Optical Time Domain Reflectometer

Abstract

To reduce degradation of an OTDR waveform even when reflected light with an optical intensity is received in an OTDR measurement.SOLUTION: An optical pulse tester 10 according to the present disclosure functions as an OTDR (Optical Time Domain Reflectometer) which can measure the state of an optical fiber 1. The optical pulse tester 10 includes: a laser element 121 for generating an optical pulse which enters an optical fiber 1; a light reception unit 123 for detecting reflected light from the optical fiber 1; an optical intensity adjusting unit 13 for adjusting the optical intensity of the optical pulse and the reflected light; and a control unit 16 for controlling the optical intensity adjusting unit 13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an optical time domain tester. [Background technology]

[0002] Conventionally, an optical time domain reflectometer (OTDR) has been known as a device capable of measuring the state of an optical fiber. For example, Patent Document 1 discloses an OTDR measuring device capable of detecting breaks and the like near the end of an optical fiber.

[0003] An OTDR repeatedly injects light pulses into the optical fiber being measured, and can measure the condition of the optical fiber, such as breaks and losses, based on the light intensity of the reflected light from the optical fiber and the time it takes to receive the reflected light from the optical fiber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-20226 Summary of the Invention [Problem to be solved by the invention]

[0005] If the optical fiber being measured has a break, the light reflected at the break will have a higher intensity than the light reflected by Rayleigh scattered light from the optical fiber. If the light intensity is higher than a predetermined level, an excessive photocurrent will be supplied to the amplifier downstream of the photodetector that detects the reflected light, and the amplifier output may become saturated.

[0006] When the amplifier output saturates, the response speed of the amplifier decreases, and the OTDR waveform measured by the OTDR deteriorates from the ideal waveform. In this specification, "OTDR waveform" means a waveform obtained by OTDR measurement, with the horizontal axis representing distance and the vertical axis representing light intensity. "Distance" corresponds to the time from when a light pulse is incident until the reflected light returns. "Light intensity" corresponds to the light intensity of the reflected light.

[0007] An example of an OTDR waveform measured with a conventional OTDR is shown in Fig. 5. Referring to Fig. 5, in the area where the light intensity of the reflected light is high, the actually measured OTDR waveform 501 is degraded from the ideal OTDR waveform 502 due to saturation of the amplifier output.

[0008] Therefore, an object of the present disclosure is to provide an optical time domain tester that can reduce degradation of the OTDR waveform even when receiving reflected light with high optical intensity during OTDR measurement. [Means for solving the problem]

[0009] According to some embodiments, an optical time domain reflectometer (OTDR) functions as an OTDR (Optical Time Domain Reflectometer) capable of measuring the state of an optical fiber, and includes a laser element that generates optical pulses to be incident on the optical fiber, a photodetector that detects reflected light from the optical fiber, a light intensity adjuster that adjusts the intensities of the optical pulses and the reflected light, and a controller that controls the light intensity adjuster. This optical time domain reflectometer can reduce degradation of the OTDR waveform even when receiving reflected light with high optical intensity during OTDR measurement.

[0010] In an optical pulse tester according to one embodiment, the light intensity adjuster may include a variable optical attenuator that adjusts the light intensity of the optical pulse and the reflected light. This allows the light intensity of the optical pulse and the reflected light to be adjusted.

[0011] In one embodiment of the optical time domain tester, when the OTDR waveform of the reflected light detected by the optical receiver includes an optical intensity equal to or greater than a threshold, the control unit may increase the attenuation of the variable optical attenuator by a predetermined amount and measure the reflected light again, thereby enabling measurement to be performed without saturating the amplifier output.

[0012] In one embodiment, the control unit may generate a composite OTDR waveform by combining multiple OTDR waveforms of the reflected light measured at multiple different attenuation amounts when the attenuation amount of the variable optical attenuator is increased by a predetermined amount. This allows a composite OTDR waveform to be generated by using OTDR waveform data measured at large attenuation amounts for portions with high light intensity and using OTDR waveform data measured at small attenuation amounts for portions with low light intensity.

[0013] In one embodiment, the optical time domain tester further includes a display unit, and the control unit may display the composite OTDR waveform on the display unit, thereby allowing a user to check the composite OTDR waveform.

