CN115200618B - All-optical phase modulation system based on gas photo-thermal effect in micro-nano optical fiber - Google Patents
All-optical phase modulation system based on gas photo-thermal effect in micro-nano optical fiber Download PDFInfo
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
- G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0147—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on thermo-optic effects
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- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention discloses an all-optical phase modulation system based on the gas photo-thermal effect in micro-nano optical fibers, 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 pump light source and an optical fiber air chamber, wherein the pump light source is used for emitting control light; the optical fiber air chamber comprises a sealed inner cavity and a micro-nano optical fiber positioned in the sealed inner cavity, wherein 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 refractive index of the absorptive gas are changed by the control light so as to cause the phase change of the signal light; the input end is connected with the matching arm assembly of 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 assembly; and the detection assembly 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
Technical Field
The invention relates to the technical field of optical phase modulation, in particular to an all-optical phase modulation system based on a gas photo-thermal effect in micro-nano optical fibers.
Background
Optical phase modulators are important devices in the fields of optical fiber communication and sensing, and conventional optical phase modulators are mostly manufactured based on the principle of the electro-optical effect of crystalline materials. The heterogeneous characteristics between the quartz optical fiber and the crystal material lead the traditional optical phase modulator to have large insertion loss, low integration level, large packaging volume and complex process.
The existing phase modulator generally adopts solid thermosensitive materials such as graphene, transition metal chalcogenide, black phosphorus and the like, and has the defects of high scattering loss, low photodamage threshold and complex preparation process.
Accordingly, the prior art is still in need of improvement and development.
Disclosure of Invention
In view of the shortcomings of the prior art, the invention aims to provide an all-optical phase modulation system based on the gas photo-thermal effect in the micro-nano optical fiber, which has the advantages of small scattering loss, uniform heat generation and simple preparation process based on the photo-thermal effect of the gas in the evanescent field of the micro-nano optical fiber.
The technical scheme of the invention is as follows:
An all-optical phase modulation system based on gas photo-thermal effect in micro-nano optical fiber, comprising:
a signal light source for generating signal light;
The first coupler is connected with the signal light source and outputs the signal light from the first output end and the second output end respectively;
The phase modulator is connected to the first output end and comprises a pumping light source and an optical fiber air chamber, and the pumping light source is used for emitting control light; the optical fiber air chamber comprises a sealed inner cavity and a micro-nano optical fiber positioned in the sealed inner cavity, wherein 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 refractive index of the absorptive gas are changed by the control light so as to cause the phase change of the signal light;
The input end of the matching arm assembly is connected with the second output end;
the first input end of the second coupler is connected with the phase modulator, and the second input end of the second coupler is connected with the output end of the matching arm assembly;
and the detection component is connected with the output end of the second coupler.
Further, the mating arm assembly includes: the piezoelectric optical fiber stretcher is connected to the second output end;
and the polarization controller is connected with the light emitting end of the piezoelectric optical fiber stretcher and is connected with the second coupler.
Further, the mating arm assembly further includes: and the servo controller is connected with the detection assembly and the piezoelectric optical fiber stretcher, and the piezoelectric optical fiber stretcher locks the output signal at the maximum slope point through the driving of the servo controller.
Further, the phase modulator further includes:
the first light inlet end of the wavelength division multiplexer is arranged at the light outlet end of the pumping light source and used for inputting control light, and the second light inlet end is used for inputting signal light; and
The optical fiber Bragg grating is arranged at the light-emitting end of the optical fiber air chamber and is used for outputting signal light and reflecting control light;
the micro-nano optical fiber comprises: a fiber tail region and a cone region; the fiber tail regions are positioned at two ends of the cone region.
Further, the micro-nano optical fiber is made of a single-mode optical fiber by tapering;
The diameter of the cone region is 0.1-10 micrometers, and the length of the cone region is 0.1-10 cm.
Further, the pumping light source is connected with the wavelength division multiplexer through an optical fiber.
Further, the pump light source includes: the pump light laser is used for emitting control light;
The amplifier is arranged at the light outlet end of the pump light laser and is used for amplifying the control light;
and the acousto-optic modulator is arranged at the light emitting end of the amplifier and used for modulating the intensity of the control light.
