JP2005162602A - Method for manufacturing member for temperature compensation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a member for temperature compensation having a low thermal expansion hysteresis and also a high environmental stability and capable of manufacturing at a low cost, and to provide an optical communication device using such a member for temperature compensation. <P>SOLUTION: In the method for manufacturing the member for temperature compensation composed of a polycrystal consisting of a β-quartz solid solution or a β-eucryptite solid solution as a main crystal and in which the interplanar spacing of the crystal plane giving the main peak in an X-ray diffraction measurement is lower than 3.52Å, the polycrystal is prepared by sintering the powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a temperature compensating member having a negative coefficient of thermal expansion and an optical communication device using the same.

  With the progress of optical communication technology, networks using optical fibers are being rapidly established. In a network, wavelength multiplexing technology that transmits light of a plurality of wavelengths at once is used, and wavelength filters, couplers, waveguides, and the like are becoming important devices.

  Some devices of this type change their characteristics depending on the temperature, which hinders outdoor use. Therefore, a technology that keeps these device characteristics constant regardless of temperature changes, so-called temperature Compensation technology is needed.

  A typical optical communication device that requires temperature compensation is a fiber Bragg grating (hereinafter referred to as FBG). An FBG is a device in which a refractive index change in a lattice shape is formed in the core of an optical fiber, that is, a so-called grating, and reflects light of a specific wavelength according to the relationship shown in Equation 1 below. It has characteristics. For this reason, it is attracting attention as an important optical device in an optical communication system of a wavelength division multiplex transmission system in which optical signals having different wavelengths are multiplexed and transmitted through one optical fiber.

Here, λ represents the reflection wavelength, n represents the effective refractive index of the core, and Λ represents the lattice spacing of the portion where the refractive index is changed in a lattice shape.

  However, such an FBG has a problem that the reflection wavelength fluctuates when the ambient temperature changes. The temperature dependence of the reflection wavelength is represented by the following formula 2 obtained by differentiating the formula 1 with the temperature T.

(∂Λ / ∂T) / Λ in the second term on the right side of Equation 2 corresponds to the thermal expansion coefficient of the optical fiber, and its value is approximately 0.6 × 10 ⁻⁶ / ° C. On the other hand, the first term on the right side is the temperature dependence of the refractive index of the core portion of the optical fiber, and its value is approximately 7.5 × 10 ⁻⁶ / ° C. That is, it can be seen that the temperature dependence of the reflection wavelength depends on both the refractive index change of the core part and the change of the lattice spacing due to thermal expansion, but most is caused by the temperature change of the refractive index.

  As a means for preventing such fluctuations in the reflection wavelength, a method is known in which a component caused by a change in refractive index is canceled by applying a tension according to a temperature change to the FBG and changing the lattice spacing. .

  As a specific example of this method, for example, a method of fixing the FBG to a temperature compensating member in which a material such as an alloy or quartz glass having a small thermal expansion coefficient and a metal such as aluminum having a large thermal expansion coefficient is combined has been proposed. . That is, as shown in FIG. 4, Al brackets 11a and 11b having relatively large thermal expansion coefficients are respectively attached to both ends of an Invar (trademark) rod 10 having a small thermal expansion coefficient, and clasps 12a are attached to these brackets 11a and 11b. 12b, the optical fiber 13 is fixed in a state of being pulled with a predetermined tension. At this time, the grating portion 13a of the optical fiber 13 is positioned between the two clasps 12a and 12b.

  When the ambient temperature rises in this state, the Al brackets 11a and 11b are extended and the distance between the two clasps 12a and 12b is shortened, so that the tension applied to the grating portion 13a of the optical fiber 13 is reduced. On the other hand, when the ambient temperature decreases, the Al brackets 11a and 11b contract and the distance between the two clasps 12a and 12b increases, so that the tension applied to the grating portion 13a of the optical fiber 13 increases. In this manner, the lattice spacing of the grating portion can be adjusted by changing the tension applied to the FBG due to the temperature change, thereby canceling the temperature dependence of the reflection center wavelength.

  However, such a temperature compensation device has a problem that it is mechanically complicated and difficult to handle.

