A method, system and OTDR device for avoiding event dead zones in optical time domain reflectometry

Abstract

The application discloses an optical time domain reflectometry (OTDR) method, system and OTDR equipment for avoiding event blind area, and relates to the technical field of OTDR. The OTDR method adds a second detector to the ground end of a first detector, and detects the optical signal emitted by a second light source by using the second detector. Then, when measuring the OTDR curve of a to-be-measured optical fiber, the second driver is controlled to drive the second light source to emit a compensation optical signal within a pre-determined saturation time interval, so that the photocurrent detected by the second detector offsets and compensates the photocurrent detected by the first detector, and the current input to the amplification circuit is lower than the saturation threshold, thereby eliminating the event blind area caused by saturation, enabling the blind area event to be detected, and without adding a selection switch, thereby avoiding introducing additional noise, improving the optical fiber OTDR test accuracy and having better noise performance.

Description

Technical Field

[0001] This application relates to the field of OTDR technology, and in particular to an optical time domain reflectance detection method, system and OTDR device that avoids event blind spots. Background Technology

[0002] Optical Time-Domain Reflectometer (OTDR) technology uses a driver to drive a light source to emit laser pulses into an optical fiber. A detector detects the backscattering and reflection signals of the laser pulses. The photocurrent detected by the detector is then amplified by an analog amplifier circuit and converted into a digital signal by an analog-to-digital converter (ADC), thus obtaining the OTDR measurement curve distributed along the optical fiber. Analysis of the acquired OTDR measurement curve can reveal several properties of the optical fiber link, such as uniformity, defects, breaks, and splice coupling. Therefore, it can be used to measure fiber attenuation, splice loss, locate fiber fault points, and understand the loss distribution along the fiber's length. It is an indispensable tool in optical cable construction, maintenance, and monitoring.

[0003] In practical applications, high dynamic range OTDRs can be used to measure longer optical fibers and have a wider range of applications. This is based on the OTDR dynamic range calculation formula. It can be seen that to obtain a larger dynamic range, such as 30dB, the signal-to-noise ratio... Need to be greater than Theoretically, a 20-bit ADC is needed in the hardware architecture to provide a 30dB dynamic range for OTDR. However, currently, the industry only offers low-sampling-rate 20-bit ADCs, which cannot meet the requirements of OTDR products. Therefore, due to limitations of commercially available ADC products, OTDR systems generally use 12-bit to 14-bit ADCs. However, this leads to saturation and recovery issues: when the laser pulse signal power is relatively high, the photocurrent detected by the detector is also relatively high. When passing through the analog amplifier circuit, this can easily cause saturation. Because the recovery time after saturation is relatively long, when the photocurrent detected by the detector decreases, the analog amplifier circuit cannot immediately return to the amplification state; it requires a long saturation recovery time to re-enter the amplification state. During the saturation state and saturation recovery time, it is impossible to accurately measure the OTDR curve, nor can other events that may occur on the fiber optic line (such as reflection events and attenuation events). This period is also known as the event blind zone, affecting the accuracy of the OTDR curve. For example, common issues include... Figure 1 The reflection event saturation condition shown and such Figure 2 The initial saturation condition is shown.

[0004] To address the event blind zone issue under high dynamic range requirements, some current practices employ multiple analog amplifier circuits in OTDR systems, switched using gain channel selection switches. A common approach involves using two analog amplifier circuits with different gains. When measuring the OTDR curve of an optical fiber, the system first switches to the low-gain amplifier circuit for the first measurement, amplifying the photocurrent detected by the detector to obtain a low-gain curve. Then, it switches to the high-gain amplifier circuit for the second measurement, amplifying the photocurrent to obtain a high-gain curve. Finally, the near-end portion of the low-gain curve replaces the near-end saturated portion of the high-gain curve, and the two curves are spliced ​​together to obtain the OTDR curve. However, because the photocurrent is relatively weak, the additional noise introduced by the gain channel selection switch affects the noise performance of the OTDR. Furthermore, even with a low-gain analog amplifier circuit, circuit saturation can still occur at very large reflection points, resulting in the event blind zone problem. Summary of the Invention

