JP2004295156A - Temperature compensation device for optical communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature compensation device for optical communication which can be miniaturized, has a simple machinery and has a satisfactory temperature compensation effect. <P>SOLUTION: In the temperature compensation device for optical communication, an inner hole is formed on a prescribed part of a substrate having a negative thermal expansion coefficient of -10 to -120×10<SP>-7</SP>/°C in the temperature range of -40 to 100°C, the substrate having the negative thermal expansion coefficient precipitates a β-eucryptite crystal or β-quartz solid solution crystal, a large number of micro cracks are formed in the crystals and optical components having a positive thermal expansion coefficient penetrates the inner hole so as to be fixed at two points or more or on the whole surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a temperature compensation device for optical communication using a substrate having a negative coefficient of thermal expansion.

  With the advance of optical communication technology, networks using optical fibers are being rapidly developed. In networks, wavelength multiplexing technology for transmitting light of a plurality of wavelengths collectively has been 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 and hinder outdoor use.Therefore, a technology that keeps the characteristics of such devices constant regardless of the temperature change, the so-called temperature There is a need for compensation technology.

  A typical optical communication device requiring temperature compensation is a fiber Bragg grating (hereinafter, referred to as FBG). The FBG is a device in which a so-called grating is formed in a portion having a refractive index change in a lattice shape in the core of an optical fiber, and reflects light of a specific wavelength according to the relationship shown in the following equation (1). Has features. For this reason, it has been drawing 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 via one optical fiber.

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

  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 expressed by the following equation (2) obtained by differentiating the equation (1) with the temperature (T).

(∂Λ / ∂T) / Λ in the second term on the right side of the equation (2) corresponds to the coefficient of thermal expansion of the optical fiber, and its value is about 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 of the optical fiber, and its value is about 7.5 × 10 ⁻⁶ / ° C. In other words, it can be seen that the temperature dependence of the reflection wavelength depends on both the change in the refractive index of the core portion and the change in the lattice spacing due to thermal expansion, but most of the time is due to the temperature change in the refractive index.

  As a means for preventing such a change in the reflection wavelength, a method is known in which a tension corresponding to a temperature change is applied to the FBG to change a lattice interval, thereby canceling a component caused by a change in the refractive index. .

  As a specific example of this method, there has been proposed a method of fixing the FBG to a temperature compensating member in which a material such as an alloy or a quartz glass having a small thermal expansion coefficient and a metal such as an aluminum having a large thermal expansion coefficient are combined. . That is, as shown in FIG. 5, Al brackets 11a and 11b having a relatively large thermal expansion coefficient are attached to both ends of an Invar (trademark) rod 10 having a small thermal expansion coefficient, and a clasp 12a is attached to these brackets 11a and 11b. , 12b to fix the optical fiber 13 in a state of being pulled by a predetermined tension. At this time, the grating portion 13a of the optical fiber 13 is located between the two clasps 12a and 12b.

  When the ambient temperature rises in this state, the Al brackets 11a and 11b expand, and the distance between the two clasps 12a and 12b decreases, so that the tension applied to the grating portion 13a of the optical fiber 13 decreases. 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. As described above, the lattice spacing of the grating portion can be adjusted by changing the tension applied to the FBG in accordance with the temperature change, thereby canceling the temperature dependence of the reflection center wavelength.

  However, there is a problem that such a temperature compensating device is mechanically complicated and difficult to handle.

As a method for solving the above-mentioned problem, WO97 / 26572 discloses a glass ceramic substrate having a negative coefficient of thermal expansion which is crystallized by heat-treating a raw glass body previously formed into a plate shape as shown in FIG. FIG. 14 shows a method of controlling the tension of the FBG 15 by fixing the FBG 15. In FIG. 3, reference numeral 16 denotes a grating portion, 17 denotes an adhesive fixing portion, and 18 denotes a weight.
WO 97/26572 pamphlet JP-A-10-96827 JP-A-8-286040

  The method disclosed in WO97 / 26572 has the advantage of being mechanically simple and easy to handle because temperature compensation can be performed with a single member, but the FBG 15 is bonded to one surface of the glass ceramic substrate 15. Therefore, it is required to increase the thickness so that the substrate does not warp when the substrate expands due to a temperature change.

  In order to connect such a substrate 14 to another device, a separate connector is required. As a result, the number of connection parts increases, light loss increases, device cost increases, and the device increases. There's a problem.

