CN115200618A - All-optical phase modulation system based on gas photothermal effect in micro-nano optical fiber - Google Patents

Abstract

The invention discloses an all-optical phase modulation system based on gas photothermal effect in a micro-nano optical fiber, which comprises a signal light source for generating signal light, a first coupler connected with the signal light source, and a first coupler for respectively outputting the signal light from a first output end and a second output end; the phase modulator comprises a pumping light source and an optical fiber air chamber, wherein the pumping light source is used for emitting control light; the optical fiber gas chamber comprises a sealed inner cavity and a micro-nano optical fiber positioned in the sealed inner cavity, the outer part of the micro-nano optical fiber is filled with absorptive gas, the micro-nano optical fiber receives control light and signal light, and the temperature and the refractive index of the absorptive gas are changed by the control light to cause the phase change of the signal light; the input end of the matching arm component is connected with the second output end; the first input end is connected with the second coupler of the phase modulator, and the second input end is connected with the output end of the matching arm component; and the detection component is connected with the output end of the second coupler. Has the advantages of small scattering loss, uniform heat generation and simple preparation process.

Description

All-optical phase modulation system based on gas photothermal effect in micro-nano fiber

technical field

The invention relates to the technical field of optical phase modulation, in particular to an all-optical phase modulation system based on the photothermal effect of gas in micro-nano optical fibers.

Background technique

Optical phase modulators are important devices in the field of optical fiber communication and sensing. Traditional optical phase modulators are mostly based on the principle of electro-optic effect of crystal materials. The heterogeneity between the quartz fiber and the crystal material makes the traditional optical phase modulator have large insertion loss, low integration, large packaging volume and complex process.

The solid-state thermosensitive materials commonly used in existing phase modulators, such as graphene, transition metal chalcogenides, and black phosphorus, have the disadvantages of large scattering loss, low light damage threshold, and complex fabrication processes.

Therefore, the existing technology still needs to be improved and developed.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide an all-optical phase modulation system based on the photothermal effect of gas in the micro-nano optical fiber, based on the photothermal effect of the gas in the evanescent field of the micro-nano optical fiber, with small scattering loss, high production The advantages of thermal uniformity and simple preparation process.

The technical scheme of the present invention is as follows:

An all-optical phase modulation system based on gas photothermal effect in micro-nano optical fiber, comprising:

Signal light source, the signal light source is used to generate signal light;

a first coupler, the first coupler is connected to the signal light source, and outputs the signal light from the first output end and the second output end respectively;

a phase modulator, the phase modulator is connected to the first output end, the phase modulator includes a pump light source, and an optical fiber air chamber, the pump light source is used to emit control light; the optical fiber air chamber includes a sealed inner cavity, and is located in the sealed inner cavity The outside of the micro-nano fiber is filled with absorbing gas, the micro-nano fiber receives the control light and the signal light, and changes the temperature and refractive index of the absorbing gas by the control light to cause the phase change of the signal light;

a matching arm assembly, the input end of the matching arm assembly is connected to the second output end;

a second coupler, the first input end of the second coupler is connected to the phase modulator, and the second input end is connected to the output end of the matching arm assembly;

The detection component is connected to the output end of the second coupler.

Further, the matching arm assembly includes: a piezoelectric fiber stretcher, and the piezoelectric fiber stretcher is connected to the second output end;

The polarization controller is connected to the light output end of the piezoelectric fiber stretcher, and is connected to the second coupler.

Further, the matching arm assembly further includes: a servo controller, the servo controller is connected to the detection assembly and the piezoelectric fiber stretcher, and the piezoelectric fiber stretcher is driven by the servo controller to lock the output signal at the maximum slope point.

