Abstract:
In one aspect the invention comprises a system and a method for marine geophysical exploration, which includes a first cable connected to a vessel and a plurality of streamer cables connected to the first cable. The first cable includes all towing strength members and all electrical power and data transmission conductors for the connected streamer cables.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Not applicable.  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not applicable.  
         BACKGROUND OF INVENTION  
         [0003]    1. Field Of The Invention  
           [0004]    This invention generally relates to methods and apparatuses for towing multiple streamer array systems  
           [0005]    2. Background  
           [0006]    One of several conventional techniques for marine seismic surveying is to tow a number of hydrophones behind a vessel over the survey area. Typically, the hydrophones are contained in one or more cables called streamers. Seismic impulses are created and their reflection from the sea bottom and the underlying strata is received by the hydrophones. This data is then used to image the sub-sea strata. Because it is advantageous to extend the hydrophone pattern over a large portion of the survey area, several streamers are towed at the same time.  
           [0007]    [0007]FIG. 1 illustrates a conventional streamer configuration from an aerial view. Conventional streamer configurations use a vessel  1  to pull streamers  2 . Paravanes  3  are used to keep the multiple streamers  2  separated. The paravanes  3  pull various lead in cables  7  and other cables  8  laterally away from the vessel  1 . Use of the paravanes and the configuration of the lead-in cables (or spreader cables)  7  and superwide cables  8  enables several streamers  2  to be pulled from a single vessel  1  in a wide pattern. However, the more lead-in  7  and other cables  8  used, the more drag the vessel  1  and the streamers  2  experience. Drag increases fuel and vessel power requirements.  
           [0008]    Another drawback of conventional techniques is that to connect the various components of conventional cable configurations, the cables  7 ,  8 , are cut and then spliced together. This includes the stress bearing members, the seismic data conductors, and the electrical power conductors. By cutting and then splicing, the mechanical integrity of the cable is compromised, and the cables become more susceptible to fatigue and/or manufacturing process induced failure. Also, if optical fibers are used for transmitting the data from the sensors to the vessel, each splice will attenuate the signal and will give a substantial loss in signal level.  
           [0009]    Thus, there is a long felt need for an improved method and system for towing streamers which increases reliability, reduces components, reduces structural, electrical, and optical splices, and that creates less drag than conventional techniques.  
         SUMMARY OF INVENTION  
         [0010]    In one aspect the invention comprises a system and a method for marine geophysical exploration, which includes a first cable connected to a vessel and a plurality of streamer cables connected to the first cable. The first cable includes all towing strength members and all electrical power and data transmission conductors for the connected streamer cables.  
           [0011]    In another aspect the invention comprises a system and a method for marine geophysical exploration in which a vessel tows a first cable that includes at least one strength member and a plurality of electrical power and data conductors. A plurality of streamer cable connection locations are provided on the first cable, and a first connector assembly is affixed to the first cable at a first streamer cable connection location. At least one electrical power conductor and at least one data conductor included in the first cable is connected by means of the first connector assembly to a first streamer cable, and at least one electrical power conductor and at least one data conductor are extended continuously past the first streamer cable connection location to at least a second streamer cable connection location. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]    [0012]FIG. 1 illustrates a conventional streamer configuration from a top view.  
         [0013]    [0013]FIG. 2 shows an aerial view of two lead-in and manifold cables of the present invention.  
         [0014]    [0014]FIG. 2A shows an aerial view of an alternate configuration of two lead-in and manifold cables of the present invention.  
         [0015]    [0015]FIG. 3 shows a cross-section of a first embodiment of a lead-in and manifold cable of the present invention.  
         [0016]    [0016]FIGS. 4 and 5 show anchoring elements assembled around a center stress core.  
         [0017]    [0017]FIG. 6 shows a compression collar as it is assembled around anchoring elements on a center stress core.  
         [0018]    [0018]FIG. 7 shows a side view cross-section of an implementation of the present invention.  
         [0019]    [0019]FIG. 8 shows the “break-out” of optical fibers and electrical conductors from a manifold and lead in cable for assembly of a streamer tow terminal.  
         [0020]    [0020]FIG. 9 is a further illustration of the assembly of a streamer tow terminal.  
