Abstract:
A method comprising identifying a data demand of an optical channel request; identifying available resources for satisfying the optical channel request; selecting light paths to a destination based on the identified available resources, wherein each light path is distinct; selecting one or more optical carriers for each light path; optically transmitting data pertaining to the optical channel request based on the selected light paths, wherein each selected optical carrier of each light path carries a portion of the data and a total of the one or more optical carriers associated with the light paths collectively carry an entire portion of the data; receiving the one or more optical carriers of the light paths at the destination; identifying a latency between the one or more optical carriers of the light paths; adjusting the latency between the one or more optical carriers of the light paths; and assembling the data.

Description:
BACKGROUND 
       [0001]    With traffic demands continually increasing, driven by, among other things, video, cloud computing and mobility, optical network operators and/or service providers are confronted with a host of challenges to accommodate these traffic demands. One solution proposed to address this problem is the idea of super-channels, which permit multiple optical carriers to be bonded together (e.g., frequency-locked optical carriers, etc.) to enable channel data rates that exceed the 100 Gigabits/second (Gb/s) model. For example, super-channels may be configured to support channel data rates in the Terabit/second (Tb/s) realm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1A  is a diagram illustrating an exemplary embodiment of an optical network having light-path aggregation capability; 
           [0003]      FIG. 1B  is a diagram illustrating components of an exemplary embodiment of a transmitting-side of one of the optical nodes depicted in  FIG. 1A : 
           [0004]      FIG. 1C  is a diagram illustrating components of an exemplary embodiment of a receiving-side of one of the optical nodes depicted in  FIG. 1A ; 
           [0005]      FIG. 2A  is a diagram illustrating optical carriers of a channel traversing an optical network along a single light path; 
           [0006]      FIG. 2B  is a diagram illustrating optical carriers of a channel traversing the optical network along multiple light paths; 
           [0007]      FIG. 3  is a diagram illustrating an exemplary scenario in which multiple light paths of a channel traverse the optical nodes of the optical network; 
           [0008]      FIG. 4  is a diagram illustrating another exemplary scenario in which multiple light paths of a channel traverse the optical nodes of the optical network; 
           [0009]      FIG. 5  is a diagram illustrating yet another exemplary scenario in which multiple light paths of a channel traverse the optical nodes of the optical network; 
           [0010]      FIG. 6A  is a diagram illustrating another exemplary scenario in which multiple light paths of a channel traverse the optical nodes of the optical network; 
           [0011]      FIG. 6B  is a diagram illustrating an exemplary channel management table; 
           [0012]      FIG. 7  is a flow diagram illustrating an exemplary process for transmitting optical carriers of a channel along multiple light paths; and 
           [0013]      FIG. 8  is a flow diagram illustrating an exemplary process for receiving the optical carriers of a channel that traversed multiple light paths. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0014]    The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. Also, the following detailed description does not limit the invention. 
         [0015]    As traffic demands continually increase, optical networks must correspondingly increase their capacity. Optical networks, particularly long-haul optical networks, are now steering toward a super-channel architecture, in which a host of optical carriers are used and each optical carrier carries a fraction of the data of the super-channel. According to the super-channel architecture, the super-channel propagates from a source to a destination along a single light path. 
         [0016]    According to an exemplary embodiment, an optical transport channel can be carried by multiple optical carriers in which the optical carriers can propagate along different light paths. That is, an optical carrier belonging to a particular transport channel may propagate along a light path different from another optical carrier belonging to the same transport channel. 
         [0017]    According to an exemplary embodiment, the optical network includes light-path aggregation capability for optical transport channels. That is, the optical carriers belonging to a particular channel may aggregate at the end points of a light path. According to an exemplary embodiment, the aggregation capability includes, among other capabilities, a latency capability to manage latencies that may be created by virtue of optical carriers belonging to the same transport channel propagating along different light paths. According to such an embodiment, the latency of an optical carrier may be detected and re-timed, when needed. According to an exemplary implementation, buffers may be used, among other components, to manage the latencies of optical carriers. 
