefringence ( 4.7 \times 10^{-4} ) to split the two polarizations of the fundamental mode and an ellipitcal depressed-index cladding to provide a steep wavelength-dependent tunneling loss to the fast axis mode. The stress-induced birefringence is created by an elliptical SiO 2 -B 2 O 2 inner cladding. A 4.7-m length of polarizer fiber exhibits an extinction ratio of 34 dB at a wavelength of 633 nm, with polarizing behavior over a bandwidth of 50 nm. Insertion loss of less than 1 dB has been observed for the guided linear-polarization mode. The polarizing band may be shifted from 620 to 525 nm by bending the fiber to a radius of 0.67 cm. Such fiber polarizers should find a variety of applications in fiber sensors, attenuators, isolators, wavelength filters, and tuners.
143 citations
IBM1
TL;DR: The experimental results agree well with the predicted intensity dependence of the reshaping action of nonlinear birefringence during passage through a 150-cm-long, single-mode optical fiber and a crossed polarizer.
Abstract: We report the observation of strong reshaping of 3-psec dye-laser pulses by nonlinear birefringence during passage through a 150-cm-long, single-mode optical fiber and a crossed polarizer. For lower-intensity input pulses to the fiber, the transmitted pulses were observed to be proportional to the cube of the input pulses. With increased intensity, more-complicated pulse shapes were obtained. Our experimental results agree well with the predicted intensity dependence of the reshaping action.
95 citations
TL;DR: In this article, the beam-propagation method was used to calculate both the pure bending loss and the transition loss of bent single-mode optical waveguides and fibers, which allowed the authors to establish the accuracy of several commonly used theories of bending loss.
Abstract: We demonstrate that the beam-propagation method can be used to calculate accurately both the pure bending loss and the transition loss of bent single-mode optical waveguides and fibers. Our results allow us to establish the accuracy of several commonly used theories of bending loss and to investigate the degree to which theories of step-index monomode fiber losses can be used to predict the losses of graded-index monomode fibers.
93 citations
Patent•
21 Jun 1983TL;DR: An optical fiber assembly comprising at least two plastic optical fibers and an embedding material, which is arranged substantially in parallel to each other and embedded in said embedding materials, is described in this article.
Abstract: An optical fiber assembly comprising at least two plastic optical fibers and an embedding material, said plastic optical fibers being arranged substantially in parallel to each other and embedded in said embedding material, wherein each plastic optical fiber comprises a core of polymer having a refractive index, n 1 , and a cladding of a polymer having a refractive index, n 2 , wherein the refractive indices n 1 and n 2 satisfy the following relationship [I] n.sub.1 -n.sub.2 >0.01 [I] The optical fiber assembly is prepared by extruding from a spinneret a plurality of optical fibers having a core-cladding structure and an embedding material of a polymer in three layers of core, cladding and embedding material, according to a melt-spinning method; arranging the optical fibers in parallel to each other before solidification thereof; and bonding the optical fibers together through the embedding material.
66 citations
TL;DR: In this paper, a single-mode, single-polarization fiber design that can be realized by stress-induced birefringence was proposed, and the leakage rate was calculated by a perturbation method, which accounts for degeneracy between a bound mode and a packet of radiation modes.
Abstract: Optical fibers composed of highly birefringent material are studied. One of the two fundamental modes can be made leaky when the birefringence is sufficiently large. This suggests a novel single-mode, single-polarization fiber design that can be realized by stress-induced birefringence. The leakage rate is calculated by a perturbation method, which accounts for degeneracy between a bound mode and a packet of radiation modes.
61 citations
TL;DR: In this article, the reduction of the degree of polarization of broadband light due to propagation in ordinary single-mode fiber is examined theoretically and experimentally, and a model for one discrete mode-coupling center and extending it qualitatively to include multiple centers is developed.
Abstract: The reduction of the degree of polarization of broad-band light due to propagation in ordinary single-mode fiber is examined theoretically and experimentally. Previous work is extended to account for polarization-mode coupling along the fiber by developing a model for one discrete mode-coupling center and extending it qualitatively to include multiple centers. The existence of nonzero degree of polarization in long lengths of fiber is shown to be due to mode coupling at particular positions along the fiber and the degree of polarization is shown to be related to the degree of coherence associated with the mode-coupling site. The experimental results generally support the model developed.
TL;DR: Third-harmonic generation and three-wave sum-frequency light generation in a short-length elliptical-core optical fiber pumped by pulses from a Q-switched and mode-locked Nd:YAG laser, operating at 1.064microm, have been observed in the 355-385-nm spectral range.
