Abstract:
A system, an unbundling optical line terminal (OLT), and a method are described herein that allow at least two service providers (SPs) to use individual fibers of an optical distribution network (ODN). In one embodiment, the unbundling OLT includes one or more wavelength division multiplexing-passive optical network (WDM-PON) line cards and one or more SP uplink cards that enable multiple SPs to each utilize one uplink port to access individual wavelengths of one or more passive optical networks (PONs). In another embodiment, the unbundling OLT includes one or more point-to-point line (p2p) line cards (e.g., p2p fiber Ethernet line cards) and one or more SP uplink cards that enable multiple SPs to each utilize one uplink port to access one or more individual fibers.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/440,551 filed on Feb. 8, 2011. The contents of this document are hereby incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a system, an unbundling optical line terminal (OLT), and a method for allowing at least two service providers (SPs) to use individual fibers of an optical distribution network (ODN). In one embodiment, the unbundling OLT includes one or more wavelength division multiplexing-passive optical network (WDM-PON) line cards and one or more SP uplink cards that enable multiple SPs to each utilize one uplink port to access individual wavelengths of one or more passive optical networks (PONs). In another embodiment, the unbundling OLT includes one or more point-to-point line (p2p) line cards (e.g., p2p fiber Ethernet line cards) and one or more SP uplink cards that enable multiple SPs to each utilize one uplink port to access one or more individual fibers. 
       BACKGROUND 
       [0003]    The following abbreviations are herewith defined, at least some of which are referred to within the following description of the prior art and the present invention. 
       AWG Arrayed Waveguide Grating 
     CPRI Common Public Radio Interface 
     C-VID Customer-VLAN ID 
     EPON Ethernet PON: IEEE 802.3ah 
     FTTH Fiber to the Home 
     GEM GPON Encapsulation Method 
       [0004]    GPON Gigabit-capable PON, ITU-T G.984 series 
       GbE Gigabit Ethernet 
     ID Identification 
       [0005]    MM Multi mode (fiber) 
       NetOp/NO Network Operator 
     ODF Optical Distribution Frame 
     OLT Optical Line Terminal 
     OIM Optical Interface Module 
     PON Passive Optical Network 
     Rx Receiver 
     SFP Small Formfactor Pluggable Optical Module 
       [0006]    SM Single Mode (fiber) 
       SP Service Provider 
     S-VID Service-VLAN ID 
     TDM Time Division Multiplexing 
     TRx Transceiver 
     Tx Transmitter 
     VLAN Virtual Local Area Network 
     WDM Wavelength Division Multiplexing 
     XPS Cross-point Switch 
       [0007]    In the emerging WDM-PON fiber access technology, one of the areas currently attracting a lot of interest relates to enhancing the capability of physical layer unbundling. Physical layer unbundling refers to a network architecture where multiple service providers (SPs) share a common data-link layer to provide voice, video and data services to subscribers. For example, physical layer unbundling allows different service SPs to use the individual wavelengths of a WDM-PON (fiber access network) to provide voice, video and data services to subscribers. In this way, improved competition in fiber access networks would be achieved as described in Broadtrends article: “Unbundling GPON: Bitstream Makes Most Sense . . . For Now” Jul. 6, 2010 (the contents of which are incorporated by reference herein). It is understood that physical layer unbundling, or using the more common term “Open Access”, implies a network operator (NetOp, also called NO) being responsible for the operation of the physical network plant and potentially also the physical layer active equipment. The network operator may or may not be the owner of the physical network and may or may not be a SP. 
         [0008]    The dominating technology today for fiber access is TDM-PON (EPON, GPON) where the subscriber access to multiple SPs is achieved by L 2  open access technologies (see the Broadtrends article).  FIG. 1  (PRIOR ART) is a block diagram illustrating the basic architecture of a GPON  100  utilizing an exemplary conventional L 2  open access technology. In this N: 1  VLAN scheme, each SP  102 - 1  . . .  120 -N uses a S-VID  104 - 1 .. 104 -N to represent them in the Access and Aggregation network  106  and a corresponding C-VID  108 - 1  . . .  108 -N to represent the end user service (voice, data, video). On the GPON&#39;s OLT  110 , each end user (ONT  112 - 1  . . .  112 -M in the FTTH case) is represented by a GEM-port  114 - 1  . . .  114 -M. The SP&#39;s S-VID  104 - 1  . . .  104 -N is mapped to the end user GEM-port  114 - 1  . . .  114 -M for transport over a PON  115 . At the ONT  112 - 1  . . .  112 -M, the end user  116 - 1  . . .  116 -M has access to the selected SP services. For simplicity, just one OLT  110  and one PON  115  from this OLT  110  has been shown. The problem with L 2  open access technologies is that the traffic of different SPs  120 - 1  . . .  120 -N need to come together and pass a common packet processing device (e.g., Ethernet switch or similar—located in OLT  110 ). This architecture where all SPs need to come together gives rise to trust issues in terms of security and fairness as well as some limitations when it comes to service differentiations within the OLT  110  or in an aggregation device upstream from the OLT  110 . 