         [0018]    According to an exemplary embodiment, an optical carrier of a transport channel may have its own data rate, modulation format, and/or light path provided that the total data rate of all of the optical carriers belonging to the transport channel meet the requirements of the optical transport channel. 
         [0019]      FIGS. 1A-1C  are diagrams illustrating an exemplary embodiment of an optical network having light-path aggregation capability. As illustrated in  FIG. 1A , an exemplary environment  100  includes an optical network  105  including optical node  110 - 1  through optical node  110 -X, in which X&gt;1 (referred to individually as optical node  110  or collectively as optical nodes  110 ), optical link  115 - 1  through optical link  115 -Z, in which Z&gt;1 (referred to individually as optical link  115  or collectively as optical links  115 ), and device  120 - 1  through device  120 -Z, in which Z&gt;1 (referred to individually as device  120  or collectively as devices  120 ). Devices  120  may be communicatively coupled to network  105  via various access technologies. 
         [0020]    The number of devices (which includes optical nodes) and the configuration in environment  100  are exemplary and provided for simplicity. According to other embodiments, environment  100  may include additional devices, fewer devices, different devices, and/or differently arranged devices than those illustrated in  FIG. 1A . For example, environment  100  may include intermediary devices (not illustrated) to permit communication between devices  120  and optical network  105 . 
         [0021]    Optical network  105  is an optical network. For example, optical network  105  may include a synchronous optical network. Optical network  105  may be implemented using various topologies (e.g., mesh, ring, etc.). According to an exemplary embodiment, optical network  105  is a long-haul optical network (e.g., long-haul, extended long-haul, ultra long-haul). According to other embodiments, optical network  105  is an optical network other than a long-haul optical network. According to an exemplary embodiment, optical network  105  is a Dense Wavelength Division Multiplexing (DWDM) network or a Wavelength-Division Multiplexing (WDM) network. 
         [0022]    Optical node  110  is an optical site. For example, optical node  110  may take the form of an optical transmitting node, an optical receiving node, an optical regeneration site, or some other type of intermediary optical device between a source and a destination. Optical node  110  may be implemented as a WDM, a DWDM system, or an Optical Time Division Multiplexing (OTDM) system. Optical link  115  is an optical fiber that communicatively couples optical node  110  to another optical node  110 . For example, optical link  115  may take the form of a nonzero dispersion-shifted fiber, etc. 
         [0023]    Device  120  may include a device having the capability to communicate with a network (e.g., optical network  105 ), devices (e.g., optical node  110 , etc.) and/or systems. For example, device  120  may correspond to a user device. The user device may take the form of a portable device, a handheld device, a mobile device, a stationary device, a vehicle-based device, or some other type of user device. Additionally, or alternatively, device  120  may correspond to a non-user device, such as, a meter, a sensor, or some other device that is capable of machine-to-machine (M2M) communication. 
         [0024]      FIG. 1B  is a diagram illustrating components of an exemplary embodiment of a transmitting-side of one of the optical nodes  110  depicted in  FIG. 1A . As illustrated, optical node  110  includes a data source  105 , a laser  110 , a carrier generator  115 , modulators  120 - 1  through  120 -T, in which T&gt;1 (referred to individually as modulator  120  or collectively as modulators  120 ), transmitters  125 - 1  through  125 -T (referred to individually as transmitter  125  or collectively as transmitters  125 ), a channel manager  130 , and a Reconfigurable Optical Add-Drop Multiplexer (ROADM))  135 . As further illustrated, optical links  115 - 1  through  115 - 3  are coupled to ROADM  135 . The number of optical links  115  is exemplary and provided for simplicity. 
         [0025]    The number of components and the configuration (e.g., connection between components) are exemplary and provided for simplicity. According to other embodiments, optical node  110  may include additional components, fewer components, different components, and/or differently arranged components than those illustrated in  FIG. 1B . For example, the transmitting-side of optical node  110  may include a power source, an optical amplifier (e.g., Erbium Doped Fiber Amplifier (EDFA), Raman amplifier, etc.), digital signal processing (DSP) (e.g., forward error correction (FEC), equalization, filtering, etc.), an optical transceiver, etc. 
