Abstract:
A fiber optic cable is disclosed, a fiber optic cable containing multiple optical fibers within an enclosure, where the fibers are divided into two groups, the first group of fibers being arrayed together and the second group being free fibers. The arrayed fibers are used to carry signals that are desired to be maintained in synchronization with each other, while the free fibers are used to carry signals whose synchronization with other signals is not important. In one example, four optical fibers form a linear array, and two free optical fibers are arranged on two sides of the linear array.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a data transmission cable using optical fibers and having electrical connectors at both ends, and related fabrication methods. 
       SUMMARY OF THE INVENTION 
       [0002]    The present invention is directed to a connecting device for a fiber optic cable for converting electrical signals and optical signals to each other, and a cable device having a fiber optic cable and such connecting devices at both ends. 
         [0003]    Additional features and advantages of the invention will be set forth in the descriptions that follow and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings. 
         [0004]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention provides a fiber optic cable containing multiple optical fibers within an enclosure, where the fibers are divided into two groups, the first group of fibers being arrayed together and the second group being free fibers. The arrayed fibers are used to carry signals that are desired to be maintained in synchronization with each other, while the free fibers are used to carry signals whose synchronization with other signals is not important. 
         [0005]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  schematically illustrates a connecting device for a fiber optic cable according to an embodiment of the present invention. 
           [0007]      FIG. 2  schematically illustrates a fiber optic cable device having two connecting devices at its ends according to an embodiment of the present invention. 
           [0008]      FIGS. 3A-3C  illustrate exemplary exterior views the connecting device of embodiments of the present invention. 
           [0009]      FIG. 4  is a cross-sectional view of a fiber optic cable according to another embodiment of the present invention. 
           [0010]      FIGS. 5A ,  5 B and  5 C illustrate previously disclosed connecting devices. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0011]    Chinese utility model patent application No. 201020599351.6, filed Nov. 4, 2010 and granted on Jul. 20, 2011 as CN 201903673 U (hereinafter “the CN &#39;673 patent”), is herein incorporated by reference in its entirety.  FIGS. 1 ,  5   a  and  8   f  of the CN &#39;673 patent are reproduced as  FIGS. 5A ,  5 B and  5 C of the present application. The disclosure of the CN &#39;673 patent is summarized briefly below. 
         [0012]    The CN &#39;673 patent describes a connecting device for use with an optical fiber cable for data transmission. As shown in  FIGS. 5A ,  5 B and  5 C ( FIGS. 1 ,  5   a  and  8   f  of the CN &#39;673 patent), one end of the connecting device is provided with an electrical connector  1  which complies with a standard format such as HDMI (High Definition Multimedia Interface), VGA (Video Graphics Array), DP (DisplayPort), DVI (Digital Visual Interface), etc. The other end of the connecting device accommodates an optical fiber cable or optical fiber bundle. Various components are contained in a housing of the connecting device and mounted on a circuit board  2 , and function to convert electrical signals from the electrical connector  1  into optical signals transmitted onto the optical fibers  3 , and to convert optical signals from the optical fibers  3  into electrical signals transmitted onto the electrical connector  1 . These internal components include, in the example shown in  FIGS. 5A and 5C , a chip electrically connected to the electrical connector  1 , for processing electrical signals; an optical transceiver block (not shown in  FIGS. 5A and 5C ) having multiple individual optical transceivers, electrically connected to the chip, for converting optical signals to electrical signals and vice versa; an optical component positioning block  4 , for positioning the optical transceivers to the circuit board; a lens block  5 , positioned on the optical component positioning block  4 , for focusing and reflecting light signals between the optical transceivers and the optical fibers; and an optical fiber positioning block  6 , for positioning the optical fibers to the lens block  5 .  FIG. 5A  shows a state where the optical fiber positioning block  6  is not yet aligned with the lens block  5 ;  FIG. 5C  shows a state where the components are assembled an placed inside the housing but the top cover of the housing is still open. The example shown in  FIG. 5B  is similar to the example shown in  FIG. 5A  except that the multiple individual optical transceivers are directly mounted on the optical component positioning block  54  which faces the optical fiber positioning block  56 , and the lens block is omitted. 