Further, a circulator is arranged between the pumping 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 absorptive gas includes: acetylene, methane or/and carbon dioxide.
The beneficial effects are that: compared with the prior art, the all-optical phase modulation system based on the gas photo-thermal effect in the micro-nano optical fiber provided by the invention has the advantages that the control light is generated through the pumping light source, the signal light is generated through the signal light source, the signal light is divided into two paths through the first coupler, the control light and the pumping light are jointly input into the optical fiber air chamber in the phase modulator, the thermo-optical effect generated by the interaction of the control light in the evanescent field of the micro-nano optical fiber and the absorptive gas in the mode field range is controlled, the temperature of the absorptive gas and the micro-nano optical fiber is caused to rise, and the refractive index of the micro-nano optical fiber is changed due to the temperature change through the thermo-optical effect, so that the phase of the signal light transmitted along the micro-nano optical fiber is changed; the other path of signal light is regulated by the matching arm component through the matching arm component, and the two paths of signal light are jointly input into the detection component after passing through the second coupler, so that interference light is generated when the two paths of signal light are combined, interference fringes are generated, and when the phase difference of the transmission light in the two optical fibers is changed, the movement of the interference fringes is caused. The optical detection component receives the change information of the interference fringes and inputs the change information to a proper data processing system to finally obtain the phase modulation of the signal light.
Drawings
FIG. 1 is a schematic block diagram of an embodiment of an all-optical phase modulation system based on the gas photothermal effect in micro-nano optical fibers according to the present invention;
FIG. 2 is a schematic block diagram of a phase modulator of an embodiment of an all-optical phase modulation system based on the gas photothermal effect in micro-nano optical fibers according to the present invention;
FIG. 3 is a schematic cross-sectional view of a micro-nano fiber of an embodiment of an all-optical phase modulation system based on gas photothermal effects in the micro-nano fiber according to the invention;
FIG. 4 is a graph of evanescent field distribution of a micro-nano fiber of an embodiment of an all-optical phase modulation system based on the gas photothermal effect in the micro-nano fiber according to the present invention;
FIG. 5 is a phase modulated time domain signal diagram of an embodiment of an all-optical phase modulation system based on the gas photothermal effect in micro-nano optical fibers according to the present invention;
FIG. 6 is a graph showing the response of the control optical power of an embodiment of an all-optical phase modulation system based on the gas photo-thermal effect in micro-nano fiber according to the present invention;
Fig. 7 is a modulation frequency response curve of an embodiment of an all-optical phase modulation system based on the gas photo-thermal effect in micro-nano optical fiber according to the present invention.
The reference numerals in the drawings: 10. a phase modulator; 110. a pump light source; 111. a pump light laser; 112. an amplifier; 113. an acousto-optic modulator; 120. a wavelength division multiplexer; 130. an optical fiber air chamber; 131. sealing the inner cavity; 132. micro-nano optical fiber; 133. a fiber tail region; 134. a cone region; 135. an evanescent field; 140. a fiber bragg grating; 150. a circulator; 20. a signal light source; 30. a first coupler; 40. a mating arm assembly; 410. a piezoelectric fiber stretcher; 420. a polarization controller; 430. a servo controller; 50. a second coupler; 60. a detection assembly; 610. a photodetector; 620. an oscilloscope.
Detailed Description
The invention provides an all-optical phase modulation system based on the gas photo-thermal effect in micro-nano optical fibers, which is further described in detail below with reference to the accompanying drawings and examples in order to make the purposes, technical schemes and effects of the invention clearer and more definite. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The principle of many schemes for modulating signal light is that heat is generated by absorbing a control light evanescent field by using a thermosensitive material, so that the refractive index of a waveguide is changed, and the phase of the signal light in the waveguide is modulated. But is limited by intrinsic absorption of a thermosensitive material and scattering effect caused by imperfect coating, the insertion loss is up to 10dB, and the light-transmitting wave band is narrower; limited by the slow heat dissipation of air, the modulation bandwidth is typically below 100Hz. And the thermosensitive material is complex to prepare due to the need of waveguide post-treatment and material coating, and the long-term reliability is difficult to meet the practical requirement. In order to solve the limitation problem of the thermosensitive material, an all-optical phase modulation technology may be adopted to improve the problem, so this embodiment proposes an all-optical phase modulation system based on the gas photo-thermal effect in the micro-nano optical fiber to improve the problem.