[0014] In an optical pulse tester according to one embodiment, the light intensity adjuster may include a variable optical amplifier that can adjust the light intensity of the optical pulse and the reflected light, thereby adjusting the light intensity of the optical pulse and the reflected light.

[0015] In one embodiment of the optical time domain tester, when the OTDR waveform of the reflected light detected by the optical receiver contains an optical intensity equal to or greater than a threshold, the control unit may reduce the amplification amount of the tunable optical amplifier by a predetermined amount and measure the reflected light again, thereby enabling measurement to be performed without saturating the amplifier output.

[0016] In one embodiment, the control unit may generate a composite OTDR waveform by combining multiple OTDR waveforms of the reflected light measured with multiple different amplification amounts when the amplification amount of the variable optical amplifier is reduced by a predetermined amount. This allows a composite OTDR waveform to be generated by using OTDR waveform data measured with a small amplification amount for a portion with high light intensity and using OTDR waveform data measured with a large amplification amount for a portion with low light intensity.

[0017] In one embodiment, the optical time domain tester further includes a display unit, and the control unit may display the composite OTDR waveform on the display unit, thereby allowing a user to check the composite OTDR waveform. [Effects of the Invention]

[0018] According to the present disclosure, it is possible to provide an optical time domain tester that can reduce degradation of the OTDR waveform even when receiving reflected light with high optical intensity during OTDR measurement. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram illustrating a schematic configuration of an optical pulse tester according to an embodiment; [Figure 2A] FIG. 10 is a diagram showing an example of an OTDR waveform when the amount of attenuation is small. [Figure 2B] FIG. 10 is a diagram showing an example of an OTDR waveform when the amount of attenuation is large. [Figure 2C] FIG. 10 is a diagram showing an example of a composite OTDR waveform. [Figure 3] FIG. 10 is a diagram showing a schematic configuration of an optical pulse tester according to a modified example. [Figure 4] FIG. 1 is a diagram showing a schematic configuration of an optical pulse tester according to a comparative example. [Figure 5] FIG. 1 is a diagram showing an example of a conventional OTDR waveform. DETAILED DESCRIPTION OF THE INVENTION

[0020] 1 is a diagram showing a schematic configuration of an optical time domain tester 10 according to an embodiment of the present invention. The configuration and functions of the optical time domain tester 10 according to an embodiment of the present invention will be described with reference to FIG.

[0021] The optical time domain reflectometer 10 is a measuring instrument that functions as an OTDR capable of measuring the state of the optical fiber 1. The optical time domain reflectometer 10 can measure the state of the optical fiber 1, such as breakage and loss, of the optical fiber 1 that is the measurement target. The optical time domain reflectometer 10 can be used, for example, when laying the optical fiber 1 and when performing maintenance and inspection of the optical fiber 1.

[0022] The optical fiber 1 to be measured may be, for example, an optical fiber used in an optical communication system that performs data communication using optical signals.

[0023] The optical pulse tester 10 generates an OTDR waveform with distance on the horizontal axis and optical intensity on the vertical axis by injecting an optical pulse into the optical fiber 1 and measuring the optical intensity of the reflected light from the optical fiber 1. The "distance" on the horizontal axis corresponds to the time from when the optical pulse is injected until the reflected light returns. The "optical intensity" on the vertical axis corresponds to the optical intensity of the reflected light.

[0024] The light reflected at the break point of the optical fiber 1 has a higher optical intensity than the light reflected by Rayleigh scattering, etc. By generating an OTDR waveform using the optical time domain reflectometer 10, it is possible to determine at what distance the light intensity is high. This allows the optical time domain reflectometer 10 to measure the break point of the optical fiber 1.

[0025] The optical pulse tester 10 includes a laser driver 11, an optical module 12, a light intensity adjuster 13, an amplifier 14, a sampling unit 15, a control unit 16, and a display unit 17.

[0026] The laser driver 11 is a driver that drives the laser element 121 included in the optical module 12. The laser driver 11 drives the laser element 121 in response to a command from the controller 16, and can cause the laser element 121 to generate an optical pulse.

[0027] The optical module 12 includes a laser element 121, a half mirror 122, and a photodetector 123. The optical module 12 may house the laser element 121, the half mirror 122, and the photodetector 123 in the same case.

[0028] The laser element 121 generates laser light of a predetermined wavelength. It is sufficient for the laser element 121 to generate laser light of a constant light intensity. In other words, the laser element 121 does not need to have variable light intensity. The laser element 121 is driven by the laser driver 11 to generate light pulses that are incident on the optical fiber 1.

