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For the maintenance of railways on soft soils, accurate knowledge of the subsoil conditions is essential. Soft soils at shallow depths have high variability; thus, high spatial resolution is required. Spare telecommunication fiber-optic cables, known as dark fiber, can be used as an array of sensors to measure waves generated by running trains, which offers a unique opportunity to characterize shallow soils at high spatial resolution. We used dark fiber to measure seismic waves generated by running trains and implemented a seismic interferometry technique to retrieve surface waves. We evaluated the reliability of selected parts of the recorded signals split as bow waves (the train approaching the fiber), train waves (the train passing alongside the fiber), and tail waves (the train leaving the fiber) to retrieve broad-band surface waves. The analysis was performed in two distinctive zones. Zone I consists of a thick–soft (2.0–6.0 m thickness) layer, and Zone II consists of a thin–soft (less than 2.0 m thickness) layer, both overlaying a "stiffer" sand layer. At Zone I, train waves yielded the best results in revealing the thick–soft layer. At Zone II, the bow waves yielded clear high-frequency energy, revealing the overall soil structure but without identifying the shallow thin–soft layer. [ABSTRACT FROM AUTHOR]

A novel cantilever-type fiber Bragg grating (FBG) mechanical vibration sensor has been proposed with an excellent sensitivity through the use of the mechanical axial property of a suspended optical fiber with two fixed ends, enhancing the sensitivity and the resonant frequency. The experimental results show a resolution of 0.006g (where g represents the gravitational acceleration of 1g 9.81 m/s2), a resonant frequency of 227.3 Hz and a working bandwidth range of 10-210 Hz. The linearity and relative sensitivity errors are 1.9 % and ±4.4 %, respectively. [ABSTRACT FROM AUTHOR]

A method of one- and two-way comparisons of the time scales of distant ground objects with the use of a fiber-optic communication line is proposed. An optical pulse from one of the objects is transmitted through a fiber-optic line and the time this pulse is emitted and the time the pulse, reflected from the end of the fiber-optic line, arrives at a second object are determined in terms of the time scale of the radiating object. The divergence of the time scales of the objects is determined on the basis of the data obtained. A scheme of a system that implements this method and makes it possible to synchronize time scales with error not greater than 100 psec is considered. [ABSTRACT FROM AUTHOR]

The main aim of the work is the integration of modalmetric sensor in one arm. The proposed sensor is a classical fiber optic cable whose measuring arm is upgraded with multimode sensor. The aim of the research is to assess the impact of modal changes for detection of mechanical disturbances and comparative assessment of detection capabilities of interferometer sensor, modalmetric sensor, and hybrid sensor for different types of excitations. The measurements concerns the area of fundamental research. The results can be used in the construction of sensors with corresponding characteristics and properties, especially to protect museum collections. [ABSTRACT FROM AUTHOR]

This paper introduces the application of fibre-optic distributed temperature sensing (DTS) in combined sewer systems. The DTS-technique uses a fibre-optic cable that is inserted into a combined sewer system in combination with a laser instrument that performs measurements and logs the data. The DTS-technique allows monitoring in-sewer temperatures with dense spatial and temporal resolutions. The installation of a fibre-optic cable in a combined sewer system has proven feasible. The use of a single instrument in an easy accessible and safe location that can simultaneously monitor up to several hundreds of monitoring locations makes the DTS set-up easy in use and nearly free of maintenance. Temperature data from a one-week monitoring campaign in an 1,850m combined sewer system shows the level of detail with which in-sewer processes that affect wastewater temperatures can be studied. Individual discharges from houseconnections can be tracked in time and space. With a dedicated cable configuration the confluence of wastewater flows can be observed with a potential to derive the relative contributions of contributary flows to a total flow. Also, the inflow and in-sewer propagation of stormwater can be monitored. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of photonic crystal fibers (PCFs), which have been experimentally determined in the last few years in Iran's Telecom Research Center are analyzed and compared theoretically using an effective index method. The PCFs under investigation are fabricated with a high speed drawing process that has not yet been reported elsewhere. It was shown that at higher wavelengths in PCFs; the light field is confined in the core where in shorter wavelengths the field spreads into the cladding region. This phenomenon leads to affect the numerical aperture and the normalized frequency of the PCFs, because these two parameters directly depend on the diameter of the air-hole and the spacing between them in the cladding region. The measured results show that the PCF fabricated at high drawing speeds has a loss of 12 dB/km of speed, which is a reasonable level compared to other published reports. In addition, we have shown that a lower spacing between the adjacent air-holes would reduce the loss in the PCFs. [ABSTRACT FROM AUTHOR]