  In addition to the above, JP-A-10-96827 discloses a temperature compensating member having a negative coefficient of thermal expansion composed of a Zr-tungstate-based or Hf-tungstate-based, These raw materials are very expensive, and practical use as industrial products is difficult.

Further, Japanese Patent Application Laid-Open No. Hei 8-286040 discloses a temperature compensating member (fixing member) having a smaller coefficient of thermal expansion than glass fiber, and the temperature compensating member has a coefficient of thermal expansion of 5.5 of quartz glass. It is made of a material having a positive coefficient of thermal expansion of less than × 10 ^-7 / ° C, and a material having a zero or negative coefficient of thermal expansion, but no temperature compensating member having a sufficiently negative coefficient of thermal expansion is suggested.

  In other words, Japanese Patent Application Laid-Open No. 8-286040 describes that if a temperature compensating member having a smaller coefficient of thermal expansion than a glass fiber is used, a sufficient temperature compensating function can be obtained. Understanding is a complete mistake. That is, as is apparent from the above equation 1, even if a material having a positive coefficient of thermal expansion is used as the temperature compensating member, a sufficient effect of temperature compensation cannot be obtained, and a specific material having a thermal expansion coefficient cannot be obtained. A neoceram N-0 manufactured by Nippon Electric Glass Co., Ltd., whose coefficient is almost zero, is shown. However, even with this neoceram N-0, the negative thermal expansion coefficient is too small, and the effect of sufficient temperature compensation is obtained. Cannot be obtained.

  An object of the present invention is to provide a compensating device for optical communication which can be reduced in size, is mechanically simple, and has a sufficient temperature compensating action. Another object is to form the compensating device easily and at low cost. Another object of the present invention is to provide a temperature compensation device for optical communication that can simplify the method of connecting to an optical fiber.

That is, the temperature compensation device for optical communication of the present invention has an inner hole at a predetermined position of a base material having a negative coefficient of thermal expansion of -10 to -120 × 10 ⁻⁷ / ° C. in a temperature range of −40 to 100 ° C. Formed, the substrate having a negative coefficient of thermal expansion, β-eucryptite crystals, or β-quartz solid solution crystals are precipitated, a number of microcracks are formed in the crystals, the inner hole, An optical component having a positive coefficient of thermal expansion is penetrated so as to be fixed at two or more points or on the entire surface.

  As described above, the temperature compensation device for optical communication of the present invention can be miniaturized, mechanically simple, and has a sufficient temperature compensation effect, so that the temperature of the fiber Bragg grating, coupler, waveguide, etc. It is suitable as a compensation device.

The temperature compensation device for optical communication of the present invention has a structure in which a positive heat is applied to an inner hole of a substrate having a negative coefficient of thermal expansion of -10 to -120 × 10 ^-7 / ° C in a temperature range of -40 to 100 ° C. Since the through-hole is formed so that the component having the expansion coefficient is fixed, sufficient temperature compensation action can be obtained, and even if the optical component having the positive thermal expansion coefficient is under tension, the inner hole is formed. , And stress is not applied from one direction unlike the conventional plate-like substrate, so that deformation such as warpage hardly occurs. Therefore, it is not necessary to increase the thickness of the substrate. Furthermore, since the stress on the fiber can be applied uniformly not only from the lower surface direction as in the conventional plate-shaped substrate but also from the entire periphery of the base material, the durability of the fiber can be improved and the fiber can be protected. Therefore, since a protective cover is not required, the size can be reduced.

However, when the coefficient of thermal expansion of the base material approaches a positive direction from −10 × 10 ⁻⁷ / ° C., the temperature compensation becomes insufficient, and when the coefficient of thermal expansion increases in a negative direction beyond −120 × 10 ⁻⁷ / ° C., It is not preferable because the temperature dependence of the direction is observed.

  The above-mentioned inner hole is not limited to one place of the base material, and may be formed at a plurality of places, and in order to fix a component having a positive coefficient of thermal expansion to a base material having a negative coefficient of thermal expansion, Uses adhesives such as polymer (for example, epoxy resin), metal (for example, metal solder such as Au-Sn), frit (for example, low melting glass frit or composite frit thereof and negative expansion filler), thermosetting resin, and ultraviolet curing resin. Just do it. In particular, it is preferable to form one or a plurality of small holes communicating with the inner hole in the side peripheral portion of the base material because the adhesive can be easily injected into the inner hole.

