CN210327580U - Optical fiber time delay measuring device - Google Patents
Optical fiber time delay measuring device Download PDFInfo
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- CN210327580U CN210327580U CN201921959607.7U CN201921959607U CN210327580U CN 210327580 U CN210327580 U CN 210327580U CN 201921959607 U CN201921959607 U CN 201921959607U CN 210327580 U CN210327580 U CN 210327580U
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Abstract
The utility model discloses an optical fiber time delay measuring device, the TDC time digital conversion circuit that the device is connected for including CU the control unit and with CU the control unit, the amplitude limiting comparison amplifier, DA converting circuit, AD converting circuit and optical transmitter, the optical transmitter passes through optical circulator and connects optical receiver, optical receiver is connected with amplitude limiting comparison amplifier, optical receiver passes through AD converting circuit and connects CU the control unit, DA converting circuit, AD converting circuit also is connected with amplitude limiting comparison amplifier, a port of 2x2 optical divider is connected to the common port of optical circulator, first optical reflector is connected respectively to 3 other ports of 2x2 optical divider, second optical reflector and the one end of being surveyed the optic fibre, third optical reflector is connected to the other end of being surveyed the optic fibre. The device has low cost and good practicability.
Description
Technical Field
The utility model relates to an optical fiber measurement technique specifically is an optical fiber time delay measuring device.
Background
At present, the optical fiber time delay measurement method mainly includes a pulse measurement method, a phase measurement method and an optical interferometry, wherein the pulse measurement method can utilize a time-to-digital conversion circuit in a mature ToF (time of flight) measurement technology, so that a measurement device is simple and low in cost, but the measurement accuracy is relatively poor. In the pulse measurement method using the ToF (time of flight) measurement technique, the measurement accuracy thereof depends on the parameters of the time-to-digital conversion circuit; in addition, the bandwidth of the optical transmitter and the optical receiver used affects the rise time response of the optical pulse signal, which may severely restrict the time measurement accuracy, but if the optical transmitter and the optical receiver with high bandwidth are used, the cost is too high. Therefore, there is a need to improve the current solutions to obtain better time measurement accuracy with less cost penalty.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing an optical fiber time delay measuring device to the not enough of prior art. The device has low cost and good practicability.
Realize the utility model discloses the technical scheme of purpose is:
an optical fiber time delay measuring device is different from the prior art and comprises a CU control unit formed by an FPGA or an ARM processor or other commercial microprocessors, a TDC time digital conversion circuit, a limiting comparison amplifier, a D/A conversion circuit, an A/D conversion circuit and an optical transmitter, wherein the TDC time digital conversion circuit is connected with the CU control unit and is formed by a TDC7201 of Texas instruments company, a TDC-GPX series of ACAM company of Germany or other commercial time digital conversion circuits, the optical transmitter is connected with an optical receiver through an optical circulator, the optical receiver is connected with the limiting comparison amplifier, the optical receiver is connected with the CU control unit through the A/D conversion circuit, the D/A conversion circuit and the A/D conversion circuit are also connected with the limiting comparison amplifier, the public end of the optical circulator is connected with one port of a 2x2 optical splitter, and the other 3 ports of the 2x2 optical splitters are respectively connected with a first optical reflector, The second light reflector and one end of the measured optical fiber, and the other end of the measured optical fiber is connected with the third light reflector.
The splitting ratio of the 2x2 optical splitter is A (100-A), and the value range of A is 1-10.
The reflection coefficient of the first light reflector is as follows: -10 dB-40 dB.
The reflection coefficients of the second light reflector and the third light reflector are as follows: 0-1 dB.
The amplitude limiting comparison amplifier adopts a controllable comparison threshold value which is 1/2 of the amplitude value of the pulse signal.
