JP2008241824A - Optical circuit module - Google Patents

Abstract

A compact optical circuit module having a plurality of functions or multistage functions is provided.
A substrate 3 having intersecting grooves 8 on the main surface, and an optical fiber 1 installed in the grooves 8 and intersecting each other so as to overlap each other at the intersecting portions of the grooves 8 are provided. At least one of the optical fibers 1 that overlapped each other was bent and fixed.
[Selection] Figure 1

Description

  The present invention relates to an optical circuit module used in an optical communication device and an optical sensing system device of an optical transmission system using single or plural wavelength light.

  Various optical circuit modules are used for downsizing and integration of optical circuits in optical communication equipment. One example is the multi-core type optical branching / coupling device shown in FIG. It has two sets of optical collimator systems in which a refractive index distribution type (graded index type, GI for short) GI lens 110 is connected to one end of a single mode fiber (hereinafter referred to as SM fiber) 105. An optical member 111 having a right angle, three sets of hexagonal prisms having opposite sides parallel to each other, and two right triangle prisms whose outer diameter becomes a square when combined with the hexagonal prism, and a dielectric on the hypotenuse of the right triangle prism A half mirror film made of a multilayer film 112 or the like is formed, and the four sets of GI lenses 110 of the two sets of optical collimator systems mounted with their optical axes aligned.

  In this case, the light emitted from the GI lens 110 of one optical collimator system of the port AA is transmitted and reflected by the half mirror film 112 at a predetermined branching ratio, and the transmitted light is transmitted to the other GI lens of the opposed port BB. 110 enters and exits from the connected SM fiber 105. The reflected light is transmitted through the hexagonal prism, is incident on another half mirror film 112 disposed in parallel and opposite, and is transmitted, reflected, and transmitted at a predetermined branching ratio, and is absorbed by the absorber as it is. The reflected light is incident on the GI lens 110 of another optical collimator system of the port DD and is emitted from the connected SM fiber 105. Under the same conditions, the light incident from the port DD is transmitted from the SM fiber 105 of the port CC and is transmitted from the SM fiber 105 of the port AA.

In addition, the dielectric multilayer film 112 can be equipped with not only branch coupling by the half mirror function but also an optical multiplexing / demultiplexing function for reflecting and transmitting light of a special wavelength. In that case, the light incident from the port AA transmits and reflects the specific wavelength light which is the dielectric multilayer film 112, and emits light of different wavelengths from the port BB and the port DD. The light is emitted from the port CC when entering from the port DD.
JP-A-2-25807

  In recent years, there has been a demand for an optical circuit module having a plurality of functions or a multi-stage function by combining a plurality of functions of an optical circuit module having such a conventional structure. However, if a plurality of optical circuit modules having a conventional structure are mounted and integrated on a single substrate, they cannot be mounted efficiently, and light having a plurality of functions or multi-stage functions as a final product. There was a problem that the circuit module was increased in size.

  Accordingly, the present invention has been made in view of the above-described circumstances, and an object thereof is to provide a small optical circuit module.

  An optical circuit module of the present invention includes a substrate having intersecting grooves on a main surface, and an optical fiber installed in the groove and intersecting each other so as to overlap each other at the intersection of the grooves. It is characterized in that at least one of the optical fibers overlapping each other is bent.

  The optical circuit module of the present invention is preferably characterized in that a recess deeper than the groove is formed at the intersection of the grooves.

  The optical circuit module of the present invention is preferably characterized in that an optical element is mounted on the main surface so as to face the tip of the optical fiber.

  In the optical circuit module of the present invention, preferably, the optical fiber has a bending loss smaller than that of the remaining portion in the bent portion.

  In the optical circuit module of the present invention, preferably, the optical fiber has the bent portion made of a holey fiber.

  In the optical circuit module of the present invention, it is preferable that the optical fiber has a GI lens fiber at a tip facing the optical element.

  The optical circuit module of the present invention is preferably characterized in that a coreless fiber is further connected to the tip of the GI lens fiber.