Further, the phase modulator also includes:

a wavelength division multiplexer, the first light input end of the wavelength division multiplexer is arranged at the light output end of the pump light source and is used for inputting control light, and the second light input end is used for inputting signal light; and

Fiber Bragg Grating, the fiber Bragg grating is arranged at the light output end of the optical fiber air chamber, and is used to output the signal light and reflect the control light;

The micro-nano fiber includes: a fiber tail region and a tapered region; the fiber tail region is located at both ends of the tapered region.

Further, the micro-nano fiber is made of single-mode fiber taper;

The diameter of the cone is 0.1-10 microns, and the length of the cone is 0.1-10 cm.

Further, the pump light source and the wavelength division multiplexer are connected by an optical fiber.

Further, the pump light source includes: a pump light laser, and the pump light laser is used to emit control light;

Amplifier, the amplifier is arranged at the light output end of the pump laser, and is used to amplify the control light;

The acousto-optic modulator is arranged at the light output end of the amplifier and is used to modulate the intensity of the control light.

Further, a circulator is arranged between the pump light source and the wavelength division multiplexer.

Further, the reflection bandwidth of the fiber Bragg grating is 0.1-10 nanometers, the center wavelength corresponds to the wavelength of the control light, and the reflectivity is 99%.

Further, the absorbing gas includes: acetylene, methane or/and carbon dioxide.

Beneficial effects: Compared with the prior art, the present invention proposes an all-optical phase modulation system based on the photothermal effect of gas in micro-nano optical fibers, wherein the control light is generated by the pump light source, the signal light is generated by the signal light source, and the signal light passes through The first coupler is divided into two paths, one of which jointly inputs the control light and the pump light into the optical fiber gas chamber in the phase modulator, and controls the absorbing gas in the evanescent field and mode field of the micro-nano fiber. The thermo-optic effect produced by the interaction causes the temperature of the absorptive gas and the micro-nano fiber to increase. Phase; the other signal light is adjusted by the matching arm assembly through the matching arm assembly, and after passing through the second coupler, the two signal lights are jointly input to the detection assembly, and the two signal lights generate interference light when they are combined, resulting in interference fringes. , when the phase difference of the transmitted light in the two fibers changes, which causes the movement of the interference fringes. The light detection component receives the change information of the interference fringes, and inputs it into the appropriate data processing system, and finally obtains the phase modulation of the signal light. Compared with the existing modulator, it has the advantages of higher mode field energy density, small scattering loss and simple preparation process.

Description of drawings

1 is a structural principle block diagram of an embodiment of an all-optical phase modulation system based on gas photothermal effect in a micro-nano fiber of the present invention;

2 is a structural principle block diagram of a phase modulator according to an embodiment of an all-optical phase modulation system based on gas photothermal effect in a micro-nano fiber of the present invention;

3 is a schematic cross-sectional view of a micro-nano fiber according to an embodiment of an all-optical phase modulation system based on gas photothermal effect in a micro-nano fiber of the present invention;

4 is an evanescent field distribution diagram of a micro-nano fiber according to an embodiment of an all-optical phase modulation system based on gas photothermal effect in a micro-nano fiber of the present invention;

5 is a phase modulation time domain signal diagram of an embodiment of an embodiment of an all-optical phase modulation system based on gas photothermal effect in a micro-nano optical fiber according to the present invention;

6 is a control optical power response curve of an embodiment of an all-optical phase modulation system based on gas photothermal effect in a micro-nano fiber of the present invention;

7 is a modulation frequency response curve of an embodiment of an all-optical phase modulation system based on the photothermal effect of gas in a micro-nano fiber of the present invention.

Labels in the figure: 10, phase modulator; 110, pump light source; 111, pump laser; 112, amplifier; 113, acousto-optic modulator; 120, wavelength division multiplexer; 130, optical fiber air chamber; 131 , sealed cavity; 132, micro-nano fiber; 133, fiber tail region; 134, cone region; 135, evanescent field; 140, fiber Bragg grating; 150, circulator; 20, signal light source; 30, first coupler 40, matching arm assembly; 410, piezoelectric fiber stretcher; 420, polarization controller; 430, servo controller; 50, second coupler; 60, detection assembly; 610, photodetector; 620, oscilloscope.

