Return loss detection method and OTDR (Optical Time Domain Reflectometer) system

Abstract

The invention relates to the technical field of optical detection, in particular to a return loss detection method and an OTDR (Optical Time Domain Reflectometer) system, and the method comprises the following steps: carrying out driving current-output power calibration at a transmitting end of the OTDR system; performing received power-ADC value calibration at a receiving end of the OTDR system; configuring the current driving current of the OTDR system, and transmitting a signal to the to-be-tested system; collecting an ADC value reflected by the system to be tested through a receiving end of the OTDR system, and calculating an actual power value according to a received power-ADC calibration relation; the target power value is obtained according to the current driving current and the driving current-output power calibration relation, and the return loss value of the to-be-measured system is calculated according to the target power value and the actual power value. According to the scheme, the characteristics of the OTDR system are utilized, and through driving current-power calibration and receiving power-ADC calibration of the OTDR system, the return loss value of the to-be-measured system is calculated; the target power is transmitted to the to-be-detected system, the corresponding DAC value is collected, the actual power of the to-be-detected system is inversely calculated according to the calibration relation, the return loss value of the to-be-detected system can be directly calculated, the calculated amount is small, and the detection result is accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of optical detection, and particularly to a return loss detection method and an OTDR system. Background Art

[0002] The return loss of a traditional OTDR (Optical Time Domain Reflectometer) test system is mainly analyzed and processed based on the collected Rayleigh scattering trajectory. This scheme not only has a complex algorithm, but especially when affected by the OTDR blind zone, hardware noise, and high reflection at the front end of the test system, the measured return loss value often has a large error and is difficult to meet the requirements of high-precision application scenarios. Therefore, the return loss detection result of the system based on this scheme only plays an evaluation role and cannot obtain an accurate value.

[0003] Therefore, it is crucial for those skilled in the art to design a return loss detection method and an OTDR system with a small amount of calculation and a small detection error. Summary of the Invention

[0004] The technical problem to be solved by the embodiments of the present invention is to provide a return loss detection method and an OTDR system with a small amount of calculation and a small detection error, so as to solve the problems of complex algorithm and large error in measured value in the prior art.

[0005] The present invention discloses a return loss measurement method based on an OTDR system, and the solution is as follows:

[0006] Perform drive current-output power calibration at the transmitter end of the OTDR system;

[0007] Perform received power-ADC value calibration at the receiver end of the OTDR system;

[0008] Configure the current drive current of the OTDR system and transmit a signal to the system to be measured;

[0009] Collect the ADC value reflected back by the system to be measured through the receiver end of the OTDR system, and calculate the actual power value according to the received power-ADC calibration relationship;

[0010] Obtain the target power value according to the current drive current and the drive current-output power calibration relationship, and calculate the return loss value of the system to be measured according to the target power value and the actual power value.

[0011] Optionally, the drive current-output power calibration includes the following steps:

[0012] Configure multiple groups of drive currents with different DAC values at the transmitter end of the OTDR system, and correspondingly collect multiple groups of output powers at the output end of the OTDR system;

[0013] Establish a first-order linear relationship between drive current and output power based on multiple sets of drive current and output power data.

[0014] Optionally, the output power is collected by an external power collector.

[0015] Optionally, the first-order linear relationship formula between the drive current and the output power is:

[0016] Tx power (mW) = K0 * DAC_I + B0

[0017] Where Tx power is the output power, with the unit of mW, K0 is the slope, B0 is the intercept, and DAC_I is the DAC value corresponding to the drive current.

[0018] Optionally, the received power - ADC calibration includes the following steps:

[0019] Receive multiple sets of lights with different powers through the OTDR system and collect the ADC values corresponding to multiple sets of different received powers;

[0020] Establish a first-order linear relationship between the received power and the ADC value based on multiple sets of received power and ADC value data.

[0021] Optionally, the first-order linear relationship formula between the received power and the ADC value is:

[0022] Rx power (mW) = K1 * ADC_P + B1

[0023] Where Rx power is the received power, with the unit of mW, K1 is the slope, B1 is the intercept, and ADC_P is the ADC value collected at the receiving end of the OTDR system.

[0024] Optionally, it further includes the following steps:

[0025] Switch the drive current of the OTDR system to DC output.

[0026] Optionally, the calculation of the return loss value of the system under test includes the following steps:

[0027] Calculate the difference between the target power value and the actual power value as the return loss value of the system under test.

[0028] To solve the problems existing in the prior art, the present invention also provides an OTDR system, which includes: a main control unit, a laser control unit, a laser emitting unit, an optical circulator, an output unit, and a receiving unit. The output end of the laser control unit is connected to the laser emitting unit, the output end of the laser emitting unit is connected to the optical circulator, the output end of the optical circulator is connected to the output unit, the output end of the receiving unit is connected to the main control unit, and the output end of the main control unit is connected to the laser control unit.

