Abstract: Methods and systems for investigating downhole conditions are described. One method comprises inserting a tubular into a wellbore, the tubular comprising a tubular section having upper and lower fluid injection ports, and having a thermally insulated fiber optic cable section positioned inside the tubular extending to the upper fluid injection port, and a non-insulated fiber optic cable section positioned outside of the tubular section and extending at least between the upper and lower fluid injection ports; positioning the tubular section having upper and lower fluid injection ports near a suspected thief or pay zone; injecting a fluid through the upper fluid injection port; determining a first differential temperature profile between the upper and lower fluid injection ports; injecting a fluid through the lower fluid injection port; and determining a second differential temperature profile at least between the upper and lower fluid injection ports.

Abstract: An optical phase modulator made of lithium niobate or the like phase-modulates the output light of a single-wavelength laser light source 20 that emits CW light, and the phase-modulated light is inputted to a dispersion medium 22. The positive chirp and negative chirp of light to which frequency chirp is applied by phase modulation draw near in the dispersion medium and an optical pulse is generated.

Abstract: An optical fiber cable that sustains reduced increase in transmission loss and optical fiber breakage when subject to external pressure exerted thereon, comprises an aggregate of elements including central buffer filaments disposed in the center part of the optical fiber cable and a plurality of optical fibers disposed around the central buffer filaments, as well as circumferential strength filaments disposed around the outer periphery of the aggregate of elements, and a sheath covering the circumferential strength filaments.

Abstract: An apparatus for producing a low-PMD optical fiber having a furnace for melting a lower portion of an optical preform; a traction device for pulling an optical fiber from the lower portion of an optical preform; a spinning device for imparting a substantially constant and unidirectional spin to the optical fiber as it is pulled, which causes the fiber to undergo an elastic torsion; a winding device for winding the optical fiber onto a reel; and a twisting device for imparting to the spun optical fiber a unidirectional twist in a direction opposite the elastic torsion, so as to control the residual twist in the optical fiber. A process for producing the fiber, an optical fiber and a cable are also provided.

Abstract: A fiber optic cable having at least one optical fiber such as a microstructured bend performance optical fiber disposed within a protective covering. The protective covering is highly flexible and the fiber optic cable has extremely low delta attenuation when aggressively bent compared with the conventional fiber optic cable designs. By way of example, the delta attenuation of one fiber optic cable design is about 0.33 dB or less when wrapped 3 turns about a 7.5 millimeter mandrel at a reference wavelength of 1625 nanometers. Other variations of the present invention include a connector attached to the fiber optic cable.

Abstract: A method includes incorporating an optical fiber into a buffer tube, wherein the buffer tube has a first length. The buffer tube contains the optical fiber and a filler compound to create a buffer tube assembly. The buffer tube assembly is heated to an elevated temperature for a period of time, wherein the first length of the buffer tube decreases to a second length, such that extra optical fiber length is created relative to the second length. The buffer tube assembly is cooled to stabilize the second length and to retain the excess fiber length in the buffer tube.

Abstract: A method includes incorporating an optical fiber into a buffer tube, wherein the buffer tube has a first length. The buffer tube contains the optical fiber and a filler compound to create a buffer tube assembly. The buffer tube assembly is heated to an elevated temperature for a period of time, wherein the first length of the buffer tube decreases to a second length, such that extra optical fiber length is created relative to the second length. The buffer tube assembly is cooled to stabilize the second length and to retain the excess fiber length in the buffer tube.

Abstract: A test apparatus including an optical coupler for optically coupling a main frame and a test head is provided. The optical coupler has a plurality of optical fiber cables, a cable storage chain for bundling a stored portion except for a non-stored portion in a part of the test head side and a non-stored portion in a part of the main frame side of the plurality of optical fiber cables and storing the same, a test head side cable storage unit provided at the boundary between the non-stored portion and the stored portion of the plurality of optical fiber cables on the test head side and being capable of adjusting a length for storing therein the non-stored portion on the test head side and a main frame side cable storage unit provided at the boundary between the non-stored portion and the stored portion of the plurality of optical fiber cables on the main frame side and being capable of adjusting a length for storing therein the non-stored portion on the main frame side.