[0005] This application addresses the aforementioned problems and technical requirements by proposing an OTDR system that avoids event blind spots. The technical solution of this application is as follows: An optical temporal reflectance detection method that avoids event blind spots, the optical temporal reflectance detection method comprising: Drive the first light source to emit detection light signals When injected into the optical fiber under test, the first detector detects the optical signal returned by the optical fiber and generates a photocurrent. ; The second light source is driven to emit a compensation light signal within a predetermined saturation time interval. A second detector, connected in series with the first detector, detects the light signal emitted by the second light source and generates a photocurrent. Based on the photocurrent detected by the first detector After compensation, the output is lower than the saturation threshold of the amplifier circuit. Detection current And then input to the amplifier circuit and analog-to-digital converter in sequence. Indicates time; The OTDR curve of the optical fiber under test is obtained from the output curve of the analog-to-digital converter.

[0006] A further technical solution is that the optical temporal reflectance detection method also includes: Drive the first light source to emit test light signals The optical signal is injected into the fiber under test, and the test value curve of the analog-to-digital converter output is obtained to test the optical signal. The power is much smaller than the detection light signal. The power is sufficient to ensure the photocurrent detected by the first detector. ; According to the test light signal The obtained test numerical curves predict the saturation time range and the compensation optical signal .

[0007] Its further technical solution is to test the optical signal. The obtained test numerical curves predict the saturation time range and the compensation optical signal include: Determine the test optical signal The power relative to the detected optical signal Power scaling Depending on the number of bits of the analog-to-digital converter used Determine the upper limit of the output value of the analog-to-digital converter. ; According to the scale For the test optical signal The obtained test value curve is amplified, and the amplified test value curve is compared with the upper limit of the value. Numerical relationship to predict saturation time interval and compensate optical signal .

[0008] The further technical solution is to use the numerical curve of the amplified test value and the upper limit of the value. Numerical relationship to predict saturation time interval and compensate optical signal include: Determine if the measured numerical value curve exceeds the upper limit after numerical amplification. The time interval is used as the saturation time interval, and the saturation degree of the amplified test value curve within the saturation time interval is estimated. The compensation optical signal is then determined based on the saturation degree within the saturation time interval. The higher the saturation level, the better the compensation light signal. The higher the power.

[0009] A further technical solution involves estimating the degree of saturation of the amplified test numerical curve within the saturation time interval, including: Calculate the test value and upper limit of the numerical curve after numerical amplification within the saturation time interval. The difference values ​​are used to obtain the difference value curve within the saturation time interval. The larger the difference value, the higher the degree of saturation.

[0010] A further technical solution involves determining the compensation optical signal based on the degree of saturation within the saturation time interval. include: The difference curve within the saturation time interval is converted according to the analog-to-digital conversion logic of the analog-to-digital converter to obtain the photocurrent within the saturation time interval. and in accordance with The compensation optical signal within the saturation time interval is obtained through conversion. Time transformation curve ; Alternatively, the maximum value in the difference curve within the saturation time interval can be converted according to the analog-to-digital conversion logic of the analog-to-digital converter to obtain the photocurrent within the saturation time interval. maximum value and in accordance with The compensation optical signal within the saturation time interval is obtained through conversion. ; in, It is the conversion coefficient of the photocurrent obtained by converting the light signal sent by the second light source into a photocurrent by the second detector.

[0011] A further technical solution involves obtaining the OTDR curve of the optical fiber under test based on the output of the analog-to-digital converter, including: The OTDR curve of the optical fiber under test is obtained by superimposing the compensation curve within the saturation time interval onto the output curve of the analog-to-digital converter. The compensation curve within the saturation time interval is obtained by using the analog-to-digital conversion logic of the analog-to-digital converter to detect the compensation optical signal of the second detector within the saturation time interval. The obtained photocurrent The curve obtained after conversion.

[0012] A further technical solution involves driving a second light source to emit compensation light signals during a single OTDR curve detection of the optical fiber under test, within multiple saturation time intervals. The durations of any two saturation time intervals are equal or unequal; the compensation light signals emitted by the second light source within any two saturation time intervals. The signal power may be equal or unequal.

