CN115200618A - All-optical phase modulation system based on gas photothermal effect in micro-nano optical fiber - Google Patents
All-optical phase modulation system based on gas photothermal effect in micro-nano optical fiber Download PDFInfo
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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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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
Technical Field
The invention relates to the technical field of optical phase modulation, in particular to an all-optical phase modulation system based on gas photothermal effect in a micro-nano optical fiber.
Background
The optical phase modulator is an important device in the field of optical fiber communication and sensing, and the traditional optical phase modulator is manufactured based on the principle of the electro-optic effect of a crystal material. Due to the heterogeneous characteristics between the quartz optical fiber and the crystal material, the traditional optical phase modulator has the advantages of large insertion loss, low integration level, large packaging volume and complex process.
The solid-state thermosensitive materials commonly used in the existing phase modulator, such as graphene, transition metal chalcogenide, black phosphorus and the like, have the disadvantages of large scattering loss, low optical damage threshold and complex preparation process.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide an all-optical phase modulation system based on the photothermal effect of the gas in the micro-nano optical fiber, and the system has the advantages of small scattering loss, uniform heat generation and simple preparation process based on the photothermal 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 photothermal effect in micro-nano optical fiber comprises:
the signal light source is used 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 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;
a first input end of the second coupler is connected with the phase modulator, and a second input end of the second coupler 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.
Further, the mating arm assembly includes: the piezoelectric optical fiber stretcher is connected to the second output end;
and the polarization controller is connected to the light outlet end of the piezoelectric optical fiber stretcher and connected with the second coupler.
Further, the mating 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 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 is used for inputting control light, and the second light inlet end of the wavelength division multiplexer is used for inputting signal light; and
the fiber Bragg grating is arranged at the light outlet end of the 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 by tapering a single mode optical fiber;
the diameter of the cone area is 0.1-10 microns, and the length of the cone area is 0.1-10 cm.
Furthermore, the pumping light source is connected with the wavelength division multiplexer through an optical fiber.
Further, the pumping 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 outlet end of the amplifier and is used for modulating the intensity of the control light.
Further, a circulator is arranged between the pumping light source and the wavelength division multiplexer.
Furthermore, the reflection bandwidth of the fiber Bragg grating is 0.1-10 nanometers, the central wavelength corresponds to the wavelength of the control light, and the reflectivity is 99%.
Further, the absorbent gas includes: acetylene, methane or/and carbon dioxide.
Has the beneficial effects that: compared with the prior art, the all-optical phase modulation system based on the photothermal effect in the micro-nano optical fiber provided by the invention has the advantages that control light is generated through a pumping light source, signal light is generated through a signal light source, the signal light is divided into two paths through a first coupler, one path of the control light and the pumping light are jointly input into an optical fiber air chamber in a phase modulator, the thermo-optical effect generated by the interaction of the evanescent field of the control light in the micro-nano optical fiber and the absorption gas in the mode field range is caused, the temperature of the absorption gas and the micro-nano optical fiber is increased, the refractive index of the micro-nano optical fiber is changed through the thermo-optical effect, and the phase of the signal light transmitted along the micro-nano optical fiber is further changed; the other path of signal light is adjusted through the matching arm component, the two paths of signal light are input to the detection component together after passing through the second coupler, the two paths of signal light generate interference light when wave combination is carried out, therefore, 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 assembly receives the change information of the interference fringes and inputs the change information into a proper data processing system to finally obtain the phase modulation of the signal light.
Drawings
Fig. 1 is a structural principle block diagram of an embodiment of an all-optical phase modulation system based on a photothermal effect in a micro-nano optical fiber according to the invention;
fig. 2 is a structural schematic block diagram of a phase modulator of an embodiment of an all-optical phase modulation system based on photothermal effect in a micro-nano optical fiber according to the present invention;
fig. 3 is a schematic cross-sectional view of a micro-nano optical fiber according to an embodiment of an all-optical phase modulation system based on a photothermal effect in the micro-nano optical fiber;
fig. 4 is an evanescent field distribution diagram of a micro-nano optical fiber according to an embodiment of the all-optical phase modulation system based on the gas photothermal effect in the micro-nano optical fiber;
fig. 5 is a phase modulation time domain signal diagram of an embodiment of an all-optical phase modulation system based on a gas photothermal effect in a micro-nano optical fiber according to the present invention;
fig. 6 is a control light power response curve 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;
fig. 7 is a modulation frequency response curve of an embodiment of an all-optical phase modulation system based on a gas photothermal effect in a micro-nano optical fiber.
