Abstract:
A system for delivering multiple passive optical network services is disclosed. The system includes a first optical transmission service comprising a common wavelength pair routed from a source to each of a plurality of subscribers. The system further includes a second optical transmission service comprising a plurality of unique wavelength pairs, where each of the unique wavelength pairs is routed from the source to a subscriber among the plurality of subscribers. The system delivers the first optical transmission service and the second optical transmission service to the subscriber on a single optical fiber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/000,753 filed Oct. 26, 2007, the disclosure of which is 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to delivery of passive optical network services, such as from an optical service provider to a home or business. More specifically, the present disclosure relates to methods and systems for delivery of multiple passive optical network services. 
     BACKGROUND 
     Passive optical networks are becoming prevalent in part because service providers want to deliver high bandwidth, communication capabilities to customers. Passive optical networks are a desirable choice for delivering high speed communication data because they may not employ active electronic devices, such as amplifiers and repeaters, between a central office and a subscriber termination. The absence of active electronic devices may decrease network complexity and cost and may increase network reliability. 
     Passive optical networks may take a signal from a single incoming fiber and make it available to a number of output fibers. For example, a distribution cable may include 24 optical fibers and may run from a central office to a distribution location, such as an equipment enclosure. At the equipment enclosure, each fiber in the distribution cable may be split into a number of outgoing fibers which are made available to subscribers. For example, passive optical networks may employ 1:2, 1:4, 1:8, 1:16 and 1:32 splitting ratios for each fiber, for making optical data available to subscriber locations. 
     In traditional gigabit passive optical network a single transmit wavelength and a single receive wavelength are used in each 1:32 split, requiring 32 subscribers to share bandwidth on a single fiber. However, in other systems, such as DWDM systems, dedicated wavelengths are used for each subscriber. Conversion between gigabit and DWDM systems requires substantial reconfiguration of the optical network to take advantage of the dedicated wavelength system. In certain instances, replacing wires leading to subscriber locations would be required. Such re-cabling is costly and time-consuming. 
     For these and other reasons, improvements are desirable. 
     SUMMARY 
     The above and other problems are solved in accordance with the present disclosure by the following: 
     In a first aspect, a system for delivering multiple passive optical network services is disclosed. The system includes a first optical transmission service comprising a common wavelength pair routed from a source to each of a plurality of subscribers. The system further includes a second optical transmission service comprising a plurality of unique wavelength pairs, where each of the unique wavelength pairs is routed from the source to a subscriber among the plurality of subscribers. The system delivers the first optical transmission service and the second optical transmission service to the subscriber on a single optical fiber. 
     In a second aspect, a method for delivering multiple passive optical network services is disclosed. The method includes splitting a first optical transmission service from source to a plurality of subscribers, the first optical transmission service including a common wavelength pair. The method further includes separating a second optical transmission service including a plurality of unique wavelength pairs onto a corresponding plurality of optical fibers, where each optical fiber receives a unique wavelength pair associated with a subscriber among the plurality of subscribers. The method also includes routing the first and second wavelengths of the first optical transmission service and the first and second wavelengths of the second optical transmission service to the subscriber on a single optical fiber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a typical network in which aspects of the present disclosure can be implemented; 
         FIG. 2  shows a schematic view of a system for delivery of multiple passive optical network services, according to one embodiment of the present disclosure; 
         FIG. 3  shows a schematic view of a system for delivery of multiple passive optical network services, according to a second embodiment of the present disclosure; and 
         FIG. 4  shows a schematic view of a system for delivery of multiple passive optical network services, according to a third embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the present invention will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the invention, which is limited only by the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the claimed invention. 
     In general, the present disclosure relates to delivery of multiple passive optical network services to a single endpoint, such as a household, a business, or other entity requiring a telecommunications connection to a distribution hub. The present disclosure describes a variety of passive optical network configurations which allow for selective use of one or more of the passive optical network services, thereby allowing selective upgrading of endpoints based on customer desires or requirements. The methods and systems of the present disclosure allow use of the same optical fibers already deployed to customer homes. 
