Abstract:
An OTDR user interface including a setup menu that includes a plurality of user settings capable of displaying information corresponding to a test, wherein each of the plurality of user settings is capable of displaying information corresponding to a different aspect of the test, and wherein one of the plurality of user settings is a dynamic range setting capable of displaying a dynamic range of the test.

Description:
FIELD OF THE INVENTION 
     The present invention relates to optical time-domain reflectometers (OTDRs), and in particular, to an OTDR user interface that more clearly communicates the changes to the measurement performance of an OTDR that result from changes to certain input parameters. 
     BACKGROUND 
     An optical time-domain reflectometer (OTDR) is a useful tool for testing point-to-point fiber optic links, testing passive optical networks (PONs), and finding faults, such as breaks and measure reflectance or optical return loss (ORL) in fiber optic networks. As shown in  FIG. 1  a typical OTDR includes one or more processors, which include necessary CPU, memory, software and other components. These processors are in communication with a user interface made up of a display and controls, such as buttons, knobs, touch screens or the like, an output pulse generator and laser driver, a sampling analog to digital converter and a photo detector with input amplifier. The output pulse generator and laser driver drives the laser or lasers, which send light pulses through a coupler and into an optical fiber network under test. 
     The OTDR generates output pulses and measures the return signal from the same end of the fiber network under test. The return optical signal from each pulse (optical fiber backscatter and event reflections) is converted into an analog electrical signal that must be amplified. The OTDR input amplifier has a finite gain-bandwidth product, which is a key reason why real OTDR event resolution is longer than would be indicated by the nominal pulse width in nanoseconds divided by 10 equals trace event width in meters. The amplified electrical signal is sampled and converted into digital data points, which are averaged over many pulses (determined by test duration) and digitally filtered if needed to decrease noise, and thus increase dynamic range, at the expense of resolution. The product is a trace. 
     OTDRs typically include a number of user settings, including setup mode, wavelength, distance range, pulse width, and test duration. The setup mode setting allows the user to configure the OTDR for automatic mode, manual or expert mode, or, in some models, application-specific operations. The wavelength setting determines which lasers (wavelengths) are used to measure the fiber network under test. The distance range setting determines the section (length) of the fiber network under test that will be included in the OTDR trace. The pulse width setting determines test pulse duration, typically set in nanoseconds or microseconds, and typically also determines other key OTDR parameters such as amplifier bandwidth and digital or analog filter settings. The test duration setting determines the nominal duration of the test, typically set in seconds or minutes, which in turn determines the number of samples averaged to create each trace data point. 
     In the automatic mode, most settings are selected automatically by the OTDR. This is useful for inexperienced users, or experienced users who need to create a baseline trace quickly, but will result in an OTDR setup that is not optimized for most applications.  FIG. 2A  shows typical OTDR user settings in automatic mode. In the expert mode, most or all settings are selected by the user.  FIG. 2B  shows typical user settings in expert mode. Additional setting choices offered in the expert mode will allow experienced users to optimize the performance of their OTDR for specific applications, such as detecting and/or resolving closely spaced events or measuring the loss of a splice near the far end of the fiber network under test. 
     OTDR dynamic range is a key performance parameter. OTDR dynamic range is a function of pulse width, test duration, and OTDR signal processing parameters typically automatically selected by the OTDR based on pulse width, such as input amplifier and filter (analog, digital or both) bandwidth. Therefore, in the expert mode of a current art OTDR, the user determines dynamic range by selecting pulse width and test duration. For a given choice of distance range and wavelength, each pulse width/test duration combination corresponds with a given OTDR dynamic range. The higher the dynamic range, the smoother the OTDR trace, and therefore the better the loss measurement accuracy, which is needed to detect and measure low loss events, such as splices. The user can increase dynamic range by increasing pulse width, which coarsens event resolution, or increasing test duration, or both. Therefore, OTDR setup involves a tradeoff between dynamic range, event resolution, and test duration, but only test duration is a parameter available for viewing and adjustment on current art OTDRs. 