The reference numbers in the figures: 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 fibers; 133. a fiber tail region; 134. a conical zone; 135. an evanescent field; 140. a fiber Bragg grating; 150. a circulator; 20. a signal light source; 30. a first coupler; 40. a matching arm assembly; 410. a piezoelectric fiber stretcher; 420. a polarization controller; 430. a servo controller; 50. a second coupler; 60. a detection component; 610. a light detector; 620. an oscilloscope.
Detailed Description
The invention provides an all-optical phase modulation system based on gas photothermal effect in micro-nano optical fibers, and in order to make the purpose, technical scheme and effect of the invention clearer and more clear, the invention is further described in detail below by referring to the attached drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The principle of the modulation scheme for the signal light is that heat is generated by using a thermosensitive material to absorb a control optical evanescent field, so that the refractive index of the waveguide is changed, and the phase of the signal light in the waveguide is modulated. But is limited by the scattering effect caused by intrinsic absorption and imperfect coating of the thermosensitive material, the insertion loss is as high as 10dB, and the light-passing wave band is narrow; limited by the slow dissipation of heat from the air, the modulation bandwidth is typically below 100Hz. And the thermosensitive material is complex in preparation because of waveguide post-treatment and material coating, and long-term reliability is difficult to meet practical requirements. In order to solve the limitation problem of the thermosensitive material, an all-optical phase modulation technique can be adopted to improve the limitation problem, so that the embodiment provides an all-optical phase modulation system based on the photothermal effect in the micro-nano fiber to improve the problem.
The specific structure of this embodiment is as follows:
as shown in fig. 1, the embodiment provides an all-optical phase modulation system based on photothermal effect in a micro-nano fiber, and modulates signal light by controlling photothermal effect generated by light and adsorptive gas. The all-optical phase modulation system comprises: signal light source 20, first coupler 30, phase modulator 10, matching arm assembly 40, second coupler 50, and 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 outputs the signal light from a first output end and a second output end of the first coupler 30 respectively; the phase modulator 10 is connected to the first output end, the phase modulator 10 includes a pump light source 110, and a fiber gas chamber 130, the pump light source 110 is used for emitting control light; the optical fiber gas chamber 130 comprises a sealed inner cavity 131 and a micro-nano optical fiber 132 positioned in the sealed inner cavity 131, an absorptive gas is filled outside the micro-nano optical fiber 132, the micro-nano optical fiber 132 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 assembly 40 is connected with the 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 the output of the matching arm assembly 40; the detection assembly 60 is connected to the output of the second coupler 50. Control light is generated by the pump light source 110, signal light is generated by the signal light source 20, the signal light is divided 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, the thermo-optic effect generated by the interaction of the control light in the evanescent field 135 of the micro-nano optical fiber 132 and the absorptive gas in the range of the mode field causes 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-optic effect, so that the phase of the signal light transmitted along the micro-nano optical fiber 132 is changed; the other signal light is adjusted by the matching arm assembly 40, and after passing through the second coupler 50, the two signal lights are jointly input to the detection assembly 60, and the two signal lights generate interference light during wave combination, so that interference fringes appear, and when the phase difference of the transmission light in the two optical fibers changes, the interference fringes move. The optical detection component 60 receives the change information of the interference fringes and inputs the change information into a proper data processing system to finally obtain the phase modulation of the signal light, and the scheme adopts the gas photothermal effect based on the micro-nano optical fiber 132 to realize 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 enters the wavelength division multiplexer 120; the wavelength division multiplexer 120 has a first light input end and a second light input end, and a common end for output; the first light input end of the wavelength division multiplexer 120 is disposed 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 signal light to be modulated, where the signal light is the first path of signal light split by the first coupler, and the control light and the signal light can be multiplexed by the wavelength division multiplexer 120. The optical fiber air chamber 130 is connected to a 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 the control light in the fiber gas cell 130 to cause a phase change of the signal light. The fiber bragg grating 140 is disposed at a light emitting end of the fiber gas chamber 130, the control light and the signal light output from the fiber gas chamber 130 enter the fiber bragg grating 140, the fiber bragg grating 140 is configured to output the signal light and reflect the control light, so as to obtain the modulated signal light, and the control light reflected by the fiber bragg grating 140 enters the fiber gas chamber 130 from the other end of the micro-nano fiber 132, and continues to act on the absorptive gas to generate a photo-thermal effect, so that both ends of the fiber gas chamber 130 can perform the photo-thermal effect, and the photo-thermal effect in the transmission direction of the micro-nano fiber 132 is mild.