Abstract: The cable system layout for the NEMO Phase-2 project has been studied starting from the experience obtained after NEMO Phase-1 deployment. The aim has been to improve the reliability and simplify the integration procedures of the system. This has been attained by reducing the number of optical fibers in the backbone and by an improved layout of the optical links in the cabling. Moreover, an optimization in order to reduce the cost, in view of a large scale industrial production, has been performed. The design characteristics of the cabling system proposed for the detector line are presented. [Copyright &y& Elsevier]

The relationship is explored between reconfigurable optical add/drop multiplexers, fast becoming the standard nodal subsystem for providing flexibility in modern multichannel fiber optic networks, and wavelength selective switches, the predominant technology used to implement ROADMs. [ABSTRACT FROM AUTHOR]

Deregulation of telecommunication networks and utility companies has led to a worldwide increase in the use of fiber optic cables on long-span overhead power transmission lines. The cable jacket is subject to the deterioration caused by dry-band arcing, which is believed to be the major cause of failure of cable in, service. This paper establishes an arc model based on the physical mechanism and experimental observation, and performs simulation of the transient of dry-band arcing on ADSS fiber optic cable. The basic theories concerning the dynamics of arc, arc extension along the electrolytic surface and its speed, and dry-band arcing on ADSS cable are reviewed. The differential equation systems composed of the dynamic equation of the arc and its interaction with the circuit components are proposed with state variable method. And the equations are solved numerically with Runge- Kutta method. The proposed differential equations can be used to simulate dry-band arcing on experimental setup in laboratory and predict the dynamic behavior of dry-band arcing on ADSS cable in transmission network. Hence the damage caused to cable can be evaluated. Experiments are performed to verify the simulation results. [ABSTRACT FROM AUTHOR]

All dielectric self supporting (ADSS) fiber optic cables are suffering from damage caused by dry-band arcing. This paper investigates the formation of the dry band, which is crucial to the arcing. The formation of the dry band is the result of evaporation of water deposit some point on the cable surface. When the dry band is formed the current is interrupted. Then high voltage is applied to the small gap separated by the dry band, and may cause arcing. This paper discusses the drying process of the wet layer on the surface of the cable in detail. The differential equation of the drying rate is formulated and numerical simulation is performed. With this equation, the time-to-arcing and variation of the layer resistance can be estimated. For verification of the results, the time-to-arcing and layer resistance are measured in the laboratory. The numerical results provide guidance for design of an automatic dry-band arcing aging test system. The onset of arcing is investigated based on the results. [ABSTRACT FROM AUTHOR]

Transports between the Swedish mainland and the island of Gotland were studied by means of motionally induced voltages. The copper mantle of an existent fiber-optic telecommunications cable was grounded on Gotland, and the data acquisition system was installed on the mainland, whereby the bulk flow over the section could be observed. The magnetic field was simultaneously measured so as to permit a comparison with the induced voltage. It was found that geomagnetic fluctuations only weakly affected the observed voltage differences at subinertial frequencies, whereas in the superinertial range a considerable degree of geomagnetic influence was detected. The induced-voltage results were also compared to the geostrophic transports determined using tidal gauge data, analysis of which showed that the stratification of the western Gotland basin affected both types of calculations. Transport adjustments, based on taking into account the effects of stratification as well as the bedrock geological characteristics, were thus carried out. It was found that the best correspondence between the two independent estimates of the transport was obtained by locating the main halocline at a depth of 78 m, in good agreement with hydrographic results from the region. [ABSTRACT FROM AUTHOR]

In this paper, a new highly nonlinear dispersion-shifted fiber (HN-DSF) with an effective area of 9.3 μm2 is presented. This innovative HN-DSF has a unique triple-cladding structure, which offers not only a large nonlinear coefficient, but also low attenuation, low splicing, and bending losses. It is a very suitable candidate to implement an all-fiber wavelength converter via four-wave mixing (FWM). © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 153–156, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11312 [ABSTRACT FROM AUTHOR]

The development of optical fiber amplifiers has spurred study of the 1R (reshaping) repeating transmission method for transmission distances over 1000 km. As transmission distances become longer, there is the possibility that polarization mode dispersion and chromatic dispersion will limit transmission distances. In particular, polarization mode dispersion can be altered by the ambient temperature, cable structure, and situation of installation. The effects of such factors with respect to the polarization mode dispersion in submarine optical fiber cables have not been sufficiently clarified. Therefore, in this article, the authors investigate the polarization mode dispersion by using a submarine optical fiber cable with 12 fibers roughly 10 km in length to clarify the characteristics of a submarine optical fiber cable for application in long-distance transmission systems with optical fiber amplifiers. The results show that there is a correlation between the changes in the polarization mode dispersion after each cable manufacturing process and the change in the strain, as well as accompanying changes in lateral force. Finally, the temperature dependence (from 5 °C to 30 °C) of the polarization mode dispersion is also described. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(8): 76–84, 2000 [ABSTRACT FROM AUTHOR]