         [0026]    Data source  105  may provide data that is to traverse optical node(s)  110  in optical network  105 . Laser  110  may include a laser (e.g., a cooled laser). According to an exemplary embodiment, laser  110  may include a tunable laser (e.g., a Distributed Feedback (DFB) laser, an External-Cavity Laser (ECL), a Sampled Grating Distributed Bragg Reflector (SGDBR) laser, etc.). Carrier generator  115  may include components (e.g., a Photonic Integrated Circuit (PIC) or other known multicarrier generating architectures) to produce a multicarrier channel, such as a super-channel. 
         [0027]    Modulators  120  may include optical modulators to provide a modulation format in terms of constellation (e.g., binary, quaternary, 8-ary, 16-ary, higher order constellations, etc.), manner of modulation (e.g. intensity, phase, frequency, polarization), etc. Transmitters  125  may include optical transmitters or transponders. 
         [0028]    Channel manager  130  may include logic to manage transport channels and signaling. For example, unlike the super-channel design, optical carriers will traverse different light paths. Thus, channel manager  130  will manage the correlation between optical carriers, a transport channel, and multiple light paths. Channel manager  130  may also correlate performance and alarm information across all optical carriers. 
         [0029]    As described further below, channel manager  130  may also manage failures pertaining to a transport channel. Unlike existing architectures in which all optical carriers traverse the same light path, a failure may impact a portion of the transport channel (e.g., one or more optical carriers traversing a light path), while other optical carriers of the transport channel traversing a different light path may not be impacted by the failure. Channel manager  130  may include one or multiple processors, microprocessors, multi-core processors, application specific integrated circuits (ASICs), controllers, microcontrollers, and/or some other type of hardware logic to perform the processes or functions described herein. ROADM  135  is a ROADM. ROADM  135  may include a colorless (e.g., any wavelength to any add/drop port), a directionless (e.g., any wavelength to any degree), and a contentionless (e.g., any combination of wavelengths to any degree from any port) architecture. ROADM  135  may support any portion of the optical spectrum, any channel bit rate, and/or any modulation format. 
         [0030]    According to an exemplary process, as illustrated in  FIG. 1B , the transmitting-side of optical node  110  may output optical signals (e.g., optical signal outputs  140 - 1  through  140 - 3 ) to optical links  115 , which may traverse separate light paths in optical network  105 . The number of output optical signals is exemplary and provided for simplicity. 
         [0031]      FIG. 1C  is a diagram illustrating components of an exemplary embodiment of a receiving-side of one of the optical nodes  110  depicted in  FIG. 1A . As illustrated, optical node  110  includes a ROADM  150 , receivers  155 - 1  through  155 -T, in which T&gt;1 (referred to individually as receiver  155  or collectively as receivers  155 ), buffers  160 - 1  through  160 -T (referred to individually as buffer  160  or collectively as buffers  160 ), de-modulators  165 - 1  through  165 -T (referred to individually as de-modulator  165  or collectively as de-modulators  165 ), and a channel manager  170 . As further illustrated, optical links  115 - 1  through  115 - 3  are coupled to ROADM  150 . 
         [0032]    The number of components and the configuration (e.g., connection between components) are exemplary and provided for simplicity. According to other embodiments, optical node  110  may include additional components, fewer components, different components, and/or differently arranged components than those illustrated in  FIG. 1B . For example, optical node  110  may include a power source, an optical amplifier (e.g., Erbium Doped Fiber Amplifier (EDFA), Raman amplifier, etc.), DSP, a transceiver, etc. 
         [0033]    ROADM  150  may include a ROADM similar to that described above (i.e., ROADM  135 ). Receivers  155  may include optical receivers or transponders. Buffers  160  may include memory, such as, for example, cache or some other type of ultra-high speed memory to store data in the digital domain. Alternatively, buffers  160  may take the form of optical buffers. According to an exemplary embodiment, buffers  160  may be used to manage delay differences between optical signals of the same transport channel traversing difference light paths by storing the information (e.g., data) pertaining to one or more optical carriers. De-modulators  165  may include optical modulators that complement modulators  120 . 