The specific structure of this embodiment is as follows:
As shown in fig. 1, the present embodiment provides an all-optical phase modulation system based on the photo-thermal effect of the gas in the micro-nano optical fiber, and modulates the signal light by controlling the photo-thermal effect generated by the light and the adsorptive 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 for generating signal light, the first coupler 30 is connected with the signal light source 20, and the signal light is respectively output from a first output end and a second output end of the first coupler 30; the phase modulator 10 is connected to the first output end, the phase modulator 10 includes a pump light source 110, and an optical fiber air chamber 130, and the pump light source 110 is used for emitting control light; the optical fiber air chamber 130 comprises a sealed inner cavity 131 and a micro-nano optical fiber 132 positioned in the sealed inner cavity 131, wherein the outer part of the micro-nano optical fiber 132 is filled with absorptive gas, the micro-nano optical fiber 132 receives control light and signal light, and the temperature and refractive index of the absorptive gas are changed by the control light to cause the phase change of the signal light; an input end of the matching arm assembly 40 is connected with a second output end of the first coupler 30; a first input of the second coupler 50 is connected to the phase modulator 10 and a second input is connected to an output of the matching arm assembly 40; the detection assembly 60 is connected to the output of the second coupler 50. Generating control light by the pump light source 110, generating signal light by the signal light source 20, and dividing the signal light into two paths by the first coupler 30, wherein one path of the signal light and the control light are jointly input into the optical fiber air chamber 130 in the phase modulator 10, controlling a thermo-optical effect generated by interaction of the light in an evanescent field 135 of the micro-nano optical fiber 132 and absorptive gas within a mode field range, and causing temperature rise of the absorptive gas and the micro-nano optical fiber 132, wherein the temperature change causes refractive index change of the micro-nano optical fiber 132 by the thermo-optical effect, so that the phase of the signal light transmitted along the micro-nano optical fiber 132 is changed; the other path of signal light is regulated by the matching arm assembly 40, and after passing through the second coupler 50, the two paths of signal light are jointly input into the detection assembly 60, and interference light is generated when the two paths of signal light are combined, so that interference fringes appear, and when the phase difference of the transmission light in the two optical fibers changes, the movement of the interference fringes is caused. The optical detection component 60 receives the change information of the interference fringes, and inputs the change information to a proper data processing system to finally obtain the phase modulation of the signal light.
As shown in fig. 1 and 2, the specific structure of the phase modulator 10 in this embodiment further includes: wavelength division multiplexer 120, and fiber bragg grating 140. The pump light source 110 in this embodiment is configured to emit control light, and the control light is injected into the wavelength division multiplexer 120; the wavelength division multiplexer 120 has a first light inlet and a second light inlet, and a common end for output; the first light-in end of the wavelength division multiplexer 120 is disposed at the light-out end of the pump light source 110 and is used for inputting control light, and the second light-in end is used for inputting signal light to be modulated, wherein the signal light is a first path of signal light split by the first coupler, and the control light and the signal light can be combined 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 outputs the combined control light and signal light from the wavelength division multiplexer 120; the temperature and refractive index of the absorptive gas are changed by controlling light in the optical fiber gas cell 130 to cause a phase change of the signal light. The fiber bragg grating 140 is disposed at the light outlet end of the fiber optic chamber 130, the control light and the signal light output from the fiber optic chamber 130 enter the fiber bragg grating 140, the fiber bragg grating 140 is used for outputting the signal light and reflecting the control light, so as to obtain the modulated signal light, the control light reflected by the fiber bragg grating 140 enters the fiber optic chamber 130 from the other end of the micro-nano fiber 132 and continuously acts on the absorptive gas to generate the photo-thermal effect, so that the photo-thermal effect can be performed at both ends of the fiber optic chamber 130, and the photo-thermal effect in the transmission direction of the micro-nano fiber 132 is mild.
