A fiber F-P cavity tunable filter

Abstract

The present invention discloses an optical fiber F-P cavity tunable filter. The piezoelectric ceramic device in the tunable filter of the present invention is a hollow tubular structure. The input optical fiber ferrule seat and the output optical fiber ferrule seat are respectively fixed at the two ends of the piezoelectric ceramic device. The piezoelectric ceramic device is arranged in a hollow shell, and the horizontal axis of the hollow shell is parallel to the axis of the tubular piezoelectric ceramic. A spring is arranged between the outer end of the optical fiber ferrule seat and the adjacent end in the hollow shell. A temperature sensing element is arranged in the hollow shell. A cooling element is arranged at the bottom of the outer part of the hollow shell. A heat sink is arranged at the bottom of the cooling element. A heat preservation material is arranged outside the hollow shell. The advantages of the present invention are that it can overcome the influence of the piezoelectric ceramic length change on its performance in the prior art; it can better reduce the difficulty of preparation and the manufacturing cost; it has the advantages of high control accuracy, fast thermal response and low power consumption, and makes the tunable range larger, and can reduce the voltage amplitude of driving the piezoelectric ceramic.

Description

Technical Field

[0001] The present invention relates to a filter, in particular to an adjustable optical fiber F-P filter. The optical fiber F-P cavity tunable filter of the present invention comprises: an input optical fiber and an output optical fiber, two optical fiber cores inserted into the input optical fiber and the output optical fiber respectively, and a piezoelectric ceramic device. Background Art

[0002] With the widespread application of optical fiber sensing and transmission technology, devices for tuning the wavelength of light have also received increasing attention. Due to its unique advantages such as high precision, fast tuning speed, and small size, tunable optical fiber F-P filters have been widely used and have become a commonly used device. Although there are many forms of existing tunable optical fiber F-P filters, they generally have the disadvantages of high production costs, high processing difficulties, and large differences in their characteristics. Secondly, the existing tunable optical fiber F-P filters need to further improve their working stability and reduce performance changes caused by temperature changes.

[0003] Chinese invention patent 200910071000X discloses a method and device for nonlinear testing of tunable optical filters using FP etalon. The device includes four parts: a tunable laser and optical power module, a test module based on a tunable optical filter, an FP etalon module, and a central processing module. The FP etalon can provide multiple reference wavelengths in a large range. The wavelength-voltage relationship of the tunable optical filter is fitted using a polynomial fitting method, which can characterize the wavelength response characteristics of the tunable optical filter and realize the study of the nonlinear relationship between the PZT driving voltage and the transmission band of the optical filter in the tunable optical filter. The patented method provides multiple reference wavelengths, which can improve the detection sensitivity of the system.

[0004] Chinese invention patent 200810106218X discloses a tunable fiber FP cavity filter, including: a package box made of metal or ceramic material; a semiconductor refrigerator fixed in the package box; a structural block, piezoelectric ceramics, a temperature measuring element and a heat-resistant material fixed on the semiconductor refrigerator; a sheath sealed by an epoxy resin adhesive material and fixed on the structural block with a spherical crown through hole; a first optical fiber fixed in the sheath by a first optical fiber pin; a second optical fiber fixed in the sheath by a second optical fiber pin; and an FP cavity formed by the first optical fiber and the second optical fiber coated at the end face. According to the patent, this tunable fiber FP filter has the advantages of high resolution, large dynamic range, fast response speed, stable operation, etc., which can improve the performance of the FP filter.

[0005] Chinese invention patent application 2018101031908 discloses a temperature-insensitive device for a tunable optical fiber FP filter, comprising a paired optical fiber assembly, a sleeve, a temperature compensation device and a displacement device with temperature compensation, wherein the paired optical fiber assembly is installed in the sleeve and at least one end protrudes from the sleeve, the temperature compensation device comprises a temperature compensation frame and a first sleeve connection frame, the first sleeve connection frame is detachably installed between the temperature compensation frame and the protruding end of any optical fiber assembly, the displacement device with temperature compensation comprises a displacement drive plate, a displacement drive temperature compensation plate, a second sleeve connection frame and an adapter plate, the displacement device with temperature compensation is installed on the sleeve through the adapter plate and corresponds to the position of the optical fiber assembly in the sleeve, and the second sleeve connection frame is detachably installed between the displacement drive plate and the displacement drive temperature compensation plate. This technical content can solve the problem of device sensitivity to temperature, improve the use environment of the tunable optical fiber FP filter, and reduce the complexity of the device's external control circuit.

