Patent Publication Number: US-11650127-B2

Title: Optical time-domain reflectometer device including combined trace display

Description:
PRIORITY 
     This application is a Continuation of U.S. patent application Ser. No. 16/791,889 filed Feb. 14, 2020, which is a Continuation of commonly assigned U.S. patent application Ser. No. 16/121,215, filed Sep. 4, 2018, now U.S. Pat. No. 10,598,566, issued Mar. 24, 2020, which claims priority to U.S. patent application Ser. No. 15/862,526, filed Jan. 4, 2018, now U.S. Pat. No. 10,101,240, issued Oct. 16, 2018, which claims priority to French Application Serial No. 1753714, filed Apr. 27, 2017, and entitled “OPTICAL FIBER SENSOR INCLUDING COMBINED TRACE DISPLAY”, the disclosures of which are hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     An optical fiber may be characterized by a sensor that injects optical pulses into the optical fiber. Based on the injected optical pulses, the sensor may extract light that is scattered or reflected back from points along the optical fiber. The scattered or reflected light that is gathered back may be used to characterize the optical fiber. For example, the scattered or reflected light that is gathered back may be used to detect, locate, and measure events at any location of the optical fiber. The events may include faults at any location of the optical fiber. Other types of features that may be measured by the sensor include attenuation uniformity and attenuation rate, segment length, and location and insertion loss of connectors, splices, or any other optical components such as splitters or multiplexers. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Features of the present disclosure are illustrated by way of examples shown in the following figures. In the following figures, like numerals indicate like elements, in which: 
         FIG.  1    illustrates an architecture of an optical time-domain reflectometer (OTDR) device, according to an example of the present disclosure; 
         FIG.  2    illustrates a sensor display of multiple pulse acquisitions including five traces displayed for five pulses for one wavelength, according to an example of the present disclosure; 
         FIG.  3    illustrates a sensor display of multiple pulse acquisitions including a single combined trace generated with three trace sections for one wavelength, according to an example of the present disclosure; 
         FIG.  4    illustrates a sensor display of multiple pulse acquisitions including two single combined traces with one combined trace per wavelength, according to an example of the present disclosure; 
         FIG.  5    illustrates a sensor display of optical events identified using a 300 ns pulse, according to an example of the present disclosure; 
         FIG.  6    illustrates a sensor display at combined trace section [S 1 ] associated with a pulse that encompasses an event # 4  and an event # 6  and is extended to existing neighboring event # 3 , according to an example of the present disclosure; 
         FIG.  7    illustrates a sensor display including overlapping trace sections, according to an example of the present disclosure; 
         FIG.  8    illustrates a sensor display including no overlapping trace sections, according to an example of the present disclosure; 
         FIG.  9    illustrates a sensor display including creation of sub-sections, according to an example of the present disclosure; 
         FIG.  10    illustrates a sensor display which may be used for algorithm based (e.g., interpolation based) creation of sub-sections, according to an example of the present disclosure; 
         FIG.  11    illustrates a sensor display including algorithm based creation of sub-sections, according to an example of the present disclosure; 
         FIG.  12    illustrates a sensor display including length reduction of algorithm based sub-sections, according to an example of the present disclosure; 
         FIG.  13    illustrates a sensor display including length reduction of algorithm based sub-sections, according to an example of the present disclosure; 
         FIG.  14    illustrates a sensor display including discontinuous trace sections, according to an example of the present disclosure; 
         FIG.  15    illustrates a sensor display including algorithm based creation of sub-sections, according to an example of the present disclosure; 
         FIG.  16    illustrates a sensor display including a weighted arithmetic mean algorithm based creation of sub-sections, according to an example of the present disclosure; 
         FIG.  17    illustrates a sensor display including a dual linear regression algorithm based creation of sub-sections, according to an example of the present disclosure; 
         FIG.  18    illustrates a sensor display including section slopes with respect to the dual linear regression algorithm based creation of sub-sections, according to an example of the present disclosure; 
         FIG.  19    illustrates a sensor display including a section [S] generated using the dual linear regression algorithm based creation of sub-sections, according to an example of the present disclosure; 
         FIG.  20    illustrates a sensor display including a section [S] generated using a De Casteljau&#39;s algorithm based creation of sub-sections, according to an example of the present disclosure; and 
         FIG.  21    illustrates a computer system, according to an example of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     For simplicity and illustrative purposes, the present disclosure is described by referring mainly to examples thereof. In the following description, details are set forth in order to provide an understanding of the present disclosure. It will be readily apparent however, that the present disclosure may be practiced without limitation to these details. In other instances, some methods and structures have not been described in detail so as not to unnecessarily obscure the present disclosure. 