In this embodiment, the pump light source 110 generates the control light, and then the wavelength division multiplexer 120 inputs the control light and the pump light into the optical fiber air chamber 130 together, so as to control the thermo-optical effect generated by the interaction of the light in the evanescent field 135 of the micro-nano optical fiber 132 and the absorptive gas in the mode field range, and cause the temperature rise of the absorptive gas and the micro-nano optical fiber 132, and the temperature change causes the refractive index change of the micro-nano optical fiber 132 through the thermo-optical effect, thereby changing the phase of the signal light transmitted along the micro-nano optical fiber 132, and realizing the phase modulation of the signal light. 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 continuously acts on the absorptive gas to generate a photo-thermal effect, so that the photo-thermal effect can be carried out at both ends of the fiber air chamber 130, uniform heat generation is realized at both ends of the micro-nano fiber 132 in the transmission direction, the photo-thermal effect of the adopted gas is different from that of the existing solid photo-thermal material, gas molecules are strongly absorbed only at discrete narrow absorption lines, the wavelength of the signal light outside the absorption lines is almost not absorbed, the problems of intrinsic absorption of the material and scattering effect caused by imperfect coating are avoided, and scattering loss is reduced; the wavelength division multiplexer 120, the optical fiber air chamber 130 and the optical fiber Bragg grating 140 can be integrated, so that the integration level is high, and the preparation process is simple; the method can be widely applied to the fields of optical fiber communication and optical fiber sensing.
As shown in fig. 3 and 4, the micro-nano optical fiber 132 in the present embodiment specifically includes a tail region 133 and a taper region 134; fiber pigtail region 133 is located at each end of taper region 134. The fiber tail region 133 is used as a region for light to enter and exit the optical fiber, the cone region 134 is used as a main functional region of the micro-nano optical fiber 132, the micro-nano optical fiber has the characteristic of small diameter, and the evanescent field 135 is stronger, so that the photo-thermal effect can be generated with the absorptive gas conveniently; the tapered region 134 is positioned in the middle of the sealed cavity 131, so that the evanescent field is uniformly distributed in the sealed cavity 131 and uniformly acts with the absorptive gas. The power threshold of the control light can be reduced by regulating and controlling the dispersion of the micro-nano optical fiber 132, and the nonlinear interaction length is reduced; the stiffness coefficient is small, thereby being convenient for stretching and manufacturing. The evanescent field excited outside the fiber by the control light transmitted in the micro-nano fiber 132 is used in this embodiment to generate the interaction of light and absorptive gas, which has a higher mode field energy density than other fiber modulators. The micro-nano optical fiber 132 in this embodiment is made of a single-mode optical fiber, the diameter of the tapered region 134 is 0.1-10 μm, and the length of the tapered region 134 is 0.1-10 cm. In micro-nano optical fiber 132, depending on the diameter of taper region 134, a different percentage of the optical field propagates as evanescent waves outside the fiber, which can react with the absorptive gas, e.g., 80% of the evanescent field outside the fiber when taper region 134 is 0.2 microns in diameter. This facilitates a rapid action with the absorbent gas. The micro-nano optical fiber 132 with the above-mentioned form is adopted, so that the coupling loss from the optical fiber to the device to the optical fiber is extremely low, the roughness is extremely low, the waveguide surface is extremely low, the optical field is strongly limited by a high refractive index difference, the evanescent field is a large percentage, the quality is extremely light, and the dispersion characteristic is flexible.
The pump light source 110 and the wavelength division multiplexer 120 in this embodiment are connected by an optical fiber, so that the control light is directly transmitted to the optical fiber air chamber 130 to react through the optical fiber, and the wavelength division multiplexer has the advantage of small transmission loss, and the pump light source 110 can be far away 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, so that the wavelength division multiplexer has the advantages of small volume, electromagnetic interference resistance and high temperature resistance.
The two ends of the micro-nano optical fiber 132 in the embodiment can be directly welded through an optical fiber link, so that the wavelength division multiplexer 120 is connected with the optical fiber air chamber 130 through the optical fiber, and the optical fiber bragg grating 140 is connected with the optical fiber air chamber 130 through the optical fiber, thereby facilitating the stable transmission of control light and signal light, having extremely low coupling loss, and simultaneously having 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 electromagnetic interference resistance.
