Abstract:
A network TAP that provides access to data communicated in a network. The TAP includes a first port for connecting to a pluggable optoelectronic module such as an optical transceiver, a link port for connecting to an optical link configured to receive and send data to the optical transceiver, and a TAP port for relaying diverted optical data to a storage and/or analyzing device. Couplers are used to split the optical signals entering the TAP from the first port and/or the link port such that a useable portion of the optical signal(s) can be stored and/or analyzed. The TAP also includes optical devices for relaying optical signals between components in the TAP.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/583,754, filed Jun. 29, 2004, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. The Field of the Invention 
     The present invention relates to the field of devices for use in optical communications. More particularly, the present invention relates to optical devices for tapping an optical fiber to divert a portion of an optical signal to a connected device such as a network analyzer. 
     2. The Relevant Technology 
     As local area networks and other networks become more pervasive and complex, the need to obtain access to network data for purposes of testing, monitoring, analysis, etc., has become more important. For instance, when a network problem is experienced, a network administrator may need to capture or otherwise monitor the network data to diagnose the problem and identify the network components or conditions that may be responsible for the condition. 
     One technique for accessing network data is to either break a network link (e.g., temporarily disconnecting an end of a link) so that a network monitoring or analysis device can be placed in-line in a position where the network data can be accessed. The temporary disruption of the network topology and the associated connectivity between network nodes when the link is broken represent a significant problem and, in many situations, makes this approach to network monitoring or analysis highly undesirable. 
     This problem can often be avoided using network Traffic Access Ports (“TAPs”), which are devices that are placed inline in a network link and split, or tap, a data signal by diverting a portion of the signal away from the network link to a TAP port where the signal can be transmitted to a network capture or analysis device. Network TAPs often have multiple ports and can be applied to multiple network links. TAPs typically are positioned in a location in the network where the network problems might be experienced. A primary benefit of network TAPs is the fact that network data can be accessed at will without breaking a network link. Regardless of whether a TAP is in use at any particular time by a network analysis device, the components at either end of the tapped network link can communicate with each other as if the TAP were not present. 
     Although conventional network TAPs have significantly improved the ability to access network data, such TAPs have typically been fixtures located at discrete points in a network. When the TAP is located in a position where data of interest can be accessed, the TAPs generally perform quite well. However, as the topology of a particular network grows or changes, or if the number of conventional TAPs is not sufficient, it is possible that a network problem could arise in a location that is not serviced by a tap. In such situations, the network administrator can access the appropriate network data only by breaking a network link and inserting either a TAP or a network analysis device. 
     One way to solve this problem is to place a TAP on every link of a network, such as a storage area network (SAN) or local area network (LAN). Despite the benefits of such a practice, this has generally not been feasible because conventional network TAPs can be prohibitively expensive or bulky. Moreover, the use of a large number of conventional TAPs can lead to the concern of inserting an undesirable number of potential points of failure into a network. 
     It would therefore represent an advance in the art to provide devices that overcome the foregoing difficulties. 
     BRIEF SUMMARY OF THE INVENTION 
     In order to overcome these needs, the present invention relates to Traffic Access Ports (TAPs) that plug directly into a port in a pluggable optoelectronic module such as an optical transceiver connected to a network device, such as a switch or Redundant Array of Inexpensive Disks (RAID) device. An example of such a port is a communications port that is configured according to the Small Form-factor Pluggable (SFP) Transceiver MultiSource Agreement (MSA). Such SFP ports are common in many network switch or RAID devices. The SFP ports are often used to receive pluggable transceiver modules, such as SFP optical transceivers, that propagate data signals between the port and a remote node in the network. According to the invention, the TAP can be a removable extension of an SFP optical transceiver module that plugs into an SFP port. This enables potentially every communication port or network link to have an associated TAP that provides access to network data for purposes of data capture, analysis, and monitoring. 
     Accordingly, a first example embodiment of the invention is a network TAP that provides access to data communicated in a network. The TAP generally includes: a transceiver port configured to be connected to an optical transceiver module; a link port configured to interface with a network link that is in communication with the optical transceiver module, wherein at least one optical path is configured to relay optical signals between the transceiver port and the link port; and a TAP port configured to relay a portion of optical signals received at the transceiver port and a portion of optical signals received at the link port to a connected device. 