         [0013]    Embodiments of the present invention improves the connecting device described in the CN &#39;673 patent by separating the various internal components, which are contained in a single housing in the CN &#39;673 patent, into two groups and arrange them in two separate housings. An embodiment of the present invention is schematically illustrated in  FIG. 1  of the present disclosure. 
         [0014]    As shown in  FIG. 1 , the connecting device  100  includes a first part  110  and a second part  120  adapted to be electrically and mechanically connected to each other. The first part  110  has a first electrical connector  111  and a second electrical connector  112  disposed on a housing  113 . The first connector  111 , which may be referred to as the external connector of the connecting device  100 , is preferably one that complies with a standard format such as HDMI, VGA, DP, DVI, etc., similar to the electrical connector  1  of the previously disclosed connector device shown in  FIGS. 5A-5C . Contained inside the housing  113  are one or more electrical components such as a chip  114  for processing electrical signals. The chip  114  is electrically connected to the first electrical connector  111  by a first set of wires  115 , and to the second electrical connector  112  by a second set of wires  116 . The chip and the wires may be formed on a circuit board enclosed in the housing  113 . 
         [0015]    The second part  120  of the connecting device  100  has a first electrical connector  121  disposed on a housing  122 . The first electrical connector  121  is designed to electrically and mechanically connect with the second electrical connector  112  of the first part  110 . The connectors  112  and  121  are not required to comply with any commonly recognized standard, so long as they can mate with each other. Contained inside the housing  122  are an optical transceiver block  123  including a plurality of optical transceivers (such as laser diodes (LD) and/or photo detectors (PD)), and an optical fiber positioning block  124  for receiving and positioning a set of optical fibers  125  from an optical fiber cable  127 . The optical transceivers, which are electrically connected to the first electrical connector  121  by a set of wires  126 , convert optical signals to electrical signals and vice versa. The optical fiber positioning block  124  positions the end of the optical fibers  125  relative to the optical transceivers such that light signals are transmitted between the optical transceivers and the optical fibers. Either the optical transceiver block  123  or the optical fiber positioning block  124  or both may include optical elements such as lenses, reflectors, etc. to direct the light signals. Preferably, the optical fibers  125  include multiple fibers for transmitting various signals. In one example, six optical fibers are used for transmitting HDMI signals, four of which carry the Tc, T0, T1 and T2 signals, and two carry the SCL, SDA, HPD, CEC, and ARC signals in a multiplexed manner. The chip  114  carries out the necessary multiplexing/demultiplexing functions. 
         [0016]    The optical transceiver block  123  and the optical fiber positioning block  124  may have any suitable structures. In one example, the optical transceiver block  123  has a structure similar to the combined structure of the an optical component positioning block  4 , the a lens block  5 , and the optical transceiver block shown and described in  FIGS. 5A and 5C . In another example, the optical transceiver block  123  has a structure similar to the optical component positioning block  54  shown and described in  FIG. 5B . In one embodiment, the optical fiber positioning block  124  has a structure similar to the optical fiber positioning block  6  shown and described in  FIG. 5A , or the optical fiber positioning block  56  shown and described in  FIG. 5B . Other suitable structures may be used as well. 
         [0017]    In the previously disclosed structures shown in  FIGS. 5A-5C , the optical transceivers are electrically connected to the chip by wires. In effect, the embodiment shown in  FIG. 1  of the instant disclosure divides the components of shown in  FIGS. 5A-5C  into two groups at the location of these wires, and locate the two groups of components in two separate housings with appropriate electrical connector to connect the two. Preferably, in embodiments of the present invention, most or all electrical signal processing circuitry, including generating drive signals for the laser in the optical transceiver, is located in the first housing, so the second housing contains very little or no electrical signal processing circuitry, enabling the size of the second housing to be minimized. All components related to transmitting and processing of optical signals are located in the second housing. The connection between the two housings only involves electrical connection. 
