CN114421964A - High-precision using method of low-resolution AD converter and optical time domain reflectometer thereof - Google Patents

Abstract

The invention discloses a high-precision using method of a low-resolution AD converter and an optical time domain reflectometer thereof, wherein the method comprises the following steps: the analog output branch is introduced, which comprises establishing an analog signal source, wherein the quantization step length of the analog signal source is smaller than that of the acquisition AD converter, and the full-scale amplitude of the output is larger than that of the acquisition AD converter; the addition introduction comprises an adder, wherein the adder adds the outputs of the analog output branch and the original detection branch and outputs the added outputs to an AD converter for acquisition; detection execution, comprising: the quantization step length of the analog output branch is recorded as

V; the primary signal detection of the original detection path and the output increase of the analog output branch

V; and (3) signal restoration, which comprises the steps of accumulating all the acquisition curves, taking the average value, and then subtracting the known average value of the bias voltage to obtain a real curve after multiple acquisition. The present application has the effect of achieving the measurement accuracy of a high-order AD converter with a low-resolution AD converter.

Description

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

Technical Field

The present invention relates to an optical time domain reflectometer, and more particularly, to a high-precision using method of a low-resolution AD converter and an optical time domain reflectometer thereof.

Background

The resolution of the AD converter is defined as the full-scale voltage and

the ratio of the first to the second,

the number of bits of the AD converter. When the analog quantity is input

And

when changing, the conversion results are all

(ii) a When inputting analog quantity

And

when changing, the conversion results are all

(ii) a When the analog quantity is input

And

when changing, the conversion results are all

。

From the above, it can be seen that this is done

By making units to quantize the input analog quantity, i.e.

The quantization step size of the AD converter is indicated. From the quantization results, when the analog quantity changes in the quantity

In between, it is no longer possible to perform finer resolution, which causes a dead zone in the conversion resolution. To distinguish the ratio

The number of bits of the AD converter must be increased for a small analog quantity.

It should be noted that the resolution is simply the number of bits after the decimal point, for example, the resolution of 4.201V is higher than 4.20V, but the high resolution does not represent high precision.

The OTDR is called Optical Time Domain Reflectometer in English, and Chinese means an Optical Time Domain Reflectometer. The OTDR is a precision optoelectronic integration instrument developed by utilizing the rayleigh scattering phenomenon generated when laser light is transmitted through an optical fiber. The working principle of the device is that high-power light pulse laser is injected into an optical fiber to be detected, and then scattered light power of the light pulse returning back along the axial direction of the optical fiber is collected at the same port. The loss of the optical pulse transmitted in the optical fiber directly reflects the optical power value acquired at the moment, and the attenuation curve of the optical fiber can be obtained by plotting the data along with the time sequence.

Since rayleigh scattering in the fiber is very weak, the OTDR receive end only generates about 1nA photocurrent for the end of the fiber measuring 100 km. For this photocurrent, TIA circuitry is typically required for amplification, followed by data acquisition using a high-speed AD converter.

The dynamic range of the measurable signal is mainly determined by the resolution of the AD converter. Since the AD converter cannot distinguish a signal smaller than its quantization step, a high-speed AD converter with high accuracy, i.e., a high-order AD converter is generally selected in the model selection.

However, the unit price of the D converter chips of 12 bits, 14 bits and above is generally expensive, and basically depends on import, especially for the high-speed AD converter of 14 bits or above, the chips made in China are more rare, which leads to the increase of the cost of the related equipment, and the development of the related industry in China is limited, so the present application proposes a new technical solution.

Disclosure of Invention

In order to realize the measurement accuracy of a high-order AD converter by a low-resolution AD converter, the application provides a high-accuracy using method of the low-resolution AD converter and an optical time domain reflectometer thereof.