[0013] An optical time-domain reflectometry (OTDR) detection system that avoids event blind spots, the optical time-domain reflectometry (OTDR) detection system comprising: The first control module is used to drive the first light source to emit detection light signals. When injected into the optical fiber under test, the first detector detects the optical signal returned by the optical fiber and generates a photocurrent. ; The second control module is used to control the second driver to drive the second light source to emit compensation light signals within a predetermined saturation time interval. A second detector, connected in series with the first detector, detects the light signal emitted by the second light source and generates a photocurrent. Based on the photocurrent detected by the first detector After compensation, the output is lower than the saturation threshold of the amplifier circuit. Detection current And then input to the amplifier circuit and analog-to-digital converter in sequence. Indicates time; The curve output module is used to obtain the OTDR curve of the optical fiber under test based on the output curve of the analog-to-digital converter.

[0014] An OTDR device that avoids event blind spots includes a controller, a first driver, a first light source, a second driver, a second light source, a first detector, a second detector, an amplifier circuit, and an analog-to-digital converter. The controller is connected to and controls the first and second drivers. The first driver is connected to and drives the first light source, and the second driver is connected to and drives the second light source. The first and second detectors are connected in series. The common terminal of the first and second detectors is connected to the amplifier circuit and the analog-to-digital converter in sequence, and then connected to the controller. The first light source emits an optical signal to the optical fiber under test, and the first detector detects the optical signal returned by the optical fiber under test. The second detector detects the optical signal emitted by the second light source. The controller is used to perform the steps of the optical time-domain reflectometry method as described in the first aspect.

[0015] The beneficial technical effects of this application are: This application discloses an optical time domain reflectance detection method, system, and OTDR device that avoids event blind zones. The optical time domain reflectance detection method uses a second detector to detect the optical signal of a second light source for cancellation compensation, thereby avoiding event blind zones caused by saturation, enabling blind zone events to be detected, and without adding a selection switch to avoid introducing additional noise, thus improving the accuracy of fiber optic OTDR testing and having superior noise performance.

[0016] Existing methods for gain switching using multiple analog amplifier circuits with different gains require multiple curve tests. Each curve test necessitates transmitting multiple test pulses and performing numerous averaging operations. For example, with an analog amplifier circuit incorporating two gains, two curve tests are required, each involving transmitting, say, 10,000 pulses and performing 10,000 averaging operations. Averaging over 100km of fiber takes more than 1 millisecond, meaning one curve test takes 100 seconds. Therefore, two curve tests would take a total of 200 seconds, which is time-consuming and inefficient. While the optical time-domain reflectometry method of this application requires prior knowledge of the test numerical curve, this application only needs to transmit a single pulse of test light signal for averaging once to estimate the saturation time interval and the compensation light signal. Then, a curve test is performed using the compensation method. For example, using the same approach of transmitting 10,000 pulses for 10,000 averaging operations for one curve test, the method of this application can save approximately 100 seconds compared to traditional methods, thus significantly improving efficiency. Attached Figure Description

[0017] Figure 1 This is the output curve of the analog-to-digital converter when a reflection event occurs and the existing OTDR device becomes saturated.

[0018] Figure 2 This is the output curve of the analog-to-digital converter when the existing OTDR device experiences initial saturation.

[0019] Figure 3 This is a hardware structure diagram of an OTDR device according to an embodiment of this application.

[0020] Figure 4 This is a comparison chart of the output curve of the analog-to-digital converter under the conventional method and the output curve of the analog-to-digital converter after cancellation compensation according to the optical temporal reflectance detection method of this application.

[0021] Figure 5 This is a schematic diagram of the test value curve after the values ​​have been magnified in an example.

[0022] Figure 6 This is a structural block diagram of an optical temporal reflectance detection system according to an embodiment of this application. Detailed Implementation

[0023] The specific embodiments of this application will be further described below with reference to the accompanying drawings.

[0024] This application discloses an optical time-domain reflectometry (OTDR) method for avoiding event blind spots. The hardware structure diagram of the OTDR device implementing this method is shown below. Figure 3 As shown, the OTDR device includes a controller, a first driver 1, a first light source 2, a second driver 3, a second light source 4, a first detector 5, a second detector 6, an amplifier circuit, and an analog-to-digital converter. The actual controller is also connected to other devices such as a memory, which will not be described further in this application.