         [0021]    [0021]FIG. 10 shows still a further assembly of a streamer tow terminal.  
         [0022]    [0022]FIG. 11 shows still another view of a streamer tow terminal.  
         [0023]    [0023]FIG. 12 shows a cross-sectional view of an alternate embodiment of a lead-in and manifold cable.  
         [0024]    [0024]FIG. 13 is an illustration of the assembly of a streamer tow terminal for the lead-in and manifold cable of FIG. 12.  
         [0025]    [0025]FIG. 13A shows a detail of the assembly of the embodiment shown in FIG. 13.  
         [0026]    [0026]FIG. 14 is a further illustration of the assembly of a streamer tow terminal for the lead-in and manifold cable of FIG. 12.  
         [0027]    [0027]FIG. 15 is a cross-sectional view of yet another embodiment of a leadin and manifold cable.  
         [0028]    [0028]FIG. 16 is a cross-sectional view of still another embodiment of a lead-in and manifold cable.  
         [0029]    [0029]FIG. 17 is a schematic view of a streamer tow for the embodiment of the invention shown in FIG. 16.  
         [0030]    [0030]FIG. 18 illustrates a fairing as used with the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0031]    [0031]FIG. 2 shows an aerial view of two cables  10  according to the present invention towing five streamers  2  each. Each cable  10  is both a lead-in and a manifold cable, providing power to and signal reception from a plurality of seismic streamers  2 . That is, the cable  10  leads from the vessel  1  to the first streamer (designated with the reference  2   a ) and extends beyond the first streamer  2   a  to provide a connection location for each of the other streamers  2 . By contrast, conventional cable configurations use multiple cables to perform the function of a single unitary lead-in and manifold cable  10  of the present invention.  
         [0032]    In FIG. 2, each streamer  2  is connected to a cable  10  with a streamer tow terminal  11 . It should be noted that the cable  10  is a lead-in and manifold cable. The lead-in, or trunk portion,  60  of the cable  10  comprises the portion of the cable  10  extending from the vessel  1  to the first streamer tow terminal  11  for the first streamer  2   a . The manifold portion  50  of the cable  10  comprises the portion of the cable  10  extending beyond the first streamer tow terminal  11  for the first streamer  2   a  to the paravane  3 .  
         [0033]    In one embodiment, the lead-in and manifold cable  10  runs continuously from vessel to the paravane  3 , as illustrated in FIG. 2. In an alternate embodiment, the lead-in section of cable  10  is connected to the manifold section of cable  10  by connector  14 , as shown in FIG. 2A, by connection techniques known to those of ordinary skill in the art. In either configuration, the lead-in and manifold cable  10  is spread out using the paravane  3  to draw the lead-in and manifold cable  10  and the streamers  2  out horizontally, giving the desired lateral coverage. Thus, the present lead-in and manifold cable  10  provides a configuration for towing multiple streamers  2  with a tow vessel  1 , which requires fewer cable segments and fewer connections between various cable segments, than multiple streamer tow configurations known to the prior art.  
         [0034]    [0034]FIG. 3 shows a cross-section of a first embodiment of the lead-in and manifold cable  10 . The lead-in and manifold cable  10  has a center stress core  30 , which will serve as a strength member. The center stress core  30  comprises metal wire, a metal rope, an armored rope, Kevlar (Kevlar is a registered trademark of E. I. Du Pont de Nemours and Company), aramid fiber, and/or other material that will occur to those of ordinary skill in the art. Surrounding the center stress core  30  is an inner jacket  25  comprising, for example, plastic, and/or any other suitable material that will occur to those of ordinary skill in the art.  