As shown in fig. 2, the pump light source 110 in this embodiment includes: pump laser 111, amplifier 112, and acousto-optic modulator 113. The pump light laser 111 is configured to emit control light, and the wavelength of the control light generated by the pump light source 110 corresponds to any one of absorption lines of an absorptive gas (acetylene gas). The control laser in this embodiment can generate single-frequency control light with a wavelength of 1532.83nm, which corresponds to the P13 absorption line of acetylene gas. The amplifier 112 is an optical fiber amplifier 112, and is disposed at the light emitting end of the pump laser 111 and is used for amplifying control light; an acousto-optic modulator 113 is provided at the light-emitting end of the amplifier 112 and is used for modulating the intensity of the control light. The power of the control light is amplified by the optical fiber amplifier 112 and then modulated by the acousto-optic modulator 113, and the modulation of the control light by the acousto-optic modulator 113 in this embodiment may be sine wave modulation, triangular wave modulation, sawtooth wave modulation, pulse modulation, etc. The modulated control light and signal light are output to the optical fiber cell 130, and the signal light is modulated by the photothermal effect of the absorptive gas in the optical fiber cell 130.
In this embodiment, a circulator 150 is disposed between the pump light source 110 and the wavelength division multiplexer 120, and specifically, the 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, and after the control light reflected by the fiber bragg grating 140 is emitted from the fiber air chamber 130, the remaining control light is returned back into the circulator 150 through the common end and the first light inlet end of the wavelength division multiplexer 120 and is output from the other port of the circulator 150.
The reflection bandwidth of the fiber bragg grating 140 in this embodiment is 0.1-10 nm, the center wavelength corresponds to the wavelength of the control light, the reflectivity is 99%, and the reflectivity 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 optical fiber 132 to be absorbed again, so that the control light enters at the other end of the micro-nano optical fiber 132 to generate a photo-thermal effect, and meanwhile, the temperature change is carried out from the two ends, so that the phase modulation amplitude is enhanced.
The sealed cavity 131 in this embodiment is also filled with a buffer gas. The buffer gas includes: the buffer gas can play a more stable role in controlling the transmission of light and signal light, and the volume fraction of the absorptive gas in the mixed gas is not less than 1%.
The absorptive gas in this embodiment includes: acetylene, methane or/and carbon dioxide. In this embodiment, the absorptive gas may be acetylene gas, which has an excellent photo-thermal coefficient, and the acetylene gas in the closed air chamber can efficiently absorb the energy of the evanescent field and generate heat, and the heated micro-nano optical fiber 132 generates phase modulation on the signal light by the thermo-optical effect.
As shown in fig. 1, another path of signal light split by the first coupler 30 enters the matching arm assembly 40, and 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 emitting end of the piezoelectric fiber stretcher 410 and connected to the second coupler 50, the length of the optical fiber can be adjusted by the piezoelectric fiber stretcher 410, the polarization controller 420 is used for adjusting the polarization of the signal light in the matching arm assembly 40, and when the signal light modulated by the phase modulator 10 meets the second signal light in the matching arm assembly 40, the maximum interference signal is obtained.
As shown in fig. 1, the matching arm assembly 40 in this embodiment further includes a servo controller 430, where the servo controller 430 connects the probe assembly 60 and the piezoelectric fiber stretcher 410, and the piezoelectric fiber stretcher 410 locks the output signal of the interferometer at the maximum slope point by driving of the servo controller 430. This facilitates the collection and processing of interference signals by the detection assembly 60. Because the working point of the system easily drifts due to environmental noise, a small vibration, such as walking by a person nearby, can cause the working point to drift for hundreds of cycles, so that the locking of the working point is needed to keep the working point at the maximum slope point. The locking mode relies on the servo controller 430 and the piezoelectric fiber stretcher 410, and when locking is performed, the optical detector 610 inputs the detected optical signal to the servo controller 430, the signal received by the servo controller 430 contains drift of the working point due to noise, the servo controller 430 extracts a noise intensity signal through filtering, and 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, the working point drift introduced by the piezoelectric fiber stretcher 410 can be offset with the working point drift caused by the noise, and the working point can be stabilized at the point with the maximum slope.
