CN216718202U

CN216718202U - Double-optical fiber end surface interference salinity detection device based on digital signal processing

Info

Publication number: CN216718202U
Application number: CN202123059174.XU
Authority: CN
Inventors: 李广
Original assignee: Guangdong Institute of Science and Technology
Current assignee: Guangdong Institute of Science and Technology
Priority date: 2021-12-07
Filing date: 2021-12-07
Publication date: 2022-06-10
Anticipated expiration: 2031-12-07

Abstract

The utility model provides a double-optical-fiber end-face interference salinity detection device based on digital signal processing, which comprises an input optical signal generation module, an optical fiber end-face interference salinity detection module and a salinity detection module, wherein the input optical signal generation module comprises an electro-optical modulator, and the electro-optical modulator is used for modulating an optical signal by using a radio-frequency signal to form an input optical signal; the optical circulator is connected with the electro-optical modulator and receives an input optical signal; the salinity sensor is connected with the second port, a return light signal formed by an input light signal passing through the salinity sensor is transmitted to the third port from the second port, the salinity sensor is provided with a first reflection end face and a second reflection end face, a single-mode optical fiber is arranged between the first reflection end face and the second reflection end face, and the second reflection end face is soaked in seawater to be detected; a photodetector that receives the return light signal and converts the return light signal into a measurement electric signal; the analog-to-digital converter receives the measuring electric signal and converts the measuring electric signal into a digital signal; and the digital signal processor receives the digital signal output by the analog-to-digital converter. The utility model has small volume and low production cost.

Description

Double-optical fiber end surface interference salinity detection device based on digital signal processing

Technical Field

The utility model relates to the field of salinity detection of seawater, in particular to a double-optical-fiber end surface interference salinity detection device based on digital signal processing.

Background

The seawater salinity in different regions is often different, and the change of the seawater salinity often has great influence on the marine ecology, therefore, the seawater salinity needs to be monitored, for example, the seawater salinity in some specific regions needs to be detected periodically. The existing system (SDS) for detecting the salinity of the seawater is often provided with a device for detecting the salinity of the seawater.

Referring to fig. 1, the existing seawater salinity detecting device comprises an erbium-doped fiber amplifier 11, an electro-optical modulator 12, a salinity sensor 13, an optical circulator 14, a photoelectric detector 15 and an electronic spectrum analyzer 16. Erbium doped fiber amplifier 11 outputs optical signals to electro-optic modulator 12, and electro-optic modulator 12 also receives radio frequency signals, for example, connects to a Radio Frequency (RF) signal source and receives RF signals. It can be seen that the existing seawater salinity detecting device uses the amplified spontaneous emission signal (ASE) emitted by the erbium-doped fiber amplifier 11, and then is electro-optically modulated by the electro-optical modulator 12 by using the electrical signal generated by the radio frequency signal source, and the modulated optical signal is then sent to the first port 141 of the optical circulator 14 and enters the salinity sensor 13 through the second port 142. During detection, a part of the salinity sensor 13 is immersed in seawater to be detected, and since the frequency of the optical signal changes after the optical signal passes through seawater with different salinity, the changed optical signal is transmitted to the third port 143 through the second port 142 of the optical circulator 14, and is incident to the photoelectric detector 15 through the third port 143.

The photodetector 15 performs photoelectric modulation on the optical signal passing through the salinity sensor 13, converts the optical signal into an electrical signal, outputs the obtained electrical signal to the electronic spectrum analyzer 16, and performs spectrum analysis on the photoelectrically converted signal by the electronic spectrum analyzer, thereby calculating the salinity of the seawater. For example, the salinity sensor 13 includes two physical contact optical fibers and a single-mode optical fiber, the single-mode optical fiber is located between the two physical contact optical fibers, and an end surface of each physical contact optical fiber is provided with a reflection end surface, the reflection end surface of one of the physical contact optical fibers is immersed in seawater to be detected, a reference solution with known salinity is provided between the other physical contact optical fiber and the APC connector, a first reflection signal is formed when an optical signal passes through the first reflection end surface, and a second reflection signal is formed on the second reflection end surface after a part of the optical signal passes through the first reflection end surface and passes through the single-mode optical fiber, microwave interference is formed due to a time delay between the first reflection signal and the second reflection signal, only an optical signal with a specific frequency can pass through the third port of the optical circulator, and an optical signal emitted from the optical circulator forms a measurement electrical signal after passing through the photodetector 15, the measured electrical signal is analyzed and calculated by the electronic spectrum analyzer 16 to obtain the salinity value of the seawater to be detected.

