JP4905252B2 - Optical communication module - Google Patents

Description

  The present invention relates to an optical communication module with little optical axis deviation due to temperature.

  Optical communication modules often include a plurality of optical semiconductor elements such as a light emitting element for transmission and a light receiving element for reception. An optical communication module including a plurality of optical semiconductor elements is equipped with a plurality of optical transmission optical fibers, such as a transmission optical fiber and a reception optical fiber, or connected to the optical fiber with an optical connector. Configured to be possible.

Japanese Patent No. 3134850 JP 2006-306113 A

  The present inventor is studying a configuration in which the plurality of optical transmission optical fibers are gathered together to transmit light from a plurality of optical semiconductor elements to one optical transmission optical fiber.

  For example, the optical communication module 61 under examination shown in FIG. 6 includes an optical semiconductor element 3 mounted at a plurality of locations on the ceramic substrate 2 and having an optical axis perpendicular to the ceramic substrate 2, and an optical axis of each optical semiconductor element 3. And a lens block 62 on which a reflection surface having a common reflection optical axis is formed.

  In the lens block 62, an external lens 7c positioned on the reflection optical axis is formed on an end surface perpendicular to the ceramic substrate 2, and each optical semiconductor element 3 (3a, 3a, 3b) was formed on the optical semiconductor element lens 7 (7a, 7b) located on the optical axis, and the reflecting surface 4 was formed at the intersection of the reflected optical axis and the optical axis of each optical semiconductor element 3. Is.

  Here, the optical semiconductor element 3 is a light emitting element 3a and a light receiving element 3b.

  A light-receiving element reflecting surface 4a that selectively reflects only transmitted light is formed at a position near the end face (the right-hand face in the drawing of the lens block 62) on the reflection optical axis, and a light-receiving element that reflects the received light at a position far from the end face. The reflective surface 4b for use shall be formed. Each reflecting surface 4 (4a, 4b) has an inclination of 45 degrees with respect to the ceramic substrate 2.

  An optical filter 16 that selectively reflects only the transmission light (wavelength λ1) of the light emitting element 3a and transmits the received light (wavelength λ2) received by the light receiving element 3b is installed on the light emitting element reflection surface 4a. ing. Here, the wavelengths λ1 and λ2 are different, and the optical filter 16 only needs to have a function of reflecting or transmitting according to the wavelength. In this embodiment, a multilayer filter is used.

  By the way, the lens block 62 is mainly made of acrylic resin, PC (polycarbonate) resin, COP (cycloolefin polymer) resin, PEI (polyetherimide), etc., and its temperature expansion coefficient is, for example, 60 ppm / ° C. is there. On the other hand, the ceramic substrate 2 is mainly made of ceramic and has a temperature expansion coefficient of, for example, 7 ppm / ° C. That is, the temperature expansion coefficient differs greatly between the lens block 62 and the ceramic substrate 2.

On the other hand, the operating temperature range of the optical communication module 61 is, for example, 0 to 80 ° C. For this reason, the lens block 62 and the ceramic substrate 2 cause a significant difference in size between the upper limit and the lower limit of the operating temperature range. As a specific example, at normal temperature (20 ° C.), the distance L1 between the optical semiconductor element lenses 7 in the lens block 62 is 5 mm, and the distance L2 between the optical semiconductor elements 3 in the ceramic substrate 2 is 5 mm. When the temperature reaches 70 ° C., the difference between the increase ΔL1 in the lens interval L1 and the increase ΔL2 in the element interval L2 is
ΔL1−ΔL2 = (60−7) ppm / ° C. × (80−20) ° C. × 5 mm
= 0.0159 mm (15.9 μm)
It becomes. In other words, at 80 ° C., the lens interval L1 and the element interval L2 are different by about 16 μm compared to 20 ° C.

  If a multimode optical fiber having a core diameter (diameter) of 50 μm is used, a light beam having a diameter (φ) of 40 μm is emitted from the multimode optical fiber (see FIG. 8). When this light beam is imaged 1: 1 with the light receiving element lens 7b, the light beam is incident on the light receiving element 3b with a spot size of φ40 μm.

