JP2018084778A - Optical module, optical transmission and reception device, and method for mounting optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce variation in characteristics among a plurality of channels in the case where an optical module is applied to a wavelength division multiplex optical transmission and reception module.SOLUTION: An optical module comprises a multichannel light emission part 104 provided with a plurality of light emission elements mounted thereon and having a plurality of channels, a multichannel polarization holding part 107 provided with a plurality of optical fibers mounted thereon and having a plurality of channels, an optical fiber holding substrate 101 for holding the multichannel polarization holding part 107, an optical isolator 110, and a multichannel diffraction grating type optical coupler 116. An optical fiber of the multichannel polarization holding part 107 is held on the optical fiber holding substrate 101 in the state of being twisted so that a polarization plane between both ends of the optical fiber rotates by a polarization rotation angle in the optical isolator 110.SELECTED DRAWING: Figure 1B

Description

  The present invention relates to an optical module, an optical transceiver, and an optical module mounting method.

  In recent years, silicon photonics technology has attracted attention. Silicon photonics technology is a general term for technologies for producing optical circuits using silicon wafer process technology and packaging technology that have been highly developed for LSI manufacturing. An optical module manufactured using silicon photonics technology enables large capacity, low cost, power saving, and long-distance transmission.

  The optical module generally uses an external modulation system in which an optical signal having a constant intensity emitted from a light emitting element is modulated at high speed by an optical modulator. In the external modulation system, a technique for coupling light from a light emitting element to an optical modulator with high efficiency is important.

  The optical module may use a wavelength division multiplexing system (WDM system) that combines and transmits light of a plurality of wavelengths. In the WDM system, it is necessary to couple light from a light emitting element having a large number of channels to optical modulators of different channels. For this reason, it is necessary to combine the respective channels so as to increase the efficiency and reduce the variation between the channels.

  As technologies related to the optical module, for example, there are US8, 168, 939 B2 (Patent Document 1), JP-A-2006-71025 (Patent Document 2), and JP-A-2006-292562 (Patent Document 3). . Patent Document 1 discloses a structure in which light emitted from a single-channel semiconductor laser is coupled to a silicon photonics chip in which an optical modulator is integrated using a half-wave plate. Patent Document 2 discloses a structure using a polarization maintaining fiber as optical coupling in an optical modulator composed of a plurality of channels. Patent Document 3 discloses a technique for rotating a polarization direction of a beam emitted from a light source of a single channel by 90 degrees by twisting a polarization maintaining optical fiber.

US8, 168, 939B2 Japanese Patent Laid-Open No. 2006-71025 JP 2006-292562 A

  In an optical module composed of a large number of channels, even if the total loss in each channel is the same, the power consumption tends to be lower when the variation in loss in each channel is smaller. This is due to the fact that the electro-optic energy conversion efficiency of the light emitting element is generally non-linear. When the input electric energy is large, the efficiency tends to deteriorate due to the influence of heat generation. Therefore, even if the total loss in the entire optical module is the same, if some channels include channels with extremely large losses compared to others, the power consumption in those channels becomes extremely large. As a result, the total power consumption may increase. Furthermore, when there is a large variation between channels, a correction circuit that takes the variation into consideration is necessary in advance, and power consumption in the correction circuit increases.

  Patent Documents 1 to 3 do not mention reducing variation in characteristics such as optical loss among many channels when applied to a wavelength division multiplexing optical transceiver module.

  An object of the present invention is to reduce variation in characteristics among a large number of channels when applied to a wavelength division multiplexing optical transceiver module.

  An optical module according to an aspect of the present invention includes a multi-channel light-emitting unit having a plurality of light-emitting elements and a plurality of channels, and a multi-channel polarization holding unit having a plurality of channels and a plurality of optical fibers mounted thereon. An optical fiber holding substrate for holding the multi-channel polarization holding unit, an optical isolator, and a multi-channel diffraction grating type optical coupler, and each light emitting element of the multi-channel light emitting unit, One end of each optical fiber of the multichannel polarization holding unit is optically connected, and each optical fiber and the other end of the multichannel polarization holding unit and the multichannel diffraction grating type optical coupler are optically connected. The optical isolator is disposed on an optical path connected to the multichannel polarization holding unit and the multichannel diffraction grating type optical coupler, and the multichannel polarization holding unit In a state in which the polarization plane across the optical fiber by polarization rotation angle component of the optical isolator is twisted so as to rotate, characterized in that it is held in the optical fiber holding substrate.

  An optical transceiver according to one embodiment of the present invention includes a multi-channel light-emitting portion having a plurality of light-emitting elements and a plurality of channels, and a multi-channel polarization having a plurality of optical fibers and a plurality of channels. Each of the light emitting elements of the multichannel light emitting section includes a holding section, an optical fiber holding substrate for holding the multichannel polarization holding section, an optical isolator, and a multichannel diffraction grating type optical coupler. And one end of each optical fiber of the multi-channel polarization holding unit is optically connected, each optical fiber and the other end of the multi-channel polarization holding unit, and the multi-channel diffraction grating type optical coupler The optical isolator is optically connected, and the optical isolator is disposed on an optical path connecting the multi-channel polarization holding unit and the multi-channel diffraction grating type optical coupler, and the multi-channel polarization holding unit An optical module configured to be held on the optical fiber holding substrate in a state where the polarization plane between both ends of the optical fiber is rotated by the polarization rotation angle of the optical isolator, An optical circuit board on which at least the diffraction grating type optical coupler is formed, the optical circuit board having an optical modulator for converting a modulated electric signal into an optical signal, and modulated light A light receiver for converting a signal into an electrical signal, a modulator drive circuit for driving the light modulator, a light receiver drive circuit for driving the light receiver, and light of a plurality of wavelengths are combined. And a wavelength multiplexer / demultiplexer for wave transmission, wherein the plurality of wavelengths are multiplexed and transmitted / received.

  The optical module mounting method according to one aspect of the present invention includes a multi-channel light emitting unit having a plurality of light-emitting elements and a plurality of channels, and a multi-channel having a plurality of optical fibers and a plurality of channels. A polarization holding unit; an optical fiber holding substrate for holding the multi-channel polarization holding unit; an optical isolator; and a multi-channel diffraction grating type optical coupler; A light emitting element and one end of each optical fiber of the multi-channel polarization holding unit are optically connected, each optical fiber and the other end of the multi-channel polarization holding unit, and the multi-channel diffraction grating type optical coupler Are connected optically, and the optical isolator is disposed on an optical path connecting the multi-channel polarization holding unit and the multi-channel diffraction grating type optical coupler, and the multi-channel The polarization holding unit is configured to be held on the optical fiber holding substrate in a state in which a polarization plane between both ends of the optical fiber is rotated by an amount corresponding to a polarization rotation angle in the optical isolator. An optical module mounting method, wherein a positional relationship between an alignment marker for mounting the multi-channel light emitting unit formed on the surface of the optical fiber holding substrate and the multi-channel light emitting unit is based on image information. A first active alignment that adjusts the positional relationship between the optical fiber holding substrate and the optical circuit substrate while monitoring the light coupling efficiency by actually driving the multi-channel light emitting unit. And a process.

  According to the present invention, when applied to a wavelength division multiplexing optical transceiver module, it is possible to reduce variation in characteristics among a large number of channels.

