High-precision use method of low-resolution AD converter and optical time domain reflectometer

Abstract

This invention discloses a high-precision method for using a low-resolution analog-to-digital converter (ADC) and its optical time-domain reflectometer (OTDR). The method includes: introducing an analog output branch, which involves establishing an analog signal source, wherein the quantization step size of the analog signal source is smaller than the quantization step size of the ADC used for acquisition, and the full-scale amplitude of the output is larger than the quantization step size of the ADC used for acquisition; introducing an addition, which involves setting an adder to add the outputs of the analog output branch and the original detection path, and then outputting the sum to the ADC used for acquisition; performing detection, which includes: recording the quantization step size of the analog output branch as V; performing a single signal detection on the original detection path, and increasing the output of the analog output branch by V; and signal reconstruction, which involves, after multiple acquisitions, averaging all the acquired curves and then subtracting the known average bias voltage to obtain the true curve. This application achieves the measurement accuracy of a high-resolution ADC using a low-resolution ADC.

Description

Technical Field

[0001] This application relates to optical time domain reflectometers, and more particularly to a high-precision method for using a low-resolution AD converter and its optical time domain reflectometer. Background Technology

[0002] The resolution of an AD converter is defined as the full-scale voltage and The ratio of This refers to the number of bits in the AD converter. When the input analog signal is... and When the values ​​change between these two values, the conversion result is always the same. When an analog input is received and When the values ​​change between these two values, the conversion result is always the same. When the input analog quantity is and When the values ​​change between these two values, the conversion result is always the same. .

[0003] Based on the above, it is clear that this is using This is due to the unit used to quantize the input analog quantity, i.e. This indicates the quantization step size of the A / D converter. From the quantization results, it can be seen that when the analog quantity changes within... In between, it becomes impossible to distinguish them in greater detail, which creates a blind spot in resolution conversion. To be able to distinguish between... For small analog signals, the number of bits in the AD converter must be increased.

[0004] It's important to note that resolution, simply put, refers to the number of decimal places. For example, 4.201V has a higher resolution than 4.20V, but higher resolution does not necessarily mean higher precision.

[0005] OTDR stands for Optical Time Domain Reflectometer. It's a precision optoelectronic instrument developed using the Rayleigh scattering phenomenon that occurs when a laser beam propagates through an optical fiber. Its working principle involves injecting a high-power laser pulse into the fiber under test and then collecting the scattered light power returning along the fiber axis at the same port. The loss experienced by the optical pulse during propagation in the fiber is directly reflected in the collected optical power value at that moment. Plotting the data over time yields the attenuation curve of the fiber.

[0006] Because Rayleigh scattering in optical fibers is extremely weak, an OTDR receiver generates only about 1 nA of photocurrent when measuring the end of a 100-kilometer fiber. This photocurrent typically requires amplification by a TIA circuit before data acquisition using a high-speed AD converter.

[0007] The dynamic range of a measurable signal is primarily determined by the resolution of the analog-to-digital converter (ADC). Since ADCs cannot distinguish signals smaller than their quantization step size, high-precision, high-speed ADCs, i.e., high-bit ADCs, are generally selected during the selection process.

[0008] However, the unit price of 12-bit, 14-bit and above D converter chips is generally high, and they are basically all imported. Especially for high-speed AD converters with 14 bits or more, domestically produced chips are even scarcer, which leads to increased costs of related equipment and restricts the development of related industries in China. Therefore, this application proposes a new technical solution. Summary of the Invention

[0009] In order to achieve the measurement accuracy of a high-resolution AD converter with a low-resolution AD converter, this application provides a high-precision method for using a low-resolution AD converter and its optical time domain reflectometer.

[0010] Firstly, this application provides a high-precision method for using a low-resolution AD converter, employing the following technical solution:

[0011] A high-precision method for using a low-resolution AD converter includes the following steps:

[0012] S101, Analog output branch introduction, which includes establishing an analog signal source, wherein the quantization step size of the analog signal source is smaller than the quantization step size of the AD converter used for acquisition, and the full-scale amplitude of the output is larger than the quantization step size of the AD converter used for acquisition.

[0013] S102, addition introduction, which includes setting up an adder, adding the output of the analog output branch and the original detection branch through the adder, and then outputting it to the AD converter for acquisition;

[0014] S103, Detection execution, which includes:

[0015] S201, Let the quantization step size of the analog output branch be... V;

[0016] S202, the original detection path performs primary signal detection, and the output of the analog output branch is increased. V;

[0017] S104, Signal Restoration, which involves accumulating all the acquired curves, averaging them, and then subtracting the known average bias voltage value to obtain the true curve.

