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  Wavelength division multiplexed (wdm) ring passive optical network (pon) with route protection for replacement of splitter based passive optical networksUSPTO Application #: 20070201873Title: Wavelength division multiplexed (wdm) ring passive optical network (pon) with route protection for replacement of splitter based passive optical networks Abstract: A method and apparatus for low cost upgrading on demand of an optical fiber communication system without installing additional optical fiber and minimal installation of optical circuitry at destination and distribution terminals. The upgraded systems comprise an optical data loop of a plurality of destination terminals and a single intermediate terminal. (end of abstract)
Agent: Baker Botts L.L.P. - Dallas, TX, US Inventors: George H. Buabbud, Muneer Zuhdi, Ulrich Trick, Thomas Volk, Debra D. Wawro USPTO Applicaton #: 20070201873 - Class: 398066000 (USPTO) Related Patent Categories: Optical Communications, Multiplex, Broadcast And Distribution System The Patent Description & Claims data below is from USPTO Patent Application 20070201873. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application is a continuation application of U.S. application Ser. No. 11/088,070 filed on Mar. 23, 2005 and now U.S. Pat. No. 7,212,541, which is a continuation of U.S. patent application Ser. No. 09/876,439 filed on Jun. 6, 2001 now U.S. Pat. No. 6,898,206, the entire disclosure of each being hereby incorporated herein by reference. TECHNICAL FIELD OF THE INVENTION [0002] The present invention relates to methods and apparatus associated with broadband communications using optical fibers as the transmission media, and more specifically to methods and apparatus for on-demand upgrading of an existing optical network system with the capacity to service additional subscribers with broadband digital service with no installation of additional optical fibers and minimal replacement of existing infrastructure. BACKGROUND OF THE INVENTION [0003] The telecommunications industry is using more and more optical or light fibers in lieu of copper wire. Optical fibers have an extremely high bandwidth thereby allowing the transmission of significantly more information than can be carried by a copper wire. The carried information includes broadband digital data carrying digital television signals, computer data, etc. [0004] Of course, modern telephone systems require bidirectional communications where each station on a communication channel can both transmit and receive. This is true, of course, whether the system uses electrical wiring or optical fibers as the transmission medium, and whether the information is simple analog voice or broadband digital signals. Early telephone communication systems solved this need by simply providing separate copper wires for carrying the communications in each direction. Some early attempts at using optical fibers as a transmission medium followed this example and also used two different optical fibers such as optical fibers 10 and 10A in the prior art FIG. 1 for carrying the communications in each direction. As shown, in the prior art FIG. 1, fiber 10 is connected by an optical coupler 12 to an LED (light-emitting diode) 14 at one end and by optical coupler 16 to a PD (photodetection diode) 18 at the other end. Similarly, but in reverse, fiber 10A is connected by an optical coupler 16A to PD 18 at one end and by optical coupler 12A to LED 14 at the other end. [0005] However, because of the extremely high bandwidths capable of being transmitted by an optical fiber, a single fiber is quite capable of carrying communications in both directions. One technique is WDM (wavelength divisional multiplexing) which is shown in the prior art FIG. 2 and uses different wavelengths for each direction of travel. Components in FIG. 2 and subsequent FIGUREs which operate the same as shown in FIG. 1 carry the same reference numbers. In the embodiment shown in FIG. 2, a central office 20 is connected to an immediate or RT (remote terminal) 22 by at least one pair of optical fibers 10B. The remote terminal 22 may be further connected to a multiplicity of destination terminals by other pairs of optical fibers. As shown, the central office includes a light-emitting diode 14 optically connected to fiber optics 10 by optical coupler 12 for converting electrical signals to optical signals and a photodetection diode 18A optically connected to optical fiber 10A by a coupler 16A for converting optical signals to electrical signals. The fiber optics 10 and fiber optics 10A are each connected to a wavelength division multiplexer 24 which in turn is connected by optical coupler 26 to optical fiber 10B. This arrangement is duplicated at the RDT 22 by light-emitting diode 14A, photodetection diode 18, and wavelength division multiplexer 24A. It will, of course, be appreciated that although the FIGURE is shown as providing communications between a central office 20 (station 1) and a remote terminal office 22 (station 2) prior to being further distributed to a multiplicity of destinations, the