It is a principal part perspective view of the optical module which concerns on Embodiment 1 of this invention. It is a cross-sectional view of a ₁ -a ₁ 'of the optical module shown in FIG. 1A. It is a sectional view of b ₁ -b ₁ 'of the optical module shown in FIG. 1A. It is a cross-sectional view of a c ₁ -c ₁ 'of the optical module shown in FIG. 1A. It is explanatory drawing of the mounting method of the polarization maintaining optical fiber in the optical module which concerns on Embodiment 1 of this invention. It is explanatory drawing of the refractive index distribution of the refractive index distribution type | mold lens in the optical module which concerns on Embodiment 1 of this invention. It is a perspective view of the example of mounting of the polarization maintaining optical fiber and the gradient index lens in the optical module according to Embodiment 1 of the present invention. It is explanatory drawing of the beam shape of the light which permeate | transmits the polarization maintaining optical fiber and refractive index distribution type | mold lens in the optical module which concerns on Embodiment 1 of this invention. It is explanatory drawing of the optical isolator in the optical module which concerns on Embodiment 1 of this invention. 1 is a perspective view of a diffraction grating type optical coupler in an optical module according to Embodiment 1 of the present invention. It is a perspective view of the modification of the example of mounting of the polarization maintaining optical fiber and refractive index distribution type lens in the optical module which concerns on Embodiment 1 of this invention. It is explanatory drawing of the beam shape of the light which permeate | transmits the polarization maintaining optical fiber and refractive index distribution type | mold lens in the optical module which concerns on Embodiment 1 of this invention. It is explanatory drawing of the modification of the optical isolator in the optical module which concerns on Embodiment 1 of this invention. It is another example of a cross-sectional view of a c ₁ -c ₁ 'of the optical module shown in FIG. 1A. It is a principal part perspective view of the optical module which concerns on Embodiment 2 of this invention. It is a cross-sectional view of _{a 2} -a 2 'section of the optical module shown in Figure 9A. It is a principal part perspective view of the optical module which concerns on Embodiment 3 of this invention. It is a cross-sectional view of _{a 3} -a 3 'portion of the optical module shown in FIG. 10A. It is a principal part perspective view of the optical module which concerns on Embodiment 4 of this invention. It is a cross-sectional view of _{a 4} -a 4 'portion of the optical module shown in FIG. 11A. It is a principal part top view of the wavelength division multiplexing optical transmission and reception module concerning Embodiment 5 of the present invention. It is principal part sectional drawing of the silicon photonics optical module as related technology.

  First, in order to clarify the characteristics of the embodiment of the present invention, a technique related to the embodiment of the present invention will be described with reference to FIG.

  Referring to FIG. 13, a laser module 7 in which the light emitting element 1, the ball lens 2, the optical isolator 3, and the reflection mirror 4 are mounted on the front surface side of the holding substrate 5, and the half-wave plate 6 is mounted on the back surface side is silicon photonics. It is mounted on the surface of the chip 8. Note that this structure shown in FIG. 13 is a mounting method of the single-channel light-emitting element 1.

The outgoing light 12 from the light emitting element 1 is input to the surface of the silicon photonics chip 8 through the ball lens 2, the optical isolator 3, the reflection mirror 4, and the half-wave plate 6. The silicon photonics chip 8 includes a silicon substrate 9 and a SiO ₂ layer 10 formed on the upper surface of the silicon substrate 9, and an optical circuit (not shown) including an optical waveguide, light modulation, a light receiver and the like is embedded in the SiO ₂ layer 10. ing. A diffraction grating type optical coupler 11 for converting the optical axis direction of light input from the surface is formed at the input part of the optical circuit, and light is input through the diffraction grating type optical coupler 11. The Here, the ball lens 2 is for condensing light, and the optical isolator 3 is for the reflected light from the surface of the silicon photonics chip 8 to return to the light emitting element 1 and for the operation of the light emitting element 1 to become unstable. It is for suppressing.

  The reflection mirror 4 converts the optical axis direction, and the half-wave plate 6 is for rotating the polarization direction. Here, the reason why the half-wave plate 6 is necessary is that it is necessary to restore the rotation of the polarization generated in the optical isolator 3. Since the diffraction grating type optical coupler 11 has a very large polarization dependence in principle, the polarization direction is appropriately controlled in order to couple the light from the light emitting element 1 to the diffraction grating type optical coupler 11 with low loss. This is because it is necessary to input after that.

  Here, the present inventors considered that the structure of FIG. 13 is applied to a mounting method of a multi-channel light emitting device in which a plurality of light emitting devices having different wavelengths are integrated, and half-wavelength as in the related art. It has been found that there is a big problem when using the plate 6.

  The half-wave plate 6 is an optical component that can rotate incident linearly polarized light by providing a phase difference between two orthogonal polarization components using a birefringent material or the like. When the thickness is exactly half the wavelength, the incident linearly polarized light is emitted directly as polarized light, but when the thickness deviates from half the wavelength, it is emitted as elliptically polarized light. . In other words, when light of various wavelengths is incident on the half-wave plate 6 having a certain thickness, a specific wavelength is emitted as linearly polarized light, but light of other wavelengths is emitted as elliptically polarized light. Therefore, when trying to input light of various wavelengths through the half-wave plate 6 to the diffraction grating type optical coupler 11 whose optical coupling loss is strongly dependent on polarization, the optical loss varies between wavelengths. I found it.

  What is important here is that the above problem becomes more prominent as the demand for capacity increases in the future. The optical module that supports 100 Gigabit Ethernet (registered trademark) (100 GbE) is a system that multiplexes light modulated at 25 Gbps with four wavelengths. In contrast, the next-generation 400 Gigabit Ethernet (registered trademark) (400 GbE) compatible optical module multiplexes light modulated at 50 Gbps into eight wavelengths.

  When the number of wavelengths to be multiplexed is doubled, there is a concern that the wavelength range is widened and the variation in optical loss becomes more remarkable. In addition, even when the wavelength to multiplex is increased, the method which does not change a wavelength range by narrowing the space | interval of each wavelength is also considered. However, the narrower the wavelength interval, the stricter the specifications required for the optical component and the higher the cost. Therefore, it is not realistic considering the economy. When such a structure is applied to a wavelength division multiplexing optical transceiver module, there is a variation between channels regarding the optical loss between the light emitting element and the optical modulator.

  Therefore, in the embodiment of the present invention, when applied to a wavelength division multiplexing optical transceiver module, variation in characteristics among a large number of channels is reduced. Therefore, in the embodiment of the present invention, a multi-channel light emitting unit having a plurality of light-emitting elements mounted thereon and a plurality of channels, a multi-channel polarization holding unit having a plurality of optical fibers mounted thereon and a plurality of channels, and In an optical module having an optical fiber holding substrate for holding a multi-channel polarization holding unit, an optical isolator, and a multi-channel diffraction grating type optical coupler, the multi-channel polarization holding optical fiber is an optical isolator. It is characterized by twisting so that the polarization plane between both ends of the optical fiber is rotated by the polarization rotation angle of. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1

The configuration of the first embodiment will be described with reference to FIGS. 1A to 5. 1A is a perspective view of a main part of an optical module described in Embodiment 1. FIG. FIG. 1B is a cross-sectional view taken along a ₁ -a ₁ ′ in FIG. 1A. In the optical module shown in FIGS. 1A and 1B, a multi-channel laser module 112 is stacked and mounted on the surface of a silicon photonics chip 113. Here, the multi-channel laser module 112 includes a multi-channel light emitting element 104 on the upper surface of the laser / optical fiber mounting portion 102 of the laser module substrate 101, an input-side gradient index lens 105 on the input-side output side, and an output-side side. A module in which a polarization maintaining optical fiber 107 having a gradient index lens 106 is mounted, and an optical isolator 110 and a reflection mirror 111 are mounted on the upper surface of the optical isolator / reflection mirror mounting portion 103 of the laser module substrate 101. It is. Here, the multi-channel light emitting element 104 constitutes a multi-channel light emitting unit having a plurality of channels by mounting a plurality of light emitting elements having different wavelengths. Also, the polarization maintaining optical fiber 107 constitutes a multi-channel polarization maintaining unit having a plurality of channels on which a plurality of optical fibers are mounted.

