JP2010039115A - Optical module and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a one package type bidirectional optical module excellent in optical isolation.
An optical module includes a filter, a light receiving element, a light emitting element, a block, and a package. The filter has a characteristic of transmitting light having the first wavelength and reflecting light having the second wavelength. The light receiving element receives the light having the first wavelength transmitted through the filter. The light emitting element emits light of the second wavelength so as to be reflected by the filter. A block is a component for mounting a filter. The block has a slope on which the filter is mounted. This slope is along a plane that intersects the light emitting direction of the light emitting element and the light passing direction of the first wavelength. The block provides a space through which light having the first wavelength transmitted through the filter passes. This space forms at least a part of a triangle in a cross section orthogonal to the passing direction of light of the first wavelength.
[Selection] Figure 9

Description

  The present invention relates to a single-core bi-directional optical module and a method for manufacturing the same that enable bi-directional transmission and reception optical communication with respect to a single fiber. In particular, the light-emitting device and the light-receiving device are accommodated in a single housing. The present invention relates to a single package type single-core bidirectional optical module and a manufacturing method thereof.

  Urban-type optical communication systems are becoming popular. In this system, in order to effectively use the existing fiber, a form in which both transmission and reception are performed by changing the wavelength is adopted. That is, transmission is performed using signal light having a wavelength of 1.31 μm, and reception is performed using signal light having a wavelength of 1.49 μm or 1.55 μm. These signals are all intended for transmission and reception of digital signals. Furthermore, a system for transmitting an analog signal such as a video signal through the same fiber has been proposed. Such a system is a system using signal light having a wavelength of 1.55 μm as an analog optical signal and signal light having a wavelength of 1.49 μm as a digital optical signal.

  As a bidirectional module used in such a system, a transmission module in which a light emitting element is mounted in a casing and a receiving module in which a light receiving element is mounted in another casing are combined with a WDM unit (wavelength multiplexing / demultiplexing unit). There are some that are assembled together. In such a bi-directional module, the work of assembling the transmission module and the reception module together is necessary, and the cost becomes high. In addition, since such a bidirectional module uses two separate casings, the size thereof is large.

  As a solution to the above problems, a single package type bidirectional optical module has been proposed in which a light emitting element such as a semiconductor laser and a light receiving element such as a photodiode are accommodated in one casing.

  As a single package type bidirectional optical module, for example, one disclosed in Patent Document 1 is known. The optical module disclosed in Patent Document 1 includes a semiconductor laser (LD), a photodiode (PD), a WDM filter, a preamplifier, a cover, and a package. The LD, PD, WDM filter, preamplifier, and cover are accommodated in the package.

  The light emitted from the LD is emitted parallel to the stem of the package, reflected by the WDM filter, bent at a substantially right angle with respect to the stem, collected by the lens, and then coupled to the optical fiber. On the other hand, the light emitted from the optical fiber is collected by a lens, passes through a WDM filter, and enters a PD mounted on the stem.

  In one package type bidirectional optical module, electrical crosstalk and glossy crosstalk between the transmitter and the receiver are always a problem. That is, the LD generates signal light synchronized with On / Off by modulating a large current (On / Off). It is essential that electromagnetic induction noise is generated by turning on / off a large current. The PD receives extremely weak light and converts it into an electrical signal, but the drive current of the LD affects the reception state of the PD.

  In addition, light emitted from the LD may be irregularly reflected in the package before being combined with the optical fiber to become stray light, and part of the stray light may enter the PD. Since the PD generally has reception sensitivity even in the wavelength band of the emitted light from the LD, stray light may interfere with the reception state of the PD.

In the optical module disclosed in Patent Document 1, the PD and the preamplifier are covered with a conductive cover provided inside the package. A hole is provided in a part of the cover, and a WDM filter is attached to the cover so as to close the hole. In this optical module, an electrical isolation and an optical isolation between the transmission unit and the reception unit are attempted by this cover.
JP 2004-133463 A

  One package type bidirectional optical module is required to further improve the characteristics of electrical isolation and optical isolation.

  In particular, an object of the present invention is to provide a one-package bidirectional optical module excellent in optical isolation. Another object of the present invention is to provide a method for manufacturing a one-package bidirectional optical module.