When the device is used for measurement, the method comprises the following steps:
1) predicting the amplitude value and the time position of the pulse: the CU control unit controls the optical transmitter to transmit a pulse signal, the optical receiver receives the pulse signal sequence, the pulse signal sequence is output to the A/D conversion circuit after being amplified, the A/D conversion circuit and the CU control unit sample the pulse signal sequence, and the CU control unit acquires the amplitude value and the time position of each pulse in the pulse signal sequence;
2) the CU control unit controls the optical transmitter to transmit a pulse signal, and the optical receiver receives the pulse signal, amplifies the pulse signal and outputs the amplified pulse signal to the input end of the amplitude limiting comparison amplifier;
3) while step 2 is carried out, the CU control unit controls the D/A conversion circuit to output a voltage to the limiting comparison amplifier as a comparison threshold value according to the predicted values of the pulse amplitude and the time position obtained in step 1 in a time period for predicting the occurrence of the pulse by the CU control unit, wherein the comparison threshold value is 1/2 of the predicted value of the pulse amplitude;
4) the CU control unit selects a first pulse as a 'start' pulse signal and an N +1 th pulse as an 'end' pulse signal from pulse signals sent by the amplitude limiting comparison amplifier, and sends the 'start' pulse signal and the 'end' pulse signal to the TDC time-to-digital conversion circuit, wherein N is more than or equal to 1;
5) according to the 'start' and 'end' pulse signals, the TDC time-digital conversion circuit obtains the time value of the optical signal to and from the tested optical fiber for a plurality of times, and the time value is converted into a digital signal by the time-digital conversion circuit and sent to the CU control unit.
The working principle of the technical scheme is as follows: in the pulse measurement method adopted in the prior art optical fiber delay measurement scheme, an optical pulse signal generates two pulse signals only when entering and leaving a measured optical fiber as trigger signals of the start and end times of time measurement, and between the start and end times of time measurement, the optical signal only passes through or reciprocates the measured optical fiber once, assuming that the length of the measured optical fiber is L, and the optical signal reciprocates to the measured optical fiber once, the time required for the optical signal to reciprocate in the length of the measured optical fiber is 2L/V, V is the optical speed in the measured optical fiber, the time measurement error of a measurement circuit is σ, and the delay measurement result T = (2L/V ± σ)/2 of the measured optical fiber, in this case, the delay measurement error of the measured optical fiber is σ/2;
in the technical scheme, an optical signal is selected to make N round trips to a measured optical fiber, assuming that the length of the measured optical fiber is L, the time required for the optical signal to make N round trips to the measured optical fiber is 2NL/V, V is the speed of light in the measured optical fiber, the time measurement error of a measurement circuit is σ, and the time delay measurement result T = (2 NL/V ± σ)/2N of the measured optical fiber. In this case, the delay measurement error of the measured optical fiber is σ/2N;
if the value of N is larger, the time delay measurement error of the measured optical fiber can be greatly reduced under the condition that the time measurement errors of the measurement circuit are the same.
In the technical scheme, two light reflectors, namely a light reflector 2 and a light reflector 3, are adopted, a measured optical fiber is positioned between the two light reflectors, an optical pulse signal is reflected back and forth between the light reflector 2 and the light reflector 3 for multiple times, the optical pulse signal returns to and returns to the measured optical fiber for multiple times, and an optical pulse signal output is generated when the optical pulse signal returns to and returns to the measured optical fiber every time, therefore, when an optical transmitter sends an optical pulse test signal to the measured optical fiber, an optical receiver receives a signal sequence with the same pulse interval, the time difference of the occurrence of the first and the (N + 1) th optical pulse signals is selected and measured, the time of the optical pulse signal returning to the measured optical fiber for N times can be obtained, and the time is divided by 2N, and the result is the transmission delay of the optical signal in the measured optical fiber.
As mentioned above, the optical pulse signal is reflected between the optical reflector 2 and the optical reflector 3 for multiple times, and multiple times of round trip to the tested optical fiber, and each round trip to the tested optical fiber will generate an optical pulse signal output, and finally the optical receiver receives a signal sequence with the same pulse interval time, because the optical reflector 2, the optical reflector 3, the optical fiber to be detected and other optical components in the device all produce different degrees of attenuation to the optical signal, the optical signal is attenuated once every round trip of the optical fiber to be detected, so that the pulse in the optical pulse signal sequence received by the optical receiver, the amplitude value of the optical fiber is gradually reduced, the gradient of the amplitude change is related to the attenuation of the optical signal by the optical fiber to be detected and the optical components in the device, even if the loss of the optical fiber connector between the measured optical fiber and the measuring device changes, the gradient of the amplitude change of the optical pulse signal is directly changed.