[0029] Optionally, an optical detector is further provided between the optical circulator and the receiving unit.

[0030] Compared with the prior art, the beneficial effect of the return loss measurement method provided by the embodiment of the present invention is as follows: By designing a return loss measurement method based on an OTDR system, the method includes the following steps: performing drive current-output power calibration at the transmitting end of the OTDR system; performing received power-ADC value calibration at the receiving end of the OTDR system; configuring the current drive current of the OTDR system and transmitting a signal to the system under test; collecting the ADC value reflected back by the system under test through the receiving end of the OTDR system, and calculating the actual power value according to the received power-ADC calibration relationship; obtaining the target power value according to the current drive current and the drive current-output power calibration relationship, and calculating the return loss value of the system under test according to the target power value and the actual power value. This solution utilizes the inherent optical path characteristics of the OTDR system and its amplification ability for weak signals at the receiving end. By performing drive current-power calibration on the light emitted by the OTDR system in the DC mode and simultaneously performing received power-ADC calibration on its receiving end, when measuring the return loss of the system under test, by transmitting a known target power to the system under test and calculating the power reflected back by the system under test through the DAC value collected by the receiving end and the calibration relationship, the accurate return loss value of the system under test can be directly calculated, with not only small calculation amount but also small detection error. Description of the Drawings

[0031] The following will further elaborate on the solution of the present invention in conjunction with the drawings and embodiments. In the drawings:

[0032] Figure 1 is the flowchart of the return loss measurement method provided by the embodiment of the present invention;

[0033] Figure 2 is the module diagram of the OTDR system provided by the embodiment of the present invention.

[0034] The reference numerals in the drawings are as follows:

[0035] 100, main control unit; 200, laser control unit; 300, laser emitting unit; 400, optical circulator; 500, output unit; 600, receiving unit; 700, optical detector. Detailed implementation manners

[0036] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. Now, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

[0037] As Figure 1 and Figure 2 shown, the present invention provides a specific embodiment of a return loss measurement method.

[0038] A return loss measurement method, based on an OTDR system, with reference to Figure 1 , the return loss measurement method includes the following steps:

[0039] S1. Perform drive current-output power calibration at the transmitting end of the OTDR system;

[0040] S2. Perform received power-ADC value calibration at the receiving end of the OTDR system;

[0041] S3. Configure the current drive current of the OTDR system and transmit a signal to the system under test;

[0042] S4. Collect the ADC value reflected back by the system under test through the receiving end of the OTDR system, and calculate the actual power value according to the received power-ADC calibration relationship;

[0043] S5. Obtain the target power value according to the current drive current and the drive current-output power calibration relationship, and calculate the return loss value of the system under test according to the target power value and the actual power value.

[0044] Specifically, the above return loss measurement method is implemented based on an OTDR system, with reference to Figure 2 , the OTDR system includes a main control unit 100, a laser control unit 200, a laser emitting unit 300, an optical circulator 400, an output unit 500 and a receiving unit 600. The input end of the laser control unit 200 is connected to the output end of the main control unit 100, and the output end of the laser control unit 200 is connected to the input end of the laser emitting unit 300 for configuring the drive current of the laser emitting unit 300. The output end of the laser emitting unit 300 is connected to the input end of the optical circulator 400, and the output end of the optical circulator 400 is connected to the input end of the output unit 500 for unidirectionally transmitting the optical signal emitted by the laser emitting unit 300 to the output unit 500. The output unit 500 is used to output the optical signal emitted by the laser emitting unit 300 to the system under test.

[0045] Further, the receiving unit 600 is configured to receive the optical signal reflected back from the system under test to the OTDR system, and calculate the ADC value of the optical signal reflected back to the OTDR system. The output end of the receiving unit 600 is connected to the input end of the main control unit 100 for transmitting the collected data to the main control unit 100. An optical detector 700 is further provided between the optical circulator 400 and the receiving unit 600. The input end of the optical detector 700 is connected to the output end of the optical circulator 400, and the output end of the optical detector 700 is connected to the input end of the receiving unit 600 for converting the optical signal into an electrical signal.

[0046] Before measuring the return loss of the system under test, it is necessary to switch the drive current of the OTDR system to DC output, perform drive current-output power calibration at the transmitting end of the OTDR system, and perform received power-ADC value calibration at the receiving end of the OTDR system.

[0047] Specifically, the drive current-output power calibration is to establish a first-order linear relationship based on multiple sets of drive currents and the corresponding multiple sets of output powers under different drive currents. Taking the drive current as the independent variable and the output power that changes with the drive current as the target variable, perform linear regression to find the best regression coefficient and intercept, so as to establish a model that can best fit the drive current and output power data. In the OTDR system, the laser control unit 200 configures multiple sets of different drive currents for the laser transmitting unit 300, and records the output powers output by the output unit 500 under different drive currents, so as to obtain multiple sets of output powers. By using the output power of the output module as the standard, the internal loss of the OTDR system can be calibrated, making the data and the model more accurate.