         [0034]    Channel manager  170  may include logic to manage transport channels and signaling. Channel manager  170  will manage the correlation between optical carriers, a transport channel, and multiple light paths. Channel manager  170  may manage the assembly of the optical carriers of a transport channel and delay differences between the optical carriers. Channel manager  170  may also correlate performance and alarm information across all optical carriers. 
         [0035]    Channel manager  170  may also manage failures pertaining to a transport channel. For example, channel manager  170  may identify when an optical carrier(s) may need to be re-transmitted (e.g., due to the failure) by a source or a transmitting optical node  110 . Channel manager  130  may include one or multiple processors, microprocessors, multi-core processors, application specific integrated circuits (ASICs), controllers, microcontrollers, and/or some other type of hardware logic to perform the processes or functions described herein. 
         [0036]    As previously described, according to exemplary embodiments, a channel can be carried by multiple optical carriers in which the optical carriers can propagate along different light paths via optical nodes  110 . This is in contrast to conventional approaches. For example, as illustrated in  FIG. 2A , optical carriers of a channel traverse an optical network  200  along a single light path (e.g., nodes  110 B-C-F-H). However, as illustrated in  FIG. 2B , according to an exemplary embodiment, optical carriers of a channel traverse optical network  200  along multiple light paths, in which a portion of the channel traverses via nodes  110 B-C-F-H and another portion of the channel traverses nodes  110 B-D-E-K-H. 
         [0037]      FIG. 3  is a diagram illustrating an exemplary scenario in which multiple light paths of a channel traverse optical nodes  110  of optical network  200 . According to this scenario, it may be assumed that a channel between optical nodes  110 B and H is needed. As illustrated in  FIG. 3 , a channel traverses optical network  200  along multiple light paths via optical nodes  110  (e.g., nodes  110 B-A-F-H; nodes  110 B-D-E-K-H; and nodes  110 B-C-F-H) having different modulation (e.g., 16-ary, 8-ary, and quaternary). 
         [0038]      FIG. 4  is a diagram illustrating another exemplary scenario in which multiple light paths of a channel traverse optical nodes  110  of optical network  200 . According to this scenario, it may be assumed that a 400 Gb/s channel between optical nodes  110 B and H is needed. However, optical network  200  does not have enough optical carriers along a single light path (e.g., nodes  110 B-C-F-H) to support this data rate. 
         [0039]    According to an exemplary implementation, the 400 Gb/s channel traverses optical network  200  along multiple light paths. According to this scenario, as illustrated, the 400 Gb/s channel is composed of one 100 Gb/s optical carrier that traverses optical nodes  110 B-A-F-H, two 100 Gb/s optical carriers that traverse optical nodes  110 B-C-F-H, and one 100 Gb/s optical carrier that traverses optical nodes  110 B-D-E-K-H. 
         [0040]      FIG. 5  is a diagram illustrating yet another exemplary scenario in which multiple light paths of a channel traverse optical nodes  110  of optical network  200 . According to this scenario, it may be assumed that a 1 Tb/s channel between optical nodes  110 B and H is needed. However, optical network  200  does not have enough optical carriers along a single light path (e.g., nodes  110 B-C-F-H) to support this data rate. 
         [0041]    According to an exemplary implementation, the 1 Tb/s channel traverses optical network  200  along multiple light paths. According to this scenario, the 1 Tb/s channel is composed of different data rates traversing different light paths. For example, the 1 Tb/s channel is composed of four 200 Gb/s optical carriers that traverse optical nodes  110 B-C-F-H, and two 100 Gb/s optical carrier that traverse optical nodes  110 B-D-E-K-H (e.g., since the distance is much longer than the light path of optical nodes B-C-F-H). 
         [0042]      FIG. 6  is a diagram illustrating another exemplary scenario in which multiple light paths of a channel traverse optical nodes  110  of optical network  200 . According to this scenario, it may be assumed that a 1 Tb/s channel is composed of four 200 Gb/s optical carriers that traverse optical nodes  110 B-C-F-H, and two 100 Gb/s optical carriers that traverse optical nodes  110 B-D-E-K-H. Subsequently, an optical link failure occurs between optical nodes  110 E and K. 