     The tradeoff between dynamic range and event resolution is explained with reference to  FIGS. 3A-3C .  FIG. 3A  shows an exemplary fiber network  70  being tested by an OTDR  72 . The network includes an input connection  73 , two connections  74 ,  75 , a splice  76  and a network termination  77 .  FIG. 3B  shows a trace  80  produced by the OTDR when a fine event resolution is chosen by the user. This trace  80  allows the user to clearly differentiate between the two connections, shown in  FIG. 3B  as events  81 ,  82 , but user cannot accurately measure the loss of the splice, which is a low loss event.  FIG. 3C  shows a trace  90  produced by the OTDR when a high dynamic range setup is chosen by the user. This trace  90  allows the user to accurately measure the loss of the splice, which is the downward sloping region  91  on the trace. However, the two connections are shown on the trace as a single event  92  rather than two separate events. 
     Pulse width is not the same as event resolution. The idealized relationship between OTDR trace event width in units of distance (d) and output pulse width in units of time (t) is d=ct/2n, where c=the speed of light in a vacuum and n is the fiber group index of refraction at the trace wavelength. This relationship is often approximated as d (m)=t (ns)/10, as discussed above. Common measures of event resolution, such as attenuation dead zone, are normally longer than the idealized trace event width because they include the effects of output pulse shape, input amplifier bandwidth, filtering (analog, digital, or both) and other OTDR characteristics. Therefore pulse width is not the most precise metric for representing event resolution. 
     Therefore there is a need for an OTDR that provides for the display and adjustment of dynamic range and a measure of event resolution in its users settings, that shows dynamic range in setup menus and ties this value to the current pulse width and test duration settings, that allow the user to change dynamic range directly and tie this new setting to event resolution and test duration, and that also allow the user to ‘lock’ any one of these settings, the one most important to the user in the given application, and then make trade-offs between the other two. 
     SUMMARY OF THE INVENTION 
     The present invention is an OTDR having an improved user interface, a software product for controlling the operation of the improved user interface, and a method of interfacing with an OTDR. 
     In its most basic form the OTDR of the present invention includes a user interface with a setup menu that includes a plurality of user settings, one of which is a setting that displays the dynamic range of a test. 
     It is preferred that the setup menu also include event resolution and test duration settings and that all three settings; dynamic range, event resolution, and test duration, be capable of receiving input from a user. Moreover, it is preferred that, when input is provided to one of the settings, the other settings adjust to show the effect of the input on the other parameters. It is also preferred that each of the dynamic range, event resolution, and test duration settings include a lock setting where a user can lock a value or range into one of the settings. Typically, the user will lock in the most important setting for his given application, and then make tradeoffs between the other two. For example, the user may lock in an event resolution and then choose a tradeoff between test duration and dynamic range, or the user may lock in a test duration, and then choose a tradeoff between the event resolution and the dynamic range. 
     It is also preferred that the settings be displayed in the setup menu using graphical controls, such as a slide switch. Such a graphical control presents the parameters as a range of possible values and the user may select different values by moving the control through the range, for example by sliding a slide switch from one position to another. When graphical controls are included and a setting has been locked, it is preferred that any limits imposed on the non-locked settings by the value or range locked into the locked setting be displayed on those non-locked settings. An example of such a display of a limit might be a block over a certain part of a range of a non-locked setting. For example, if event resolution is locked at a certain value, sections of the dynamic range control may no longer be available as an option for the user and would be blocked off so that that user could not slide a slide switch into the blocked sections. 
     In addition to the dynamic range, event resolution, and test duration settings, it is understood that the preferred user interface of the OTDR of the present invention also includes the standard settings for mode, wavelength, and distance range. The mode setting includes an option for an expert mode so that the user may take advantage of the options for setting input that are available with the improved user interface. 