         [0009]    Alternatively, TDM-PON can also provide subscriber access to multiple SPs using different L 1  open access technologies.  FIGS. 2A-2B  (PRIOR ART) are block diagrams illustrating the basic architectures of two WDM-PONS  200   a  and  200   b  utilizing exemplary conventional L 1  open access technologies. In  FIG. 2A , the WDM-PON  200   a  shows the case when the NO is the owner of the active and passive PON equipment  201  (including ONTs  202 - 1 .. 202 -M, wavelength multiplexers/demultiplexers  204  and  206 , an OEO  208  and an ODF  210 ) which connect SPs  212 - 1  . . .  212 -N to end users  214 - 1  . . .  214 -M. In this case, the NO has to use the ODF  210  and manually patch each SP interface to the OEO port (which translates the SP&#39;s optic which are wavelength un-specific to the specific PON wavelength representing an individual end user  214 - 1  . . .  214 -M). If desired, the NO can also make use of an optical switch to replace the manual patching, albeit at a very high cost. In  FIG. 2B , the WDM-PON  200   b  shows the case when the NO is the owner of the passive PON equipment  216  (including wavelength multiplexers/demultiplexers  218  and  220 , and an ODF  222 ) but not the active PON equipment  224  (including ONTs  226 - 1  . . .  226 -M) which connect SPs  228 - 1  . . .  228 -N to end users  230 - 1  . . .  230 -M. In this case, the SP- 1   228 - 1  (for example) has to provide the correct wavelength to the ODF  222 . This means that the SP  228 - 1  risks having unused expensive WDM-ports in case an end user  230 - 1  (for example) switches to another SP  212 -N (for example) or in a case the take rate is slow or unsuccessful. Plus, the SPs  228 - 1  . . .  228 -N need to have a substantial amount of GbE ports (if this is the line speed per wavelength) and corresponding patch cabling since each port represents one wavelength line (being in service or potentially coming onto service). In both WDM-PONs  200   a  and  200   b  it is evident that the number of optical patch cords (cabling) from each SP is substantial, which will increase even more with customer turn-over. Hence, there has been and still is a need enhance the capability of physical layer unbundling (Open Access). This need and other needs are satisfied by the present invention. 
       SUMMARY 
       [0010]    A system, an unbundling OLT, and a method for allowing at least two SPs to use individual fibers of an ODN are described in the independent claims of the present application. Advantageous embodiments of the system, the unbundling OLT, and the method are described in the dependent claims. 
         [0011]    In an aspect, the present invention provides a system comprising at least two SPs, a first unbundling OLT, and an optical ODN, wherein the first unbundling OLT is positioned between the at least two SPs and the ODN. The first unbundling OLT comprises a first line card, a backplane, and first uplink card, wherein the first uplink card is coupled by the backplane to the first line card. The first line card includes a multi-channel transmitter-receiver array and a plurality of L 1  switches, wherein the multi-channel transmitter-receiver array has a first side coupled to a first set of one or more ODN fibers associated with the ODN and a second side coupled to the plurality of L 1  switches, wherein each L 1  switch has one port on a first side connected to a port associated with one of the channels on the multi-channel transmitter-receiver array, and wherein each L 1  switch has multiple ports on a second side coupled to the backplane. The first uplink card is dedicated to a first SP and is connected by a first uplink port and a first link to the first SP, wherein the first uplink card includes a L 2  switch and an OIM, wherein the OIM has a first side connected to the first uplink port which is coupled via the first link to the first SP, wherein the OIM has a second side connected to a first side of the L 2  switch, wherein the L 2  switch has multiple ports on a second side connected to the backplane such that one of the ports on the L 2  switch is coupled via the backplane to one of the multiple ports on the second side of one of the plurality of L 1  switches in the first line card, and wherein the first uplink port is shared among all of the channels on the multi-channel transmitter-receiver array which are supported by the first set of one or more ODN fibers. The unbundling OLT enables fiber access physical layer unbundling for WDM-PON and p2p fiber Ethernet while minimizing the need for active (ports etc) and passive optics (patch cord, ODF ports etc) as well as reducing manual labor as a SP acquires or looses resources and subscribers in the access network. 
         [0012]    In another aspect, the present invention provides an unbundling OLT that is positioned between at least two SPs and an ODN. The unbundling OLT comprises a first line card, a backplane, and first uplink card, wherein the first uplink card is coupled by the backplane to the first line card. The first line card includes a multi-channel transmitter-receiver array and a plurality of L 1  switches, wherein the multi-channel transmitter-receiver array has a first side coupled to a first set of one or more ODN fibers associated with the ODN and a second side coupled to the plurality of L 1  switches, wherein each L 1  switch has one port on a first side connected to a port associated with one of the channels on the multi-channel transmitter-receiver array, and wherein each L 1  switch has multiple ports on a second side coupled to the backplane. The first uplink card is dedicated to a first SP and is connected by a first uplink port and a first link to the first SP, wherein the first uplink card includes a L 2  switch and an OIM, wherein the OIM has a first side connected to the first uplink port which is coupled via the first link to the first SP, wherein the OIM has a second side connected to a first side of the L 2  switch, wherein the L 2  switch has multiple ports on a second side connected to the backplane such that one of the ports on the L 2  switch is coupled via the backplane to one of the multiple ports on the second side of one of the plurality of L 1  switches in the first line card, and wherein the first uplink port is shared among all of the channels on the multi-channel transmitter-receiver array which are supported by the first set of one or more ODN fibers. The unbundling OLT enables fiber access physical layer unbundling for WDM-PON and p2p fiber Ethernet while minimizing the need for active (ports etc) and passive optics (patch cord, ODF ports etc) as well as reducing manual labor as a SP acquires or looses resources and subscribers in the access network. 