  On the other hand, the light receiving diameter (diameter) of a photodiode (PD) which is an example of the light receiving element 3b used for optical communication with a transmission rate of 10 Gbit / sec class is currently 60 μm. Therefore, assuming that the optical axis of a VCSEL (surface emitting laser), which is an example of the light emitting element 3a, is fixedly coincident with the optical axis of the lens 7 for the optical semiconductor element regardless of the temperature, the PD at 80 ° C. Is shifted from the optical axis of the lens 7 for the optical semiconductor element by about 16 μm, the spot size (diameter) of the received light incident on the PD is 40 μm, so that it protrudes from the light receiving diameter of the PD. For this reason, a large loss is received by the temperature change (see FIG. 7).

  Accordingly, an object of the present invention is to solve the above-described problems and provide an optical communication module with little optical axis deviation due to temperature.

In order to achieve the above object, an optical communication module of the present invention includes an optical semiconductor element mounted at a plurality of locations on a ceramic substrate and having an optical axis perpendicular to the surface of the ceramic substrate, and is common on the optical axis of each optical semiconductor element. A split lens block formed with a reflective surface having a reflective optical axis, and a gap separating the split lens blocks in the reflective optical axis direction, each of the split lens blocks being attached to the ceramic substrate ; It is.

In each of the divided lens blocks , a surface facing the gap may be inclined at a right angle with respect to the reflected optical axis.

  The gap may be filled with a filler that is softer than the divided lens block and has a refractive index close to that of the divided lens block compared to air.

  The divided lens blocks may be attached to the ceramic substrate via individual height adjustment spacers.

The optical communication module of the present invention includes an optical semiconductor element mounted at a plurality of locations on a ceramic substrate and having an optical axis perpendicular to the ceramic substrate, and a reflection having a common reflected optical axis on the optical axis of each optical semiconductor element. A lens block having a surface formed thereon and a split groove formed on a side surface of the lens block opposite to the ceramic substrate , the lens block being attached to the ceramic substrate .

  The present invention exhibits the following excellent effects.

  (1) Little optical axis shift due to temperature.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, an optical communication module 1 according to the present invention includes an optical semiconductor element 3 mounted at a plurality of locations on a ceramic substrate 2 and having an optical axis perpendicular to the surface of the ceramic substrate 2, and each optical semiconductor element 3. Are provided with a divided lens block 5 in which a reflecting surface 4 having a common reflected optical axis is formed on the optical axis, and a gap 6 that separates the divided lens blocks 5 in the direction of the reflected optical axis.

  Here, the optical semiconductor element 3 is a light emitting element 3a and a light receiving element 3b.

  A reflection surface 4a for the light emitting element 3a that selectively reflects only the transmitted light is formed at a position near the end surface S1 (the right surface of the divided lens block 5 on the right side in the drawing) on the reflection optical axis, and is received at a position far from the end surface. It is assumed that a reflection surface 4b for the light receiving element 3b that reflects light is formed. Each reflecting surface 4 (4a, 4b) has an inclination of 45 degrees with respect to the ceramic substrate 2.

  And the optical filter 16 is installed in the reflective surface 4a. The function of the optical filter 16 is the same as that in FIG. 6 and is as described above.

  The divided lens block 5 on which the reflecting surface 4a is formed is referred to as a light emitting side lens block 5a, and the divided lens block 5 on which the reflecting surface 4b for the light receiving element 3b is formed is referred to as a light receiving side lens block 5b.

  The light emitting side lens block 5 a has an external lens 7 c positioned on the reflection optical axis on the end surface perpendicular to the ceramic substrate 2, and the optical axis of the light emitting element 3 a on the bottom surface parallel to the ceramic substrate 2. The anti-light-emitting element lens 7a located above is formed. The light receiving side lens block 5b is formed with a counter light receiving element lens 7b positioned on the optical axis of the light receiving element 3b on the bottom surface parallel to the ceramic substrate 2.