     The event resolution setting may be for any metric for event resolution, such as pulse width, attenuation dead zone, and event dead zone. Pulse width is not preferred for the reasons discussed in the background, but may be included in some non-preferred embodiments of the present invention. However, it is preferred that an attenuation dead zone setting be one of the possible event resolution settings. Each event resolution/test duration pair for a given distance range and wavelength is associated with a given dynamic range. For a given wavelength, distance range, and test duration, the key performance tradeoff the user must make is between dynamic range and event resolution. For example, a user may select a fine resolution that will allow the OTDR to detect closely spaced events, but may not allow the OTDR to accurately measure low loss events, such as splices. On the other hand, a user may select a high dynamic range needed for measuring splice loss, but the resulting course event resolution may not be sufficient for separately detecting closely spaced events. In addition, test duration may be increased to improve dynamic range at a given event resolution or to improve event resolution for a given dynamic range. 
     These examples illustrate the balance that must be made between the dynamic range, event resolution, and test duration parameters. A skilled user must carefully tailor the balance for the specific requirements of the test, including the characteristics of the fiber network under test, the equipment being used for the test, and the goals of the test. With current art OTDR user interfaces, the dynamic range is not even displayed, let alone provided as a setting that may receive user input, and event resolution is generally displayed non-precisely as pulse width. However, with the OTDR of the present invention, which includes the improved user interface, the skilled user has all three settings available to allow him to appropriately balance the test parameters. 
     In its most basic form, the software product for controlling the operation of the improved user interface includes a setup menu code, which includes a plurality of sets of user setting code, including dynamic range setting code and dynamic range display code. The software product of the present invention is intended for use with a OTDR, which includes memory and control circuitry. In such embodiments, the software product is stored in the memory and executable by the control circuitry of the OTDR device. However, the software product may also be adapted for use in connection with OTDRs that are controlled by personal computers or other types of controllers, in which case the software product is stored in the memory of the controller and is executable by its microprocessor. 
     The setup menu code provides for a setup menu in the user interface of the OTDR. The setup menu code includes sets of user setting code that provide for the inclusion and display of specific user settings through the setup menu, including a dynamic range setting. The sets of user setting code preferably also include event resolution setting code and test duration setting code. Each of these sets of user setting codes includes display code providing for the display of the user setting in the setup menu. Each user setting code also preferably includes input code and effect code that allow a user to input values into the settings and see the effect on other settings upon the introduction of input into one setting. Each user setting code also preferably includes lock code which allows the user to lock one of the user settings at a time. Each user setting code also preferably includes graphical control code providing for a presentation of the settings as ranges of values. Finally, each user setting also preferably includes locked limit code. This code is included in embodiments that also include graphical control code, and provides for the indication of any limits imposed on a setting by the locking in of a certain value or range of another setting. Such limits are preferably indicated directly on the limited setting. 
     It is understood that the sets of user setting code also include mode setting code providing a mode setting in the setup menu, wavelength setting code providing for a wavelength setting in the setup menu, and distance range setting code providing for a distance range setting in the setup menu. The mode setting provides a selection of user modes, including expert mode. The wavelength setting provides a selection of lasers available in the OTDR to measure a fiber network under test, or allows for input of a laser wavelength. The distance range setting provides a selection of lengths of a fiber network under test, or allows for input of a length. 
     In its most basic form, the method of the present invention includes the steps of providing a dynamic range, an event resolution, or a test duration input into an OTDR user interface, observing the effect of the input provision on the other parameters, analyzing the optimization of the three parameters, repeating these steps until an optimally balanced set of parameters is indicated for the purpose of the test, and analyzing the results of the test with that optimally balanced set of parameters. The method also preferably includes the step of locking a value or range into one of the settings. 
     Therefore it is an aspect of the present invention to provide an OTDR having an improved user interface that displays dynamic range. 
     It is a further aspect of the present invention to provide an OTDR having an improved user interface that allows a user to input dynamic range. 
     It is a further aspect of the present invention to provide an OTDR having an improved user interface that displays event resolution. 