         [0013]    In yet another aspect, the present invention provides a method for allowing at least two SPs to use individual fibers of an ODN. The method comprises a step of: (a) positioning an unbundling OLT between the at least two SPs and the ODN. The unbundling OLT comprises a first line card, a backplane, and first uplink card, wherein the first uplink card is coupled by the backplane to the first line card. The first line card includes a multi-channel transmitter-receiver array and a plurality of L 1  switches, wherein the multi-channel transmitter-receiver array has a first side coupled to a first set of one or more ODN fibers associated with the ODN and a second side coupled to the plurality of L 1  switches, wherein each L 1  switch has one port on a first side connected to a port associated with one of the channels on the multi-channel transmitter-receiver array, and wherein each L 1  switch has multiple ports on a second side coupled to the backplane. The first uplink card is dedicated to a first SP and is connected by a first uplink port and a first link to the first SP, wherein the first uplink card includes a L 2  switch and an OIM, wherein the OIM has a first side connected to the first uplink port which is coupled via the first link to the first SP, wherein the OIM has a second side connected to a first side of the L 2  switch, wherein the L 2  switch has multiple ports on a second side connected to the backplane such that one of the ports on the L 2  switch is coupled via the backplane to one of the multiple ports on the second side of one of the plurality of L 1  switches in the first line card, and wherein the first uplink port is shared among all of the channels on the multi-channel transmitter-receiver array which are supported by the first set of one or more ODN fibers. The method also comprises the steps of controlling the plurality of L 1  switches to select one or more of the channels of the multi-channel transmitter-receiver array to be used by the first SP. The method further comprises the step of controlling the L 2  switch to enable the first uplink port of the first SP to use the first set of one or more ODN fibers associated with the ODN. The unbundling OLT enables fiber access physical layer unbundling for WDM-PON and p2p fiber Ethernet while minimizing the need for active (ports etc) and passive optics (patch cord, ODF ports etc) as well as reducing manual labor as a SP acquires or looses resources and subscribers in the access network. 
         [0014]    In still yet another aspect, the present invention provides an unbundling OLT positioned between at least two SPs and at least one PON. The unbundling OLT comprises a first line card, a backplane; and a first uplink card, wherein the first uplink card is coupled by the backplane to the first line card. The first line card includes a WDM multiplexer, a multi-channel transmitter-receiver array and a plurality of L 1  switches, wherein the WDM multiplexer has a first side coupled to a first PON and a second side coupled to a first side of the multi-channel transmitter-receiver array which has a second side coupled to the plurality of L 1  switches, wherein each L 1  switch has one port on a first side connected to a port associated with one of the wavelength channels on the multi-channel transmitter-receiver array, and wherein each L 1  switch has multiple ports on a second side coupled to the backplane. The first uplink card is dedicated to a first SP and is connected by a first uplink port and a first optical link to the first SP, wherein the first uplink card includes a L 2  switch and an OIM, wherein the OIM has a first side connected to the first uplink port which is coupled via the first optical link to the first SP, wherein the OIM has a second side connected to a first side of the L 2  switch, wherein the L 2  switch has multiple ports on a second side connected to the backplane such that one of the ports on the L 2  switch is coupled via the backplane to one of the multiple ports on the second side of one of the plurality of L 1  switches in the first line card, and wherein the first uplink port is shared among all of the wavelength channels on the multi-channel transmitter-receiver array which are supported by the first PON. The unbundling OLT enables fiber access physical layer unbundling for WDM-PON while minimizing the need for active (ports etc) and passive optics (patch cord, ODF ports etc) as well as reducing manual labor as a SP acquires or looses resources and subscribers in the access network. 
         [0015]    In still yet another aspect, the present invention provides an unbundling OLT positioned between at least two SPs and multiple fibers. The unbundling OLT comprises a first line card, a backplane, and a first uplink card, wherein the first uplink card is coupled by the backplane to the first line card. The first line card includes a multi-channel transmitter-receiver array and a plurality of L 1  switches, wherein the multi-channel transmitter-receiver array has a first side coupled to the multiple fibers and a second side coupled to the plurality of L 1  switches, wherein each L 1  switch has one port on a first side connected to a port associated with one of the wavelength channels on the multi-channel transmitter-receiver array, and wherein each L 1  switch has multiple ports on a second side coupled to the backplane. The first uplink card is dedicated to a first SP and is connected by a first uplink port and a first optical link to the first SP, wherein the first uplink card includes a L 2  switch and an OIM, wherein the OIM has a first side connected to the first uplink port which is coupled via the first optical link to the first SP, wherein the OIM has a second side connected to a first side of the L 2  switch, wherein the L 2  switch has multiple ports on a second side connected to the backplane such that one of the ports on the L 2  switch is coupled via the backplane to one of the multiple ports on the second side of one of the plurality of L 1  switches in the first line card, and wherein the first uplink port is shared among all of the wavelength channels on the multi-channel transmitter-receiver array which are supported by the multiple fibers. The unbundling OLT enables fiber access physical layer unbundling for p2p fiber Ethernet while minimizing the need for active (ports etc) and passive optics (patch cord, ODF ports etc) as well as reducing manual labor as a SP acquires or looses resources and subscribers in the access network. 