Abstract: Third-harmonic generation and three-wave sum-frequency light generation in a short-length elliptical-core optical fiber pumped by pulses from a Q-switched and mode-locked Nd:YAG laser, operating at 1.064 μm, have been observed in the 355–385-nm spectral range. In particular, the third harmonics of the pump (λ0 = 1.064 μm, λ0/3 = 354.7 nm) and of the first Raman Stokes (λ1 = 1.116 μm λ0/3 = 372.0 nm) lines have been obtained with 5-kW peak power of the laser pulses.
TL;DR: It is concluded that a tapered fiber end with a large working distance reduces the influence on the laser's performance, and the influence of various fiber faces on laser power and wavelength stability is presented.
Abstract: The coupling of CSP lasers to single-mode fibers with different coupling structures made on the fiber face is investigated. In this case easy to make coupling arrangements such as tapers and microlenses, result in a high launching efficiency (∼2-dB loss), in contrast to launching from gain-guided lasers with strong astigmatism and a broader far-field pattern. Index-guiding lasers exhibit, however, a higher sensitivity to optical feedback. Laser output power and wavelength are changed due to reflections from the fiber tip. Critical distances exist which lead to a highly unstable laser spectrum. A comparison of the influence of various fiber faces on laser power and wavelength stability is presented. It is concluded that a tapered fiber end with a large working distance reduces the influence on the laser's performance.
TL;DR: In this paper, the authors investigated the possible use of Bragg fibers for long-distance low-loss optical communications, structures calculated, and their limitations were established, and it was found that the original Bragg fiber design offers no possibility of low loss propagation.
Abstract: The possible use of Bragg fibers for long-distance low-loss optical communications is investigated, structures calculated, and their limitations established. It is found that the original design of Bragg fibers offers no possibility of low-loss propagation.
TL;DR: In this article, a superluminescent diode (SLD) was designed to meet a wide range of optical system needs and demonstrated in a lensed 0.23 NA, 50 μm diameter graded index core fiber with a power of 550 μW at 250 mA and 20°C.
Abstract: A superluminescent diode (SLD) has properties, based on the degree of coherence, that are bounded by those of the light emitting diode and the laser diode. The SLD can be designed to meet a wide range of optical system needs. By introducing ridge-waveguide lateral confinement, a good anti-reflection coating at one end and a high reflectivity mirror at the other, we have demonstrated an SLD that allows 30 percent coupling efficiency into a lensed 0.23 NA, 50 μm diameter graded index core fiber. The power in the fiber is 550 μW at 250 mA and 20°C. It is possible to maintain a constant power level in the fiber greater than 250 μW over the temperature range 0 to 35°C by adjusting the current. The spectral width is 300 A and the modulation bandwidth 350 MHz. PCM with 400 Mbit/s rate has been observed. These devices are relatively easy to fabricate from ridge-waveguide lasers or any other lateral confinement laser.
TL;DR: In this article, a broad-band ultrasonic sensor based on induced optical phase shifts in single-mode fibers is demonstrated over a frequency regime of 0.5-50 MHz, and a recently developed theory used to predict the magnitudes of acoustically induced strains in optical fibers is verified.
Abstract: A broad-band ultrasonic sensor based on induced optical phase shifts in single-mode fibers is demonstrated over a frequency regime of 0.5-50 MHz. In addition, a recently developed theory used to predict the magnitudes of acoustically induced strains in optical fibers is verified.
TL;DR: A new technique for measuring the polarization mode coupling of a polarization-maintaining optical fiber is proposed that uses a modified optical time-domain reflectometry in which two kinds of backscattered signals coming through each principal axis of the fiber are utilized.
Abstract: A new technique for measuring the polarization mode coupling of a polarization-maintaining optical fiber has been proposed that uses a modified optical time-domain reflectometry in which two kinds of backscattered signals coming through each principal axis of the fiber are utilized. This technique shows how the mode coupling occurs along the fiber. The extinction ratio evaluated by the present technique is in good agreement with that obtained by a conventional technique (within ±0.5 dB).
TL;DR: The optical solitons in a glass fiber with dissipation can be reshaped by periodic amplifications and thereby can be stably transmitted for a sufficiently large distance, even when the amplifiers have gains with random variation.
Abstract: The optical solitons in a glass fiber with dissipation can be reshaped by periodic amplifications and thereby can be stably transmitted for a sufficiently large distance. We show that the solitons retain this basic property even when the amplifiers have gains with random variation.
Patent•
17 Mar 1983TL;DR: In this article, the position of the core (14) in the reflectivity profile of each surface can be readily identified and the fiber ends (18, 20) can then be manoeuvred transverse of the fiber axes to bring the fiber core centers into registration with a datum line.