[0006] Chinese invention patent 2015101528103 discloses an adjustable optical fiber FP filter, the FP cavity of the filter is an elastic body, a through hole is opened in the middle, a ceramic ferrule is inserted at each end, and an optical fiber is inserted inside the ceramic ferrule; an annular piezoelectric ceramic driving element and an annular temperature compensation ring are sequentially sleeved on the outside of the elastic body; the annular piezoelectric ceramic driving element performs telescopic movement under the drive of voltage, and when it stretches, the thrust on both sides acts on the elastic body, so that the elastic body is extended, and the cavity length of the FP cavity becomes longer. When the annular piezoelectric ceramic driving element contracts, the cavity length of the FP cavity becomes shorter, so that the wavelength changes with the change of the cavity length. The present invention realizes precise adjustment of the cavity length through piezoelectric ceramic drive to achieve the purpose of wavelength tuning, and the structure is compact, and the structure itself has a temperature compensation function.

[0007] The existing technical solutions all have the disadvantages of high production cost and great processing difficulty, and their ability of compensation adjustment is also insufficient. Secondly, the working principle of the optical fiber F-P cavity tunable filter is: by changing the size of the driving voltage of the piezoelectric ceramic, changing the cavity length L of the FP cavity to achieve the purpose of tunability, but when the cavity length of the F-P cavity changes, the friction between the optical fiber ferrule and the piezoelectric ceramic will make its movement unstable, so that the performance of the adjustable optical fiber F-P cavity filter is affected. On the other hand, there is a displacement difference between the piezoelectric ceramic boost curve and the buck curve, and this displacement difference will change with the change of the voltage variation range. The smaller the driving voltage, the smaller the displacement difference will be, which also affects the performance of the adjustable optical fiber F-P cavity filter. In addition, increasing the driving voltage of the piezoelectric ceramic will also cause the temperature of the device to rise, thereby affecting its performance. Summary of the invention

[0008] The invention provides an optical fiber F-P cavity tunable filter which can overcome the shortcomings of the prior art.

[0009] As in the prior art, an optical fiber F-P cavity tunable filter of the present invention also includes: an input optical fiber and an output optical fiber, two optical fiber ferrules into which the input optical fiber and the output optical fiber are respectively inserted, and a piezoelectric ceramic device. A particularly optical fiber F-P cavity tunable filter includes: an input optical fiber and an output optical fiber, two optical fiber ferrules into which the input optical fiber and the output optical fiber are respectively inserted, and a piezoelectric ceramic device, characterized in that the piezoelectric ceramic device of the present invention is a tubular structure, and the two ends of the tubular structure piezoelectric ceramic device are respectively provided with an input optical fiber ferrule and an output optical fiber ferrule with the input optical fiber and the output optical fiber, the outer ends of the input ferrule and the output optical fiber are respectively fixed to the two ends of the piezoelectric ceramic device, the piezoelectric ceramic device and the optical fiber ferrules arranged at both ends are both arranged in a hollow shell, and the horizontal axis of the hollow shell is parallel to the axis of the tubular piezoelectric ceramic, a spring is arranged between the outer end of at least one optical fiber ferrule seat and the adjacent end in the hollow shell, a temperature sensing element and a cooling element are arranged in the hollow shell, and a heat-insulating material is arranged outside the hollow shell.

[0010] Preferably, in an optical fiber F-P cavity tunable filter of an embodiment of the present invention, the input optical fiber ferrule and the output optical fiber ferrule are respectively arranged in a ferrule seat made of thermally stable material and having a flange at one end, the piezoelectric ceramic device is located between the flanges of the two ferrule seats, and each ferrule seat is fixed to the ceramic seat, each optical fiber ferrule is fixed to the corresponding optical fiber ferrule seat, and a spring is arranged between the outer end of the optical fiber ferrule seat and the adjacent end in the hollow shell.