         [0016]    Additional aspects of the invention will be set forth, in part, in the detailed description, figures and any claims which follow, and in part will be derived from the detailed description, or can be learned by practice of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as disclosed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    A more complete understanding of the present invention may be obtained by reference to the following detailed description when taken in conjunction with the accompanying drawings: 
           [0018]      FIG. 1  (PRIOR ART) is a block diagram illustrating the basic architecture of a GPON utilizing an exemplary conventional L 2  open access technology; 
           [0019]      FIGS. 2A-2B  (PRIOR ART) are block diagrams illustrating the basic architectures of two WDM-PONs utilizing exemplary conventional L 1  open access technologies; 
           [0020]      FIGS. 3-5  are block diagrams of an exemplary system which includes one or more unbundling OLTs (including WDM-PON line cards, a backplane, and SP uplink cards) which are positioned between multiple SPs and multiple PONs in accordance with a first embodiment of the present invention; 
           [0021]      FIGS. 6-8  are block diagrams of an exemplary system which includes one or more unbundling OLTs (including p2p line cards, a backplane, and SP uplink cards) which are positioned between multiple SPs and multiple fibers in accordance with a second embodiment of the present invention; and 
           [0022]      FIG. 9  is a flowchart illustrating the basic steps of a method for allowing at least two SPs to use individual fibers of an ODN in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring to  FIG. 3 , there is shown a block diagram illustrating an exemplary system  300  including an exemplary unbundling OLT  302  positioned between multiple SPs  304 - 1 .. 304 -N and multiple PONs  306 - 1  . . .  306 -M (e.g., 48 channel GbE PONs  306 - 1  . . .  306 -M associated with ODF  307 ) in accordance with a first embodiment of the present invention. The unbundling OLT  302  includes one or more WDM-PON line cards  308 - 1  . . .  308 -M, a backplane  310 , one or more SP uplink cards  312 - 1 .. 312 -L (dedicated to SP- 1   304 - 1 ), and one or more SP uplink cards  314 - 1  . . .  314 -L (dedicated to SP-N  304 -N). The WDM-PON line cards  308 - 1  . . .  308 -M are interfaced with the PONs  306 - 1  . . .  306 -M. Plus, the WDM-PON line cards  308 - 1  . . .  308 -M are coupled by the backplane  310  to the SP uplink cards  312 - 1  . . .  312 -L and  314 - 1  . . .  314 -L. Each set of the SP uplink cards  312 - 1  . . .  312 -L and  314 - 1  . . .  314 -L are respectively coupled via one or more links  313 - 1  . . .  313 -K to one of the SPs  304 - 1  . . .  304 -N. 
         [0024]    The WDM-PON line cards  308 - 1  . . .  308 -M each include a WDM multiplexer  316 , a multi-channel transmitter-receiver array  318  (e.g., 48 channel DWDM Tx/Rx array  318 ), and multiple L 1  switches  320 - 1  . . .  320 -X (e.g., 48  1 :N XPSs  320 - 1  . . .  320 -X). As shown, the multi-channel transmitter-receiver array  318  has a first side  322  coupled via the WDM multiplexer  316  to the PON # 1   306 - 1  and a second side  324  coupled to the L 1  switches  320 - 1  . . .  320 -X. Each L 1  switch  320 - 1  . . .  320 -X has one port  326 - 1  . . .  326 -X on a first side  328  connected to a port  330 - 1  . . .  330 -X associated with one of the wavelength channels on the multi-channel transmitter-receiver array  318 . Plus, each L 1  switch  320 - 1  . . .  320 -X has multiple ports  332 - 1  . . .  332 -N on a second side  334  coupled to the backplane  310 , where each port  332 - 1  . . .  332 -N is associated with one SP  304 - 1  . . .  304 -N. 
         [0025]    In this example, the WDM multiplexer  316  (optical mux/demux component  316 , AWG  316 ) is hosted on each WDM-PON line card  308 - 1  . . .  308 -M to reduce optical patch cords. Plus, the multi-channel transmitter-receiver array  318  is in a common package to reduce the cost of the optical transmitters and receivers. For example, the common package can contain  12  channels or even all the channels (or more) of the corresponding PON  306 - 1  . . .  306 -M. Each electrical Tx/Rx port  330 - 1  . . .  330 -X of the multi-channel transmitter-receiver array  318  is connected to one of the  1 :N XPSs  320 - 1  . . .  320 -X which is used to select SP(s)  304 - 1  . . .  304 -N for each WDM-PON wavelength. The XPS performs switching on L 1  which is transparent to SP packets and protocols. The  1 :N XPSs  320 - 1  . . .  320 -X can be realized using larger XPS: eg a 60 port XPS can in case of 4 SPs be used for 6 wavelengths (Tx+Rx*(1 PON facing port+4 SP ports)=10 ports required for each wavelength). However, MxM XPS allows for more switching possibilities than required for this application and are therefore not optimal in resource utilization. The NetOp can monitor the various parts: the TRx array for optical powers etc, and can also in e.g., a round-robin fashion (using an extra XPS port) monitor the SP packet headers. Thus, the WDM-PON line cards  308 - 1  . . .  308 -M if desired can be totally under the control of the NetOp. 
         [0026]    The SP uplink cards  312 - 1  . . .  312 -L and  314 - 1  . . .  314 -L can be totally under the control of their respective SPs  304 - 1  . . .  304 -N. For example, SP- 1   304 - 1  controls SP uplink cards  312 - 1  . . .  312 -L. Each SP uplink card  312 - 1  (for example) is connected by one or more uplink ports  334 - 1  . . .  334 -K via the links  313 - 1  . . .  313 -K (e.g., GbE (SM, MM, cat6), 10 GbE (SM, MM, Cat6)) to the dedicated SP  304 - 1  (for example). Each SP uplink card  312 - 1  (for example) includes a L 2  switch  336  which is connected to one or more OIMs  338 - 1  . . .  338 -K (e.g., SFPs  338 - 1  . . .  338 -K) which are connected to the uplink ports  334 - 1  . . .  334 -K. Each OIM  338 - 1  (for example) has a first side  340  connected to one uplink port  334 - 1  which is coupled via one link  313 - 1  to the SP- 1   304 - 1 . Each OIM  338 - 1  has a second side  342  connected to a first side  344  of the L 2  switch  336 . The L 2  switch  336  has a second side  346  with multiple ports  348 - 1  . . .  348 -X connected to the backplane  310  such that one of the ports  348 - 1  (for example) is coupled to one of the ports  332 - 1  (for example) on the second side  334  of one of the L 1  switches  320 - 1  (for example) in the WDM-PON line card  308 - 1  (for example). In this configuration, each uplink port  334 - 1  . . .  334 -K can be shared among all of the wavelength channels on the multi-channel transmitter-receiver array  318  which are supported by PON # 1   306 - 1 . 