     Throughout the present disclosure, the terms “a” and “an” are intended to denote at least one of a particular element. As used herein, the term “includes” means includes but not limited to, the term “including” means including but not limited to. The term “based on” means based at least in part on. 
     An optical time-domain reflectometer (OTDR) is an optoelectronic instrument used to characterize an optical fiber. The OTDR may inject a series of optical pulses into an optical fiber under test. Based on the injected optical pulses, the OTDR may extract, from the same end of the optical fiber in which the optical pulses are injected, light that is scattered or reflected back from points along the optical fiber. The scattered or reflected light that is gathered back may be used to characterize the optical fiber. For example, the scattered or reflected light that is gathered back may be used to detect, locate, and measure events at any location of the optical fiber. The events may include faults at any location of the optical fiber. Other types of features that may be measured by the OTDR include attenuation uniformity and attenuation rate, segment length, and location and insertion loss of connectors, splices, or any other optical components such as splitters or multiplexers. 
     Optical networks may include topologies for which multiple pulse widths, and/or multiple pulse widths and wavelengths need to be injected, for example, by an OTDR, in order to detect and characterize optical events along the optical fiber. In this regard, an OTDR measurement may be represented by a trace showing backscattering power over the distance of the optical fiber. Each trace may be processed to localize and characterize the optical events. 
     When multiple acquisitions are performed by an OTDR, the number of traces displayed on a screen increases. This increases the complexity of trace analysis for a user. 
     In order to address at least these aspects of trace analysis, the disclosed optical time-domain reflectometer (OTDR) device provides a combined trace based on all of the multiple pulse widths, and/or multiple pulse widths and wavelengths. For example, the combined trace may include a single trace based on all of the multiple pulse widths, and/or multiple pulse widths and wavelengths. In this regard, the combined trace may include a single trace based on all of the multiple pulse widths, and/or multiple pulse widths and wavelengths. Alternatively, the disclosed OTDR device provides a reduced number of combined traces based on all of the multiple pulse widths, and/or multiple pulse widths and wavelengths. In this regard, the combined traces may include a reduced number of traces compared to the number of pulse widths, and/or pulse widths and wavelengths injected into the optical fiber. 
     According to an example, with respect to OTDR acquisitions using multiple pulse widths, and/or multiple pulse widths and wavelengths, the disclosed OTDR device may provide a single combined trace instead of multiple traces associated with the multiple OTDR acquisitions. The combined trace may be formed of different trace sections. For example, a trace section may be selected from any of the traces obtained for each pulse width and/or each pulse width and wavelength used during the acquisition. The trace section may also be generated based on specified processing (e.g., algorithms) as disclosed herein. 
       FIG.  1    illustrates an architecture of an OTDR device  100  (hereinafter referred to as “OTDR device  100 ”), according to an example of the present disclosure. 
     Referring to  FIG.  1   , the OTDR device  100 , which may be an OTDR, may include emitting laser diode (or a plurality of emitting laser diodes)  102  to generate light by an electrical current. The emitting laser diode  102  may include a semiconductor. A pulse generator  104  may control a laser diode which sends light pulses into an optical fiber  106  under test (also designated device under test (DUT)). A time base control unit  108  may control operations of the OTDR device  100 . A sensor display  110  may display measured characteristics of the optical fiber  106 , for example, in the form of traces and other attributes as disclosed herein. A photodiode detector  112  may analyze the return signal from the optical fiber  106  under test to generate a signal proportional to the intensity of an optical field. A sampling ADC averaging block at  114  may be analyze the amplified return signal from amplifier  116  to generate the display at the sensor display  110 . 
     According to examples, the emitting laser diode  102  may emit a plurality of laser beams. Each laser beam may include a different pulse width. For example, as disclosed herein with respect to  FIG.  2   , each laser beam may include pulse widths of 1 μs, 300 ns, 100 ns, 30 ns, and 10 ns. 
     The time base control unit  108  may analyze, for each laser beam, a backscattered signal from a DUT. For example, the DUT may include the optical fiber  106 . The time base control unit  108  may generate, for each backscattered signal, a trace along the DUT. Further, the time base control unit  108  may generate, based on an analysis of each trace along the DUT, a combined trace that identifies optical events detected along the DUT. In this regard, the combined trace may be formed of different trace sections, where the trace sections may be selected from any of the traces obtained for each pulse width and/or each pulse width and wavelength used during the acquisition. Alternatively or additionally, the trace sections may be generated based on specific algorithms as disclosed herein. Further, the acquisitions may be based on several pulse widths and several wavelengths to provide as many combined traces as the number of wavelengths used. Moreover, for a given trace (following an acquisition for a given pulse width) a single trace section or a plurality of non-adjacent trace sections may be determined. 