[0018] Optionally, the analog output branch includes: a DA converter and a first operational amplifier connected to the output of the DA converter. The first operational amplifier is configured to attenuate the output voltage of the DA, so that the quantization step size of the analog output branch is smaller than the quantization step size of the AD converter used for acquisition, and the full-scale amplitude of the output is larger than the quantization step size of the AD converter used for acquisition.

[0019] Optionally, the DA converter is a low-speed, low-precision DA converter.

[0020] Optionally, the adder includes a second operational amplifier.

[0021] Secondly, this application provides an optical time-domain reflectometer, which adopts the following technical solution:

[0022] An optical time-domain reflectometer, wherein one AD acquisition channel of the optical time-domain reflectometer includes:

[0023] Avalanche photodiode (APD) is used to convert optical signals into electrical signals.

[0024] The TIA operational amplifier has its input connected to the avalanche photodiode (APD).

[0025] The analog output branch has a quantization step size smaller than that of the AD converter used for data acquisition, and its full-scale output amplitude is larger than that of the AD converter used for data acquisition.

[0026] The adder has its input connected to the analog output branch and the output of the TIA operational amplifier, and its output connected to the AD converter used for acquisition in the optical time domain reflectometer.

[0027] Optionally, the analog output branch includes: a DA converter and a first operational amplifier connected to the output of the DA converter, wherein the DA converter is configured to connect to the main control board of the optical time domain reflectometer; and the first operational amplifier is configured to attenuate the output voltage of the DA converter.

[0028] Optionally, the main control board of the optical time domain reflectometer is configured as follows:

[0029] Used to match an increase of ΔV with each optical pulse transmission; and used to control the increase of the output voltage of the DA converter by ΔV, which is synchronized with or precedes the transmission of the optical pulse.

[0030] Optionally, the main control board of the optical time domain reflectometer is also configured as follows:

[0031] Used to establish a database that corresponds one-to-one with optical fiber measurement distance / time and optical pulse transmission count;

[0032] This is used to obtain the selected data for fiber optic measurement distance / time, search the database to retrieve the corresponding number of optical pulse transmissions, and execute the optical pulse transmission action during the current measurement process based on the search results.

[0033] Optionally, the main control board of the optical time domain reflectometer is also configured as follows:

[0034] Used to obtain user authentication data and identify and match user identities in the identity information database;

[0035] Used to record each usage session and bind user identity; and,

[0036] It is used to retrieve the user's previous usage record based on the user's identity, determine the number of optical pulses sent in the previous use, and operate on the number of optical pulses sent in the previous use when no new optical fiber measurement distance / time selection data is received.

[0037] Optionally, the quantization step size of the analog output branch is configured to be adjustable and controlled by the main control board of the optical time domain reflectometer.

[0038] In summary, this application includes at least one of the following beneficial technical effects: it is equivalent to further subdividing the quantization step size of the AD converter, which solves the problem that the slight changes in the original curve are insufficient to cause changes in the output value of the AD converter, resulting in the loss of true curve information. This allows the low-bit AD converter to achieve the acquisition effect of using a higher bit-level AD converter. For example, OTDR products that originally used 12-bit or 14-bit AD converters can be replaced by 8-bit or 10-bit AD converters, reducing costs and mitigating the impact of foreign chip restrictions. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the system block of this application;

[0040] Figure 2 This is a schematic diagram of the waveforms collected in this application;

[0041] Figure 3 This is a circuit diagram of an operational amplifier attenuator according to an embodiment of this application. Detailed Implementation

[0042] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0043] This application discloses a high-precision method for using a low-resolution AD converter.

[0044] Reference Figure 1 High-precision usage methods for low-resolution AD converters include:

[0045] S101, Analog output branch introduction, which includes establishing an analog signal source, wherein the quantization step size of the analog signal source is smaller than the quantization step size of the AD converter used for acquisition, and the full-scale amplitude of the output is larger than the quantization step size of the AD converter used for acquisition.

[0046] In one embodiment, the analog output branch includes a DA converter and a first operational amplifier; wherein the input of the DA converter is connected to a digital signal generation unit for control, such as a CPU, the output of the DA converter is connected to the input of the first operational amplifier (AMP), and the output of the first operational amplifier serves as an analog signal output.

[0047] It is understandable that the analog output branch mentioned above can also be any other circuit structure that can generate analog quantities that meet the above requirements; in this embodiment, the DA converter + first operational amplifier is preferred for one reason: the output adjustment and control of the DA converter is convenient and can better cooperate with the other contents below.

[0048] The function of the first op-amp in the circuit is to attenuate the output voltage (amplitude) of the DA converter. Specifically, the first op-amp forms an attenuator to reduce the output of the DA converter, ensuring it meets the signal requirements for the analog output branch.