communications system could be used for providing communications between any two types of stations, examples include communication between two central offices, two remote terminal offices, or between a remote office and an individual user's location, etc. A typical communications system using an LED (light-emitting diode) and a PD (photodiode) with a single optical fiber is disclosed in U.S. Pat. No. 5,075,791 entitled "Method and Apparatus for Achieving Two-Way Long-Range Communication Over an Optical Fiber", issued to Mark W. Hastings, and incorporated in its entirety hereby by reference. [0006] Yet another technique for using a single optical fiber 10 for telephone systems is illustrated in the prior art FIG. 3. The illustrated FIGURE is referred to as TCM (time compression multiplexing). The system operates at a single frequency and uses a single optical fiber 10 and a single diode 30 and 30A at each end connected by optical couplers 32 and 32A, respectively, for both converting electrical signals to optical signals and for receiving optical signals and converting those optical signals to electrical signals. TCM systems have the obvious advantage of requiring fewer components. [0007] Still other and more advanced systems carry telephony communication (either analog or digital) at one wavelength of light and television signals (digital and/or analog) at another wavelength. SUMMARY OF THE INVENTION [0008] However, as mentioned above, optical fibers have extremely high bandwidths and use of an optical fiber for any of the above-mentioned existing systems is a very ineffective use of the fiber and, in fact, the available bandwidth of an optical fiber makes it possible to use both active and passive optical transmission techniques which can be used to carry a significantly-increased number of individual bidirectional broadband communication channels or signals. [0009] Of course, where early types of optical transmission systems have been installed, it is desirable to limit the time the operation of such systems is disrupted. Further, once an early type fiber-optic telephone system is installed, wholesale removal and replacement with a new system would normally be prohibitive from a cost point of view. Therefore, it would be advantageous to be able to upgrade on a demand basis an existing fiber-optic system to also carry a significantly increased number of broadband communication channels. [0010] Disclosed herein is a system for communicating optical data to and from an optical distribution terminal having an optical communication device including an optical fiber data output and an optical fiber data input. The system includes a plurality of remote optical interface units defining at least a first remote optical interface unit and a last remote optical interface unit. Each remote optical interface unit has an optical fiber data input and an optical fiber data output. The optical fiber data input of the first remote optical interface unit and the optical fiber data output of the last remote optical interface unit are respectively configured to be connected to the optical fiber data output and the optical fiber data input of the optical communication device. The remaining optical fiber data inputs of the plurality of remote optical interface units are connected to the remaining optical fiber data outputs of the plurality of remote optical interface units. BRIEF DESCRIPTION OF THE DRAWINGS [0011] For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts, in which: [0012] FIG. 1 is a block diagram of a prior art fiber optical communication system using two fibers to obtain bidirectional communication; [0013] FIG. 2 is a block diagram of another prior art bidirectional fiber-optic communication system using a single transmission fiber having a light-emitting diode and a photodetection diode at each end of the fiber; [0014] FIG. 3 is a block diagram of a prior art fiber optical communication system using a single fiber and a single transmit/receive diode at each end suitable for TCM; [0015] FIG. 4 is a schematic of a prior art Passive Optical Fiber distribution network suitable for being upgraded by the teachings of this invention; [0016] FIG. 5 illustrates a first embodiment of the invention for upgrading the optical network of FIG. 4 to an active optical network with minimal new equipment and without the installation of additional optical fibers; [0017] FIG. 6 is an enlarged illustration of how the optical loop is formed between BOIU 66 and 68 and the corresponding pairs of optical fibers 50 and 52; [0018] FIG. 7 illustrates another embodiment of the invention wherein the prior art passive optical system is upgraded to handle a large number of broadband subscribers by using 4 wavelengths of light, but continues to operate as a passive optical system; [0019] FIGS. 8A and 8B illustrate how the route protection switches operate so as to limit the number of customers or subscribers affected in the event of a failure of an OIU in one of the destination terminals of either of the embodiments shown in FIGS. 6 and 7; Continue reading... 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