JP2008046593A - Method of temperature compensation of optical wavelength filter apparatus and fiber etalon element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of temperature compensation of a light wavelength filter apparatus and a fiber etalon element, with which the temperature dependency of a peak wavelength passing through the fiber etalon element which varies according to temperature is reduced. <P>SOLUTION: The light wavelength filter apparatus includes: a sleeve; the fiber etalon element composed of a rigid material, an optical fiber arranged in the inner hole of the rigid material and reflection films formed on both end faces of the optical fiber; and a pair of ferrules, in which an end of the optical fiber is inserted, which are abutted to both ends of the fiber etalon element, wherein a pressurizing means whose pressurizing force acting against the fiber etalon element via the pair of ferrules varies according to the temperature is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical wavelength filter device having a temperature compensation function and a temperature compensation method for a fiber etalon element.

  An optical interference element and an optical wavelength filter using the same are widely used in multiplexing / demultiplexing devices and various optical measuring instruments in wavelength division multiplexing optical communication (WDM). As these elements or filters, in general, a fiber Bragg grating (FBG) element (for example, see Patent Document 1), a dielectric multilayer film filter (for example, see Patent Document 2), and the like, and a Fabry-Perot etalon. An element (for example, refer to Patent Document 3) is well known.

  A Fabry-Perot etalon element (hereinafter referred to as an etalon element) uses optical multiple reflection between two parallel planes having a reflective film. Compared to the FBG element and the dielectric multilayer filter, The wavelength band of the transmitted light is very narrow.

  The wavelength λ of light transmitted through the etalon element is expressed by the following equation (1).

λ = 2nd / m (1)
Here, n is the refractive index, d is the distance between the reflecting films constituting the etalon element, and m is an arbitrary natural number. That is, equation (1) indicates that only light whose 2nd is an integral multiple of the wavelength λ can pass through the etalon element. Further, the peak shape of the transmission spectrum depends on the reflectance of the reflection film. The higher the reflectance, the narrower the peak width, and the minimum transmitted light amount in the transmission spectrum can be kept low.

  When an etalon element is used, the incident light needs to be a parallel light beam, and a collimator needs to be used to obtain the parallel light beam. Therefore, it is difficult to reduce the size of the entire optical system, and there is a problem that fine adjustment of the optical system is required.

  In order to solve these problems, an optical wavelength filter device having a configuration in which a columnar etalon element (fiber etalon element) including an optical fiber as a central axis is inserted into a split sleeve has been proposed (see, for example, Patent Document 4). ).

  Also, among fiber etalon elements, the one that is fused and fixed so as to wrap the optical fiber by heating and stretching the cylindrical glass rather than the optical fiber being fixed to the cylindrical member with an adhesive or the like, Misalignment with the optical connector plug is reduced. Therefore, Patent Document 5 describes that a transmission spectrum having a sharp peak can be obtained.

  By the way, as described in the equation (1), the transmission wavelength of the etalon element is determined by the refractive index n of the waveguide and the distance d between the reflection films of the etalon element. However, since these two values have independent temperature dependencies, there is a problem that the peak wavelength transmitted through the etalon element is shifted by a temperature change.

So far, for example, in the FBG, a temperature compensation member (see, for example, Patent Documents 6 and 7) has been proposed in order to cancel the temperature dependence of the reflected peak wavelength. The FBG is fixed at two points in a state where tension is applied to these temperature compensation members, and when the temperature rises, the distance between the two fixed points is reduced, so that the tension is relaxed and the peak wavelength reflected by the FBG It is intended to reduce the fluctuations.
JP 2001-305356 A JP-A-11-218617 JP-A-3-45904 Japanese Patent No. 2865620 JP 2006-153986 A JP 2000-347047 A JP 2000-313654 A

  By the way, in the etalon elements of Patent Documents 3 to 5, these optical path lengths S are expressed as S = nd by the refractive index n of the waveguide section and the distance d between the reflection films of the etalon element. When the optical path length S changes due to the above, the peak position of the transmission spectrum shifts. When the environmental temperature of the optical wavelength filter device is changed, the optical path length S is changed by the change of the physical length (d) of the optical interference element caused by the temperature change and the change of the refractive index (n) of the waveguide portion accompanying the temperature change. Change. This peak shift is a big problem for the optical wavelength filter device, and an early solution has been expected.