Abstract: A cable which includes conductor bundles prepared from at least one optical fiber positioned either centrally or helically about the center axis of the bundle, metallic conductors helically positioned around the bundles center axis, and a polymeric insulation material. A method of making a cable including forming a conductor bundle by placing helically positioned conductors and optical fibers about the periphery of a central optical fiber or metallic conductor, encasing the conductors, optical fibers, in a polymeric insulation material, and grouping the conductor bundles together.

Abstract: A mirror structure includes a plurality of features of a defined size. The features include alternating spatial units of a chalcogenide glass and a thermoplastic polymer, and are specifically arranged in an ordered form so that the structure is highly reflective. Thermally-assisted methods are introduced for forming such structures.

Abstract: A method and apparatus for determining and adjusting binder laylength during the process of manufacturing a selected fiber optic cable design. Specifically, a binder, having a distinguishing and physically detectable feature, is wrapped around fiber optic bundles or a buffer tube. A detection system detects the unique feature associated with the binder and thus creates a calculates a representative distance value. The distance value is calculated in relation the periodic spacing between two detected points on the physically detectable binder and is continuously monitored by a closed feedback loop. A computer receives status data from the closed feedback loop and compares the received data to a stored laylength parameter. In light of the comparison, an algorithm adjusts the binder head speed accordingly. This process repeats until the desired stored laylength is detected by the detection system.

Abstract: In one embodiment a macroscopically-sized specimen is illuminated with radiations of selectable multiple intensities and frequencies for viewing along a single viewing axis. A stage supports specimen to be observed. First and second illumination sources provide respective first and second radiations at predetermined different colors, permissively of different intensities. A special “bifurcated” fiber optic cable receives the first radiation into a first one of two radiation-receiving, or input, ends, and the second radiation into a second one of two radiation-receiving, or input, ends, so as to produce at each of at least two radiation-emitting, or output, ends an illuminating beam in which the first and the second radiations are mixed. The intensities and colors of both radiations are controllable.

Abstract: A signal receiver which receives an optical signal from a remote control includes a light guide for guiding a light passing through a front panel window toward a photodetector mounted on a circuit board. The light guide is made of a homogeneous material. A light guiding portion of the light guide extending from an entrance end to an exit end has a substantially circular cross section and is curved gently, not angularly. The exit end is configured to have a concave surface which is coaxial with the axes of both the cross section of the light guiding portion and a light-receptive portion of the photodetector. The exit end is disposed adjacent and opposite to the light-receptive portion.

Abstract: An array of fiber optic hydrophones or geophones is formed by winding of optical fiber around a continuous, yet flexible cylindrical core. The cylindrical core contains an elastomer filled with a specified percentage of voided plastic microspheres. The elastomer provides the necessary radial support of the optical fiber, and with the included voided microspheres, provides sufficient radial compliance under acoustic pressure for proper operation of the hydrophone. The cylindrical core can be made in very long sections allowing a plurality of fiber optic hydrophones to be wound onto it using a single optical fiber, with individual hydrophone elements separated by integral reflectors such as Fiber Bragg Gratings (FBSs). The center of the core may include a strength member and a central hollow tube for the passing of additional optical fibers. The aforementioned hydrophone array is then packaged within a protective outer coating or coatings as required for the specified application.

Abstract: A cable element and a method of making the same, in which the cable element has a central strength member, a plurality of buffer tubes are disposed on the central strength member, each of the plurality of buffer tubes encloses at least one signal transmission element, and a layer of pressure sensitive adhesive is provided on the central strength member. The pressure sensitive adhesive is a repositionable adhesive and releasably couples the plurality of buffer tubes to the central strength member such that the plurality of buffer tubes can be coupled and uncoupled repeatedly from the central strength member.

Abstract: An optical fiber cable suitable installation using an air-blown method is disclosed. The optical fiber cable has a center tensile member located at a center of the optical fiber cable to provide tension-resistant force, at least three loose tubes each of which includes at least one optical signal transmitting medium, and located to surround a peripheral portion of the center tensile member, a binder surrounding the loose tubes to maintain an alignment pattern of the loose tubes, and a sheath located at an outermost portion of the optical fiber cable. The optical fiber cable has a polygonal sectional shape having smooth edges.