  The inventor of the present application has found that even in the optical module disclosed in Patent Document 1, a part of stray light may enter the PD. As a result of studying this phenomenon, the inventor of the present application has found that the shape of the hole of the cover affects the incidence of stray light on the PD. The present invention has been made based on such knowledge.

  The optical module of the present invention includes a filter, a light receiving element, a light emitting element, a block, and a package. The filter has a characteristic of transmitting light having a first wavelength emitted from one fiber and reflecting light having a second wavelength different from the first wavelength. The light receiving element is an element that receives light of the first wavelength that has passed through the filter and outputs a photocurrent corresponding to the amount of the light. The light emitting element is an element that emits light of the second wavelength toward the filter. A block is a component for mounting a filter. The block has a slope. This slope is along a plane that intersects both the light emitting direction of the light emitting element and the light passing direction of the first wavelength. The filter is mounted on this slope. The package contains a filter, a light receiving element, a light emitting element, and a block. The block provides a space through which light having the first wavelength transmitted through the filter passes. This space forms at least a part of a triangle in a cross section orthogonal to the passing direction of light of the first wavelength.

  In general, a space provided in a block or cover, that is, a hole, has a circular cross-sectional shape in order to allow light having a first wavelength transmitted through a filter to pass therethrough. The surface that defines the circular cross-sectional hole reflects light in all directions. Therefore, part of the stray light reflected by the surface may be received by the light receiving element.

  On the other hand, since the cross section of the space provided by the block of the present invention forms a part of a triangle, the surface of the block defining this space can reflect light only in a specific direction. Therefore, the optical module of the present invention can reflect the light entering the space in a direction different from the direction toward the light receiving element.

  The block may have the following configuration: That is, the block may have two planes that define the space described above. The two planes extend in the direction of passage of light of the first wavelength, and are provided so that the space between the two planes becomes narrower as the distance from the light emitting element increases.

  The optical module of the present invention may have the following configuration. That is, the package has a mounting surface on which the light receiving element is mounted. The block may have a pair of side walls, a support portion, and a first bottom surface. The support part is located between the pair of side walls. The first bottom surface is a surface in contact with the mounting surface. The support portion provides the slope. The support portion includes a second bottom surface between the mounting surface and the inclined surface. The second bottom surface is separated from the mounting surface. The second bottom surface and the pair of side walls define a space in which the light receiving element is disposed. According to this configuration, the isolation between the light emitting element and the light receiving element is further ensured by the block.

  The distance between the mounting surface and the tops of the pair of side walls is preferably smaller than the distance between the mounting surface and the slope. In this configuration, since the height of the side wall is smaller than that of the inclined surface, the stray light reflected by the surface defining the space through which the light of the first wavelength passes can be released to the space above the top of the side wall.

  The optical module further includes a metal mounting member for mounting the light emitting element, and the mounting member is placed between the pair of side walls to define the above-described space in which the light receiving element is disposed. Preferably it is. In this configuration, since the metal mounting member is interposed between the light receiving element and the light emitting element, the isolation between the light receiving element and the light emitting element becomes more reliable.

  It is preferable that an optical filter for blocking light having the second wavelength is provided on the second bottom surface. According to this configuration, the optical isolation between the light emitting element and the light receiving element is more reliable. The optical axis of the wavelength cut filter is preferably parallel to the optical axis of the light receiving element.

  Another aspect of the present invention relates to a method of manufacturing an optical module. This method includes (a) a step of arranging the light emitting element and the light receiving element at respective predetermined positions, and (b) a step of moving a block on which the filter is mounted. And a step for reflecting light of a second wavelength from the light emitting element. In the step of moving the block, in the image observed by the image acquisition device arranged on the optical axis of the light receiving element, the image of the light receiving element and the image of the light emitting element acquired through reflection by the filter have a predetermined positional relationship. The block is moved so that

  As described above, according to the present invention, a one-package bidirectional optical module excellent in optical isolation is provided. Also, a manufacturing method suitable for manufacturing a one-package bidirectional optical module is provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a partially cutaway perspective view of a bidirectional optical module according to an embodiment. FIG. 2 is a plan view showing the optical module shown in FIG. 1 with the cap removed. The plan view shown in FIG. 2 is a plan view of the optical module as viewed from the lens side. The optical module 1 shown in FIGS. 1 and 2 includes a package 10, a light receiving element 12, a light emitting element 14, a WDM filter 16, and a block 18.