In the embodiment, control light is generated by a pump light source 110, the control light and the pump light are input into an optical fiber air chamber 130 through a wavelength division multiplexer 120, a thermo-optic effect generated by interaction of the control light in an evanescent field 135 of a micro-nano optical fiber 132 and an absorptive gas in a mode field range is controlled, the temperature of the absorptive gas and the temperature of the micro-nano optical fiber 132 are increased, the temperature change causes the refractive index change of the micro-nano optical fiber 132 through the thermo-optic effect, the phase of signal light transmitted along the micro-nano optical fiber 132 is changed, and the phase modulation of the signal light is realized; the control light reflected by the fiber Bragg grating 140 enters the fiber gas chamber 130 from the other end of the micro-nano fiber 132 and continuously acts on the absorptive gas to generate a photothermal effect, so that both ends of the fiber gas chamber 130 can perform the photothermal effect, both ends of the micro-nano fiber 132 in the transmission direction generate heat uniformly, the photothermal effect of the adopted gas is different from that of the existing solid photothermal material, gas molecules only have strong absorption at discrete narrow absorption lines, and the wavelength of signal light outside the absorption lines hardly absorbs, so that the problems of scattering effect caused by intrinsic absorption and imperfect coating of the material are avoided, and the scattering loss is reduced; in addition, the wavelength division multiplexer 120, the optical fiber air chamber 130 and the optical fiber Bragg grating 140 can be arranged in an integrated manner, 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 this embodiment specifically includes a fiber tail region 133 and a tapered region 134; the pigtail regions 133 are located at both ends of the tapered region 134. The fiber tail region 133 is used as a region for light to enter and exit the optical fiber, and the cone region 134 is used as a main functional region of the micro-nano optical fiber 132, so that the micro-nano optical fiber has the characteristic of small diameter, and an evanescent field 135 of the micro-nano optical fiber is relatively strong, so that a photo-thermal effect can be generated with an absorptive gas conveniently; the tapered region 134 is located in the middle of the sealed cavity 131, so that the evanescent field can be uniformly distributed in the sealed cavity 131 and uniformly react with the absorptive gas. The power threshold of the control light can be reduced by regulating the dispersion of the micro-nano optical fiber 132, and the nonlinear interaction length is reduced; the coefficient of stiffness is small, thereby being convenient for stretching and manufacturing. In this embodiment, an evanescent field excited outside the optical fiber by the control light transmitted through the micro-nano optical fiber 132 is used to generate interaction between the light and the absorptive gas, and compared with other optical fiber modulators, the optical fiber modulator has a higher mode field energy density. The micro-nano optical fiber 132 in the embodiment is made of single-mode fiber tapering, the diameter of the tapered region 134 is 0.1-10 micrometers, and the length of the tapered region 134 is 0.1-10 centimeters. In the micro-nano fiber 132, according to the diameter of the tapered region 134, different percentages of the optical field propagate outside the fiber in the form of evanescent waves, and this portion of the evanescent field can react with the absorbing gas, for example, when the diameter of the tapered region 134 is 0.2 μm, the evanescent field outside the fiber accounts for 80%. This is advantageous for a rapid interaction with the absorbent gas. By adopting the micro-nano optical fiber 132 in the form, the waveguide fiber has extremely low coupling loss from the optical fiber to the device and then to the optical fiber, extremely low roughness of the waveguide surface, a strong limited optical field with high refractive index difference, a large-percentage evanescent field, extremely light weight and flexible dispersion characteristics.
The pumping light source 110 and the wavelength division multiplexer 120 in the embodiment are connected through the optical fiber, so that the control light is directly conducted to the optical fiber air chamber 130 through the optical fiber to react, the advantage of small transmission loss is achieved, the pumping light source 110 can be far away from the optical fiber air chamber 130, the phase of the signal light transmitted along the micro-nano optical fiber 132 is controlled through remote injection control, and the advantages of small size, electromagnetic interference resistance and high temperature resistance are achieved.
The two ends of the micro-nano optical fiber 132 in this 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 an optical fiber, and the 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 anti-electromagnetic interference capability.
As shown in fig. 2, the pumping light source 110 in the present embodiment includes: a pump laser 111, an amplifier 112, and an acousto-optic modulator 113. The pump light laser 111 is used to emit control light, and the wavelength of the control light generated by the pump light source 110 corresponds to any one absorption line of the absorptive gas (acetylene gas). The control laser in this embodiment can generate a 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, is arranged at the light output end of the pump light laser 111, and is used for amplifying the control light; the acousto-optic modulator 113 is provided at the light exit 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 optical fiber amplifier 112 and modulated by the acousto-optic modulator 113, and the acousto-optic modulator 113 in this embodiment may adjust the control light by sine wave modulation, triangular wave modulation, sawtooth wave modulation, pulse modulation, and the like. The modulated control light and signal light are output to the optical fiber gas chamber 130, and the signal light is modulated by the photothermal effect of the absorptive gas in the optical fiber gas chamber 130.