[0011] Preferably, in another embodiment of the optical fiber F-P cavity tunable filter of the present invention, the input and output optical fiber ferrules are arranged in a bracket with a flange in the middle thereof, the two ends of the bracket are respectively fixed to two ferrule seats made of thermally stable materials and provided with flanges at the ends, a piezoelectric ceramic device is respectively arranged between the flange of the input ferrule seat and the flange of the bracket and between the flange of the output ferrule seat and the flange of the bracket, and a spring is respectively arranged between the outer ends of the input ferrule seat and the output ferrule seat and the housing, wherein: each ferrule seat and the combined ferrule, each ferrule seat and the combined piezoelectric ceramic, each piezoelectric ceramic and the bracket are fixedly connected to each other. The bracket of the present invention can be made of a metal material with good thermal stability, and the fixed connection can be fixed to each other by bonding.

[0012] Preferably, in the optical fiber F-P cavity tunable filter of the present invention, the input optical fiber ferrule seat and the output optical fiber ferrule seat are made of cemented carbide material or ceramic material respectively.

[0013] Preferably, in the optical fiber F-P cavity tunable filter of the present invention, the cross-sectional area S of the piezoelectric ceramic and the compensation elongation ΔL and the piezoelectric ceramic material satisfy the following relationship:

[0014] △L =Qr P+P 2 S / ε0K

[0015] Where: △L is the elongation of the piezoelectric ceramic; P is the internal polarization strength of the piezoelectric ceramic; ε0 is the dielectric constant in a vacuum; Qr is the residual charge after polarization; S is the cross-sectional area of ​​the piezoelectric ceramic; K is the elastic modulus of the piezoelectric ceramic laminate.

[0016] More preferably, the fiber FP cavity tunable filter of the present invention has a cooling element which is a semiconductor cooling plate, a heat sink is arranged under the semiconductor cooling element, and the heat sink is arranged at a heat dissipation "window" of the thermal insulation material outside the hollow shell.

[0017] The present invention has the following advantages:

[0018] 1) The present invention provides a spring between the insertion end of the input optical fiber ferrule and the hollow shell, which can overcome the influence of the piezoelectric ceramic length change on its performance in the prior art. At the same time, the spring provided in the present invention applies a preload force to the piezoelectric ceramic, which can greatly improve the performance of the piezoelectric ceramic and improve the stability of the F-P cavity length change process;

[0019] 2) Using thermally stable materials such as ceramics or cemented carbide to make the ferrule seat can effectively reduce the difficulty of its preparation and reduce the manufacturing cost;

[0020] 3) In the present invention, the refrigeration element and the heat sink thereunder are arranged at a small heat dissipation "window" of the heat insulation material outside the hollow shell, which can overcome the shortcomings of the prior art such as long refrigeration and cooling time and poor temperature control effect. The use of semiconductor refrigeration elements also has the advantages of high control accuracy, fast thermal response and low power consumption;

[0021] 4) The present invention limits the piezoelectric ceramic material, cross-sectional area and elongation of the piezoelectric ceramic, thereby increasing the tunable range and reducing the voltage amplitude for driving the piezoelectric ceramic.

[0022] 5) In particular, the present invention has a structure with two piezoelectric ceramics, which can reduce the driving voltage of a single piezoelectric ceramic, thereby reducing the displacement difference between the voltage-increasing curve and the voltage-decreasing curve, and further improving its performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the first embodiment of the present invention.

[0024] Figure 2 This is a schematic structural diagram of the second embodiment of the present invention.

[0025] Figure 3The driving voltage (boost curve and buck curve) of the piezoelectric ceramic device and the FP cavity elongation change curve, where the horizontal axis is the driving voltage and the vertical axis is the FP cavity length change. The upward arrow curve in the curve is the boost curve, and the downward arrow curve is the buck curve.

[0026] Figure 4 for Figure 1 The embodiment of the tunable fiber F-P cavity filter of the embodiment and the length curve of the driving voltage and the FP cavity length change of the prior art, wherein: A is the prior art (i.e., the displacement curve without spring), B is Figure 1 Example.

[0027] Figure 5 This is the displacement-piezoelectric ceramic driving voltage curve of the FP cavity length of the prior art (i.e., without a spring).