  The package 10 is a component for mounting and housing components such as the light receiving element 12, the light emitting element 14, the WDM filter 16, and the block 18. The package 10 includes a stem 10a, a plurality of lead pins 10b, a cap 10c, and a lens 10d.

  The stem 10a is a substantially disk-shaped metal member. The stem 10 a has a mounting surface 10 e for mounting components such as the light receiving element 12, the light emitting element 14, the WDM filter 16, and the block 18. The stem 10a has a plurality of holes, and a plurality of lead pins 10b pass through these holes. An insulating sealing member, for example, a seal glass is provided between the stem 10a and the lead pin 10b. Devices such as the light receiving element 12 and the light emitting element 14 are electrically connected to the lead pins 10b.

  The cap 10c is a substantially cylindrical metal member. The cap 10c has one end fixed to the mounting surface 10e and the other end holding the lens 10d. The cap 10c can be fixed to the stem 10a by, for example, projection welding. A gap between the lens 10d and the other end of the cap 10c is sealed with a sealing member such as a seal glass.

  The light receiving element 12 is a photodiode (PD). The PD 12 receives the first wavelength light emitted from the single optical fiber OF and transmitted through the lens 10d by the WDM filter 16, and outputs a photocurrent corresponding to the amount of the light. The first wavelength is, for example, 1.49 μm or 1.55 μm.

In the optical module 1, the PD 12 is mounted via the submount 20 on the mounting surface 10e of the stem 10a and substantially at the center of the mounting surface 10e. The optical module 1 further includes a preamplifier 22. The preamplifier 22 is disposed in the vicinity of the PD 12, amplifies the photocurrent generated by the PD 12, and outputs a complementary output voltage signal. The output voltage signal of lead pins 10b, via the lead pin 10b ₁ of two arranged on both sides of the pre-amplifier 22 is taken out of the module. That is, on both sides of the preamplifier 22 in the direction intersecting the direction PD12 and preamplifier 22 are arranged, two of the lead pin 10b ₁ is provided. Thus, pre-amplifier 22, in the center of the triangle (isosceles triangle) formed by the two lead pins 10b ₁ and PD 12, and is directly mounted on the stem 10a.

  The light emitting element 14 is a semiconductor laser (LD), and emits light of the second wavelength. The wavelength of the light emitted from the LD 14 is, for example, 1.31 μm. The light emitted from the LD 14 travels substantially parallel to the mounting surface 10e, is reflected by the filter 16, changes its direction by about 90 degrees, and is collected by the lens 10d. After being collected by the lens 10d, the light from the LD 14 is coupled to a single optical fiber OF.

The LD 14 is disposed at a position opposite to the position where the PD 12 is provided with respect to the block 18. That is, the LD 14 is provided so that the block 18 is positioned between the LD 14 and the PD 12. The LD 14 is mounted on the mounting surface 10e via the LD submount 24 and the wiring board 26 at the position. And wiring on the wiring board 26 are connected by the bonding wires and the lead pins 10b ₂ for LD of the lead pin 10b.

The distal end of the lead pin 10b ₃ positioned on the rear side of the LD14 of the lead pin 10b, PD28 is mounted directly. The PD 28 receives the back light of the light emitted from the LD 14 and outputs a photocurrent corresponding to the amount of the back light. The output signal of the PD 28 is used to automatically control the driving condition of the LD 14 so as to keep the intensity of the light emitted from the LD 14 constant. Therefore, the PD 28 is called a monitor PD. Further, this control is a control called APC (Auto-Power Control).

Tip of the lead pin 10b ₃ for mounting the monitor PD28 is slightly bent at an angle of, for example, 20 to 30 °. This is to prevent the back light of the LD 14 from being reflected by the surface of the monitor PD 28 and entering the LD 14 again as return light, and the return light becoming a noise source of the LD 14.

  In the present optical module 1, a block 18 is provided between the receiving unit (the part on which the PD 12 is mounted) and the transmitting unit (the part on which the LD 14 is mounted). The block 18 is made of a conductive material such as metal. One surface of the block 18 is inclined with respect to the mounting surface 10e, and the WDM filter 16 is attached to the surface, thereby realizing an optical system required for the reception unit, the transmission unit, and the WDM filter 16. ing.