     According to examples, the time base control unit  108  may generate, based on the analysis of each trace along the DUT, the combined trace that identifies optical events detected along the DUT by determining, for each analyzed trace along the DUT, whether a respective trace section of an analyzed trace may be included in the combined trace. Based on a determination that the respective trace section of the analyzed trace is to be included in the combined trace, the time base control unit  108  may include the respective trace section in the combined trace. Further, based on a determination that the respective trace section of the analyzed trace is to not be included in the combined trace, the time base control unit  108  may exclude the respective trace section from the combined trace. 
     According to examples, the time base control unit  108  may determine, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace is to be included in the combined trace by determining, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace includes an optical event. Further, based on a determination that the respective trace section of the analyzed trace includes the optical event, the time base control unit  108  may include the respective trace section in the combined trace. Thus, for a given pulse width, a trace section may be retained as soon as at least one optical event has been detected on the trace corresponding to this pulse width. 
     According to examples, the time base control unit  108  may determine, for a respective trace section included in the combined trace, whether a further trace section is adjacent to an optical event for the respective trace section included in the combined trace. Further, based on a determination that the further trace section is adjacent to the optical event for the respective trace section included in the combined trace, the time base control unit  108  may determine, for the combined trace, a single point that accounts for the further trace section and the optical event for the respective trace section included in the combined trace. Thus, in order to avoid any overlapping trace sections at a given point, various algorithms may be applied to determine a single point at a given position. According to various criteria (e.g., quality criteria) and for a given position, a single acquisition point may be selected on a trace section Sn and displayed to provide a single combined trace. The criteria in this regard may be derived, for example, from optical event position, event dead zone, attenuation dead zone, splitter attenuation dead zone, noise level or peak to peak noise (local noise), pulse width dynamics, etc. Further, on the overlapping area, according to quality criteria, several sub sections that are derived from initial trace sections may be generated. For a defined trace section, dedicated algorithms may be used when two trace sections are discontinuous (e.g., to join two different trace sections from two different pulse widths), or no trace section of an overlapping area meets a quality criteria. In this regard, the quality criteria may be derived, for example, from event dead zone, attenuation dead zone, splitter attenuation dead zone, noise level or peak to peak noise (local noise), optical event parameter (attenuation, reflectance, distance . . . ), pulse width dynamics, etc. 
     According to examples, the time base control unit  108  may determine, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace is to be included in the combined trace by determining, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace includes a plurality of optical events. Based on a determination that the respective trace section of the analyzed trace includes the plurality of optical events, the time base control unit  108  may include the respective trace section in the combined trace. Thus, for a given pulse width, a trace section may encompass the position(s) of the different events identified on the trace corresponding to the pulse width. 
     According to examples, the time base control unit  108  may determine, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace is to be included in the combined trace by determining, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace meets a quality criterion. Based on a determination that the respective trace section of the analyzed trace does not meet the quality criterion, the time base control unit  108  may exclude the respective trace section from the combined trace. Thus, the traces without any relevant information related to optical events may not be displayed. 
     According to examples, the time base control unit  108  may generate, based on the analysis of each trace along the DUT, the combined trace that identifies optical events detected along the DUT by interpolating a combined trace section between two non-adjacent combined trace sections of the combined trace to form the combined trace. 
     According to examples, the pulse width of one of the two non-adjacent combined trace sections may be different from the pulse width of another one of the two non-adjacent combined trace sections. 
     According to examples, the time base control unit  108  may reduce a length of the interpolated combined trace section by including, from an analyzed trace, an intermediate section that does not include an optical event. 
     According to examples, the time base control unit  108  may generate, based on the analysis of each trace along the DUT, the combined trace that identifies optical events detected along the DUT by determining, for each analyzed trace along the DUT, whether a respective trace section of an analyzed trace is to be included in the combined trace. Based on a determination that no respective trace section of the analyzed trace meets a quality criteria, the time base control unit  108  may interpolate a combined trace section where no respective trace section is included in the combined trace. 
     According to examples, the time base control unit  108  may generate, based on the analysis of each trace along the DUT, the combined trace that identifies optical events detected along the DUT by selecting, based on the analysis of each trace along the DUT, a plurality of trace sections from the analyzed traces. Further, the time base control unit  108  may connect the selected plurality of trace sections to generate the combined trace. 