More preferably, the laser / optical fiber mounting portion 102 of the laser module substrate 101 is thicker than the optical isolator / reflecting mirror mounting portion 103. On the other hand, the silicon photonics chip 113 is composed of a silicon substrate 114 and a SiO ₂ layer 115 formed on the upper surface thereof. In the SiO ₂ layer 115, an optical circuit (not shown) composed of an optical waveguide, light modulation, a light receiver, and the like. ) Is an embedded optical integrated circuit chip. Further, a diffraction grating type optical coupler 116 for converting the optical axis direction of light input from the surface is formed at the input portion of the optical circuit, and light is input through the diffraction grating type optical coupler 116. Is done. In the figure, an optical circuit composed of an optical waveguide, light modulation, light receiver, and the like is not shown because it overlaps with the SiO ₂ layer 115 and cannot be identified. In FIG. 1, the case where the number of channels of the multi-channel light emitting element 104 and the polarization maintaining optical fiber 107 is four is shown as an example. However, the number of channels is not limited to this. Good.

Next, details of each optical component described above will be described. First, the polarization maintaining optical fiber 107 will be described in detail with reference to FIG. 1C, FIG. 1D, and FIG. FIG. 1C and FIG. 1D are examples of views in which the cross sections of the b ₁ -b ₁ ′ portion and c ₁ -c ₁ ′ portion in FIG. 1A are viewed from the multi-channel light emitting element 104 side (right side of the drawing). The cross section of the b ₁ -b ₁ ′ portion is a surface including the surface where the input-side gradient index lens 105 and the polarization maintaining optical fiber 107 are in contact, and the cross section of the c ₁ -c ₁ ′ portion. It is a surface including a surface where the output-side gradient index lens 106 and the polarization maintaining optical fiber 107 are in contact with each other.

In the cross section of the b ₁ -b ₁ ′ portion, the input-side gradient index lens 105 of each channel is mounted so as to fit into the optical fiber mounting V-groove 109 formed on the surface of the laser module substrate 101. . Similarly, in the cross section of the c ₁ -c ₁ ′ portion, the output-side gradient index lens 106 of each channel is mounted so as to be fitted into the optical fiber mounting V-shaped groove 109. The difference regarding the mounting form in the b ₁ -b ₁ ′ part and the c ₁ -c ₁ ′ part is the direction of the axis of the polarization maintaining optical fiber 107. In addition to the core portion 107a and the clad portion 107b, the polarization maintaining optical fiber 107 is provided with a stress applying portion 107c in which an impurity such as boron is added to a part of the clad portion. Since the non-axisymmetric stress is applied to the core portion 107a, the polarization plane can be maintained without being affected by external stress such as bending of the optical fiber.

  In the polarization maintaining optical fiber 107, a high speed axis 160 and a low speed axis 161 are defined, and input light having a polarization plane substantially coinciding with the axes can propagate through the optical fiber while maintaining linear polarization. Here, having substantially the same polarization plane means that the angle formed between the polarization plane of the multi-channel light emitting element 104 and the high-speed axis 160 or the low-speed axis 161 of the multi-channel polarization maintaining optical fiber 107 is within ± 5 degrees. To do. By setting the angle formed by the high-speed axis 160 or the low-speed axis 161 of the multi-channel polarization maintaining optical fiber 107 to be within ± 5 degrees, it is possible to effectively reduce the optical loss.

In the configuration of the first embodiment, in the cross section of the b ₁ -b ₁ ′ section, the high-speed axis 160 or the low-speed axis 161 of the polarization-maintaining optical fiber 107 indicates the polarization direction of the outgoing light 150 from the multichannel light emitting element 104. It is almost coincident. The polarization direction of the outgoing light 150 from the multi-channel light emitting element 104 is polarized light in which the electric field component called TE mode vibrates in the in-plane direction of the light emitting element, or the electric field component called TM mode is perpendicular to the surface of the light emitting element. It is common for either polarized light to vibrate in the direction. For this reason, as shown in FIG. 1C, the high-speed axis 160 may substantially coincide with the surface direction of the laser module substrate 101, or the high-speed axis 160 may substantially coincide with the surface vertical direction of the laser module substrate 101.

On the other hand, in the cross section of the c ₁ -c ₁ ′ portion, the direction of the axis of the polarization maintaining optical fiber 107 is rotated by a certain angle from the direction in the cross section of the b ₁ -b ₁ ′ portion. Although details will be described later, the rotation angle only needs to be rotated so as to cancel the polarization rotation when passing through the optical isolator 110. That is, when the polarization direction rotates 45 degrees counterclockwise when passing through the optical isolator 110, it only needs to be rotated 45 degrees clockwise. FIG. 2 is a perspective view of the polarization maintaining optical fiber 107 in which the polarization direction 181 at the output end face 107e rotates 45 degrees clockwise with respect to the polarization direction 180 at the input end face 107d. In order to rotate the polarization direction, the polarization maintaining optical fiber may be twisted as shown in the figure.

  Here, if the twist angle per unit length of the polarization maintaining optical fiber is too large, the stress applied from the outside to the core portion 107a cannot be ignored with respect to the stress applied in advance by the stress applying portion. There is a concern that the waves will not be held. For this reason, the length of the polarization-maintaining optical fiber 107 may be appropriately set according to the desired rotation angle at the output portion end face so that the external stress due to twisting becomes sufficiently small. The details of the polarization maintaining optical fiber 107 in the configuration of the first embodiment have been described above. For the sake of explanation, a PANDA (Polarization-maintaining AND Absorption-Reducing) fiber is shown as an example of the polarization-maintaining optical fiber 107 in the figure. However, the present invention is not limited to this, but a bow-tie fiber. Alternatively, an elliptical jacket fiber may be used.

  Next, the gradient index lenses 105 and 106 will be described in detail with reference to FIGS. 3A to 3C. The gradient index lenses 105 and 106 are cylindrical glass, and the in-plane refractive index distribution gently changes in a parabolic shape from the central axis toward the outer periphery as shown in FIG. 3A. Conventional convex lenses use refraction on the lens surface and require precise surface processing, whereas gradient index lenses use refraction inside the lens and require precise surface treatment. No processing is required.

  In addition, the gradient index lenses 105 and 106 can change the focal length of the lens arbitrarily by simply changing the length of the cylinder, and can be focused on the lens end face if an appropriate length is selected. is there. Therefore, it is also possible to connect the lens directly to the end face of a component such as an optical fiber.