  In the optical circuit module of the present invention, preferably, the optical element has any one of a branching / coupling function, a filter function, a mirror function, a polarization function, a Faraday rotation function, an attenuation function, and an isolator function. And

  According to the present invention, the optical fiber can be highly integrated on the main surface of the substrate, and the optical circuit module can be easily downsized and integrated.

  Next, embodiments of the optical circuit module of the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment of an optical circuit module according to the present invention. Three optical elements 2i, 2g, and 2h (hereinafter, optical elements 2i, 2g, and 2h are collectively referred to as an optical element 2) on a substrate 3. And four optical fibers 1a, 1b, 1c, and 1d (hereinafter, the optical fibers 1a, 1b, 1c, and 1d are collectively referred to as an optical fiber 1) and are fixedly mounted.

  The substrate 3 to be used is the one shown in FIG. The substrate 3 has a thickness T and terraces for fixing the optical fibers on both sides. The material of the substrate 3 can be quartz glass, ceramic, silicon substrate or the like. Further, three parallel grooves (concave portions) X having a width S and a depth E are formed on the substrate 3 with a spacing P. Further, in the center line of the parallel groove X, an optical fiber fixing groove 8 (hereinafter referred to as an optical fiber fixing groove) intersecting at an angle 2Θ is formed at an interval W. The cross-sectional shape of the optical fiber fixing groove 8 may be any shape that can position the optical fiber, and examples thereof include a V groove, a U groove, and a rectangular groove.

  5A to 5D show examples of various configurations of the optical fibers 1a to 1d used in FIG. In the optical fiber 1a of FIG. 5A, a GI lens fiber 6 having a length GL set to a working distance with an optimum connection loss with respect to the length CL is fused on both sides of the coreless fiber 7 having a predetermined length CL. Two pieces that are spliced are prepared, and they are fusion spliced with a predetermined length of SM fiber 5 so that the center-to-center distance of each coreless fiber is P. These fusion splices can be easily manufactured using a high frequency discharge fusion splicer and a fiber cutter that can be cut to a precise length. The connection loss between the GI lens fibers 6 via the coreless fiber 7 is within 0.2 to 0.3 dB.

  The optical fiber 1b shown in FIG. 5B is mainly used for a reflection port. Similarly, the GI lens fiber 6 having the optimum length GL is provided on both sides of the coreless fiber 7 having the predetermined length CL. The spliced connection is similarly spliced with SM fibers 5 on both sides thereof, and the GI lens fiber 6 and the coreless fiber 7 having a length DL are sequentially spliced to the tip. The length between the coreless fibers is P.

  FIG. 5C is also used for a reflection port. In this case, a low bending loss SM fiber 13 having a length ω is fusion-spliced between SM fibers 5. The SM fiber 13 with low bending loss is an optical fiber having an allowable bending radius of 15 mm or less while maintaining a single mode characteristic, whereas the allowable bending radius of the normal SM fiber 5 is 30 mm. Note that the allowable bending radius is that the angle of light incident on the interface between the core and the cladding may be larger than the complementary angle of the critical angle in the optical fiber bent small, in which case the light will enter the cladding. Leak bending loss. The bending loss is defined by the minimum radius (the bending loss is defined by. The SM fiber 13 having such a low bending loss increases the relative refractive index difference between the core and the clad or devise the shape of the refractive index distribution. Even if the bending radius is small, loss is not easily generated, and the same characteristics that are strong against bending can be obtained by using a holey fiber having a plurality of hole structures inside. As in the case of (b), the GI lens fiber 6 and a coreless fiber having a length DL are fused and connected to the tip on one side.

  In the present invention, the optical fibers 1 intersect so as to overlap each other, and at the intersection B, at least one of the optical fibers 1 overlapping each other is bent. The optical fiber 1 more preferably has a bending loss smaller in the bent portion than in the remaining portion. With such a configuration, optical loss can be further reduced.