  However, since the etalon element has a structure in which a tension cannot be applied in advance like the FBG, there is a problem that the mechanism of the temperature compensation member of the FBG cannot be incorporated as it is.

  An object of the present invention is to provide an optical wavelength filter device and a temperature compensation method for a fiber etalon element that can reduce the temperature dependence of the peak wavelength of light transmitted through the fiber etalon element that fluctuates with respect to a temperature change.

  As a result of intensive studies, the present inventors have found that the change in optical path length generated in the etalon element due to a temperature change can be compensated by adjusting the pressure (force for pressing the etalon element).

First, when the environmental temperature of the etalon element is actually changed from −40 ° C. to 85 ° C., the peak of the transmission spectrum increases with an increase in the refractive index of the waveguide due to the temperature change and an increase in the distance between the reflection films due to thermal expansion. It was confirmed that the position shifted to the high wavelength side. In principle, when the waveguide portion is a core portion of a silica fiber, the temperature dependence of the total length, the refractive index, and the refractive index is 1.26 mm, 1.46, 1 × 10 ⁻⁵ / ° C., respectively. If the coefficient of thermal expansion of 5 × 10 ⁻⁷ / ° C., the peak position of the transmission spectrum at the wavelength of 1550 nm can be calculated to shift to the longer wavelength side of 1.42 nm, and the calculated shift amount (1.42 nm) is It was in good agreement with the measured value (about 1.4 nm).

  Next, when pressure is applied to the optical interference element at room temperature, the peak position gradually shifts to the lower wavelength side, and the same shift amount (about 1.4 nm as when the temperature is changed from −40 ° C. to 85 ° C. I was able to make it smaller. This can be compensated for by canceling the increase in the refractive index (n), which changes due to temperature rise, by pressing the physical length (d) of the optical interference element in a reverse direction. It means that.

  In other words, the optical wavelength filter device of the present invention comprises a sleeve, a rigid material inserted into the inner hole of the sleeve, an optical fiber disposed in the inner hole, and a reflection film formed on both end faces of the optical fiber. In an optical wavelength filter device including a fiber etalon element and a pair of ferrules in which one end of the optical fiber is inserted and brought into contact with both ends of the fiber etalon element, a force that presses the fiber etalon element through the pair of ferrules It is characterized by comprising pressing means that changes according to the temperature.

  In the temperature compensation method for the fiber etalon element of the present invention, the fiber etalon element is inserted into the inner hole of the sleeve, and a pair of ferrules in which one end of the optical fiber is inserted are in contact with both ends of the fiber etalon element and pressed. The force for pressing the fiber etalon element through the pair of ferrules by means changes according to the temperature.

  In the optical wavelength filter device of the present invention, the fiber etalon element is pressed by the pressing means through the ferrule, and the pressing force changes according to the temperature, so that the peak wavelength that passes through the fiber etalon element even if the temperature changes Fluctuations can be reduced.

  In other words, as the temperature rises, the refractive index of the waveguide section of the fiber etalon element increases and the distance between the reflecting films increases due to thermal expansion, and the peak wavelength shifts to the longer wavelength side, but the refractive index changes and thermal expansion. As the temperature rises so as to cancel out the pressure, the force is pressed with a larger force, so the shift of the peak wavelength to the longer wavelength side can be reduced.

  The sleeve is generally made of glass, crystallized glass, ceramics, metal or the like. As the sleeve, a cylindrical rigid sleeve or a split sleeve having a slit in the cylinder is generally used.

  The elastic modulus of the sleeve is preferably 10 to 250 GPa. If it is lower than 10 GPa, there is a risk of deformation or bending during pressing, which may cause axial misalignment. Moreover, since the material larger than 250 GPa is expensive, it is not economically preferable. Preferably it is 20-200 GPa, More preferably, it is 30-180 GPa.

  In the fiber etalon element, an optical fiber is inserted and fixed in an inner hole provided in the axial center of a cylindrical rigid material such as glass, crystallized glass, ceramics, or metal. In addition, reflection films are formed on both end faces of the fiber etalon element. As the reflective film, a metal thin film, a dielectric multilayer film, or the like is used. For the formation of the reflective film, sputtering, vapor deposition, CVD, PVD, ion plating, or the like can be used. In particular, since the reflective film has high mechanical strength, a reflective film forming method using a sputtering method is preferable.

