WO2018191860A1

WO2018191860A1 - Method and device for manufacturing optical fiber end face thin film air pressure sensor

Info

Publication number: WO2018191860A1
Application number: PCT/CN2017/080877
Authority: WO
Inventors: 何俊; 王义平; 张哲�
Original assignee: 深圳大学
Priority date: 2017-04-18
Filing date: 2017-04-18
Publication date: 2018-10-25

Abstract

A device for manufacturing an optical fiber end face thin film air pressure sensor, comprising a light source module (10), an optical fiber coupler (20), a spectral acquisition and analysis module (60), a conductive optical fiber (30), a thin film (40), and a hot air generation module (50). An output port of the light source module (10) is connected to a first port of the optical fiber coupler (20). A second port of the optical fiber coupler (20) is connected to an input port of the conductive optical fiber (30), and a third port of the optical fiber coupler (20) is connected to an input port of the spectral acquisition and analysis module (60). The thin film (40) is located on the end face of an output port of the conductive optical fiber (30). An output port of the spectral acquisition and analysis module (60) is connected to an input port of the hot air generation module (50). The thickness of the thin film (40) is precisely controlled by means of hot air generated by the hot air generation module (50), and the manufactured optical fiber end face thin film air pressure sensor has high precision. In addition, the manufacturing method is simple and low in cost. Further provided is a method for manufacturing an optical fiber end face thin film air pressure sensor.

Description

Method for preparing optical fiber end face film type air pressure sensor and preparation device thereof

Technical field

The invention belongs to the field of optical fiber sensing, and in particular relates to a preparation method and a preparation device for a fiber end face film type air pressure sensor.

Background technique

The fiber optic sensor is compact, anti-electromagnetic interference and easy to network. It has been widely used in building structures and environmental monitoring. Fiber-optic end face film type FPI (Fabry-Perot Interferometer), Fabry-Perot interferometer) has good stability and high detection sensitivity, and is widely used in barometric pressure measurement. The fiber end face film type FPI is coated with a film on the flat fiber end face. After the irradiation light is incident on the fiber, the two beams reflected at the interface between the fiber and the film, the film and the air form an FPI.

The existing fiber end face film FPI manufacturing methods include: solution dipping method, spin coating method, ultraviolet glue curing method and the like. However, the solution dipping method and the spin coating method are complicated. The solution dipping method requires a solution to be prepared in advance, and then the flat fiber end face is immersed in the solution, and then taken out, air-dried and solidified to form an end cap. Spin coating requires special spin coating equipment and requires precise process control. The UV glue curing method requires special glue, and since the UV modulus is relatively large after curing, the UV adhesive end cap FPI pressure sensitivity reported recently is relatively low (about 1 nm/MPa).

Therefore, the prior art does not provide a fabrication method that simultaneously satisfies the high sensitivity of the device and is simple and low-cost, and needs improvement.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method and a device for preparing a fiber end face film type air pressure sensor, which aim to solve the problem that the prior art does not provide a method for simultaneously satisfying high sensitivity and simple and low cost of the device.

The invention is realized by the invention, comprising a light source module, a fiber coupler, a spectrum acquisition and analysis module, a conductive fiber, a film and a hot air generating module, wherein;

An output port of the light source module is connected to the first port of the fiber coupler for generating illumination light of a preset wavelength, and transmitting the illumination light to the fiber coupler through the output port;

a second port of the fiber coupler is coupled to an input port of the conductive fiber, and a third port of the fiber coupler is coupled to an input port of the spectral acquisition and analysis module for coupling the illumination light, and Transmitting the coupled illumination light to the conductive fiber;

An end surface of the output port of the conductive fiber is wrapped with the film, and the coupled illumination light is transmitted to the film for reflection, and the reflected light of the film is collected and sent to the fiber coupler to Transmitting the reflected light to the spectral acquisition and analysis module by the fiber coupler;

An output port of the spectral acquisition and analysis module is coupled to an input port of the hot air generating module for passing a preset film according to a wavelength of light of the reflected light and a free spectral width of the reflected light The thickness calculation formula calculates the thickness of the film, compares the thickness of the film with a preset film thickness, generates a control signal according to the comparison result, and sends the control signal to the hot air generation module;

The hot air generating module is configured to generate hot air corresponding to temperature and wind speed according to the control signal, wherein the hot air acts on the surface of the film to control the thickness of the film to a preset film thickness, and The film is attached to the end face of the output port of the conductive fiber.