     A second example embodiment of the invention is a removable network TAP that provides access to data communicated in a network. The TAP generally includes: a transceiver port configured to be removably connected to an optical transceiver module whereby the transceiver port can receive a first optical signal from the optical transceiver module and relay a second optical signal to the optical transceiver module; a link port configured to be removably connected to a network link whereby the link port can receive the second optical signal from the network link and relay the first optical signal to the network link; a first coupler configured to receive the first optical signal from the transceiver port and split the first optical signal such that a first portion of the first optical signal is relayed to a TAP port and a second portion of the first optical signal is relayed to the link port; and a second coupler configured to receive the second optical signal from the link port and split the second optical signal such that a first portion of the second optical signal is relayed to the TAP port and a second portion of the second optical signal is relayed to the transceiver port. 
     A third example embodiment of the invention is a network TAP that provides access to data communicated in a network. The TAP includes: a transceiver port configured to be connected directly to an SFP optical transceiver module, including a first transceiver interface for receiving outgoing signals from a transmitter optical subassembly of the optical transceiver module and a second transceiver interface for passing incoming signals to a receiver optical subassembly of the optical transceiver module; a link port that interfaces with a network link that is in communication with the optical transceiver module, including a first link interface for connecting to a first optical cable carrying incoming signals and a second link interface for connecting to a second optical cable carrying outgoing signals; a TAP port that is configured for relaying optical signals to a connected device; a first optical path between the first transceiver interface and the second link interface; a first coupler for splitting a portion of the optical signals transmitted on the first optical path such that the split portion of the optical signals are relayed on a third optical path to the TAP port; a second optical path between the second transceiver interface and the first link interface; and a second coupler for splitting a portion of the optical signals transmitted on the second optical path such that the split portion of the optical signals are relayed on a fourth optical path to the TAP port. 
     These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1A  illustrates a Traffic Access Port in a network environment according to a first embodiment of the invention; 
         FIG. 1B  illustrates further details of a Traffic Access Port according to another example embodiment of the invention; and 
         FIG. 2  illustrates configurations of a link port and a TAP port in a Traffic Access Port according to additional example embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made to the drawings to describe various aspects of exemplary embodiments of the invention. It is to be understood that the drawings are diagrammatic and schematic representations of such exemplary embodiments, and are not limiting of the present invention, nor are they necessarily drawn to scale. 
     In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known aspects of optical systems have not been described in great detail in order to avoid unnecessarily obscuring the present invention. 
     Referring now to  FIGS. 1A and 1B ,  FIG. 1A  schematically illustrates an embodiment of a network Traffic Access Port (“TAP”)  106  according to the invention in an example network environment. As illustrated, TAP  106  is connected to a pluggable optoelectronic module such as an optical transceiver module  102 . The optical transceiver module is in turn connected to a port in a network device  104 , such as a switch, a host bus adapter, a Redundant Array of Independent Disks (RAID), or other network device to which an optical transceiver may be connected. 
     The optical transceiver module  102  can be any of various types of transceiver modules that pass data bidirectionally, meaning that the module has a transmitter optical subassembly with a laser that transmits data out into the network and a receiver optical subassembly that receives data in from the network. Such a transceiver passes incoming data through a first cable connector (not illustrated) and outgoing data through a second cable connector (not illustrated). For example, a preferred transceiver module for use with the network TAPs of the invention is a conventional SFP transceiver module. An SFP module is bidirectional, having incoming and outgoing connector ports at a duplex connector. Further details regarding conventional SFP device configurations are well known in the art and can be found, for example, in the “Small Form Factor Pluggable (SFP) Transceiver MultiSource Agreement (MSA)”, (Sep. 14, 2000), which is incorporated herein by reference. Other standard and future transceivers and their respective interface connectors are also well known in the art, or will be well known in the art, and are also included within the scope of the invention. 
     In normal operation, transceiver module  102  would transmit and receive optical signals on optical cables  164  and  166 . When TAP  106  is inserted, however, optical signals are routed through TAP  106  between transceiver module  102  and optical cables  164 ,  166 . The TAP  106  also diverts a copy of incoming and/or outgoing the optical signals onto cables  168  and  170  to a connected network device  108 . Network device  108  can be, for example, a network analyzer, a mass storage device for storing captured data, or any other device where it is desired to receive the copied or split optical signal. 