Here, the optical loss at the bent portion indicates the optical loss when the optical fiber is bent with a constant bending radius. And when each part of the optical fiber 1 is bent at a constant bending radius, the optical loss at the bent portion is 1/100 to 1/1000 times or less compared to the case where the remaining SM fiber 5 is bent similarly. The light loss at the bent portion is within 0.01 to 0.001 dB. For such a configuration, as shown in FIG. 5C, it is preferable to use an optical fiber having an allowable bending radius of 15 mm or less at the bent portion.

  FIG. 5D shows a case where the GI lens fiber 6 and the coreless fiber 7 having a length DL are fused and connected to one end of the SM fiber 5.

  The configuration of the optical fiber 1 used in the present invention is not limited to the above-described embodiment, and if necessary, a connection portion by the coreless fiber 7 and the GI lens fiber 6 may be installed corresponding to the location of the connection portion of the optical element 2. Good.

  The optical fibers 1a to 1d as described above are sequentially fixed and mounted in the fixing groove 8 of the substrate 3 with an adhesive or the like (see FIG. 1). The coreless fiber 7 of each optical fiber 1 is fixed so as to correspond to the parallel groove X on which the optical element 2 is mounted. That is, the two coreless fibers 7 of the optical fiber 1a are fixed so as to cross the part where the optical elements 2g and 2h of the parallel groove X are mounted. Further, the coreless fiber 7 at the tip of the optical fiber 1b faces the portion where the optical element 2g of the parallel groove X is mounted, and the coreless fiber 7 in the optical fiber 1b is a portion where the optical element 2i of the parallel groove X is mounted. Secure so that it crosses. Further, the coreless fiber 7 at the tip of the optical fiber 1c is fixed so as to face the portion of the parallel groove X where the optical element 2h is mounted. Further, the coreless fiber 7 at the tip of the optical fiber 1d is fixed so as to face the portion of the parallel groove X where the optical element 2i is mounted. In order to fix the optical fiber 1, the upper surface of the substrate 3 may be pressed by a flat cover.

Here, since the optical fiber 1c intersects the optical fiber 1d, it is finally attached to the mounting substrate 3. 3 shows the intersection B, FIG. 3 (a) is a top view thereof, and FIG. 3 (b) is a side view seen from the direction of the arrow in FIG. 3 (a). The optical fiber 1d is normally mounted in the fixing groove 8, but the optical fiber 1c intersects the optical fiber 1d with a radius of curvature r over the bent portion length ω. Here, the radius of curvature r of the optical fiber 1c at the intersection is defined as r = (4d ² + ω ² ) / 16d (hereinafter referred to as Equation 1).

  According to the present invention, the intersecting portion B of the groove 8 (in FIG. 1, the parallel groove X is formed at the intersecting portion of the groove 8, but the grooves 8 on both sides of the parallel groove X are extended in the axial direction to 8 can be regarded as intersecting each other.) By bending at least one of the optical fibers 1 and crossing the optical fibers 1 so as to overlap each other, the optical fiber 1 is highly advanced on the main surface of the substrate 3. Therefore, the optical circuit module can be easily downsized and integrated.

  In addition, although the recessed part X does not need to be formed in the crossing part B of the groove | channel 8 where the optical fiber 1 crossed, Preferably the recessed part X deeper than the groove | channel 8 is formed like FIG. Is preferred. Thus, when the recessed part X is formed in the crossing part B of the optical fiber 1, the optical fibers 1 which cross | intersect can be mutually bent, and the recessed part X is not formed in the curvature radius of the bending of the optical fiber 1. It can be made smaller than the case, and the optical loss can be further reduced.

  FIG. 6 shows the relationship between the radius of curvature r and the bent portion length ω at the intersection B when the outer diameter d of the optical fiber 1 is 125 μm. In the case of a general-purpose SM fiber, it can be seen that a bending radius r = 30 mm and a bent portion length ω = 6 mm at that time are required. Therefore, in the case of a general-purpose SM fiber, about 10 mm is required as the P length of the mounting substrate to fix the optical fiber 1.

  Furthermore, the value of the bending portion length ω of the optical fiber 1 decreases as the bending radius r decreases according to the relational expression (1). Therefore, the optical fiber 1 can reduce the bending radius r and the bending portion length ω when the bending loss is smaller in the bending portion than in the remaining portion. As a result, the P length of the mounting substrate can be further reduced, and miniaturization and integration can be further improved.