Further, the preparation device further includes a fiber cutter for cutting the end surface of the output port of the conductive fiber, the fiber cutter being a mechanical fiber cutter or a femtosecond laser cutter.

Further, the light source module is a light source module that generates a broadband light source, and the broadband light source includes a stimulated spontaneous radiation light source or a super continuous light source.

Further, the fiber coupler includes at least three ports, and the fiber coupler is one of a tree fiber coupler, a star fiber coupler, or a fiber circulator.

Further, the spectral acquisition and analysis module is one of a diffraction grating spectrometer, a prism spectrometer, an interference spectrometer or a micro spectrometer.

Further, the film is a polymer film including any one of a polyvinyl chloride film, a polyethylene film, a nylon film, or a mylar film.

Further, the hot air generating module is a plastic welding torch with adjustable temperature and wind speed.

The invention also provides a preparation method of an optical fiber end face film type air pressure sensor, comprising:

Connecting the first port of the fiber coupler to the output port of the light source module, connecting the second port of the fiber coupler to the input port of the conductive fiber, and connecting the third port of the fiber coupler to the spectrum An input port of the set and analysis module, and an output port of the spectrum acquisition and analysis module is connected to an input port of the hot air generating module;

Wrap the film on the end face of the output port of the conductive fiber and adjust the film to obtain a high contrast interference spectrum;

Opening the hot air generating module, and initializing a temperature and a wind speed of the hot air generated by the hot air generating module, so that the hot air generating module generates a hot air corresponding to the temperature and the wind speed according to the control signal sent by the spectrum collecting and analyzing module. The hot air acts on the surface of the film to fix the film on the end face of the output port of the conductive fiber;

The hot air generating module is turned off to cool and solidify the film to obtain a preset fiber end face film type air pressure sensor.

Further, the initializing the temperature and the wind speed of the hot air generated by the hot air generating module includes:

The initial temperature of the hot air generated by the hot air generating module is set to a temperature matching the melting point of the material of the film, and the wind speed of the hot air generated by the hot air generating module is set to zero.

Further, before the closing the hot air generating module, the method further includes:

The spectral acquisition and analysis module calculates the thickness of the current film according to a preset film thickness calculation formula and a light wavelength of the reflected light;

Determining whether the thickness of the film is greater than a preset film thickness, and if greater, generating a control signal for increasing the wind speed to the hot air generating module, so that the hot air generating module increases the generated hot air according to the control signal. The wind speed, if equal, sends a shutdown signal to the hot air generating module;

The shutting down the hot air generating module includes:

After receiving the shutdown signal, the hot air generating module performs a closing operation.

Compared with the prior art, the present invention has the beneficial effects that the preparation device and the preparation method provided by the embodiments of the present invention can control the hot air generated by the hot air generating module according to the thickness of the film, thereby further controlling the thickness of the film and obtaining the preset. The film thickness is finally obtained as a preset fiber end face film type air pressure sensor. In the embodiment of the invention, the thickness of the film is precisely controlled by the hot air generated by the hot air generating module, and the manufactured fiber end face film type air pressure sensor has high precision, and the manufacturing method is simple and the cost is low.