         [0035]    Optical fibers  20  and electrical conductors  15  are wound around the jacket  25  in a helical direction. Optical fibers  20  may be in the form of a stainless steel loose tube, a plastic loose tube, a tight-buffered fiber matrix, or other forms known to those of ordinary skill in the art. By winding the optical fibers  20  and the electrical conductors  15  in a helical direction, the optical fibers  20  and electrical conductors  15  are subjected to less stress when tension is placed on the lead-in and manifold cable  10 . Each bundle of optical fibers  20  and each electrical conductor  15  are routed to a specific streamer  2 . The optical fibers carry control signals to and data from a specific streamer  2 , and the electrical conductors transmit power to a specific streamer  2 . For example, if eight streamers  2  are used, optical fibers  20  and electrical conductors  15  for at least eight individual streamers  2  are provided in the cable  10 . Typically, at least two electrical conductors  15  and at least four optical fibers  10  (included in one tube) per streamer are provided in the lead-in and manifold cable  10  for each streamer  2 . This includes at least two optical fibers for telemetry and at least two optical fibers for multiplexed auxiliary data and at least one electrical conductor  15  for each polarity of the power supply. A typical power supply voltage is, for example, 1,000 V dc.  
         [0036]    To protect the optical fibers  20  and the electrical conductors  15 , at least one layer of armor  40  surrounds the optical fibers  20  and electrical conductors  15 . The armor  40  protects the optical fibers  20  and electrical conductors  15  from damage caused by impact, such as the streamers  2  colliding with one another, damage caused by rolling the streamers  2 , or impact from various objects or animals out at sea. However, in this first described embodiment, the armor  40  does not provide substantial tensile strength for the cable  10 . The armor  40  comprises Kevlar, aramid fibers, metal, plastic, and/or any other suitable material that will occur to those of ordinary skill in the art. Conductor belt  26 , which may be formed from plastic or other suitable material, is positioned between armor  40  and optical fibers  20  and electrical conductors  15  in order to protect the optical fibers  20  and electrical conductors  15  from abrasion by armor  40 . The assembly of the cable is completed by the application of the outer jacket  34 . Outer jacket  34  may be formed from plastic or other suitable material, and is utilized to retard abrasion of the armor  40 .  
         [0037]    Streamers  2  are connected to the lead-in and manifold cable  10  by means of streamer tow terminals  11 . FIGS.  4 - 11  illustrate a particular implementation of the streamer tow terminal  11 . The lead-in and manifold cable  10  is continuous (uninterrupted) as it passes each streamer cable tow terminal  11 . At each streamer tow terminal  11 , only the optical fibers  20  and electrical conductors  15  that are routed to the streamer connected to that particular tow terminal are “broken out”. The optical fibers  20  and electrical conductors  15  that are not routed to that specific streamer  2  are continuous, that is, they are not cut and then spliced, but are routed through the terminal, uninterrupted, to the next tow terminal. The center stress core  30  is also continuous, and passes uninterrupted through the tow terminals  11 . With reference to FIGS. 4 and 5, in accordance with a first embodiment, a button  17 , which may be a substantially cylindrical metallic sleeve is hexagonally swaged onto the center stress core  30  during the assembly process for cable  10  at each connection location from which it is desired to tow a streamer cable. In one implementation of the invention, after a button  17  is swaged onto the center stress core, the button will have a hexagonally shaped exterior. However, button  17  may have a shape other than hexagonal, so long as the button provides an appropriate mounting base for stress anchor  18 . As illustrated in FIGS. 4 and 5, stress anchor  18  is then assembled around button  17 . Stress anchor  18  is assembled from two mating sections  18 A and  18 B, as shown in FIG. 4, which may be substantially mirror images of each other. The interior surface of stress anchor  18  is configured to form a mating engagement with the hexagonal exterior surface of button  17 , to maintain the rotational position of the anchor with respect to the stress core  30 . The elevated ridges (router grooves)  19  on stress anchor  18  provide a mounting support for compression collar  23  (see FIG. 6), thereby creating space between stress anchor  18  and compression collar  23  for routing the optical fibers  20  and electrical conductors  15 . The router grooves  19  follow a generally helical pattern that the fiber optic cables  20  and the electrical conductors  15  follow as they are wound around the inner jacket  25  and center stress core  30 . Cable  10  is assembled with the optical fibers  20  and the electrical conductors  15  exterior to the stress anchor  18 , as shown in FIG. 6. The assembly of the cable is completed by the application of the conductor belt  26 , protective armor  40 , and outer jacket  34 .  