Abstract: Before splicing optical fibers (10) having cladding (12) and core (14) of differing refractive index, have their cores (14) axially aligned. The fiber ends (18, 20) are held apart with the fibers approximately coaxial. The fiber end surfaces (18, 20) are then illuminated and reflected light is monitored. Since reflectivity is a function of refractive index, the position of the core (14) in the reflectivity profile of each surface can be readily identified. The fiber ends (18, 20) can then be manoeuvred transverse of the fiber axes to bring the fiber core centers into registration with a datum line. The fiber ends are then brought close together for splicing. Previously, fibers having nominally identical outside diameters were aligned simply by pressing them into a common V groove (24), the optical transmission efficiency then depending on fiber/core concentricity. Alternatively, light was injected into the far end of one fiber, monitored at the far end of the other fiber, and the fibers at their near end manipulated to maximize monitored optical power. The present invention provides an easier and cheaper method of ensuring core alignment especially for monomode fibers.
TL;DR: This paper is a brief review of the principles of optical fiber systems to serve as an introduction to the specific application and technology papers in this issue.
Abstract: This paper is a brief review of the principles of optical fiber systems to serve as an introduction to the specific application and technology papers in this issue. Fibers, transmitters, receivers, point-to-point transmission systems, multipoint buses, and sensor systems are discussed. Subsystems are reviewed in terms of thier input/ output characteristics.
TL;DR: Low-loss single polarization fibers that maintain a state of linear polarization well are proposed that are composed of the concentric circular GeO2- and/or P2O5-doped core and pure silica clad regions for constructing the low-loss waveguide.
Abstract: Low-loss single polarization fibers that maintain a state of linear polarization well are proposed. This fiber is composed of four regions: the concentric circular GeO2- and/or P2O5-doped core and pure silica clad regions for constructing the low-loss waveguide, and the B2O3-doped elliptical-jacket and the silica outer support regions for introducing the large nonsymmetric stress in the core. Theoretical and experimental studies on the coupling length of the two fundamental modes of orthogonal polarization and transmission loss have been carried out. An extinction ratio of less than −33 dB at 1-km fiber length and a loss of <0.8 dB/km at 1.5 μm were achieved.
TL;DR: The large variety of fiber optical intensity sensors reported to date will be classified by their sensing mechanism, and examples will be given for each category of sensors with reported performances.
Abstract: Fiber optical intensity sensors are made of optical fibers connected to a miniaturized optical sensor which is based on either a mechanical light valve, a light scattering process, a photoemission or photoabsorption process, or the transmission property of the optical fiber itself. Use of the optical fiber to transmit light to and from the optical sensor makes it possible to construct an electrically passive sensor with remotely located electronic readout capability. Major advantages of this type of sensors are electromagnetic interference immunity, electrical passiveness and safety, miniature size, and ruggedness, In this paper, the large variety of fiber optical intensity sensors reported to date will be classified by their sensing mechanism. Examples will be given for each category of sensors with reported performances.
TL;DR: The calculated phase sensitivity indicates that it is currently possible to measure a 1-microdegree C temperature change at frequencies exceeding 50 kHz with 1 cm of a metal coated optical fiber.
Abstract: The dynamic temperature phase sensitivity of a three-layer optical fiber is calculated for unjacketed as well as Al- and Hytrel-coated fibers. The calculations include both the variation of the refractive index with temperature and the thermally induced axial and radial strains. The calculated phase sensitivity indicates that it is currently possible to measure a 1-μ°C temperature change at frequencies exceeding 50 kHz with 1 cm of a metal coated optical fiber.
Patent•
09 May 1983TL;DR: In this article, an inline single-mode fiber attenuator is described, which may be formed by a tandem combination of a birefringent polarization-preserving fiber and a single polarization fiber.
Abstract: An inline single-mode fiber attenuator (10) is disclosed which may be formed by a tandem combination of a birefringent polarization-preserving fiber (12) and a single polarization fiber (14). The birefringent fiber functions as a variable wave plate and the single polarization fiber functions as a fiber polarizer. By continuously changing the local birefringence of the birefringent fiber with, for example, tension, pressure, or temperature, the phase difference between the two polarization components of light traveling through the birefringent fiber is continuously modified. The difference in phase causes suppression of one of the polarization components as it enters the fiber polarizer and, therefore, the output of the fiber polarizer, the sum of the two polarizations, is attenuated. The attenuator may be tuned by changing the local birefringence of the birefringent fiber. An inline optical fiber bandpass filter may be formed by cascading a plurality of appropriately arranged inline fiber attenuators formed in accordance with the present invention.