DRAWINGS

1 is a schematic structural view of an optical fiber end face film type air pressure sensor according to an embodiment of the present invention;

2 is a schematic structural view of a device for preparing an optical fiber end face film type air pressure sensor according to an embodiment of the present invention;

3 is a flow chart of a method for preparing an optical fiber end face film type air pressure sensor according to an embodiment of the present invention;

4 is a physical flow chart of a method for preparing an optical fiber end face film type air pressure sensor according to an embodiment of the present invention;

5 is a reflection spectrum of an optical fiber end face film type air pressure sensor according to an embodiment of the present invention, and a fiber end face thin film microscope image corresponding to a reflection spectrum;

6a to 6d are diagrams showing the air pressure of the optical fiber end face film type air pressure sensor according to an embodiment of the present invention. The device and test results should be tested.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The fiber optic sensor is compact and sensitive, and is widely used in engineering technology. The fiber end face FPI air pressure sensor relies on making a micron-scale FP cavity on the fiber end face, so that the incident light is at the interface between the conductive fiber and the FP cavity (Fabry-perot Cavity) (interface I), FP. The cavity interface and the air interface (interface II) are reflected, and the two reflected light interfere with white light and conduct back to the conducting fiber, so that white light interference fringes appear in the reflection spectrum of the conducting fiber, as shown in FIG. When the external air pressure changes, the FP cavity material is subjected to pressure deformation, the cavity length L changes, and the interference fringes drift. By detecting the wavelength change at a certain interference maximum or minimum value, the change of the external air pressure can be calibrated. The detected light intensity can be expressed as:

Where I ₁ , I ₂ are the light intensities reflected back to the single mode fiber by interfaces I and II, respectively, λ is the wavelength of light, and n is the effective refractive index of the cavity material.

Is the initial phase difference between the two reflected lights.

Based on this, an embodiment of the present invention provides an optical fiber end face film type air pressure sensor as shown in FIG. 2, including a light source module 10, a fiber coupler 20, a spectrum acquisition and analysis module 60, a conductive fiber 30, a film 40, and hot air generation. Module 50, wherein;

The output port a1 of the light source module 10 is connected to the first port b1 of the fiber coupler 20 for generating the preset wavelength of illumination light, and the illumination light is sent to the fiber coupler 20 through the output port;

The second port b2 of the fiber coupler 20 is connected to the input port c1 of the conductive fiber 30, and the third port b3 of the fiber coupler 20 is connected to the input port d1 of the spectrum acquisition and analysis module 60 for coupling the illumination light, and Transmitting the coupled illumination light to the conductive fiber 30;

The end face of the output port c2 of the conductive fiber 30 is wrapped with a film 40 for conducting the coupled illumination light to the film 40 for reflection, and the reflected light of the collection film 40 is sent to the fiber coupler 20 for passing through the fiber coupler. 20 transmitting the reflected light to the spectral acquisition and analysis module 60;

The output port d2 of the spectral acquisition and analysis module 60 is connected to the input port e1 of the hot air generating module 50 for calculating the optical wavelength of the reflected light and the free spectral width of the reflected light by a preset film thickness calculation formula. The thickness of the film is compared with the thickness of the film, and a control signal is generated based on the comparison result and sent to the hot air generation module 50. Specifically, the spectrum generation module 60 has a built-in film thickness calculation formula:

And a preset film thickness L ₀ , and importing a logic operation, if the L>L ₀ , increasing the wind speed; if L=L ₀ , stopping the blowing;

a hot air generating module 50, configured to generate hot air corresponding to temperature and wind speed according to the control signal, the hot air acting on the surface of the film to control the thickness of the film to a preset film thickness, and The film is fixed to the end face of the output port c2 of the conductive fiber 30. Specifically, the hot air generating module 50 is initialized before the preparation is performed, and the initialization process is: the hot air generating module 50 is produced. The initial temperature of the raw hot air is set to a temperature matching the melting point of the material of the film, and the wind speed of the hot air generated by the hot air generating module is set to 0, that is, the initial hot air temperature generated by the hot air generating module 50 is based on different films. The melting point of the material is set so that it is suitable for many types of films.

Further, in order to ensure that the end surface of the output port c2 of the conductive fiber 30 enclosing the film 40 is cut and flat, the preparation device provided by the embodiment of the present invention further includes a fiber cutter that acts on the output port c2 of the conductive fiber 30. To obtain a flat conductive fiber end face. Wherein, the fiber cutter can be a mechanical fiber cutter, a femtosecond laser cutter, and the like.