  It can be said that the divided lens block 5 is obtained by dividing the lens block in the optical communication module of FIG. Both split lens blocks are made of resin as the main material in the same manner as the lens block in the optical communication module of FIG.

  The operational effects of the above configuration will be described.

  Similarly to the above, at room temperature (20 ° C.), the distance L1 between the light-receiving semiconductor element lens 7 (the light-emitting element lens 7a and the light-receiving element lens 7b) in the split lens block 5 is 5 mm, and the ceramic substrate. The interval L2 between the optical semiconductor elements 3 in 2 is 5 mm. Assuming that the optical axis of the light emitting element 3a is fixedly coincident with the optical axis of the light emitting element lens 7a regardless of the temperature, the optical axis of the light emitting element 3a is at 80 ° C. Coincides with the optical axis.

  As the temperature rises, the light emitting side lens block 5a expands toward the light receiving side lens block 5b. However, since there is a gap 6 between the light emitting side lens block 5a and the light receiving side lens block 5b, the light emitting side lens block 5a expands. Does not affect the light receiving side lens block 5b.

  On the other hand, the light-receiving side lens block 5b also expands, but is separate from the light-emitting side lens block 5a and has a gap 6 between it and the light-emitting side lens block 5a. It can be assumed that the optical axis of the element lens 7b is fixedly matched regardless of the temperature. At this time, the optical axis of the light receiving element 3b coincides with the optical axis of the lens 7b for the light receiving element even at 80 ° C.

  Therefore, both the lens interval L1 and the element interval L2 remain approximately 5 mm even at 80 ° C., the optical axis shift between the anti-light-receiving element lens 7b and the light-receiving element 3b, and the anti-light-emitting element lens 7a and the light-emitting element 3a. There is no optical axis misalignment.

  Actually, even though the optical axis of the optical semiconductor element 3 is not fixedly coincident with the optical axis of the lens 7 for the optical semiconductor element regardless of the temperature, both the divided lens blocks 5 are formed individually, Since there is a gap 6 between the two divided lens blocks 5 having a large temperature expansion coefficient, the difference in temperature between the lens interval L1 and the element interval L2 is alleviated. The size of the gap 6 is sufficient as long as it exceeds the size of the two divided lens blocks 5 that expand in the direction of the gap 6.

  Next, other features and effects of the embodiment of FIG. 1 will be described.

  In the light emitting side lens block 5a and the light receiving side lens block 5b, the surfaces facing the gap 6 are inclined at right angles to the reflected optical axis. The surfaces of the two divided lens blocks 5 facing the gap 6 are parallel to each other and have an inclination of 5 to 15 degrees with respect to a virtual surface perpendicular to the reflected optical axis.

  Since the surface facing the gap 6 is inclined at a right angle to the reflected optical axis in this way, the light emitted from the divided lens block 5 to the gap 6 is partially reflected by the surface of the divided lens block 5 facing the surface. Sometimes this partially reflected light deviates from the normal reflected optical axis. Therefore, communication failure due to partially reflected light can be prevented.

  As shown in FIG. 2, the gap 6 of the optical communication module 1 may be filled with a filler 8 that is softer than the divided lens block 5 and has a refractive index close to that of the divided lens block 5 compared to air. The filler 8 is, for example, a silicone resin having a refractive index substantially equal to that of the resin of the split lens block 5.

  As described above, the gap 6 is filled with the filler 8 having a refractive index close to that of the divided lens block 5 compared to air, so that the light emitted from the divided lens block 5 to the gap 6 is opposed to the divided lens block. When incident on 5, less light is partially reflected. On the other hand, since the filler 8 is softer than the divided lens block 5, when both the divided lens blocks 5 expand in the direction of the gap 6, the filler 8 is easily deformed to give a position shift or distortion to the divided lens block 5. There is no.

  Further, since the gap 6 is filled with the filler 8, dust and moisture from the outside of the optical communication module 1 do not enter the gap 6, and communication failure due to these foreign matters can be prevented.