     Referring now to  FIG. 1B , the TAPs of the present invention are three port devices, including a “transceiver” port  150  that connects directly with an optical transceiver, a “link” port  152  that connects with the network link (cables  164 ,  166 ) that communicates with the transceiver, and a “tap” port  154  that connects with network device  108  that accesses the tapped network data. As used herein, the term “port” denotes a communications access point, including both male and female adapters, other connectors, and wireless components. As previously noted, one skilled in the art will recognize that the illustrations do not depict required port forms or configurations. By way of example only, in a preferred embodiment of the invention, transceiver port  150  will be an SFP duplex cable connector such that it can plug into a duplex transceiver connector on an SFP transceiver module. Similarly, link port  152  will be an SFP duplex transceiver connector such that a duplex cable connector on cables  164  and  166  can quickly and easily be attached. TAP port  154  is more flexible and can be selected to match the desired hardware for cable  168  and  170  and network device  108 . The preferred embodiment of the invention wherein ports  150  and  152  replicate the cable and transceiver ports between which it will be inserted serves to make the device easy to insert and remove into a network. Alternatively, additional adapters can be used to insert TAP  106  if necessary for compatibility with the connectors on transceiver  102  and cables  164 ,  166 . 
     As shown in  FIG. 1B , the TAP  106  includes a pair of couplers  156 , each associated with one of the directional links of the SFP module. The couplers split a portion of the data signals out of the associated links such that a network analysis device connected to the TAP can access the network data. As noted in  FIGS. 1A and 1B , a network device  108  connected to the TAP  106  can obtain incoming data from the link port  150  and the transceiver port  152 , thereby accessing data from both of the directional links of the transceiver. More particularly, optical link  112  passes through a coupler  156  where a portion of an optical signal is split and sent on optical link  116  to TAP port  154  and on to network device  108 . Similarly, optical link  110  passes through a coupler  156  where a portion of an optical signal is split and routed on optical link  114  to TAP port  154  and on to network device  108 . 
     The couplers  156  within the TAP  106  can have any desired split ratios. For example, the couplers  156  can provide a split ratio of 70/30, meaning that 70% of the optical power passes through a coupler  156  and remains in the network link and 30% is diverted from the TAP  106  to the network device  108 . The split ratio that is used in any particular situation is determined by the light loss budget constraints of the network and the amount of power required by the network analysis device. 
     The TAPs shown in  FIG. 1  are 1×1 TAPs, meaning that there is one TAP port for each tapped bidirectional link. The TAPs of the invention can also have other numbers of TAP ports (e.g., 1×2 or higher-order TAPs). However, 1×1 TAPs are generally preferred because of the space constraints and light loss budget constraints that often exist. 
     Referring now to  FIG. 2 , the TAP port  154  and the link port  152  can be aligned in various configurations depending on the space constraints associated with the ports on the network device. For example, the port for the network link and the port for the network analysis device can have a horizontal configuration  204  or a vertical configuration  202  as illustrated in the alternative configurations in  FIG. 2 . Interfaces  155 ,  157 ,  159 , and  161  are depicted to illustrate one preferred arrangement of such interfaces for connecting with optical cables at the TAP and link ports. 
     The TAPs of the invention can be discrete components that can be removably connected to a pluggable optical transceiver module as illustrated above. In other embodiments, the TAPs can be integrated into an optical transceiver module rather than being a separate component, in which case transceiver port  150  may be omitted in certain embodiments. Although the invention is described herein primarily in reference to Small Form Factor Pluggable (SFP) modules, the principles of the invention can also be applied to TAPs that can be used with other communication modules, such as Small Form Factor (SFF) modules, other optoelectronic transceiver modules or other types of transceivers. 
     Because the TAPs of the invention are relatively small and have only a single port to be accessed by a network analysis device, the TAPs can be relatively inexpensive. Thus, the TAPs of the invention can reasonably permit a network administrator to install TAPs in as many as all of the network links of a network. As network problems are experienced, the network administrator can connect a network analysis device to any of the links that might be useful to analyze. 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.