[0028] Figure 6 The displacement-voltage curve of the FP cavity length after the spring is added in the present invention.

[0029] Figure 7 For the present invention Figure 2 The displacement-voltage curve of the FP cavity length after setting a spring, increasing the cross-section of the piezoelectric ceramic, and setting two piezoelectric ceramics in the embodiment shown in FIG.

[0030] Figure 8 For the present invention Figure 2 A displacement-voltage curve comparison diagram of the tunable fiber FP cavity filter of the embodiment and the FP cavity length of the prior art is shown.

[0031] In the accompanying drawings: input optical fiber 1, output optical fiber 2, input optical fiber ferrule 3, output optical fiber ferrule 4, output optical fiber holder 5 (right), input optical fiber holder 6 (left), piezoelectric ceramic device 7 (7a and 7b), housing 8, spring 9 (9a and 9b), semiconductor cooling sheet 10, heat sink 11, temperature sensor 12, optical fiber rubber sheath 13, thermal insulation layer 14, bracket 15. DETAILED DESCRIPTION

[0032] The present invention is explained below in conjunction with embodiments.

[0033] Figure 1 The best embodiment of the present invention is composed of an input optical fiber 1, an output optical fiber 2, an input optical fiber ferrule 3, an output optical fiber ferrule 4, an output optical fiber ferrule seat (right) 5, an input optical fiber ferrule seat 6 (left), a piezoelectric ceramic device 7, a housing 8, a spring 9, a semiconductor refrigeration sheet 10, a heat sink 11, a temperature sensor 12, an optical fiber rubber sheath 13, and a thermal insulation layer 14, wherein the output optical fiber ferrule seat 5 and the input optical fiber ferrule seat 6 are both made of thermally stable materials, such as ceramic materials or cemented carbide materials.

[0034] Depend on Figure 1 It can be seen that the two ends of the tubular piezoelectric ceramic device 7 are respectively fixed with an input ferrule seat 6 and an output ferrule seat 5, and the fixing method can be fixed by bonding. The input ferrule 3 and the output ferrule 4 are respectively inserted into the input ferrule seat 6 and the output ferrule seat 5. The interval between the input ferrule 3 and the output ferrule 4 is determined by the device spectrum signal. During use, the gap is adjusted by changing the size of the driving voltage of the piezoelectric ceramic, and the end faces of the ferrules 3 and 4 and the end faces of the input optical fiber 1 and the output optical fiber 2 therein are plated with a high reflection film to form an FP cavity. The housing 8 of this embodiment is made of heat-conducting metal material, and a semiconductor cooling plate 10 is arranged at the bottom of the outer surface, and a heat sink 11 is arranged at the bottom of the semiconductor cooling plate 19. The flatness of the contact surface with the semiconductor cooling plate 10 is not greater than 0.03, and the contact surface is evenly coated with heat-conducting silica gel to ensure good heat conduction between the two. A temperature sensor 12 is also arranged in the housing 8 to detect temperature changes and provide temperature control signals. The outer part of the housing 8 is wrapped with a heat-insulating layer 14 of heat-insulating material, and a small "window" is provided in the heat-insulating layer 14 for arranging the heat sink 11. Such a structure can not only play the role of energy storage, but also facilitate heat dissipation.

[0035] The application of the best embodiment of the present invention and the comparison with the prior art are as follows:

[0036] Because there is a displacement difference between the step-up curve and the step-down curve of the electric ceramic. At the same voltage value, there is a significant difference in the displacement values ​​on the rising curve and the falling curve, and this displacement difference will change with the change of the voltage variation range. The smaller the driving voltage, the smaller the displacement difference will be. The hysteresis of piezoelectric ceramics is generally about 10%~15% of the displacement value corresponding to a given voltage. In order to make the performance of the tunable filter stable, the hysteresis of the piezoelectric ceramic must be solved first. While meeting the tuning range requirements, the driving voltage amplitude is reduced to control the hysteresis. In the prior art, reducing the driving voltage amplitude will reduce the elongation △L of the piezoelectric ceramic, making the tunable width narrower, see the data in Table 1.

