Abstract:
Apparatus and methods for maintaining balanced communication channels evenly even with heavy increases in service demands are disclosed. The apparatus uses an arrangement of jumpers and unique connection panes which allow rapid changes in the distribution of similar circuits to achieve balanced loads.

Description:
This application is a continuation of U.S. patent application Ser. No. 09/412,416, filed Oct. 5, 1999, the entire disclosure of which is incorporated herein by reference. 
    
    
     
       BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to methods and apparatus for use in a distribution cabinet of an optical communication system, and more specifically to distribution apparatus which allows the addition on demand of substantially a maximum number of electrical RF (radio frequency) user channels onto a wavelength carrier at a specific wavelength before being required to add another optical transmitter for generating a carrier at a different wavelength. That is, the addition of an optical generator for generating a specific wavelength may be substantially delayed until the optical wavelength carrier in use is almost to saturation. This is done without substantial downtime by making simple terminal connections between the existing panels.  
           [0003]    2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98  
           [0004]    The communications industry is using more and more optical or light fibers in lieu of copper wire. Optical fibers have an extremely high bandwidth thereby allowing significantly more information than can be carried by a copper wire transmission line such as twisted pairs or coaxial cable. However, because of the different usage of cable modem transmissions in various neighborhoods (commonly referred to as penetration), there may be some areas either business or residential where the penetration is almost one hundred percent. That is, almost every household path (HHP) will require the use of a cable modem transmission whereas other neighborhoods may be at substantially zero penetration.  
           [0005]    However, just because an area may be at zero penetration at one point in time suggests that the growth rate in that area may be very rapid, and a need exists so that such rapid grown can be handled quickly and inexpensively without the major addition of new equipment and without significant downtime to the customer.  
         SUMMARY OF THE INVENTION  
         [0006]    The above objects and advantages are achieved in the present invention by distribution apparatus in an optical communication system which allows the addition on demand of substantially a maximum number of cable modem transmission user channels with minimum downtime and at no expense. In areas of low usage or low penetration, an optical fiber may carry a single wavelength of light which is modulated by RF signals around a center wavelength of light of about 1550 nanometers. The same optical fiber carrying the 1550 nanometers of light will typically also be capable of carrying other wavelengths of lights which have center wavelengths close to the 1550 nanometers but somewhat displaced so as to have good isolation between the signals. For example, if it were desirable to carry three different wavelengths of light, the center frequencies might be selected to be 1545 nanometers, 1550 nanometers, and 1555 nanometers. The use of three different wavelengths of light as discussed will provide ample separation such that there is no cross talk or interference between the different wavelengths of light. In fact, up to eight different and specific wavelengths of light may be selected around the base wavelength referred to as 1550. Each of these different eight wavelengths may be referred to as A such as λ 1 , λ 2 , λ 3 , λ 4 , λ 5 , λ 6 , λ 7 , and λ 8 . The 1550 nanometers of light which is considered a base wavelength is selected to minimize the transmission loss of the optical fibers. Certain ones of the most used optical fibers will typically have transmission characteristics such that certain wavelengths are highly desirable as center wavelengths such as, for example, 1550 nanometers, 1310 nanometers, and 960 nanometers of light. However, to understand how eight different wavelengths of light around the 1550 nanometer length can exist at the same time may best be understood by thinking of the 1550 nanometers being one of the best possible wavelengths for transmission over the optical fiber, yet 1545 and 1555 nanometers also are very efficient transmissions. Therefore, so long as there is sufficient separation between the various wavelengths of light such that there is no cross talk or interference from each of the various wavelength transmissions, there is sufficient bandwidth to readily handle a large number of customers such as, for example, 768 cable modem customers. The novel apparatus of this invention which allows such flexibility, comprises a first group of combining circuits each of which has a plurality of inputs and a single output. Each of the combining circuit inputs is capable of receiving an input signal on each one of the plurality of input terminals. The plurality of input signals which may be of different frequencies are then directly combined by the combining circuits and provided as an output signal made up of these combined received input signals on the single output terminal. In a preferred embodiment, the plurality of inputs and the single output terminate in an SMB-type coax connector. Further, each one of the inputs may itself be carrying signals from up to at least 24 HHP&#39;s (household paths) or cable modem customers. The inputs to the input terminals are provided by a multiplicity of input cables each of which may be carrying, as mentioned above, up to at least 24 different channels or signals from 16 different cable modem customers. Each one of the input cables will also terminate with an SMB connector suitable for mating with the SMB connectors on the first group of combining circuits. There is also a second group of combining circuits similar to the first group in that they also have a plurality of inputs and a single output. Each one of the second group of combining circuits receives one of the outputs from one of the first group of combining circuits and then, as in the same manner as with respect to the first group of combining circuits, combines these inputs to produce a combined output signal which is made up of all of the output signals received from the first group of combining circuits. The inputs of this second group of combining circuits is also a first type of connector, such as an SMB connector as discussed above.  