However, since the electronic spectrum analyzer 16 is generally expensive and large in size, the existing seawater salinity detecting apparatus is often installed in a laboratory. When the salinity of the seawater is detected, a sample bottle is usually required to be used for loading a certain amount of seawater to a specified sea area, and then the seawater is brought to a laboratory for detection. However, a certain distance is often kept between a laboratory and a sea area to be detected, and the existing seawater salinity detection device is not suitable for outdoor seawater salinity detection, so that the convenience of detection is influenced.

Disclosure of Invention

The utility model aims to provide a double-optical-fiber end surface interference salinity detection device based on digital signal processing, which can reduce the detection cost and improve the detection convenience.

In order to achieve the above object, the device for detecting the end surface interference salinity of the dual optical fiber based on digital signal processing provided by the utility model comprises an input optical signal generation module, wherein the input optical signal generation module comprises an electro-optical modulator, and the electro-optical modulator modulates an optical signal by using a radio frequency signal to form an input optical signal; the optical circulator is provided with a first port, a second port and a third port, and the first port is connected with the electro-optical modulator and receives an input optical signal; the salinity sensor is connected with the second port of the optical circulator, and a return optical signal formed by an input optical signal passing through the salinity sensor is transmitted to the third port from the second port, wherein the salinity sensor is provided with a first reflection end face and a second reflection end face, a single-mode optical fiber is arranged between the first reflection end face and the second reflection end face, and the second reflection end face is soaked in seawater to be detected; the photoelectric detector is connected with the third port of the optical circulator, receives the return optical signal and converts the return optical signal into a measurement electric signal; the analog-to-digital converter is used for receiving the measuring electric signal and converting the measuring electric signal into a digital signal; and the digital signal processor receives the digital signal output by the analog-to-digital converter.

According to the scheme, the measurement electric signal acquired by the photoelectric detector is subjected to analog-to-digital conversion to obtain a digital signal, and the digital signal processor is used for processing the received digital signal to calculate and obtain the salinity value of the seawater. The digital signal processor has small volume and low production cost, so that the production cost and the volume of the seawater salinity detection device can be greatly reduced, and the seawater salinity can be conveniently detected in real time outdoors.

In a preferred embodiment, the digital signal processor has a display interface module for connecting to a display and outputting a display signal to the display.

Therefore, the calculation result of the digital signal processor can be output to the display screen and displayed by the display screen, and a user can conveniently check the detection result in real time.

The digital signal processor is arranged in the portable terminal equipment, and the display interface module is arranged on the shell of the portable terminal equipment.

Therefore, the digital signal processor can be integrated on handheld equipment such as a PDA (personal digital assistant), and information such as a detection result is displayed through a display screen of the handheld equipment, so that a user can check the detection result in real time.

In a further aspect, a filter circuit is disposed between the analog-to-digital converter and the digital signal processor, and preferably, the filter circuit is a band-pass filter circuit.

Therefore, the measurement electric signal output by the photoelectric detector is filtered through the filter circuit, so that the analog signal received by the analog-to-digital converter is smoother, and the received analog signal is ensured to be the analog signal with specific frequency, so that the interference of the interference signal to the calculation of the digital signal processor is avoided.

The input optical signal generation module further comprises a band-pass filter and a signal amplifier, and the wireless signal output by the band-pass filter is output to the electro-optical modulator after passing through the signal amplifier.

Therefore, the wireless signals can be acquired from the air through the band-pass filter and used as radio-frequency signals of electro-optical modulation, and therefore detection can be conveniently carried out outdoors.