[0025] The controller connects to and controls the first driver 1 and the second driver 3. The first driver 1 connects to and drives the first light source 2, and the second driver 3 connects to and drives the second light source 4. The first detector 5 and the second detector 6 are connected in series. The cathode of the first detector 5 is connected to a positive power supply, and the anode of the second detector 6 is connected to a negative power supply or grounded; alternatively, the cathode of the first detector 5 is grounded, and the anode of the second detector 6 is connected to a negative power supply. The common terminal of the first detector 5 and the second detector 6 is connected to an amplifier circuit and an analog-to-digital converter in sequence before being connected to the controller. In one embodiment, both the first detector 5 and the second detector 6 are implemented using APDs (avalanche photodiodes). In this case, the cathode of the first detector 5 is connected to a positive power supply, and the anode of the first detector 5 is connected to the cathode of the second detector 6. The anode of the second detector 6 is grounded or connected to a negative power supply; alternatively, the cathode of the first detector 5 is grounded, and the anode of the second detector 6 is connected to a negative power supply.

[0026] The optical signal emitted by the first light source 2 (referred to as the test optical signal) is coupled to the optical fiber under test (the coupler can be a circulator, beam splitter, or beam splitter, etc.) through a coupler. For example, it is injected into port 1 of the circulator 7. Port 2 of the circulator 7 is connected to the optical fiber under test or injected into the beam splitter or beam splitter before being injected into the optical fiber under test. The optical signal undergoes backscattering and / or reflection in the optical fiber under test (which can be called backscattered and / or reflected optical signals). The backscattered and / or reflected optical signals are detected or received by the first detector 5 through the coupler. For example, it detects the optical signal at port 3 of the circulator 7 or detects the optical signal returning from the optical fiber and arriving at the first detector after passing through the beam splitter or beam splitter. If the coupler is a circulator, the circulator 7 sequentially transmits the optical signal input from port 1 to port 2 for injection into the optical fiber under test. The circulator 7 also sequentially transmits the backscattered optical signal from port 2 back into the optical fiber under test to port 3 for detection by the first detector 5. The second detector 6 detects the optical signal emitted by the second light source 4.

[0027] Based on having Figure 3 The OTDR device with the hardware circuit shown implements the optical time-domain reflectometry detection method disclosed in this application by executing the following steps: The first driver 1 controls the first light source 2 to emit detection light signals. The fiber under test is injected, and within a predetermined saturation time interval, the second driver 3 drives the second light source 4 to emit a compensation light signal. The predetermined saturation time interval is The time interval It is the saturation threshold of the amplifier circuit.

[0028] The detection light signal emitted by the first light source 2 The backward optical signal generated after being injected into the optical fiber under test is received by the first detector 5 and converted into photocurrent. Photocurrent The current flows from the pull-up power supply connected to the first detector 5 to the common terminal of the two detectors. When the second light source 4 does not emit a compensation light signal... At that time, the current flowing into the amplifier circuit is the photocurrent. Photocurrent After being amplified by an amplifier circuit, the signal is then converted into a digital signal by an analog-to-digital converter (ADC). At locations with large reflection points, due to... This can cause the amplifier circuit to saturate, resulting in an event blind zone that cannot detect attenuation events or reflection events.

[0029] Therefore, this application utilizes the second light source 4 to emit a compensation light signal within the saturation time interval that would lead to an event blind zone. Compensating for optical signals Received by the second detector 6 and converted into photocurrent Photocurrent The current flows from the common terminal of the two detectors to the ground terminal. At this time, the photocurrent detected by the second detector 6... The photocurrent detected by the first detector 5 To compensate for the loss, the detection current flowing into the amplifier circuit is reduced. Therefore, as long as the photocurrent is properly adjusted... The size makes the input amplifier circuit This can prevent amplifier circuit saturation, thereby avoiding the event blind zone within the saturation time interval.

[0030] The cancellation compensation effect of the second detector can avoid the occurrence of event blind spots. At this time, the current values ​​corresponding to the output curves of the analog-to-digital converter are all less than the saturation threshold. Furthermore, the output curve of the analog-to-digital converter does not exhibit an event blind zone within the saturation time interval. For example, in one instance, such as... Figure 4 As shown, the first light source 2 is arranged as follows Figure 4 (a) The detected light signal emitted in the middle. If the photocurrent is directly measured using conventional methods The curve of the amplified analog-to-digital converter output is as follows: Figure 4 As shown in (b) in the figure, by Figure 4 As can be seen from (b) in this case, the output curve of the analog-to-digital converter has a time dead zone. Based on this, and using the second light source 4 according to the method of this application, as shown in the diagram... Figure 4 (c) In this context, a compensation optical signal is emitted during the saturation time interval. In photocurrent The output curve of the analog-to-digital converter under the effect of compensation is as follows Figure 4 As shown in (d) in the diagram. Compare. Figure 4 As can be seen from (b) and (d) in this application, the output curve of the analog-to-digital converter after compensation avoids the event blind zone.