         [0038]    As described above, the anchoring elements (button  17  and stress anchor  18 ) are encased in the cable as the cable is assembled. To secure the tow terminal  11  to the lead-in and manifold cable  10 , the encased anchoring elements are exposed. As shown in FIG. 6, the outer jacket  34 , armor  40  are removed in the area adjacent the anchoring elements, and a segment of conductor belt  26  is opened to expose the anchoring elements.  
         [0039]    Compression collar  23  is then positioned around stress anchor  18 . As shown in FIG. 6 compression collar  23  is formed from compression collar elements  23 A and  23 B, which are interconnected with a tongue and groove mechanism, and compression collar elements  23 C and  23 D, which are similarly interconnected with a tongue and groove mechanism. Compression collar elements  23 A and  23 B are then mated with compression collar elements  23 C and  23 D and secured together with bolts  22 , as further illustrated in FIG. 7. Compression collar elements  23 A,  23 B,  23 C and  23 D each have curved under surfaces so as to engage the outer surface of stress anchor  18 . The shear pins  21 , which are inserted into receptacles in elevated ridges  19 , extend upwardly from elevated ridges  19  and engage corresponding apertures in the compression collar  23  to maintain the rotational position of the compression collar  23  with respect to cable  10 , and to assist in maintaining the axial position of the compression collar  23  with respect to cable  10 . Compression collar elements  23 A and  23 B are secured to compression collar elements  23 C and  23 D with bolts  22 , to maintain compression collar elements  23 A and  23 B in compressive engagement with stress anchor  18 . Button  17 , stress anchor  18  and compression collar  23  form a mounting assembly for tow terminal  11 .  
         [0040]    [0040]FIG. 7 shows a cross-section of the button  17 , stress anchor  18 , and compression collar  23  assembled onto the stress core  30  of lead-in and manifold cable  10 .  
         [0041]    As illustrated in FIG. 8, dedicated ones of the optical fibers  20  and electrical conductors  15  are “broken out” at each streamer tow terminal  11 . Typically, at least two electrical conductors  15  and at least four optical fibers  20  (typically included in one loose tube) are broken out for connection into each steamer cable  2 . As shown in FIG. 8, the exterior armor  40  is severed and terminated on either side of the connection location for assembling streamer tow terminal  11  onto the cable  10 . As indicated by the dotted lines in FIG. 8, a helical strip  31  of the conductor belt  26 , following the path of the optical fibers  20  and electrical conductors  15  to be “broken then out” is removed in order to permit a length of the electrical conductors  15  and the optical fibers  20  to be broken out as shown in FIG. 8. An overmold  41  is then formed around conductor belt  26  which will cover and seal the area where the helical strip was removed. As shown more clearly in FIG. 7, the overmold  41  material also fills the void spaces in the region where button  17 , stress anchor  18  and compression collar  23  are assembled around the inner stress core  30  in order to provide a water proof seal for the interior of cable  10  at the location of the streamer tow terminal  11 . The overmold  41  is typically formed from the same material as the conductor belt  26 . With reference to FIG. 8, the electrical conductors and optical fibers are broken out through periscope  45 , which is formed into the overmold. Sealing boot  47 , which may be formed from the same material as conductor belt  26 , is applied over the electrical conductors  15  and optical fibers  20  at the point where they exit the periscope  45  for sealing purposes in order to prevent water from getting into the core of the cable.  
         [0042]    The armor  40  is then secured around overmold  41  on each side of the streamer tow terminal location with bands  43 , which may be stainless steel or other corrosion resistant metal. Potting cups (not shown) are installed over the armor terminations of each side of the tow terminal, and a wire lock is applied to the ends of the armor, which may be an epoxy resin and diatomaceous earth material, or other similar material to form armor terminations  40 A.  