         [0027]    In this example, the L 2  switch  336  at the SP uplink card  312 - 1  (for example) is facing the backplane  310  toward one or more WDM-PON line cards  308 - 1  . . .  308 -M and has a number of ports  348 - 1  . . .  348 -X equal to the number of wavelengths on the one or more WDM-PON line cards  308 - 1  . . .  308 -M. For example, if the SP uplink card  312 - 1  is made to interface just one 48 wavelength channel WDM-PON line card  308 - 1 , the L 2  switch  336  needs to have 48 ports  348 - 1  . . .  348 -X facing the backplane  310  connecting to the WDM-PON line card  308 - 1 . This way, the backplane  310  of the unbundling OLT  302  replaces an optical patch panel as a meeting point for the SP- 1   304 - 1 . Such an optical patch panel, typically needed for physical layer unbundling, has problems with a high number of ports and resulting large size. The L 2  functionality at the SP uplink card  312 - 1  enables efficient use of uplink ports  334 - 1  . . .  334 -K and reduces the need for additional hardware and manual labor when the SP- 1   304 -I acquires (or loses) a new (existing) wavelength. For instance, one GbE port  334 - 1  can be shared among all the wavelengths the SP- 1   304 - 1  has on a particular PON # 1   306 - 1 . A further improvement comes when one SP- 1   304 - 1  (for example) has multiple SP uplink cards  312 - 1  . . .  312 -L directly connected to one another over the OLT backplane which enables one uplink port  334 - 1  to be shared among several PONs  306 - 1  . . .  306 -M (see  FIG. 4 ). Further, when one SP- 1   304 - 1  (for example) has one or more SP uplink cards  312 - 1  . . .  312 -L equipped with a number of uplink ports  334 - 1  . . .  334 -K (e.g., both 1 GbE and 10 GbE), these ports  334 - 1  . . .  334 -K can be connected to one or more SP uplink cards dedicated to SP- 1   304 - 1  in one or more OLTs  302  and  302 ′ to enable an increase of uplink capacity as the number of SP wavelengths (i.e., subscribers) increase (see  FIGS. 5A and 5B ). 
         [0028]    Referring to  FIG. 4 , there is shown a block diagram of a portion of the exemplary system  300  illustrating in greater detail a scenario where one SP- 1   304 - 1  has multiple SP uplink cards  312 - 1 ,  312 - 2  . . .  312 -L each of which are connected to one WDM-PON line card  308 - 1 ,  308 - 2  . . .  308 -M in accordance with the first embodiment of the present invention. The components within each of the SP uplink cards  312 - 1 ,  312 - 2  . . .  312 -L and the WDM-PON line cards  308 - 1 ,  308 - 2  . . .  308 -M have been discussed above and are not repeated here but reference is made to the connections  402  between the SP uplink card&#39;s L 2  switches  336  which enable one uplink port  334 - 1  (for example) to be shared among several PONs  306 - 1 ,  306 - 2  . . .  306 -M (note: the connections  402  would typically be done via the backplane  310 ). The uplink ports  334 - 1  . . .  334 -K can be of different media type: SM, MM, Cat6 etc, and speed (e.g., mix of 1 GbE and 10 GbE) to minimize the capital expenditure. The SP  304 - 1  . . .  304 -N′s network equipment can be located at remote sites and connected via long-haul optics to the unbundling OLT  302 . Also, as each L 2  switch  336 ′s functionality is mainly used for aggregation, this functionally is likely rather simple and the more advanced access network related traffic handling (high touch functions like subscriber management etc.) is likely located at the SP&#39;s network equipment which connects to the unbundling OLT  302 . Finally, as each SP uplink card  312 - 1 ,  312 - 2  . . .  312 -L is under the control of a specific SP- 1   304 - 1  (for example) and the traffic is not mixed with any other SP- 2  . . . SP-N, the SP- 1   304 - 1  can apply whatever L 2  practice they prefer. 