         [0018]    In the embodiment illustrated in  FIG. 1 , the first electrical connector  111  for the first part  110  is a male connector, but it may also be a male connector. Further, the second electrical connector  112  of the first part  110  is a female connector and the first electrical connector  121  of the second part  120  is a female connector, but the reverse structure may be used. 
         [0019]      FIG. 2  illustrate an embodiment of the present invention which is a cable device  101  having an optical fiber cable  127  and two connecting devices  100 ,  100 A at its two ends. Typically, the two connecting devices  100 ,  100 A are not identical because one end of the cable device  101  is primarily a transmitting end and the other end is primarily a receiving end (even though different signals may be transmitted in different directions simultaneously). In the example shown in  FIG. 2 , each connecting device  100 ,  100 A is formed of two parts as described above. Alternatively, one connecting device (e.g.  100 ) may be formed of two parts while the other (e.g.  100 A) may be formed of a single part similar to that of the previously disclosed connector device shown in  FIGS. 5A-5C . 
         [0020]    The external connectors  111  and  111 A and the electronic components within the connecting devices  100  and  100 A may be the same or different. When they are different, the cable device may function as an adaptor or converter, which converts electrical signals complying with one standard to electrical signals complying with a different standard. When the two external connectors  111  and  111 A are the same or comply with the same standard, the cable device may function as an extender or connector cable to connect two external devices located remotely with respect to each other. For example, one practical application of the cable device  101  is an HDMI to HDMI fiber optic connector for connecting a TV at one end (the receiving end) and a DVD player or another source device at the other end (the transmitting end). 
         [0021]    In one particular example, the cable device  101  is an adaptor with an Apple Lightening connector, or an Apple 30-pin connector, or an MHL (Mobile High-Definition Link) connector at one end, and an HDMI connector at the other end. Such a cable will allow an Apple device such as iPad™, iPhone™ and iPod™ or other mobile devices to be connected to an HDTV or other HDMI-compatible display device, so that the images seen on the mobile device can be displayed on the screen of the HDTV or the other HDMI-compatible device. Lightening and 30-pin are two types of connectors used by various versions of Apple&#39;s iPad™, iPhone™ and iPod™ devices. MHL is a standard mobile audio/video interface. The signal conversion schemes between Lightening, 30-pin or MHL and HDMI are known, as Lighting connector to HDMI adaptors, 30-pin connector to HDMI adaptors and MHL to HDMI adaptors are known and commercially available from various sources, even though these adaptors use electrical rather than optical cables for signal transmission. In such an adaptor cable, either the Lightening or 30-pin connector, or the HDMI connector, or both, may be made as a two-part structure by implementing embodiments of the present invention. 
         [0022]    Referring back to  FIG. 1 , forming the connecting device  100  in two parts  110  and  120  offers many advantages. First, by locating the electrical components  114  and the external connector  111  in a detachable first part  110 , the second part  120  contains very little or no electrical signal processing circuitry; thus, the size of the second part  120  can be reduced, so that it can be much smaller than the previously disclosed connector device shown in  FIGS. 5A-5C . For example, the size of the second part  120  can be smaller than 0.35 by 0.25 by 0.75 inches. When connecting two external devices located remotely to each other, the cable device  101  often needs to be passed through narrow passages in a building, such as conduit inside walls of the building. To pass through a pipe having a limited size, the first part  110  can be detached, and the second part  120  with the cable  127  can be passed through the pipe more easily. For example, many older residential buildings have pipes of 0.5 inches in diameter with 90 degree turns. It would have been very difficult or impossible to pass the previously disclosed connector shown in  FIGS. 5A-5C  through such conduit, whereas the second part  120  of the embodiments of this invention can easily pass through such conduit. After the second part  120  is passed through the conduit, the first part  110  is attached to the second part  120  and the connecting device  100  is ready to be connected to an external device. 