  FIG. 7 shows the relationship of bending loss when optical transmission is turned 10 turns (rotation) at the bending radius r of two types of low bending loss SM fibers. The refractive index difference Δ is larger than that of a normal SM fiber, and the mode field diameter is also smaller. The low bending loss SM fiber 1 has a rectangular single-peaked refractive index distribution as in the case of a general SM fiber, but the low bending loss SM fiber 2 has a stepped refractive index distribution, and the mode field diameter is The SM fiber 1 is slightly smaller than 9 μm, about 8.6 μm. Similar bending characteristics can be obtained with holey fibers.

  It has been shown that a practical range of bending loss of 0.5 dB / 10 turns can be realized with a bending radius r of about 4 to 15 mm with the low bending loss SM fiber used. In the case of general-purpose SM fiber, the allowable bending radius r is about 30 mm, in the case of low bending loss SM fiber 1, r = 8 mm or more, and in the case of low bending loss SM fiber 2, r = 3 mm or more. Good. In the case of a low bending loss optical fiber, it can be realized with ω = 2 to 3 mm, which is less than half that of a general-purpose SM fiber. That is, the mounting length of the fiber crossing portion can be made shorter, and the optical fiber 1 can be fixed in the fiber fixing groove 8 even in the case of the substrate 3 with P = 5 mm. Is planned.

  The optical fiber used at the intersection of the optical fiber 1c can be realized by using an optical fiber that satisfies the above-mentioned conditions. However, in order to make it smaller and more integrated, a low bending loss SM fiber 13 is used. However, the length of the bent portion length ω can be shortened.

  FIG. 2A shows details of the portion A in FIG. 1 and shows an example of a mounting form of the optical element 2 mounted in the parallel groove (concave portion) X having the width S. The optical element 2 has a width K, and is provided with a mirror, a filter, and the like made of a dielectric multilayer film 12 on one end face. The relationship between each dimension and the coreless fiber length CL is CL · cos Θ> S> K (hereinafter referred to as Equation 2). Further, in order to fix and mount the optical element 2g, the coreless fiber 7 in the optical fiber 1a fixed and mounted in advance is cut by a dicing saw in accordance with the width S of the parallel groove X. Similarly, the coreless fiber 7 in the optical fiber 1b is cut by the dicing saw with respect to the optical element 2i, and the coreless fiber 7 in the optical fiber 1a is cut by the dicing saw with respect to the optical element 2h.

  It is preferable that a parallel groove X deeper than the groove 8 is formed at the intersection of the grooves 8. As a result, the optical element 2 can be accurately and stably installed, and the light emitted from the optical fiber 1 can be incident on the substantially central portion of the optical element 2, so that the optical effect of the optical element 2 is improved. Can be done. Such parallel grooves X for installing and fixing the optical element 2 may be processed in advance, but after the optical fiber 1 is fixedly mounted, parallel grooves with a width S and a depth E may be processed. In order to fill a gap on one side of the optical element 2, gel or UV adhesive is filled as the translucent resin 4. In particular, if the translucent resin 4 is made substantially equal to the refractive index 1.5 of the coreless fiber 7, the incident light from the coreless fiber 7 can be transmitted without reflection attenuation, and between the transmission / reflection GI lens fibers 6. Can be connected with low loss without causing optical axis misalignment at equal working distances CL.

  FIG. 2B shows an embodiment in which an inline type optical isolator is mounted as the optical element 2. In this case, the optical element 2 has an optical fiber 1 connected in an X shape, and has a function of transmitting incident light in two directions of the Pa direction and the Pb direction and blocking the return light. An optical element 2 having an optical isolator function is obtained by closely fixing a birefringent crystal plate 2a such as a rutile crystal on both sides of a Faraday rotator 2b and a half-wave plate 2c, and the width K is about 1.5 to 2 mm. Consists of.