Specifically, the light source module 10 is a light source module that generates a broadband light source, and the broadband light source includes a stimulated spontaneous radiation light source or a super continuous light source. The fiber coupler 20 includes at least three ports, and the fiber coupler 20 may be one of a tree fiber coupler, a star fiber coupler, or a fiber circulator. The spectral acquisition and analysis module 60 can be one of a diffraction grating spectrometer, a prism spectrometer, an interference spectrometer, or a micro spectrometer. The film 40 is a polymer film including any one of a polyvinyl chloride (PVC) film, a polyethylene (PE) film, a nylon film (PA), or a polyester film (PET). The hot air generating module 50 can generate an air flow with adjustable temperature and wind speed, and can be a plastic welding torch with adjustable temperature and wind speed. Plastic torch with adjustable temperature and wind speed. The conductive fiber 30 can be any of a conventional single mode fiber, a photonic crystal fiber, or other specialty fiber.

Specifically, the spectral acquisition and analysis module 60 can calculate the thickness of the thin film 40 according to the free spectral range of the spectrum of the reflected light (FSR: Free Spectrum Range), and generate a feedback signal, which is transmitted to the hot air generating module 50 to control the hot air. The generating module 50 generates hot air corresponding to the wind speed, Further, the effect of controlling the thickness of the film 40 is achieved. The thickness of film 40 can be expressed as a function of FSR:

Where λ is the wavelength of light, n is the optically effective refractive index of the film, and L is the thickness of film 40.

The hot air generating module 50 is controlled by the feedback signal generated by the spectrum generating module 60. When the thickness of the film 40 detected by the spectrum generating module 60 is greater than the predetermined film thickness, the wind speed of the hot air generating module 50 is automatically increased, and the thickness of the film 40 is increased. The thickness of the film 40 is then reduced and then reciprocated until the thickness of the film 40 reaches a predetermined film thickness.

FIG. 3 is a diagram of a method for fabricating an optical fiber end face film type air pressure sensor according to an embodiment of the present invention, comprising:

S301. Connect a first port of the fiber coupler to an output port of the light source module, connect a second port of the fiber coupler to an input port of the conductive fiber, and connect a third port of the fiber coupler to a spectrum acquisition and analysis module. The input port connects the output port of the spectral acquisition and analysis module to the input port of the hot air generation module.

S302, wrapping a film on an end surface of the output port of the conductive fiber, and adjusting the film to obtain a high contrast interference spectrum. Specifically, prior to this step, in order to ensure that the port of the output port of the conductive fiber can be flattened to ensure the reflection intensity, it is necessary to use a fiber cutter to cut the end face of the conductive fiber. In practical applications, the interference spectrum is observed for manual adjustment, and the purpose is to make the contrast of the interference fringe high, and the adjustment method is to manually adjust the film. The interference spectrum obtained in this step is to trace the drift of the interference spectrum to demodulate the external air pressure value. In this embodiment, a contrast greater than 10 dB is called For high contrast.

S303, the hot air generating module is turned on, and a temperature and a wind speed of the hot air generated by the hot air generating module are initialized, so that the hot air generating module generates a hot air corresponding to the temperature and the wind speed according to the control signal sent by the spectrum collecting and analyzing module. The hot air acts on the surface of the film to secure the film to the end face of the output port of the conductive fiber.

S304, the hot air generating module is turned off to cool and solidify the film to obtain a preset fiber end face film type air pressure sensor.