Detailed ways

The present invention provides an all-optical phase modulation system based on gas photothermal effect in a micro-nano fiber. In order to make the purpose, technical scheme and effect of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

There are many schemes for modulating the signal light. The principle is to use the heat-sensitive material to absorb the evanescent field of the control light to generate heat, thereby causing a change in the refractive index of the waveguide and modulating the phase of the signal light in the waveguide. However, limited by the intrinsic absorption of heat-sensitive materials and the scattering effect caused by imperfect coating, the insertion loss is as high as 10dB, and the optical band is narrow; limited by the slow heat dissipation of the air, the modulation bandwidth is usually lower than 100Hz. Moreover, the preparation of heat-sensitive materials is complicated due to the need for post-treatment of waveguides and material coating, and the long-term reliability is difficult to meet practical needs. In order to solve the limitation of thermosensitive materials, all-optical phase modulation technology can be used to improve. Therefore, this embodiment proposes an all-optical phase modulation system based on gas photothermal effect in micro-nano fibers to improve the above problems.

The specific structure of this embodiment is as follows:

As shown in FIG. 1 , this embodiment proposes an all-optical phase modulation system based on the photothermal effect of gas in a micro-nano fiber, and modulates the signal light by controlling the photothermal effect generated by the light and the adsorbed gas. The all-optical phase modulation system includes: a signal light source 20 , a first coupler 30 , a phase modulator 10 , a matching arm assembly 40 , a second coupler 50 , and a detection assembly 60 . The signal light source 20 is used to generate signal light, and the first coupler 30 is connected to the signal light source 20, and outputs the signal light from the first output end and the second output end of the first coupler 30 respectively; the phase modulator 10 is connected to the first output end and the second output end of the first coupler 30. At the output end, the phase modulator 10 includes a pump light source 110 and an optical fiber air chamber 130. The pump light source 110 is used to emit control light; the optical fiber air chamber 130 includes a sealed cavity 131 and a micro-nano optical fiber located in the sealed cavity 131 132, the outside of the micro-nano fiber 132 is filled with absorbing gas, the micro-nano fiber 132 receives the control light and the signal light, and changes the temperature and refractive index of the absorbing gas by the control light to cause the phase change of the signal light; the matching arm assembly 40 The input end is connected to the second output end of the first coupler 30; the first input end of the second coupler 50 is connected to the phase modulator 10, and the second input end is connected to the output end of the matching arm assembly 40; the detection assembly 60 is connected to the first The outputs of the two couplers 50 . The control light is generated by the pump light source 110 , the signal light is generated by the signal light source 20 , and the signal light is divided into two paths by the first coupler 30 , and one path of the signal light and the control light are jointly input to the optical fiber air chamber in the phase modulator 10 In 130, the thermo-optic effect produced by the interaction between the evanescent field 135 of the micro-nano fiber 132 and the absorbing gas in the mode field range is controlled, and the temperature of the absorbing gas and the micro-nano fiber 132 is increased, and the temperature is increased. The change causes the refractive index of the micro-nano fiber 132 to change through the thermo-optic effect, thereby changing the phase of the signal light transmitted along the micro-nano fiber 132; the other signal light is adjusted by the matching arm assembly 40, and after passing through the second coupler 50, the two paths are adjusted. The signal light is jointly input to the detection component 60. When the two signal lights are combined, interference light is generated, and interference fringes appear. When the phase difference of the transmitted light in the two fibers changes, the interference fringes move. The light detection component 60 receives the change information of the interference fringes, and inputs it to an appropriate data processing system, and finally obtains the phase modulation of the signal light.