[0048] Among them, the output power of the output module can be collected by an external power collector.

[0049] Further, the received power-ADC value calibration is to establish a first-order linear relationship between the received power and the ADC value data based on multiple sets of optical signals with different powers received by the OTDR system and the ADC values corresponding to multiple sets of different received powers collected by the OTDR system. Taking the received power as the independent variable and the corresponding ADC value as the target variable, perform linear regression to find the best regression coefficient and intercept between the two, so as to establish a model that can best fit the received power and ADC value data. In the OTDR system, different powers of light are transmitted to the OTDR system externally, and the ADC values corresponding to different powers are collected by the receiving unit 600 of the OTDR system, so as to obtain multiple sets of ADC values.

[0050] In one embodiment, the first-order linear relationship formula between the drive current and the output power is:

[0051] Tx power (mW) = K0 * DAC_I + B0

[0052] Wherein, Tx power is the output power, with the unit of mW, K0 is the slope, B0 is the intercept, and DAC_I is the DAC value corresponding to the drive current.

[0053] In one of the embodiments, the first-order linear relationship between the received power and the ADC value is:

[0054] Rx power (mW) = K1 * ADC_P + B1

[0055] Wherein, Rx power is the received power, with the unit of mW, K1 is the slope, B1 is the intercept, and ADC_P is the ADC value collected at the receiving end of the OTDR system.

[0056] It should be noted that, in the final calculation, the units of the output power and the received power need to be converted from mW to dBm, and the conversion formula is: That is, dBm is a logarithmic unit with 1 mW as the reference value.

[0057] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0058] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. For those skilled in the art, the technical solutions recorded in the above embodiments can be modified, or some of the technical features can be equivalently replaced; and all such modifications and replacements should fall within the protection scope of the appended claims of the present invention.

Claims

1. A return loss measurement method, based on an OTDR system, characterized in that Including the following steps: Perform drive current - output power calibration at the transmitting end of the OTDR system; Perform received power - ADC value calibration at the receiving end of the OTDR system; Configure the current drive current of the OTDR system and transmit a signal to the system under test; Collect the ADC value reflected back by the system under test through the receiving end of the OTDR system, and calculate the actual power value according to the received power - ADC calibration relationship; Obtain the target power value according to the current drive current and the drive current - output power calibration relationship, and calculate the return loss value of the system under test according to the target power value and the actual power value.

2. The return loss measurement method according to claim 1, wherein The drive current - output power calibration includes the following steps: Configure drive currents with multiple different DAC values at the transmitting end of the OTDR system, and correspondingly collect multiple sets of output powers at the output end of the OTDR system; Establish a first - order linear relationship between the drive current and the output power based on multiple sets of drive current and output power data.

3. The return loss measurement method according to claim 2, wherein The output power is collected by an external power collector.

4. The return loss measurement method according to claim 2, characterized in that, The first - order linear relationship formula between the drive current and the output power is: Tx power(mW)=K0*DAC_I + B0 Where, Tx power is the output power, its unit is mW, K0 is the slope, B0 is the intercept, and DAC_I is the DAC value corresponding to the drive current.

5. The return loss measurement method according to claim 1, wherein, The received power - ADC calibration includes the following steps: Receive lights with multiple different powers through the OTDR system, and collect the ADC values corresponding to multiple different received powers; Establish a first - order linear relationship between the received power and the ADC value based on multiple sets of received power and ADC value data.

6. The return loss measurement method according to claim 5, characterized in that, The first - order linear relationship formula between the received power and the ADC value is: Rx power(mW)=K1*ADC_P + B1 Where, Rx power is the received power, its unit is mW, K1 is the slope, B1 is the intercept, and ADC_P is the ADC value collected at the receiving end of the OTDR system.

7. The return loss measurement method according to claim 1, characterized in that, It also includes the following steps: Switch the drive current of the OTDR system to DC output.

8. The return loss measurement method according to claim 1, characterized in that, The calculation of the return loss value of the system under test includes the following steps: Calculate the difference between the target power value and the actual power value as the return loss value of the system under test.

9. An OTDR system, characterized in that, Including: A main control unit, a laser control unit, a laser transmitting unit, an optical circulator, an output unit, and a receiving unit. The output end of the laser control unit is connected to the laser transmitting unit, the output end of the laser transmitting unit is connected to the optical circulator, the output end of the optical circulator is connected to the output unit, the output end of the receiving unit is connected to the main control unit, and the output end of the main control unit is connected to the laser control unit.

10. The OTDR system according to claim 9, wherein An optical detector is also arranged between the optical circulator and the receiving unit.

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