  3A and 3C show an example of a perspective view when the gradient index lenses 105 and 106 are connected to both ends of the polarization maintaining optical fiber 107, respectively, and an example of a light beam transmitted through these components. . An input-side gradient index lens 105 is mounted on the input side of the polarization maintaining optical fiber 107, and an output-side gradient index lens 106 is mounted on the output side. Here, the input-side gradient index lens 105 has a function of condensing the light emitted from the light emitting point 190 and inputting it to the polarization maintaining optical fiber 107, and the output-side gradient index lens 106 is polarized. It has a function of condensing the light output from the wave holding optical fiber 107 at a condensing point 191.

1A and 1B, the light emission point 190 is the output end face of the multi-channel light emitting element 104, and the light condensing point 191 is the input end face of the diffraction grating type optical coupler 116. Here, the numerical aperture NA (Numerical Aperture) of the input-side gradient index lens 105 and the output-side gradient index lens 106 is preferably about the same as the NA of the polarization maintaining optical fiber 107. Further, it is preferable to design the distance L ₁ from the light emitting point 190 to the end face of the input-side gradient index lens 105 as short as possible. The shorter the distance L _{1, the} larger the maximum incident angle θ of the light component coupled to the polarization maintaining optical fiber 107, so that more light can be collected by the lens and coupled to the polarization maintaining optical fiber 107. Because.

On the other hand, it is preferable that the distance L ₂ from the end face of the output-side gradient index lens 106 to the condensing point 191 is designed to be sufficiently longer than L ₁ . This is because the optical isolator 110 needs to be disposed between the end surface of the output-side gradient index lens 106 and the condensing point 191. The distance L ₂ to be sufficiently longer than the distance L ₁ is, 3B, them shorter than that of the input-side gradient index lens 105 the length of the output-side refractive index distribution type lens 106 as shown in FIG. 3C That's fine. The details of the gradient index lenses 105 and 106 in the configuration of the first embodiment have been described above.

  Next, the optical isolator 110 will be described in detail with reference to FIG. An optical isolator is an optical component that utilizes the magneto-optic effect (Faraday effect) in which the polarization state of light is rotated by a magnetic field, and transmits light in the forward direction but does not transmit light in the reverse direction. It is used to protect the light emitting element from the instability of light and the return light that causes damage. FIG. 4 is an example of a perspective view of a polarization-dependent one-stage optical isolator 110A.

  The one-stage optical isolator 110A has a structure in which a Faraday rotator 110Ac is inserted between two polarizers 110Aa and 110Ab whose transmission axes are inclined by 45 degrees. The Faraday rotator is an optical component having a function of rotating the polarization plane of linearly polarized light. When a magnetic field is applied, the Faraday rotator has a property (nonreciprocity) that the polarization plane rotates in the opposite direction depending on the light input direction. The light input from the side of the polarizer 110Aa can be transmitted by the Faraday rotator 110Ac through the polarizer 110Ab whose plane of polarization is rotated 45 degrees counterclockwise with respect to the optical axis direction and inclined 45 degrees. On the other hand, the light input from the polarizer 110Ab side does not receive a large loss because the plane of polarization rotates 45 degrees clockwise with respect to the optical axis direction and is orthogonal to the transmission axis of the polarizer 110Aa. Thus, the optical isolator 110A has a function of transmitting only light from one direction, and the polarization direction 182 at the input end face and the polarization direction 183 at the output end face rotate 45 degrees. Yes. The details of the optical isolator 110 in the configuration of the first embodiment have been described above.

  Next, the diffraction grating type optical coupler 116 will be described in detail with reference to FIG. FIG. 5 is an example of a perspective view of the diffraction grating type optical coupler 116. The diffraction grating type optical coupler 116 includes a silicon substrate 114, a lower cladding layer 115a formed on the upper surface of the silicon substrate 114, a diffraction grating portion 116a formed on the upper surface of the lower cladding layer 115a, a tapered portion 116b, an optical waveguide. 117 and an upper clad layer 115b formed on the upper surface of the lower clad layer 115a so as to cover the three. Here, one end of the diffraction grating portion 116a and the tapered portion 116b are connected, and the other end of the tapered portion 116b is connected to the optical waveguide 117.

The diffraction grating portion 116a, the tapered portion 116b, and the optical waveguide 117 may be made of the same silicon material as the substrate, and the lower cladding layer 115a and the upper cladding layer 115b may be made of SiO ₂ material. The diffraction grating part 116a has a function of converting the optical axis of the light 150d input from a substantially vertical direction with respect to the plane of the silicon substrate 114 and outputting the light to the taper part 116b using the second-order diffraction phenomenon of light. Further, the tapered portion 116b reduces the mode field diameter of the input light and outputs the input light 151 to the optical circuit. The diffraction grating part 116a exhibits a strong polarization dependence on the transmittance when the input light is output to the taper part 116b. When the polarized wave 184 in the x direction corresponding to the depth in the figure is input, the transmittance is maximized. The transmittance of the diffraction grating portion 116a strongly depends on the wavelength in addition to the polarization direction.

  By changing the pitch of the diffraction grating, the wavelength of the light having the maximum transmittance can be changed. Therefore, an optimum pitch may be designed according to the wavelength of the input light. Further, by changing the pitch, it is possible to change the input direction of light that maximizes the transmittance. There is a possibility that light input from a completely perpendicular direction to the substrate surface returns slightly to the light emitting element due to reflection on the substrate surface. For this reason, it is more preferable to incline about 4 to 12 degrees from the vertical direction of the substrate surface. The details of the diffraction grating optical coupler 116 in the configuration of the first embodiment have been described above.

  Next, an example of the mounting method of the optical module of Embodiment 1 is demonstrated. First, the gradient index lenses 105 and 106 are bonded to both ends of the polarization maintaining optical fiber 170. As the bonding method, an adhesive may be used, or direct fusion may be used. At this time, as shown in FIG. 3B, bonding is performed so that the central axes of the respective components substantially coincide.

  Next, the polarization maintaining optical fiber 170 to which the gradient index lenses 105 and 106 are bonded is mounted so as to fit into the optical fiber mounting V-shaped groove 109 of the laser module substrate 101. At this time, the position of the polarization maintaining optical fiber 170 in the optical axis vertical direction in the substrate surface is uniquely determined by the position of the optical fiber mounting V-groove 109, and the position in the substrate surface vertical direction is for optical fiber mounting. It is uniquely determined by the groove depth of the V groove 109.

  The position of the polarization maintaining optical fiber 170 in the optical axis direction may be positioned by matching with the optical fiber mounting marker provided on the surface of the laser module substrate 101. However, as shown in FIG. 1B, it is more preferable that the optical fiber mounting V-shaped groove 109 and the input-side gradient index lens 105 be mounted so that the side surfaces are in contact with each other. In mounting the polarization-maintaining optical fiber 170, it is important to mount the polarization-maintaining optical fiber 170 in accordance with the above-described direction.

  The axial direction may be adjusted while monitoring the camera with the shape of the stress applying portion 107c as a mark, and the light is actually transmitted using a polarizer, an optical fiber, a laser, an optical power meter, etc. You may adjust while monitoring. After mounting the polarization maintaining optical fiber 170 in a desired position and axial direction in this way, the multi-channel light emitting element 104 is mounted in accordance with the position of the laser mounting marker 108 formed on the surface of the laser module substrate 101. More preferably, the multi-channel light emitting device 104 is mounted so that the surface on which the active layer 104 a is formed faces downward and is in contact with the laser module substrate 101.