     According to examples, the laser source (e.g., the emitting laser diode  102 ) may emit a further laser beam including a further different pulse width. The time base control unit  108  may analyze, for the further laser beam, a further backscattered signal from the DUT. Further, the time base control unit  108  may generate, for the further backscattered signal, a further trace along the DUT. The time base control unit  108  may update, based on a further analysis of the further trace along the DUT, the combined trace that identifies the optical events detected along the DUT. Thus, the combined trace may be updated after each new acquisition using a different pulse width. 
     According to examples, the emitting laser diode  102  may emit a first set of a plurality of laser beams, with each laser beam of the first set including a different pulse width and a first specified wavelength (e.g., 1550 nm as disclosed herein with respect to  FIG.  4   ). Further, the emitting laser diode  102  may emit a second set of a plurality of laser beams, with each laser beam of the second set including a different pulse width and a second specified wavelength (e.g., 1310 nm as disclosed herein with respect to  FIG.  4   ). In this regard, the time base control unit  108  may analyze, for each laser beam of the first set and the second set, a backscattered signal from the DUT. The time base control unit  108  may generate, for each backscattered signal for the first set and the second set, a trace along the DUT. The time base control unit  108  may generate, based on an analysis of each trace along the DUT, a first combined trace that identifies optical events detected along the DUT for the first set, and a second combined trace that identifies optical events detected along the DUT for the second set. 
       FIG.  2    illustrates a sensor display of multiple pulse acquisitions including five traces displayed for five pulses for one wavelength, according to an example of the present disclosure. 
     Referring to  FIG.  2   , the pulses may include pulse widths 1 μs, 300 ns, 100 ns, 30 ns, and 10 ns. As shown in  FIG.  2   , the acquisitions for pulse widths 1 μs, 300 ns, and 100 ns may taper after approximately 150 m, whereas the acquisitions for pulse widths 30 ns and 10 ns may become distorted after approximately 130 m. The events at “2” and “3” may represent various types of events along the optical fiber  106  under test, such as faults, connections, splices, etc. 
       FIG.  3    illustrates a sensor display of multiple pulse acquisitions including a single combined trace generated with three trace sections for one wavelength, according to an example of the present disclosure. 
     Referring to  FIG.  3   , as disclosed herein, the time base control unit  108  may generate, based on an analysis of each trace along the DUT, a combined trace that identifies optical events detected along the DUT. In this regard, the display traces for the pulse widths 1 μs, 300 ns, 100 ns, 30 ns, and 10 ns may be combined into a single combined trace  300 . The single combined trace  300  may include a trace section # 1 , a trace section # 2 , and a trace section # 3 . Trace sections # 1  and # 3  may be determined (e.g., by the time base control unit  108  that operates in conjunction with the sampling ADC averaging block at  114 ) by selecting traces (i.e., trace portions) associated to each pulsewidth. For example, trace section # 1  may be composed of the portion of the trace for the 30 ns pulse width from 0 m to approximately 120 m (e.g., including event # 2  and event # 3 ). Trace section # 2  may be determined (e.g., by the time base control unit  108  that operates in conjunction with the sampling ADC averaging block at  114 ) by a specific algorithm, as disclosed herein. For example, trace section # 2  may be determined by applying a tapering process beyond section # 1  from approximately 125 m along the optical fiber (e.g., from event # 3 ) to approximately 175 m. Further, trace section # 3  may be determined from selecting a portion of the 300 ns trace from approximately 175 m to an end of the optical fiber. 
       FIG.  4    illustrates a sensor display of multiple pulse acquisitions including two single combined traces with one combined trace per wavelength, according to an example of the present disclosure. 
     Referring to  FIG.  4   , as disclosed herein, the emitting laser diode  102  may emit a first set of a plurality of laser beams, with each laser beam of the first set including a different pulse width and a first specified wavelength (e.g., 1550 nm). Further, the emitting laser diode  102  may emit a second set of a plurality of laser beams, with each laser beam of the second set including a different pulse width and a second specified wavelength (e.g., 1310 nm). In this regard, the time base control unit  108  may analyze, for each laser beam of the first set and the second set, a backscattered signal from the DUT. The time base control unit  108  may generate, for each backscattered signal for the first set and the second set, a trace along the DUT. The time base control unit  108  may generate, based on an analysis of each trace along the DUT, a first combined trace (e.g., at  400 ) that identifies optical events detected along the DUT for the first set, and a second combined trace (e.g., at  402 ) that identifies optical events detected along the DUT for the second set. 
     Thus, referring to  FIG.  4   , the acquisitions may be based on several pulse widths and several wavelengths to provide as many combined traces as the number of wavelengths used. The multiple pulse acquisitions may be based on nine traces displayed, with five pulses used for 1550 nm (e.g., the first set), and four pulses used for 1310 nm (e.g., the second set). For example, combined trace  400  may represent a combined trace based on five pulses (e.g., 1 μs, 300 ns, 100 ns, 30 ns, and 10 ns) used for 1550 nm, and combined trace  402  may represent a combined trace based on four pulses (e.g., 300 ns, 100 ns, 30 ns, and 10 ns) used for 1310 nm. 