In a first aspect, the present application provides a high-precision using method of a low-resolution AD converter, which adopts the following technical solutions:

a high-precision use method of a low-resolution AD converter comprises the following steps:

s101, analog output branch introduction, which comprises establishing an analog signal source, wherein the quantization step size of the analog signal source is smaller than that of the acquisition AD converter, and the output full-scale range is larger than that of the acquisition AD converter;

s102, adding, wherein the adding comprises the steps of arranging an adder, adding the outputs of the analog output branch and the original detection branch through the adder, and outputting the added outputs to an AD converter for collection;

s103, detection execution, which comprises:

s201, recording the quantization step length of the analog output branch as

V；

S202, primary signal detection of the original detection path, and output increase of the analog output branch

V；

And S104, signal restoration, which comprises the steps of accumulating all the acquired curves, taking the average value, and then subtracting the known average value of the bias voltage to obtain a real curve after multiple acquisition.

Optionally, the analog output branch includes: the DA converter and connect the first operational amplifier in DA converter output, the first operational amplifier is configured as: the full-scale voltage attenuation circuit is used for attenuating the output voltage of the DA, so that the quantization step length output by the analog output branch is smaller than that of the acquisition AD converter, and the full-scale amplitude is larger than that of the acquisition AD converter.

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

Optionally, the adder includes a second operational amplifier.

In a second aspect, the present application provides an optical time domain reflectometer, which adopts the following technical scheme:

an optical time domain reflectometer, an AD acquisition path of the optical time domain reflectometer comprises:

an Avalanche Photodiode (APD) for converting an optical signal into a current signal;

a TIA operational amplifier, the input of which is connected with an avalanche photodiode APD;

the analog output branch circuit is used for outputting a full-scale amplitude which is larger than the quantization step length of the AD converter for acquisition, wherein the quantization step length of the analog output branch circuit is smaller than the quantization step length of the AD converter for acquisition;

and the input of the adder is connected with the analog output branch circuit and the output of the TIA operational amplifier, and the output of the adder is connected with the acquisition AD converter of the optical time domain reflector.

Optionally, the analog output branch includes: a DA converter and a first operational amplifier connected to an output of the DA converter, the DA converter configured to: the main control board is used for connecting the optical time domain reflectometer; the first operational amplifier is configured to: for attenuating the output voltage of the DA-converter.

Optionally, the main control board of the optical time domain reflectometer is configured to:

Δ V increases for each optical pulse transmission match; and the output voltage for controlling the DA converter is increased by Δ V and synchronized or advanced compared to the sending of the light pulses.

Optionally, the main control board of the optical time domain reflectometer is further configured to:

the database is used for establishing one-to-one correspondence of optical fiber measuring distance/time-optical pulse sending times;

the optical pulse transmitting device is used for acquiring the selected data of the optical fiber measuring distance/time, searching the database to call the corresponding optical pulse transmitting times, and executing the optical pulse transmitting action in the current measuring process according to the searching result.

Optionally, the main control board of the optical time domain reflectometer is further configured to:

the identity authentication system is used for acquiring identity authentication data of a user, and identifying and matching user identities in an identity information base;

the system is used for recording the use process of each time and binding the user identity; and the number of the first and second groups,

the optical fiber distance/time measuring device is used for retrieving the previous use record based on the identity of the user, determining the number of times of sending the previous used optical pulse, and working when the selected data of the new optical fiber distance/time measuring device is not received.

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

In summary, the present application includes at least one of the following beneficial technical effects: the method is equivalent to subdividing the quantization step size of the AD, and solves the problem that the output value of the AD converter is not changed enough due to weak change in the original curve, so that the real curve information is lost, and the low-order AD achieves the acquisition effect of using a higher-order AD converter, for example, an OTDR product using a 12-order or 14-order AD converter can be replaced by an 8-order or 10-order AD converter, so that the cost is reduced, and the influence of foreign chip limitation is reduced.

Drawings

FIG. 1 is a system block diagram of the present application;

FIG. 2 is a schematic diagram of waveforms collected by the present application;

fig. 3 is a circuit schematic of an operational amplifier attenuator of an embodiment of the present application.