  When an optical component having a positive coefficient of thermal expansion is fixed to a substrate having a negative coefficient of thermal expansion, it may be fixed at two or more points or on the entire surface. In the case of fixing at two or more points, even when the substrate having a negative coefficient of thermal expansion shrinks, a part having a positive coefficient of thermal expansion is fixed after applying tension so as not to bend. In the case where it is fixed on the entire surface, there is an advantage that it is not necessary to apply a tension since a component having a positive coefficient of thermal expansion is unlikely to bend.

  The base material used in the present invention may be formed into a predetermined shape by machining directly after a method of directly molding from molten glass such as downdraw, or after preforming the molten glass. When a base material is manufactured by accumulating crystal powder showing anisotropy and sintering, even a complicated shape can be easily formed at low cost by methods such as press molding, cast molding, extrusion molding, etc. This is preferable because a base material having a through hole can be formed. When accumulating crystal powder, it is preferable to use an organic binder because a sintered body having a desired shape can be easily obtained.

Since the substrate having a negative coefficient of thermal expansion of the present invention contains crystals exhibiting anisotropy in the coefficient of thermal expansion therein, in the temperature range of -40 to 100 ° C as a whole, -10 to -120 × A coefficient of thermal expansion of 10 ⁻⁷ / ° C. (preferably −30 to −90 × 10 ⁻⁷ / ° C.) is obtained. In particular, when each crystal powder particle having an anisotropic coefficient of thermal expansion is used, a large number of microcracks are generated at the crystal grain boundaries during cooling of the crystal particles grown in the sintering process, and a desired coefficient of thermal expansion is obtained. Cheap.

  Each crystal powder particle having an anisotropic thermal expansion coefficient expands or contracts in various directions according to the thermal expansion coefficient in the respective crystal axis direction during the heat treatment, and the respective powder particles are rearranged with each other to increase the packing density. Thus, the contact area between the particles increases. This promotes the tendency of the powder particles to fuse together during heat treatment and try to minimize surface energy, resulting in a ceramic member having high strength, specifically a flexural strength of 10 MPa or more. Will be able to In the present invention, in order to increase the contact area between the powder particles, it is desirable that the crystal powder has a particle size of 50 μm or less.

A crystalline powder having anisotropic thermal expansion coefficient refers to a crystal having a negative thermal expansion coefficient in at least one crystal axis direction and a positive thermal expansion coefficient in the other axis direction. Silicates represented by β-eucryptite crystals and β-quartz solid solution crystals, titanates such as PbTiO ₃ , phosphates such as NbZr (PO ₄ ) ₃ , and La, Nb, V, Ta, etc. Among them, the β-eucryptite crystal powder has a large thermal expansion coefficient anisotropy, and therefore has a thermal expansion of −10 to −120 × 10 ⁻⁷ / ° C. The β-eucryptite crystal powder produced by a so-called solid-phase method of easily obtaining a coefficient and further mixing and firing the raw material powder is a β-eucryptite crystal powder produced by a melting method in which the raw material is once melted. Can be synthesized at a lower temperature and crushed There is an advantage that it can be manufactured at low cost because it is easy.

  Further, in the present invention, it is possible to mix other types of crystal powder with the above crystal powder, and by using two or more types of crystal powder in combination, the thermal expansion coefficient, the strength, or the chemical property is increased. Adjustment is easier.

  Further, in the present invention, one kind of an additive such as an amorphous glass powder, a crystallizable glass powder, a partially crystallized glass powder, a glass powder prepared by a sol-gel method, a sol, and a gel is used for the crystal powder. Alternatively, by adding two or more kinds at a ratio of 0.1 to 50% by volume and then sintering, it is possible to further improve the bending strength. By the way, the crystallizable glass powder is a glass powder having a property of precipitating crystals inside by heat treatment, and a partially crystallized glass powder is a crystallized glass powder having crystals precipitated in glass. That is.

  Further, in the present invention, when the substrate having a negative coefficient of thermal expansion is formed into a cylindrical shape or a prismatic shape, it can be directly inserted into a connector outer tube provided with a cylindrical or prismatic sleeve, and is used for other optical communication. It functions as a positioning component between the device and the optical component that penetrates the inner hole, and enables highly accurate connection. In particular, it is preferable that the end of the base material has a tapered shape that becomes thinner in the direction of the tip end, because it becomes easier to insert the base material into the connector outer tube. Further, it is preferable that the end of the inner hole of the base material has a tapered shape that becomes thinner in the inner direction, because the optical fiber can be easily inserted.