Abstract: An optical cable having a metal tube receiving an optical fiber and bent to form a waved shape is disclosed. The optical cable may prevent cutoff of the optical fiber or deterioration of optical characteristics though tensile force is applied to the optical cable in its longitudinal direction since the metal is formed in a waved shape. To bend the metal tube, the metal tube is passed through roller pair(s) which are shaken in a direction perpendicular to the advancing direction of the metal tube. Thus, it is possible to obtain excess fiber length (EFL) easily and accurately as desired.

Abstract: In the present invention, a deformation process is applied to a part of an image fiber, and when implementing improvement of the quality of the transmitted image, the improvement of the image quality in the center region and peripheral region of the image fiber in the radial direction is carried out to an equal degree, and a uniform improvement of the entire screen can be carried out. A processed part is formed having a deformation of all cores that is substantially identical by deforming in the radial direction or by deforming and twisting a part of an image fiber having a plurality of cores that function as pixels in the radial direction thereof. The image fiber can be manufactured by a processing in which by a part of the image fiber having a plurality of cores that function as pixels is heated, and deformed in the radial direction thereof or simultaneously deformed and twisted in the radial direction thereof this heated part.

Abstract: An underground power cable having an optical fiber sensor for measuring temperature distribution is disclosed. In the power cable, an optical fiber for measuring temperature distribution is received in a stainless steel tube having excellent strength, and this optical tube is interposed between a core and a sheath of the power cable. When arranging the optical tube in the power cable, a supporting material having a relatively low strength than the optical tube is arranged in the cable together in order to prevent the optical fiber from being damaged by external force and prevent the inner insulation layer from being broken down by the optical tube. In addition, a fixing tape for fixing the optical tube in contact with the core may be added to prevent the optical tube from being bent seriously or inclined to one side when the cable is bent.

Abstract: The specification describes a technique for drawing circular core multimode optical fiber using twist during draw to increase fiber bandwidth.

Abstract: An optical cable for telecommunications having an optical core and a plurality of protecting and reinforcing elements or avers placed around the optical core. The optical core has a central reinforcing element, a polymer layer, a plurality of optical fibers incorporated in the polymer layer and a thin sheath which covers the polymer layer. The optical fibers have an alternating spin about their own axes with a maximum value of at least 4 twists per meter, and a core having a mean ellipticity in the range of 0.25 to 0.55, in such a way that the effects of birefringence of the fibers caused by the cabling process are significantly reduced.

Abstract: Disclosed is an interior optical cable including a plurality of tight buffer optical fibers; a subsidiary tension member surrounding the outer circumferences of the optical fibers; and an outer coating layer surrounding the subsidiary tension member, wherein the tight buffer optical fibers has a predetermined lay ratio to the outer coating layer.

Abstract: The present invention relates to an electroluminescent filament capable of emitting a plurality of colors and a method for manufacturing the same. Said electroluminescent filament of the present application comprises: A metal conductive wire as core wire; A medium insulating layer coated on the core wire; A light emitting layer coated on the medium insulating layer; A conductive layer coated on the light emitting layer; At least one or more transmission conductive wires wound at interval on the outside of the conductive layer; The transparent polymer casing tube covering the transmission conductive wires and the outer side of the surface of conductive layer not covered by transmission conductive wires; The polymer casing tube of at least 2 to 8 colors covering the outer layer of transparent polymer casing tube and forming light emitting filament with helical or sectional colors combination.

Abstract: A method for the direct measurement of large strains in ropes in situ using a plastic optical fiber, for example, perfluorocarbon or polymethyl methacrylate and Optical Time-Domain Reflectometer or other light time-of-flight measurement instrumentation. Protective sheaths and guides are incorporated to protect the plastic optical fiber. In one embodiment, a small rope is braided around the plastic optical fiber to impose lateral compressive forces to restrain the plastic optical fiber from slipping and thus experience the same strain as the rope. Methods are described for making reflective interfaces along the length of the plastic optical fiber and to provide the capability to measure strain within discrete segments of the rope. Interpretation of the data allows one to calculate the accumulated strain at any point in time and to determine if the rope has experienced local damage.

Abstract: A tow cable in which the temperature of the cable is measurable by the use of multiplexing capability intrinsic to optical fibers in which the optical fibers are positioned at the center of the tow cable and wound as part of two layers of surrounding strength wires. The optical fibers of the two layers intersect a vector extending radially from the optical fiber at the center to an outer surface of the tow cable. Light signals emitted from a multiplexer to positions along the optical fibers, in which the positions intersect the vector, return light signals from the positions to provide measurements that in conjunction with a data processor further provide temperature measurement of the outer boundary of the tow cable.