The dielectric multilayer film is formed by alternately stacking 4 to 30 layers of high refractive index films such as Nb ₂ O ₅ , Ta ₂ O ₅ and TiO ₂ and low refractive index films such as SiO ₂ , MgF ₂ , SiN and Al ₂ O _3. It is a thing.

  The fiber etalon element is such that when an optical fiber is inserted into an inner hole of a rigid material made of glass or crystallized glass, and the optical fiber is fused and fixed by glass or crystallized glass, the optical fiber is not easily displaced. It is preferable because the connection loss is small, the transmitted peak is not easily split, and the adhesion between the optical fiber and the rigid material is not loosened by the pressing force of the pressing means.

  As the ferrule, a cylindrical rigid material such as glass, crystallized glass, ceramics, or metal having an inner hole in the axial center can be used. It is preferable that the tip of the ferrule is PC (physical contact) polished for connection to the fiber etalon element because the connection loss tends to be small. Further, it may be flat polished.

Further, as a ferrule, the difference (OD _F −ID _S ) between the ferrule whose outer diameter dimension (OD _F ) is slightly smaller than the inner diameter dimension (ID _S ) of the sleeve (for example, the inner diameter dimension (ID _S ) of the sleeve). If a sleeve having an outer diameter (OD _F ) of 1 μm or less is used, the ferrule (optical connector plug) can be held without tilting even when an external force is applied.

  The pressing means is means for applying a pressing force corresponding to a temperature change to the fiber etalon element through a pair of ferrules. Three specific examples are shown below.

  The first form is a pressing means that combines a material having a small thermal expansion coefficient and a material having a large thermal expansion coefficient. Specifically, as shown in FIG. 5, the pressing means uses a material having a small thermal expansion coefficient as the base material 41 and a material having a large thermal expansion coefficient as the pressing parts 42, 42, and uses the pressing parts 42, 42 as the base material. 41, and a pressing force is generated by the difference in thermal expansion between the base material and the pressing component. Due to such a configuration, the distance between the protrusions 42a of the pressing component 42 is reduced as the temperature rises due to the difference in thermal expansion between the base material 41 and the pressing component 42, and the fiber etalon element is pressed through the ferrule. Strength increases. In the figure, a fiber etalon element and a pair of ferrules that come into contact with both ends of the fiber etalon element are collectively referred to as an optical component 43.

  The magnitude of the pressing force is the distance between the pressing components 42 and 42 fixed to the substrate 41, the length of the pressing component 42 in the optical axis direction, the length of the ferrule in the optical axis direction, and the ferrule, the substrate, and the pressing component. It depends on the size of each coefficient of thermal expansion.

  It is preferable that the elastic constants of the low-expansion material base material 41 and the high-expansion material pressing part 42 are 80 GPa or more because they are not easily deformed during pressing and can be pressed efficiently.

Further, it is preferable that the difference between the thermal expansion coefficients of the low-expansion material base material 41 and the high-expansion material pressing part 42 is 1 × 10 ^{−7 to} 370 × 10 ⁻⁷ / ° C. because it can be efficiently pressed. If it is less than 1 × 10 ⁻⁷ / ° C., the dimensions of the low expansion material and high expansion material necessary for temperature compensation increase, and the device shape increases. If it is higher than 370 × 10 ⁻⁷ / ° C., the difference in thermal expansion coefficient is too large, and the joint between the low expansion material and the high expansion material is likely to peel off. Preferably, it is 70 × 10 ^{−7 to} 150 × 10 ⁻⁷ / ° C., more preferably 90 × 10 ^{−7 to} 120 × 10 ⁻⁷ / ° C.

As shown in FIG. 5, it is particularly preferable that the base material 41 has a cylindrical shape in which the fiber etalon element can be built in the inner hole, because the fiber etalon element can be protected. May be. Moreover, the base material 41 may be formed by combining two or more parts. The substrate 41 has a coefficient of thermal expansion of −120 × 10 ^{−7 to} 100 × 10 ⁻ such as Kovar, Invar (registered trademark), cordierite, aluminum titanate, crystallized glass having a β-spodumene solid solution as a main crystal. ^{It is 7} / ° C, and any material having high rigidity can be used. A preferable thermal expansion coefficient is −50 × 10 ^{−7 to} 90 × 10 ⁻⁷ / ° C., and more preferably 10 × 10 ⁻⁷ to 80 × 10 ⁻⁷ / ° C.