In a further aspect, the number of the band pass filters is two or more, and the plurality of band pass filters correspond to different frequency bands. Preferably, the electro-optical modulator is a direct modulation electro-optical modulator.

Therefore, the direct-modulation type electro-optical modulator can directly modulate the voltage or the current of the light source by the radio-frequency signal, and compared with an erbium-doped optical fiber amplifier, the volume and the production cost of the seawater salinity detection device can be reduced.

Optionally, the input optical signal generating module includes an erbium-doped fiber amplifier and a radio frequency signal generator, where the erbium-doped fiber amplifier inputs the optical signal to the electro-optical modulator, and the radio frequency signal generator inputs the radio frequency signal to the electro-optical modulator.

Drawings

Fig. 1 is a block diagram of a conventional apparatus for detecting salinity of seawater.

FIG. 2 is a block diagram of a first embodiment of the double-fiber end-face interference salinity detection apparatus based on digital signal processing.

FIG. 3 is a block diagram of the salinity sensor in the first embodiment of the dual-fiber end-face interference salinity detecting device based on digital signal processing.

FIG. 4 is an electrical schematic diagram of the filter circuit and the analog-to-digital converter in the first embodiment of the dual-fiber end-face interference salinity detection apparatus based on digital signal processing according to the present invention.

FIG. 5 is a block diagram of the second embodiment of the double-fiber end-face interference salinity detection apparatus based on digital signal processing.

The utility model is further explained with reference to the drawings and the embodiments.

Detailed Description

The double-optical-fiber end-face interference salinity detection device based on digital signal processing is used for detecting seawater salinity, the production cost is reduced by using the digital signal processor to replace an electronic spectrum analyzer, and the volume is also reduced, so that the detection is convenient outdoors.

The first embodiment:

referring to fig. 2, the salinity detecting apparatus of the present embodiment includes an erbium-doped fiber amplifier 21, an electro-optical modulator 22, a salinity sensor 23, an optical circulator 24, a photodetector 25, a filter circuit 26, an analog-to-digital converter 27, a digital signal processor 28, and a display interface module 29. Specifically, the erbium-doped fiber amplifier 21 generates an optical signal and outputs the optical signal to the electro-optical modulator 22, and the electro-optical modulator 22 further receives a wireless radio frequency signal, for example, the wireless radio frequency signal provided by a wireless radio frequency signal source is received, and the optical signal is modulated by using the wireless radio frequency signal, so as to obtain the input optical signal. The input optical signal is output to an optical circulator 24.

The optical circulator 24 has three ports, i.e., a first port 241, a second port 242, and a third port 243, and an optical signal incident on the optical circulator 24 from the first port 241 can be emitted only from the second port 242, and an optical signal incident on the optical circulator 24 from the second port 242 can be emitted only from the third port 243, and cannot be transmitted in the reverse direction.

The output terminal of the electro-optical modulator 22 is connected to the first port 241 of the optical circulator 24, and thus, the input optical signal enters the first port 241 and exits the second port 242. Salinity sensor 23 is connected to second port 242 of optical circulator 24 so the input optical signal is incident on salinity sensor 23 from second port 242.

Referring to fig. 3, an optical fiber 231, an APC connector 232, a first segment of physical contact optical fiber 235, a single mode optical fiber 236, and a second segment of physical contact optical fiber 237 are disposed in the salinity sensor 23, wherein a first end of the optical fiber 231 is connected to a second port 242 of the optical circulator 24, and the APC connector 232 is disposed at a second end of the optical fiber 23. Wherein, the outer end face of the APC connector 232 forms an inclined plane of 8 °, that is, the outer end face of the APC connector forms an angle of 8 ° with the axis. The first end face 234 of the first segment of physical contact optical fiber 235 is a conventional PC connector, i.e., a face polished to a micro-sphere, so the first end face 234 will form a first reflective end face. The second end of the first length of physical contact fiber 235 is an APC splice and is connected to a single mode fiber 236. The second segment of the physical contact optical fiber 237 has a second end face 239, the second end face 239 is a free end of the second segment of the physical contact optical fiber 237, the second end face 239 is also a common PC connector, i.e. an end face polished to a micro-sphere, and thus, the second end face 239 will form a second reflective end face. The other end of the second segment of physical contact fiber 237 is provided with an APC splice that is connected to the single mode fiber 236. In addition, the second end face 239 of the second segment of the physical contact optical fiber 237 extends into the accommodating cavity 238, the accommodating cavity 238 is filled with seawater to be detected, and preferably, the second end face 239 is completely immersed in the seawater to be detected.

