Abstract:
A composite cable includes at least two optical fiber components and at least one additional component. An irradiated crosslinked jacket surrounds the optical fiber component and the at least one additional component. A shield encloses at least the two optical fiber components within the jacket, where the shield protects the optical fibers from irradiation of the crosslinked jacket.

Description:
BACKGROUND 
     1. Field of the Invention 
     This application relates to cables. More particularly, this application relates to composite fiber optic, power and signal type cables. 
     2. Related Art 
     In the art of cable production, composite cables are cables that combine both power conductors as well as signal cables within a single outer jacket. Such cables can be used for many self contained power/signal transmission connections. A common use for such composite cables is for connecting cameras, such as CCD security cameras, for providing power, signal transmission and actuator control of the camera. See for example prior art  FIG. 1  wherein various cable types are included within a single jacket. 
     A number of such composite cables are offered with various constructions, typically as an assembly of copper and fiber elements. However, such prior art cables lack the ability to deliver the power necessary over distances of 300 to 5000 ft, nor the ability to carry a 20-400 volt range and 0.5 to 5 amps with sufficient ground safety factors protecting from eventual flex failure. Furthermore, the prior art cables also lack sufficient jacket crosslink to survive 24 hours at 100 degree C. in heavy diesel fuel. An exemplary standard that employs such test parameters is EIA/TIA-455-12A. 
     To achieve such a cable it is highly desirable to have a well-crosslinked polymer jacket for the composite cable. Crosslinking of the polymer in the jacket provides, among other advantages, improved heat resistance, decreased permeability and better abrasion resistance. 
     One manner in achieving fast and complete crosslinking of the polymer jacket, so as to make it sufficiently crosslinked to survive diesel oil soak, is to use a process of electron beam processing (or E-beam processing) where the jacket is subjected to irradiation by a high energy electron beam. Although this has the advantage of providing a well cross linked jacket, if optical fibers are included in the cable under this jacket process, the fiber element of the composite cable is also inadvertently subject to the irradiation as well. Such irradiation from an E-beam processor, as with any radiation exposure (background radiation post installation etc. . . . ) can cause noticeable signal attenuation in the fibers, as the material of the fibers is altered/damaged during the irradiation process. 
     OBJECTS AND SUMMARY 
     The present arrangement provides a composite cable with optical fiber, power and signal tactical elements, that has an improved durability and may be used longer before flex-failure, and even after flex failure in some cases. Moreover, the composite cable is constructed so that the fiber component therein is protected during the crosslinking process used on the cable jacket. 
     In one arrangement, the present invention provides for utilization of shields to prevent e-beam damage to optical fiber. Through the utilization of material that can be exposed to multiple crosslinking methods, the e-beam crosslinking, method can be used initially, and followed by other crosslinking methods such as moisture, curing to complete the process to sufficiently reach a crosslink density enabling the plastic to withstand 24 hours in 100 C diesel fuel, under the EIA/TIA-455-12A testing standard. 
     In another arrangement, the optical fiber component shields are utilized to supplement the bare ground wire enabling the composite cable to be more readily monitored for power loss failure for conductor jacket rupture from excessive flexing due to human or environmental factors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be best understood through the following description and accompanying drawings, wherein: 
         FIG. 1  shows a prior art composite cable. 
         FIG. 2  shows a composite cable, in accordance with one embodiment; 
         FIG. 3  shows a composite cable, in accordance with another embodiment; and 
         FIGS. 4A-4D  show composite cables of  FIG. 2 , with a shield element, in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment, as shown in  FIG. 2 , a composite cable  10  is shown having a central grounding member  12 . Preferably, central grounding member  12  is constructed as a copper wire, such as size 14 (AWG) copper wire, however, the invention is not limited in that respect. 
     Surrounding central grounding member  12 , are two conductor wires  14 A and  14 B. Preferably, conductor wires  14  are constructed as copper wires, such as size 18 (AWG) copper wire, however, the invention is not limited in that respect. Conductor wires  14  make up the electrical carrier component of composite cable  10 . 
     In one arrangement, in the case of grounding member  12  and conductors  14 , fine stranded tinned copper is used to improve the flexibility of those members and thus the entire cable  10  as a whole. 
     Also positioned around central grounding member  12 , are two fiber optic elements  16 A and  16 B. Preferably, fiber optic elements  16  are tight buffer optical fibers  17 , surrounded by an aramid filler  18  within a larger flame retardant jacket (subunit)  19 . However, the invention is not limited in that respect. This construction of optical fiber elements  16  provides additional strength and flexibility to these members and the cable  10  as a whole. 
     Also surrounding central grounding member  12 , as shown in  FIG. 2 , is a twisted pair  20  for digital signal transmission. Also, a drain wire  24  may be included with pair  20  for additional fault protection. 
     The above components are encased within an outer jacket  30 , such as an extruded polymer jacket made from polyurethane or polyethylene. Within jacket  30 , a rip cord  32  may be used for easy removal of the jacket and additional aramid filler fibers  34  may be included for added tensile strength. Aramid fibers  34  may be added to cable  10  in a 3-6″ contra-helical lay length to facilitate flexibility while simultaneously adding strength. Additionally, aramid fibers  34  may be coated with super absorbent polymers to provide a barrier against water ingress into cable  10 . 