[0029] The half mirror 122 transmits the light pulse incident from the laser element 121 and supplies it to the light intensity adjusting unit 13. The half mirror 122 reflects the reflected light incident from the light intensity adjusting unit 13 and supplies it to the light receiver 123.

[0030] Here, the reflected light is light that is reflected by the optical fiber 1, which is the measurement target, after receiving an optical pulse from the optical pulse tester 10. The reflected light includes light reflected at a break in the optical fiber 1, light reflected by the optical fiber 1 due to Rayleigh scattering, and the like.

[0031] The photodetector 123 detects the reflected light incident on the half mirror 122 and supplies a current signal corresponding to the light intensity of the reflected light to the amplifier 14. The photodetector 123 may be, for example, an avalanche photodiode (APD).

[0032] The light intensity adjusting unit 13 can adjust the light intensity of the light pulse incident from the half mirror 122 of the optical module 12. The light intensity adjusting unit 13 can adjust the light intensity of the reflected light incident from the optical fiber 1.

[0033] The light intensity adjusting unit 13 includes a variable optical attenuator 131 and an attenuator driving unit 132 .

[0034] The variable optical attenuator 131 can adjust the optical intensity of the optical pulse incident from the half mirror 122 of the optical module 12. The variable optical attenuator 131 can adjust the optical intensity of the reflected light incident from the optical fiber 1. The attenuation amount of the variable optical attenuator 131 is set by the attenuator driver 132.

[0035] The attenuator driver 132 sets the amount of attenuation of the variable optical attenuator 131 in response to a command from the controller 16 .

[0036] The amplifier 14 converts the current signal supplied from the photodetector 123 of the optical module 12 into a voltage signal, and amplifies the converted voltage signal. The amplifier 14 outputs the voltage signal to the sampling unit 15.

[0037] The sampling unit 15 samples the voltage signal supplied from the amplifier 14 at predetermined time intervals and outputs the sampled signal to the control unit 16.

[0038] The control unit 16 includes at least one processor, at least one dedicated circuit, or a combination of these. The processor is a general-purpose processor such as a central processing unit (CPU) or a graphics processing unit (GPU), or a dedicated processor specialized for a specific process. The dedicated circuit is, for example, a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC). The control unit 16 controls each component of the optical time domain tester 10 and executes processes related to the operation of the optical time domain tester 10.

[0039] The control unit 16 controls the light intensity adjusting unit 13 to set the amount of attenuation of the variable optical attenuator 131. This allows the control unit 16 to adjust the light intensity of the light pulse incident from the half mirror 122 of the optical module 12. The control unit 16 can also adjust the light intensity of the reflected light incident from the optical fiber 1.

[0040] The operation of the control unit 16 will be described in detail later.

[0041] The display unit 17 includes one or more output interfaces for displaying information, and may include, for example, an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescent) display.

[0042] The display unit 17 can display the OTDR waveform generated by the control unit 16.

[0043] (Operation of the optical pulse tester) Next, the operation of the optical pulse tester 10 will be described.

[0044] The control unit 16 controls the laser driving unit 11 to cause the laser element 121 to generate an optical pulse. The optical pulse generated by the laser element 121 is input to the optical fiber 1 via the half mirror 122 and the variable optical attenuator 131.

[0045] At this time, the control unit 16 controls the attenuator driving unit 132 to set the attenuation amount of the variable optical attenuator 131 to a predetermined attenuation amount. As a result, the variable optical attenuator 131 attenuates the optical intensity of the optical pulse by the attenuation amount set by the control unit 16.

[0046] When an optical pulse is incident on optical fiber 1, light reflected at a break in optical fiber 1, light reflected by Rayleigh scattering in optical fiber 1, and the like return to optical pulse tester .

[0047] The reflected light incident on the optical fiber 1 and entering the optical pulse tester 10 is detected by the optical receiver 123 via the variable optical attenuator 131 and the half mirror 122. At this time, the variable optical attenuator 131 attenuates the optical intensity of the reflected light by the attenuation amount set by the control unit 16.