     According to an example, the combined trace (e.g., the combined trace  300 , or the combined traces  400  and  402 ) may be determined (e.g., by the time base control unit  108  that operates in conjunction with the sampling ADC averaging block at  114 ) once the second acquisition is completed, and thereafter, after each new acquisition using a different pulse width. 
     For example, for a Wavelength 1, the combined trace may be determined as follows: 
     Wavelength 1: Pulse 1→Pulse 2→Single Combined Trace→Pulse 3→Combined Trace Updated→Pulse 4→Combined Trace Updated, etc. 
     For a Wavelength 2, the combined trace may be determined as follows: 
     Wavelength 2: Pulse 1→Pulse 2→Single Combined Trace→Pulse 3→Combined Trace Updated→Pulse 4→Combined Trace Updated, etc. 
     As disclosed herein, the time base control unit  108  may generate, based on the analysis of each trace along the DUT, the combined trace that identifies optical events detected along the DUT by determining, for each analyzed trace along the DUT, whether a respective trace section of an analyzed trace may be included in the combined trace. Thus, based on a determination that the respective trace section of the analyzed trace is to not be included in the combined trace, the time base control unit  108  may exclude the respective trace section from the combined trace. In this regard, the traces and/or trace sections without any relevant information related to optical events may not be displayed. For example, for  FIGS.  2  and  3   , all traces and trace sections, other than trace section # 1 , trace section # 2 , and trace section # 3 , are not displayed in  FIG.  3   . 
     With respect to trace section definition (e.g., see sections # 1 , # 2 , and # 3  of  FIG.  3   ), a trace section may be defined by parameters that include a section origin, and a section length. These parameters may be expressed in distance and/or time units. Trace sections may be selected from any traces obtained for each pulse width used during an acquisition. Trace sections may also be determined by specific algorithms. For example, the specific algorithms may include interpolation algorithms that interpolate from an extremity of one trace section (e.g., see trace section # 1  in  FIG.  3   ) to an origin of another trace section (e.g., see section # 3  in  FIG.  3   , where trace section # 2  of  FIG.  3    is interpolated). The interpolation may be based on best fit, averaging, etc., to provide a smooth transition between trace sections. 
     For a given trace (following an acquisition for a given pulse width), a single trace section or a plurality of non-adjacent trace sections may be determined (e.g., see single trace section # 1  of  FIG.  3   ). If a trace section is not useful, the trace section (or no trace sections) for a trace may be retained. For example, in  FIGS.  2  and  3   , no trace sections of the 10 ns trace are used to generate the combined trace. 
     With respect to trace section determination, examples of criteria that may be used to determine a trace section may include optical events detection at a given position, noise level, peak to peak noise measured at a given location, event dead zone, attenuation dead zone, etc. For example, in  FIGS.  2  and  3   , the optical events at “2” and “3” are used to determine the trace section # 1 . As shown in  FIG.  2   , the noise level (for the pulse with 10 ns) may be used to determinate the end of the section # 1 . The dead zone (e.g., attenuation or event dead zone) may be used to determinate the beginning of a given section. For example, as shown in  FIGS.  2  and  3   , the start point of the section # 3  may be derived from the event dead zone from the 300 ns pulse width. 
     As disclosed herein, the time base control unit  108  may determine, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace is to be included in the combined trace by determining, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace includes an optical event. Further, based on a determination that the respective trace section of the analyzed trace includes the optical event, the time base control unit  108  may include the respective trace section in the combined trace. For example, for a given pulse width, a trace section may be retained as soon as at least one optical event has been detected on the trace corresponding to the pulse width. For example, in  FIGS.  2  and  3   , the trace section # 1  may be retained based on the detection of the optical events at “2” and “3”. 
     As disclosed herein, the time base control unit  108  may determine, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace is to be included in the combined trace by determining, for each analyzed trace along the DUT, whether the respective trace section of the analyzed trace includes a plurality of optical events. Based on a determination that the respective trace section of the analyzed trace includes the plurality of optical events, the time base control unit  108  may include the respective trace section in the combined trace. For example, for a given pulse width, the trace section may encompass the position(s) of the different events identified on the trace corresponding to the pulse width. For example, in  FIGS.  2  and  3   , the trace section # 1  may encompass the positions of the optical events at “2” and “3”. 