     It is a further aspect of the present invention to provide an OTDR having an improved user interface that adjusts a display of dynamic range, event resolution, and test duration to correspond with inputs among the three. 
     It is a further aspect of the present invention to provide an OTDR having an improved user interface that allows one of the dynamic range, event resolution, and test duration parameters to be locked. 
     It is a further aspect of the present invention to provide an OTDR having an improved user interface that uses a graphical control to show ranges of parameters. 
     It is a further aspect of the present invention to provide an OTDR having an improved user interface that displays limits imposed on ranges of parameters when another parameter is locked. 
     It is a further aspect of the present invention to provide a software product capable of presenting the features of an OTDR having the improved user interface. 
     It is a further aspect of the present invention to provide a method for optimizing a test using an OTDR device with an OTDR having an improved user interface of the present invention. 
    
    
     
       These aspects of the present invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, claims, and accompanying drawings. 
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing the functional blocks of a typical prior art OTDR. 
         FIG. 2A  is a depiction of typical prior art OTDR user settings in automatic mode. 
         FIG. 2B  is a depiction of typical prior art OTDR user settings in expert mode. 
         FIG. 3A  is a diagram of an OTDR testing a fiber network. 
         FIG. 3B  is a graph showing a trace of the fiber network of  FIG. 3A  produced by the OTDR when a fine event resolution is chosen by the user. 
         FIG. 3C  is a graph showing a trace of the fiber network of  FIG. 3A  produced by the OTDR when a high dynamic range is chosen by the user. 
         FIG. 4  is a depiction of OTDR user settings of the present invention. 
         FIG. 5A  is a depiction of an alternate embodiment of OTDR user settings of the present invention showing limits associated with locked parameters. 
         FIG. 5B  is a depiction of the alternative embodiment of OTDR user settings of the present invention that does not show limits associated with locked parameters. 
         FIG. 6  is a block diagram showing the features of the software product of the present invention. 
         FIG. 7  is a flow chart showing the steps of the method of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to  FIG. 4 , one embodiment of the user interface  10  of the OTDR of the present invention is shown. OTDR user interface  10  includes setup menu  12 , which includes setup mode setting  14 , wavelength setting  16 , distance range setting  18 , test duration setting  20 , event resolution setting  22 , and dynamic range setting  24 . In this embodiment, event resolution setting  22  is an attenuation dead zone setting. In other embodiments, event resolution setting  22  is a pulse width setting or other setting that correlates with event resolution. Each setting provides for data input, including mode input  35 , wavelength input  34 , distance range input  32 , test duration input  30 , event resolution input  28 , and dynamic range input  26 . Mode input  35  includes an option for expert mode  25 . If one of test duration input  30 , event resolution input  28 , and dynamic range input  26  is provided, the other two will automatically adjust to show the user the effect of the input of the one on the other two. To graphically indicate this linkage, a ‘chain’ symbol and lines  31  are shown next to the test duration, event resolution, and dynamic range settings. 
     Now referring to  FIG. 5A , another embodiment of the user interface  10  with setup menu  12  is shown. In this embodiment, test duration setting  20 , event resolution setting  22 , and dynamic range setting  24  are shown with graphical controls  26 ,  28 ,  30 . Test duration graphical control  30 , event resolution graphical control  28 , and dynamic range graphical control  26  indicate a range of possible test durations, event resolutions, and dynamic ranges, respectively. The user may use the graphical controls  26 ,  28 ,  30  to move through test duration range  52 , event resolution range  50 , and/or dynamic range  48 . As with the embodiment shown in  FIG. 4 , as one parameter is shifted, the others will shift to indicate the effect of the change of the first parameter on the other two. 