Abstract: The present invention relates to an electroluminescent light source. In particular, it relates to an multi-colored electroluminescent cable capable of changing colors, which comprises: a group of electroluminescent filaments which consist of a plurality of electroluminescent filaments of different colors and are insulated from each other, helically wound on the outer side of the axis; a transparent and flexible polymer casing tube disposed on the outer side of the group of electroluminescent filaments. The advantage of the present invention is low in power consumption, simple in structure, convenient for use, and has relatively long service life. The filament can be bent into a plurality of geometrical shapes as consumers demand, and it is beautiful and appealing.

Abstract: For the longitudinal application of at least one elongated retainer element onto a longitudinally extending bundle having a plurality of electrical and/or optical transmission elements, a retainer element is formed into a loop at successive discrete locations of the bundle and the respective loops are tightened to form a retaining force. Preferably, the loops are chained together by having the loop of the next following loop passing through the preceding loop.

Abstract: A medical imaging system with a base unit including an electronic display, and a remote imaging transducer connected to the display unit via a flexible cable. The cable includes a number of signal transmission lines, each of which includes a twisted pair of conductors for digital differential signal lines. Each conductor is connected at a first end to the transducer, and at a second end to the base unit. The signal transmission lines may be wrapped about a core, which may be an optical conduit communicating with a light source at the base unit.

Abstract: A communication cable including at least one communication element having a ripcord for ripping at least one cable component for facilitating access to the communication cable. In one embodiment, the ripcord is formed from a plurality of plies twisted together in a first direction, each of the plurality of plies being formed from a plurality of strands twisted together in a second direction. In another embodiment, the ripcord is formed from at least two different filament materials such as polyester and polyethylene.

Abstract: A termination assembly for use in an optical hydrophone module, comprising a module oil seal and an optical fiber seal. The termination assembly is used at the ends of modules and provides a means for filling individual modules with fill fluid. A module oil seal comprises a cylindrical wall defining a cavity, with one end substantially closed and the other end open. An annular face plate on the open end makes a seal dividing a coupling and a clevis. A check valve is mounted to an orifice that passes through the substantially closed end of the module oil seal. Optical fibers pass through the substantially closed end and the optical fiber seal is provided around the optical fiber that passes therethrough. The fiber seal fits snugly in a module oil seal opening. Both components serve to provide a seal that can withstand high pressures and maintain optical fiber integrity.

Abstract: Optical cable (1) for telecommunications, having low PMD and attenuation values, said cable comprising a central element (4), a plurality of optical fibres (3) and a layer of polymer material (5) devoid of discontinuities and incorporating both the central element (4) and the optical fibres, each of the optical fibres (3) being ranged along an open helix trajectory along which it has a torsion with a mean value of zero and a local maximum value of between 0.05 turns/m and 1 turns/m.

Abstract: An optical fiber includes a first core having a relative refractive index difference of larger than 0.36%, and a cladding. The optical fiber has fiber cut-off wavelength &lgr;c of more than 1350 nm, cable cut-off wavelength &lgr;cc of less than 1285 nm, bending loss at a wavelength of 1625 nm of not more than 10 dB/km when wound at a diameter of 20 mm, transmission loss at a wavelength range of 1285 to 1625 nm of not more than 0.40 dB/km, transmission loss at a wavelength of 1383 nm less than transmission loss at a wavelength of 1310 nm, and difference in transmission loss at a wavelength of 1383 nm of not more than 0.04 dB/km before and after exposure to hydrogen. The lower bending loss of the optical fiber provides an optical fiber cable for use in a WDM transmission in wavelength range of 1285 to 1625 nm.

Abstract: An optical fibre arrangement has at least two optical fibre sections, each optical fibre section defining an outside longitudinally extending surface. The outside longitudinally extending surfaces are in optical contact with each other. The invention further provides for an amplifying optical device have an optical fibre arrangement as just described, and a pump source. The amplifying optical device is configured such that the pump source illuminates the amplifying optical fibre. A amplifying arrangement is also disclosed. The amplifying arrangement includes a plurality of amplifying optical devices as just described, and each amplifier also has at least one input fibre and a first multiplexer connected to the input fibre. Each amplifier is configured such that at least one of the amplifying optical fibres is connected to the first multiplexer. The amplifying arrangement also has a second multiplexer connected to each of the first multiplexers.