  The optical fiber 1 used in the present invention may be composed of the GI lens fiber 6 at the tip facing the optical element 2 as well as the above-described embodiment. Accordingly, it is only necessary to fuse and connect the GI lens fiber 6 having a predetermined length between the SM fibers 5 or at the tip, and the optical fiber 1 having the lens connecting portion can be easily manufactured. In that case, in order to cut | disconnect the length of the GI lens fiber 6 correctly, it is necessary to install a GI lens fiber correctly with respect to the groove part of a board | substrate.

  More preferably, the coreless fiber 7 is further connected to the tip of the GI lens fiber 6 as in the above embodiment. As a result, the working distance between the GI lens fibers to be used can be accurately adjusted by the coreless fiber 7, a low-loss connection is possible, and the lens characteristics are stable.

  The optical circuit module of the present invention shown in FIG. 1 is configured as a four-wavelength optical multiplexer / demultiplexer and actually manufactured. The substrate 3 for mounting the optical fiber 1 has a length of 24 mm, a width of 5 mm, P = 6 mm, S = 1.5 mm, E = 0.3 mm, a thickness T = 1.5 mm, W = 1 mm, and Θ = 3 °. Three quartz glass substrates having three rows of fiber fixing grooves 8 each having a U-shaped cross section were prepared. The U groove depth is 110 μm. Unlike the V groove, the U groove can fix the optical fiber 1 by surface contact at the groove bottom surface. Therefore, when the optical fiber 1 is fixed with an adhesive or the like, the stress on the optical fiber 1 due to the shrinkage / expansion of the adhesive due to temperature fluctuations. The load is relaxed as compared to the V-groove that is in line contact, and temperature fluctuation characteristics such as polarization dependent loss due to the photoelastic effect caused by the load stress are reduced. Since four types of optical fiber 1 are manufactured as shown in FIGS. 5A to 5D, the GI lens fiber 6 has a clad diameter of 125 μm, a core diameter of 110 μm, and a relative refractive index difference Δ = 0. .85 were prepared and used by cutting to a length GL = 740 μm. As the coreless fiber 7, a quartz fiber having an outer diameter of 125 μm was prepared, and the coreless fiber 7 was cut into a length CL = 1.7 mm and DL = 0.7 mm. The SM fiber 5 was used after being cut to a length SL = 2.83 mm. The low bending loss SM fiber 13 is of the type of the low bending loss SM fiber 2 in FIG. 7, and is used at a bending radius r = 5 mm and ω = 2 mm. Each optical fiber 1 is prepared by manufacturing three optical fibers 1a, 1b, 1c, and 1d by sequentially fusion-connecting a GI lens fiber 6 and a coreless fiber 7 having the following predetermined length to the SM fiber 5 on one side. did.

  Next, the prepared optical fibers 1a to 1d were sequentially fixed to a predetermined position in the U groove on the mounting substrate 3 with a UV adhesive. The optical fiber 1c that bends to form an intersection is formed by bending the region of the low bending loss fiber 13 with ω = 2 mm at r = 5 mm, and the other portion is mounted and fixed in the fixing groove 8. The resulting loss is almost negligible. Thereafter, the coreless fiber 7 at the portion of the parallel groove X3 at a predetermined position where the optical element 2 on the substrate 3 is mounted was cut by a dicing saw.

  The optical element 2 to be used has a function of multiplexing / demultiplexing in which a dielectric multilayer filter 12 is deposited on one side of the type shown in FIG. 2A, and the thickness of the optical element 2 is K = 1.3 mm. This is an element of a quartz substrate of 1 mm square in length and width. It should be noted that the conditional expression (2) satisfies CL · cos Θ = 1.7> S = 1.5> K = 1.3.

  The optical element 2g reflects the wavelength of 1491 nm or less and transmits the wavelength of 1511 nm or more. The optical element 2h reflects light having a center wavelength of 1511 nm and transmits 1531 nm. The optical element 2i reflects light having a center wavelength of 1471 nm and transmits light having a wavelength of 1491 nm. As a result, among the multiple wavelength light incident from Pi, light having a wavelength of 1491 nm, light having a wavelength of 1511 nm from port P2, light having a wavelength of 1531 nm from port P3, and light having a wavelength of 1471 nm are emitted from port P4.