As shown in FIG. 1 and FIG. 2 , the specific structure of the phase modulator 10 in this embodiment further includes: a wavelength division multiplexer 120 and a fiber Bragg grating 140 . The pump light source 110 in this embodiment is used to emit control light, and the control light is incident on the wavelength division multiplexer 120; the wavelength division multiplexer 120 has a first light input end and a second light input end, and an output light Common end; the first light input end of the wavelength division multiplexer 120 is arranged at the light output end of the pump light source 110 and is used for inputting control light, and the second light input end is used for inputting the signal light to be modulated, and the signal light is the first light input. The first signal light split by a coupler can be combined with the control light and the signal light by the wavelength division multiplexer 120 . The optical fiber air chamber 130 is connected to the common end of the wavelength division multiplexer 120, and the combined control light and signal light are output from the wavelength division multiplexer 120; the temperature and refraction of the absorbing gas are changed in the optical fiber air chamber 130 by the control light rate to cause the phase change of the signal light. The fiber Bragg grating 140 is disposed at the light-emitting end of the fiber air chamber 130, and the control light and signal light output from the fiber air chamber 130 enter the fiber Bragg grating 140, and the fiber Bragg grating 140 is used for outputting the signal light and reflecting the control light, thereby obtaining modulation. The resulting signal light, and the control light reflected by the fiber Bragg grating 140 enters the fiber air chamber 130 from the other end of the micro-nano fiber 132, and continues to act on the absorbing gas to generate a photothermal effect, which makes the optical fiber air chamber 130 Both ends can perform photothermal effect, and the photothermal effect in the transmission direction of the micro-nano fiber 132 is mild.

In this embodiment, the control light is generated by the pump light source 110 , and then the control light and the pump light are jointly input into the optical fiber air chamber 130 through the wavelength division multiplexer 120 . The thermo-optic effect produced by the interaction of the absorbing gas in the mode field range causes the temperature of the absorbing gas and the micro-nano fiber 132 to increase. The temperature change causes the refractive index of the micro-nano fiber 132 to change through the thermo-optic effect, and then Change the phase of the signal light transmitted along the micro-nano fiber 132 to realize the phase modulation of the signal light. This scheme uses the gas photothermal effect based on the micro-nano fiber 132 to realize the phase modulation of the signal light, compared with the existing modulator. It has a higher mode field energy density; the control light reflected by the fiber Bragg grating 140 enters the fiber air chamber 130 from the other end of the micro-nano fiber 132, and continues to act on the absorbing gas to generate a photothermal effect, which makes the fiber air chamber 130. Both ends of 130 can perform photothermal effect, and uniform heat generation can be achieved at both ends in the transmission direction of micro-nano fiber 132, and the photothermal effect of gas is different from existing solid photothermal materials, and gas molecules are only in discrete There is strong absorption at the narrow absorption line, and almost no absorption at the wavelength of the signal light outside the absorption line, which avoids the problem of intrinsic absorption of the material and the scattering effect caused by imperfect coating, and reduces the scattering loss; The wavelength division multiplexer 120, the optical fiber air chamber 130, and the fiber Bragg grating 140 are integratedly arranged, the integration degree is high, and the preparation process is simple; it can be widely used in the fields of optical fiber communication and optical fiber sensing.