In this embodiment, a circulator 150 is disposed between the pumping 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 in one direction in the circulator 150 through the circulator 150, and after the control light reflected by the fiber bragg grating 140 exits from the fiber gas chamber 130, the remaining control light returns to the circulator 150 through the common end and the first light-incoming end of the wavelength division multiplexer 120, and is output from another port of the circulator 150.
The fiber bragg grating 140 in this embodiment has a reflection bandwidth of 0.1 to 10 nm, a central wavelength corresponding to the wavelength of the control light, a reflectivity of 99%, and a reflectivity 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 at the other end of the micro-nano fiber 132 to generate a photo-thermal effect, and meanwhile, temperature change is carried out from two ends, and the phase modulation amplitude is enhanced.
The sealed inner cavity 131 in this embodiment is also filled with a buffer gas. The buffer gas includes: inert gases such as nitrogen or/and argon, buffer gas can play a more stable role in the transmission of control light and signal light, and the volume fraction of the absorbing gas in the mixed gas is not less than 1 percent.
The absorbent gas in this aspect includes: acetylene, methane or/and carbon dioxide. In this embodiment, the absorbing gas may be acetylene gas, the acetylene gas has an excellent photo-thermal coefficient, the acetylene gas in the sealed gas chamber can efficiently absorb energy of an evanescent field and generate heat, and the heated micro-nano optical fiber 132 generates phase modulation on the signal light through a thermo-optic effect.
As shown in fig. 1, the other 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 optical fiber stretcher 410 is connected to the second output end, the polarization controller 420 is connected to the light emitting end of the piezoelectric optical fiber stretcher 410 and connected to the second coupler 50, the length of the optical fiber in the path can be adjusted through the piezoelectric optical 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 one path of signal light modulated by the phase modulator 10 is intersected with the second path of 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, the servo controller 430 connects the detection 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 through the driving of the servo controller 430. This facilitates the collection and processing of the interference signals by the detection assembly 60. Since the operating point of the system is easy to drift due to environmental noise, and a slight shock such as walking nearby may cause the operating point to drift by tens of hundreds of cycles, the operating point needs to be locked to be kept at the maximum slope point. The locking mode depends on the servo controller 430 and the piezoelectric optical fiber stretcher 410, when locking is performed, the optical detector 610 inputs a 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, generates an electrical signal corresponding to the noise signal through a proportional-integral algorithm, and inputs the electrical signal to the piezoelectric optical fiber stretcher 410. The piezoelectric optical 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 optical 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 probe assembly 60 in this embodiment includes a light detector 610, and an oscilloscope 620. The light detector 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. As can be seen, the phase modulation amplitude of the signal light by the all-optical phase modulation system is 2 pi. In addition, the experiment proves the direct proportion relation between the control light power and the photo-thermal phase modulation amplitude, and the result is shown in fig. 6. In the experiment, the modulation frequency of the control light was 1kHz. Further, the phase modulation amplitude and the frequency response of the present phase modulator to different wavelengths in the C + L band, namely 1529, 1550, 1590 and 1625nm, are demonstrated, and the result is shown in fig. 7, in which the control optical power is 148mW, and the phase modulation amplitude of the present modulator to the signal light increases as the control optical modulation frequency decreases.