         [0029]    Referring to  FIGS. 5A and 5B , there are shown block diagrams of the exemplary system  300  including multiple unbundling OLTs  302  and  302 ′ (only two shown) in accordance with the first embodiment of the present invention. In this example, one SP- 1   304 - 1  (for example) has one uplink port  334 - 1  (for example) shared among several PONs  306 - 1 ,  306 - 2  . . .  306 -M associated with one unbundling OLT  302  and the same uplink port  334 - 1  is also shared among several PONs  306 - 1 ′,  306 - 2 ′. . .  306 -M′ associated with a second unbundling OLT  302 ′. In particular, the one SP- 1   304 - 1  has one uplink port  334 - 1  shared among several PONs  306 - 1 ,  306 - 2  . . .  306 -M associated with one unbundling OLT  302  by connecting multiple SP uplink cards  312 - 1 ,  312 - 2  . . .  312 -L to one another via connections  402  between the L 2  switches  336  each of which in turn are connected to one WDM-PON line card  308 - 1 ,  308 - 2  . . .  308 -M (see  FIG. 4 ). Furthermore, the one SP- 1   304 - 1  has one uplink port  334 - 1  shared among several PONs  306 - 1 ′. . .  306 -M′ associated with the second unbundling OLT  302 ′ by connecting the OIMs  338 - 1  . . .  338 -K of one SP uplink card  312 - 1  (for example) in the first unbundling OLT  302  to corresponding OIMs  338 - 1 ′. . .  338 -K′ of one SP uplink card  312 - 1 ′ (for example) in the second unbundling OLT  302 ′. The second unbundling OLT  302 ′ is similar to the first unbundling OLT  302  except that the components therein have a reference number of xxx′ instead of reference number xxx. If desired, the exemplary system  300  can have any number of unbundling OLTs that may be or may not be connected to one another. 
         [0030]    Referring to  FIG. 6 , there is shown a block diagram illustrating an exemplary system  600  including an exemplary unbundling OLT  602  positioned between multiple SPs  604 - 1 .. 604 -N and multiple sets of fibers  606 - 1  . . .  606 -M (associated with ODF  607 ) in accordance with a second embodiment of the present invention. The unbundling OLT  602  includes one or more p2p line cards  608 - 1  . . .  608 -M, a backplane  610 , one or more SP uplink cards  612 - 1  . . .  612 -L (dedicated to SP- 1   604 - 1 ), and one or more SP uplink cards  614 - 1  . . .  614 -L (dedicated to SP-N  604 -N). The p2p line cards  608 - 1  . . .  608 -M each interface with a individual set of fibers  606 - 1  . . .  606 -M. Plus, the p2p line cards  608 - 1  . . .  608 -M are coupled by the backplane  610  to the SP uplink cards  612 - 1  . . .  612 -L and  614 - 1  . . .  614 -L. Each set of the SP uplink cards  612 - 1  . . .  612 -L and  614 - 1  . . .  614 -L are respectively coupled via one or more links  613 - 1  . . .  613 -K to one of the SPs  604 - 1  . . .  604 -N. 
         [0031]    The p2p line cards  608 - 1  . . .  608 -M each include a multi-channel transmitter-receiver array  618  (e.g., 48 channel Tx/Rx array  618  which uses “gray” optics over parallel fibers) and multiple L 1  switches  620 - 1  . . .  620 -X (e.g., 48  1 :N XPSs  620 - 1  . . .  620 -X). As shown, the multi-channel transmitter-receiver array  618  has a first side  622  coupled to a set of fibers  606 - 1  (e.g., 48 fibers  606 - 1 ) and a second side  624  coupled to the L 1  switches  620 - 1  . . .  620 -X. Each L 1  switch  620 - 1  . . .  620 -X has one port  626 - 1  . . .  626 -X on a first side  628  connected to a port  630 - 1  . . .  630 -X associated with one of the wavelength channels on the multi-channel transmitter-receiver array  618 . Plus, each L 1  switch  620 - 1  . . .  620 -X has multiple ports  632 - 1  . . .  632 -N on a second side  634  coupled to the backplane  610 , where each port  632 - 1  . . .  632 -N is associated with one SP  604 - 1  . . .  604 -N. 
         [0032]    In this example, the multi-channel transmitter-receiver array  618  is in a common package to reduce the cost of the optical transmitters and receivers. For example, the common package can contain  12  channels or even all the channels (or more) associated with the corresponding set of multiple fibers  606 - 1  . . .  606 -M. Each electrical Tx/Rx port  630 - 1  . . .  630 -X of the multi-channel transmitter-receiver array  618  is connected to one of the  1 :N XPSs  620 - 1  . . .  620 -X which is used to select SP(s)  604 - 1  . . .  604 -N for each fiber in the corresponding set of multiple fibers  606 - 1  . . .  606 -M. The XPS performs switching on L 1  which is transparent to SP packets and protocols. The  1 :N XPSs  620 - 1  . . .  620 -X can be realized using a larger MxM XPS if desired. However, MxM XPS allows for more switching possibilities than required for this application and are therefore not optimal in resource utilization. The NetOp can monitor the various parts: the TRx array for optical powers etc, and can also in e.g., a round-robin fashion (using an extra XPS port) monitor the SP packet headers. Thus, the p2p line cards  608 - 1  . . .  608 -M if desired can be totally under the control of the NetOp. 
         [0033]    The SP uplink cards  612 - 1  . . .  612 -L and  614 - 1  . . .  614 -L can be totally under the control of their respective SPs  604 - 1  . . .  604 -N. For example, SP- 1   604 - 1  controls SP uplink cards  612 - 1  . . .  612 -L. Each SP uplink card  612 - 1  (for example) is connected by one or more uplink ports  634 - 1  . . .  634 -K via the links  613 - 1  . . .  613 -K (e.g., GbE (SM, MM, cat6), 10 GbE (SM, MM, Cat6)) to the dedicated SP  604 - 1  (for example). Each SP uplink card  612 - 1  (for example) includes a L 2  switch  636  which is connected to one or more OIMs  638 - 1  . . .  638 -K (e.g., SFPs  638 - 1  . . .  638 -K) which are connected to the uplink ports  634 - 1  . . .  634 -K. Each OIM  638 - 1  (for example) has a first side  640  connected to one uplink port  634 - 1  which is coupled via one link  313 - 1  to the SP- 1   604 - 1 . Each OIM  638 - 1  has a second side  642  connected to a first side  644  of the L 2  switch  636 . The L 2  switch  636  has a second side  646  with multiple ports  648 - 1  . . .  648 -X connected to the backplane  610  such that one of the ports  648 - 1  (for example) is coupled to one of the ports  632 - 1  (for example) on the second side  634  of one of the L 1  switches  620 - 1  (for example) in the p2p line card  608 - 1  (for example). In this configuration, each uplink port  634 - 1  . . .  634 -K can be shared among all of the wavelength channels on the multi-channel transmitter-receiver array  618  which are supported by fibers in the corresponding set of fibers  606 - 1  . . .  606 -M. 