The optical receiver amplifies the received optical pulse signal sequence, and then sends the optical pulse signal sequence to a limiter comparison amplifier, the limiter comparison amplifier carries out amplitude limiting comparison amplification on the optical pulse signal sequence, the pulse signal after amplitude limiting amplification becomes a '0' type digital pulse signal and a '1' type digital pulse signal and is sent to a CU control unit; the CU control unit selects the pulse signals, wherein the first pulse signal becomes a 'start' pulse signal, the subsequent pulse signal becomes an 'end' pulse signal, and the 'start' pulse signal and the 'end' pulse signal are sent to the time-to-digital conversion circuit; the time-to-digital conversion circuit obtains the time value of the optical signal to and from the tested optical fiber for a plurality of times according to the pulse signals of 'start' and 'end', and the time value is converted into a digital signal by the time-to-digital conversion circuit and sent to the CU control circuit unit.
In the above process, because the amplitude of the input optical pulse signal received by the optical receiver is changed, the output amplitude of the input optical pulse signal is also changed, and the front edge and the back edge of the output pulse signal of the optical receiver have a certain slope, when the amplitude limiting comparison amplifier performs amplitude limiting comparison amplification on the input optical pulse signal, a fixed comparison threshold cannot be used, otherwise, the time measurement accuracy can be seriously affected.
In the technical scheme, before time delay measurement is carried out on a measured optical fiber, a pulse signal is transmitted firstly, an optical receiver receives a pulse signal sequence and outputs the pulse signal sequence to an A/D conversion circuit, the A/D conversion circuit and a CU control unit sample the pulse signal sequence, the CU control unit obtains amplitude values and rough time positions of all pulses in the pulse signal sequence, and when the time delay measurement is carried out on the subsequent measured optical fiber, the amplitude values and time position parameters of the pulses are used as predicted values of the amplitude values and the time positions of all pulses in the pulse signal sequence.
When a certain pulse is subjected to amplitude limiting comparison amplification, according to the prediction of the amplitude and the time position of the pulse, the CU control unit controls the D/A conversion circuit to output a voltage value, such as 1/2 of a predicted value of the pulse amplitude, as a comparison threshold value of the amplitude limiting comparison amplifier in a time period when the pulse is predicted to appear.
The device has low cost and good practicability.
Drawings
Fig. 1 is a schematic structural diagram of an optical fiber delay measuring device in an embodiment.
Detailed Description
The contents of the present invention will be further described with reference to the accompanying drawings and examples, but the present invention is not limited thereto.
Example (b):
referring to fig. 1, an optical fiber time delay measuring device includes a CU control unit, a TDC time-to-digital conversion circuit, a limiting comparison amplifier, a D/a conversion circuit, an a/D conversion circuit, and an optical transmitter connected to the CU control unit through an optical circulator, the optical receiver is connected to the limiting comparison amplifier, the optical receiver is connected to the CU control unit through the a/D conversion circuit, the D/a conversion circuit and the a/D conversion circuit are also connected to the limiting comparison amplifier, a common port of the optical circulator is connected to one port of a 2x2 optical splitter, the other 3 ports of the 2x2 optical splitter are respectively connected to one end of a first optical reflector, a second optical reflector, and a measured optical fiber, and the other end of the measured optical fiber is connected to a third optical reflector.
The CU control unit in this example is constituted by an ARM processor.
The TDC time-to-digital conversion circuit of this example employs TDC7201 by Texas instruments, USA.
The splitting ratio of the 2x2 optical splitter is A (100-A), and the value range of A is 1-10.
The reflection coefficient of the first light reflector is as follows: -10 dB-40 dB.
The reflection coefficients of the second light reflector and the third light reflector are both 0-1 dB.
The amplitude limiting comparison amplifier adopts a controllable comparison threshold value which is 1/2 of the amplitude value of the pulse signal.
When the device is used for measurement, the method comprises the following steps:
1) predicting the amplitude value and the time position of the pulse: the CU control unit controls the optical transmitter to transmit a pulse signal, the optical receiver receives the pulse signal sequence, the pulse signal sequence is output to the A/D conversion circuit after being amplified, the conversion A/D circuit and the CU control unit sample the pulse signal sequence, and the CU control unit acquires the amplitude value and the time position of each pulse in the pulse signal sequence;
2) the CU control unit controls the optical transmitter to transmit a pulse signal, and the optical receiver receives the pulse signal, amplifies the pulse signal and outputs the amplified pulse signal to the input end of the amplitude limiting comparison amplifier;
3) while step 2 is carried out, the CU control unit controls the D/A conversion circuit to output a voltage to the limiting comparison amplifier as a comparison threshold value according to the predicted values of the pulse amplitude and the time position obtained in step 1 in a time period for predicting the occurrence of the pulse by the CU control unit, wherein the comparison threshold value is 1/2 of the predicted value of the pulse amplitude;
4) the CU control unit selects a first pulse as a 'start' pulse signal and an N +1 th pulse as an 'end' pulse signal from pulse signals sent by the amplitude limiting comparison amplifier, and sends the 'start' pulse signal and the 'end' pulse signal to the TDC time-to-digital conversion circuit, wherein N is more than or equal to 1;
5) according to the 'start' and 'end' pulse signals, the TDC time-digital conversion circuit obtains the time value of the optical signal to and from the tested optical fiber for a plurality of times, and the time value is converted into a digital signal by the time-digital conversion circuit and sent to the CU control unit.