As shown in FIGS. 3 and 4 , the micro-nano fiber 132 in this embodiment specifically includes a fiber tail region 133 and a tapered region 134 ; the fiber tail region 133 is located at both ends of the tapered region 134 . The fiber tail region 133 serves as the region where light enters and leaves the optical fiber, and the tapered region 134 serves as the main functional region of the micro-nano fiber 132, which has the characteristics of small diameter, and its evanescent field 135 is relatively strong, which is convenient for generating photothermal effect with absorbing gas; The zone 134 is located in the middle of the sealed inner cavity 131, so that the evanescent field can be evenly distributed in the sealed inner cavity 131, and the absorbing gas can evenly act. By adjusting the dispersion of the micro-nano fiber 132, the power threshold of the control light can be reduced, and the nonlinear interaction length can be reduced; In this embodiment, the evanescent field excited by the control light transmitted in the micro-nano fiber 132 outside the fiber is used to generate the interaction between the light and the absorbing gas, which has higher mode field energy than other fiber modulators density. The micro-nano fiber 132 in this embodiment is made of a single-mode fiber taper, the diameter of the tapered region 134 is 0.1-10 microns, and the length of the tapered region 134 is 0.1-10 cm. In the micro-nano fiber 132, depending on the diameter of the tapered region 134, different percentages of the light field will propagate in the form of evanescent waves outside the fiber, and this part of the evanescent field will react with the absorbing gas, such as the tapered region When the diameter of 134 is 0.2 microns, the evanescent field outside the fiber accounts for 80%. This facilitates rapid action with the absorbing gas. The use of the micro-nano fiber 132 in the above form has extremely low coupling loss from the fiber to the device and then to the fiber, a waveguide surface with extremely low roughness, a strong confinement light field with a high refractive index difference, a large percentage of evanescent field, extremely Light mass and flexible dispersion characteristics.

In this embodiment, the pump light source 110 and the wavelength division multiplexer 120 are connected by an optical fiber, so that the control light is directly conducted through the optical fiber to the optical fiber air chamber 130 for reaction, which has the advantages of small transmission loss, and can connect the pump light source The 110 is disposed far from the optical fiber air chamber 130, and the phase of the signal light transmitted along the micro-nano optical fiber 132 is controlled by remote injection control light, which has the advantages of small size, anti-electromagnetic interference and high temperature resistance.

In this embodiment, both ends of the micro-nano optical fiber 132 can be directly welded through the optical fiber link, so that the wavelength division multiplexer 120 and the optical fiber air chamber 130 are connected by optical fibers, and the fiber Bragg grating 140 and the optical fiber air chamber 130 are connected by optical fibers. The optical fiber is connected between the two, which is conducive to the stable transmission of control light and signal light, has extremely low coupling loss, and also has the advantages of mild light absorption, uniform heat generation, and small scattering loss. The structure has the advantages of easy low insertion loss coupling with the optical fiber link and strong anti-electromagnetic interference capability.

As shown in FIG. 2 , the pump light source 110 in this embodiment includes: a pump laser 111 , an amplifier 112 , and an acousto-optic modulator 113 . The pump laser 111 is used for emitting control light, and the wavelength of the control light generated by the pump light source 110 corresponds to any absorption line of the absorbing gas (acetylene gas). In this embodiment, the control laser can generate a single-frequency control light with a wavelength of 1532.83 nm, which corresponds to the P13 absorption line of acetylene gas. The amplifier 112 is a fiber amplifier 112, which is arranged at the light output end of the pump laser 111 and used to amplify the control light; the acousto-optic modulator 113 is arranged at the light output end of the amplifier 112, and is used to modulate the intensity of the control light. The power of the control light is amplified by the fiber amplifier 112, and then modulated by the acousto-optic modulator 113. In this embodiment, the acousto-optic modulator 113 can adjust the control light by sine wave modulation, triangular wave modulation, sawtooth wave modulation, Pulse modulation, etc. The modulated control light and signal light are then output to the optical fiber air chamber 130 , where the signal light is modulated by the photothermal effect of the absorbing gas in the optical fiber air chamber 130 .

In this embodiment, a circulator 150 is disposed between the pump light source 110 and the wavelength division multiplexer 120 , specifically, a circulator 150 is disposed between the acousto-optic modulator 113 and the wavelength division multiplexer 120 . The control light can be transmitted unidirectionally in the circulator 150 through the circulator 150 . After the control light reflected by the fiber Bragg grating 140 is emitted from the fiber air chamber 130 , the remaining control light passes through the wavelength division multiplexer 120 . The common terminal and the first light input terminal are reversely returned to the circulator 150 , and then output from another port of the circulator 150 .