[0037] Table 1

[0038]

[0039] In this embodiment, in order to solve this problem, the cross-sectional area S of the piezoelectric ceramic is increased to compensate for the elongation ΔL. The relationship between the displacement of the piezoelectric ceramic is:

[0040] △L=Q r P+P 2 S / ε0K

[0041] Where: △L is the elongation of the piezoelectric ceramic; P is the internal polarization strength of the piezoelectric ceramic; ε0 is the dielectric constant in a vacuum; Qr is the residual charge after polarization; S is the cross-sectional area of ​​the piezoelectric ceramic; K is the elastic modulus of the piezoelectric ceramic laminate.

[0042] On the other hand, since the displacement of the piezoelectric ceramic 7 decreases with the increase of temperature, the length L of the FP cavity changes, causing the central wavelength of the tunable optical fiber F-P cavity filter to drift, resulting in unstable performance. This requires that the temperature inside the housing 8 is in a constant temperature state. The current practice is to install the semiconductor refrigeration plate 10 inside the housing 8. When cooling, the hot surface dissipates heat through the housing 8, so that the heat is dissipated to the outside and the inside at the same time. This extends the cooling time, the temperature control effect is poor, and the power consumption is large. Therefore, in this embodiment, the semiconductor refrigeration plate 10 is installed outside, and the housing 8 is equipped with a heat insulation layer 14 made of heat insulation materials such as glass fiber wool and polyurethane, and a heat dissipation window is set in the insulation layer 14 for setting the heat sink 11 set below the semiconductor refrigeration element 10. This greatly reduces the influence of external temperature changes on the temperature changes inside the housing 8, and then the constant temperature inside the housing 8 is achieved through the semiconductor refrigeration plate 10 and the temperature sensor 12. In this way, the temperature control accuracy is high, the effect is good, and the power consumption is small. The stability of the tunable FP cavity filter is improved to a greater extent.

[0043] In the prior art, since the tunable optical fiber F-P cavity filter is tuned by changing the F-P cavity length L. When the piezoelectric ceramics are stretched and contracted, the displacement of each point is different, causing the piezoelectric ceramic input end to tilt due to the force of the extension. Since the piezoelectric ceramic left seat 6 and the input optical fiber ferrule 3 are fixed, the input optical fiber ferrule 3 is also subject to this force, so that when the F-P cavity length L changes, the friction between the input optical fiber ferrule 3 and the positioning sleeve 5 increases, the movement becomes unstable, and the performance of the tunable optical fiber F-P cavity filter deteriorates. Therefore, the present invention adds a spring 9 to prevent the piezoelectric ceramic left seat 3 from tilting due to the force.

[0044] In dynamic applications, the thrust and tension of piezoelectric ceramics exist simultaneously, and the thrust is much greater than the tension, so the tension has a great influence on piezoelectric ceramics. When piezoelectric ceramics are used in dynamic applications, the two forces appear alternately. Therefore, a spring is added to the piezoelectric ceramic left seat 6 to give the piezoelectric ceramics a preload force. After the spring 9 is added to the present invention, the displacement of the piezoelectric ceramic 7 is reduced to L1, see Figure 3 As shown, the working stability of the tunable fiber F-P cavity filter is greatly improved.

[0045] Figure 2 The embodiment of Figure 1The improvement of the embodiment is also a preferred embodiment of the present invention. In this embodiment, the input ferrule 3 and the output ferrule 4 are inserted into the input ferrule seat 6 and the output ferrule seat 5 respectively, and the input ferrule seat 6 and the output ferrule seat 5 are respectively arranged in a tubular bracket 15 with a flange in the middle. The piezoelectric ceramic device 7 is composed of two independent tubular piezoelectric ceramic tubes 7a and 7b, and the piezoelectric ceramic tubes 7a and 7b are respectively fixedly arranged between the ferrule seat 6 and the left side of the bracket 15 and between the ferrule seat 5 and the right side of the bracket 15, see the attached Figure 2 , and are fixed to each other by bonding. The interval between the input ferrule 3 and the output ferrule 4 is determined by the device spectrum signal. During use, the gap is adjusted by changing the size of the driving voltage of the piezoelectric ceramic, and the end faces of the ferrules 3 and 4 and the end faces of the input optical fiber 1 and the output optical fiber 2 therein are plated with a high reflection film to form an FP cavity. As in Example 1, the shell 8 of this embodiment is made of a heat-conducting metal material, and a semiconductor refrigeration plate 10 is arranged at the bottom of the outer surface, and a heat sink 11 is arranged at the bottom of the semiconductor refrigeration plate 19. The flatness of the contact surface with the semiconductor refrigeration plate 10 is not greater than 0.03, and the contact surface is evenly coated with heat-conducting silica gel to ensure good heat conduction between the two. A temperature sensor 12 is also arranged in the shell 8 for detecting temperature changes and providing temperature control signals. A heat-insulating layer 14 of heat-insulating material is wrapped on the outside of the shell 8, and a small "window" is arranged in the heat-insulating layer 14 for arranging the heat sink 11. Such a structure can not only play the role of energy storage, but also facilitate heat dissipation.