The working principle of the technical scheme is as follows: in the pulse measurement method adopted in the prior art optical fiber delay measurement scheme, an optical pulse signal generates two pulse signals only when entering and leaving a measured optical fiber as trigger signals of the start and end times of time measurement, and between the start and end times of time measurement, the optical signal only passes through or reciprocates the measured optical fiber once, assuming that the length of the measured optical fiber is L, and the optical signal reciprocates to the measured optical fiber once, the time required for the optical signal to reciprocate in the length of the measured optical fiber is 2L/V, V is the optical speed in the measured optical fiber, the time measurement error of a measurement circuit is σ, and the delay measurement result T = (2L/V ± σ)/2 of the measured optical fiber, in this case, the delay measurement error of the measured optical fiber is σ/2;
in the technical scheme, an optical signal is selected to make N round trips to a measured optical fiber, assuming that the length of the measured optical fiber is L, the time required for the optical signal to make N round trips to the measured optical fiber is 2NL/V, V is the speed of light in the measured optical fiber, the time measurement error of a measurement circuit is σ, and the time delay measurement result T = (2 NL/V ± σ)/2N of the measured optical fiber. In this case, the delay measurement error of the measured optical fiber is σ/2N;
if the value of N is larger, the time delay measurement error of the measured optical fiber can be greatly reduced under the condition that the time measurement errors of the measurement circuit are the same.
In the technical scheme, two light reflectors, namely a light reflector 2 and a light reflector 3, are adopted, a measured optical fiber is positioned between the two light reflectors, an optical pulse signal is reflected back and forth between the light reflector 2 and the light reflector 3 for multiple times, the optical pulse signal returns to and returns to the measured optical fiber for multiple times, and an optical pulse signal output is generated when the optical pulse signal returns to and returns to the measured optical fiber every time, therefore, when an optical transmitter sends an optical pulse test signal to the measured optical fiber, an optical receiver receives a signal sequence with the same pulse interval, the time difference of the occurrence of the first and the (N + 1) th optical pulse signals is selected and measured, the time of the optical pulse signal returning to the measured optical fiber for N times can be obtained, and the time is divided by 2N, and the result is the transmission delay of the optical signal in the measured optical fiber.
As mentioned above, the optical pulse signal is reflected between the optical reflector 2 and the optical reflector 3 for multiple times, and multiple times of round trip to the tested optical fiber, and each round trip to the tested optical fiber will generate an optical pulse signal output, and finally the optical receiver receives a signal sequence with the same pulse interval time, because the optical reflector 2, the optical reflector 3, the optical fiber to be detected and other optical components in the device all produce different degrees of attenuation to the optical signal, the optical signal is attenuated once every round trip of the optical fiber to be detected, so that the pulse in the optical pulse signal sequence received by the optical receiver, the amplitude value of the optical fiber is gradually reduced, the gradient of the amplitude change is related to the attenuation of the optical signal by the optical fiber to be detected and the optical components in the device, even if the loss of the optical fiber connector between the measured optical fiber and the measuring device changes, the gradient of the amplitude change of the optical pulse signal is directly changed.
The optical receiver amplifies the received optical pulse signal sequence, and then sends the optical pulse signal sequence to an amplitude limiter comparison amplifier, the amplitude limiter comparison amplifier carries out amplitude limiting comparison amplification on the optical pulse signal sequence, the pulse signal after amplitude limiting amplification becomes a '0' type digital pulse signal and a '1' type digital pulse signal, and the pulse signal is sent to a control unit; the control unit selects the pulse signals, wherein the first pulse signal becomes a 'start' pulse signal, the subsequent pulse signal becomes an 'end' pulse signal, and the 'start' pulse signal and the 'end' pulse signal are sent to the time-to-digital conversion circuit; the time-to-digital conversion circuit obtains the time value of the optical signal to and from the tested optical fiber for a plurality of times according to the pulse signals of 'start' and 'end', and the time value is converted into a digital signal by the time-to-digital conversion circuit and sent to the control circuit unit.