The embodiments provided by the present invention are further explained below with reference to FIGS. 4 to 6:

In the embodiment of the present invention, a PVC (polyvinyl chloride) plastic wrap film is selected as a film for forming an FP cavity, a common single mode fiber is used as a conductive fiber, and a mechanical fiber cutter is used as a fiber cutting device. A low-bias full-broadband mobile phone self-radiating light source (ASE, Amplified Spontaneous Emission) is used as a light source module, an optical spectrometer (OSA) and manual operation are used as a spectrum generating module, and an adjustable hot air plastic welding torch is used as a hot air generating module. First, the first port b1 of the fiber coupler is connected to the output port a1 of the light source module, the second port b2 of the fiber coupler is connected to the input port c1 of the ordinary single mode fiber, and the third port b3 is connected to the input port d1 of the spectrometer. Connect the spectrometer output port d2 to the input port e1 of the hot air plastic torch. FIG. 4 shows the physical connection provided by the embodiment, wherein the light emitted by the light source is transmitted through the single mode fiber and reflected on the end face of the single mode fiber, and the reflected light is input to the spectrometer through the 3 dB fiber coupler.

Secondly, the end face of the single-mode fiber is cut flat using a mechanical fiber cutter. At this time, the intensity of the reflected signal on the spectrometer can be observed to be enhanced, because the interface reflection is enhanced after the fiber end face is flattened, and The reflected light is more easily coupled into the conducting fiber and transmitted to the spectrometer, but there is no periodic intensity distribution because only one interface of the reflected light is conducted into the spectrometer.

Then, take a piece of PVC cling film and wrap the PVC wrap film on the end face c2 of the flattened single-mode fiber. The PVC wrap film covering the end face of the single-mode fiber was manually adjusted while observing the reflection spectrum. When the reflection spectrum exhibits a periodic interference spectrum with a high contrast ratio, the position of the fixed wrap film does not move. The hot air plastic welding torch is turned on, the tuyere is facing the end face of the fiber, and the temperature is adjusted to melt the PVC cling film. The thickness of the wrapped film on the end face of the single-mode fiber is calculated according to the interference spectrum FSR observed on the spectrometer. If the thickness of the film is larger than the thickness of the predetermined fiber end face film, the wind speed of the hot-air plastic welding torch is increased. It is known that when the thickness of the film calculated by the reflectance spectrum of the spectrometer reaches a predetermined thickness, the hot air plastic torch is turned off. The PVC cling film is gradually cooled and solidified on the end face of the fiber to form a stable FPI.

Fig. 5 shows four different film thickness air pressure sensors of the fiber end face fabricated by the above method, and corresponding reflection spectra. It can be seen that the FPI spectrum of the fiber end face film prepared by this method has high contrast and the film thickness can be controlled.

In this embodiment, one of the samples in FIG. 5 is selected for testing the performance of the sensor. Figure 6(a) shows a manual commercial gas generating device with a high precision digital barometric pressure meter built into the air chamber. The fiber optic sensor is sealed in the air chamber using AB curing glue. When the AB glue is completely cured and the air chamber is completely sealed, the air pressure test is performed, and the whole test is performed at room temperature (25 ° C). Manually pressurize the air chamber. When the air pressure reaches the set value, use the air pressure fine adjustment knob to adjust the air pressure to the set value. The boost interval is 10KPa. After the air pressure reaches the set value, keep the air pressure constant for 5 minutes, after ten minutes. After the spectrum is stabilized, spectral data is acquired. Figure 6b shows the drift of the wavelength with an air pressure at an interference minimum near 1565 nm. It can be seen that as the gas pressure rises from 0 to 60 KPa, the spectrum drifts toward the short-wave direction. In order to verify the recovery of the fiber sensor, after the pressure is applied to 60 KPa, the same method is used for depressurization, and the spectrum is drifted in the long-wave direction as the pressure is lowered, as shown in Fig. 6c. By tracking the wavelength drift around 1565 nm and using linear fitting data processing, the high sensitivity of the fiber-optic sensor device is -66.07 nm/M Pa, as shown in Fig. 6d. So far, the present embodiment has verified the simplicity and reliability of the proposed fiber end face film type air pressure sensor manufacturing apparatus and method.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

The device for preparing a fiber end face film type air pressure sensor, wherein the preparation device comprises a light source module, a fiber coupler, a spectrum acquisition and analysis module, a conductive fiber, a film and a hot air generating module, wherein;