Detailed Description

The present application is described in further detail below with reference to figures 1-3.

The embodiment of the application discloses a high-precision using method of a low-resolution AD converter.

Referring to fig. 1, a high-precision use method of a low-resolution AD converter includes:

s101, analog output branch introduction, which comprises establishing an analog signal source, wherein the quantization step of the analog signal source is smaller than that of the acquisition AD converter, and the output full-scale range is larger than that of the acquisition AD converter.

In one embodiment, the analog output branch includes: the DA converter and the first operational amplifier; wherein, the input of the DA converter is connected to a digital signal generating unit for control, for example: CPU-class, the output of the DA converter is connected to the input of a first operational Amplifier (AMP), the output of which serves as the analog signal output.

It is understood that the analog output branch can also select any other circuit structure capable of generating analog quantity meeting the above requirements; in this embodiment, the DA converter + the first operational amplifier is preferred, for one reason: the output regulation control of the DA converter is convenient and fast, and can be better matched with other contents.

The first operational amplifier functions in a circuit as follows: for attenuating (amplitude) the output voltage of the DA, that is, forming an attenuator with the first operational amplifier, the output quantity of the DA converter is attenuated to satisfy the above signal limitation for the analog output branch, which may be specifically based on the following:

1. the attenuated value of the quantization step of the DA converter is less than that of the AD converter;

2. the DA converter outputs the value of the full scale amplitude after attenuation which is larger than the quantization step size of the AD converter.

It is understood that the operational amplifier attenuator is the prior art, and the following another embodiment is matched with other limiting examples, which are not described herein again.

In one embodiment, the DA converter preferably includes: the low-speed low-precision DA converter reduces the cost and better meets the use requirement.

And S102, adding, namely, arranging an adder, adding the outputs of the analog output branch and the original detection branch through the adder, and outputting the added outputs to the AD converter for collection.

In one embodiment, the adder includes a second operational amplifier, that is, the adder is formed by the second operational amplifier to connect one output value of the DA converter to the acquisition circuit (the acquisition AD converter).

S103, detection execution, which comprises:

s201, recording the quantization step length of the analog output branch as

V；

S202, primary signal detection of the original detection path, and output increase of the analog output branch

V。

With OTDR coordination, the popular explanation is: as shown in figure 1 of the drawings, in which,

original: the APD is responsible for converting the optical signal into a current signal, and the TIA operational amplifier is responsible for converting the current signal into a voltage signal, amplifying the voltage signal and inputting the voltage signal into the AD converter for collection;

in the 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 the adder, the quantization step of the DA converter is recorded as Δ V, and the output voltage of the DA converter is controlled to increase by Δ V every time the OTDR system sends an optical pulse.

And S104, signal restoration, which comprises the steps of accumulating all the acquired curves, taking the average value, and then subtracting the known average value of the bias voltage to obtain a real curve after multiple acquisition.

As shown in fig. 2, which is a schematic diagram of the acquisition.

A1 first acquisition, the curve obtained is

；

A2, second collection, the obtained curve is

；

A3, collecting for the third time, the obtained curve is

；

An is the second

The curve obtained by the secondary collection is

。

According to the content, the quantization step size of the AD is equivalently subdivided, the problem that the output value of the AD converter is not changed enough due to weak change in the original curve, so that the real curve information is lost is solved, and the low-order AD achieves the acquisition effect of using a higher-order AD converter.

In one embodiment, the logic for both the above-described transmit light pulse, Δ V increase, is defined as: at least in synchronization, actually some execution earlier in time for the optical pulse. This is done because the ADC has already started to acquire when the light pulse is transmitted, taking into account time delay etc., and for a more realistic curve there needs to be no aliasing of the acquired signal all the way, for which reason a DA output increase needs to be performed before acquisition.

The embodiment of the application also discloses an optical time domain reflectometer.