In response to the need for construction of new customer lines, usually the construction takes place at the joints where in-service lines are accommodated. It is very difficult to select and establish connection to a specific line without touching other in-service lines, thereby imposing additional curvatures upon them. Therefore, the losses are increased because of fiber bending; and, in such construction works, there is the fear that the transmission-loss variations exceed the tolerable threshold. To eliminate such fears, experiments on optical fiber handling are carried out and the factors which influence the transmission losses and the magnitude of such variations are clarified. Further, it is shown that by proper choice of the mode field diameter and the cut-off wavelength, it is possible to limit the variations of the transmission losses. The guidelines in the design of optical receivers which can tolerate these variations also are given. [ABSTRACT FROM AUTHOR]

In optical-fiber-cable networks of Japan,usually dry air is compressed into the cable and joins and gas-pressure sensors are used for remote-supervision of pressure maintenance. However, optical fibers are different from metallic lines and penetrating water is not a direct obstacles. Further, the manufacture of gas dams is not as easy as that of the metallic cables, and the gas dams become very large in size so that it becomes difficult to put them in the line. Therefore, the nonpressurized cables with reliabilities as high as those of the pressurized ones have been investigated. This paper discusses first the main factors responsible for the reliability deterioration of nonpressurized optical fiber cables and joint, which are the important elements of an optical system. Then, as the nonpressurized line structure, the waterproof optical fiber cables and the remote supervision of joints are discussed. using a simple remote-supervisory structure which consisted of the water sensors and OTDR, it is shown that the realization of reliabilities as high as those of the pressurised cables is possible. [ABSTRACT FROM AUTHOR]

To realize a ring-type optical LAN which is affected little by node failure and cable failure and yet is flexible in wiring, a star-ring LAN with optical accessors within an optical cabinet is proposed. Although the present system has art advantage of realizing a high reliability with a one-fold ring configuration, the system is susceptible to signal interference in optical accessors. The effect of this signal interference on the transmission quality has been evaluated by means of the equation for the equivalent transmission loss by Tokura et al. However, this equation was derived in the case where the discriminating level is always set at the optimum value of the main signal and is not applicable to a general receiving system which is set at the optimum value of the composite signal. In this paper, a configuration of the star-ring LAN is proposed first and its advantages are described. Next, an approximate equation for calculation of the equivalent transmission loss is derived for an optical receiver system which 15 set such that the discrimination level is an optimum value of the composite signal. Further, by means of experiments, the relationship is derived between the degree of interference and the equivalent transmission loss, and the experimental values are compared with the computed results. It is demonstrated that the computed and experimental results agree well. Finally, by the use of the results, the optimum value of the transmission loss of the optical accessors in a star-ring LAN is determined. [ABSTRACT FROM AUTHOR]

This paper discusses the flexibility of a cable when it is bent to the range of plastic deformation of the cable material. Considering the situation where the cable material exhibits elastic or plastic deformation, the expression for the maximum bending moment, which represents the flexibility of the cable, is derived in terms of the following parameters: The strain-hardening exponent n and the plastic modulus σ∗, which are material parameters; and the Outside and the inside radii γ1 and γ2, respectively which are the structural parameters. As a method to determine the foregoing material parameters experimentally, the three-point bending test is discussed. A method is presented which determines the strain-hardening exponent n and the plastic modulus σ∗ from the relation between the load P and flexion δ. The method is verified experimentally. The case is considered where the cable is composed of several materials such as sheath, core, and tension member, and it is demonstrated that the bending moment of the whole cable is given as a sum of the bending moments of the component materials. Thus, it is shown that if the material parameters of the cable components are known, the maximum bending moment of the whole cable, representing the flexibility, can easily be designed. [ABSTRACT FROM AUTHOR]