  As long as the pressing component basically has a protrusion, a cross-section having a convex shape, an L-shape, or a similar shape can be used. As shown in FIG. 5, when the pressing parts 42, 42 are composed of protrusions 42 a, 42 a and flat parts 42 b, 42 b, the flat parts 42 b, 42 b are fixed to the base material 41, and the protrusions 42 a, 42 a face each other. Fixed to.

The pressing component 42 can be used as long as it has a thermal expansion coefficient of 101 × 10 ^{−7 to} 300 × 10 ⁻⁷ / ° C. and has a high rigidity. For example, aluminum, stainless steel, iron, brass, etc. are used. Is possible. A preferable thermal expansion coefficient is 130 × 10 ⁻⁷ to 250 × 10 ⁻⁷ / ° C., and more preferably 150 × 10 ⁻⁷ to 200 × 10 ⁻⁷ / ° C.

  The base material 41 and the pressing component 42 can be bonded by welding such as YAG welding, screwing each component processed into a screw shape, bonding with an adhesive, or the like.

  The second form is composed of a base material and a pressing part, and the base material is made of a material whose expansion amount is smaller than the total expansion amount of the fiber etalon element and the pair of ferrules (preferably, a negative thermal expansion coefficient). Pressing means). Specifically, as shown in FIG. 6, the pressing means is made of a material (preferably a negative thermal expansion coefficient) that has a smaller expansion amount than the total expansion amount of the fiber etalon element and the pair of ferrules on the base material 51. Is formed into a substantially U-shape having pressing parts 52 at both ends thereof. Therefore, as the temperature rises, the base member 51 has an expansion amount smaller than the total expansion amount of the optical component 53 (preferably, the optical component expands and the base member 51 contracts), thereby the pressing component 52. However, the fiber etalon element can be pressed through the ferrule of the optical component 53. The pressing component 52 may be any material as long as it has rigidity, may be the same material as the substrate 51, and the substrate and the pressing component may be integrally formed. In addition, it is preferable that the base material is made of a material having a negative coefficient of thermal expansion because the temperature compensation of the fiber etalon element is possible even if the total length of the base material is short, and the optical wavelength filter element can be downsized.

Examples of materials having a negative thermal expansion coefficient include zirconium tungstate, hafnium tungstate, β-quartz solid solution ceramics, crystallized glass having a β-quartz solid solution as a main crystal, and a liquid crystal polymer having a thermal expansion coefficient of −1 × 10 ^{−. Any} material having ⁷ to −120 × 10 ⁻⁷ / ° C. can be used.

  The third form is a pressing means having a temperature sensor and a drive unit. That is, this pressing means senses the temperature, and the drive unit works so that an optimal pressing is applied between the ferrules at that temperature. The drive unit is a piezoelectric element, a motor, or the like.

  In the above configuration, it is preferable that a plurality of fiber etalon elements optically connected in series are inserted into the inner hole of the sleeve. In this way, the transmission spectra of the individual fiber etalon elements are overlapped, and a large cutoff rate (PV value) can be obtained with almost the same half-value width as in the case of one fiber etalon element. At this time, it is preferable to use two or three fiber etalon elements. When the number of fiber etalon elements is four or more, the connection loss increases because there are many connection points, and it becomes difficult to accurately match the peak wavelengths of the respective fiber etalon elements, and the manufacturing cost increases accordingly. Because.

  In the above-described configuration, the optical wavelength filter device of the present invention preferably applies a predetermined pressing force (initial load value) to the fiber etalon element at room temperature. In this way, the optical connection between the fiber etalon element and the ferrule or between the fiber etalon elements is unlikely to be impaired. In particular, the initial load value is preferably a load value determined as follows.

  (1) Without using the pressing means, the environmental temperature of the fiber etalon element is changed from −40 ° C. to 85 ° C., and the shift amount of the transmission peak wavelength at each temperature is set with reference to the transmission peak wavelength at −40 ° C. Measure and plot the relationship between temperature and transmission peak wavelength shift as shown in FIG.