As shown in fig. 1, the detection assembly 60 in this embodiment includes a light detector 610, and an oscilloscope 620. The photodetector 610 receives the change information of the interference fringes of the modulated signal light, and inputs the change information to the oscilloscope 620 for data processing and display, thereby obtaining a measurement result.
Fig. 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. Wherein the wavelength of the signal light is 1550nm. Therefore, the phase modulation amplitude of the signal light by the full-optical phase modulation system is 2 pi. Further, experiments confirmed that the proportional relation between the control optical power and the photo-thermal phase modulation amplitude was shown in fig. 6. In the experiment, the modulation frequency of the control light was 1kHz. Further, the phase modulation amplitude and frequency response of the present phase modulator to signal light at different wavelengths within the c+l band, i.e., 1529, 1550, 1590 and 1625nm, were demonstrated, and the result is shown in fig. 7, in which the control light power was 148mW, and the phase modulation amplitude of the present modulator to signal light increased with decreasing control light modulation frequency.
In summary, in the all-optical phase modulation system based on the gas photo-thermal effect in the micro-nano optical fiber, the pump light source 110 of the phase modulator 10 generates the control light which can be modulated, the signal light is generated by the signal light source, the signal light is divided into two paths by the first coupler, one path of the signal light and the control light is combined with the signal light to be modulated by the wavelength division multiplexer 120, and then the two paths of the control light and the signal light are input to the micro-nano optical fiber 132 in the optical fiber air chamber 130 through the public end of the wavelength division multiplexer 120. Because evanescent field energy is distributed outside the micro-nano optical fiber 132, the micro-nano optical fiber 132 is packaged in an environment filled with acetylene and buffer gas with fixed concentration by using a sealed inner cavity 131 with good air tightness. The optical fiber air chamber 130 can protect the micro-nano optical fiber 132 from mechanical damage possibly encountered in use, and simultaneously prevent dust or air and other substances in the external environment from participating in interaction between an evanescent field in the micro-nano optical fiber 132 and the external environment, so that the heat generating efficiency and the refractive index of the absorptive gas in the photo-thermal effect are fixed along with the change rate of heat. The control light and the signal light are input from the tail fiber of the micro-nano optical fiber 132, and at the taper region 134 of the micro-nano optical fiber 132, the control light is absorbed by the absorptive gas (acetylene gas) through the evanescent field thereof, and the micro-nano optical fiber 132 is heated by the photo-thermal effect. The energy distribution of the micro-nano optical fiber 132 and the evanescent field of the control light transmitted along the micro-nano optical fiber 132 is shown in fig. 3, and the waveguide structure of the micro-nano optical fiber 132 enables the energy originally transmitted inside the optical fiber to leak to the outside of the optical fiber to form the evanescent field and transmit along the optical fiber, and the energy density leaked to the outside of the optical fiber is higher, so that the energy can fully interact with acetylene gas in the gas chamber. The acetylene gas has excellent photothermal coefficient, and the acetylene gas in the closed air chamber can efficiently absorb the energy of the evanescent field and generate heat, and the heated micro-nano optical fiber 132 generates phase modulation on the signal light through the thermo-optical effect. The taper region 134 of the micro-nano optical fiber 132 and acetylene gas are encapsulated in the sealed inner cavity 131. The control light and the modulated signal light are output from the pigtail of the micro-nano optical fiber 132 and enter the fiber bragg grating 140, so that the control light is reflected back into the micro-nano optical fiber 132 to be absorbed again, and the phase modulation amplitude is enhanced. The remaining control light returns to the port of the circulator 150 after passing through the common port and the first light inlet port of the wavelength division multiplexer 120, and is output from the other port of the circulator 150. The other path of signal light is regulated by the matching arm assembly, and the two paths of signal light are jointly input into the detection assembly after passing through the second coupler, so that interference light is generated when the two paths of signal light are combined, interference fringes are generated, and when the phase difference of the transmission light in the two optical fibers is changed, the movement of the interference fringes is caused. The optical detection component receives the change information of the interference fringes and inputs the change information to a proper data processing system to finally obtain the phase modulation of the signal light. The scheme adopts the medium gas photo-thermal effect based on the micro-nano optical fiber 132 to realize the phase modulation of the signal light, and has the advantages of higher mode field energy density, mild light absorption, uniform heat generation, small scattering loss and simple preparation process compared with the existing modulator.