     For a given pulse width, the section may then be extended to the position of the neighboring optical events identified during the previous acquisitions. Thus, several sections may also overlap. 
       FIG.  5    illustrates a sensor display of optical events identified using a 300 ns pulse, according to an example of the present disclosure. 
     Referring to  FIG.  5   , optical events # 4  and # 6  may be identified using the 300 ns pulse. Optical event # 4  and optical event # 6  may represent different events as shown at  500  (e.g., a fiber connection) and  502  (a fiber end). The display of  FIG.  5    may include other types of information such as the distance of an event, loss (dB) at an event, slope of the optical fiber at an event, a length of a particular section, etc. 
       FIG.  6    illustrates a sensor display at combined trace section [S 1 ] associated with a pulse that encompasses an event # 4  and an event # 6  and is extended to existing neighboring event # 3 , according to an example of the present disclosure. 
     Referring to  FIG.  6   , the section [S 1 ] associated with the pulse width of 1550 nm encompasses the event # 4  at  600  and the event # 6  at  602 , and is extended to existing neighboring events (# 3  at  604  and # 6  (last optical event identified in this case)). 
       FIG.  7    illustrates a sensor display including overlapping trace sections, according to an example of the present disclosure. 
     Referring to  FIG.  7   , overlapping sections are displayed between the range identified at  700 . For example, the range identified at  700  includes sections for traces  702  and  704 . 
       FIG.  8    illustrates a sensor display including no overlapping trace sections, according to an example of the present disclosure. 
     Referring to  FIGS.  7  and  8   , as disclosed herein, the time base control unit  108  may determine, for a respective trace section included in the combined trace, whether a further trace section is adjacent to an optical event (e.g., see optical event at  706  for traces  702  and  704 ) for the respective trace section included in the combined trace. Further, based on a determination that the further trace section is adjacent to the optical event for the respective trace section included in the combined trace, the time base control unit  108  may determine, for the combined trace, a single point (e.g., see corresponding single point at  806  in  FIG.  8   ) that accounts for the further trace section and the optical event for the respective trace section included in the combined trace. 
     In this regard, referring to  FIG.  8   , section # 1   b  (pulse width # 1 ) is displayed at  800 , and section # 2   b  (pulse width # 4 ) is displayed at  802 . As shown at  804 , the sensor display includes no overlapping trace sections. In order to avoid any overlapping trace sections at a given point (as shown in  FIG.  7   ), various algorithms may be applied to determine a single point at a given position. For example, according to various criteria (e.g., quality criteria) and for a given position, a single acquisition point may be selected on a section Sn and displayed to provide a single combined trace. The criteria in this regard may be derived, for example, from optical event position, optical event section link, event dead zone, attenuation dead zone, splitter attenuation dead zone, peak to peak noise (local noise), noise level, pulse width used, and/or dynamics of the pulse width used. As shown in  FIGS.  7  and  8   , the peak to peak noise may be lower on the acquisition trace  702  than the acquisition trace  704 , and thus the section trace may be derived from trace  704  and not trace  702 . 
       FIG.  9    illustrates a sensor display including creation of sub-sections, according to an example of the present disclosure. 
     Referring to  FIG.  9   , section # 1   b  may be based on pulse width # 1 , trace section # 2   b  may be based on pulse width # 4 , and trace section # 1   c  may be based on pulse width # 1 . In this regard, based on the overlapping area, according to quality criteria, several sub-sections that are derived from initial sections (e.g., multiple sections created from the same trace) may be generated. 
       FIG.  10    illustrates a sensor display which may be used for algorithm based (e.g., interpolation based) creation of sub-sections, according to an example of the present disclosure. 
     Referring to  FIG.  10   , trace section # 1  may be based on pulse width # 1 , trace and section # 2  may be based on pulse width # 4 . In this regard, as disclosed herein in further detail with respect to  FIGS.  14 - 20   , sections (or a section) that join trace section # 1  and trace section # 2  may be generated, for example, by using dedicated algorithms, if no section of the overlapping area meets the quality criteria. The algorithms may include, for example, interpolation algorithms that provide a best fit between adjacent sections. 
       FIG.  11    illustrates a sensor display including algorithm based creation of sub-sections, according to an example of the present disclosure. 
     With reference to  FIGS.  10  and  11   , for  FIG.  11   , trace section # 3  and trace section # 4  may be generated, for example, by using dedicated algorithms, since no section of the overlapping area meets the quality criteria. As disclosed herein in further detail with respect to  FIGS.  14 - 20   , the algorithms may include, for example, interpolation algorithms that provide a best fit between adjacent sections. 