           [0007]    Then, depending upon the level of penetration, the output of the second group of combining circuits may go directly to an optical transmitter which generates light over a frequency band at a very select center wavelength around 1550 nanometers of light. Alternately, the output from the second group of combining circuits goes to a third or final combining circuit. The final combining circuit, in the same manner as the first and second groups of combining circuits, receives the output from the second group of combining circuits as input signals and combines these signals into a final or modulation output signal which is used to modulate the wavelength of light generated by the optical transmitter.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    These and other features of the present invention will be more fully disclosed when taken in conjunction with the following Detailed Description of the Invention in which like numerals represent like elements and in which:  
         [0009]    [0009]FIG. 1 is a distribution cabinet or other support structure showing apparatus as used in the present invention;  
         [0010]    [0010]FIG. 2 shows the densely aligned panels or combining circuits of the present invention;  
         [0011]    [0011]FIGS. 3A and 3B show the side and front views of a type of combining circuit having eight similar input connectors and a single output connector;  
         [0012]    [0012]FIGS. 4A and 4B show another type of panel similar to FIG. 3A and 3B except that it has two independent combining circuits each of which has four inputs and a single output;  
         [0013]    [0013]FIGS. 5A, 5B, and  5 C show still another type of combining circuit which produces a final or modulating output going to the light generator for modulating the specific wavelength of light. According to one embodiment, each of these combining circuits has four inputs of one type connector and a single output of a different type connector;  
         [0014]    [0014]FIGS. 6A and 6B show a typical type arrangement and connections for the apparatus of this invention for a distribution area with low penetration or user demand;  
         [0015]    [0015]FIG. 7 is a simplified schematic showing the HHP (household path) inputs (individual modem user) through the distribution apparatus of this invention to the light generation and modulation circuit which produces the light having a specific wavelength such as 1545 nanometers and referred to in this example as λ 1 . This figure is representative of the low penetration of FIGS. 6A and 6B;  
         [0016]    [0016]FIGS. 8A and 8B show the apparatus of this invention connected in a manner suitable for an average amount of cable modem users or medium penetration;  
         [0017]    [0017]FIGS. 9A and 9B show the apparatus of the present invention arranged for use in an area of high penetration; and  
         [0018]    [0018]FIG. 10 shows a block diagram schematic of portions of the apparatus of this invention as it may be arranged for medium or high penetration.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Referring now to FIG. 1, there is shown a distribution cabinet or other support structure  10  supporting the distribution apparatus of the present invention. According to the embodiment shown, there are sixteen distribution panels  12 - 42  having eight inputs and a single output. In addition, there are four dual distribution panels  44  through  50  making eight total distribution circuits each of which has four inputs and a single output. Also shown are eight optical transmitters for generating eight different and specific wavelengths of light λ 1 -λ 8  having reference numerals  52 - 66 . Also shown is a power supply  70  for providing power to the optical transmitters. It will also be appreciated that a fan  71  could be included for keeping the rack and the equipment cool.  