The reflection bandwidth of the fiber Bragg grating 140 in this embodiment is 0.1-10 nanometers, the center wavelength corresponds to the wavelength of the control light, the reflectance is 99%, and the reflectance is close to 100%. The signal light is output after passing through the fiber Bragg grating 140, and the control light is reflected back to the micro-nano fiber 132 to be absorbed again, so that the control light enters the other end of the micro-nano fiber 132 to generate a photothermal effect, and the temperature is changed from both ends. , to enhance the phase modulation amplitude.

The sealed inner cavity 131 in this embodiment is also filled with buffer gas. The buffer gas includes: nitrogen or/and argon and other inert gases, the buffer gas can play a more stable role in controlling the transmission of light and signal light, and the volume fraction of absorbing gas in the mixed gas is not less than 1%.

Absorbent gases in this scheme include: acetylene, methane or/and carbon dioxide. In this embodiment, the absorbing gas can be acetylene gas. The acetylene gas has an excellent photothermal coefficient. The acetylene gas in the airtight chamber can efficiently absorb the energy of the evanescent field and generate heat. The heated micro-nano fiber 132 passes through the heat. The optical effect produces phase modulation on the signal light.

As shown in FIG. 1 , another signal light branched by the first coupler 30 enters the matching arm assembly 40. The matching arm assembly 40 in this embodiment specifically includes: a piezoelectric fiber stretcher 410, and a polarization controller 420. The piezoelectric fiber stretcher 410 is connected to the second output end, the polarization controller 420 is connected to the light output end of the piezoelectric fiber stretcher 410, and is connected to the second coupler 50, through which the piezoelectric fiber stretcher 410 can Adjusting the fiber length of this path is used to adjust the polarization of the signal light in the matching arm assembly 40 through the polarization controller 420. When the one signal light modulated from the phase modulator 10 intersects with the second signal light in the matching arm assembly 40 to obtain the maximum interference signal.

As shown in FIG. 1 , the matching arm assembly 40 in this embodiment further includes a servo controller 430, the servo controller 430 is connected to the detection assembly 60 and the piezoelectric fiber stretcher 410, and the piezoelectric fiber stretcher 410 passes through the servo controller 430 to lock the output signal of the interferometer at the point of maximum slope. This facilitates the collection and processing of the interference signal by the detection component 60 . Because environmental noise can easily make the operating point of the system drift, a slight vibration such as people walking nearby may cause the operating point to drift for dozens or hundreds of cycles, so it is necessary to lock the operating point to keep it at the maximum slope point. The locking method depends on the servo controller 430 and the piezoelectric fiber stretcher 410. During locking, the photodetector 610 inputs the detected optical signal to the servo controller 430, and the signal received by the servo controller 430 includes the work If the point drifts due to noise, the servo controller 430 extracts the noise intensity signal through filtering, generates an electrical signal corresponding to the noise signal through a proportional-integral algorithm, and inputs the electrical signal to the piezoelectric fiber stretcher 410 . The piezoelectric fiber stretcher 410 changes the arm length of the optical fiber, so that the working point can be adjusted in real time according to the noise signal, so that the working point drift introduced by the piezoelectric fiber stretcher 410 can be offset with the noise-induced working point drift, so that the The operating point can be stabilized at the point of maximum slope.

As shown in FIG. 1 , the detection assembly 60 in this embodiment includes a photodetector 610 and an oscilloscope 620 . The photodetector 610 receives the change information of the interference fringes of the modulated signal light, and inputs it to the oscilloscope 620 for data processing and display, thereby obtaining a measurement result.