       FIG.  12    illustrates a sensor display including length reduction of algorithm based sub-sections, according to an example of the present disclosure. Further,  FIG.  13    illustrates a sensor display including length reduction of algorithm based sub-sections, according to an example of the present disclosure. 
     Referring to  FIG.  12   , in order to reduce the length of algorithm based sub-sections, additional intermediate sections may be generated from traces (e.g., curves as indicated in  FIG.  12   ) where no optical event has been previously identified. The length of algorithm based sub-sections may be reduced, for example, using acquisition points from other (e.g., lower) pulse widths up to the initial attenuation dead zone of the given pulse width. For example, compared to  FIG.  12   ,  FIG.  13    includes section # 3  that is generated from traces where no optical event has been previously found. Further, two additional sections # 5  and # 6  may be obtained from pulse width # 2  and pulse width # 3 . 
       FIG.  14    illustrates a sensor display including discontinuous trace sections, according to an example of the present disclosure. 
     Referring to  FIG.  14   , as disclosed herein, the time base control unit  108  may generate, based on the analysis of each trace along the DUT, the combined trace that identifies optical events detected along the DUT by interpolating a combined trace section between two non-adjacent combined trace sections of the combined trace to form the combined trace. Additionally or alternatively, the time base control unit  108  may generate, based on the analysis of each trace along the DUT, the combined trace that identifies optical events detected along the DUT by determining, for each analyzed trace along the DUT, whether a respective trace section of an analyzed trace is to be included in the combined trace. Based on a determination that no respective trace section of the analyzed trace meets a quality criteria, the time base control unit  108  may interpolate a combined trace section where no respective trace section is included in the combined trace. 
     As shown in  FIG.  14   , in order to join two different trace sections that are based on two different pulse widths, the interpolation may be based on dedicated algorithms. The algorithms may be used when two sections are discontinuous (e.g., sections S 1  and S 2  as shown respectively at  1400  and  1402  in  FIG.  14   ), and/or when no section of an overlapping area meets a quality criteria. 
     The quality criteria may be derived from event (e.g., optical event) dead zone, attenuation dead zone, splitter attenuation dead zone, noise level or peak to peak noise (local noise), optical event parameter (attenuation, reflectance, distance, etc.), pulse width dynamics, etc. 
       FIG.  15    illustrates a sensor display including algorithm based creation of sub-sections, according to an example of the present disclosure. 
     As shown in  FIG.  15   , the time base control unit  108  may implement algorithms to join two sections issued from a short pulse (e.g., the pulse at  1500 ) and a long pulse (e.g., the pulse at  1502 ) when the short pulse is not strong enough to reach the end of the optical network (e.g., fiber end) because of the pulse width dynamics. Alternatively or additionally, the time base control unit  108  may implement algorithms to join two sections issued from a short pulse (e.g., section S 2  of  FIG.  14   ) and a long pulse (e.g., section S 1  of  FIG.  14   ) when the long pulse is too large to be able to detect/measure the optical events (e.g., because of the initial dead zone, attenuation dead zone, splitter attenuation dead zone, etc.). The time base control unit  108  may apply algorithms to the overlap area, or may apply algorithms to an extended area that totally or partially includes the overlap area. 
       FIG.  16    illustrates a sensor display including a weighted arithmetic mean algorithm based creation of sub-sections, according to an example of the present disclosure. 
     Referring to  FIG.  16   , the time base control unit  108  may apply the weighted arithmetic mean algorithm by analyzing a short pulse trace to measure the noise level (quality criteria), and define two thresholds. The first threshold may include an upper level at  1600  to be above the noise level (e.g., +6 dB for example) at  1602 , and the second threshold may include a lower level at  1604  to be, for example, 2 dB under the upper level. The time base control unit  108  may determine a first point used by the weighted arithmetic mean algorithm to be the intersection point of the shorter pulse trace with the upper level threshold. Further, the time base control unit  108  may determine a last point used by the weighted arithmetic mean algorithm to be the intersection point of the larger pulse trace and the lower level threshold. The time base control unit  108  may implement an algorithm to combine the traces between these two points as a weighted average of the points of each curve, where some points contribute more than others. 
     For the weighted arithmetic mean algorithm, the weighting may be defined by first considering that the data from the short pulse width contribute more than the data from the long pulse width (e.g., high weight) at the beginning of the algorithm area. Further, for the weighted arithmetic mean algorithm, the weighting may be defined by further considering that the data from the long pulse width contribute more than the data from the short pulse width (e.g., high weight) at the end of the algorithm area. For example, as shown at  1606 , the algorithm area may include 100 points for which the weight may be defined as shown. In this regard, the time base control unit  108  may determine the section “S” at  1608  using the weighted arithmetic mean algorithm. 