  After mounting the multi-channel light emitting element 104, the multi-channel laser module 112 is completed by mounting the optical isolator 110 and the reflection mirror 111 at desired positions on the surface of the laser module substrate 101. Finally, the multichannel laser module 112 is mounted on the upper surface of the silicon photonics chip 113. At this time, positioning may be performed by matching with a multi-channel laser module mounting marker provided on the surface of the silicon photonics chip 113. However, it is more preferable that the multi-channel light emitting element 104 is actually driven and positioned while monitoring the optical coupling loss with the silicon photonics chip 113.

  As described above, in the optical module according to the first embodiment, the polarization maintaining optical fiber 170 is twisted, and the axial direction at the output end face 107d is in the axial direction at the input end face 107e. The rotation is performed to cancel the polarization rotation when passing through the optical isolator 110. Therefore, the polarization direction after passing through the optical isolator 110 is substantially the same as the polarization direction of the diffraction grating type optical coupler 116, and a half-wave plate (for example, in FIG. 13) for rotating the polarization direction separately. The half-wave plate 6) is not necessary. Since the half-wave plate has a large wavelength dependency, when a multi-channel light emitting device having a different wavelength is mounted, the optical coupling loss varies greatly between channels. On the other hand, in the configuration of the first embodiment, it is possible to mount the variation between channels small.

  In the optical module according to Embodiment 1, the multi-channel light emitting element 104 is mounted on the laser module substrate 101 with a so-called junction-down structure with the surface on which the active layer 104a is formed facing downward. In the junction-up structure with the active layer 104a facing upward, variation in optical coupling loss between channels is large due to thickness variation when the light emitting element substrate is thinned by polishing or the like. On the other hand, the configuration of the first embodiment can be mounted with small variations between channels.

  In the optical module according to the first embodiment, gradient index lenses 105 and 106 are used to collect light from the multi-channel light emitting element 104. In conventional ball lenses and biconvex lenses, it is difficult to obtain a large NA because high precision and fine surface processing is required. On the other hand, the gradient index lenses 105 and 106 have a simple structure and can obtain a relatively large NA, so that they can be mounted at low cost and with low optical coupling loss.

  Next, as a modification of the optical module according to Embodiment 1, another embodiment of the input-side gradient index lens 105 described with reference to FIGS. 3B and 3C will be described. FIGS. 6A and 6B show an example of a perspective view when a gradient index lens is connected to both ends of the polarization maintaining optical fiber 107, and an example of light rays transmitted through these components. In this embodiment, two refractive index distribution type lenses are mounted on the input side end face of the polarization maintaining optical fiber 107. Here, it is preferable that the NA of the first input-side gradient index lens 105 a in contact with the polarization maintaining optical fiber 107 is approximately the same as the NA of the polarization maintaining optical fiber 107. The NA of the second input-side gradient index lens 105b in contact with the first input-side gradient index lens 105a is preferably larger than the NA of the first input-side gradient index lens 105a.

By increasing the NA of the lens on the light emitting point 190 side, the distance L ₁ ′ from the light emitting point 190 to the end face of the gradient index lens can be made shorter than in the case of FIG. 3C. As the distance L ₁ ′ is shorter, the maximum incident angle θ ′ of the light component coupled to the polarization maintaining optical fiber 107 becomes larger, and more light is collected by the lens than in the case of FIG. Can be coupled to fiber 107. The ability to couple more light means that the multi-channel light emitting device 104 can be implemented with lower optical coupling loss. However, in another embodiment, if the NA of the second input-side gradient index lens 105b is too large, the mounting tolerance of the multi-channel light emitting element 104 may become extremely small, thereby increasing the variation between channels. There is. Therefore, in consideration of the trade-off relationship between the optical coupling loss and the variation, the lens may be designed so that both are in an appropriate amount.

  Next, another embodiment of the one-stage optical isolator 110A described in FIG. 4 will be described as another modification of the optical module according to the first embodiment. FIG. 7 is an example of a perspective view of a polarization-dependent 1.5-stage optical isolator 110B. The 1.5-stage optical isolator 110B has a structure in which two Faraday rotators 110Bd and 110Be are inserted between three polarizers 110Ba, 110Bb, and 110Bc whose transmission axes are inclined by 45 degrees. The light input from the polarizer 110Ba side is transmitted by a Faraday rotator 110Bd whose polarization plane is rotated 45 degrees counterclockwise with respect to the optical axis direction and transmitted through the polarizer 110Bb inclined 45 degrees. Further, the polarization plane of the Faraday rotator 110Be rotates 45 degrees counterclockwise with respect to the optical axis direction, and can pass through the polarizer 110Bc tilted 45 degrees.

  On the other hand, the light input from the side of the polarizer 110Bc receives a large loss because the Faraday rotator 110Be rotates the plane of polarization by 45 degrees clockwise with respect to the optical axis direction and is orthogonal to the transmission axis of the polarizer 110Bb. do not do. Even if the polarizer 110Bb is slightly transmitted due to a manufacturing error or the like, the Faraday rotator 110Bd further rotates the polarization plane by 45 degrees clockwise with respect to the optical axis direction, and is orthogonal to the transmission axis of the polarizer 110Ba. The light is surely not transmitted due to further loss.

As described above, the 1.5-stage optical isolator has a higher light isolation function than the single-stage optical isolator, and reliably protects the light-emitting element from return light that causes instability and damage to the light-emitting element. be able to. As a result, a higher performance optical module can be realized. In the 1.5-stage optical isolator 110B, the polarization direction 185 at the input end face and the polarization direction 186 at the output end face are rotated by 90 degrees. As described above, in the mounting method of the polarization-maintaining optical fiber 107, the direction of the axis on the output side is rotated to cancel the polarization rotation when passing through the optical isolator 110 with respect to the direction on the input side. Just do it. For this reason, when the 1.5-stage optical isolator 110B is used, the cross section of the c ₁ -c ₁ ′ portion in FIG. 1A only needs to have the structure shown in FIG.

Embodiment 2

Next, the configuration of the second embodiment will be described with reference to FIGS. 9A and 9B. FIG. 9A is a perspective view of a main part of the optical module described in the second embodiment. FIG. 9B is a cross-sectional view of the part a ₂ -a ₂ ′ in FIG. 9A. In the optical module shown in FIGS. 9A and 9B, a multi-channel laser module 212 is stacked and mounted on the surface of the silicon photonics chip 113. In the configuration of the second embodiment, the configuration of the multi-channel laser module, more specifically, the mounting mode of the multi-channel light emitting element 104 is different. In the configuration of the first embodiment, the multi-channel light emitting element 104 is mounted on the upper surface of the laser / optical fiber mounting portion 102 of the laser module substrate 101. On the other hand, in the configuration of the second embodiment, the multi-channel light emitting element 104 is mounted on the upper surface of the light emitting element mounting substrate 204 which is a substrate different from the laser module substrate 201, and the laser module substrate 201 and the light emitting element mounting substrate 204 are mounted. Are connected with the same optical axis. Since other configurations are substantially the same as those of the first embodiment, description thereof is omitted.

  Next, an example of an optical module mounting method according to the second embodiment will be described. In the optical module mounting method of the first embodiment, the multi-channel light emitting element 104 is mounted in accordance with the position of the laser mounting marker 108 formed on the surface of the laser module substrate 101. On the other hand, in the optical module mounting method of the second embodiment, the multi-channel light emitting element 104 is mounted according to the position of the laser mounting marker 108 formed on the surface of the light emitting element mounting substrate 204. Thereafter, the light emitting element mounting substrate 204 on which the multi-channel light emitting element 104 is mounted is mounted on the side wall of the laser module substrate 201 with the optical axis aligned.