[0046] The application of the best embodiment of the present invention and the comparison with the prior art are as follows:

[0047] Because there is a displacement difference between the step-up curve and the step-down curve of the electric ceramic. At the same voltage value, there is a significant difference in the displacement values ​​on the rising curve and the falling curve, and this displacement difference will change with the change of the voltage variation range. The smaller the driving voltage, the smaller the displacement difference will be. The hysteresis of piezoelectric ceramics is generally around 10%~15% of the displacement value corresponding to a given voltage. In order to make the performance of the tunable filter stable, the hysteresis of the piezoelectric ceramic must be solved first. While meeting the tuning range requirements, the driving voltage amplitude is reduced to control the hysteresis. In the prior art, reducing the driving voltage amplitude will reduce the elongation △L of the piezoelectric ceramic, making the tunable width narrower. See Figures 3 to 6 , and Table 1.

[0048] As mentioned above, the present embodiment also adopts the same technical measures as the previous embodiment, by increasing the cross-sectional area S of the piezoelectric ceramic to compensate for the elongation ΔL. The relationship between the displacement of the piezoelectric ceramic is shown in the following formula:

[0049] △L=Q r P+P 2 S / ε0K

[0050] Where: △L is the elongation of the piezoelectric ceramic; P is the internal polarization strength of the piezoelectric ceramic; ε0 is the dielectric constant in a vacuum; Qr is the residual charge after polarization; S is the cross-sectional area of ​​the piezoelectric ceramic; K is the elastic modulus of the piezoelectric ceramic laminate.

[0051] The displacement of the piezoelectric ceramics 7a and 7b of the present invention decreases with the increase of temperature, so that the FP cavity length L changes, causing the central wavelength of the tunable optical fiber F-P cavity filter to drift, resulting in unstable performance. This embodiment also adopts the same measures as the previous embodiment to obtain high temperature control accuracy, good effect, low power consumption, and improve the stability of the tuned FP cavity filter to a greater extent.

[0052] In the prior art, since the tunable optical fiber F-P cavity filter is tuned by changing the F-P cavity length L. When the piezoelectric ceramics are stretched and contracted, there are differences in the displacement of each point, causing the input end of the piezoelectric ceramics to tilt due to the force of the extension. Since the input optical fiber ferrule seat 6 and the output optical fiber ferrule seat 5 are respectively fixed to the input optical fiber ferrule 3 and the output optical fiber ferrule 4, the input optical fiber ferrule 3 and the output optical fiber ferrule 4 are also subject to this force, so that when the F-P cavity length L changes, the friction between the input optical fiber ferrule 3 and the positioning axis of the bracket 12 increases, the movement becomes unstable, and the performance of the tunable optical fiber F-P cavity filter deteriorates. The present invention thus adds springs 9 and 10 to prevent the piezoelectric ceramic left seat 3 from tilting due to force, and pressure-sensitive ceramics are set at both ends, so that the unidirectional displacement becomes smaller, the tilting effect is smaller, and the movement is more stable.