[0049] 1. The attenuated value of the quantization step size of the DA converter is less than the quantization step size of the AD converter;

[0050] 2. The attenuated value of the full-scale output amplitude of the DA converter is greater than the quantization step size of the AD converter.

[0051] It is understood that the operational amplifier attenuator is existing technology, and the other embodiment described below, along with other limited examples, will not be repeated here.

[0052] In one embodiment, the aforementioned DA converter is preferably a low-speed, low-precision DA converter, which reduces costs while better meeting usage requirements.

[0053] S102, addition introduction, which includes setting up an adder, adding the output of the analog output branch and the original detection branch through the adder, and then outputting to the AD converter for acquisition.

[0054] In one embodiment, the adder includes a second operational amplifier, that is, the second operational amplifier is used to form an adder to connect the output value of one path of the DA converter to the acquisition circuit (the DA converter for acquisition).

[0055] S103, Detection execution, which includes:

[0056] S201, Let the quantization step size of the analog output branch be... V;

[0057] S202, the original detection path performs primary signal detection, and the output of the analog output branch is increased. V.

[0058] Using OTDR in conjunction with other devices, simply put, means: Figure 1 As shown,

[0059] Original: The APD is responsible for converting the optical signal into a current signal, and the TIA op-amp is responsible for converting the current signal into a voltage signal and amplifying it, and then inputting it into the AD converter for acquisition;

[0060] In this application, another signal source (a DA converter and an operational amplifier) ​​is introduced into the analog circuit. The output value of the DA converter is connected to the acquisition circuit through an adder. The quantization step size of the DA converter is recorded as ΔV. For each optical pulse sent by the OTDR system, the output voltage of the DA converter is increased by ΔV.

[0061] S104, Signal Restoration, which involves accumulating all the acquired curves, averaging them, and then subtracting the known average bias voltage value to obtain the true curve.

[0062] like Figure 2 The diagram shown is a schematic of the data collection process.

[0063] A1: The curve obtained from the first data collection is... ;

[0064] A2: The curve obtained from the second data collection is... ;

[0065] A3: The curve obtained from the third data collection is... ;

[0066] An: The The curve obtained from the second data collection is: .

[0067] Based on the above, the quantization step size of the AD converter has been further subdivided, which solves the problem that the slight changes in the original curve were not enough to cause changes in the output value of the AD converter, resulting in the loss of true curve information. This allows the low-bit AD converter to achieve the acquisition effect of using a higher bit-count AD converter.

[0068] In one embodiment, the logic for sending the optical pulse and increasing ΔV is limited to: at least synchronous, meaning the optical pulse is executed slightly earlier. This is because, considering time delays, the ADC has already started acquiring data when the optical pulse is sent. For a more accurate curve, the acquired signal needs to be complete from beginning to end; therefore, the DA output needs to be increased before acquisition.

[0069] This application also discloses an optical time domain reflectometer.

[0070] An optical time domain reflectometer (OTDR) has one AD acquisition channel including:

[0071] Avalanche photodiode (APD) is used to convert optical signals into electrical signals.

[0072] The TIA operational amplifier has its input connected to the avalanche photodiode (APD).

[0073] The analog output branch has a quantization step size smaller than that of the AD converter used for data acquisition, and its full-scale output amplitude is larger than that of the AD converter used for data acquisition.

[0074] The adder has its input connected to the analog output branch and the output of the TIA operational amplifier, and its output connected to the AD converter used for acquisition in the optical time domain reflectometer.

[0075] As is understandable, the analog output branch and adder are as described in the previous method, and will not be repeated here.

[0076] Based on the above: the DA converter is configured to connect to the main control board of the optical time domain reflectometer. The main control board of the optical time domain reflectometer is configured to match an increase of ΔV with each optical pulse transmission; and to control the output voltage of the DA converter to increase by ΔV, synchronously or ahead of the transmission of the optical pulse.

[0077] Based on the above settings, OTDR products that originally used 12-bit or 14-bit AD converters can be replaced by 8-bit or 10-bit AD converters, thereby reducing equipment costs and being less restricted by chips.

[0078] In one embodiment, the present application also makes the following settings:

[0079] The main control board of the optical time domain reflectometer is also configured to: establish a database for a one-to-one correspondence between fiber optic measurement distance / time and the number of optical pulse transmissions; and,

[0080] This is used to obtain the selected data for fiber optic measurement distance / time, search the database to retrieve the corresponding number of optical pulse transmissions, and execute the optical pulse transmission action during the current measurement process based on the search results.

[0081] Based on the above, users can manually select different sampling times on the OTDR's interactive interface, depending on their specific needs. Compared to a fixed format, this reduces the likelihood of signal loss and helps establish a more realistic signal curve.