     This embodiment of the user interface  10  also includes lock test duration setting  36 , lock event resolution setting  38 , and lock dynamic range setting  40 . Only one of these lock settings  36 ,  38 ,  40  is selectable at a time, and its selection locks in the test duration, event resolution, or dynamic range chosen by the user. This allows the user to then make tradeoffs between the other two parameters while keeping the most important parameter for that particular test locked. In  FIG. 5A , event resolution setting  22  has been locked. This embodiment also indicates any limits that are imposed on non-locked settings when another setting is locked. In this case, with event resolution setting  22  locked at 2 km, limit  54  is imposed on dynamic range setting  24 , indicating to the user that the upper and lower limit of dynamic range setting  24  at 1310 and 1550 nm with a 2 km event resolution are 32/30 dB and 28/26 dB respectively. Limit  54  blocks off the remainder of the setting so that it is not possible to set the dynamic range setting  24  outside the allowed section when the event resolution setting  22  is locked at 2 km.  FIG. 5B  shows the same user interface  10 , where no parameter has been locked so no limits are imposed. 
     It is noted that, although two embodiments of the user interface  10  have been shown in  FIGS. 4 ,  5 A, and  5 B, there are a wide variety of ways in which the same data may be presented. For example, the data may be shown in the form of circular pie charts for the various parameters, in a series of graphs, or in any other manner known in the art of graphical display. Further, although there are no locks or limits shown in the embodiment of  FIG. 4 , it is also recognized that such locks and/or limits may be incorporated therein. Accordingly, the user interface  10  should not be seen as being so limited. 
     Now referring to  FIG. 6 , the features of OTDR software product  100  are shown. OTDR software product  100  includes setup menu code  101 , which provides for a setup menu. Setup menu code  101  includes a plurality of sets of user setting code, including dynamic range setting code  102 , event resolution setting code  104 , test duration setting code  106 , wavelength setting code  110 , distance range setting code  112 , and mode setting code  108 . These plurality of sets of user setting code provide for a dynamic range setting, an event resolution setting, a test duration setting, a wavelength setting, a distance range setting, and a mode setting, respectively. Dynamic range setting code  102  includes dynamic range display code  110 , dynamic range input code  112 , dynamic range effect code  114 , lock dynamic range code  116 , dynamic range graphical control code  117 , and locked dynamic range limit code  118 . Event resolution setting code  104  includes event resolution display code  120 , event resolution input code  122 , event resolution effect code  124 , lock event resolution code  126 , event resolution graphical control code  128 , and locked event resolution limit code  130 . Test duration setting code  106  includes test duration display code  132 , test duration input code  134 , test duration effect code  136 , lock test duration code  138 , test duration graphical control code  140 , and locked test duration limit code  142 . Each display code  110 ,  120 ,  132  provides for the display of the user setting. Each input code  112 ,  122 ,  134  provides for the introduction of user input into each user setting. Each effect code  114 ,  124 ,  136  provides for the indication of the effect on the other user settings when one user setting receives input. Each lock code  116 ,  126 ,  138  provides the ability for the user to lock one of the user settings into a certain value or range at a time. Each graphical control code  117 ,  128 ,  140  provides for the user settings to be presented using graphical controls that display a range for each setting. Each locked limit code  118 ,  130 ,  142  provides for the indication of any limits imposed on a non-locked user setting by the locking of a certain value or range into another setting. Mode setting code  108  includes expert mode code  144  providing for an expert mode as a selection within the mode setting. 
     Now referring to  FIG. 7 , the steps of method  300  of the present invention are shown. Method  300  is for optimizing OTDR performance on an OTDR device that includes OTDR user interface  10  of the present invention. Method  300  includes the steps of providing one of the dynamic range input, the event resolution input, and the test duration input  301 ; observing the effect of the input provided on the other two parameters  302 ; analyzing the optimization of the three parameters  304 ; repeating the steps of providing an input, observing the effect, and analyzing the optimization until an optimal set of parameters is achieved  306 ; and analyzing the results of the test with the optimal set of parameters  308 . Method  300  may also include the step of locking in a parameter  310  by selecting one of the lock dynamic range setting, the lock pulse width setting, and the lock test time setting. 
     Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions would be readily apparent to those of ordinary skill in the art. Therefore, the spirit and scope of the description should not be limited to the description of the preferred versions contained herein.