Figure 5 shows the output signal of the all-optical phase modulation system when the control optical power is 61mW and the modulation frequency is 1kHz. The wavelength of the signal light is 1550 nm. It can be seen that at this time, the phase modulation amplitude of the all-optical phase modulation system to the signal light is 2π. In addition, the experiments confirmed the proportional relationship between the control optical power and the photothermal phase modulation amplitude, and the results are shown in Fig. 6. In the experiment, the modulation frequency of the control light was 1 kHz. In addition, the phase modulation amplitude and frequency response of the phase modulator to different wavelengths in the C+L band, namely 1529, 1550, 1590 and 1625nm, are demonstrated. The results are shown in Figure 7, where the control optical power is 148mW , as the modulation frequency of the control light decreases, the amplitude of the phase modulation of the signal light by the modulator increases.

To sum up, an all-optical phase modulation system based on the photothermal effect of gas in a micro-nano fiber proposed in this solution generates modulated control light through the pump light source 110 of the phase modulator 10, and generates signal light through the signal light source. , the signal light is divided into two paths by the first coupler, one of which is the signal light and the control light through the wavelength division multiplexer 120 to combine the control light and the signal light to be modulated, and then the two beams of light are passed through the wavelength division multiplexer. The common end of 120 is input to the micro-nano fiber 132 in the fiber air chamber 130 . Since the evanescent field energy is distributed outside the micro-nano fiber 132, a sealed cavity 131 with good air tightness is used to encapsulate the micro-nano fiber 132 in an environment filled with a fixed concentration of acetylene and buffer gas. The optical fiber air chamber 130 can protect the micro-nano optical fiber 132 from mechanical damage that may be encountered in use, and at the same time prevent dust or air in the external environment from participating in the interaction between the evanescent field in the micro-nano optical fiber 132 and the external environment, The heat generation efficiency and the refractive index change rate of the absorbing gas in the photothermal effect are fixed. The control light and the signal light are input by the pigtail of the micro-nano fiber 132. At the tapered region 134 of the micro-nano fiber 132, the control light is absorbed by the absorbing gas (acetylene gas) through its evanescent field, and the micro-nano is heated by the photothermal effect. Optical fiber 132 . The energy distribution of the micro-nano fiber 132 and the evanescent field of the control light transmitted along the micro-nano fiber 132 is shown in FIG. 3 . The waveguide structure of the micro-nano fiber 132 allows the energy originally transmitted inside the fiber to leak to the outside of the fiber to form an evanescent field. The field does not propagate along the fiber, and the energy density leaking outside the fiber is high enough to interact with the acetylene gas in the gas chamber. The acetylene gas has an excellent photothermal coefficient, and the acetylene gas in the airtight chamber can efficiently absorb the energy of the evanescent field and generate heat, and the heated micro-nano fiber 132 can phase modulate the signal light through the thermo-optic effect. The tapered region 134 of the micro-nano fiber 132 and the acetylene gas are encapsulated in the sealed cavity 131 . The control light and the modulated signal light are output from the pigtail of the micro-nano fiber 132, and then enter the fiber Bragg grating 140, so that the control light is reflected back into the micro-nano fiber 132 to be absorbed again, and the amplitude of phase modulation is enhanced. The remaining control light is returned to the port of the circulator 150 through the common end and the first light input end of the wavelength division multiplexer 120 , and then output from another port of the circulator 150 . The other signal light is adjusted by the matching arm assembly. After passing through the second coupler, the two signal lights are jointly input to the detection assembly. When the two signal lights are combined, interference light is generated, and interference fringes appear. The phase difference of the transmitted light changes, which causes the movement of the interference fringes. The optical detection component receives the change information of the interference fringes, and inputs it into the appropriate data processing system, and finally obtains the phase modulation of the signal light. Compared with the existing modulator, this scheme adopts the photothermal effect of the medium gas based on the micro-nano fiber 132 to realize the phase modulation of the signal light. Compared with the existing modulator, it has higher mode field energy density, mild light absorption, uniform heat generation, and small scattering loss. And the advantage of simple preparation process.

It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above descriptions, and all these improvements and transformations should belong to the protection scope of the appended claims of the present invention.