[0031] As mentioned above, the output curve of the analog-to-digital converter at this time is based on the photocurrent. The output curve under the compensation effect cannot accurately represent the OTDR data of the fiber under test. Therefore, data restoration is required, including superimposing the compensation curve within the saturation time interval onto the output curve of the analog-to-digital converter to obtain the OTDR curve of the fiber under test. The compensation curve within the saturation time interval used here is the same as the compensation optical signal detected by the second detector within the saturation time interval. The obtained photocurrent Correspondingly, and specifically according to the analog-to-digital conversion logic of the analog-to-digital converter, the photocurrent within the saturation time interval is... The curve obtained after transformation.

[0032] The core of the above process is to determine the compensation light signal emitted by the second light source 4. The start / stop timing and signal power are determined in advance by the controller using the first driver 1 in conjunction with the first light source 2, including: controlling the first driver 1 to drive the first light source 2 to emit test light signals. The test light signal emitted by the first light source 2 is injected into the optical fiber under test. The backward optical signal generated after being injected into the optical fiber under test is received by the first detector 5 and converted into photocurrent. Photocurrent The current flows from the pull-up power supply connected to the first detector 5 to the common terminal of the two detectors. (Photocurrent) After being amplified by the amplifier circuit, the signal is converted by the analog-to-digital converter (ADC) and the test value curve is output. The greater the power of the optical signal injected into the fiber under test, the greater the photocurrent detected by the first detector 5. Therefore, the test optical signal used during the test... The power is much smaller than the detection optical signal actually used. The power makes the photocurrent detected in this case... It is also relatively small, so as to ensure that the photocurrent detected by the first detector 5 is small. This will prevent circuit saturation issues.

[0033] Then based on the test light signal The obtained test numerical curves can be used to predict the saturation time range and compensate for the optical signal. This includes: first, determining the test optical signal. The power relative to the detected optical signal Power scaling Then, depending on the number of bits of the analog-to-digital converter used. Determine the upper limit of the output value of the analog-to-digital converter. For example, the number of bits in a 14-bit analog-to-digital converter. The upper limit of the output value of the analog-to-digital converter According to the scale For the test optical signal The obtained test value curve is amplified, and the amplified test value curve is compared with the upper limit of the value. The numerical relationship is used to predict the saturation time interval and compensate for the optical signal. Specifically: Determine if the measured numerical value curve exceeds the upper limit after numerical amplification. The time interval is used as the saturation time interval. For example, in one instance, the scale is... Then test the optical signal The obtained test value curve, when magnified by 100, exceeds the upper limit of the value. The time interval corresponding to the curve is the saturation time interval. The start and end times of the saturation time interval are the compensation light signals emitted by the second light source 4. The start and stop times. For example... Figure 5 A schematic diagram of the saturation time interval determined in one example is shown.

[0034] Additionally, the saturation level of the amplified test value curve within the saturation time interval is estimated, and then the compensation optical signal is determined based on the saturation level within the saturation time interval. The higher the saturation level obtained, the better the compensation optical signal. The higher the power.

[0035] In another embodiment, the numerical curve of the test value after numerical amplification exceeds the upper limit of the value. The degree of saturation is defined as the level of saturation, exceeding the upper limit of the value. The more values, the higher the degree of saturation. Therefore, the amplified test value curve is calculated, showing the test value and its upper limit within the saturation time interval. The difference values ​​are used to obtain the difference value curve within the saturation time interval. The larger the difference value, the higher the degree of saturation.