         [0043]    According to an exemplary implementation, destination node  110 -H and/or intermediary node  110 -E may transmit a control signal to source node  110 -B to indicate the existence of the optical link failure. When the control signal is received, channel manager  130  of source node  110 -B may identify the two 100 Gb/s optical carriers that need to be re-transmitted. According to an exemplary implementation, channel manager  130  may use a table or other data structure that stores information pertaining to outbound channels. 
         [0044]      FIG. 6B  illustrates an exemplary channel management table  605 . As illustrated, channel management table  605  may include, among other fields, a channel field  610  that identifies optical channels, a carrier field  615  that identifies a frequency (e.g., a center frequency or a reference frequency), a port field  620  that identifies a port pertaining to ROADM  135 , and a path field  625  that identifies a path associated with an optical carrier. According to other implementations, channel management field  605  may include additional field(s), fewer field(s), and/or different field(s) than those illustrated. For example, channel management table  605  may include fields pertaining to the total data rate of the channel, the data rates pertaining to each optical carrier of a channel, etc. 
         [0045]    According to this scenario, channel manager  130  may identify channel  4 , port  5 , frequencies  1  and  2 , and light path B-D-E-K-H, as this information pertains to the optical carriers that failed to reach destination node  110 -H due to the optical link failure. Since the 1 Tb/s channel comprised of optical carriers traversing distinct light paths, source node  110 -B needs to only compensate for 200 Gb/s of the 1 Tb/s channel instead of the entire 1 Tb/s that would otherwise be needed when all optical carriers of a channel traverse the same light path. 
         [0046]    Based on resource availability, channel manager  130  may assign an optical carrier(s) to another light path (i.e., a working path) to compensate for that portion of the transport channel that did not reach destination node  110 -H. For example, as illustrated in  FIG. 6A , channel manager  130  may use two 100 Gb/s optical carriers via optical nodes  110 B-D-E-G-K-H to compensate for the failure. 
         [0047]    It may be assumed that delay exists between the optical carriers of the 1 Tb/s channel reaching destination node  110 -H. However, channel manager  170  of destination node  110 -H manages these delay differences based on its logic and buffers  160 . 
         [0048]      FIG. 7  is a flow diagram illustrating an exemplary process  700  for transmitting optical carriers of a channel along multiple light paths. Process  700  may be performed by optical node  110 . According to an exemplary implementation, channel manager  130 , in combination with other components of optical node  110 , performs process  700  when optical node  110  is a source or a transmitting node. 
         [0049]    In block  705 , optical node  110  receives an optical channel request. The optical channel request includes the data rate needed for the optical channel and the destination node  110 . The optical channel request may include other information, such as, quality of service information, etc. Channel manager  130  receives pertinent information (e.g., data rate, destination node, etc.) pertaining to the optical channel request to allow channel manager  130  to allocate resources for the multi-light path channel. 
         [0050]    In block  710 , channel manager  130  identifies the data demand pertaining to the optical channel request and available resources. At least based on this information, channel manager  130  is able to select the light paths and optical carriers (blocks  715  and  720 ). Depending on the data demand and available resources, channel manager  130  may select optical carriers of the channel to each have their own data rate, modulation format, and/or light path. For example, channel manager  130  may select multiple light paths in which each light path includes one or more optical carriers. Additionally, or alternatively, as previously described, data rates of different optical carriers may be set to different values to optimize spectral efficiency according to the distance of the light-paths. Additionally, or alternatively, optical carriers may differ in modulation format. In this way, left-over capacities (i.e., resources) of light paths may be used and optical bandwidth waste can be minimized. 
         [0051]    In block  725 , transmitters  125  transmit the selected optical carriers via ROADM  135  along the light paths selected by channel manager  130 . In block  730 , channel manager  130  stores channel information (e.g., in channel management table  605 ) pertaining to the received optical channel request and/or the resources allocated to satisfy the optical channel request. 
         [0052]    Although  FIG. 7  illustrates an exemplary process  700  for transmitting multiple optical carriers of a same channel over multiple light paths, according to other implementations, process  700  may include additional operations, fewer operations, and/or different operations than those illustrated in  FIG. 7  and described herein. 