  Thus, the isolation between the receiving unit and the transmitting unit is realized by sandwiching the block 18 between the receiving unit and the transmitting unit. That is, the electrical isolation between the receiving unit and the transmitting unit is realized by the conductivity of the block 18. In addition, a system in which light emitted from the LD 14 does not enter the PD 12, that is, optical isolation, is realized by a configuration provided by the block 18 described later.

  Hereinafter, the block 18 will be described in detail. 3 and 4 are perspective views showing an example of a block. FIG. 3 is a perspective view of the block 18 as viewed from above, and FIG. 4 is a perspective view of the block 18 as viewed from below. FIG. 5 is a perspective view showing a part of the block shown in FIG.

  The block 18 has a pair of side walls 18a, a central wall 18b, and a support portion 18c. The central wall 18b and the support portion 18c are located between the pair of side walls 18a. The upper surface 18d of the block is defined by a pair of side walls 18a and a support portion 18c. The first bottom surface 18e of the block is defined by a pair of side walls 18a and a central wall 18b, and has a substantially H-shaped planar shape. The first bottom surface 18e is a surface that contacts the mounting surface 10e of the stem 10a.

The support portion 18c includes a slope 18f. The inclined surface 18f is inclined downward from the upper surface 18d and continues to the top of the central wall 18b. Slopes 18f is a surface intersecting the exit direction _{Z L} and passing direction Z of the first wavelength light LD 14. A WDM filter 16 is mounted on the slope 18f.

  The support portion 18c includes a second bottom surface 18g. The second bottom surface 18g is located between the mounting surface 10e of the stem 10a and the inclined surface 18f when the block 18 is mounted on the stem 10a. The second bottom surface 18g faces the mounting surface 10e of the stem 10a and is separated from the mounting surface 10e. That is, the distance from the second bottom surface 18g to the upper surface 18d is shorter than the distance from the first bottom surface 18e to the upper surface 18d.

  The support portion 18c provides a space 18h extending from the slope 18f to the second bottom surface 18g. In the present embodiment, the space 18h is a through hole. The space 18h is a space through which light having the first wavelength emitted from the optical fiber OF passes.

  An optical filter 30 is attached to the second bottom surface 18g so as to close the through hole 18h. The optical filter 30 has a characteristic of blocking light of the second wavelength. Therefore, even if light from the LD 14 is diffusely reflected and tries to pass through the block 18, it is blocked by the optical filter 30. In the present embodiment, the second bottom surface 18g and the mounting surface 10e are substantially parallel, and the optical axis of the optical filter 30 mounted on the second bottom surface 18g is parallel to the optical axis of the PD 12. It has become.

Central wall 18b extends along a plane intersecting the exit direction _{Z L} of the light LD 14. The central wall 18b defines a space 18i and a space 18j. The space 18i is a space located between the LD 14 and the central wall 18b, and the space 18j is located on the opposite side of the space 18i with respect to the central wall 18b.

  The central wall 18b extends to the first bottom surface 18e and is in contact with the mounting surface 10e. The space 18j is surrounded by the center wall 18b on the LD12 side, that is, the front side. The space 18j is surrounded on both sides by a pair of side walls 18a, and is covered by a second bottom surface 18g on which the optical filter 30 is mounted. On the other hand, the space 18i is surrounded by a central wall 18b and a pair of side walls 18a.

  The LD 14 and the LD submount 24 are arranged in such a space 18i, and the PD 12, the submount 20 and the like are arranged in the space 18j. Therefore, the transmission unit and the reception unit can be separated from each other and electrically shielded.

6 is a cross-sectional view taken along line VI-VI shown in FIG. FIG. 6 shows the positional relationship between the PD 12, the LD 14, the WDM filter 16, and the block 18. The light emitted from the LD 14 follows a Gaussian distribution with respect to the optical axis Lz, and reaches about 20 to 25 ° with a half-width of the spread angle of 1 / e ² . Therefore, the size of the WDM filter 16 must be such that light having such a large divergence angle is efficiently separated (reflected / transmitted). For example, the WMD filter 16 needs to cope with light having a spread angle of ± 30 °. However, when the incident angle to the WDM filter 16 increases (when the incident angle deviates greatly from 45 °), the wavelength discrimination performance of the filter 16 deteriorates.