     Once cable  10  is constructed as set forth above, it is contemplated that the polymer of jacket  30  is crosslinked in order to improve the durability, abrasion resistance, and other various advantageous qualities to the jacket. Polymers may be formulated such that the crosslinking is performed in various modes, including CV (Continuous Vulcanization), E-beam and Silane/Moisture curing. In one of the arrangements, jacket  30  is crosslinked using the E-beam mode because of its thorough/complete crosslinking, cleanliness and low secondary material costs. It is contemplated that such e-beam processing of jacket  30  may be affected with incremental processing (several iterations). This lessens the damage to fiber elements  14 , allowing them to at least partially recover between iterations. Any of the embodiments described herein may be used in conjunction with this incremental processing of jacket  30  by e-beam. 
     In another arrangement, in order to reduce damage to fiber elements  14 , jacket  30  may be constructed of a polymer capable of multi-mode crosslinking. For example, in one arrangement, upon the formation of jacket  30 , crosslinking may be partially affected by e-beam irradiation to an extent not to cause damage to fiber elements  14  therein. Later, crosslinking of the jacket may then be completed using other methodologies, including but not limited to moisture/humidity processing, Silane cure, peroxide cure or some combination of these methods. This provides at least some advantages of the e-beam type cross linking, without excessive irradiation reaching fiber elements  30 . 
     In either arrangement, it is contemplated that the crosslink density of jacket  30  should advantageously enable the polymer to withstand 24 hours in 100 C diesel fuel without failure, as per the EIA/TIA-455-12A testing standard. 
     As shown in  FIG. 2 , the assembly of the components described above, are configured to be evenly distributed around ground member  12  so as to have consistent stiffness and flexibility. Additionally, in one arrangement, conductors  14 , fiber elements  16  and twisted pair  20  may be advantageously stranded around central member  12  The components are helically stranded about the center element of themselves with a preferred lay length from 3-7 inches. 
     In such an arrangement, with the elements of composite cable balanced around central member  12 , cable  10  is capable of flexing in every direction with less chance of achieving a fault. Also, even if a partial fault is found in one of the components, because they are centrally located near the central grounding member  12 , the frayed ends of the faulted component will ground, allowing the other components to continue until cable  10  is replaced. 
     In another arrangement, as shown in  FIG. 3 , up to an additional 5 jacketed conductors  40 , such as 26 AWG copper wires, may be added for additional uses such as part of a ground fault alarm system and or a digital electrical communication signal. 
     In another embodiment as shown in  FIG. 4A , a shield  50  is provided around at least one set of components of cable  10 , namely fiber elements  14 A and  14 B. This shield  50  is arranged to provide irradiation protection for the optical elements  17  to prevent attenuation causing damage during the E-beam irradiation/crosslinking of jacket  30 . Shield  50 , which is grounded, is able to draw electrons from the e-beam process that contact shield  50  away from fiber elements  12  therein. 
     As shown in  FIGS. 4B ,  4 C and  4 D shield  50  may be arranged around additional components a well. For example,  FIG. 4B  depicts one portion of the shield  50  covering twisted pair  20 . In  FIG. 4C , a unitary shield  50  covers both fiber elements  14  as well as twisted pair  20 . In  FIG. 4D , the shield extends around all of the internal components of cable  10 . Although the arrangement of  FIG. 4D  would protect fiber elements  14  during cross linking irradiation of jacket  30 , the other limited size shield arrangements of shield  50  shown in  FIG. 4A-4C  may be additionally advantageous in that they may be formed of minimal size so as not to add substantial cost or weight to composite cable  10 , both of which are significant, particularly in densely packed composite type cables. 
     In one arrangement, when shield  50  is used in conjunction with a jacket  30  that has been crosslinked with partial e-beam and partial humidity crosslinking, it is contemplated that there can be a reduction in the size and/or thickness of shielding  50  to account for the lesser need to protect against the more limited electron radiation. 
     It is noted that in addition to shield  50  protecting fiber elements during irradiation of jacket  30 , it additionally may serve as a grounding fault protection in the event one of the conductors  12  experiences an insulation breech. For example, shield  50  and central bare copper element  12  may be arranged to signal copper power loss in conductors  14  from rupture of cable  10  from excessive flexing. 
     The material used for shield  50  may be selected from any number of materials including, but not limited to silver, nickel, tin plate, copper, lead, graphite, carbon and aluminum (sheet or vacuum deposit). 
     In one arrangement shield  50  is made from a laminate of aluminum, nickel, tin plate, copper and lead, so as to screen out all of the potential radiation from the crosslink process as well as radiation from the use environment either from nearby equipment, power plant normal operation or calamity, landfill leakage, munitions leakage, weapons accidental or intentional discharge. It is also contemplated that shield  50  may be made from a more basic aluminum/nickel material. 
     In one arrangement, shield  50  (individually or combined as per the embodiments shown in  FIG. 4A-4D ) may have a thickness range of 0.0005″ to 0.002,″ and preferably 0.001″ individually or combined. It is contemplated that shield  50  may have a plastic laminate on one or more sides of thickness of 0.0005 to 0.001, to aid in processing or applying shield  50  to cable  10 . 
     The shield should be of sufficient material/dimension so as to prevent or substantially prevent damage to fiber elements  14  during the complete or partial E-beam irradiation of jacket  30 . 
     While only certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes or equivalents will now occur to those skilled in the art. It is therefore, to be understood that this application is intended to cover all such modifications and changes that fall within the true spirit of the invention.