Claims (10)

1. an all-optical phase modulation system based on gas photothermal effect in a micro-nano optical fiber, is characterized in that, comprises: a signal light source, the signal light source is used to generate signal light; a first coupler, the first coupler is connected to the signal light source, and outputs the signal light from the first output end and the second output end respectively; a phase modulator, the phase modulator is connected to the first output end, the phase modulator includes a pump light source, and an optical fiber air chamber, the pump light source is used to emit control light; the optical fiber air chamber includes A sealed inner cavity, and a micro-nano optical fiber located in the sealed inner cavity, the outside of the micro-nano optical fiber is filled with absorbing gas, the micro-nano optical fiber receives the control light and the signal light, and passes the control light changing the temperature and refractive index of the absorbing gas to cause a phase change of the signal light; a matching arm assembly, the input end of the matching arm assembly is connected to the second output end; a second coupler, the first input end of the second coupler is connected to the phase modulator, and the second input end is connected to the output end of the matching arm assembly; and a detection component, the detection component is connected to the output end of the second coupler. 2 . The all-optical phase modulation system based on the photothermal effect of gas in micro-nano fibers according to claim 1 , wherein the matching arm assembly comprises: a piezoelectric fiber stretcher, the piezoelectric fiber stretcher connected to the second output; a polarization controller, which is connected to the light output end of the piezoelectric fiber stretcher and connected to the second coupler. 3. The all-optical phase modulation system based on the photothermal effect of gas in micro-nano optical fibers according to claim 2, wherein the matching arm assembly further comprises: a servo controller, the servo controller is connected to the detection assembly and the piezoelectric fiber stretcher, which is driven by the servo controller to lock the output signal at the point of maximum slope. 4. The all-optical phase modulation system based on the photothermal effect of gas in the micro-nano fiber according to claim 1, wherein the phase modulator further comprises: a wavelength division multiplexer, the first light input end of the wavelength division multiplexer is arranged at the light output end of the pump light source and is used for inputting the control light, and the second light input end is used for inputting the signal light; and a fiber Bragg grating, the fiber Bragg grating is arranged at the light-exiting end of the optical fiber air chamber, and is used for outputting signal light and reflecting control light; The micro-nano fiber includes: a fiber tail region and a tapered region; the fiber tail region is located at both ends of the tapered region. 5. The all-optical phase modulation system based on the photothermal effect of gas in the micro-nano fiber according to claim 4, wherein the micro-nano fiber is made of a single-mode fiber taper; The diameter of the cone is 0.1-10 microns, and the length of the cone is 0.1-10 cm. 6 . The all-optical phase modulation system based on the photothermal effect of gas in a micro-nano fiber according to claim 4 , wherein the pump light source and the wavelength division multiplexer are connected by an optical fiber. 7 . 7. The all-optical phase modulation system based on the gas photothermal effect in the micro-nano fiber according to claim 4, wherein the pump light source comprises: a pump light laser, and the pump light laser is used for emission control Light; an amplifier, where the amplifier is arranged at the light output end of the pump laser, and is used to amplify the control light; an acousto-optic modulator, the acousto-optic modulator is arranged at the light output end of the amplifier, and is used for modulating the intensity of the control light. 8 . The all-optical phase modulation system based on the photothermal effect of gas in a micro-nano fiber according to claim 7 , wherein a circulator is provided between the pump light source and the wavelength division multiplexer. 9 . 9 . The all-optical phase modulation system based on the photothermal effect of gas in micro-nano optical fibers according to claim 4 , wherein the reflection bandwidth of the fiber Bragg grating is 0.1-10 nanometers, and the center wavelength is the same as that of the control light. 10 . Corresponding to the wavelength, the reflectivity is 99%. 10. The all-optical phase modulation system based on the photothermal effect of gas in micro-nano optical fibers according to any one of claims 1-9, wherein the absorbing gas comprises: acetylene, methane or/and carbon dioxide.

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