  More preferably, in the optical module mounting method of the first embodiment, the surface on which the active layer 104a of the multi-channel light emitting element 104 is formed faces downward and is mounted on the substrate. On the other hand, in the mounting method of the optical module according to the second embodiment, the surface of the multi-channel light emitting element 104 on which the active layer 104a is formed faces upward and is mounted on the substrate. In order to align and mount the optical axis of the light emitting element mounting substrate 204 and the laser module substrate 201, the multi-channel light emitting element 104 is actually driven and while monitoring the optical coupling loss with the polarization maintaining optical fiber 107, The positional relationship between the light emitting element mounting substrate 204 and the laser module substrate 201 may be adjusted. As above, the mounting method of the second embodiment has been described focusing on the differences from the first embodiment. Since other mounting methods are almost the same as the mounting method of the first embodiment, description thereof is omitted.

  As described above, in the optical module according to Embodiment 2, the multi-channel light emitting element 104 and the polarization maintaining optical fiber 107 are mounted on independent substrates, and the optical coupling loss between these optical components is monitored. Adjustment (alignment), so-called active alignment mounting becomes possible. In passive alignment mounting that uses a marker as a mark for adjustment (alignment), optical coupling loss may increase due to an optical component manufacturing error. On the other hand, in active alignment mounting, an optical component manufacturing error can be corrected in the mounting process, and therefore, mounting with lower optical coupling loss can be achieved.

  In the optical module according to Embodiment 2, the multi-channel light emitting element 104 is mounted on the laser module substrate 201 with a so-called junction-up structure with the surface on which the active layer 104a is formed facing upward. In the junction-down structure with the active layer 104a facing downward, there is a concern that reliability is deteriorated due to excessive stress applied by mounting. In contrast, the configuration of the second embodiment can achieve higher reliability. Note that the concern about the increase in inter-channel variation in optical coupling loss due to the substrate thickness variation in the junction-up structure is a problem only when passive alignment mounting is performed. Since the active alignment mounting is possible in the second embodiment, the above problem does not occur.

Embodiment 3

Next, the configuration of the third embodiment will be described with reference to FIGS. 10A and 10B. FIG. 10A is a perspective view of a main part of the optical module described in the third embodiment. FIG. 10B is an example of a cross-sectional view taken along a ₃ -a ₃ ′ in FIG. 10A. In the optical module shown in FIGS. 10A and 10B, the multi-channel laser module 312 is mounted on the surface of the thermoelectric cooler 305, and the reflection mirror 111 is mounted on the surface of the silicon photonics chip 113. The second embodiment is different from the second embodiment in the configuration of the multi-channel laser module, the mounting configuration, and the mounting configuration of the reflection mirror.

  In the configuration of the second embodiment, the optical isolator 110 and the reflection mirror 111 are mounted on the upper surface of the optical isolator / reflection mirror mounting portion 203 of the laser module substrate 201, and the laser module substrate 201 is laminated on the surface of the silicon photonics chip 113. Has been implemented. On the other hand, in the configuration of the third embodiment, the reflection mirror 111 is directly mounted on the surface of the silicon photonics chip 113, and the laser module substrate 301 on which the reflection mirror 111 is not mounted is mounted on the surface of the thermoelectric cooler 305. Has been. The other configuration is almost the same as the configuration of the second embodiment, and a description thereof will be omitted.

  Next, an example of an optical module mounting method according to the third embodiment will be described. In the optical module mounting method of the second embodiment, the multi-channel light emitting element 104 is actually driven and the optical coupling loss with the silicon photonics chip 113 is monitored, while the multi-channel laser module 212 and the silicon photonics chip 113 are connected. Adjust the positional relationship. On the other hand, in the optical module mounting method according to the third embodiment, the multichannel light emitting element 104 is actually driven and the optical coupling loss with the silicon photonics chip 113 is monitored, and the multichannel laser module 212 and the reflecting mirror are monitored. The positional relationship between the three members 111 and the silicon photonics chip 113 is adjusted. Since other mounting methods are almost the same as the mounting method of the second embodiment, description thereof is omitted.

  As described above, in the optical module according to Embodiment 3, the output-side gradient index lens 106 and the reflection mirror 111 are mounted on independent substrates, so that alignment can be performed with higher accuracy. When mounted on the same substrate as in the second embodiment, when an optical component manufacturing error occurs, the beam diameter of the light condensed by the output-side gradient index lens 106 is minimized. The beam waist position and the position of the diffraction grating type optical coupler 116 cannot be completely matched. On the other hand, the output-side gradient index lens 106 and the reflection mirror 111 are mounted on independent substrates, and the positional relationship between them can be freely changed by alignment. In this case, the beam waist position and the position of the diffraction grating type optical coupler 116 can be completely matched. That is, since an optical component manufacturing error can be corrected in the mounting process, mounting can be performed with lower optical coupling loss.

In the optical module according to Embodiment 3, the multi-channel laser module 312 is directly mounted on the surface of the thermoelectric cooler 305, and the temperature of the multi-channel light emitting element 104 can be controlled. By controlling the temperature, the oscillation wavelength of the multi-channel light emitting element 104 is stabilized, and a high-performance optical module can be realized. Even in the configuration described in the second embodiment, it is possible to control the temperature by mounting the entire silicon photonics chip 113 on which the multichannel laser module 212 is mounted on the surface of the thermoelectric cooler. . However, since the thermal conductivity of the SiO ₂ layer 115 on the surface of the silicon photonics chip 113 is low, it is difficult to efficiently control the temperature of only the multi-channel light emitting element 104. Therefore, in the configuration described in Embodiment 3, an optical module with high temperature control efficiency and low power consumption can be realized.

Embodiment 4

Next, the configuration of the fourth embodiment will be described with reference to FIGS. 11A and 11B. FIG. 11A is a perspective view of a main part of the optical module described in the fourth embodiment. FIG. 11B is a cross-sectional view taken along a ₄ -a ₄ ′ in FIG. 11A. The optical module shown in FIGS. 10A and 10B includes polarization-maintaining light including an input-side refractive index distribution type lens 105 and an output-side refractive index distribution type lens 106 on the input side output side on the upper surface of the optical fiber mounting substrate 401, respectively. A fiber 107 is mounted, and a rod mirror 411 is connected to the end face of the output-side gradient index lens 106.

  Here, the rod mirror 411 is an optical component having a function as a reflection mirror in which one end surface of cylindrical glass is obliquely polished. A fixing substrate 402 is bonded to the back surface of the optical fiber mounting substrate 401 by aligning one end surface (the right end surface in FIG. 11B). Further, the multi-channel light emitting element 104 is mounted on the upper surface of the light emitting element mounting substrate 204, and the optical fiber mounting substrate 401 and the light emitting element mounting substrate 204 are connected with their optical axes aligned. Hereinafter, the optical fiber mounting substrate 401, the input side refractive index distribution type lens 105, the output side refractive index distribution type lens 106, the polarization maintaining optical fiber 107, the rod mirror 411, the fixing substrate 402, the light emitting element mounting substrate 204, and many A device including the channel light emitting element 104 is referred to as a multi-channel laser module 412.