[0048] The photoreceiver 123 supplies a current signal corresponding to the light intensity of the reflected light to the amplifier 14. The amplifier 14 converts the current signal supplied from the photoreceiver 123 of the optical module 12 into a voltage signal and amplifies the converted voltage signal. The sampling unit 15 samples the voltage signal supplied from the amplifier 14 at predetermined time intervals. The sampling unit 15 outputs the sampled signal to the control unit 16.

[0049] The control unit 16 processes the voltage signal acquired from the sampling unit 15 to generate an OTDR waveform. As described above, the OTDR waveform is a waveform in which the horizontal axis represents "distance" and the vertical axis represents "light intensity." The "distance" on the horizontal axis corresponds to the time from when the light pulse is incident on the optical fiber 1 until the reflected light returns. The "light intensity" on the vertical axis corresponds to the light intensity of the reflected light.

[0050] If the OTDR waveform generated based on the reflected light detected by the photodetector 123 contains a light intensity equal to or greater than a threshold, the control unit 16 increases the attenuation of the variable optical attenuator 131 by a predetermined amount and measures the reflected light again.

[0051] The threshold value may be a value set based on the light intensity at which saturation of the voltage signal is expected to occur in the signal processing in the amplifier 14. In other words, if the OTDR waveform contains a light intensity equal to or greater than the threshold value, there is a possibility that saturation of the voltage signal will occur in the signal processing in the amplifier 14.

[0052] The predetermined amount may be a preset amount, for example, a few dB to 10 and a few dB.

[0053] The control unit 16 repeats the process of increasing the attenuation of the variable optical attenuator 131 by a predetermined amount and measuring the reflected light again until the generated OTDR waveform does not contain any optical intensity equal to or greater than the threshold.

[0054] When the control unit 16 increases the attenuation of the variable optical attenuator 131 by a predetermined amount and measures the reflected light again, it generates a composite OTDR waveform by combining the multiple OTDR waveforms generated based on the reflected light measured at each attenuation. In this embodiment, the term "composite OTDR waveform" is used to refer to a waveform generated by combining multiple OTDR waveforms.

[0055] The process of generating a composite OTDR will be described with reference to Figures 2A to 2C. Figure 2A is a diagram showing an example of an OTDR waveform when the attenuation of the variable optical attenuator 131 is small. Figure 2B is a diagram showing an example of an OTDR waveform when the attenuation of the variable optical attenuator 131 is large. Figure 2C is a diagram showing an example of a composite OTDR waveform obtained by combining the OTDR waveform shown in Figure 2A and the OTDR waveform shown in Figure 2B.

[0056] 2A, the tip of peak 201, where the optical intensity is high, is flattened, indicating that the signal input to amplifier 14 is large and the output of amplifier 14 is saturated.

[0057] When an OTDR waveform such as OTDR waveform A shown in Fig. 2A is generated, the control unit 16 increases the attenuation of the variable optical attenuator 131 by a predetermined amount and measures the reflected light again. The OTDR waveform generated based on the reflected light measured again in a state where the attenuation is large is OTDR waveform B shown in Fig. 2B.

[0058] 2B, the OTDR waveform B has a sharp peak at the tip of peak 203, which is the part of high light intensity. This indicates that the signal input to amplifier 14 has become smaller and the output of amplifier 14 is no longer saturated.

[0059] 2A and 2B, the width w1 of the peak 201 in the OTDR waveform A is wider than the width w2 of the peak 203 in the OTDR waveform B. This indicates that in the OTDR waveform A where the output of the amplifier 14 is saturated, the response speed of the amplifier 14 is reduced, and the width w1 of the peak 201 is wider.

[0060] In this way, by increasing the attenuation amount of the variable optical attenuator 131, the control unit 16 can generate an OTDR waveform B that has a sharp peak and a narrow peak 203 in the part where the light intensity is high, as shown in FIG. 2B.

[0061] 2A, where the light intensity of OTDR waveform A is low, and small signal portion 204, where the light intensity of OTDR waveform B is low, where small signal portion 202 is low, where small signal portion 204 is low, where small signal portion 202 is high in measurement, whereas the signal-to-noise ratio is low in small signal portion 204. Small signal portion 202 and small signal portion 204 are portions where there is no reflected light with high light intensity, such as the light reflected at a break point, and only reflected light due to Rayleigh scattering or the like is present.

[0062] That is, in areas where the light intensity is low, it is desirable to perform measurements with a small amount of attenuation, since this allows for a high signal-to-noise ratio to be achieved.