TL;DR: In this article, it was shown that stress birefringence in polarization-preserving fibers can be calculated by the simple addition of contributions from infinitesimal elements of the highly doped stress regions.
Abstract: It is shown that stress birefringence in polarization-preserving fibers can be calculated by the simple addition of contributions from infinitesimal elements of the highly doped stress regions. This method provides insight into the properties of stress-birefringent fibers and shows the equivalence between the various types of such fibers. In particular, it is seen that a circular barrier layer around the core does not reduce the birefringence and that high birefringence does not require a large stress cladding.
TL;DR: In this article, a low-loss single-polarization fiber with stress-induced birefringence has been fabricated using VAD single-mode fiber preforms.
Abstract: Low-loss single-polarization fibers with stress-induced birefringence have been fabricated using VAD single-mode fiber preforms. Design criteria have also been clarified with due regard to optimum fiber structure that reduces transmission loss and increases birefringence. As a result of these criteria, the minimum loss of 0.4 dB/km at 1.54 μm, and the birefringence B s of 1.2 \times 10^{-4} at 1.15 μm was obtained. It has been shown that a large refractive-index difference between the core and the cladding Δ, as well as large birefringence, are very effective to stabilize the state of polarization. In a 5-km-long fiber with \Delta = 0.8 percent and B_{s}= 1.2 \times 10^{-4} , crosstalk lower than -20 dB has been obtained.
TL;DR: In this paper, a method for obtaining permanent low-loss couping between arrys of single-mode fiber and Ti:LiNbO 3 waveguides is described, based on the use of silicon chip V-grooves, simplifies the coupling problem by simultaneously aligning the entire array and by providing a large surface area for a higher integrity adhesive bond.
Abstract: A method for obtaining permanent low-loss couping between arrys of single-mode fiber and Ti:LiNbO 3 waveguides is described. The technique, based on the use of silicon chip V-grooves, simplifies the coupling problem by simultaneously aligning the entire array and by providing a large surface area for a higher integrity adhesive bond. At \lambda = 1.3 \mu m, we measure an average 1.9-dB coupling loss (exclusive of propagation loss) for the assembled array. The average excess loss due to the fiber array is 0.8 dB. We present an analysis of the effect of various types of array misalignment on coupling efficiency. Angular alignment and array periodicity are found to be critical. If the fiber and waveguide periodicities are matched exactly, the fibers need only be placed within \pm 1.3\mu m of their optimum position to maintain coupling efficiencies greater than 90 percent.
TL;DR: In this article, an expression for the power flow in multimode optical fibers is derived, which is mathematically simple and allows a clear physical interpretation of the effects of mode coupling.
Abstract: An expression for the power flow, in multimode optical fibers, is derived, which is mathematically simple and allows a clear physical interpretation of the effects of mode coupling. Coupling strength is assumed to decrease with increasing axial angle. The solution obtained under this assumption is supported by experimental observations. Following the analysis, an experimental procedure to determine the coupling constant is devised. The theoretical results enable the prediction of the loss due to the mode coupling and the transmission bandwidth of the angular multiplexed channels in step-index optical fibers.
TL;DR: Results of pump-to-Stokes power conversion in a monomode fiber indicate a striking equivalence between pump power and fiber length and a qualitative explanation of these facts is proposed, although a detailed theory of nonlinear behavior of fibers is wanting.
Abstract: Several orders of stimulated Raman scattering (SRS) in monomode and multimode fibers have been observed. The relatively low power in the visible used in the quasi-stationary regime permitted observation of sharply defined Stokes and anti-Stokes spectral lines without any continua. Results of pump-to-Stokes power conversion in a monomode fiber indicate a striking equivalence between pump power and fiber length. The dependence of multiple SRS generation/amplification with these parameters is investigated up to the limit of near total pump extinction. We propose a qualitative explanation of these facts, although a detailed theory of nonlinear behavior of fibers is wanting. Parametric four-photon mixing is again confirmed to account for the generation of stimulated anti-Stokes radiation in multimode fibers and its absolute absence in monomode fibers.
TL;DR: Through an application of analysis to polarization-maintaining fibers, the properties of the polarization optical time-domain reflectometry have been made clear.
Abstract: Optical time-domain reflectometry for single-mode optical fibers has been theoretically discussed in terms of the Lorentz reciprocity principle and of a correlation function of the refractive-index fluctuation. Through an application of analysis to polarization-maintaining fibers, the properties of the polarization optical time-domain reflectometry have been made clear.