In the above process, because the amplitude of the input optical pulse signal received by the optical receiver is changed, the output amplitude of the input optical pulse signal is also changed, and the front edge and the back edge of the output pulse signal of the optical receiver have a certain slope, when the amplitude limiting comparison amplifier performs amplitude limiting comparison amplification on the input optical pulse signal, a fixed comparison threshold cannot be used, otherwise, the time measurement accuracy can be seriously affected.
In the technical scheme, before time delay measurement is carried out on a measured optical fiber, a pulse signal is transmitted firstly, an optical receiver receives a pulse signal sequence and outputs the pulse signal sequence to an A/D conversion circuit, the A/D conversion circuit and a CU control unit sample the pulse signal sequence, the CU control unit obtains amplitude values and rough time positions of all pulses in the pulse signal sequence, and when the time delay measurement is carried out on the subsequent measured optical fiber, the amplitude values and time position parameters of the pulses are used as predicted values of the amplitude values and the time positions of all pulses in the pulse signal sequence.
When a certain pulse is subjected to amplitude limiting comparison amplification, according to the prediction of the amplitude and the time position of the pulse, the CU control unit controls the D/A conversion circuit to output a voltage value, such as 1/2 of a predicted value of the pulse amplitude, as a comparison threshold value of the amplitude limiting comparison amplifier in a time period when the pulse is predicted to appear.
In the optical transmitter, the light source uses a single longitudinal mode semiconductor laser such as DFB-LD; and preferably, an automatic temperature control circuit can be used, so that the temperature of the laser is stable, and the influence of the wavelength change of the laser on the measurement precision of the optical fiber time delay can be reduced.
Claims (5)
1. An optical fiber time delay measuring device is characterized by comprising a CU control unit, a TDC time digital conversion circuit, a limiting comparison amplifier, a D/A conversion circuit, an A/D conversion circuit and an optical transmitter, wherein the TDC time digital conversion circuit, the limiting comparison amplifier, the D/A conversion circuit, the A/D conversion circuit and the optical transmitter are connected with the CU control unit through optical circulators, the optical receiver is connected with the limiting comparison amplifier and the optical receiver is connected with the CU control unit through the A/D conversion circuit, the D/A conversion circuit and the A/D conversion circuit are also connected with the limiting comparison amplifier, the common end of the optical circulators is connected with one port of a 2x2 optical splitter, the other 3 ports of the 2x2 optical splitter are respectively connected with a first optical reflector, a second optical reflector and one end of a measured optical fiber, and the other end of the measured optical.
2. The optical fiber time delay measuring device of claim 1, wherein the splitting ratio of the 2x2 optical splitter is A (100-A), and the value range of A is 1-10.
3. The optical fiber delay measuring device of claim 1, wherein the reflection coefficient of the first optical reflector is: -10 dB-40 dB.
4. The optical fiber delay measuring device of claim 1, wherein the reflection coefficients of the second and third light reflectors are both 0-1 dB.
5. The optical fiber delay measuring device of claim 1, wherein the limiting comparison amplifier uses a controllable comparison threshold value, and the comparison threshold value is 1/2 of the amplitude value of the pulse signal.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110649964A (en) * | 2019-11-14 | 2020-01-03 | 桂林聚联科技有限公司 | Optical fiber time delay measuring device and measuring method |
| CN113328793A (en) * | 2021-06-17 | 2021-08-31 | 西北核技术研究所 | Remote optical fiber transmission delay testing method and system based on time domain reflection difference |
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2019
- 2019-11-14 CN CN201921959607.7U patent/CN210327580U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110649964A (en) * | 2019-11-14 | 2020-01-03 | 桂林聚联科技有限公司 | Optical fiber time delay measuring device and measuring method |
| CN110649964B (en) * | 2019-11-14 | 2024-01-16 | 桂林聚联科技有限公司 | Method for measuring optical fiber time delay |
| CN113328793A (en) * | 2021-06-17 | 2021-08-31 | 西北核技术研究所 | Remote optical fiber transmission delay testing method and system based on time domain reflection difference |
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