         [0043]    [0043]FIG. 9 shows a portion of the streamer tow terminal  11 , including torsion bar  90 . A first end of torsion bar  90  is mated, typically with bolts or screws (not shown), with torsion bar clamp  92  in compressional engagement with armor termination  40 A. The other end of torsion bar  90  is bolted or otherwise affixed to compression collar  23 . Torsion bar  90  provides structural stability to prevent the two portions of split outer housing  80  (see FIG. 10) from rotating with respect to each other Splice tray  84  is secured to torsion bar  90  by means of screws  93 . The optical and electrical conductors are omitted from FIG. 9 for clarity. However, with reference to FIGS. 9 and 10, the optical fibers and electrical conductors that are broken out are extracted through sealing boot  47  and are connected to corresponding optical fibers and electrical conductors in the swivel connector  98  by which a streamer cable  2  is connected to a tow terminal  11 . The optical fibers that are broken out extend from sealing boot  47  to splice tray  84 , which is utilized for splicing together, by standard means known to those of ordinary skill in the art, the optical fibers broken out from the lead-in and manifold cable  10  with corresponding optical fibers extending to swivel connector  98 .  
         [0044]    [0044]FIG. 10 shows in cross-section the split outer housing  80  assembled at each end of the streamer tow terminal  11 , with the connector collar  82  extending between the two sections of the split outer housing. Split outer housing  80  is assembled from four components,  80 A,  80 B,  80 C and  80 D. Mating housing components  80 A and  80 B are affixed by way of keying pins (not shown) to the keyways  86  in the elevated ring of torsion bar  90  (and torsion bar clamp  92 ) to form one end of split outer housing  80 , and mating components  80 C and  80 D are mounted onto compression collar  23  to form the other end of split outer housing housing  80 . The interior surfaces of split outer housing elements  80 C and  80 D have a pattern of grooves and ridges that mate with the corresponding pattern of the compression collar  23 . Split outer housing elements  80 A and  80 B, and split outer housing elements  80 C and  80 D are assembled together by means of bolts and guide pins such as those identified by numeral  94  in FIG. 10. The projecting pins in split locking ring  72  are installed into the pattern of grooves and ridges in housings  80 C and  80 D and compression collar  23 , maintaining rotational position of housings  80 C and  80 D with respect to cable  10 . Locking stud  74  is then installed to maintain axial position of housing elements  80 C and  80 D with respect to cable  10 . A connector collar  82  is then assembled around the two sections of split outer housing by means of a tongue and groove connection, to enable rotational movement of the connector collar with respect to the split outer housing  80 . Such rotational movement is desirable because it permits proper rotational orientation of the streamer cable with respect to lead-in and manifold cable  10  to be established prior to beginning towing operation. After the desired orientation is established, set screws  88  are utilized to fix the rotational orientation of the attached streamer cable  2  to the lead-in and manifold cable  10 . With reference to FIG. 10 the tongue portion  61  extends from connector collar  82  into groove portion  62  of split outer housings  80 . Connector collar  82  includes a swivel connection, described further below, by which a streamer cable  2  is mechanically connected to tow terminal  11  and cable  10 .  
         [0045]    With reference to FIG. 10, each half of connector collar  82  includes an extension  83 , which includes an aperture  55  for providing a swivel connection between the tow terminal  11  and streamer  2 . As shown in FIG. 10, pivot arm  96  includes pivot studs  95  (only one of which is visible in FIG. 10) which are inserted into bushings (not specifically shown) in apertures  55 . Electrical conductors are routed from the periscope  45  through pivot arm  96  to swivel connector  98 , and optical fibers are also routed from the periscope, via the splice tray  84 , to swivel connector  98 , by standard techniques known to those of ordinary skill in the art. A mating connector (not shown) connects corresponding optical fibers and electrical conductors extending within streamer  2  to the optical fiber and electrical conductor terminations in swivel connector  98 , as the streamer  2  is attached to terminal  11  by threaded engagement with threaded connection  97 .  
         [0046]    [0046]FIG. 11 shows assembled streamer tow terminal  11 , which further includes a protective bellows  100 . Bellows  100  is affixed for the purpose of deflecting debris. Bellows  100  is attached to connector collar extension  83  by means of bellows clamp  102 , and a bolt (not visible in FIG. 11) which attaches the bellows to extension  83  on the underside of bellows  100 .  