         [0053]      FIG. 8  is a flow diagram illustrating an exemplary process for receiving the optical carriers of a channel that traversed multiple light paths. Process  800  may be performed by optical node  110 . According to an exemplary implementation, channel manager  170 , in combination with other components of optical node  110 , performs process  800  when optical node  110  is a receiving or a destination node. It may be assumed that optical node  110  (e.g., channel manager  170 ) has knowledge of the light paths and/or optical carriers belonging to a particular channel based on control signaling (e.g., from a source or a transmitting node  110 ). 
         [0054]    In block  805 , optical node  110  receives optical carriers of a channel that traversed different light paths. For example, the optical carriers may be received via ROADM  150  and/or receivers  155 . 
         [0055]    In block  810 , optical node  110  determines the latency between the optical carriers. For example, according to an exemplary implementation, the source or the transmitting node  110  may insert markers into the optical carriers that may be used to determine the latency between the optical carriers by identifying and interpreting the markers included in the optical carriers when the optical carriers are received by optical node  110 . Channel manager  170  may measure and identify the latency between optical carriers based on the markers. 
         [0056]    In block  815 , optical node  110  uses buffer(s)  165  to adjust the identified latency. For example, optical node  110  may convert the optical signal into the digital domain. By way of example, the data may take the form of Asynchronous Transfer Mode (ATM) cells, Internet Protocol (IP) packets, frames, etc.). Channel manager  170  may identify which packets, cells, frames, etc., are stored in buffers  165  based on the identified latency. Alternatively, when buffers  165  take the form of optical buffers, the light may be stored. In this way, an earlier optical carrier or data relative to another optical carrier or may be stored in buffer  165 . According to an exemplary implementation, optical node  110  may include a buffer  165  for each optical carrier to adjust latencies that exist. 
         [0057]    In block  820 , optical node  110  reconstructs the data. For example, channel manager  170  assembles the data (e.g., based on sequence numbers, or other known techniques) with respect to the buffered data and other incoming data received from other optical carriers. The assembled data may be used by a particular service, pushed to an end user, etc. 
         [0058]    Although  FIG. 8  illustrates an exemplary process  800  for receiving multiple optical carriers of a same channel over multiple light paths, according to other implementations, process  800  may include additional operations, fewer operations, and/or different operations than those illustrated in  FIG. 8  and described herein. 
         [0059]    According an exemplary embodiment, described herein, data management at the transport layer may provide additional flexibility relative to existing approaches based on light-path aggregation. 
         [0060]    The foregoing description of implementations provides illustration, but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Accordingly, modifications to the implementations described herein may be possible. 
         [0061]    The terms “a,” “an,” and “the” are intended to be interpreted to include one or more items. Further, the phrase “based on” is intended to be interpreted as “based, at least in part, on,” unless explicitly stated otherwise. The term “and/or” is intended to be interpreted to include any and all combinations of one or more of the associated items. 
         [0062]    In addition, while series of blocks are described with regard to the processes illustrated in  FIGS. 7 and 8 , the order of the blocks may be modified in other implementations. Further, non-dependent blocks may be performed in parallel. Additionally, with respect to other processes described in this description, the order of operations may be different according to other implementations, and/or operations may be performed in parallel. 
         [0063]    An embodiment described herein may be implemented in many different forms. For example, a process or a function may be implemented as “logic” or as a “component.” The logic or the component may include hardware (e.g., one or more processors, multi-core processors, etc.), as previously described. 
         [0064]    In the preceding specification, various embodiments have been described with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded as illustrative rather than restrictive. 
         [0065]    In the specification and illustrated by the drawings, reference is made to “an exemplary embodiment,” “an embodiment,” “embodiments,” etc., which may include a particular feature, structure or characteristic in connection with an embodiment(s). However, the use of the phrase or term “an embodiment,” “embodiments,” etc., in various places in the specification does not necessarily refer to all embodiments described, nor does it necessarily refer to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiment(s). The same applies to the term “implementation,” “implementations,” etc. 
         [0066]    No element, act, operation, or instruction described in the present application should be construed as critical or essential to the embodiments described herein unless explicitly described as such.