In addition, a holding chamber 233 is disposed between the APC connector 232 and a first end face 234 of the first length of physical contact optical fiber 231, and the holding chamber 233 is filled with a reference solution of a preset salinity, for example, seawater of a known salinity. An input optical signal passes through the optical fiber 231, exits from the APC connector 232, and penetrates through the reference solution, and a portion of the optical signal is reflected by the first end face 234 and incident on the optical fiber 231, thereby forming a first reflected signal. Another portion of the input optical signal will pass through the first end face 234 and be incident on the first segment of physical contact fiber 235, then pass through the single-mode fiber 236 to the second segment of physical contact fiber 237, and be reflected on the second end face 239 to form a second reflected signal, which in turn passes through the second segment of physical contact fiber 237, the single-mode fiber 236, the first segment of physical contact fiber 235 and is incident on the optical fiber 231, and then enters the second port 242 of the optical circulator 24. Therefore, the first reflected signal and the second reflected signal actually pass through the optical circulator 24 one after another, and there is a time difference between the first reflected signal and the second reflected signal when passing through the third port 243 of the optical circulator 24. Thus, a microwave photonic filter is formed at the third port 243 of the optical circulator 24.

In this embodiment, the length of the single mode fiber 236 is between 1.5 km and 2.5 km, preferably, the length of the single mode fiber 236 is 2 km, and the lengths of the first segment of the physical contact fiber 235 and the second segment of the physical contact fiber 237 are equal and do not exceed 5 m, preferably, the lengths of the first segment of the physical contact fiber 235 and the second segment of the physical contact fiber 237 are between 2 m and 3 m. It can be seen that the length of the single mode optical fiber 236 is much greater than the length of the first and second lengths of physical contact

optical fibers

235, 237.

Thus, within the salinity sensor 23, since the second end face 239 of the second segment of physical contact optical fiber 237 is completely immersed in the seawater to be tested, the seawater having a known salinity between the first end face 234 and the APC connector 232, such that the first reflected signal and the second reflected signal form microwave interference at the third port 243 of the optical circulator 24. According to the microwave interference principle, only the optical signal with a specific wavelength can pass through the microwave interferometer, and therefore, of the interference signals formed by the first reflected signal and the second reflected signal, only the optical signal with the specific wavelength is output from the third port 243 of the optical circulator 24, the output optical signal is received by the photodetector 25, and the photodetector 25 performs photoelectric conversion on the received optical signal, converts the optical signal into an electrical signal, and forms a measurement electrical signal. The photodetector 25 outputs the measurement electrical signal to the filter circuit 26, the measurement electrical signal is filtered and then output to the analog-to-digital converter 27, the analog signal is converted into a digital signal, and the digital signal obtained by the conversion is output to the digital signal processor 28.

Referring to fig. 4, the filter circuit 26 includes two filter capacitors C4 and C5 connected IN parallel, and the measurement electrical signal output from the photodetector 25 is input to the filter circuit 26 from the terminal IN and then passes through the filter capacitors C4 and C5, so that the measurement electrical signal output from the photodetector 25 is smoother under the action of the filter circuit.

The analog-to-digital converter 27 includes an analog-to-digital conversion chip U1, the filtered measurement electrical signal is input to an input terminal AIN of the analog-to-digital conversion chip U1, and the analog-to-digital conversion chip U1 converts the analog signal into a digital signal and outputs the digital signal from output terminals SDA, SCL. The analog-to-digital conversion chip U1 is implemented by a known analog-to-digital conversion chip, and the process of converting an analog signal into a digital signal is also known, and will not be described herein.