       FIG.  17    illustrates a sensor display including a dual linear regression algorithm based creation of sub-sections, according to an example of the present disclosure. 
     Referring to  FIG.  17   , the time base control unit  108  may implement a dual linear regression algorithm instead of the weighted arithmetic mean algorithm of  FIG.  16   . For the dual linear regression algorithm, the time base control unit  108  may define two slopes (e.g., one for each trace section) and determine the intersection point of these two lines. Slope determination for a given area may be based on linear regression on a pre-determined sub-section which may consider quality criteria based, for example, on optical events parameters (distance, attenuation, reflectance), attenuation, splitter attenuation dead zone, event dead zone, noise level, peak to peak noise level, etc. 
       FIG.  18    illustrates a sensor display including section slopes with respect to the dual linear regression algorithm based creation of sub-sections, according to an example of the present disclosure. 
     Referring to  FIG.  18   , the S 2  section slope (L 2 ) at  1800  may be the last slope determined after the “splitter” event and before the signal falls into the noise. The time base control unit  108  may determine the slope using a regression analysis with a relatively large number of points (e.g., sub-section: Sb at  1802 ), and implement a linear function equation: y=a2·x+b2. 
     The time base control unit  108  may determine the S 1  Section slope (L 1 ) at  1804  as the first slope after the initial dead zone with a relatively large number of points, where no optical event has been identified in a given area. The time base control unit  108  may determine the slope using a regression analysis on this given section (e.g., Sub-section: Sa at  1806 ), and implement a linear function equation: y=a1·x+b1. 
     The time base control unit  108  may determine, if available, the intersection point Pi (Xi, Yi) between these two lines, and each point inside the section S may be determined as follows:
 
 Xi =( b 1− b 2)/( a 2− a 1), where  Xi  is the coordinate of the intersection point.
 
If  XSb′&lt;=x&lt;=XPi  then  y=a 2· x+b 2
 
If  xPi&lt;=x&lt;=XSa  then  y=a 1· x+b 1.
 
       FIG.  19    illustrates a sensor display including a section [S] generated using the dual linear regression algorithm based creation of sub-sections, according to an example of the present disclosure. 
     Referring to  FIG.  19   , the section [S] generated using the dual linear regression algorithm is shown at  1900 . 
       FIG.  20    illustrates a sensor display including a section [S] generated using a De Casteljau&#39;s algorithm based creation of sub-sections, according to an example of the present disclosure. 
     Referring to  FIG.  20   , as shown at  2000 , the time base control unit  108  may determine the section [S] generated using a variety of other algorithms, such as polynomial regression, B-splines, quadratic Bezier curves, the De Casteljau&#39;s algorithm as shown at  2000  in  FIG.  20   , etc. 
       FIG.  21    shows a computer system  2100  that may be used with the examples described herein. The computer system may represent a generic platform that includes components that may be in a server or another computer system. The computer system  2100  may be used as part of a platform for the time base control unit  108 . The computer system  2100  may execute, by a processor (e.g., a single or multiple processors) or other hardware processing circuit, the methods, functions and other processes described herein. These methods, functions and other processes may be embodied as machine readable instructions stored on a computer readable medium, which may be non-transitory, such as hardware storage devices (e.g., RAM (random access memory), ROM (read only memory), EPROM (erasable, programmable ROM), EEPROM (electrically erasable, programmable ROM), hard drives, and flash memory). 
     The computer system  2100  may include a processor  2102  that may implement or execute machine readable instructions performing some or all of the methods, functions and other processes described herein. Commands and data from the processor  2102  may be communicated over a communication bus  2104 . The computer system may also include a main memory  2106 , such as a random access memory (RAM), where the machine readable instructions and data for the processor  2102  may reside during runtime, and a secondary data storage  2108 , which may be non-volatile and stores machine readable instructions and data. The memory and data storage are examples of computer readable mediums. The memory  2106  may include the time base control unit  108  including machine readable instructions residing in the memory  2106  during runtime and executed by the processor  2102 . 
     The computer system  2100  may include an I/O device  2110 , such as a keyboard, a mouse, a display, etc. The computer system may include a network interface  2112  for connecting to a network. Other known electronic components may be added or substituted in the computer system. 
     The processor  2102  may be designated as a hardware processor. The processor  2102  may execute operations associated with various components of the OTDR device  100 . For example, the processor  2102  may execute operations associated with the time base control unit  108 , etc. 
     What has been described and illustrated herein is an example along with some of its variations. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Many variations are possible within the spirit and scope of the subject matter, which is intended to be defined by the following claims—and their equivalents—in which all terms are meant in their broadest reasonable sense unless otherwise indicated.