  The fixing substrate 402 of the multichannel laser module 412 is mounted on the surface of the silicon photonics chip 113. In addition, the back surface of the light emitting element mounting substrate 204 is in contact with the surface of the thermoelectric cooler 305 through the heat conductive sheet 403. Here, it is preferable that the heat conductive sheet 403 is, for example, a gel-like material having flexibility so as to absorb the height variation from the surface of the thermoelectric cooler 305 to the back surface of the light emitting element mounting substrate 204. On the upper surface of the silicon photonics chip 113, an optical isolator 110 is mounted in an orientation in which the optical axis direction is the direction perpendicular to the substrate of the silicon photonics chip 113. The other configuration is almost the same as the configuration of the third embodiment, and the description thereof is omitted.

  Next, an example of an optical module mounting method according to the fourth embodiment will be described. In the optical module mounting method of the fourth embodiment, first, the gradient index lenses 105 and 106 are bonded to both ends of the polarization maintaining optical fiber 170. As the bonding method, an adhesive may be used, or direct fusion may be used. At this time, as shown in FIG. 3B, bonding is performed so that the central axes of the respective components substantially coincide. Next, cylindrical glass is bonded to the end face of the output-side gradient index lens 106. As in the previous method, the adhesive may be an adhesive or may be directly fused. Next, the polarization maintaining optical fiber 170 to which the gradient index lenses 105 and 106 and the columnar glass are bonded is mounted so as to be fitted into the optical fiber mounting V-shaped groove 109 of the optical fiber mounting substrate 401.

  At this time, the position of the polarization maintaining optical fiber 170 in the optical axis vertical direction in the substrate surface is uniquely determined by the position of the optical fiber mounting V-groove 109, and the position in the substrate surface vertical direction is for optical fiber mounting. It is uniquely determined by the groove depth of the V groove 109. The position of the polarization maintaining optical fiber 170 in the optical axis direction may be positioned by matching with the optical fiber mounting marker provided on the surface of the optical fiber mounting substrate 401. However, it is more preferable that the optical fiber mounting substrate 301 is mounted so that the end surface of the input-side gradient index lens 105 is aligned with the end surface. In mounting the polarization-maintaining optical fiber 170, it is important to mount the polarization-maintaining optical fiber 170 in accordance with the above-described direction. The axial direction may be adjusted while monitoring the camera with the shape of the stress applying portion 107c as a mark, and the light is actually transmitted using a polarizer, an optical fiber, a laser, an optical power meter, etc. You may adjust while monitoring.

  Next, in the optical fiber mounting substrate 401 on which the gradient index lenses 105 and 106, the columnar glass, and the polarization maintaining optical fiber 170 are mounted, the end surface on the columnar glass side is polished by slanting. The polishing angle may be an angle at which the reflected light is most efficiently coupled with the diffraction grating type optical coupler, and is more preferably 39 degrees to 43 degrees. Next, the fixing substrate 402 is bonded to the back surface of the optical fiber mounting substrate 401. Here, more preferably, the position of the end surface of the fixing substrate 402 is made to substantially coincide with the position of the right end surface of the optical fiber mounting substrate 401, or the position is slightly retracted and bonded. Next, the multi-channel light emitting element 104 is mounted according to the position of the laser mounting marker 108 formed on the surface of the light emitting element mounting substrate 204, and then the light emitting element mounting substrate on which the multi-channel light emitting element 104 is mounted. 204 is mounted on the side wall of the optical fiber mounting substrate 401 with the optical axis aligned.

  More preferably, the surface on which the active layer 104a of the multi-channel light emitting element 104 is formed faces upward and is mounted on the substrate. In order to align and mount the optical axis of the light emitting element mounting substrate 204 and the laser module substrate 201, the multi-channel light emitting element 104 is actually driven and while monitoring the optical coupling loss with the polarization maintaining optical fiber 107, The positional relationship between the light emitting element mounting substrate 204 and the laser module substrate 201 may be adjusted. Thus, the multichannel laser module 412 is completed.

  Finally, the optical isolator 110 and the multichannel laser module 412 are mounted on the upper surface of the silicon photonics chip 113. At this time, the mounting position of the optical isolator may be positioned by matching with the optical isolator mounting marker provided on the surface of the silicon photonics chip 113. On the other hand, the mounting position of the multi-channel laser module 412 may be positioned by matching with a multi-channel laser module mounting marker provided on the surface of the silicon photonics chip 113. However, it is more preferable that the multi-channel light emitting element 104 is actually driven and positioned while monitoring the optical coupling loss with the silicon photonics chip 113. In mounting the multi-channel laser module 412, the fixing substrate 402 is connected to the silicon photonics chip 113, and the light emitting element mounting substrate 204 is connected to the heat conductive sheet 403 mounted on the surface of the thermoelectric cooler 305. That's fine.

  In the optical module according to Embodiment 4, the reflection mirror is integrated on the end face of the output-side gradient index lens 106. By integrating a plurality of functions in one optical component, it is possible to reduce the number of components, reduce the size of the components, and thereby reduce the size and cost of the optical module. Furthermore, if each optical component is miniaturized, the optical path length from the multi-channel light emitting element 104 serving as a light source to the diffraction grating type optical coupler 116 serving as a condensing destination can be shortened. When the optical path length is long, a slight mounting error leads to a large increase in optical coupling loss. On the other hand, the shorter the optical path length, the lower the optical coupling loss and the smaller the mounting.

In the optical module according to Embodiment 4, the light emitting element mounting substrate 204 of the multi-channel laser module 412 is in contact with the thermoelectric cooler 305 through the heat conductive sheet 403. As a result, the temperature control of the multichannel light emitting element 104 is possible. By controlling the temperature, the oscillation wavelength of the multi-channel light emitting element 104 is stabilized, and a high-performance optical module can be realized. Even in the configuration described in the second embodiment, it is possible to control the temperature by mounting the entire silicon photonics chip 113 on which the multichannel laser module 212 is mounted on the surface of the thermoelectric cooler. . However, since the thermal conductivity of the SiO ₂ layer 115 on the surface of the silicon photonics chip 113 is low, it is difficult to efficiently control the temperature of only the multi-channel light emitting element 104. Therefore, in the configuration described in the fourth embodiment, an optical module with high temperature control efficiency and low power consumption can be realized.

Embodiment 5

  Next, the configuration of the fifth embodiment will be described with reference to FIG. FIG. 12 is a top view of the main part of the wavelength division multiplexing optical transceiver described in the fifth embodiment. The wavelength division multiplexing optical transceiver shown in FIG. 12 is an example based on the configuration of the fourth embodiment described with reference to FIG. 11, but the wavelength division multiplexing optical transceiver module of the fifth embodiment is limited to this. Instead, the configuration of any of the first to third embodiments described with reference to FIGS. 1, 9, and 10 may be included.

  The wavelength division multiplexing optical transceiver shown in FIG. 12 includes a multi-channel laser module 412, an optical isolator 110, a thermoelectric cooler 305, a silicon photonics chip 113, and an optical fiber 522. The silicon photonics chip 113 is integrated with a diffraction grating type optical coupler 116, an optical waveguide 117, an optical modulator 520, an optical multiplexer 521, an optical demultiplexer 523, a light receiver 524, and a drive circuit 525. . The form of the drive circuit 525 may be a monolithic integrated form integrated on the same substrate as the silicon photonics chip 113, or formed on a separate substrate, and the substrate is on the surface of the silicon photonics chip 113. It may be a hybrid integrated form implemented in the above. The optical fiber 522 may be a single mode optical fiber. Although FIG. 12 shows the case where the number of channels is four as an example, the number of channels is not limited to this and may be two or more.