Abstract: A fiber optic cable including a cable core having at least one optical fiber and a ripcord. In one embodiment, the ripcord is a conductive material operative, upon application of a sufficient pulling force, to rip at least one cable component for facilitating access to said at least one optical fiber. In other embodiments, the ripcord is formed from a semi-conductive material, the ripcord is removably attached to at least one cable component, and/or the ripcord has an excess length.

Abstract: An optical fiber cable (10) type comprises at least one tube (12) having optical fibers (14) housed therein. The optical fibers (14) extend helically in a longitudinal direction inside the tube (12). In the method of the invention, the tube (12) is fed to the die for manufacturing the cable (10) by unreeling the tube (12) from the storage reel (24) while the storage reel (24) is held stationary, thereby conferring longitudinal twist on the tube (12) constraining the optical fibers (14) it contains to follow a helical path of pitch substantially equal to the length of one turn of the tube (12) wound on the storage reel (24).

Abstract: An optical cable having a metal tube receiving an optical fiber and bent to form a waved shape is disclosed. The optical cable may prevent cutoff of the optical fiber or deterioration of optical characteristics though tensile force is applied to the optical cable in its longitudinal direction since the metal is formed in a waved shape. To bend the metal tube, the metal tube is passed through roller pair(s) which are shaken in a direction perpendicular to the advancing direction of the metal tube. Thus, it is possible to obtain excess fiber length (EFL) easily and accurately as desired.

Abstract: A fiber optic assembly and method of manufacturing the same include at least one central strength member, a first layer of optical fibers, a second layer of optical fibers, and a jacket. The first and second layers of optical fibers are adjoining layers formed by a common strander. Optical fibers can migrate between the adjoining two layers at different longitudinal positions in the cable without entanglement among themselves. Additionally, the optical fibers in adjoining layers can have the same lay length and same phase relationship.

Abstract: A system for organizing elongated objects (such as wires, cables, pipes, hoses, ducts, tubing, and other similar items) into bundles to create a more uniform, neat and functional arrangement is disclosed. The system includes a fastener adapted to extend along the length of an elongated object. The fastener provides a continuous attachment to another elongated object or to another object for a distance along the length of the elongated object. The fastener is preferably integrated with the structure of the elongated object, or alternatively, it may be applied as a wrap around the elongated object.

Abstract: An optical cable for telecommunications having an optical core and a plurality of protecting and reinforcing elements or layers placed around the optical core. The optical core has a central reinforcing element, a polymer layer, a plurality of optical fibres incorporated in the polymer layer and a thin sheath which covers the polymer layer. The optical fibres have an alternating spin about their own axes with a maximum value of at least 4 twists per metre, and a core having a mean ellipticity in the range of 0.25 to 0.55, in such a way that the effects of birefringence of the fibres caused by the cabling process are significantly reduced.

Abstract: Disclosed is a premises-fiber optical cable with a S-Z stranded-strength member, comprising: a plurality of inner tightly-coated optical fibers disposed at the central region of the optical cable and being S-Z type stranded; a plurality of inner yarns S-Z type-stranded for surrounding the inner tightly-coated optical fibers; a plurality of outer tightly-coated optical fibers S-Z type-stranded for surrounding the inner tightly-coated optical fibers and the inner yarns; a plurality of spirally-stranded outer yarns surround the outer tightly-coated optical fibers; and, an outer jacket disposed at the outer region of the optical cable for surrounding the outer yarns.

Abstract: A system and method for determining the lay length of S-Z stranded buffer tubes during the manufacturing process of a fiber optic cable without slowing down the manufacturing process. Images of an S-Z stranded buffer tube are captured with a camera. The images are sent from the camera to a computer workstation. The computer workstation displays the images taken with the camera and executes programming modules that calculate the lay length of the S-Z stranded buffer tube during the manufacturing process of the cable. Input devices such as a mouse and a keyboard may be used in conjunction with the operations of the computer workstation. By measuring the lay length during cable manufacture, productivity may be maintained while ensuring that the stranding of buffer tubes does not fall out of tolerance, which might result in deleterious bending stress of optical fibers within the buffer tubes.