[0063] The control unit 16 combines the OTDR waveform A generated under the condition of small attenuation shown in Fig. 2A with the OTDR waveform B generated under the condition of large attenuation shown in Fig. 2B to generate the OTDR waveform C shown in Fig. 2C. The OTDR waveform C is a combined OTDR waveform.

[0064] As shown in FIG. 2C, OTDR waveform C is a waveform synthesized by using the waveform data of OTDR waveform B for the portion where the light intensity is high and the data of OTDR waveform A for the portion where the light intensity is low.

[0065] When the control unit 6 generates the composite OTDR waveform as shown in FIG. 2C, the control unit 6 causes the display unit 17 to display the composite OTDR waveform.

[0066] According to the optical pulse tester 10 of the embodiment described above, degradation of the OTDR waveform can be reduced even when high-intensity reflected light is received during OTDR measurement. More specifically, the optical pulse tester 10 includes a light intensity adjuster 13 that adjusts the intensities of the optical pulse and reflected light, and a controller 16 that controls the light intensity adjuster 13. When the OTDR waveform contains an optical intensity equal to or greater than a threshold, the controller 16 controls the light intensity adjuster 13 to attenuate the intensities of the optical pulse and reflected light. This prevents the output of the amplifier 14 from being saturated due to high intensities of the optical pulse and reflected light, thereby reducing degradation of the OTDR waveform even when high-intensity reflected light is received.

[0067] (Variation) 3 is a diagram showing a schematic configuration of an optical pulse tester 10a according to a modified example, which will be described with reference to FIG.

[0068] The optical pulse tester 10 a according to the modified example includes a laser driver 11 , an optical module 12 , a light intensity adjuster 18 , an amplifier 14 , a sampling unit 15 , a controller 16 , and a display unit 17 .

[0069] The optical pulse tester 10a according to the modified example differs from the optical pulse tester 10 shown in FIG. 1 in that the optical pulse tester 10a includes an optical intensity control unit 18 instead of the optical intensity control unit 13.

[0070] The optical pulse tester 10a according to the modified example will be mainly described with respect to the differences from the optical pulse tester 10 shown in FIG. 1, and the description of the commonalities and similarities with the optical pulse tester 10 shown in FIG. 1 will be omitted as appropriate.

[0071] The optical intensity adjuster 18 includes a variable optical amplifier 181 and an amplifier driver 182 .

[0072] The variable optical amplifier 181 can adjust the optical intensity of the optical pulse incident from the half mirror 122 of the optical module 12. The variable optical amplifier 181 can adjust the optical intensity of the reflected light incident from the optical fiber 1. The amplification amount of the variable optical amplifier 181 is set by the amplifier driver 182.

[0073] As described above, the variable optical attenuator 131 of the optical pulse tester 10 shown in FIG. 1 can adjust the optical intensity by setting the attenuation amount, whereas the variable optical amplifier 181 of the optical pulse tester 10a according to the comparative example can adjust the optical intensity by setting the amplification amount.

[0074] The variable optical amplifier 181 may be, for example, a semiconductor optical amplifier (SOA).

[0075] The amplifier driver 182 sets the amplification amount of the variable optical amplifier 181 in response to a command from the controller 16 .

[0076] If the OTDR waveform generated based on the reflected light detected by the photodetector 123 contains a light intensity equal to or greater than a threshold, the control unit 16 reduces the amplification amount of the variable optical amplifier 181 by a predetermined amount and measures the reflected light again.

[0077] The control unit 16 repeats the process of reducing the amplification amount of the variable optical amplifier 181 by a predetermined amount and measuring the reflected light again until the generated OTDR waveform does not contain any optical intensity equal to or greater than the threshold.

[0078] When the control unit 16 reduces the amplification amount of the variable optical amplifier 181 by a predetermined amount and measures the reflected light again, it generates a composite OTDR waveform by combining multiple OTDR waveforms generated based on the reflected light measured at each amplification amount.

[0079] When the control unit 16 generates the composite OTDR waveform, the control unit 16 causes the display unit 17 to display the composite OTDR waveform.

[0080] In this manner, in the optical pulse tester 10a according to the modification, when the OTDR waveform contains an optical intensity equal to or greater than the threshold, the control unit 16 reduces the amplification amount of the variable optical amplifier 181 by a predetermined amount. Therefore, like the optical pulse tester 10 shown in FIG. 1, the optical pulse tester 10a according to the modification can prevent the output of the amplifier 14 from becoming saturated, thereby reducing degradation of the OTDR waveform even when receiving reflected light with a high optical intensity.