[0036] After obtaining the difference curve within the saturation time interval, one approach is to convert the difference curve within the saturation time interval according to the analog-to-digital conversion logic of the analog-to-digital converter to obtain the current-time curve, which is the time variation curve of the photocurrent within the saturation time interval. Then follow The compensation optical signal within the saturation time interval is obtained through conversion. Time variation curve The compensated optical signal obtained under the above circumstances The photocurrent within the saturation time interval is a dynamic curve that changes over time, leading to high control complexity. Therefore, to simplify control, another approach is to convert the maximum value of the difference curve within the saturation time interval according to the analog-to-digital converter's analog-to-digital conversion logic to obtain the photocurrent within the saturation time interval. maximum value and in accordance with The compensation optical signal within the saturation time interval is obtained through conversion. The compensated optical signal obtained in this case A pulse signal is formed by a constant value within the saturation time interval. Figure 4 Taking this as an example, this method can simplify control. Among other things, The conversion coefficient of the photocurrent is obtained by converting the light signal sent by the second light source into a photocurrent by the second detector, which can be obtained through calibration.

[0037] The compensation optical signal within the saturation time interval can be determined using the above method. There are actually one or more saturation time intervals. When there are multiple saturation time intervals, the controller controls the second driver to drive the second light source to emit compensation light signals in multiple saturation time intervals during one OTDR curve detection of the fiber under test. For example, in Figure 4 In the examples, please combine Figure 4 As can be seen from (c) in the example, two saturation time intervals were determined. Based on this, the durations of any two saturation time intervals are either equal or unequal. The compensation light signal emitted by the second light source within any two saturation time intervals... The signal power may be equal or unequal.

[0038] This application also discloses an optical temporal reflectance detection system that avoids event blind spots; please refer to [reference needed]. Figure 6 The optical time-domain reflectometry detection system includes: The first control module is used to drive the first light source to emit detection light signals. When injected into the optical fiber under test, the first detector detects the optical signal returned by the optical fiber and generates a photocurrent. .

[0039] The second control module is used to control the second driver to drive the second light source to emit compensation light signals within a predetermined saturation time interval. A second detector, connected in series with the first detector, detects the light signal emitted by the second light source and generates a photocurrent. Based on the photocurrent detected by the first detector After compensation, the output is lower than the saturation threshold of the amplifier circuit. Detection current And then input to the amplifier circuit and analog-to-digital converter in sequence. Indicates time.

[0040] The curve output module is used to obtain the OTDR curve of the optical fiber under test based on the output curve of the analog-to-digital converter.

[0041] Each module in the aforementioned optical temporal reflectance detection system can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the operations corresponding to each module. Furthermore, these modules are also used to perform the optical temporal reflectance detection steps in the various embodiments of this application, which will not be described in detail here. Those skilled in the art will understand that… Figure 6The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0042] The above descriptions are merely preferred embodiments of this application, and this application is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of this application should be considered to be included within the protection scope of this application.

Claims

1. A method for optical temporal reflectance detection that avoids event blind zones, characterized in that, The optical temporal reflectance detection method includes: Drive the first light source to emit detection light signals When injected into the optical fiber under test, the first detector detects the optical signal returned by the optical fiber and generates a photocurrent. ; The second light source is driven to emit a compensation light signal within a predetermined saturation time interval. A second detector, connected in series with the first detector, detects the light signal emitted by the second light source and generates a photocurrent. Based on the photocurrent detected by the first detector After compensation, the output is lower than the saturation threshold of the amplifier circuit. Detection current And then input to the amplifier circuit and analog-to-digital converter in sequence. Indicates time; The OTDR curve of the optical fiber under test is obtained from the output curve of the analog-to-digital converter. The optical time-domain reflectometry detection method further includes: driving a first light source to emit a test light signal. The optical signal is injected into the fiber under test, and the test value curve of the analog-to-digital converter output is obtained to test the optical signal. The power is much smaller than the detection light signal. The power is sufficient to ensure the photocurrent detected by the first detector. According to the test light signal The obtained test numerical curves predict the saturation time range and the compensation optical signal .

2. The optical temporal reflectance detection method according to claim 1, characterized in that, According to the test light signal The obtained test numerical curves predict the saturation time range and the compensation optical signal include: Determine the test optical signal The power relative to the detected optical signal Power scaling Depending on the number of bits of the analog-to-digital converter used Determine the upper limit of the output value of the analog-to-digital converter. ; According to the scale For the test optical signal The obtained test value curve is amplified, and the amplified test value curve is compared with the upper limit of the value. Numerical relationship to predict saturation time interval and compensate optical signal .