[0082] In one embodiment, the application further configures the main control board of the optical time domain reflectometer as follows:

[0083] Used to obtain user authentication data and identify and match user identities in the identity information database;

[0084] Used to record each usage session and bind user identity; and,

[0085] It is used to retrieve the user's previous usage record based on the user's identity, determine the number of optical pulses sent in the previous use, and operate on the number of optical pulses sent in the previous use when no new optical fiber measurement distance / time selection data is received.

[0086] It is understandable that the aforementioned identity verification data can be any type of data, such as fingerprints, voiceprints, or facial recognition. Based on these settings, the use of OTDR devices becomes relatively more convenient, especially when the same person repeatedly performs the same tasks, reducing unnecessary operations.

[0087] In another embodiment, the present application further sets the following: the quantization step size of the analog output branch is configured to be adjustable and controlled by the main control board of the optical time domain reflectometer.

[0088] Based on the foregoing, adjustable quantization step size can be achieved by using multiple DA converters connected in parallel, selected according to requirements; or by using an operational amplifier attenuator with adjustable attenuation, as described above. Figure 3 For example:

[0089] The inverting input of the op-amp is connected to resistors R1 and R2 connected in series, with R1 connected to the input. The non-inverting input of the op-amp is connected to resistor R3, and the connection point is grounded. The other end of resistor R3 is connected to the connection point of resistors R1 and R2. The connection point of resistor R2 and the op-amp is connected to resistor R4, and the other end of resistor R4 is connected to the output of the op-amp. It is understood that to achieve adjustable attenuation, the fixed resistors can be replaced with adjustable resistors. The specific replacement depends on the usage requirements, and an operation port for the adjustable resistor is reserved on the OTDR.

[0090] In another embodiment, the main control board of the optical time domain reflectometer can also be configured to: adjust and control the quantization step size of the analog output branch.

[0091] Based on the above, for example: at least one adjustable resistor can be replaced by multiple transistor switching circuits, wherein the base of the transistor is connected to the main control board for control, and the emitter is connected in series to replace other resistors of the original adjustable resistor; the other resistors of the multiple transistor switching circuits have different resistance values.

[0092] In use, by controlling the conduction state of the transistor switching circuit, different other resistors can be selected to achieve quantization step size adjustment control of the analog output branch.

[0093] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An optical time-domain reflectometer, characterized in that: The AD acquisition channel of the optical time domain reflectometer includes: Avalanche photodiode (APD) is used to convert optical signals into electrical signals. The TIA operational amplifier has its input connected to the avalanche photodiode (APD). The analog output branch has a quantization step size smaller than that of the AD converter used for data acquisition, and its full-scale output amplitude is larger than that of the AD converter used for data acquisition. The adder has its input connected to the analog output branch and the output of the TIA operational amplifier, and its output connected to the AD converter used for acquisition in the optical time domain reflectometer. The analog output branch includes a DA converter and a first operational amplifier connected to the output of the DA converter. The DA converter is configured to connect to the main control board of the optical time domain reflectometer. The first operational amplifier is configured to attenuate the output voltage of the DA converter. The main control board is configured to perform detection execution, which includes: Let ΔV be the quantization step size of the analog output branch; The original detection path detects a primary signal, and the output of the analog output branch increases by ΔV. Signal restoration involves multiple acquisitions, averaging all acquired curves, and then subtracting the known average bias voltage value to obtain the true curve. The DA converter is a low-speed, low-precision DA converter. The adder includes a second operational amplifier; The main control board of the optical time domain reflectometer is configured as follows: Used to match an increase of ΔV with each optical pulse transmission; and used to control the increase of the output voltage of the DA converter by ΔV, which is synchronized with or ahead of the transmission of the optical pulse.

2. The optical time-domain reflectometer according to claim 1, characterized in that: The main control board of the optical time domain reflectometer is also configured as follows: Used to establish a database that corresponds one-to-one with optical fiber measurement distance / time and optical pulse transmission count; This is used to obtain the selected data for fiber optic measurement distance / time, search the database to retrieve the corresponding number of optical pulse transmissions, and execute the optical pulse transmission action during the current measurement process based on the search results.

3. The optical time-domain reflectometer according to claim 2, characterized in that: The main control board of the optical time domain reflectometer is also configured as follows: Used to obtain user authentication data and identify and match user identities in the identity information database; Used to record each usage session and bind user identity; and, It is used to retrieve the user's previous usage record based on the user's identity, determine the number of optical pulses sent in the previous use, and operate on the number of optical pulses sent in the previous use when no new optical fiber measurement distance / time selection data is received.

4. The optical time-domain reflectometer according to claim 1, characterized in that: The quantization step size of the analog output branch is configured to be adjustable and controlled by the main control board of the optical time domain reflectometer.

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