The AD acquisition of the optical time domain reflectometer comprises the following steps:

an Avalanche Photodiode (APD) for converting an optical signal into a current signal;

a TIA operational amplifier, the input of which is connected with an avalanche photodiode APD;

the analog output branch circuit is used for outputting a full-scale amplitude which is larger than the quantization step length of the AD converter for acquisition, wherein the quantization step length of the analog output branch circuit is smaller than the quantization step length of the AD converter for acquisition;

and the input of the adder is connected with the analog output branch circuit and the output of the TIA operational amplifier, and the output of the adder is connected with the acquisition AD converter of the optical time domain reflector.

It is understood that the analog output branch and the adder are as shown in the foregoing method, and are not described in detail.

Based on the above: the DA converter is configured to: and the main control board is used for connecting the optical time domain reflectometer. And, the master control board of the optical time domain reflectometer is configured to: Δ V increases for each optical pulse transmission match; and the output voltage for controlling the DA converter is increased by Δ V and synchronized or advanced compared to the sending of the light pulses.

According to the above arrangement, the OTDR product as originally using a 12-bit or 14-bit AD converter can be replaced with an 8-bit or 10-bit AD converter, so that the equipment cost is reduced and the chip limitation is smaller.

In one embodiment, the present application further provides:

the master control board of the optical time domain reflectometer is further configured to: the database is used for establishing one-to-one correspondence of optical fiber measuring distance/time-optical pulse sending times; and the number of the first and second groups,

the optical pulse transmitting device is used for acquiring the selected data of the optical fiber measuring distance/time, searching the database to call the corresponding optical pulse transmitting times, and executing the optical pulse transmitting action in the current measuring process according to the searching result.

According to the content, a user can manually select the OTDR interactive interface, different acquisition times are selected according to different use requirements, and compared with a fixed form, signal loss and the like are not easy to occur, so that a more real signal curve is established.

In one embodiment, the present application further provides: the master control board of the optical time domain reflectometer is further configured to:

the identity authentication system is used for acquiring identity authentication data of a user, and identifying and matching user identities in an identity information base;

the system is used for recording the use process of each time and binding the user identity; and the number of the first and second groups,

the optical fiber distance/time measuring device is used for retrieving the previous use record based on the identity of the user, determining the number of times of sending the previous used optical pulse, and working when the selected data of the new optical fiber distance/time measuring device is not received.

It is to be understood that the above-mentioned authentication data may be any one of fingerprint/voiceprint/face data and the like. According to the arrangement, the OTDR equipment is relatively more convenient to use, and especially when the same person repeatedly carries out a large amount of same work, unnecessary operation can be reduced.

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

Based on the foregoing, the quantization step size may be adjustable: the DA converters are multiple and connected in parallel; when in use, the materials are selected according to requirements; it can also be: the attenuation of the operational amplifier attenuator is adjustable, and referring to fig. 3, the following example is shown:

the reverse input of the operational amplifier is connected with resistors R1 and R2 which are connected with each other in series, wherein R1 is connected with the input; the non-inverting input end of the operational amplifier is connected with the resistor R3, and the connection point is grounded; the other end of the resistor R3 is connected with the connection point of the resistor R1 and the resistor R2; the connection point of the resistor R2 and the operational amplifier is connected with the resistor R4, and the other end of the resistor R4 is connected with the output end of the operational amplifier. It can be understood that, in order to realize the adjustability of the attenuation, the fixed resistor is replaced by the adjustable resistor, the specific replacement item is determined according to the use requirement, and the operation port of the adjustable resistor is reserved in the OTDR.

In another embodiment, the master control board of the optical time domain reflectometer may be further configured to: and adjusting and controlling the quantization step of the analog output branch.

Based on the above, if: at least one adjustable resistor is replaced by: the base electrodes of the triodes are connected with the main control board to be controlled, and the emitting electrodes are connected in series to replace other resistors of the original adjustable resistor; the other resistors of the triode switch circuits have different resistance values.