         [0047]    In the embodiment described with reference to FIGS.  4 - 11 , the streamer tow terminal  11  allows the center stress core  30 , and all of the uninterrupted fiber optic cables  20  and electrical conductors  15  to pass through—uncut and unspliced—to their assigned streamer cable. Only the individual fiber optic cables  20  and electrical conductors  15  that are connected into the streamer attached to a tow terminal  11  are cut and then spliced into the streamer  2 . That is, only the optical fibers  20  or electrical conductors  15  assigned to the specific streamer  2  are “broken out.” The remainder of the optical fibers  20  and conductors  15  are uninterrupted and will continue to the next streamer tow terminal  11  at the next streamer  2 , where again, only the specific optical fibers  20  and electrical conductors  15  assigned to that specific streamer  2  are “broken out.” 
         [0048]    Returning to FIG. 2, at the end of the lead-in and manifold cable  10 , a simple mechanical termination  27  is installed to connect the lead-in and manifold cable  10  directly to the paravane  3 . Typical mechanical terminations comprise a bolt, a preformed termination, and/or any other termination that will occur to those of ordinary skill in the art. Such terminations  27  are widely known to those of ordinary skill without further explanation.  
         [0049]    In another embodiment of the invention, the external armor also functions as a strength bearing element. A cross-section of this embodiment of the invention is shown in FIG. 12, in which cable  10  includes a center stress core  30  comprising Kevlar, aramid fibers, metal, alloy, armor, and/or any other suitable material. A jacket  25  comprising plastic and/or any other suitable material surrounds the center stress core  30 . Wrapped around the jacket  25  are fiber optic cables  20  and electrical conductors  15 . Conductor belt  26  surrounds the optical cables and electrical conductors. The external armor  40  is shown as comprising two layers to indicate its greater strength bearing capacity. Typically, no outer jacket will be utilized because of the additional cable diameter resulting from utilizing a strength member as the external armor  40 .  
         [0050]    The connection mechanism for attachment of cable  10  according to this second embodiment of the invention is similar to the tow connector described with respect to FIGS.  4 - 11 , except that the mounting assembly elements (button  17 , stress anchor  18  and compression collar  23 ) are not utilized. Instead, as shown in FIG. 13, torsion bar  90  extends for substantially the length of the tow terminal  11 , and elevated ring  90 A of torsion bar  90  and torsion bar clamp  92  are interconnected with armor  40  as more clearly described with reference to FIG. 13A. FIG. 13A shows a detail of the assembly of the embodiment shown in FIG. 13. A potting cup, including an inner portion  116  and an outer portion  114  is positioned around the severed ends of armor  40 . The potting cup; is then interconnected with elevated ring  90 A of torsion bar  90  and torsion bar clamp  92  (not shown in FIG. 13A) by a tongue  120  and groove  118  configuration. Potting cup  116 ,  114  may be formed from an epoxy resin and diatomaceous earth material. Similarly, as shown in FIG. 14, split outer housing elements  80 C and  80 D are mounted onto the lower end of the torsion bar  90  and split outer housing elements  80 A and  80 B are mounted onto the upper end of the torsion bar  90  in substantially the same manner as split outer housing elements  80 A and  80 B are mounted onto the upper end of the torsion bar  90  in FIG. 10.  
         [0051]    Designated optical fibers and electrical conductors are extracted from the cable  10  and connected to the streamer cable  2  in the same manner as for the previously described embodiment. As in the previously described embodiment, only the optical fibers and electrical conductors designated for connection to the specific streamer are “broken out”. The center stress core  30  passes uninterrupted through each connection location for each streamer cable  2  from the vessel  1  to the paravane  3 . The rest of the fiber optic cables  20  and electrical conductors  15 , and the center stress core  30 , pass uninterrupted past the location of the streamer tow terminal  11 . As with the previously described embodiment and illustrated in FIG. 2, at the end of the manifold section  50  of the cable  10 , the center stress core  30  is fitted with a typical mechanical termination  27  and connected to the paravane  3 . Mechanically, in this second embodiment, the external armor  40  supports the load put on the cable  10  by the streamer  2 , and the center stress core  30  supports the load put on the cable  10  by the paravane  3 .  