  The optical element 2 is fixed with a coreless fiber 7 on one side wall surface of the parallel groove X and a thin translucent UV adhesive, and a translucent gel 4 is filled in a gap portion. As shown in FIG. 2A, the mounting position of the optical element 2 is fixed so that the dielectric multilayer film is positioned at the end of the GI lens fiber 6 for each connection and CL / 2 = 0.85 mm. . In addition, since all materials including the optical fiber to be used are unified into a quartz system, the optical axis is not displaced, and the connection loss between the GI lens fibers 6 is about 0.2 dB / location. Thereafter, the substrate 3 on which the optical fiber 1 and the optical element 2 are mounted is fixed to a cylindrical or rectangular mounting case having a length of 30 mm to complete an optical circuit module.

Table 1 below shows a comparison between a characteristic example of an optical multiplexer / demultiplexer using the optical circuit module of the present invention and a bulk type characteristic example using a conventional filter element. It can be seen that the insertion loss and size have been greatly reduced, and that it has been miniaturized and integrated.

  In addition, this invention is not limited to the example of said embodiment, It does not have any trouble in making a various change within the range which does not deviate from the summary of this invention. For example, in the present embodiment, the optical multiplexer / demultiplexer has been shown to multiplex / demultiplex four-wavelength light in the wavelength band of C-WDM transmission. It is also possible to configure as an optical multiplexer / demultiplexer.

It is a top view which shows an example of embodiment of the optical circuit module of this invention. FIG. 2 is an enlarged view of an optical element section (A section) of the optical circuit module shown in FIG. 1, wherein (a) is an embodiment in which the optical element is a filter, and (b) is an optical element of an isolator. Example of the case. In the Example which showed the optical fiber crossing part (B part) of the optical circuit module shown in FIG. 1, (a) is the figure seen from the upper surface, (b) is the figure seen from the side surface. It is the figure which showed the Example of the board | substrate shape used for the optical circuit module of this invention. It is the figure which showed the structure of the optical fiber used for the optical circuit module of this invention, (a) showed the structural example of the optical fiber 1a of FIG. 1, (b) is the structural example of the optical fiber 1b of FIG. (C) shows a configuration example of the optical fiber 1c in FIG. 1, and (d) shows a configuration example of the optical fiber 1d in FIG. 4 is a graph showing the relationship between the bend radius r and the bend radius r of the optical fiber at the intersection shown in FIG. 3. It is the graph which showed the relationship between the bending radius r of the optical fiber of a crossing part, and bending loss. It is a figure of the conventional multi-core type filter module.

Explanation of symbols

1. 1. Optical fiber Optical element 3. Substrate 5. SM fiber 6. GI lens fiber Coreless fiber8. Groove 12. Multilayer filter 13. Low bending loss SM fiber

Claims (8)

A substrate having intersecting grooves on the main surface, and an optical fiber installed in the groove and intersecting each other so as to overlap each other at the intersection of the grooves,
An optical circuit module, wherein at least one of the optical fibers overlapping each other at the intersection is bent.   The optical circuit module according to claim 1, wherein a concave portion deeper than the groove is formed at an intersection of the grooves.   The optical circuit module according to claim 1, wherein an optical element is mounted on the main surface so as to face the tip of the optical fiber.   The optical circuit module according to any one of claims 1 to 3, wherein the optical fiber has a bending loss smaller than that of the remaining portion in the bent portion.   The optical circuit module according to claim 4, wherein the bent portion is formed of a holey fiber.   6. The optical circuit module according to claim 3, wherein the optical fiber has a GI lens fiber at a tip facing the optical element.   The optical circuit module according to claim 6, wherein a coreless fiber is further connected to a tip of the GI lens fiber.   8. The optical element according to claim 1, wherein the optical element has any one of a branching / coupling function, a filter function, a mirror function, a polarization function, a Faraday rotation function, an attenuation function, and an isolator function. The optical circuit module according to any one of the above.

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