  (2) As shown in FIG. 8, mechanically loaded onto the fiber etalon element of the optical wavelength filter device at room temperature, and the transmission peak at each load value with reference to the transmission peak wavelength at −40 ° C. in FIG. The shift amount of the wavelength is measured, and the relationship between the load value and the shift amount of the transmission peak wavelength is plotted.

  (3) The shift amount A of the transmission peak wavelength at room temperature is obtained from the graph of FIG. 7, and a load value B having the same shift amount as the shift amount is derived from the graph of FIG. The initial load value at room temperature is used.

  Hereinafter, the present invention will be described in detail using examples and comparative examples. 1 is a cross-sectional view of the optical wavelength filter device of Examples 1, 3 to 5, and Comparative Example 1, and FIG. 2 is a cross-sectional view of the optical wavelength filter device of Example 2. FIG. 3 is an explanatory diagram showing a transmission peak wavelength measuring apparatus. FIG. 4 is a graph showing the shift amount of the transmission peak wavelength with respect to temperature change in Examples 1, 3 to 5, and Comparative Example 2.

[Example 1]
As shown in FIG. 1, the optical wavelength filter device 10 of Example 1 is configured as follows. A fiber etalon element 12 having a length of 2.52 mm is inserted into the inner hole of the sleeve 11 made of crystallized glass whose main crystal is β-spodumene solid solution. At both ends of the fiber etalon element 12, a ferrule (thermal expansion coefficient is 30 × 10 ⁻⁷ / ° C.) having a length of 6.5 mm into which one end of an optical fiber (thermal expansion coefficient 5 × 10 ⁻⁷ / ° C.) 13 is inserted. ) 14 and 14 are PC-connected in a state of being pressed with a force (initial load value) of 2 kgf at room temperature. These parts are inserted into the inner hole 15a of the outer tube 15 made of Kovar (thermal expansion coefficient is 66 × 10 ⁻⁷ / ° C.) having a length of 32 mm, and the end of the outer tube 15 has a length of 6 mm. The flanges 16 and 16 made of SUS303 (thermal expansion coefficient is 164 × 10 ⁻⁷ / ° C.) are bonded and fixed, and the protruding portion (length 2 mm) 16 a of the flange 16 is in contact with the ferrule 14. The other end of the optical fiber 13 is guided to the outside through a hole (not shown) in the flange 16.

The fiber etalon element 12 has an outer diameter of 1.249 mm and a length of 2.52 mm, and is composed of a dielectric multilayer film in which 12 layers of 6 layers of Nb ₂ O ₅ and SiO ₂ are alternately laminated on both end faces. Each of the reflective films is formed. The fiber etalon element 12 has an optical fiber made of silica glass having an outer diameter of 125 μm at the center, and the optical fiber is fused to an inner hole of a rigid material made of crystallized glass whose main crystal is β-spodumene solid solution. It is fixed.

  The ferrule 14 was made of crystallized glass having a β-spodumene solid solution as a main crystal. The outer diameter is 1.249 mm as in the fiber etalon element 12.

  When the temperature rises, the flange 16 has the protruding portion 16a, and the expansion amount of the flange 16 is larger than the expansion amount of the outer cylindrical tube 15, and therefore the interval between the two flanges 16 and 16 is narrowed. That is, the pair of ferrules 14 and 14 are pressed, and as a result, the force for compressing the fiber etalon element 12 is increased so as to cancel the increase in the refractive index of the waveguide and the expansion of the fiber etalon element 12.

  On the other hand, when the temperature decreases, the amount of contraction of the flange 16 is smaller than the amount of contraction of the outer tube 15, so that the interval between the two flanges 16 and 16 becomes wider. That is, the pressure of the pair of ferrules 14 and 14 is relieved, and as a result, the force for compressing the fiber etalon element 12 is reduced so as to offset the decrease in the refractive index of the waveguide and the contraction of the fiber etalon element 12.