[0053] Since in dynamic applications, the thrust and tension of piezoelectric ceramics exist simultaneously, the thrust is much greater than the tension, and the tension has a great influence on the piezoelectric ceramics. When piezoelectric ceramics are used in dynamic applications, the two forces appear alternately. Therefore, springs are added to the input fiber optic ferrule seat 6 and the output fiber optic ferrule seat 5 to give the piezoelectric ceramics a preload force. After adding springs 9a and 9b, the present invention sets two piezoelectric ceramics 7a and 7b. Under the same displacement value, the displacement difference becomes smaller △L2<△L1, so that the signal fineness is better, the driving voltage becomes smaller UB<UA, and the influence of heat on it is reduced, see Figure 3 As shown, the working stability of the tunable fiber F-P cavity filter is greatly improved.

Claims

1. An optical fiber F-P cavity tunable filter, comprising: An input optical fiber and an output optical fiber, an input optical fiber ferrule and an output optical fiber ferrule into which the input optical fiber and the output optical fiber are respectively inserted, and a piezoelectric ceramic device, characterized in that the piezoelectric ceramic device is a tubular structure, and the two ends of the tubular piezoelectric ceramic device are respectively provided with an input optical fiber ferrule seat and an output optical fiber ferrule seat, and the input optical fiber ferrule seat and the output optical fiber ferrule seat are respectively fixed to the two ends of the piezoelectric ceramic device, the piezoelectric ceramic device and the input optical fiber ferrule seat and the output optical fiber ferrule seat provided at the two ends are all arranged in a hollow shell, and the horizontal axis of the hollow shell is parallel to the axis of the piezoelectric ceramic device, a spring is arranged between the outer end of at least one optical fiber ferrule seat and the adjacent end in the hollow shell, a temperature sensing element is arranged in the hollow shell, a refrigeration element and a heat preservation material are arranged outside the hollow shell, a heat sink is arranged at the bottom of the refrigeration element, and the heat sink is arranged at a heat dissipation window of the heat preservation material outside the hollow shell.

2. The optical fiber F-P cavity tunable filter according to claim 1, characterized in that: The input fiber optic ferrule and the output fiber optic ferrule are respectively arranged in an input fiber optic ferrule seat and an output fiber optic ferrule seat, each of which has a flange at one end and is made of a thermally stable material. The piezoelectric ceramic device is located between the flanges of the input fiber optic ferrule seat and the output fiber optic ferrule seat, and the input fiber optic ferrule seat and the output fiber optic ferrule seat are fixed to the piezoelectric ceramic device, and the input fiber optic ferrule and the output fiber optic ferrule are fixed to the corresponding input fiber optic ferrule seat and the output fiber optic ferrule seat.

3. The optical fiber F-P cavity tunable filter according to claim 1, characterized in that: The piezoelectric ceramic device is composed of two independent tubular piezoelectric ceramic tubes. The input optical fiber ferrule and the output optical fiber ferrule are arranged in a tubular bracket with a flange in the middle. The two ends of the bracket are respectively provided with an input optical fiber ferrule seat and an output optical fiber ferrule seat made of heat-stable material and having flanges at the ends. A piezoelectric ceramic tube is respectively arranged between the flange of the input optical fiber ferrule seat and the flange of the bracket and between the flange of the output optical fiber ferrule seat and the flange of the bracket. Springs are respectively arranged between the outer ends of the input optical fiber ferrule seat and the output optical fiber ferrule seat and the hollow shell. The input optical fiber ferrule seat and the output optical fiber ferrule seat are fixed to the combined piezoelectric ceramic tubes, and each piezoelectric ceramic tube is fixed to the bracket.

4. The optical fiber F-P cavity tunable filter according to claim 2 or 3, characterized in that: The input optical fiber ferrule seat and the output optical fiber ferrule seat are respectively made of hard alloy material or ceramic material.

5. The optical fiber F-P cavity tunable filter according to claim 4, characterized in that: The cross-sectional area S and elongation △L of the piezoelectric ceramic device satisfy the following relationship: △L=Q r P+P 2 S / ε0K Where: △L is the elongation of the piezoelectric ceramic device; P is the internal polarization strength of the piezoelectric ceramic device; ε0 is the dielectric constant in vacuum; Q r is the residual charge after polarization; S is the cross-sectional area of ​​the piezoelectric ceramic device; K is the elastic modulus of the piezoelectric ceramic device.

6. The optical fiber F-P cavity tunable filter according to claim 1, characterized in that: The cooling element is a semiconductor cooling sheet.

Images