An output port of the light source module is connected to the first port of the fiber coupler for generating illumination light of a preset wavelength, and transmitting the illumination light to the fiber coupler through the output port;

a second port of the fiber coupler is coupled to an input port of the conductive fiber, and a third port of the fiber coupler is coupled to an input port of the spectral acquisition and analysis module for coupling the illumination light, and Transmitting the coupled illumination light to the conductive fiber;

An end surface of the output port of the conductive fiber is wrapped with the film, and the coupled illumination light is transmitted to the film for reflection, and the reflected light of the film is collected and sent to the fiber coupler to Transmitting the reflected light to the spectral acquisition and analysis module by the fiber coupler;

An output port of the spectral acquisition and analysis module is connected to an input port of the hot air generating module, and is configured to calculate, according to a wavelength of the reflected light and a free spectral width of the reflected light, by using a preset film thickness calculation formula The thickness of the film is compared with the thickness of the film, and a control signal is generated according to the comparison result and sent to the hot air generating module;

The hot air generating module is configured to generate hot air corresponding to temperature and wind speed according to the control signal, wherein the hot air acts on the surface of the film to control the thickness of the film to a preset film thickness, and The film is attached to the end face of the output port of the conductive fiber.
The preparation apparatus according to claim 1, wherein said preparation apparatus further comprises a fiber cutter for cutting an end surface of said output port of said conductive fiber, said fiber cutter being a mechanical fiber cutter Or femtosecond laser cutting knives.
The preparation apparatus according to claim 1, wherein the light source module is a light source module that generates a broadband light source, and the broadband light source comprises a stimulated spontaneous radiation light source or a supercontinuum light source.
The preparation apparatus according to claim 1, wherein said fiber coupler comprises at least three ports, and said fiber coupler is one of a tree fiber coupler, a star fiber coupler or a fiber circulator. .
The preparation apparatus according to claim 1, wherein the spectral acquisition and analysis module is one of a diffraction grating spectrometer, a prism spectrometer, an interference spectrometer, or a micro spectrometer.
The preparation apparatus according to claim 1, wherein the film is a polymer film including any one of a polyvinyl chloride film, a polyethylene film, a nylon film, or a mylar film.
The preparation apparatus according to claim 1, wherein said hot air generating module is a plastic welding torch whose temperature and wind speed are adjustable.
A method for preparing a fiber end face film type air pressure sensor, comprising:

Connecting the first port of the fiber coupler to the output port of the light source module, connecting the second port of the fiber coupler to the input port of the conductive fiber, and connecting the third port of the fiber coupler to the input of the spectrum acquisition and analysis module a port, connecting an output port of the spectrum acquisition and analysis module to an input port of the hot air generation module;

Wrap the film on the end face of the output port of the conductive fiber and adjust the film to obtain a high contrast interference spectrum;

Opening the hot air generating module, and initializing a temperature and a wind speed of the hot air generated by the hot air generating module, so that the hot air generating module generates a hot air corresponding to the temperature and the wind speed according to the control signal sent by the spectrum collecting and analyzing module. The hot air acts on the surface of the film to fix the film on the end face of the output port of the conductive fiber;

The hot air generating module is turned off to cool and solidify the film to obtain a preset fiber end face film type air pressure sensor.
The preparation method according to claim 8, wherein the initializing the temperature and the wind speed of the hot air generated by the hot air generating module comprises:

The initial temperature of the hot air generated by the hot air generating module is set to a temperature matching the melting point of the material of the film, and the wind speed of the hot air generated by the hot air generating module is set to zero.
The method of claim 8, wherein before the closing of the hot air generating module, the method further comprises:

The spectral acquisition and analysis module calculates the thickness of the current film according to a preset film thickness calculation formula and a light wavelength of the reflected light;

Determining whether the thickness of the film is greater than a preset film thickness, and if greater, generating a control signal for increasing the wind speed to the hot air generating module, so that the hot air generating module increases the generated hot air according to the control signal. The wind speed, if equal, sends a shutdown signal to the hot air generating module;

The shutting down the hot air generating module includes:

After receiving the shutdown signal, the hot air generating module performs a closing operation.