  FIG. 7 shows the incident angle dependence of the transmittance of a WDM filter designed to reflect light having a wavelength of 1.31 μm or less and transmit light having a wavelength longer than that. In FIG. 7, the horizontal axis indicates the wavelength of light, and the vertical axis indicates the transmittance of the WDM filter. In FIG. 7, the characteristic indicated by the thickest solid line, the characteristic indicated by the solid line thinner than this line, the characteristic indicated by the dotted line, the characteristic indicated by the alternate long and short dash line, and the characteristic indicated by the two-dot chain line are shown in FIG. It is a characteristic in the case of 75 degrees, 60 degrees, 45 degrees, 30 degrees, and 15 degrees. Note that the characteristics shown in FIG. 7 are characteristics for the s-wave (polarization direction perpendicular to the incident surface of the WDM filter) component of the emitted light from the LD.

  At an incident angle of 75 ° (offset by 30 ° from the center 45 °), even a filter designed to reflect almost all of the light having a wavelength of 1.31 μm (transmittance˜0) is 1.35 μm. A considerable transmittance is shown with respect to the wavelength. Here, since the incident angle of light is an angle from the normal line of the WDM filter 16, the incident angle of 75 ° corresponds to the upper limit of the spread angle shown in FIG. Such incident light becomes stray light and repeats multiple reflection and birefringence in the filter 16 to escape from the filter 16 or diffuse reflection in the cap, and part of the stray light enters the PD 12.

  In the optical module 1 of the present embodiment, in order to prevent the stray light from entering the PD 12, the transmitting unit and the receiving unit are separated with the central wall 18b interposed therebetween, and the receiving unit has a second bottom surface. The filter 30 is attached to 18 g to reduce the ratio of stray light directly incident on the PD 12. In the conventional configuration, the back surface of the WDM filter is open, and there is a high possibility that stray light will enter the PD. In the conventional optical module in which the LD and the PD are accommodated in a single package, it is difficult to provide a light blocking filter such as the filter 30 in the vicinity of the PD. By adopting the block 18 of this embodiment, a cut filter can be provided.

Next, a method for manufacturing an optical module by aligning the PD 12, the LD 14, and the WDM filter 16 will be described. FIG. 10 is a diagram illustrating a method of manufacturing an optical module. Here, the optical axis direction of the PD 12, that is, the direction orthogonal to the mounting surface 10 e is Z, and the optical axis direction of the LD 14 is Z _L.

  In this manufacturing method, first, as shown in FIG. 10A, the PD 12 and the LD 14 are arranged on the mounting surface 10e within the range of the mechanical accuracy of each handling jig. Usually, the positional accuracy of the PD 12 and LD 14 at this time is sufficiently secured to an accuracy of about 10 to 15 μm.

Then, as shown in (b) of FIG. 10, a block 18 equipped with a WDM filter 16, placed on the mounting surface 10e, by moving the block 18 in the axial _{Z L} direction, PD 12, LD 14 and,, WDM The filter 16 is aligned. When alignment is performed, as shown in FIG. 10B, an image acquisition device 32 such as a CCD camera is disposed at a position immediately above the PD 12, that is, on the optical axis Z of the PD 12.

  The image acquired by the image acquisition device 32 includes an image of the light receiving surface of the PD 12 acquired through the filter 30 and the filter 16 and an image of the LD 14 reflected by the filter 16.

  As shown in FIG. 10 (c), in the image acquired by the image acquisition device 32, the block 18 is moved so that the center of the light receiving unit 12a of the PD 12 and the center of the edge of the end surface of the LD 14 are aligned. Thus, alignment of the PD 12, the LD 14, and the WDM filter 16 is realized. Note that the end face of the active layer of the LD 14 is located at the center of the edge of the LD 14. Resin can be used for fixing the block 18 to the stem 10a after movement.

  Hereinafter, an optical module according to another embodiment will be described. FIG. 9 is a plan view of an optical module according to another embodiment. FIG. 9 shows the optical module 1A with the cap removed. In the optical module 1A shown in FIG. 9, the block 18A and the LD submount (mounting member) 24A are different from the corresponding parts of the optical module 1 in FIG. Hereinafter, the block 18A and the LD submount 24A will be described in detail.