The analog-to-digital converter 27 outputs the digital signal obtained after the conversion to the digital signal processor 28, and preferably, the digital signal processor 28 is provided in a portable terminal device, such as a PDA. Preferably, the PDA has a display screen, and a display interface module 29 is provided in the PDA, the digital signal processor 28 is electrically connected to the display interface module 29 and transmits data to the display interface module 29, and the display interface module 29 is connected to the display screen of the PDA and transmits data to the display screen.

After the analog-to-digital converter 27 sends the digital signal to the digital signal processor 28, the digital signal processor 28 calculates the salinity of the seawater to be detected. The calculation of the salinity of the seawater using the microwave interfered signals output by the salinity sensor 23 can be carried out using known algorithms, for example using the same calculation method as used by the electronic spectrum analyzer to calculate the salinity value of the seawater to be detected. The digital signal processor 28 sends the calculation result to the display screen through the display interface module 29, and the user can directly view the seawater salinity value through the display screen.

Of course, it is an alternative that the display interface module is disposed on the housing of the portable terminal device, so that the display interface module and the external display device are connected by a connection line, and the seawater salinity value can be checked through the external display device. Alternatively, the filter circuit further includes a band-pass filter circuit, and only a signal with a specific frequency can pass through the band-pass filter circuit, so as to ensure that the frequency of the signal input to the analog-to-digital converter is a preset frequency, and prevent the analog-to-digital converter from receiving an interference signal.

Second embodiment:

referring to fig. 5, the salinity detecting apparatus of the present embodiment includes a wireless signal transceiver module 30, a salinity sensor 33, an optical circulator 34, a photodetector 35, a filter circuit 36, an analog-to-digital converter 37, a digital signal processor 38, and a display interface module 39. The wireless signal transceiver module 30, as an input optical signal generating module in this embodiment, includes a band-pass filter 311, a signal amplifier 312, and a direct modulation type electro-optical modulator 313, where the band-pass filter 311 can acquire a wireless radio frequency signal from the air, output the acquired wireless radio frequency signal to the signal amplifier 312, and input the wireless radio frequency signal amplified by the signal amplifier 312 to the direct modulation type electro-optical modulator 313.

In this embodiment, the band-pass filters 311 only allow the wireless signals in a specific frequency band to pass through, optionally, the number of the band-pass filters 311 may be multiple, each band-pass filter 311 corresponds to a wireless radio frequency signal in a frequency band, and the frequency band corresponding to each band-pass filter 311 is different from the frequency band corresponding to another band-pass filter 311. For example, the frequency bands corresponding to the plurality of band pass filters may be at least two of a frequency band of 2G communication wireless signals, a frequency band of 3G communication wireless signals, a frequency band of 4G communication wireless signals, and a frequency band of 5G communication wireless signals.

The direct modulation type electro-optical modulator 313 is provided with a light source to generate an optical signal, for example, the light source may be a light emitting diode, and the optical signal is generated by the light emitting diode. In addition, the optoelectronic direct modulation type electro-optical modulator 313 directly modulates the voltage or current of the light source by using the amplified radio frequency signal, and since the band-pass filter 311 receives the radio frequency signal from the air, the voltage or current of the light source can be directly modulated by the radio frequency signal to change the frequency of the output optical signal, the difficulty of the electro-optical modulation can be reduced by adopting the optoelectronic direct modulation mode.

The optical circulator 34 has three ports, a first port 341, a second port 342, and a third port 343. The output of the direct-modulated electro-optical modulator 313 is connected to the first port 341 of the optical circulator 34, and the salinity sensor 33 is connected to the second port 342 of the optical circulator 34, so that the input optical signal is incident on the salinity sensor 33 from the second port 342. The internal structure of the salinity sensor 33 is the same as that of the first embodiment and will not be described herein.

The return light signal passing through the salinity sensor 33 is output to the photoelectric detector 35 from the third port 343 of the optical circulator 34 and converted into an electrical signal, so as to obtain a measurement electrical signal, the photoelectric detector 35 outputs the measurement electrical signal to the filter circuit 36, the filter circuit 36 filters the measurement electrical signal and outputs the filtered measurement electrical signal to the mode converter 37, the analog-to-digital converter 37 converts the analog signal into a digital signal and outputs the digital signal to the digital signal processor 38, the digital signal processor 38 calculates the salinity of the seawater and outputs the salinity of the seawater to the display screen through the display interface module 39, so that a user can conveniently check the value of the salinity of the seawater in real time.