Therefore, as a method for solving the above-mentioned problem, WO97 / 28480 has a negative thermal expansion coefficient obtained by heat-treating and crystallizing an original glass body previously formed into a plate shape as shown in FIG. A method is shown in which an FBG 16 is fixed with an adhesive 17 in a state where tension is applied by a weight 15 on a glass ceramic substrate 14, and this tension is controlled by expansion and contraction of the glass ceramic substrate 14. In order to offset the temperature dependence of the reflection center wavelength, as described above, it is necessary to apply stress in the direction in which the FBG contracts when the temperature rises and in the direction where the FBG shrinks when the temperature falls, but the substrate material has a negative thermal expansion coefficient. Therefore, it is possible to generate such stress by a single member, and WO97 / 28480 is an invention based on this effect. In FIG. 5, reference numeral 16a denotes a grating portion.
International Publication No. 97/28480 Pamphlet

  The method disclosed in WO97 / 28480 is advantageous in that it is mechanically simple and easy to handle because temperature compensation can be performed with a single member, but there is a problem that the thermal expansion hysteresis of the glass ceramic member used is large. There is. The hysteresis of thermal expansion refers to a phenomenon in which the expansion behavior of the temperature rising process does not match that of the temperature lowering process when the material expands and contracts due to a temperature change. Further, WO97 / 28480 discloses a method for stabilizing the internal structure by performing a heat cycle treatment at a temperature of 400 to 800 ° C. for the purpose of reducing the hysteresis of the glass ceramic member. The reduced hysteresis is unstable with respect to environmental changes in temperature and humidity, and it is difficult to maintain the initial value. In addition, such a heat treatment complicates the manufacturing process, which increases the cost.

  The present invention has been made in view of such circumstances, and a method for manufacturing a temperature compensation member that has low thermal expansion hysteresis, high environmental stability, and can be manufactured at low cost, and an optical communication device It aims at providing the manufacturing method of.

  As a result of various experiments to achieve the above object, the present inventors have been able to reduce the hysteresis of thermal expansion by regulating the crystal structure of the polycrystalline body constituting the temperature compensation member, and also to stabilize the environment. The present inventors have found that a temperature compensating member having excellent properties can be obtained and proposed the present invention.

  That is, the method for producing a temperature compensating member of the present invention comprises a polycrystal having a β-quartz solid solution or β-eucryptite solid solution as a main crystal, and has an interplanar spacing that gives a main peak in X-ray diffraction measurement. A method for producing a temperature compensating member smaller than 3.52 mm, wherein the polycrystal is produced by sintering powder.

  Further, the method for producing an optical communication device of the present invention comprises a polycrystal having a β-quartz solid solution or β-eucryptite solid solution as a main crystal, and the interplanar spacing of the crystal plane that gives the main peak in X-ray diffraction measurement is A method for manufacturing an optical communication device using a temperature compensating member smaller than 3.52 mm, wherein the polycrystalline body is manufactured by sintering powder.

  The interplanar spacing refers to the spacing of various crystal planes in the crystal constituting the polycrystal, and in the present invention, the crystal plane that gives the main peak in X-ray diffraction is targeted.

  The temperature compensation member of the present invention has low thermal expansion hysteresis, high stability against environmental changes, and can be manufactured at low cost. Therefore, the temperature compensation member can be used for light such as FBG, couplers, and waveguides. It is suitable as a temperature compensation member for communication devices.

  In addition, the optical communication device of the present invention uses a temperature compensation member that has low thermal expansion hysteresis and high stability against environmental changes, and therefore has stable temperature compensation characteristics.

  In general, the thermal expansion hysteresis of the temperature compensation member is affected by the use environment, and the value thereof varies depending on, for example, a high temperature and high humidity environment or a heat cycle. Further, as described above, when the hysteresis is reduced by the thermal cycle process as described in WO97 / 28480, the hysteresis is likely to change again depending on the subsequent use environment.

  However, since the temperature compensation member of the present invention is made of a polycrystal having a crystal plane spacing smaller than 3.52 mm that gives a main peak in X-ray diffraction measurement, the initial hysteresis is small and the usage environment is small. Hysteresis changes are unlikely to occur.

  FIG. 1 shows the correlation between the interplanar spacing of the polycrystal and the hysteresis. From this figure, it can be understood that the hysteresis decreases as the surface interval decreases. If the surface separation is 3.52 mm or more, the effect of reducing hysteresis as a temperature compensation member is insufficient, and at the same time, the rate of change in hysteresis due to environmental factors such as temperature and humidity increases, resulting in a device with stable characteristics. It is difficult to obtain.

  In addition, as described above, the smaller the interplanar spacing of the polycrystal, the smaller the hysteresis. However, if the interplanar spacing is reduced too much, dissimilar crystals precipitate and the thermal expansion coefficient shifts in the positive direction. Since the linearity of thermal expansion deteriorates, the surface spacing should be appropriately selected depending on the use and characteristics of the device. In the present invention, a preferable value of the interplanar spacing is 3.491 to 3.519 mm, and a more preferable value is 3.495 to 3.512 mm.

  The reason why it is not preferable that the linearity of thermal expansion deteriorates in the temperature compensating member of the present invention is as follows.