[Example 2]
As shown in FIG. 2, the optical wavelength filter device 20 of the second embodiment is configured as follows. In the inner hole of the sleeve 21 (total length is 2.26 mm, outer diameter is 3 mm, inner diameter is 1.25 mm) made of zirconium tungstate having a negative thermal expansion coefficient (thermal expansion coefficient is −110 × 10 ⁻⁷ / ° C.) A fiber etalon element 22 having a length of 1.26 mm is inserted. At both ends of the fiber etalon element 22, a ferrule (thermal expansion coefficient is 30 × 10 ⁻⁷ / ° C.) 24 having a length of 1 mm into which one end of an optical fiber (thermal expansion coefficient 5 × 10 ⁻⁷ / ° C.) 23 is inserted. , 24 is connected to the PC while being pressed at room temperature with a force of 2 kgf. A fiber etalon element 22 is inserted into an inner hole of a sleeve 21 made of zirconium tungstate having a negative thermal expansion coefficient (thermal expansion coefficient is −110 × 10 ⁻⁷ / ° C.). The ferrules 24 and 24 into which one end of the optical fiber 23 is inserted are PC-connected to both ends of the fiber etalon element 22 while being pressed with a force of 500 gf. The flange 25 is in contact with the ferrule 24 and is fixedly bonded to the end 21 a of the sleeve 21. The other end of the optical fiber 23 is guided to the outside through a hole (not shown) in the flange 25.

  The fiber etalon element 22 and the ferrule 24 constitute an optical wavelength filter device using parts of the same type as those used in the first embodiment.

  When the temperature rises, the sleeve 21 contracts, so that the interval between the two flanges 25, 25 is narrowed. That is, the pair of ferrules 24 and 24 are pressed, and as a result, the force for compressing the fiber etalon element 22 is increased so as to cancel out the expansion of the fiber etalon element 22.

  On the other hand, when the temperature decreases, the sleeve 21 expands, so that the interval between the two flanges 25, 25 becomes wide. That is, the pressure of the pair of ferrules 24 and 24 is relieved, and as a result, the force for compressing the fiber etalon element 22 is reduced so as to cancel the contraction of the fiber etalon element 22.

[Example 3]
The length of the fiber etalon element is 1.26 mm, the length of the ferrule is 5 mm, the length of the outer tube made of Kovar is 27 mm, the length of the flange made of SUS303 is 8 mm (the protrusion is 2 mm), and the reflective film is The structure is the same as that of Example 1 except that a dielectric multilayer film in which 16 layers of Nb ₂ O ₅ and SiO ₂ are alternately stacked is formed.

[Example 4]
Instead of the fiber etalon element 12 of the optical wavelength filter device 10 of the third embodiment, two fiber etalon elements having a length of 1.26 mm are used in series with a PC, and the length of the Kovar outer tube 15 is 30 mm. The configuration is the same as in Example 3 except that the length of the flange 16 made of SUS303 is 9 mm and the length of the protrusion of the flange 16 is 3 mm.

[Example 5]
Instead of the fiber etalon element 12 of the optical wavelength filter device 10 of the third embodiment, three fiber etalon elements having a length of 1.26 mm are connected in series with a PC, and the length of the Kovar outer tube 15 is 34 mm. The configuration is the same as in Example 3 except that the length of the flange 16 made of SUS303 is 10 mm, and the length of the protrusion of the flange 16 is 4 mm.

[Comparative Example 1]
The configuration is the same as that of the first embodiment except that an SUS303 outer tube is used instead of the Kovar outer tube.
[Comparative Example 2]
The configuration is the same as that of the third embodiment except that the outer cylindrical tube 15 and the flange 16 as pressing means are not provided.

  The temperature dependence of the transmission peak wavelength of the optical wavelength filter devices of Examples 1 to 4 and Comparative Examples 1 and 2 was evaluated.

  First, each device was connected as shown in FIG. One of the optical fibers guided to the outside from the optical wavelength filter device 30 is connected to the broadband light source 31 and the other is connected to the optical spectrum analyzer 32. The optical wavelength filter device 30 is disposed in the thermostatic chamber 33.

  Next, infrared light in the 1550 nm band is transmitted from the broadband light source 31, and the transmission spectrum transmitted through the optical wavelength filter device 30 in the temperature environment of −40 to 85 ° C. using the thermostatic chamber 33 is measured by the optical spectrum analyzer 32. The shift amount of the transmission peak wavelength at each temperature was calculated with respect to the transmission peak wavelength at −40 ° C. In addition, about Examples 3-5 and the comparative example 2, the shift amount of the transmission peak wavelength with respect to temperature was plotted in FIG.