         [0034]    In this example, the L 2  switch  636  at the SP uplink card  612 - 1  (for example) is facing the backplane  610  toward one or more p2p line cards  608 - 1  . . .  608 -M and has a number of ports  648 - 1  . . .  648 -X equal to the number of wavelengths on the one or more p2p line cards  608 - 1  . . .  608 -M. For example, if the SP uplink card  612 - 1  is made to interface just one 48 wavelength channel p2p line card  608 - 1 , the L 2  switch  636  needs to have 48 ports  648 - 1  . . .  648 -X facing the backplane  610  connecting to the p2p line card  608 - 1 . This way, the backplane  610  of the unbundling OLT  602  replaces an optical patch panel as a meeting point for the SP- 1   604 - 1 . Such an optical patch panel, typically needed for physical layer unbundling, has problems with a high number of ports and resulting large size. The L 2  functionality at the SP uplink card  612 - 1  enables efficient use of uplink ports  634 - 1  . . .  634 -K and reduces the need for additional hardware and manual labor when the SP- 1   604 - 1  acquires (or loses) a new (existing) wavelength/fiber. For instance, one GbE port  634 - 1  can be shared among all the wavelengths the SP- 1   604 - 1  has on the fibers associated with one set of fibers  606 - 1  (for example). A further improvement comes when one SP- 1   604 - 1  (for example) has multiple SP uplink cards  612 - 1  . . .  612 -L directly connected to one another over the OLT backplane which enables one uplink port  634 - 1  to be shared among several sets of multiple fibers  606 - 1  . . .  606 -M (see  FIG. 7 ). Further, when one SP- 1   604 - 1  (for example) has SP uplink cards  612 - 1  . . .  612 -L equipped with a number of uplink ports  634 - 1  . . .  634 -K (e.g., both 1 GbE and 10 GbE) these ports  634 - 1  . . .  634 -K can be connected to one or more other SP uplink cards dedicated to SP- 1   604 - 1  in one or more OLTs  602  and  602 ′ to enable an increase of uplink capacity as the number of SP&#39;s fibers increase (see  FIGS. 8A and 8B ). 
         [0035]    Referring to  FIG. 7 , there is shown a block diagram of a portion of the exemplary system  600  illustrating in greater detail a scenario where one SP- 1   604 - 1  has multiple SP uplink cards  612 - 1 ,  612 - 2  . . .  612 -L each of which are connected to one p2p line card  608 - 1 ,  608 - 2  . . .  608 -M in accordance with the second embodiment of the present invention. The components within each of the SP uplink cards  612 - 1 ,  612 - 2  . . .  612 -L and the p2p line cards  608 - 1 ,  608 - 2  . . .  608 -M have been discussed above and are not repeated here but reference is made to the connections  702  between the SP uplink card&#39;s L 2  switches  636  which enable one uplink port  634 - 1  (for example) to be shared among sets of fibers  606 - 1 ,  606 - 2  . . .  606 -M (note: the connections  702  would typically be done via the backplane  610 ). The uplink ports  634 - 1  . . .  634 -K can be of different media type: SM, MM, Cat6 etc, and speed (e.g., mix of 1 GbE and 10 GbE) to minimize the capital expenditure. The SP  604 - 1  . . .  604 -N′s network equipment can be located at remote sites and connected via long-haul optics to the unbundling OLT  602 . Also, as each L 2  switch&#39;s  636  functionality is mainly used for aggregation, this functionally is likely rather simple and the more advanced access network related traffic handling (high touch functions like subscriber management etc.) is likely located at the SP&#39;s network equipment which connect to the unbundling OLT  602 . Finally, as each SP uplink card  612 - 1 ,  612 - 2  . . .  612 -L is under the control of a specific SP- 1   604 - 1  (for example) and the traffic is not mixed with any other SP- 2  . . . SP-N, the SP- 1   604 - 1  can apply whatever L 2  practice they prefer. 