         [0023]    Second, in the embodiment of the present invention shown in  FIG. 1 , the first part  110  of the connecting device  100  contains only electrical components and no optical components. Therefore, it can be fabricated more easily and reliably using mature technologies, which reduces the cost of the overall cable device. 
         [0024]    Further, because the connection (i.e. connectors  112  and  121 ) between the first part  110  and second part  120  is s pure electrical connection without involving any optical signals, the connection is not prone to problems relating to connecting two optical fibers. 
         [0025]    It should be noted that  FIGS. 1 and 2  of the instant disclosure are only intended as schematic illustrations; they do not necessarily represent the actual shape, size or spatial arrangements of the various components. For example, while the fibers  125  are shown in  FIG. 1  as being fanned out, they are not limited to this configuration, and they may go straight out to the LD or PD. 
         [0026]      FIGS. 3A-3C  illustrates exemplary exterior views of the connecting device  100  according one particular embodiment of the present invention.  FIG. 3A  shows the two parts  110  and  120  being uncoupled from each other, and  FIG. 3B  shows the two parts being coupled to each other.  FIG. 3C  illustrates the front, side and top views of the connecting device  100 . 
         [0027]      FIG. 4  is a cross-sectional view illustrating a fiber optic cable according to an embodiment of the present invention, which can be used as the cable  127  in  FIGS. 1 and 2 . As mentioned earlier, HDMI signals may be transmitted via six optical fibers, with four fibers carrying the Tc, T0, T1 and T2 signals and two fibers carrying the various other signals (SCL, SDA, HPD, CEC, and ARC). In the embodiment shown in  FIG. 4 , the four fibers  201 A to  201 D that carry the Tc, T0, T1 and T2 signals are formed into a fiber array by aligning the four fibers together side by side with a suitable adhesive material  202 . The two other fibers  201 E and  201 F which carry the other data are not formed into the same fiber array as the first four fibers. In other words, each of fibers  201 E and  201 F is free and not adhered to any other fibers, and its location with respect to the other fibers is not fixed and may shift as the cable is moved. The six fibers  201 A to  201 F are enclosed by a protecting enclosure  203  to form the fiber optic cable. 
         [0028]    The fiber arrangements described above has certain advantages. Because the Tc, T0, T1 and T2 signals are required to be synchronized as much as possible, the four fibers carrying these signals should be formed into an array so that the changes in their relative lengths are minimized when the cable bends or is coiled up. When multiple fibers are formed into an array, such as shown in  FIG. 4  (four fibers  201 A to  201 D forming an array), the array can be easily bend in one direction but not in the other (perpendicular) direction. In the example shown in  FIG. 4 , when the fibers  201 A- 201 D extend perpendicular to the plane of the paper, the array can be easily bent in the up-down direction, but not the left-right direction due to the four fibers being adhered to each other side by side in the left-right direction. Thus, reducing the size of the fiber array will make the cable easier to handle. In the embodiment shown in  FIG. 4 , only four fibers are arrayed together, and the other two fibers  201 E and  201 F can shift their positions within the enclosure  203  as the cable  200  is bent. The two free fibers can in fact move and fill in the “void” within the enclosure  203  which helps to reduce the strain on the cable. This arrangement balances the need to have the four fibers carrying the Tc, T0, T1 and T2 signals arrayed to maintain signal synchronization, and the need to make the cable easier to handle. If, on the other hand, all six fibers are formed into an array, the resulting array will be larger, making the cable more difficult to bend in the left-right direction and therefore harder to handle. 
         [0029]    In the example illustrated in  FIG. 4 , six fibers are shown with four being arrayed together. This is suitable for transmitting HDMI signals. Depending on the requirements of the signals being transmitted, a different number of fibers may be arrayed and a different number of fibers may be free. The general principle is that only fibers carrying synchronized signals should be arrayed and the other fibers should be free. 
         [0030]    It will be apparent to those skilled in the art that various modification and variations can be made in the connecting device and related methods of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations that come within the scope of the appended claims and their equivalents.