         [0052]    A benefit to this embodiment is that the center stress core  30  carries the load put on the cable  10  by the paravane  3 , and the load put on the cable  10  by the streamers  2  is carried mostly by the external armor  40 . Thus, the load carrying elements (armor  40  and center stress core  30 ) of the cable  10  are substantially separate. Where the streamer loads are expected to be comparatively low (e.g., 6 tonnes) the armor  40  material comprises, for example, standard plow steel, Kevlar, or other load-bearing material, which may havea more limited towing capacity than is required from the stress core, which carries the load of the paravane.  
         [0053]    The use of both the center stress core  30  and the armor  40  as a strength member causes an increase in the diameter of cable  10 . Therefore, according to still a further embodiment of the invention, the lead-in and manifold cable  10  has yet another design. In this embodiment the center stress core is not utilized and the external armor/strength member carries all the lift of the paravane and the weight and drag of the streamer cables. FIG. 15 shows a cross-sectional view of this embodiment. Looking at the cable  10  from the outside in, the cable  10  comprises a double layer of external armor  40  comprising Kevlar, aramid fibers, metal and/or any other suitable material that will occur to those of ordinary skill in the art. Beneath the external armor  40  are fiber optic cables  20  and the electrical conductors  15 , which are grouped into individual bundles  105 . An independent sheath  110  covers the fiber optic cable  20  and electrical conductors  15  of each bundle  105  to facilitate easy identification of which fiber optic cables  20  and electrical conductors  15  are to be broken out at each streamer  2 .  
         [0054]    In this third embodiment, the streamer connection terminal  11  is the same as described for the second embodiment with reference to FIGS. 13 and 14, except the diameter of the lead-in and manifold cable  10  will be smaller because there is no center stress member, and the elements of the streamer tow terminal  11  can be smaller in scale.  
         [0055]    In yet another embodiment, as shown in cross-section in FIG. 16, the strength bearing member  30 A and the optical fibers  20  and electrical conductors  15 , of lead-in and manifold cable  10 , are not in a concentric configuration with respect to each other. Instead, the optical fibers  20  and electrical conductors  15  are encapsulated in a rubber sleeve  104 , that extends along, but is external to, the strength bearing member  30 A, which is surrounded by a rubber sleeve  103 . An abrasion-resistant molding  106  extends around both the strength bearing member  30 A and the optical fibers  20  and electrical conductors  15 . With reference to FIG. 17, normally, fairings  112  are positioned along the molding  106 . The fairings  112  are adapted to limit bending of the strength member  30 A and optical fibers  20  and electrical conductors  15 , as well as to streamline the flow of the cable  10  through the water. FIG. 18 illustrates a fairing  112  that may be located along the cable  10  between the streamer tow terminals  111  to reduce the drag on the cable  10 . In some examples, the fairing  112  comprises a simple canvas fairing or a semi-rigid fairing. In other examples, the armor itself is shaped as a fairing. Other fairings will occur to those of ordinary skill without departing from the invention  
         [0056]    In order to attach tow connector  11  to this embodiment of the lead-in and manifold cable  10 , a button  17 A is swaged or otherwise affixed onto the strength member  30 A as shown in FIG. 17. Although not shown in detail in FIG. 17, the tow connector  11  may be configured substantially as described for the embodiment of the invention described with reference to FIGS.  4 - 11 , except that the configuration of the various elements of tow connector  11  will need to be adapted to fit the cross-section of lead-in and manifold cable  10 , as shown in FIG. 16.  
         [0057]    The various examples of the invention are not limited to use in steamer operations. Alternate embodiments are used anywhere a number of sensors or sensor modules are used, or where it is an advantage to reduce the number of cables or cable splices (for example, ocean bottom cable systems, dragged array systems, vertical array systems, or any other system that will occur to those ordinary skill in the art).  
         [0058]    Although described here as fiber optic cables  20 , in alternate embodiments, the seismic data conductors for transmitting signals from the receivers to the vessel comprise steel wires, copper wires, alloy wires, cables, and/or any other seismic data conductor that will occur to those of ordinary skill in the art.  
         [0059]    The invention has been described with a certain degree of particularity, however, many changes may be made in the details without departing from the scope of the invention. It is understood that the invention is not limited to the embodiments set forth herein, but is to be limited only to the scope of the attached claims, including the full range of equivalency to which each element thereof is entitled.