  In the present invention, since the lens interval L1 and the element interval L2 are formed as wide as 5 mm, noise generated by a high frequency driving current (for example, about several tens mA) of several GHz or more of a light emitting element driver (not shown) that drives the light emitting element 3a is generated. It is possible to prevent the weak output (for example, about several μA) of the light receiving element 3b from being affected.

  Furthermore, in the present invention, the electromagnetic wave absorber 15 (see FIG. 2) is disposed between the light emitting element 3a and the light receiving element 3b as a modification by forming the lens interval L1 and the element interval L2 as wide as 5 mm. Becomes easy. Due to the electromagnetic wave absorber 15, noise generated by a driving current (for example, about several tens mA) of a light emitting element driver (not shown) that drives the light emitting element 3 a affects a weak output (for example, about several μA) of the light receiving element 3 b. Can be effectively prevented. As the electromagnetic wave absorber 15, a material formed by combining carbon or ferrite with rubber or urethane is used. The width is about 2 mm, and the thickness is equal to the distance between the surface of the ceramic substrate 2 and the lens blocks 5 a and 5 b. Processed to 5 mm.

  As shown in FIG. 3, the divided lens block 5 may be attached to the ceramic substrate 2 via a height adjusting spacer 9. The height adjusting spacer 9 is inserted between the ceramic substrate 2 and the divided lens block 5 in order to adjust the distance between the optical semiconductor element 3 and the lens 7 for the optical semiconductor element.

  As shown in FIG. 4, the light emitting side lens block 5a and the light receiving side lens block 5b are preferably attached to the ceramic substrate 2 via individual height adjusting spacers 9a and 9b. Thereby, the distance between the light emitting element 3a and the light emitting element lens 7a and the distance between the light receiving element 3b and the light receiving element lens 7b can be individually adjusted.

  The height adjusting spacer 9 may be formed of ceramic or the same resin as that of the divided lens block 5. When the height adjusting spacer 9 is formed of ceramic, the temperature expansion coefficient is the same as that of the ceramic substrate 2, and therefore the height of the height adjusting spacer 9 and the ceramic substrate 2 are equal regardless of the temperature. Accordingly, the height adjusting spacer 9 may be integrated (that is, not divided) with the portion on which the light emitting side lens block 5a is placed and the portion on which the light receiving side lens block 5b is placed.

  When the height adjusting spacer 9 is formed of the same resin as that of the divided lens block 5, the temperature expansion coefficient is the same as that of the divided lens block 5 and is different from that of the ceramic substrate 2. Therefore, the light emitting side lens block 5a is mounted. The part and the part on which the light receiving side lens block 5b is placed may be divided separately. At this time, the light receiving side lens block 5b and its height adjusting spacer 9b can be integrally formed, and the light emitting side lens block 5a and its height adjusting spacer 9a can be integrally formed. This eliminates the need for height adjustment and facilitates manufacturing.

  Next, another embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 5, the optical communication module 11 according to the present invention includes an optical semiconductor element 3 mounted at a plurality of locations on a ceramic substrate 2 and having an optical axis perpendicular to the ceramic substrate 2, and each optical semiconductor element 3. The lens block 12 is provided with a reflection surface 4 having a common reflection optical axis on the optical axis, and a split groove 13 formed on the side surface of the lens block 12 opposite to the ceramic substrate 2.

  Since the ceramic substrate 2 and the optical semiconductor element 3 are the same as those in FIG. 1, the description is omitted, and the lens block 12 and its dividing groove 13 will be described.

  Unlike the lens block 12 shown in FIG. 1, the light emitting side and the light receiving side are integrated. However, unlike the structure shown in FIG. The split groove 13 does not completely divide the light emitting side and the light receiving side of the lens block 12, but divides only the surface opposite to the ceramic substrate 2 so as to be integrally connected on the bottom surface facing the ceramic substrate 2. Is.

  When the dividing groove 13 is formed integrally with the lens block 12 using a mold, the width of the dividing groove 13 in the optical axis direction is set to 0.5 mm or more in order to prevent mold deformation.