3. The optical temporal reflectance detection method according to claim 2, characterized in that, Based on the numerical curve and upper limit of the test values ​​after numerical amplification Numerical relationship to predict saturation time interval and compensate optical signal include: Determine if the measured numerical value curve exceeds the upper limit after numerical amplification. The time interval is used as the saturation time interval, and the saturation degree of the amplified test value curve within the saturation time interval is estimated. The compensation optical signal is then determined based on the saturation degree within the saturation time interval. The higher the saturation level, the better the compensation light signal. The higher the power.

4. The optical temporal reflectance detection method according to claim 3, characterized in that, The degree of saturation of the predicted numerical curve after amplification within the saturation time interval includes: Calculate the test value and upper limit of the numerical curve after numerical amplification within the saturation time interval. The difference values ​​are used to obtain the difference value curve within the saturation time interval. The larger the difference value, the higher the degree of saturation.

5. The optical temporal reflectance detection method according to claim 4, characterized in that, The compensation optical signal is determined based on the degree of saturation within the saturation time interval. include: The difference curve within the saturation time interval is converted according to the analog-to-digital conversion logic of the analog-to-digital converter to obtain the photocurrent within the saturation time interval. and in accordance with The compensation optical signal within the saturation time interval is obtained through conversion. Time transformation curve ; Alternatively, the maximum value in the difference curve within the saturation time interval can be converted according to the analog-to-digital conversion logic of the analog-to-digital converter to obtain the photocurrent within the saturation time interval. maximum value and in accordance with The compensation optical signal within the saturation time interval is obtained through conversion. ; in, It is the conversion coefficient of the photocurrent obtained by converting the light signal sent by the second light source into a photocurrent by the second detector.

6. The optical temporal reflectance detection method according to claim 1, characterized in that, The OTDR curve of the optical fiber under test obtained from the output of the analog-to-digital converter includes: The OTDR curve of the optical fiber under test is obtained by superimposing the compensation curve within the saturation time interval onto the output curve of the analog-to-digital converter. The compensation curve within the saturation time interval is obtained by using the analog-to-digital conversion logic of the analog-to-digital converter to detect the compensation optical signal of the second detector within the saturation time interval. The obtained photocurrent The curve obtained after conversion.

7. The optical temporal reflectance detection method according to claim 1, characterized in that, During an OTDR curve detection of the optical fiber under test, a second light source is driven to emit compensation light signals during multiple saturation time intervals. The durations of any two saturation time intervals are equal or unequal; the compensation light signals emitted by the second light source within any two saturation time intervals. The signal power may be equal or unequal.

8. An optical temporal reflectance detection system that avoids event blind spots, characterized in that, The optical time-domain reflectometry detection system includes: The first control module is used to drive the first light source to emit detection light signals. When injected into the optical fiber under test, the first detector detects the optical signal returned by the optical fiber and generates a photocurrent. ; The second control module is used to control the second driver to drive the second light source to emit compensation light signals within a predetermined saturation time interval. A second detector, connected in series with the first detector, detects the light signal emitted by the second light source and generates a photocurrent. Based on the photocurrent detected by the first detector After compensation, the output is lower than the saturation threshold of the amplifier circuit. Detection current And then input to the amplifier circuit and analog-to-digital converter in sequence. Indicates time; The curve output module is used to obtain the OTDR curve of the optical fiber under test based on the output curve of the analog-to-digital converter. The first control module is also used to drive the first light source to emit test light signals. The optical signal is injected into the fiber under test, and the test value curve of the analog-to-digital converter output is obtained to test the optical signal. The power is much smaller than the detection light signal. The power is sufficient to ensure the photocurrent detected by the first detector. According to the test light signal The obtained test numerical curves predict the saturation time range and the compensation optical signal .

9. An OTDR device that avoids event blind spots, characterized in that, The OTDR device includes a controller, a first driver, a first light source, a second driver, a second light source, a first detector, a second detector, an amplifier circuit, and an analog-to-digital converter. The controller is connected to and controls the first driver and the second driver. The first driver is connected to and drives the first light source, and the second driver is connected to and drives the second light source. The first detector and the second detector are connected in series. The common terminal of the first detector and the second detector is connected to the amplifier circuit and the analog-to-digital converter in sequence, and then connected to the controller. The first light source emits an optical signal to the optical fiber under test, and the first detector detects the optical signal returned by the optical fiber under test. The second detector detects the optical signal emitted by the second light source. The controller is used to perform the steps of the optical time-domain reflectometry detection method as described in any one of claims 1-7.

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