  In Examples 1 to 5, the shift amount of the transmission peak wavelength was 300 pm or less, but Comparative Examples 1 and 2 were 1500 pm.

It is sectional drawing which shows the optical wavelength filter apparatus of Examples 1, 3-5, and the comparative example 1. FIG. It is sectional drawing which shows the optical wavelength filter apparatus of Example 2. FIG. It is explanatory drawing which shows the measuring apparatus of a transmission peak wavelength. It is a graph which shows the shift amount of the transmission peak wavelength with respect to the temperature change of Examples 3-5 and Comparative Example 2. It is a key map showing one of the embodiments. It is a key map showing one of the embodiments. It is a graph which shows the behavior of the transmission peak shift amount with respect to temperature when not using a pressing means. It is a graph which shows the behavior of the transmission peak shift amount with respect to a load value at the time of applying mechanical load.

Explanation of symbols

10, 20, 30 Optical wavelength filter device 11, 21 Sleeve 12, 22 Fiber etalon element 13, 23 Optical fiber 14, 24 Ferrule 15 Outer tube 15a Inner hole 16, 25 Flange 16a Protrusion 21a End 31 Broadband light source 32 Light Spectrum analyzer 33 Constant temperature bath 41, 51 Base material 42, 52 Pressed part 42a Projection part 42b Plane part 43, 53 Optical part

Claims (12)

  A fiber etalon element comprising a sleeve, a rigid material, an optical fiber disposed in the inner hole of the sleeve, and reflection films formed on both end faces of the optical fiber, and one end of the optical fiber are inserted. An optical wavelength filter device comprising a pair of ferrules that are in contact with both ends of the fiber etalon element, comprising a pressing means for changing the force for pressing the fiber etalon element through the pair of ferrules according to the temperature. An optical wavelength filter device comprising:   2. The optical wavelength according to claim 1, wherein the fiber etalon element is formed by inserting an optical fiber into an inner hole of a rigid material made of glass or crystallized glass, and being fused and fixed by glass or crystallized glass. Filter device.   The optical wavelength filter device according to claim 1 or 2, wherein the elastic modulus of the sleeve is 10 to 250 GPa.   The optical wavelength filter device according to any one of claims 1 to 3, wherein the pressing means includes a base material of a low expansion material and a pressing component of a high expansion material.   The optical wavelength filter device according to claim 4, wherein the elastic constant of the base material of the low expansion material and the pressing part of the high expansion material is 80 GPa or more. 5. The optical wavelength filter device according to claim 4, wherein the difference in thermal expansion coefficient between the low expansion material and the high expansion material is 1 × 10 ^{−7 to} 370 × 10 ⁻⁷ / ° C. 6. A base material of a low expansion material having a thermal expansion coefficient of −120 × 10 ^{−7 to} 100 × 10 ⁻⁷ / ° C. and a high expansion material having a thermal expansion coefficient of 101 × 10 ^{−7 to} 300 × 10 ⁻⁷ / ° C. are used. The optical wavelength filter device according to claim 4, wherein   The pressing means is composed of a base material and a pressing part, and the base material is made of a material whose expansion amount is smaller than the total expansion amount of the fiber etalon element and the pair of ferrules. The optical wavelength filter device according to any one of the above.   9. The optical wavelength filter device according to claim 8, wherein the substrate is made of a material having a negative coefficient of thermal expansion. The optical wavelength filter device according to claim 9, wherein the substrate has a thermal expansion coefficient of −1 × 10 ⁻⁷ to −120 × 10 ⁻⁷ / ° C.   The optical wavelength filter device according to any one of claims 1 to 10, wherein a plurality of fiber etalon elements optically connected in series are inserted into an inner hole of a sleeve.   A fiber etalon element is inserted into the inner hole of the sleeve, a pair of ferrules formed by inserting one end of the optical fiber abuts both ends of the fiber etalon element, and the fiber etalon element is pressed by the pressing means through the pair of ferrules. A temperature compensation method for a fiber etalon element, characterized in that the force varies with temperature.

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