  Even if a material having a negative coefficient of thermal expansion is used as this type of substrate, as shown in 1997, AIST, C-3-46, depending on the temperature range, the temperature dependence of the reflection center wavelength may be reduced. It appears strongly and a sufficient temperature compensation function may not be obtained. This is due to the poor linearity of the thermal expansion of the substrate material. Therefore, in the present invention, the linearity of the thermal expansion is excellent, and specifically, the virtual straight line and the actual measurement at a temperature at which the deviation of the actual measurement curve with respect to the straight line (virtual straight line) connecting both ends of the thermal expansion curve of the sample is maximum. It is desirable to regulate the difference between the sample lengths of the curves so that the value divided by the sample length before the test is 60 ppm or less, which makes it possible to obtain a sufficient temperature compensation function in any temperature range. Become.

  There are various methods for changing the interplanar spacing of a polycrystal, for example, a method of adjusting the composition of the polycrystal or preparing a polycrystal, followed by ion exchange treatment. In the present invention, any method may be adopted.

The composition range suitable for reducing the interplanar spacing of the polycrystal is wt%, SiO ₂ 45-60%, Al ₂ O ₃ 20-45%, Li ₂ O 7-12%, TiO _2. It is 0 to 4% and ZrO _{2 is} 0 to 4%. Within this composition range, by regulating the content of each component to a desired value, the interplanar spacing can be made less than 3.52 mm. it can. In addition to the above components, other components such as MgO and P ₂ O ₅ can be added up to 10% by weight.

  In the present invention, after a raw material is melted, in the case of producing a polycrystalline body by reheating and crystallizing the cooled and solidified glass, in order to keep the meltability and formability of the glass good, It may be difficult to adjust the interval. On the other hand, when producing a polycrystalline body by sintering powder, it can be adjusted by the type and ratio of various raw materials before sintering without being restricted by the meltability and formability of glass. preferable. In addition, it is preferable to produce a polycrystalline body from a powder sintered body because even a complicated shape can be easily formed at low cost by a method such as press molding, cast molding, or extrusion molding. Such a powder sintered body is produced by sintering various raw material powders. The raw material powder includes amorphous glass powder, crystal-precipitating glass powder, partially crystallized glass powder, and glass powder prepared by a sol-gel method. Besides this, sol or gel may be added. .

The temperature compensation member of the present invention has a thermal expansion coefficient in the temperature range of −40 to 100 ° C. of −25 to −120 × 10 ⁻⁷ / ° C. (more preferably −50 to −90 × 10 ⁻⁷ / ° C.). ) Is preferable.

  Furthermore, in the present invention, when a polycrystalline body is produced by sintering powder, grooves and through-holes can be easily formed at predetermined locations of the sintered body simultaneously with molding. This is a great advantage in manufacturing.

  For example, an FBG optical fiber is bonded and fixed to a temperature compensation member using an adhesive (for example, glass frit or epoxy resin), and a groove or a through hole is formed at a predetermined position of the temperature compensation member. In the bonding process, the assembly can be automated easily, so that the manufacturing cost is reduced. In addition, a groove | channel and a through-hole are not limited to one place, You may form in multiple places.

  In general, when fixing a fiber-shaped device such as FBG to a temperature compensation member, tension should be applied to the device in advance so that the device does not bend when the temperature compensation member contracts from its fixed length. However, by making the diameter of the groove or the through hole close to the diameter of the device, the amount of the adhesive to be used can be reduced, and fixing with a thin adhesive layer becomes possible. If the adhesive layer becomes thinner, the stress due to the difference in thermal expansion between the adhesive, the device, and the temperature compensation member is reduced. Even when the compensation member shrinks from its fixed length, the device does not bend and there is no need to apply tension in advance, and an optical device with a temperature compensation function can be manufactured in a simpler process. In particular, when a precise through hole is formed in the temperature compensation member and a device is inserted into it, the temperature compensation member also has a function as a positioning component of the device. When a device is connected to an optical fiber or another device, it itself functions as a connection component.

  Hereinafter, the temperature compensating member of the present invention will be described in detail based on examples.

  Tables 1 and 2 show examples (sample Nos. 1 to 6) and comparative examples (sample No. 7) of the present invention.

  Each sample of Tables 1 and 2 was produced as follows.

  First, in Example No. 1-5 and No. 1 as a comparative example. Each sample of No. 7 was prepared by preparing the raw material so that the composition of the polycrystalline body after sintering was the composition (% by weight) in the table, and then putting it in a mold and press-molding it at a pressure of 20 MPa. A prismatic shaped compact (green compact) having a width of 4 mm, a thickness of 3 mm, and a length of 40 mm was produced. Subsequently, these compacts were sintered in air at 1350 ° C. for 15 hours, and then cooled to room temperature, whereby β-quartz solid solution polycrystals were obtained.