  FIG. 10 is a perspective view of a block of an optical module according to another embodiment. The space 18h of the block 18A of the optical module 1A shown in FIG. 10 is not a through-hole, but its horizontal cross-sectional shape forms part of a triangle. In the present embodiment, the block 18A includes two surfaces 18k and 18m that define a space 18h. The surfaces 18k and 18m extend in the direction (axis Z direction) through which light of the first wavelength passes. Further, in this example, the surfaces 18k and 18m are configured such that the distance from each other becomes narrower as the distance from the LD 14 increases.

  In the optical module 1, the horizontal cross-sectional shape of the space 18h provided by the block 18 is circular. A hole having a circular cross-sectional shape is excellent in productivity because it can be processed only by a drill. However, according to the experience of the inventors, since light incident on the curved surface is reflected in all directions, a part of the reflected light may enter the PD 12. A block 18A is provided with this countermeasure. The space 18h of the block 18A is configured so that the shape of the horizontal cross section forms a part of a triangle by the surface 18k and the surface 18m, and thus the light reflected by the surface 18k and the surface 18m is directed in a specific direction. be able to. Therefore, the stray light to PD12 can further be reduced.

  Further, unlike the block 18, the block 18A does not have the central wall 18b. As a countermeasure, in the optical module 1A, as shown in FIG. 9, the width of the metal LD submount 24A is enlarged so that the LD submount 24A is in contact with the pair of side walls 18a. The LD submount 24A extends further than the LD 14 toward the PD 12 in the light emitting direction of the LD 14. The LD submount 24A defines a space in which the PD 12 is disposed together with the block 18A, and contributes to electrical isolation between the LD 14 and the PD 12.

  In the block 18A, the distance between the mounting surface 10e and the top of the side wall 18a is smaller than the distance between the mounting surface 10e and the slope 18f. That is, a space for exposing the inclined surface 18f is widened on the top of the side wall 18a. As a result, the light reflected by the surfaces 18k and 18m can escape to the outside of the block 18.

  As shown in FIG. 11, like the block 18B, the side wall 18a may extend to the same height as the slope 18f.

  Hereinafter, an optical module according to still another embodiment will be described. FIG. 12 is a perspective view of an optical module according to still another embodiment. In FIG. 12, the optical module 1C is shown with the cap removed. FIG. 13 shows a state where the block is removed from the optical module shown in FIG.

  In the optical module 1 </ b> C shown in FIGS. 12 and 13, the block 18 </ b> C and the LD submount 24 </ b> C are different from corresponding parts of the optical module 1. 14 and 15 are perspective views showing blocks of an optical module according to still another embodiment. FIG. 14 is a perspective view of the block as viewed from above, and FIG. 15 is a perspective view of the block as viewed from below. FIG. 16 is a perspective view showing the block broken along the line XVI-XVI in FIG.

  The block 18C shown in FIGS. 14 to 16 is different from the block 18 of the optical module 1 in that it does not have a pair of side walls. As a countermeasure against the removal of the pair of side walls from the block, as shown in FIGS. 12 and 13, the submount 24C is provided with a pair of side walls.

  That is, the submount 24C includes a central portion 24a for mounting the LD 14 and the wiring board 26, and a pair of side walls 24b located on both sides of the central portion 24a. The horizontal cross-sectional shape of the submount 24C is substantially C-shaped. The block 18C is disposed in a space defined by the pair of side walls 24b and the central portion 24a. The interval between the pair of side walls 24b is slightly larger than the width of the block 18C.

  As shown in FIGS. 14 to 16, the block 18C includes a front wall 18b corresponding to the central wall of the block 18, a rear portion extending from the top of the front wall 18b, and a longitudinal section of the support portion 18c having a triangular shape. Have. A WDM filter 16 is attached to the slope 18f provided by the support 18c, and an optical filter 30 is attached to the bottom 18g of the support 18c. The bottom surface 18g is located above the PD 12 to prevent stray light from entering the PD 12.

  The PD 12 is disposed in a space defined by the front wall 18b, the support portion 18c, and a pair of side walls of the submount 24C. In addition, since the bottom surface 18e of the front wall 18b directly contacts the mounting surface 10e of the stem 10a, electrical isolation between the PD 12 and the LD 14 is realized by the front wall 18b.