[0081] Furthermore, the optical pulse tester 10a according to the modification includes a variable optical amplifier 181, which can amplify the optical pulses incident from the half mirror 122 of the optical module 12. This improves the dynamic range of the OTDR waveform. Furthermore, the laser element 121 does not need to be capable of generating high-power optical pulses, since the optical pulses generated by the laser element 121 can be low-power. Therefore, the optical pulse tester 10a according to the comparative example can broaden the options for the laser element 121.

[0082] (Comparative Example) 4 is a diagram showing a schematic configuration of an optical pulse tester 200 according to a comparative example. The optical pulse tester 200 according to the comparative example will be described with reference to FIG.

[0083] The optical pulse tester 200 according to the comparative example includes a laser driver 11, an optical module 12, an amplifier 14, a sampling unit 15, a control unit 16, and a display unit 17.

[0084] The optical pulse tester 200 according to the comparative example differs from the optical pulse tester 10 shown in FIG. 1 in that the optical pulse tester 200 does not include the optical intensity regulator 13.

[0085] Since the optical pulse tester 200 of the comparative example does not include the optical intensity adjuster 13, when the OTDR waveform generated based on the reflected light detected by the optical receiver 123 contains an optical intensity equal to or greater than a threshold, the gain of the amplifier 14 is set to a low value, and the optical intensity of the optical pulse generated by the laser element 121 is also set to a low value, and the OTDR waveform is measured again.

[0086] The optical time domain tester 200 according to the comparative example has the following four problems.

[0087] <Assignment 1> When the OTDR waveform contains optical intensity above the threshold, even if the amplification factor of amplifier 14 is set to a small value, if an excessively large current signal is supplied from optical receiver 123 to amplifier 14, the output of amplifier 14 will saturate, resulting in a decrease in response speed. When the output of amplifier 14 saturates, the resulting waveform will resemble OTDR waveform 501 shown in FIG. 5, degrading from ideal OTDR waveform 502. Therefore, in optical time domain tester 200 according to the comparative example, the waveform reproducibility and dead zone performance will also deteriorate.

[0088] <Assignment 2> When the OTDR waveform includes a light intensity equal to or greater than a threshold, if the light intensity of the light pulse generated by the laser element 121 is reduced, the central wavelength of the light pulse will be shifted.

[0089] <Assignment 3> The optical pulse tester 200 according to the comparative example adjusts the amplification factor of the amplifier 14 according to the intensity of the reflected light, which may result in a decrease in the signal-to-noise ratio.

[0090] <Assignment 4> When the OTDR waveform contains a light intensity equal to or greater than a threshold, the adjustment takes time because two parameters, the amplification degree of amplifier 14 and the light intensity of the light pulse generated by laser element 121, are adjusted.

[0091] The optical pulse tester 10 shown in FIG. 1 can solve the above-mentioned problems 1 to 4 of the optical pulse tester 200 according to the comparative example.

[0092] To address problem 1, when reflected light with high optical intensity is detected during OTDR measurement, the optical time domain tester 10 shown in Figure 1 can attenuate the optical intensity of the optical pulse and the reflected light by using the variable optical attenuator 131. This reduces the magnitude of the current signal supplied to the amplifier 14 and prevents the output of the amplifier 14 from saturating, thereby improving the waveform reproducibility of the optical time domain tester 10 shown in Figure 1.

[0093] To address problem 2, the optical pulse tester 10 shown in Figure 1 can maintain a constant optical intensity of the optical pulse generated by the laser element 121 without reducing the optical intensity of the optical pulse generated by the laser element 121, even when receiving reflected light with a high optical intensity during OTDR measurement. Therefore, the optical pulse tester 10 shown in Figure 1 can prevent the center wavelength of the optical pulse generated by the laser element 121 from shifting.

[0094] To address problem 3, the optical time domain tester 10 shown in FIG. 1 can set the gain of amplifier 14 to a constant level regardless of the intensity of the reflected light, thereby maintaining the signal-to-noise ratio at a desired level.