Abstract: A novel fiber optic tube and method of forming the fiber optic tube. The method includes placing at least one optical fiber onto a tape with lateral ends and forming the tape into a tube. The length of the at least one optical fiber is longer than the length of the tape. Thus, the fiber optic tube has at least one optical fiber placed on the inside wall of the tube.

Abstract: A wavelength to optical power converter and a method for converter a wavelength into an optical power are provided. The wavelength to optical power converter includes an input fiber pigtail for inputting an optical wavelength signal, a spiral fiber connected to the input fiber pigtail, a cylinder for fixing the spiral fiber, an output fiber pigtail extended from the spiral fiber, and an optical detector connected to the output fiber pigtail for reading a signal from the output fiber pigtail to generate the optical power, wherein the spiral fiber outputs the optical power in response to the optical wavelength signal, thereby performing a conversion from the wavelength into the optical power.

Abstract: The present invention relates to a tube-enclosed optical cable containing ribbon units, and more specifically to a tube-enclosed optical cable containing ribbon units which can improve the economical efficiency of the process by simplifying the manufacturing process of optical cable and at the same time can improve the water blocking capability and compression characteristics of optical cable, providing optical cable characterized by coating particularly the central member of the cable with an absorptive substance and optical cable characterized by inserting interstices coated with an absorptive substance into the empty spaces between one more tubes encircling the central member and the sheath enclosing the tubes.

Abstract: An optical cable (1) has at least two optical fibers (2, 3), composed of plastic, which are surrounded by a common sheath (6) made of insulating material. To ensure functional endurance, even with frequent bending, the optical fibers (2, 3) are stranded together with a short length of lay which is smaller than six times the diameter (D) of an optical fiber (2, 3). In addition, at least two layers of high tensile strength fibers (5) composed of insulating material are stranded around the optical fibers (2, 3), which are stranded together.

Abstract: Disclosed is a fiber optic cable, comprising a central strength member, disposed at the center of the cable, for providing tensile strength; a plurality of inner tight buffered cores disposed in a linear form around the central strength member; a plurality of outer tight buffered cores, twisted in a spiral or S-Z form, for enclosing the inner tight buffered cores; and a jacket, disposed on an outermost circumference of the cable, for protecting an interior of the cable from external environments.

Abstract: A fiber optic light-emitting panel having one or more braided fiber optic strand assemblies formed into a light-transmitting device. The fiber optic light-emitting panel includes a plurality of three or more fiber optic strands braided together to form a braided fiber optic strand assembly. Each of the fiber optic strands includes a single optical fiber or a plurality of optical fibers to form a bundle. Each of the fiber optic strands within the braided fiber optic strand assembly has at least three (3) bends per inch along the length thereof for transmitting light laterally at the bends to form the light-transmitting device. The fiber optic light-emitting panel includes plastic ties for connecting at least two (2) of the braided fiber optic strand assemblies to form the fiber optic light-emitting panel.

Abstract: Fiber optic cables, and methods of manufacturing the same, include a plurality of carriers having at least one optical fiber therein. In one embodiment, the carriers are arranged in two layers within the cable and are generally disposed about a center area of the cable. Each layer has a respective helix-plus-EFL value. A difference between the respective helix-plus-EFL values of the layers defines a differential range being, preferably, about 1% or less. Additionally, the fiber optic cables can be used in fiber optic cable systems such as dispersion managed cable systems (DMCS).

Abstract: A medical imaging system with a base unit including an electronic display, and a remote imaging transducer connected to the display unit via a flexible cable. The cable includes a number of signal transmission lines, each of which includes a twisted pair of conductors for digital differential signal lines. Each conductor is connected at a first end to the transducer, and at a second end to the base unit. The signal transmission lines may be wrapped about a core, which may be an optical conduit communicating with a light source at the base unit.

Abstract: A buffer tube design that allows easy access to signal carrying fibers disposed within the buffer tube with risk of damaging the signal carrying fibers. The buffer tube can be made with a ripcord disposed within. Additionally, the buffer tube has the mechanical properties that allow the ripcord to be pulled through the tube wall with less energy than is required to bend the signal carrying fibers within. The buffer tube can also be designed without a ripcord in such a way that the mechanical properties allow the tube to be hand torn using a lower amount of energy than required to bend the signal carrying fibers within.