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.
Claims (10)
1. An all-optical phase modulation system based on gas photo-thermal effect in micro-nano optical fiber, which is characterized by comprising:
a signal light source for generating signal light;
The first coupler is connected with the signal light source and outputs the signal light from the first output end and the second output end respectively;
The phase modulator is connected to the first output end and 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 air chamber comprises a sealed inner cavity and a micro-nano optical fiber positioned in the sealed inner cavity, wherein the outer part of the micro-nano optical fiber is filled with absorptive gas, the micro-nano optical fiber receives the control light and the signal light, and the temperature and the refractive index of the absorptive gas are changed by the control light so as to cause the phase change of the signal light;
the input end of the matching arm assembly is connected with the second output end;
The first input end of the second coupler is connected with the phase modulator, and the second input end of the second coupler is connected with the output end of the matching arm assembly;
and the detection component is connected with the output end of the second coupler.
2. The all-optical phase modulation system based on gas photothermal effects in micro-nano optical fibers according to claim 1, wherein the matching arm assembly comprises: the piezoelectric optical fiber stretcher is connected to the second output end;
and the polarization controller is connected with the light emitting end of the piezoelectric optical fiber stretcher and is connected with the second coupler.
3. The all-optical phase modulation system based on gas photothermal effects in micro-nano optical fibers of claim 2, wherein the matching arm assembly further comprises: and the servo controller is connected with the detection assembly and the piezoelectric optical fiber stretcher, and the piezoelectric optical fiber stretcher locks an output signal at a maximum slope point through the driving of the servo controller.
4. The all-optical phase modulation system based on gas photothermal effects in micro-nano optical fibers according to claim 1, wherein the phase modulator further comprises:
The first light inlet end of the wavelength division multiplexer is arranged at the light outlet end of the pumping light source and used for inputting the control light, and the second light inlet end is used for inputting signal light; and
The optical fiber Bragg grating is arranged at the light-emitting end of the optical fiber air chamber and is used for outputting signal light and reflecting control light;
the micro-nano optical fiber comprises: a fiber tail region and a cone region; the fiber tail regions are positioned at two ends of the cone region.
5. The all-optical phase modulation system based on the gas photo-thermal effect in micro-nano optical fiber according to claim 4, wherein the micro-nano optical fiber is made of single-mode fiber by tapering;
the diameter of the cone region is 0.1-10 micrometers, and the length of the cone region is 0.1-10 centimeters.
6. The all-optical phase modulation system based on gas photo-thermal effect in micro-nano optical fiber according to claim 4, wherein the pump light source is connected with the wavelength division multiplexer through optical fiber.
7. The all-optical phase modulation system based on gas photo-thermal effect in micro-nano optical fiber according to claim 4, wherein the pump light source comprises: the pump light laser is used for emitting control light;
The amplifier is arranged at the light emitting end of the pump light laser and is used for amplifying the control light;
and the acousto-optic modulator is arranged at the light emitting end of the amplifier and used for modulating the intensity of the control light.
8. The all-optical phase modulation system based on the gas photo-thermal effect in micro-nano optical fibers according to claim 7, wherein a circulator is arranged between the pumping light source and the wavelength division multiplexer.
9. The all-optical phase modulation system based on gas photo-thermal effect in micro-nano optical fiber according to claim 4, wherein 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%.
10. The all-optical phase modulation system based on the photothermal effect of gas in a micro-nano optical fiber according to any one of claims 1 to 9, wherein the absorptive gas comprises: acetylene, methane or/and carbon dioxide.
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| CN106153174A (en) * | 2015-04-22 | 2016-11-23 | 香港理工大学深圳研究院 | Phase demodulator, optical fiber sound pressure demodulating system, demodulation method and manufacture method |
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| CN106153174A (en) * | 2015-04-22 | 2016-11-23 | 香港理工大学深圳研究院 | Phase demodulator, optical fiber sound pressure demodulating system, demodulation method and manufacture method |
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