  No. Sample 6 is prepared by preparing the raw material so that the composition of the polycrystal after crystallization is the composition (% by weight) in the table, melting at 1500 ° C. for 7 hours, and rapidly cooling to produce glass, Subsequently, it is made into the polycrystal which precipitated (beta) -eucryptite solid solution by making it crystallize by heating at 1350 degreeC for 15 hours.

  In addition, the raw material of these polycrystals can be suitably selected from various minerals and compounds. In addition, β-Qs. s. Indicates β-quartz solid solution, β-Es. s. Indicates β-eucryptite solid solution.

As is apparent from the table, Examples No. Each of the samples 1 to 6 is made of β-quartz solid solution or β-eucryptite solid solution, has a negative coefficient of thermal expansion of −26 to −95 × 10 ⁻⁷ / ° C., and a surface spacing of 3. Since it is smaller than 52 mm, the initial hysteresis is small, and the change in hysteresis after high temperature and high humidity is also small, so it was suitable as a temperature compensation member. In each sample, the linearity of thermal expansion was 60 ppm or less.

  FIG. 2 is a graph showing the thermal expansion curve of the sample No. 2, and FIG. It is a graph which shows the temperature dependence of the reflection center wavelength of FBG using the member for temperature compensation which consists of 2 samples. From FIG. 2 shows good linearity of thermal expansion. From FIG. 3, the temperature dependence of the reflection center wavelength of the FBG with temperature compensation is much smaller than that without temperature compensation, and in any temperature range. But it can be understood that it is constant.

  On the other hand, No. which is a comparative example. The sample No. 7 has a large surface separation of 3.534 mm, so the initial hysteresis and the change in hysteresis after the high-temperature and high-humidity test are large, and the linearity of thermal expansion is larger than 60 ppm, which is not suitable as a temperature compensation member. Met.

  In addition, the kind of crystal | crystallization in a table | surface and the space | interval of the crystal plane which gives a main peak were calculated | required by X-ray diffraction, and the thermal expansion coefficient and the hysteresis were measured with the dilatometer. The coefficient of thermal expansion is measured in the temperature range of −40 to 100 ° C., and the hysteresis is when heated at 30 ° C. when the sample is repeatedly heated and cooled at a rate of 1 ° C./min in the temperature range of −40 to 100 ° C. And the difference in sample length during cooling was measured and divided by the sample length before the test. The hysteresis after the high-temperature and high-humidity test is a value after being left for 500 hours in an environment of 70 ° C. and 85% RH.

It is a graph which shows the correlation of the space | interval of the crystal plane of a polycrystal, and hysteresis. No. as an example. It is a graph which shows the thermal expansion curve of 2 samples. No. as an example. It is a graph which shows the temperature dependence of the reflection center wavelength of FBG using the member for temperature compensation which consists of 2 samples. It is a front view which shows the apparatus which prevents the fluctuation | variation with respect to the temperature change of the reflection wavelength of the conventional FBG. It is a perspective view which shows the glass-ceramic board | substrate which has the negative thermal expansion coefficient which fixed FBG to the surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Invar rod 11a, 11b Al bracket 12a, 12b Clasp 13 Optical fiber 13a, 16a Grating part 14 Glass ceramic substrate with negative thermal expansion coefficient 15 Weight 16 FBG
17 Adhesive

Claims (4)

  A method for producing a temperature compensation member comprising a polycrystal having a β-quartz solid solution or a β-eucryptite solid solution as a main crystal, and a crystal plane spacing which gives a main peak in X-ray diffraction measurement is smaller than 3.52 mm The method for producing a temperature compensating member, wherein the polycrystalline body is produced by sintering powder. 2. The method for producing a temperature compensating member according to claim 1, wherein the temperature compensating member has a thermal expansion coefficient of −25 to −120 × 10 ⁻⁷ / ° C. in a temperature range of −40 to 100 ° C. 3. .   Using a temperature compensation member comprising a polycrystal having a β-quartz solid solution or β-eucryptite solid solution as a main crystal, and having a crystal plane spacing which gives a main peak in X-ray diffraction measurement is smaller than 3.52 mm. An optical communication device manufacturing method, wherein the polycrystal is produced by sintering powder. The method for manufacturing an optical communication device according to claim 3, wherein the temperature compensation member has a thermal expansion coefficient in the temperature range of −40 to 100 ° C. of −25 to −120 × 10 ⁻⁷ / ° C. 5.