To construct an efficient subscriber optical fiber cable network, a highly economical and versatile distribution method is needed. This paper clarifies a technique in which by determining the installation cable size of feeder system and the ratio of common fibers to total fibers, a balance between the service requirement and cost is obtained. First, gamma distribution, practically used for metal cables, is applied to the demand forecast error distribution and the relation between the number of fibers and the ratio of common fibers to total fibers, which is required to obtain the desired equipment reliability, is clarified. Next, the relation between the cross-connecting probability is determined and utilizing the ratio of common fibers, the cost function of optical cable system is derived. Here, both the cable installation cost and cross-connection cost are considered. These two factors are combined and a design method of installation cable size and the ratio of common fibers to total fibers is clarified. This method ensures the desired equipment reliability and is the most economical one. Using this method and assuming all the various costs, it is clarified that for high cross-connection cost, a cable having a large number of fibers should be installed and the cable network construction having comparatively low ratio of common fibers to total fibers is desirable. When the cross-connection cost is less, the installation cable having a smaller number of fibers and a higher ratio of common fibers to total results in mind, an economical subscriber optical fiber cable network construction is proposed. [ABSTRACT FROM AUTHOR]

Resins such as epoxy have been used to form a gas-tight dam in communication cables. However, they have disadvantages due to the volume shrinkage during the curing period and thermal expansion. This causes reliability problems such as the breakage at the contact surface. Thus when resins are used in the optical fiber, the influence of their properties on the gas-tightness and optical loss must be well understood. This paper discusses the influence of the strain caused by the curing process of the resins on the optical loss and air-tightness. In addition, the structural design of a resin gas-tight dam is described. First, the influence of the strain in the optical fiber will be described and the design condition of the use of the resin to minimize the optical loss will the shown. Next, the design condition for air-tightness is discussed by obtaining the relationship between the hardness of the resin and gas-tightness, the method of experimentally obtaining the strain distribution in the strain at various temperatures during the curing process, and the application of the gas-tight dam for an optical fiber cable. From these results, a gas-tight dam with two layers of resin for strain absorbing to protect the optical fiber is designed. As a result of the evaluation of the properties of the designed structure, we decided that it is applicable to the optical fiber cable from the point of air-tightness and optical loss characteristics. [ABSTRACT FROM AUTHOR]

The ideal situation in constructing a broadband communication network is that all kinds of services are provided by a single network. Such a structure is not necessarily advantageous at the present state of technology. From such a viewpoint, the best approach would be first to construct an economically-optimum system, mostly considering the C - E type broadband distribution service, which is estimated to have the highest demand, and gradually extend the network for other services. This paper first describes that the configuration combining the star-type subscriber link and the tree-type trunk lines is economical and has the functional expendability. Next another configuration is considered, in which the optical fiber is used for the subscriber link and the frequency division switch is used for the channel selections in the conversion of network topology. It is shown that the system is the optimum from the viewpoint of the cost per subscriber. By applying the notion of the cross-contact switch, it is shown that the proposed system can be ex- tended to the C - E type video retrieval service and E - E type transmission service. The optical distribution system will be utilized effectively in the future new media, providing the basis for the broadband communication network. [ABSTRACT FROM AUTHOR]

This paper will discuss optical fiber cable distribution networks for accommodating the immediate introduction of optical subscriber networks. The concepts of cable distribution system design, the maintenance systems and the cables and jointing technology for supporting these systems will be discussed. The results of experiments using related technology will also be discussed. [ABSTRACT FROM AUTHOR]

Fiber optics cable has been adopted by telecommunication companies worldwide as the primary medium of transmission. The cable is steadily replacing long-haul microwave, copper cable, and satellite transmissions systems. Fiber cable has been deployed in an underground, submarine, and aerial architecture to transmit high-speed signals in intercontinental, inter countries, inter cities and intra-cities. Underground fiber cable transmission has experienced major failures as compared to other mediums of fiber transmission infrastructure. The failure is rampant, and especially the cable get cuts frequently in areas where there are road constructions, road road expansion projects, and other developmental projects. The cost of repairing these failures is enormous, and it largely depends on the cause of failure and the geographical area the faults occurred. The main aim of this paper was to investigate the cost of repairing underground fiber cable failures, clustered the cause of faults, and then used feedforward neural networks (FFNN) and linear regression to predict the cost of repairing future faults. The result of the predictive model is significant to the telecommunications industry, which means the cost of repairing an underground optical networks will be known to the industry players before the fault occurs. depending on which area, the cause of the failure and the mean time to repair (MTTR), the predictive model tells the mobile network operators the cost involved to repair the damaged cable. The accuracy of the result obtained indicates the predictive model is good for predicting the cost of repairing fiber cable cut in underground optical networks. [ABSTRACT FROM AUTHOR]

The article reports on the use of the fiber optic cable to boost over the air television signals in areas of poor reception in Great Britain. A greater number of television channels are possible, including a wide range of interactive two-way flows. The fiber optic industry was seen as a potential lucrative export base. Information flows would be speeded and it would deregulate the entire field of communications in which British Telecom held a monopoly. Advanced systems must be installed for cable to have a measurable impact on the industry.