It can be seen that, unlike the first embodiment, the present embodiment uses the direct modulation type electro-optical modulator 313 to implement electro-optical modulation, and does not need to use an erbium-doped fiber amplifier, thereby reducing the production cost and volume of the seawater salinity detection apparatus.

Because the analog-to-digital converter is adopted to convert the analog signal output by the photoelectric converter into the digital signal and the digital signal processor with lower production cost and smaller volume is adopted to calculate the salinity of the seawater, an electronic spectrum analyzer with high price is not needed, thereby reducing the production cost of the seawater salinity detection device. In addition, because digital signal processor can connect the display screen through showing interface module, convenience of customers looks over the numerical value of sea water salinity in outdoor real time.

Finally, it should be emphasized that the above-described preferred embodiments of the present invention are merely examples of implementations, not limitations, and various changes and modifications may be made by those skilled in the art, without departing from the spirit and scope of the utility model, and any changes, equivalents, improvements, etc. made within the spirit and scope of the present invention are intended to be embraced therein.

Claims

1. A double-optical fiber end surface interference salinity detection device based on digital signal processing comprises:

an input optical signal generation module comprising an electro-optical modulator that modulates an optical signal with a radio frequency signal to form an input optical signal;

the optical circulator is provided with a first port, a second port and a third port, and the first port is connected with the electro-optical modulator and receives the input optical signal;

the salinity sensor is connected with the second port of the optical circulator, and a return optical signal formed by the input optical signal passing through the salinity sensor is transmitted to the third port from the second port, wherein the salinity sensor is provided with a first reflecting end face and a second reflecting end face, a single-mode optical fiber is arranged between the first reflecting end face and the second reflecting end face, and the second reflecting end face is soaked in seawater to be detected;

the photoelectric detector is connected with the third port of the optical circulator, receives the return optical signal and converts the return optical signal into a measurement electric signal;

it is characterized by also comprising:

the analog-to-digital converter is used for receiving the measuring electric signal and converting the measuring electric signal into a digital signal;

and the digital signal processor receives the digital signal output by the analog-to-digital converter.

2. The double-optical-fiber end-face interference salinity detecting device based on digital signal processing according to claim 1, characterized in that:

the digital signal processor is provided with a display interface module which is used for being connected with a display and outputting display signals to the display.

3. The double-optical-fiber end-face interference salinity detecting device based on digital signal processing according to claim 2, characterized in that:

4. The double-optical-fiber end-face interference salinity detection apparatus based on digital signal processing according to claim 2, characterized in that:

and a filter circuit is arranged between the analog-to-digital converter and the digital signal processor.

5. The digital signal processing-based dual-fiber end surface interference salinity detection apparatus according to claim 4, wherein:

the filter circuit is a band-pass filter circuit.

6. The double-optical-fiber end-face interference salinity test device based on digital signal processing according to any one of claims 1 to 5, characterized in that:

the input optical signal generation module further comprises a band-pass filter and a signal amplifier, and a wireless signal output by the band-pass filter is output to the electro-optical modulator after passing through the signal amplifier.

7. The double-optical-fiber end-face interference salinity detecting device based on digital signal processing according to claim 6, characterized in that:

the number of the band-pass filters is more than two, and the band-pass filters correspond to different frequency bands.

8. The double-optical-fiber end-face interference salinity detecting device based on digital signal processing according to claim 6, characterized in that:

the electro-optical modulator is a direct modulation electro-optical modulator.

9. The double-optical-fiber end-face interference salinity test device based on digital signal processing according to any one of claims 1 to 5, characterized in that:

the input optical signal generation module comprises an erbium-doped optical fiber amplifier and a radio frequency signal generator, wherein the erbium-doped optical fiber amplifier inputs an optical signal to the electro-optical modulator, and the radio frequency signal generator inputs a radio frequency signal to the electro-optical modulator.