         [0036]    Referring to  FIGS. 8A and 8B , there are shown block diagrams of the exemplary system  600  including multiple unbundling OLTs  602  and  602 ′ (only two shown) in accordance with the second embodiment of the present invention. In this example, one SP- 1   604 - 1  (for example) has one uplink port  634 - 1  (for example) shared among several sets of multiple fibers  606 - 1 ,  606 - 2  . . .  606 -M associated with one unbundling OLT  602  and the same uplink port  634 - 1  is also shared among several sets of multiple fibers  606 - 1 ′,  606 - 2 ′. . .  606 -M′ associated with a second unbundling OLT  602 ′. In particular, the one SP- 1   604 - 1  has one uplink port  634 - 1  shared among several sets of multiple fibers  606 - 1 ,  606 - 2  . . .  606 -M associated with one unbundling OLT  602  by connecting multiple SP uplink cards  612 - 1 ,  612 - 2  . . .  612 -L to one another via connections  702  between the L 2  switches  636  each of which in turn are connected to one p2p line card  608 - 1 ,  608 - 2  . . .  608 -M (see  FIG. 7 ). Furthermore, the one SP- 1   604 - 1  has one uplink port  634 - 1  shared among several sets of multiple fibers  606 - 1 ′,  606 - 2 ′. . .  606 -M′ associated with the second unbundling OLT  602 ′ by connecting the OIMs  638 - 1  . . .  638 -K of one SP uplink card  612 - 1  (for example) in the first unbundling OLT  602  to corresponding OIMs  638 - 1 ′. . .  638 -K′ of one SP uplink card  612 - 1 ′ (for example) in the second unbundling OLT  602 ′. The second unbundling OLT  602 ′ is similar to the first unbundling OLT  602  except that the components therein have a reference number of xxx′ instead of reference number xxx. If desired, the exemplary system  600  can have any number of unbundling OLTs that may be or may not be connected to one another. 
         [0037]    Referring to  FIG. 9 , there is a flowchart illustrating the basic steps of a method  900  for allowing at least two SPs  304 - 1  . . .  304 -N,  604 - 1  . . .  604 -N to use individual fibers of the ODN  307  and  607  in accordance with an embodiment of the present invention. Beginning at step  904 , one or more unbundling OLTs  302 ,  302 ′,  602  and  602 ′ are positioned between at least two SPs  304 - 1  . . .  304 -N,  604 - 1  . . .  604 -N and the ODN  307  and  607 . At step  906 , the L 1  switches  320 - 1  . . .  320 -X,  320 - 1 ′. . .  320 -X′,  620 - 1  . . .  620 -X,  620 - 1 ′. . .  620 -X′ are controlled to select one or more of the channels of the multi-channel transmitter-receiver array  322 ,  322 ′,  622 ,  622 ′ to be used for example by the first SP  304 - 1 ,  604 - 1 . In one case, the NetOp would control the L 1  switches  320 - 1  . . .  320 -X,  320 - 1 ′. . .  320 -X′,  620 - 1  . . .  620 -X,  620 - 1 ′. . .  620 -X. At step  908 , the L 2  switches  336 ,  336 ′,  636 ,  636 ′ are controlled to enable for example the first uplink port  334 - 1  of the first SP  304 - 1 ,  604 - 1  to use the first set of one or more ODN fibers  306 - 1 ,  306 - 1 ′,  606 - 1  and  606 - 1 ′ associated with the ODN  307  and  607 . In one case, the SP- 1   304 - 1  and  604 - 1  would control the L 2  switches  336 ,  336 ′,  636  and  636 ′. 
         [0038]    From the foregoing, one skilled in the art will appreciate that the present invention proposes to use an unbundling OLT  302  and  602  which combines in a unique manner L 1  and L 2  switching to enhance the capability of physical layer unbundling (Open Access). In the WDM-PON scenario, the unbundling OLT  302  has the L 1  switches  320 - 1  . . .  320 -X placed on the PON line cards  308 - 1  . . .  308 -M and for each wavelength the L 1  switch  320 - 1  . . .  320 -X selects one of the SP- 1  . . . SP-N. The L 2  switches  336  are placed on the SP specific uplink cards  312 - 1  . . .  312 -L and  314 - 1  . . .  314 -L to make efficient and flexible use of optical links  313 - 1  . . .  313 -K to each SP. Thus, for example one SP GbE port  334 - 1  at that SP specific uplink card  312 - 1  could be used for different and multiple WDM-PON wavelengths, while these WDM-PON wavelengths are used exclusively by this SP- 1  the traffic is not mixed with any other SP&#39;s traffic. This implies further that no manual cabling is needed when a SP acquires more wavelengths, unless the SP would like to assign more uplink bandwidth to the wavelengths it operates. The p2p scenario is the same as the WDM-PON scenario except where a fiber is used instead of a wavelength and the p2p line cards  608 - 1  . . .  608 -M do not have a WDM multiplexer  316 . Furthermore, in the case of WDM-PON, the multi-channel Tx/Rx array  318  uses multiple wavelengths (i.e. WDM) on one fiber  306 - 1  (for example), while in the p2p case the multi-channel Tx/Rx array  618  uses multiple fibers  606 - 1  (for example)(i.e. one wavelength per fiber, being the same for each fiber, i.e. “gray” interfaces, as opposed to “colored” interfaces for WDM). 
         [0039]    The present invention is described herein in an application where the traffic can be represented by L 2 , e.g., IP packets within Ethernet frames being transported over optical links. However, it should be appreciated that any packet based traffic can be handled in similar way (ATM, Fibre Channel, Frame relay etc). It should also be appreciated that the applications may be not only residential access but also business connections, mobile backhaul etc. In addition, mobile backhaul is sometimes performed with L 1  based sampled digital data. In this case, the unbundling OLT concept of the present invention can still be used, although the SP uplink card will not include a L 2  switching device, but instead in it&#39;s simplest form just an optical/electrical conversion to the unbundling OLT backplane is utilized. Lastly, it should also be appreciated that various components such as the multi-channel transmitter-receiver array, the L 1  switches, the L 2  switches and the OIMs have been described and claimed herein as having first sides and second sides but those sides do not necessarily need to be different physical sides on the component but could be the same physical side on the component. 
         [0040]    Although multiple embodiments of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that the invention is not limited to the disclosed embodiments, but instead is also capable of numerous rearrangements, modifications and substitutions without departing from the present invention that as has been set forth and defined within the following claims.