In summary, in the all-optical phase modulation system based on the gas photothermal effect in the micro-nano fiber provided by the present disclosure, the pump light source 110 of the phase modulator 10 generates the control light that can be modulated, the signal light source generates the signal light, the signal light is divided into two paths by the first coupler, one path combines the signal light and the control light with the signal light to be modulated by the wavelength division multiplexer 120, and then the two paths are input to the micro-nano fiber 132 in the fiber gas chamber 130 through the common end of the wavelength division multiplexer 120. Because the energy of the evanescent field 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 the 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 meanwhile, substances such as dust or air in the external environment are prevented from participating in interaction between an evanescent field in the micro-nano optical fiber 132 and the external environment, so that the heat generation efficiency of the absorptive gas in the photo-thermal effect and the change rate of the refractive index along with heat are fixed. Control light and signal light are input from the tail fiber of the micro-nano optical fiber 132, and the control light is absorbed by an absorptive gas (acetylene gas) through an evanescent field of the control light at the conical region 134 of the micro-nano optical fiber 132 and heats the micro-nano optical fiber 132 through a photo-thermal effect. Energy distribution of the evanescent field of the micro-nano optical fiber 132 and 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 energy originally transmitted inside the optical fiber to leak outside the optical fiber to form the evanescent field and to be transmitted along the optical fiber, and the energy leaked outside the optical fiber has high density and can fully interact with acetylene gas in the gas chamber. Acetylene gas has an excellent photo-thermal coefficient, the acetylene gas in the closed gas chamber can efficiently absorb energy of an evanescent field and generate heat, and the heated micro-nano optical fiber 132 generates phase modulation on signal light through a thermo-optic effect. And packaging the conical region 134 of the micro-nano optical fiber 132 and acetylene gas in the sealed inner cavity 131. The control light and the modulated signal light are output from the tail fiber of the micro-nano optical fiber 132 and then enter the fiber bragg grating 140, so that the control light is reflected back to the micro-nano optical fiber 132 to be absorbed again, and the phase modulation amplitude is enhanced. The remaining control light passes through the common port and the first light-incoming port of the wavelength division multiplexer 120, returns to the port of the circulator 150, and is output from the other port of the circulator 150. The other path of signal light is adjusted through the matching arm component, the two paths of signal light are input to the detection component together after passing through the second coupler, the two paths of signal light generate interference light when being combined, so that interference fringes appear, and when the phase difference of the transmission light in the two optical fibers changes, the interference fringes move. The optical detection assembly receives the change information of the interference fringes and inputs the change information into a proper data processing system to finally obtain the phase modulation of the signal light. The scheme adopts the gas photothermal 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 to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (10)
1. An all-optical phase modulation system based on gas photothermal effect in micro-nano optical fibers is characterized by comprising:
a signal light source for generating signal light;
a first coupler connected to the signal light source and outputting the signal light from a first output terminal and a second output terminal, respectively;
the phase modulator is connected to the first output end and comprises a pump light source and an optical fiber air chamber, and 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, absorptive gas is filled outside the micro-nano optical fiber, 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 through the control light so as to cause the phase change of the signal light;
the input end of the matching arm component is connected with the second output end;
a first input end of the second coupler is connected with the phase modulator, and a second input end of the second coupler is connected with the output end of the matching arm component;
a probe assembly connected to an output of the second coupler.
2. The all-optical phase modulation system based on gas photothermal effect in micro-nano fiber 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 to the light outlet end of the piezoelectric optical fiber stretcher and connected with the second coupler.
3. The all-optical phase modulation system based on gas photothermal effect in micro-nano fiber according to claim 2, wherein the matching arm assembly further comprises: 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 a maximum slope point through the driving of the servo controller.
4. The all-optical phase modulation system based on gas photothermal effect in micro-nano fiber 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 is used for inputting the control light, and the second light inlet end of the wavelength division multiplexer is used for inputting signal light; and
the fiber Bragg grating is arranged at the light outlet end of the 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 area is positioned at two ends of the cone area.
5. The all-optical phase modulation system based on the photothermal effect in the micro-nano fiber according to claim 4, wherein the micro-nano fiber is made of single-mode fiber tapering;
the diameter of the cone area is 0.1-10 microns, and the length of the cone area is 0.1-10 cm.
6. The all-optical phase modulation system based on gas photothermal effect in micro-nano fibers according to claim 4, wherein the pumping light source is connected with the wavelength division multiplexer through an optical fiber.
7. The all-optical phase modulation system based on photothermal effect in micro-nano optical fibers according to claim 4, wherein the pumping light source comprises: a pump light laser 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 outlet end of the amplifier and is used for modulating the intensity of the control light.
8. The all-optical phase modulation system based on gas photothermal effect in micro-nano fiber 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 photothermal effect in micro-nano fibers according to claim 4, wherein the reflection bandwidth of the fiber Bragg grating is 0.1-10 nm, the central 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 in the micro-nano 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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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117074366A (en) * | 2023-10-12 | 2023-11-17 | 朗思传感科技(深圳)有限公司 | Gas sensing device based on micro-nano optical fiber and concentration detection method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117074366A (en) * | 2023-10-12 | 2023-11-17 | 朗思传感科技(深圳)有限公司 | Gas sensing device based on micro-nano optical fiber and concentration detection method |
| CN117074366B (en) * | 2023-10-12 | 2023-12-22 | 朗思传感科技(深圳)有限公司 | Gas sensing device based on micro-nano optical fiber and concentration detection method |
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