When the circuit is used, different other resistors can be selected for use by controlling the conduction state of the triode switch circuit so as to realize the adjustment control of the quantization step length of the analog output branch.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims (10)

1. A high-precision use method of a low-resolution AD converter is characterized by comprising the following steps:

s101, analog output branch introduction, which comprises establishing an analog signal source, wherein the quantization step size of the analog signal source is smaller than that of the acquisition AD converter, and the output full-scale range is larger than that of the acquisition AD converter;

s102, adding, wherein the adding comprises the steps of arranging an adder, adding the outputs of the analog output branch and the original detection branch through the adder, and outputting the added outputs to an AD converter for collection;

s103, detection execution, which comprises:

s201, recording the quantization step length of the analog output branch as

V；

S202, primary signal detection of the original detection path, and output increase of the analog output branch

V；

And S104, signal restoration, which comprises the steps of accumulating all the acquired curves, taking the average value, and then subtracting the known average value of the bias voltage to obtain a real curve after multiple acquisition.

2. A high-precision use method of a low-resolution AD converter according to claim 1, characterized in that: the analog output branch comprises: the DA converter and connect the first operational amplifier in DA converter output, the first operational amplifier is configured as: the full-scale voltage attenuation circuit is used for attenuating the output voltage of the DA, so that the quantization step length output by the analog output branch is smaller than that of the acquisition AD converter, and the full-scale amplitude is larger than that of the acquisition AD converter.

3. A high-precision use method of a low-resolution AD converter according to claim 2, characterized in that: the DA converter is a low-speed low-precision DA converter.

4. High-precision use method of a low-resolution AD converter according to claim 1 or 2, characterized in that: the adder includes a second op-amp.

5. An optical time domain reflectometer, comprising: the AD acquisition path of the optical time domain reflectometer comprises the following steps:

an Avalanche Photodiode (APD) for converting an optical signal into a current signal;

a TIA operational amplifier, the input of which is connected with an avalanche photodiode APD;

the analog output branch circuit is used for outputting a full-scale amplitude which is larger than the quantization step length of the AD converter for acquisition, wherein the quantization step length of the analog output branch circuit is smaller than the quantization step length of the AD converter for acquisition;

and the input of the adder is connected with the analog output branch circuit and the output of the TIA operational amplifier, and the output of the adder is connected with the acquisition AD converter of the optical time domain reflector.

6. An optical time domain reflectometry according to claim 5, wherein: the analog output branch comprises: a DA converter and a first operational amplifier connected to an output of the DA converter, the DA converter configured to: the main control board is used for connecting the optical time domain reflectometer; the first operational amplifier is configured to: for attenuating the output voltage of the DA-converter.

7. An optical time domain reflectometry according to claim 6, wherein: the master control board of the optical time domain reflectometer is configured to:

Δ V increases for each optical pulse transmission match; and the output voltage for controlling the DA converter is increased by Δ V and synchronized or advanced compared to the sending of the light pulses.

8. An optical time domain reflectometry according to claim 7, wherein: the master control board of the optical time domain reflectometer is further configured to:

the database is used for establishing one-to-one correspondence of optical fiber measuring distance/time-optical pulse sending times;

the optical pulse transmitting device is used for acquiring the selected data of the optical fiber measuring distance/time, searching the database to call the corresponding optical pulse transmitting times, and executing the optical pulse transmitting action in the current measuring process according to the searching result.

9. An optical time domain reflectometry according to claim 8, wherein: the master control board of the optical time domain reflectometer is further configured to:

the identity authentication system is used for acquiring identity authentication data of a user, and identifying and matching user identities in an identity information base;

the system is used for recording the use process of each time and binding the user identity; and the number of the first and second groups,

the optical fiber distance/time measuring device is used for retrieving the previous use record based on the identity of the user, determining the number of times of sending the previous used optical pulse, and working when the selected data of the new optical fiber distance/time measuring device is not received.

10. An optical time domain reflectometry according to claim 5, wherein: the quantization step size of the analog output branch is configured to be adjustable and controlled by a main control board of the optical time domain reflectometer.

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