         [0020]    Referring now to FIG. 2, there is shown a larger and more detailed view of the twenty different panels  12 - 50  shown in FIG. 1 and which contain the various types of combining circuits.  
         [0021]    As shown, each of the panels or combining circuits  12 - 42  include eight input terminals or connectors  12 A- 12 H and a single output connector  12 . Since each of the panels  12 - 42  is identical, only one will be discussed. Also as shown, each of the panels  12 - 42  as well as each of the dual panels  44 - 50  according to the present embodiment include a securing bolt  72  which secures the densely arranged panels  12 - 50  to the rack area or pocket  73 . Also shown attached to the rack area or pocket  73  are mounting brackets  74  and  76  for mounting the rack area to the support structure.  
         [0022]    Referring now to FIG. 3A, there is shown a side view and a front view of panel  12 . As was discussed above, the purpose of the panel containing the combining circuit is to receive signals on the input connectors  12 A- 12 H and provide an output on the output connector  12 . Thus, there is a copper path from the connector  12 A to  12 . It will also be appreciated, by those skilled in the art, that since the electrical paths from the input connectors  12 A- 12 H as well as the output path going to connector  12  are all carrying signals having a frequency in the megahertz range, the conductive path should maintain a constant impedance such that there will not be an impedance mismatch with the resulting signal attenuation and reflection. In the embodiment shown, the conductive paths maintain a 75-ohm impedance between the inputs  12 A- 12 H and the output  12  such as commonly required by coaxial cable. In the embodiment shown in FIGS. 3A and 3B, the input connectors  12 A- 12 H are SMB connectors as is the output connector  12 . It will also be appreciated that if necessary the paths could be made to have a different constant impedance path.  
         [0023]    Referring now to FIGS. 4A and 4B, there is shown a side view and a front view of another combining circuit similar to that of FIGS. 3A and 3B except the combining circuit of this Figure is a dual combining circuit. According to this embodiment, each one of the dual circuits includes four inputs  78 ,  80 ,  82 , and  84  and a single output  86 . The panels shown in FIGS. 4A and 4B are typically used in areas of low penetration where these panels represent the second combining circuits which go to a third and final combining circuit. According to this embodiment, all the input connectors are SMB as are the output connectors, although it will be appreciated that other types of connectors are still within the scope of this invention.  
         [0024]    Referring now to FIGS. 5A, 5B, and  5 C, there is shown a side view of a panel with two different front views. Panels  5 A and  5 B are substantially the same as that discussed with respect to FIGS. 4A and 4B except the output connectors  98  and  100  are of the larger, sturdier type “F” type coax connector. The face plate or front view of FIG. 3 shows an alternate embodiment wherein only one of the combining circuits on the panel is used since that there are only four inputs and a single output  100 .  
         [0025]    Referring now to FIGS. 6A and 6B, there is shown a simplified block diagram of the electrical cable connections between the panels containing the combining circuits of the present invention. In this particular embodiment, the 8-input/1-output panels are divided into four groups of four panels each, these groups are referred to as  102 ,  104 ,  106 , and  108 . Referring again to FIG. 2, it can be seen that each one of the panels  12 - 42  can receive eight inputs to provide one output. In the embodiment shown, the connections are for a low penetration area and as shown the first group  102  of panels has no inputs that is, these panels are not being used. However, in the second group, there are 20 inputs from 20 separate distribution panels coming into the four panels. As an example only, panel  20  is shown as receiving eight inputs, panel  22  six inputs, panel  24  four inputs, and panel  26  two inputs. Since each one of the panels  20 - 26  does receive at least two inputs and up to eight inputs, each one of these panel outputs provides an input to the panel  44 B. It should be noted, of course, that with respect to panels  12 - 18 , which receive no inputs, there is no need to make connections between these panels and the 4-input/1-output panel  44 A as is indicated by the “X”  107 . In a similar manner, groups  106  and  108  receive 32 inputs for the four panels or eight inputs per panel. Thus also as was the case with the group  104 , each one of the panels  28 - 34  and  36 - 42  provides a single output to the four inputs of the 4-to-1 combining panel  46 A and  46 B. Thus, as was discussed, since each one of the panels  44 A,  44 B,  46 A, and  46 B may receive up to four inputs each, they will each be capable of providing a single output to the 4-to-1 combining panel  48 A, which will in turn combine the inputs and provide a single output to the optical transmitter  52  to modulate the specific wavelength of light λ 1 .  