  Further, when the base material used in the present invention is formed by forming a plurality of parts in advance and joining these parts, even a base material having a complicated shape can be easily manufactured.

  A base material having a through hole manufactured by joining such a plurality of parts is manufactured, for example, by joining two parts 19a and 19b having a semicircular cross section as shown in FIG. A cylindrical base member 19, a prismatic base member 20 formed by joining two parts 20a and 20b having a concave cross section as shown in FIG. 3, a part 21a having a concave cross section as shown in FIG. The prismatic base material 21 produced by joining the shape-like parts 21b is mentioned.

Also in the case of manufacturing a substrate having a negative coefficient of thermal expansion for use in the present invention from the glass by the melting method is, in weight _{percent, SiO 2 43~63%, Al 2} O 3 33~43%, Li 2 O Glass having a composition of 7-11%, ZrO ₂ 0-6%, TiO ₂ 0-6%, SnO ₂ 0-6%, P ₂ O ₅ 0-6%, or SiO ₂ 50-75%, Al _{2 O 3 15~30%, Li 2 O} 3~7%, ZrO 2 0~5%, TiO 2 0~6%, SnO 2 0~7%, the glass having a composition of P ₂ O ₅ 0~6% A method of precipitating a large number of β-eucryptite crystals or β-quartz solid crystals by heat treatment is employed.

  Hereinafter, the temperature compensation device for optical communication of the present invention will be described in detail based on examples.

(Example 1)
The powder of β-eucryptite crystals produced by the solid-phase method was mixed with an organic binder (ethyl cellulose), and the mixture was charged into a mold, followed by press molding to produce a green compact having a cylindrical shape.

  The green compact was heated at 1300 ° C. for 10 hours, and then cooled at a temperature lowering rate of 200 ° C./hour to produce a cylindrical sintered body 22 as shown in FIG.

Many microcracks were formed in the crystal of the cylindrical sintered body 22, and the coefficient of thermal expansion in a temperature range of -40 to 100 ° C was -80 × 10 ^-7 / ° C.

  In the inner hole 22a of the cylindrical sintered body 22, a positive expansion optical component having a refractive index grating made of an optical fiber containing silica as a main component is inserted, and the epoxy is applied while tension is applied to the optical fiber. Both ends of the inner hole were bonded and fixed using a resin.

  In order to examine the temperature compensation performance of the thus-obtained temperature compensation device for optical communication, a test (operating temperature range from −40 ° C. to 100 ° C.) was performed, and compared with a case where a device without temperature compensation was used.

  As a result, the device without temperature compensation exhibited a temperature dependence of 0.012 nm / ° C. with respect to the reflection center wavelength of 1550 nm, whereas the device of the example exhibited a temperature dependency of 0.001 nm / ° C. The temperature dependence was significantly improved.

(Example 2)
First, a glass raw material was prepared to have a composition of 46.5% of SiO ₂ , 41.0% of Al ₂ O ₃ , 9% of Li ₂ O, and 3.5% of ZrO _{2 by} weight percentage, and then, in a platinum crucible. The glass body was melted, formed into a plate shape, and then cut into a cylindrical shape to form a glass body having a diameter of 3 mm, an inner diameter of 0.5 mm, and a length of 40 mm.

  Next, the glass body was heated at a heating rate of 200 ° C./hour, kept at 760 ° C. for 3 hours, 1350 ° C. for 10 hours, and then cooled at a cooling rate of 200 ° C./hour to produce a crystallized glass body. .

The main crystal of the crystallized glass body thus obtained is a β-eucryptite crystal, in which a large number of microcracks are formed, and the coefficient of thermal expansion in a temperature range of −40 to 100 ° C. is −70 × It was 10 ^-7 / ° C.

  Using this cylindrical crystallized glass body, a temperature compensating device for optical communication similar to that of Example 1 was fabricated, and its temperature compensating performance was examined. Showed dependence.

(Example 3)
By cutting the crystallized glass body produced in the same manner as in Example 2, two parts, a crystallized glass body having a concave cross section and a plate-shaped crystallized glass body as shown in FIG. 3, were produced. Next, these parts were joined together using an epoxy resin to produce a prismatic sintered body having an inner hole.

  Using this prismatic sintered body, a temperature compensating device for optical communication similar to that of Example 2 was fabricated, and its temperature compensating performance was examined. Showed sex.