  A space 18h through which light having the first wavelength incident on the PD 12 passes is formed in the support portion 18c. Although the water-side cross-sectional shape of the space 18h is used, the cross-sectional shape may be triangular as in the previous example.

  FIG. 17 is a perspective view of an optical module according to still another embodiment. FIG. 18 is a perspective view of the block of the optical module shown in FIG. An optical module 1D shown in FIG. 17 is an optical module according to a modification based on the optical module 1C shown in FIG. In the optical module 1D shown in FIG. 17, the block 18D is different from the corresponding component of the optical module 1C.

  As shown in FIG. 18, the block 18D of the optical module 1D has a pair of flanges 18n on both sides of the support portion 18c. The flange 18n can be disposed on top of the pair of side walls 24b of the submount 24C. Therefore, when aligning the PD 12, LD 14, and WDM filter 16, the block 18D can be slid along the tops of the pair of side walls 24b of the submount 24C. Therefore, according to the block 18D, only the front wall 18b is in contact with the mounting surface 10e, and the center of gravity can be more stably aligned than the submount 24C in the support portion 18c. It is preferable that the height of the front wall 18b of the block 18D is slightly lower than the height of the side wall 24b of the submount 24C in order to slide the block 18D stably.

  FIG. 19 is a cross-sectional view of a main part of an optical module according to still another embodiment. FIG. 20 is a perspective view showing a block of the optical module shown in FIG. An optical module 1E shown in FIG. 19 is a modification based on the optical module 1C. In the optical module 1E, the block 18E is different from the corresponding components of the optical module 1C.

  As shown in FIG. 20, the block 18E does not have a front wall. However, the lower end of the WDM filter 16 is extended downward compared to any of the previous examples. Further, the slope 18f of the block 18E for mounting the WDM filter 16 extends downward as compared with the previous example. As shown in FIG. 6, the light emitted from the LD 14 has a significant divergence angle, but the lowest light in the range of the divergence angle is incident on the WDM filter at a small incident angle. The light emitted from the LD is reliably reflected at the corners. Therefore, it is unlikely that the LD emitted light on the side close to the lowest limit is reflected by the WDM filter 16 and becomes stray light.

  On the other hand, as a countermeasure against the removal of the front wall of the block 18E, in this example, the slope 18f of the block 18E is extended to the front side, that is, the LD side as compared with the previous example, thereby reducing the electrical crosstalk. I am trying. Note that the width of the block 18E is slightly smaller than the distance between the pair of side walls 24b of the submount 24C, and the side surface of the block 18E is adhered to the inner surface of the side wall 24b to fix the block 18E. This is the same as the embodiment.

  21 and 22 are perspective views showing further modifications of the block. A block 18F shown in FIG. 21 and a block 18G shown in FIG. 22 are further modified examples of the block 18E. In the block 18F shown in FIG. 21, the horizontal cross-sectional shape of the space 18h is a semicircle. In the block 18G shown in FIG. 22, the horizontal cross-sectional shape of the space 18h is a triangle.

  When the horizontal cross section of the space 18h is circular, the reflected light is dispersed. Therefore, the intensity of the reflected light becomes extremely small when focused in one direction. However, theoretically there is a finite reflected light that is not zero, and there is a possibility that this becomes stray light. A space 18h of the block 18F shown in FIG. 21 is a space formed by removing a part of the surface defining the through hole. A space 18h shown in FIG. 22 has a horizontal cross-sectional shape of a triangle, and the space 18h is defined by two surfaces and is a space opened to the LD 14 side. As shown in the blocks of FIG. 21 and FIG. 22, by making the space 18h open to the LD 14 side, it is possible to escape light that is irregularly reflected on the surface defining the space 18h. As a result, optical crosstalk is reduced. Can be improved.