  When the ceramic substrate 2 and the lens block 12 expand due to the temperature rise, the lens block 12 expands more than the ceramic substrate 2 due to the difference in temperature expansion coefficient. As shown in FIG. 3, since the ceramic substrate 2 and the lens block 12 are fixed via the height adjusting spacer 9, a force acts on the bottom surface of the lens block 12 in a contracting direction.

  At this time, the state in which the optical axis of the light emitting element 3a coincides with the optical axis of the lens 7a for the light emitting element and the state in which the optical axis of the light receiving element 3b coincides with the optical axis of the lens 7b for the light receiving element. Maintained. Therefore, a communication failure due to a shift between the optical semiconductor element 3 and the lens 7 for the optical semiconductor element is avoided.

  Since the ceramic substrate 2 has higher rigidity than the lens block 12, deformation caused by the expansion difference mainly occurs in the lens block 12. If the split groove 13 is not provided, the lens block 12 expands greatly, while the expansion of the ceramic substrate 2 is small. Therefore, compressive stress is applied to the lens block 12 mounted on the ceramic substrate 2. For this reason, since the lens block 12 is shrunk to an unbalance from the original shape, the optical axis does not pass through a predetermined route. However, if there is the split groove 13, the force concentrates on the thin portion 14 at the bottom of the split groove 13, and only the thin portion 14 is distorted, so that the distortion of the lens block 12 as a whole can be reduced. This is obvious from the fact that the lens block 12 is divided into two when considering that the thin portion 14 of the lens block 12 is made extremely thin. Therefore, the amount of displacement of the optical axis of the lens block 12 can be reduced.

  Considering that the thin portion 14 of the lens block 12 is formed by a mold, the thinness limit of the thin portion 14 of the lens block 12 is 50 μm. Further, when the thin portion 14 of the lens block 12 becomes thick as described above (that is, when the height direction of the split groove 13 is reduced), the stress applied to the lens block 12 is increased. The thin portion 14 is preferably thin, and is desirably 1/10 or less of the height h of the lens block 12 (see FIG. 5). In the present embodiment, the thickness of the thin portion 14 of the lens block 12 is 50 μm.

It is a sectional side view of the optical communication module which shows one Embodiment of this invention. It is a sectional side view of the optical communication module which shows one Embodiment of this invention. It is a front view of the optical communication module which shows one Embodiment of this invention. It is a perspective view of the optical communication module which shows one Embodiment of this invention. It is a sectional side view of the optical communication module which shows other embodiment of this invention. It is a sectional side view of the optical communication module which this inventor is examining. It is a figure explaining the relationship between a spot size and a light-receiving diameter. It is a figure explaining spot size.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical communication module 2 Ceramic substrate 3 Optical semiconductor element 4 Reflecting surface 5 Divided lens block 6 Gap 7 Lens for optical semiconductor element 8 Filler 9 Height adjustment spacer

Claims (5)

An optical semiconductor element mounted on a plurality of locations on a ceramic substrate and having an optical axis perpendicular to the surface of the ceramic substrate;
A split lens block in which a reflective surface having a common reflected optical axis is formed on the optical axis of each optical semiconductor element;
A gap separating each of the divided lens blocks in the direction of the reflected optical axis ,
An optical communication module , wherein each of the divided lens blocks is attached to the ceramic substrate . 2. The optical communication module according to claim 1 , wherein each of the divided lens blocks has a surface facing the gap that is inclined at a right angle with respect to the reflected optical axis.   3. The optical communication module according to claim 1, wherein the gap is filled with a filler that is softer than the divided lens block and has a refractive index close to that of the divided lens block compared to air.   The optical communication module according to claim 1, wherein each of the divided lens blocks is attached to the ceramic substrate via an individual height adjusting spacer. An optical semiconductor element mounted at a plurality of locations on the ceramic substrate and having an optical axis perpendicular to the ceramic substrate;
A lens block in which a reflection surface having a common reflection optical axis is formed on the optical axis of each optical semiconductor element;
A split groove formed on the side opposite to the ceramic substrate of the lens block ,
The optical communication module , wherein the lens block is attached to the ceramic substrate .

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