         [0026]    To better illustrate the connections, FIG. 7 shows an overall schematic diagram of an input from a single ONU (optical network unit) to the light generator  52 . The light generated by generator  52  is modulated with all of the signals on that path. As shown, the HHP&#39;s (household paths) or user inputs are provided to a distribution panel referred to as ONU No.  1  and provides one of the inputs to the 8-to-1 distribution on combining circuit  20 . In a similar manner, although not shown, there are six ONU&#39;s  9 - 18  providing inputs to six of the inputs on combining circuit  22 . The outputs of each of the combining circuits  20  and  22  are then provided to one portion of the dual 4-to-1 combining circuits  44 A and  44 B. The output of this circuit  44 B is then provided to one of the inputs of the circuit  48 A as are inputs from the other 4-to-1 combining circuits  44 A,  46 A, and  46 B. As shown, the output of the combining circuit  48 A is provided to the light generator  52  for modulating the wavelength of light λ 1 . Most arrangements assume about 96 users or different modems can be handled by any one of the single wavelengths of light λ-λ 8 . Consequently, a single rack of 20 different panels such as shown in FIG. 2 can handle up to approximately 768 customers by using eight different wavelengths of light λ 1  through λ 8 . However, the rack may actually be able to receive a higher number of HHP&#39;s such as, for example 2016.  
         [0027]    Referring now to FIGS. 8A and 8B, there is shown a block diagram schematic for a medium penetration arrangement. As shown in this embodiment, the 8-to-1 combining circuits  16 ,  18 ,  24 ,  26  are not used as indicated by the “X” through these panels. Thus as shown in FIG. 8A, the two panels  12  and  14  of group  102  provide outputs to two of the inputs to a final combining circuit  44 . It will be recalled that the 8-to-1 combining circuits  16 ,  18 ,  24 , and  26  are not being used in the illustrated embodiment. Likewise, half of each of the circuits  44 ,  46 ,  48 , and  50  are shown as not being used by means of the “X” through these circuits. Thus, the outputs from panels  12  or  14  are provided as two inputs to the final combining circuit  44  which output is then provided as an input to light generator  52  which produces a specific wavelength λ 1  modulated by the output of combining circuit  44 . Similarly, the two outputs from panels  20  and  22  are provided to two of the four inputs of the 4-to-1 combining circuit  46  which in turn provides a modulating output to light generator  54  which produces a wavelength of light λ 2 . Also, each of the four panels in group  106  provides an input to panel  48  which then provides its single output to light generator  56  which produces a wavelength of light λ 3 . Finally, panels  36 - 42  provide four single outputs to the inputs of 4-to-1 combining circuit  50  which in turn provides a single modulating output to light generator  58  which generates a wavelength of light λ 4 .  
         [0028]    For a high penetration area, and as shown in FIGS. 9A and 9B, each one of the 8-to-1 combining circuits produces one output such that each of the final combining circuits  44 A,  44 B,  46 A,  46 B,  48 A,  48 B,  50 A, and  50 B each receive two inputs and provide one output to their respective light generators  52 - 56  to modulate wavelengths of light λ 1 -λ 8 .  
         [0029]    Referring now to FIG. 10, there is shown a schematic connection of the panels  16 - 34  as used in the mid-penetration arrangement earlier shown in FIGS. 8A and 8B. It will also be appreciated that the connections shown for panels  16  and  18  of the 8-to-1 combining circuits and the panel  46  of the 4-to-1 combining circuits providing a single output to light generator  52 . This arrangement is the same as used in the high penetration arrangement for these panels shown in FIGS. 9A and 9B.  
         [0030]    The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed.