JP2014199364A - Optical element module and optical axis adjustment method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element module capable of simultaneously performing optical axis adjustment and light intensity adjustment for polarization-combining two pieces of modulation light, and an optical axis adjustment method of the same.SOLUTION: There is provided an optical axis adjustment method of an optical element module that includes: polarization-combining means 22, 23 causing polarization planes of two pieces of modulation light L1, L2 emitted from first and second optical modulation parts to orthogonally intersect with one another to thereby combine the light; collimating means 3 condensing a light wave passing through the polarization-combining means into an optical fiber 8. A junction 10 between a housing 2 and lens holding means 4 and a junction 11 between the lens holding means 4 and an optical fiber holding means 6 each have junction surfaces of planar structure. The optical axis adjustment method adjusts light intensities of the two pieces of modulation light incident into the optical fiber 8 by a bonding step of performing laser welding simultaneously at least two or more points of around the junction, and by an adjustment step of adjusting an optical axis by performing laser welding on any one of the junction 10, the junction 11 or a thin-walled portion 7 of the optical fiber holding means 6.

Description

  The present invention relates to an optical element module and an optical axis adjusting method thereof, and more particularly to an optical element module formed by laser welding and joining a plurality of optical elements and an optical axis adjusting method thereof.

  In the optical communication field and the optical measurement field, an optical element module having an optical element such as an optical modulator and composed of a plurality of optical elements is frequently used. This optical element module is manufactured by welding and joining a plurality of optical elements. However, since high accuracy is required for adjusting the arrangement position of the optical elements at the time of manufacturing, an optical axis shift occurs. There are many things.

  In addition, each optical element constituting the optical element module is housed in a housing or held by a holding member, and the housing and the holding member are often assembled by welding, but the holding member is usually It is made of metal, and heat shrinks due to heat applied during welding, resulting in deformation.

  Then, even if it is assembled while adjusting so as not to cause an optical axis deviation, the module is thermally deformed during welding and the optical axis deviation occurs, resulting in a problem of deterioration of optical characteristics.

  With respect to the above problem, in Patent Document 1, an optical component having a curved surface and an optical component having a nodal surface are brought into contact with each other, and stress is applied to the contact portion while monitoring optical loss between the two optical components. The deterioration of the optical characteristics is corrected by irradiating the YAG laser to the portion where the optical loss is minimized.

  However, the contact portion in Patent Document 1 is a linear portion where the contact surface and the curved surface are in contact, that is, the contact between the two is a line contact. Since this line contact portion is irradiated and fixed by laser, it is fixed in an unstable state and lacks reliability as a module.

  In addition, a strong stress is generated in the part opposite to the part that has been heat-shrinked by welding for correction, and this stress remains as a residual stress after the entire module is fixed, and this residual stress is gradually released. As a result, the module is deformed over time, leading to deterioration of optical characteristics.

  Furthermore, since the welded portion is a line contact portion and is a very narrow region, the YAG laser may penetrate through the module during welding, which may cause splash (spray). When welding is attempted so that splash does not occur, a sufficient welding depth cannot be obtained and the strength cannot be ensured. Moreover, since the welding is fixed in a line contact state, the amount of deformation of the module increases even with a slight laser irradiation. Therefore, the difficulty of correction increases, leading to a decrease in productivity.

  In Patent Document 2, a plurality of components of a spatial optical system such as a polarization beam splitter (PBS) are arranged in order to adjust the polarization of the light wave propagating through the module. Thus, when the number of internal parts increases, the entire module tends to be large. The larger the module, the more pronounced the above problems. Further, in a module having a structure for branching light waves as in Patent Document 2, there is a problem that the optical loss of the module increases in order to adjust to a position for correcting the light intensity difference between the branched light waves.

  In particular, when two light waves emitted from two light modulators are combined so that their planes of polarization are orthogonal, a plurality of optical components intervene, resulting in a difference in light intensity between the two combined light waves. In addition to adjusting the optical axis, it is necessary to adjust not only the optical axis but also the light intensity, and the adjustment work of the optical components becomes more complicated. In addition, there is a method of adjusting the light intensity without depending on the adjustment of the optical component and performing the drive voltage amplitude control as described in Patent Document 3, but in this case, the control on the drive signal side becomes complicated. Therefore, it is inevitable to increase the size of the entire light modulation device including the optical element module and the driving device.

Japanese Patent No. 3938490 JP 2012-203282 A JP 2008-171634 A

  The problem to be solved by the present invention is to solve the above-mentioned problems, and to easily and accurately correct the optical axis misalignment, and to prevent a decrease in productivity and optical characteristics during the correction work. Another object of the present invention is to provide a highly reliable optical axis adjustment method for an optical element module. In particular, it is to provide an optical element module capable of simultaneously performing optical axis adjustment and light intensity adjustment when two modulated lights are polarized and combined, and an optical axis adjustment method thereof.

In order to solve the above problems, an optical element module and an optical axis adjustment method thereof according to the present invention have the following technical features.
(1) Polarization combining means for orthogonally combining the polarization planes of the two modulated lights emitted from the first and second light modulation sections, and condensing the light wave that has passed through the polarization combining means on the optical fiber In the optical axis adjustment method of the optical element module comprising the collimating means, the housing for housing the first and second light modulators and the polarization beam combining means, and the lens holding means incorporating the collimator means And an optical fiber holding means for holding an end portion of the optical fiber, and an optical fiber holding means set so that a part of a portion holding the optical fiber is thin, the casing And the lens holding means, and the joint part between the lens holding means and the optical fiber holding means, each of the bonding parts has a planar structure, and the bonding parts are joined together. At least two points around At any one of a joining step of performing laser welding at the same time, a joining portion between the housing and the lens holding means, a joining portion between the lens holding means and the optical fiber holding means, or a thin portion of the optical fiber holding means. An optical axis adjustment method for an optical element module, wherein the optical intensity of two modulated lights incident on the optical fiber is adjusted by an adjustment step of adjusting the optical axis by performing laser welding around the portion. is there.

(2) In the optical axis adjustment method of the optical element module according to (1), the joining step is characterized in that laser welding is simultaneously performed at three points at intervals of 120 degrees around the joint.

(3) In the optical axis adjustment method of the optical element module according to (1) or (2), the adjustment step includes a joint portion between the casing and the lens holding unit, the lens holding unit and the optical fiber. The stress for adjusting the optical axis is applied to a part of the periphery of the portion at either the joint with the holding means or the thin part of the optical fiber holding means, and the stress is a compressive stress. And laser welding.

(4) Polarization combining means for combining the two modulated lights emitted from the first and second light modulation sections with orthogonal polarization planes, and condensing the light wave that has passed through the polarization combining means on the optical fiber An optical element module including a collimating unit, a housing for housing the first and second light modulating units and the polarization combining unit, a lens holding unit incorporating the collimating unit, and the optical fiber. Optical fiber holding means for holding the end of the optical fiber, and optical fiber holding means set so that a part of the part holding the optical fiber is thin, the housing and the lens holding means And the joint portion between the lens holding means and the optical fiber holding means, each joint portion has a planar structure of the joint surface, and in order to join both, at least 2 around the joint portion. Laser welding at two or more points The optical axis of the two modulated lights incident on the optical fiber is not aligned, and the casing and the lens holding unit are used to adjust the light intensity of the two modulated lights incident on the optical fiber. The optical axis is adjusted by laser welding around the part at any one of the joining part with the means, the joining part between the lens holding means and the optical fiber holding means, or the thin part of the optical fiber holding means. It is characterized by.

  The present invention provides a polarization beam combining means for orthogonally combining the polarization planes of the two modulated lights emitted from the first and second light modulation sections, and collecting the light wave that has passed through the polarization wave combining means in an optical fiber. In an optical axis adjustment method of an optical element module including a collimating unit that emits light, a housing that houses the first and second light modulation units and the polarization beam combining unit, and a lens holding unit that incorporates the collimator unit And an optical fiber holding means for holding an end portion of the optical fiber, and an optical fiber holding means set so that a part of the portion holding the optical fiber is thin, In the joint portion between the body and the lens holding means, and the joint portion between the lens holding means and the optical fiber holding means, each joint portion has a planar structure, and the joint surfaces are joined together. At least two around the part Any one of a joining step of performing laser welding at the same time, a joining portion between the housing and the lens holding means, a joining portion between the lens holding means and the optical fiber holding means, or a thin portion of the optical fiber holding means An optical axis adjustment method for an optical element module, wherein the optical intensity of the two modulated lights incident on the optical fiber is adjusted by an adjustment step of adjusting the optical axis by performing laser welding around the portion. Therefore, with this planar structure of the joint surface, it is possible to easily and accurately adjust the optical axis of the optical element module by suppressing the yield reduction due to splash and the occurrence of deviation due to laser welding, as in the past. it can. In addition, since they are in contact with each other in a planar structure, deformation with time due to residual stress is suppressed, and deterioration of optical characteristics can be prevented.

  In addition, since laser welding is performed simultaneously at at least two or more points around the joint, misalignment due to laser welding is unlikely to occur. In particular, when laser welding is performed simultaneously at three points at 120 ° intervals around the joint, stresses generated by laser welding interfere with each other, and as a result, positional deviation is less likely to occur.

  Further, in fine adjustment of the optical axis, either the joint between the housing and the lens holding means, the joint between the lens holding means and the optical fiber holding means, or the thin portion of the optical fiber holding means, By performing laser welding on the periphery, more accurate adjustment is possible. In particular, by applying a stress for adjusting the optical axis to a part of the periphery of the part, and performing laser welding on the point where the stress is a compressive stress, the shape of each part is applied in a state where the stress is applied. It can be maintained.

  Moreover, when adjusting these optical axes, the optical axes are adjusted while adjusting the optical intensities of the two modulated lights incident on the optical fiber, so there is no need to separately adjust the optical intensity of each modulated light, Assembly / adjustment work can be easily performed.

It is the schematic explaining one Example of the optical element module to which the optical axis adjustment method of this invention is applied. It is a figure explaining the joining process which welds between each member in the optical element module to which the optical axis adjustment method of this invention is applied. It is a figure explaining the adjustment process which adjusts an optical axis in the optical element module to which the optical axis adjustment method of invention is applied. It is a figure explaining the example of the optical element module which carries out polarization composition of the light wave outputted from two modulation parts. It is a figure explaining the light intensity distribution of two light waves.

Hereinafter, the optical element module of the present invention and the optical axis adjustment method thereof will be described in detail using preferred examples. FIG. 1 is a diagram mainly showing a portion for adjusting the optical axis.
The light wave output from the optical element 1 is introduced into the optical fiber 8 by the collimator means 3 such as a lens. The optical element module further includes a housing 2 for housing the optical element 1, a lens holding means 4 incorporating the collimator means 3, and an optical fiber holding means for holding the end of the optical fiber 8. The optical fiber holding means 6 set so that one part (part shown with the code | symbol 7) of the holding | maintenance part becomes thin is provided.

  The first feature of the present invention is that each of the joint portions (10, 11) in the joint portion 7 between the housing 2 and the lens holding means 4 and the joint portion 11 between the lens holding means 4 and the optical fiber holding means 6. Has a planar structure on the joint surface.

  In the present invention, the meaning of “joint surface is a planar structure” means that the joint surfaces that are in contact with each other are in contact with each other in a state having a certain area or more. This means that a contact area enough to prevent splashing through the module is secured.

  Since the “joint surface is a planar structure”, even if the laser for adjusting the optical axis is irradiated, the module is sufficiently thick in the laser irradiation direction, causing the weld to shrink. Will not be deformed or splash will occur. Moreover, since each member has ensured sufficient contact area, it is suppressed that a shape changes with time by the stress which generate | occur | produced by laser welding.

  Next, a joining process for joining the joint portion 10 between the housing 2 and the lens holding means 4 and the joint portion 11 between the lens holding means 4 and the optical fiber holding means 6 by laser welding will be described. By using two or more lasers to be irradiated at the same time, the stress generated by laser welding works to interfere with each other and cancel each other, and as a result, the positional deviation of the joining member is suppressed.

  FIG. 2 is a view of the joints 10 and 11 in FIG. 1 as viewed in the optical axis direction, and illustrates an example in which three points are laser welded simultaneously. As shown in FIG. 2, by arranging the three welding points at intervals of 120 degrees, the stresses generated by laser welding interfere with each other and are uniformly applied to the entire joint. Even when the number of points to be laser welded is two or four or more, it is possible to suppress the displacement of the joining member by arranging the points to be welded so that the welding point is the target with respect to the center O. .

  In laser welding, any form such as using a plurality of YAG lasers or branching one YAG laser beam can be used. Also, when increasing the number of laser welding locations, the three points indicated by symbol A in FIG. 2 (each separated at equal intervals in the circumferential direction) are simultaneously irradiated and welded, followed by the YAG laser irradiation member and optical The position of the element module is relatively shifted, and the three points indicated by symbol B are irradiated and welded. Further, the three points indicated by reference symbol C are adjusted and irradiated in the same manner. Further, it is preferable to perform the welding while monitoring the light emitted from the optical element module during the welding operation and adjusting the optical axis of the optical element module so that the optical loss is minimized.

  In the joining process, the joining portion 7 between the housing 2 and the lens holding means 4 and the joining portion 11 between the lens holding means 4 and the optical fiber holding means 6 have been described mainly with respect to joining by laser welding. When the fiber 8 and the optical fiber holding means 6 are not completely joined, the thin portion 7 of the optical fiber holding means 6 can be fixed by irradiating three points of YAG laser as described above. . In such a case, alignment adjustment is performed while monitoring, and the thin portion 7 is first joined, then the joint portion 10 and finally the joint portion 11 are sequentially welded to perform the adjustment more efficiently. be able to.

  Next, an adjustment process for finely adjusting the optical axis will be described. In the adjustment step, the bonding portion 10 between the housing 2 and the lens holding means 4, the bonding portion 11 between the lens holding means 4 and the optical fiber holding means 6, or the thin portion 7 of the optical fiber holding means 6, Laser welding is performed around the part to adjust the optical axis.

  FIG. 3 shows the joining portion 10 between the housing 2 and the lens holding means 4, the joining portion 11 between the lens holding means 4 and the optical fiber holding means 6, or the thin portion 7 of the optical fiber holding means 6 from the rear axis direction. FIG. In the adjustment process, the optical axis is adjusted by applying a pressing force F to a part of the periphery of the joint portion (10, 11) or the thin portion (7). Stress is applied to the joints and the like by this pressing force, and welding is performed by irradiating the laser L to the portion opposite to the point where the pressing force F is applied, which is a point where the stress is a compressive stress. . As a result, the stress can be balanced and the shape can be maintained even when the pressing force F is released.

  In the adjustment step, the optical axis can be finely adjusted many times so as to minimize transmission loss. For this purpose, laser welding may be performed a plurality of times on each part.

  Next, a description will be given of an optical element provided in the housing 2 that includes a polarization beam combining unit that multiplexes two modulated lights emitted from the first and second light modulation units with their polarization planes orthogonal to each other. As shown in FIG. 4, the built-in optical element includes, for example, two Mach-Zehnder type waveguides arranged in parallel on the same substrate, and two modulation units. The light wave incident on the optical fiber 25 is branched into two and introduced into each modulation section. The light waves L1 and L2 emitted from each modulation unit are output as one light wave by the polarization beam combiner.

  As the polarization combining means, a polarization beam splitter (PBS) that combines a polarization rotation unit 22 such as a half-wave plate for rotating the polarization plane by 90 ° and two light waves (L1, L2) having orthogonal polarization planes. ) And the like. It is also possible to combine the polarization combining portions using a birefringent material.

  The optical element 21 and the polarization beam combining means (22, 23) provided with the modulation unit are accommodated in the housing 2 and are fixedly arranged. The optical axis adjustment method of the optical element module according to the present invention is characterized in that the optical axis is adjusted while adjusting the light intensities of the two light waves emitted from the two modulators.

  The optical system and holding means for introducing the light wave emitted from the polarization beam combining means into the optical fiber 8 using the collimator means 3 and the optical axis adjusting method are as described in FIGS. This embodiment can be used in the same manner.

The principle that the light intensity can be adjusted by adjusting the optical axis will be described with reference to FIG. The light waves (L1, L2) emitted from the two modulators are combined with the optical axis slightly shifted as shown in FIG. 5A due to the coupling loss of the polarization combining means and the positional adjustment. . At the position incident on the optical fiber, the optical axes of the two light waves are not completely coincident. When the light intensities of the two combined lights are viewed in the spatial intensity distribution of the portion indicated by the alternate long and short dash line X, one peak appears larger than the other as shown in FIG. The peak positions of the two light waves (the optical axes of the light waves) P ₀ and S ₀ are shifted from each other, but there are also positions where both have the same intensity. By aligning the optical axis of the optical fiber at such a position, the alignment is achieved. It is possible to make the two light intensities almost the same. Of course, it is also possible to realize a state where the light intensity ratio is not equal, such as 1: 2 or 1: 3.

  The cause of the deviation of the optical axes of the two light waves emitted from the polarization beam combining means is that optical components such as a modulation unit, a polarization rotation unit, and a polarization beam splitter (PBS) (when collimator lenses are arranged before and after the polarization rotation unit) This is because the positional relationship is deviated from the normal optical axis. The present invention can suitably adjust the light intensities of the two light waves particularly when such a positional deviation occurs. Of course, as in the case of adjusting the position of the collimator means and the optical fiber, it goes without saying that the light intensity of the two light waves changes by adjusting the position of the optical component on the housing side.

  When adjusting the optical axis, the two light waves (L1, L2) can be switched and emitted, and the optical intensity can be set by individually monitoring the light intensity. It is also possible to adjust the optical axis so that the light intensity ratio satisfies a predetermined condition by simultaneously detecting with the light receiving element.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described contents, and it is needless to say that the design can be changed as appropriate without departing from the gist of the present invention.

  According to the present invention, the optical axis deviation of the optical element module can be easily and accurately corrected, and the optical axis of the highly reliable optical element module does not cause a reduction in productivity or optical characteristics during the correction operation. An adjustment method can be provided. In particular, it is possible to provide an optical axis adjustment method for an optical element module capable of simultaneously performing optical axis adjustment and light intensity adjustment in the case of combining two modulated lights with polarization.

DESCRIPTION OF SYMBOLS 1 Optical element 2 Housing | casing 3 Lens 4 Lens holding means 5 Optical fiber holding pipe 6 Optical fiber holding means 7 Thin part 8 Optical fibers 10 and 11 Joint part 21 Optical element 22 Polarization rotation part 23 Polarization composition part 25 Input light fiber

Claims (4)

Polarization combining means for orthogonally combining the polarization planes of the two modulated lights emitted from the first and second light modulation sections, and collimating means for condensing the light wave that has passed through the polarization combining means on the optical fiber In an optical axis adjustment method of an optical element module comprising:
A housing that houses the first and second light modulators and the polarization beam combining means;
Lens holding means incorporating the collimator means;
An optical fiber holding means for holding an end of the optical fiber, and an optical fiber holding means set so that a part of a portion holding the optical fiber is thin;
In the joint portion between the housing and the lens holding means, and the joint portion between the lens holding means and the optical fiber holding means, each joint portion has a planar structure, and both are joined together. A joining step in which laser welding is simultaneously performed at at least two or more points around the joint;
Laser welding is performed around the portion at either the joint between the housing and the lens holding means, the joint between the lens holding means and the optical fiber holding means, or the thin portion of the optical fiber holding means. By the adjustment process to go and adjust the optical axis,
An optical axis adjustment method for an optical element module, comprising adjusting the light intensities of two modulated lights incident on the optical fiber.   2. The optical axis adjustment method for an optical element module according to claim 1, wherein in the joining step, laser welding is simultaneously performed at three points at intervals of 120 degrees around the joint portion. 3. Adjustment method.   3. The optical axis adjustment method for an optical element module according to claim 1, wherein the adjustment step includes a joint portion between the housing and the lens holding means, and a joint portion between the lens holding means and the optical fiber holding means. Or applying a stress for adjusting the optical axis to a part of the circumference of the thin portion of the optical fiber holding means, and performing laser welding at a point where the stress is a compressive stress. An optical axis adjustment method for an optical element module. Polarization combining means for combining two modulated lights emitted from the first and second light modulation sections with orthogonal polarization planes, and collimating means for condensing the light wave that has passed through the polarization combining means on an optical fiber In an optical element module comprising:
A housing that houses the first and second light modulators and the polarization beam combining means;
Lens holding means incorporating the collimator means;
An optical fiber holding means for holding an end of the optical fiber, and an optical fiber holding means set so that a part of a portion holding the optical fiber is thin;
In the joint portion between the housing and the lens holding means, and the joint portion between the lens holding means and the optical fiber holding means, each joint portion has a planar structure, and both are joined together. Laser welding is performed at at least two points around the joint,
The optical axis of the two modulated lights incident on the optical fiber does not coincide with each other, and the junction between the casing and the lens holding means is used to adjust the light intensity of the two modulated lights incident on the optical fiber. The optical axis is adjusted by laser welding around the portion of either the joint between the lens holding means and the optical fiber holding means or the thin portion of the optical fiber holding means. An optical element module.

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