     The present disclosure is designed to enable providers of data/video/voice services who have currently deployed fiber-to-the-premise (FTTP) distribution networks for those services, be able to upgrade customers to higher data rate &amp; bandwidth service(s) while maintaining the other services in their current delivery format. For example, a service provider may upgrade its data service to deliver individual customers with a 1 Gbps data line via a DWDM passive optical network (DWDM PON) while continuing to deliver voice and video to that same customer on its traditional gigabit PON (GPON). However, both would be delivered to the customer premise on the same already installed fiber. In this example, the service provider would not have to upgrade all of its delivery equipment to work with the new DWDM PON system but can use the fiber network that is already deployed in the field to deliver all of these services. 
     In various examples of the present disclosure, delivery of gigabit passive optical networks and DWDM passive optical networks are considered; however, deployment of additional types of optical networks is possible as well using the systems and techniques disclosed herein. For example the present disclosure also relates to delivery of other types of systems with different wavelengths and parallelism, such as WDM-PON and CWDM-PON. 
     Referring now to  FIG. 1 , a generalized network in which aspects of the methods and systems of the present disclosure may be implemented. The network  10  as shown is a passive optical network (PON) such as can contain various Fiber-to-the-premises (FTTP) systems. The network  10  connects a source  102 , such as a central office of a telecommunications provider, to various subscribers  104 , allowing the subscribers high speed data communications to other subscribers within the network and outside of the network (through other communication channels of the source). The network  10  includes a number of fiber optic components  103  that allow the network to route specific fiber optic signals to a subset of the entire subscriber base, thereby allowing the central office  102  to manage bandwidth concerns. The components can include, for example, splices, splitters, wavelength division multiplexers, repeaters, filters, and other optical components. These components may be modularly added or removed from the fiber optic system, such as by placing various combinations of such equipment in a fiber distribution hub or other modularly extensible system. The systems of the present disclosure breakout multifiber cable down to single fiber, limited wavelength spectra to allow a small number of users to share a particular available bandwidth. For example, in the case of gigabit PON, 32 subscribers  104  typically share a single wavelength for transmitting and receiving data with the source  102 . In the case of DWDM PON, each subscriber has a dedicated wavelength pair which it uses to communicate with the source  102 , thereby effectively increasing the bandwidth to that subscriber as compared to gigabit PON by eliminating competing traffic using that subscriber&#39;s communication wavelength. 
     Referring now to  FIGS. 2-4 , various systems for delivery of multiple passive optical network services are shown. These systems can be located within the network  10  of  FIG. 1 , and provide at least a portion of the connecting optical components used to connect a source  102  to subscribers  104 . 
     Referring now to  FIG. 2 , a schematic view of a system  100  for delivery of multiple passive optical network services is shown, according to one embodiment of the present disclosure. The system  100  connects optical fibers from a source  102 , shown as a central office or OLT, to one or more subscribers  104 , shown as customers or ONT connections. The system receives an initial distribution fiber  106  leading from the source  102 , on which all spectra of optical transmission coexist. 
     In the embodiment shown, the spectra of optical transmission include (1) a common wavelength pair and (2) a plurality of unique wavelength pairs. According to certain implementations the common wavelength pair is a 1310 nm wavelength and a 1490 nm wavelength used in gigabit passive optical network systems. In such systems, the 1490 nm wavelength is used to transmit data from the source  102  to all of the subscribers  104 , while the 1310 nm wavelength is used by all of the subscribers to transmit data back to the source. Other common wavelengths may be used as well with different types of optical services. 
     The unique wavelength pairs include a predetermined number of wavelength pairs, each of which connects to a single subscriber. By dedicating a wavelength pair to each subscriber, that subscriber will not need to share the bandwidth available for that wavelength pair with other subscribers on a passive optical network, thereby allowing for higher data rates due to parallel transmission of the different unique wavelength pairs. Selection of the various unique wavelength pairs is largely a matter of design choice; however, in a possible embodiment, the wavelength pairs are the corresponding C-Band and E-Band frequencies used in DWDM data transmission. 
     A wavelength division multiplexer  108  is connected to the fiber  106 , and separates the common wavelength signals from the unique wavelength signals. In the embodiment shown, the common wavelength gigabit PON signals (1310 and 1490 nm signals) are split to a fiber  110 , while the DWDM PON signals are split to fiber  112 . 
     The unique wavelength signals (e.g. DWDM PON signals) on fiber  112  are passed through a 1×N wavelength division multiplexer  114 , which separates the signals onto N different fibers. In the embodiment shown, there are N different DWDM PON signals on fiber  112 , and each of these signals is broken out onto a separate fiber  116   1-N . 
     The gigabit PON signals on fiber  110  are passed to a splitter  120 , which splits the signals into a corresponding number of optical fibers  122   1-N , each carrying the common wavelength pair signals. In the embodiment shown, the splitter  120  is a 1×N splitter, corresponding to the 1×N wavelength division multiplexer  114 . 
     Each of optical fibers  116   1-N  and  122   1-N  are passed into separate wavelength division multiplexers  124   1-N , (of which only WDM  124   1  and  124   N  are shown, for simplicity) which combine the common wavelength pair signals on the optical fibers  122   1-N  with each individual (and now separated) unique wavelength pair signal on optical fibers  116   1-N  to form subscriber lines  126   1-N , which carry both the common wavelength pair signals and one of the sets of unique wavelength pair signals to a subscriber  104  (e.g.  104   1  and analogously to other subscribers  104   2-N ). 
     Through use of the system  100 , a subscriber  104  therefore receives the common wavelength signals and one of the pairs of unique wavelength signals, allowing two different passive optical network services (e.g. gigabit PON and DWDM PON) to be delivered to the subscriber without requiring rewiring or additional wiring to the subscriber&#39;s premises. 
     Referring now to  FIG. 3 , a schematic view of a system  200  for delivery of multiple passive optical network services is shown, according to a second embodiment of the present disclosure. The system  200  generally corresponds to system  100  of  FIG. 2  in effect, but separates and recombines the common wavelength pair and unique wavelength pairs in a slightly different manner. Specifically, the optical fiber  106  leading from the source  102  connects to a 1×2 splitter  208 , which splits, but does not filter, the common wavelength pairs and the unique wavelength pairs onto optical fibers  110  and  112 . One path connects to a 1×N DWDM  214 , which filters out the common wavelength signal and also splits the unique wavelength signals onto N corresponding fibers  116   1-N , as previously described. The second path includes a filter  209  connected to the fiber  110 , which filters out the unique wavelength pairs, leaving only the common wavelength signal on a fiber  211  leading from the filter. The fiber  211  leads to a 1×N splitter  120  as previously described, which outputs the common wavelength signals onto fibers  122   1-N . The common wavelength signal, carried on each of fibers  122   1-N , is combined with each individual unique wavelength signal on the fibers  116   1-N  via 1×2 splitters  224   1-N . The splitters  224   1-N  are connected to output cables  126   1-N , which connect to subscribers  104   1-N . 
     Referring now to  FIG. 4 , a schematic view of a system  300  for delivery of multiple passive optical network services is shown, according to a third embodiment of the present disclosure. In this embodiment, the system  300  includes an AWG DWDM  350  connecting optical fiber  106  from the source  102  to the various subscribers  104   1-N . The AWG DWDM separates the unique wavelength signals, while allowing the common wavelength signals to pass to all of the output fibers  126   1-N  that lead to various customers  104   1-N . 
     Alternative designs exist in which multiple fibers are used leading from the source  104 . For example, in the systems of  FIGS. 2 and 3 , above, separate fibers could be used leading from the source  104  carrying the unique wavelength pairs to the wavelength division multiplexer  114 ,  214  and the common wavelength pairs to the splitter  120  of  FIGS. 2 and 3 , respectively. This would eliminate the need for the wavelength division multiplexer  108  of  FIG. 2  or the splitter  208  and filter  209  of  FIG. 3 . Other embodiments are possible as well which include different levels and combinations of splitters, filters, and wavelength division multiplexers. 
     In the embodiments shown in  FIGS. 2-4 , the systems for delivery of multiple passive optical network services are illustrated as passive optical modules. However, it is understood that the system can be configured from a number of separate components, and could include additional passive or active optical components. Furthermore, additional optical networking components can be incorporated into networks having the systems described herein. 
     Through use of the systems disclosed herein, a provider of passive optical network services can connect multiple services to a single subscriber location while avoiding the need to lay additional fibers to those locations. A provider or maintainer of an optical network such as are disclosed herein can install the splitters, filters, and wavelength division multiplexers as described herein to split a common wavelength pair into a number of fibers, and to separate unique wavelength pairs onto a corresponding number of fibers. The fibers carrying the common wavelength pair can be joined to each one of the fibers carrying different unique wavelength pairs to allow connection of a subscriber to either one or both services by using a single preexisting optical fiber connected to the subscriber. 
     The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.