[0095] To address problem 4, the optical pulse tester 10 shown in FIG. 1 only needs to adjust the light intensity adjuster 13 when there is reflected light with a high optical intensity during OTDR measurement, thereby reducing the time required for adjustment.

[0096] It will be apparent to those skilled in the art that the present disclosure can be embodied in other specific forms other than the above-described embodiments without departing from the spirit or essential characteristics thereof. Therefore, the foregoing description is illustrative and not limiting. The scope of the disclosure is defined not by the foregoing description but by the appended claims. All modifications within the range of equivalents of any modifications are intended to be encompassed therein.

[0097] For example, the arrangement and number of each component described above are not limited to the above description and the illustrations in the drawings, and may be arbitrarily configured as long as the functions thereof can be realized.

[0098] For example, in the above-described embodiment, the optical module 12 is configured to include a laser element 121, a half mirror 122, and a photodetector 123, but the optical module 12 may further include a lens for converting the optical pulse into collimated light.

[0099] For example, in the description of the optical time domain tester 10a according to the above-described modification, when the OTDR waveform contains an optical intensity equal to or greater than the threshold, the control unit 16 reduces the amplification amount of the variable optical amplifier 181 by a predetermined amount and measures the reflected light again. However, the optical time domain tester 10a according to the modification may execute an operation of increasing the amplification amount by a predetermined amount instead of decreasing the amplification amount by a predetermined amount. In this case, the control unit 16 sets the amplification amount of the variable optical amplifier 181 to a small value as the initial value, and then increases the amplification amount by a predetermined amount until the OTDR waveform contains an optical intensity equal to or greater than the threshold, and measures the reflected light again. [Explanation of symbols]

[0100] 1. Optical fiber 10, 10a Optical Time Domain Reflectometer 11 Laser driver 12 Optical Modules 13 Light intensity adjustment unit 14 Amplifier 15 Sampling section 16 Control Unit 17 Display 18 Light intensity adjustment unit 121 Laser element 122 Half Mirror 123 Receiver 131 Variable Optical Attenuator 132 Attenuator driver 181 Tunable Optical Amplifier 182 Amplifier driver 200 Optical Time Domain Reflectometer

Claims

1. An optical time domain reflectometer (OTDR) capable of measuring the state of an optical fiber, a laser element that generates optical pulses that are incident on the optical fiber; a light receiver for detecting reflected light from the optical fiber; a light intensity adjusting unit that adjusts the light intensity of the light pulse and the reflected light; a control unit that controls the light intensity adjustment unit; Equipped with the light intensity adjusting unit includes a variable optical attenuator capable of adjusting the light intensity of the optical pulse and the reflected light, When the OTDR waveform of the reflected light detected by the optical receiver contains an optical intensity equal to or greater than a threshold, the control unit increases the attenuation of the variable optical attenuator by a predetermined amount and measures the reflected light again.

2. 2. The optical pulse tester according to claim 1, When the attenuation of the variable optical attenuator is increased by a predetermined amount, the control unit synthesizes multiple OTDR waveforms of the reflected light measured at multiple different attenuation amounts to generate a composite OTDR waveform.

3. 3. The optical pulse tester according to claim 2, Further comprising a display unit, The control unit causes the display unit to display the composite OTDR waveform.

4. An optical time domain reflectometer (OTDR) capable of measuring the state of an optical fiber, comprising: a laser element that generates optical pulses that are incident on the optical fiber; a light receiver for detecting reflected light from the optical fiber; a light intensity adjusting unit that adjusts the light intensity of the light pulse and the reflected light; a control unit that controls the light intensity adjustment unit; Equipped with The optical pulse tester, wherein the optical intensity adjusting unit includes a variable optical amplifier that can adjust the optical intensity of the optical pulse and the reflected light.

5. 5. The optical pulse tester according to claim 4, When the OTDR waveform of the reflected light detected by the optical receiver contains an optical intensity equal to or greater than a threshold, the control unit reduces the amplification amount of the variable optical amplifier by a predetermined amount and measures the reflected light again.

6. 6. The optical pulse tester according to claim 5, When the amplification amount of the variable optical amplifier is reduced by a predetermined amount, the control unit synthesizes multiple OTDR waveforms of the reflected light measured at multiple different amplification amounts to generate a composite OTDR waveform.

7. 7. The optical pulse tester according to claim 6, Further comprising a display unit, The control unit causes the display unit to display the composite OTDR waveform.

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