(Example 4)
After melting the glass of Example 2, the glass was formed into a film and then pulverized by a ball mill. Next, after putting this in a metal mold, press molding was performed to produce a plate-like green compact.

  This plate-like green compact was heated and cooled under the same conditions as in Example 2 to produce a crystallized glass body, and then, by cutting, the crystallized glass body (parts) having a concave cross section as shown in FIG. ) Were prepared. Then, the end portions of these parts were joined to each other using an epoxy resin to produce a prismatic sintered body having an inner hole.

  In the inner hole of this prismatic sintered body, a positive expansion optical component having a refractive index grating with an optical fiber mainly composed of silica is inserted, and epoxy resin is applied in a state where tension is applied to the optical fiber. The inner hole was filled and adhered and fixed.

  In order to examine the temperature compensation performance of the thus-obtained temperature compensation device for optical communication, a test similar to that of Example 1 was performed. As a result, a temperature dependence of 0.001 nm / ° C. was exhibited with respect to a central reflection wavelength of 1550 nm.

It is a perspective view showing one mode of a substrate which has an inner hole of the present invention. It is a perspective view showing other modes of a substrate which has an inner hole of the present invention. It is a perspective view showing other modes of a substrate which has an inner hole of the present invention. It is a perspective view showing other modes of a substrate which has an inner hole of the present invention. It is a front view which shows the conventional apparatus which prevents the fluctuation with respect to the temperature change of the reflection wavelength of FBG. It is a perspective view which shows the glass-ceramic substrate which has a negative thermal expansion coefficient which fixed FBG to the surface.

Explanation of reference numerals

REFERENCE SIGNS LIST 10 Invar rod 11 a, 11 b Al bracket 12 a, 12 b Clasp 13, 15 Optical fiber 13 a, 16 Grating portion 14 Glass ceramic substrate having a negative coefficient of thermal expansion 17 Adhesive fixing portion 18 Weight 19 Cylindrical base material 20, 21 prismatic Base material 22 Cylindrical sintered body

Claims (9)

In a temperature range of −40 to 100 ° C., an inner hole is formed at a predetermined position of a substrate having a negative coefficient of thermal expansion of −10 to −120 × 10 ⁻⁷ / ° C., and a substrate having the negative coefficient of thermal expansion is formed. The material precipitates a β-eucryptite crystal or a β-quartz solid solution crystal, a number of microcracks are formed in the crystal, and an optical component having a positive coefficient of thermal expansion is formed in the inner hole. A temperature compensating device for optical communication, wherein the temperature compensating device is penetrated so as to be fixed at points or over the entire surface. 2. The light according to claim 1, wherein the substrate having a negative coefficient of thermal expansion has a cylindrical shape or a prismatic shape, and functions as a positioning component for an optical component that penetrates the inner hole when an optical signal is connected. Temperature compensation device for communication. 2. The temperature compensating device for optical communication according to claim 1, wherein one or both ends of the substrate having a negative coefficient of thermal expansion have a tapered shape tapered in a tip direction. 2. The temperature compensation device for optical communication according to claim 1, wherein one or a plurality of small holes communicating with the inner holes are formed in a side peripheral portion of the substrate having a negative coefficient of thermal expansion. 2. The temperature compensation device for optical communication according to claim 1, wherein one or both ends of the inner hole formed in the substrate having a negative coefficient of thermal expansion have a tapered shape tapered inward. 2. The optical communication according to claim 1, wherein the base material having a negative coefficient of thermal expansion is made of a sintered body of a powder containing β-eucryptite as a main component produced by a solid-phase method. For temperature compensation device. 2. The temperature compensation device for optical communication according to claim 1, wherein the substrate having a negative coefficient of thermal expansion is produced by dividing the substrate into a plurality of parts and joining the parts. A substrate having a negative thermal expansion coefficient, in weight _{percent, SiO 2 43~63%, Al 2} O 3 33~43%, Li 2 O 7~11%, ZrO 2 0~6%, TiO 2 0~ _{6%, SnO 2 0~6%,} P 2 O 5 optical communications for temperature compensation device according to claim 1, characterized by being made from glass having 0-6% of the composition. A substrate having a negative thermal expansion coefficient, in weight _{percent, SiO 2 50~75%, Al 2} O 3 15~30%, Li 2 O 3~7%, ZrO 2 0~5%, TiO 2 0~ _{6%, SnO 2 0~7%,} P 2 O 5 optical communications for temperature compensation device according to claim 1, characterized by being made from glass having 0-6% of the composition.