It is a perspective view showing a bidirectional optical module according to an embodiment with a part broken away. FIG. 2 is a plan view showing the optical module shown in FIG. 1 with a cap removed. It is a perspective view which shows an example of a block. It is a perspective view which shows an example of a block. FIG. 4 is a perspective view illustrating a partially broken block illustrated in FIG. 3. It is sectional drawing along the VI-VI line shown in FIG. It is a graph which shows the incident angle dependence of the transmittance | permeability of the WDM filter designed to reflect the light of the wavelength of 1.31 micrometer or less, and permeate | transmit the light of the wavelength more. It is a figure which shows the method to manufacture an optical module. It is a top view of the optical module which concerns on another real child form. It is a perspective view of the block of the optical module which concerns on another embodiment. It is a perspective view of another example of the block of an optical module. It is a perspective view of the optical module which concerns on another embodiment. The state which removed the block from the optical module shown in FIG. 12 is shown. It is a perspective view which shows the block of the optical module which concerns on another embodiment. It is a perspective view which shows the block of the optical module which concerns on another embodiment. It is a perspective view which fractures | ruptures and shows a block along the XVI-XVI line of FIG. It is a perspective view of the optical module which concerns on another embodiment. It is a perspective view of the block of the optical module shown in FIG. It is sectional drawing of the principal part of the optical module which concerns on another embodiment. It is a perspective view which shows the block of the optical module shown in FIG. It is a perspective view which shows the further modification of a block. It is a perspective view which shows the further modification of a block.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A, 1C, 1D, 1E ... Optical module, 10 ... Package, 10a ... Stem, 10b ... Lead pin, 10c ... Cap, 10e ... Mounting surface, 12 ... Light receiving element (PD), 14 ... Light emitting element (LD), 16 ... WDM filter, 18, 18A, 18B, 18C, 18D, 18E, 18F, 18G ... block, 18a ... side wall, 18b ... central wall (front wall), 18c ... support part, 18d ... top surface, 18e ... first Bottom surface, 18f ... slope, 18g ... second bottom surface, 18h ... space, 18k, 18m ... surface, 18n ... flange, 20 ... submount (PD submount), 22 ... preamplifier, 24, 24A, 24C ... LD submount , 24a ... central part, 24b ... side wall, 26 ... wiring board, 30 ... optical filter, 32 ... image acquisition device.

Claims (8)

A filter that transmits light of a first wavelength emitted by one fiber and reflects light of a second wavelength different from the first wavelength;
A light receiving element that receives light of the first wavelength that has passed through the filter;
A light emitting element that emits light of the second wavelength toward the filter;
A block having a slope for mounting the filter, the slope being along a plane intersecting both the light emitting direction of the light emitting element and the light passing direction of the first wavelength;
A package containing the filter, the light receiving element, the light emitting element, and the block;
With
The block has a space through which the light of the first wavelength passes, and a cross section perpendicular to the passage direction of the light of the first wavelength in the space is a triangle.
Optical module. The block has two planes that define the space;
The two planes extend in the direction of passage of light of the first wavelength, and are provided so that the space between the two surfaces becomes narrower as the distance from the light emitting element increases. The optical module according to claim 1. The package has a mounting surface on which the light receiving element is mounted,
The block has a pair of side walls and a support portion positioned between the pair of side walls, and includes a first bottom surface in contact with the mounting surface,
The slope is provided by the support;
The support portion includes a second bottom surface spaced from the mounting surface between the mounting surface and the slope.
The second bottom surface and the pair of side walls define a space in which the light receiving element is disposed.
The optical module according to claim 1 or 2. A distance between the mounting surface and the top of the pair of side walls is smaller than a distance between the mounting surface and the slope;
The optical module according to claim 3. A mounting member for mounting the light emitting element;
The mounting member is made of metal, is placed between the pair of side walls, and defines the space in which the light receiving element is disposed.
The optical module according to claim 3 or 4.   The optical module according to claim 3, wherein an optical filter for blocking light of the second wavelength is provided on the second bottom surface.   The optical module according to claim 6, wherein an optical axis of the wavelength cut filter is parallel to an optical axis of the light receiving element. A method for manufacturing an optical module, comprising:
Arranging the light emitting element and the light receiving element at respective predetermined positions;
A step of moving a block on which a filter is mounted, wherein the filter is a filter for passing light of a first wavelength to the light receiving element and reflecting light of a second wavelength from the light emitting element. A step,
Including
In the step of moving the block, an image of the light receiving element and an image of the light emitting element acquired through reflection by the filter in an image observed by an image acquisition device arranged on the optical axis of the light receiving element are The block is moved so as to have a predetermined positional relationship.
Method.

Images