  The wavelength division multiplexing optical transceiver module shown in FIG. 12 has a diffraction grating type optical coupler 116 in which a plurality of unmodulated lights (continuous lights) emitted from the multi-channel laser module 412 are formed in the silicon photonics chip 113. Is input. The light input to the diffraction grating type optical coupler 116 is converted in the optical axis direction, propagates through the optical waveguide 117, and then is input to the optical modulator 520. The optical modulator 520 is electrically connected to the drive circuit 525 via the transmission line 526, and based on the signal sent from the drive circuit 525, the modulated light that is modulated at high speed from the input unmodulated light. Convert to A plurality of modulated lights having different wavelengths output from the respective optical modulators are multiplexed by the optical multiplexer 521 and output from one optical waveguide. The light output from the end of the optical waveguide is input to the optical fiber 522 and output from the wavelength division multiplexing optical transceiver module as a transmission optical signal 550.

  The wavelength division multiplexing optical transceiver module can also receive an optical signal. The received optical signal 551 input from the other optical fiber 522 is input to the optical demultiplexer 523 via the optical waveguide. The optical demultiplexer 523 separates a plurality of modulated lights having different wavelengths and outputs them to different optical waveguides for each wavelength. Each optical waveguide is connected to a light receiver 524, and the light receiver 524 is electrically connected to a drive circuit 525 via a transmission line 526. By driving each light receiver 524 with the drive circuit 525, the modulated light is converted into an electronic signal.

  Next, an example of a mounting method of the wavelength division multiplexing optical transceiver module according to the fifth embodiment will be described. In the method of mounting the wavelength division multiplexing optical transceiver module according to the fifth embodiment, first, the substrate on which the drive circuit 525 is formed is mounted on the surface of the silicon photonics chip 113. This step is necessary when the drive circuit 525 is in a hybrid integrated form, and is not necessary in the case of a monolithic integrated form. Next, the optical isolator 110 and the multi-channel laser module 412 are mounted on the upper surface of the silicon photonics chip 113. At this time, the mounting position of the optical isolator may be positioned by matching with the optical isolator mounting marker provided on the surface of the silicon photonics chip 113.

  On the other hand, the mounting position of the multi-channel laser module 412 may be positioned by matching with a multi-channel laser module mounting marker provided on the surface of the silicon photonics chip 113. However, it is more preferable that the multi-channel light emitting element 104 is actually driven and positioned while monitoring the optical coupling loss with the silicon photonics chip 113. In mounting the multi-channel laser module 412, the fixing substrate 402 is connected to the silicon photonics chip 113, and the light emitting element mounting substrate 204 is connected to the heat conductive sheet 403 mounted on the surface of the thermoelectric cooler 305. That's fine.

  Finally, by mounting two optical fibers 522 for transmission and reception on the silicon photonics chip 113, a wavelength division multiplexing optical transceiver module is completed. The mounting position of the optical fiber 522 may be positioned by matching with an optical fiber mounting marker provided on the surface of the silicon photonics chip 113. However, positioning is performed by fitting into an optical fiber mounting V-groove provided on the surface of the silicon photonics chip 113, or the multi-channel light emitting element 104 is actually driven to monitor the optical coupling loss with the optical fiber 522. Positioning is more preferable.

  The wavelength division multiplexing optical transceiver module according to Embodiment 5 can transmit and receive a plurality of optical signals having different wavelengths. Other configurations are almost the same as those in the first to fourth embodiments, and thus detailed description thereof is omitted. In particular, the wavelength division multiplexing optical transceiver module according to Embodiment 5 has small optical coupling loss, small variation between channels, high reliability, low cost, and low power consumption.

DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Ball lens 3 Optical isolator 4 Reflecting mirror 5 Holding substrate 6 Half wave plate 7 Laser module 8 Silicon photonics chip 9 Silicon substrate 10 SiO ₂ layer 11 Diffraction grating type optical coupler 12 Output light 101 Laser module substrate 102 Laser Optical fiber mounting section 103 Optical isolator / reflecting mirror mounting section 104 Multi-channel light emitting element 104a Active layer 105 Input side refractive index distribution type lens 105a First input side refractive index distribution type lens 105b Second input side refractive index distribution type lens 106 Output-side gradient index lens 107 Polarization-maintaining optical fiber 107a Polarization-maintaining optical fiber core portion 107b Polarization-maintaining optical fiber cladding portion 107c Polarization-maintaining optical fiber stress applying portion 107d Polarization-maintaining optical fiber input End face 107e of polarization maintaining optical fiber Output section end face 108 Laser mounting marker 109 Optical fiber mounting V groove 110 Optical isolator 110A Single stage optical isolator 110Aa, 110Ab Polarizer 110Ac Faraday rotator 110B 1.5 stage optical isolator 110Ba, 110Bb, 110Bc Polarizer 110Bd, 110Be Faraday rotator 111 Reflection mirror 112 Multichannel laser module 113 Silicon photonics chip 114 Silicon substrate 115 SiO ₂ layer 115a Lower clad layer 115b Upper clad layer 116 Diffraction grating type optical coupler 116a Diffraction grating part 116b Taper part 117 Optical waveguide 150 Out Light 150a Input light 150b to polarization maintaining fiber Output light 150c from polarization maintaining fiber Light 150d of outgoing light Input light 151 to diffraction grating type optical coupler Input light 160 to the circuit High-speed axis 161 of the polarization-maintaining optical fiber Low-speed axis 170 of the polarization-maintaining optical fiber Polarization rotation angle 180 Polarization direction 181 at the end face of the input portion of the polarization-maintaining optical fiber Polarization direction 182 at the output section end face Polarization direction 183 at the input section end face of the single stage optical isolator Polarization direction 184 at the output section end face of the single stage optical isolator At the input section end face of the diffraction grating type optical coupler Polarization direction 185 Polarization direction 186 at the input section end face of the 1.5-stage optical isolator Polarization direction 190 at the output section end face of the 1.5-stage optical isolator Light emitting point 191 Condensing point 201 Laser module substrate 202 Optical fiber mounting section 203 Optical isolator / reflection mirror mounting section 204 Light emitting element mounting substrate 212 Multi-channel laser module 301 Laser module substrate 302 Optical fiber Mounting part 303 Optical isolator mounting part 305 Thermoelectric cooler 312 Multichannel laser module 401 Optical fiber mounting board 402 Fixing board 403 Thermal conduction sheet 411 Rod mirror 412 Multichannel laser module 520 Optical modulator 521 Optical multiplexer 522 Optical fiber 523 Light Wave splitter 524 Light receiver 525 Drive circuit 526 Transmission line 550 Transmission optical signal 551 Reception optical signal.

Claims (15)

A multi-channel light-emitting unit having a plurality of light-emitting elements and a plurality of channels;
A multi-channel polarization maintaining unit having a plurality of channels on which a plurality of optical fibers are mounted;
An optical fiber holding substrate for holding the multi-channel polarization holding unit;
An optical isolator;
A multi-channel diffraction grating type optical coupler,
Each light emitting element of the multi-channel light emitting unit and one end of each optical fiber of the multi-channel polarization holding unit are optically connected,
The other end of each optical fiber of the multichannel polarization holding unit and the multichannel diffraction grating type optical coupler are optically connected,
The optical isolator is disposed on an optical path connecting the multi-channel polarization holding unit and the multi-channel diffraction grating type optical coupler,
The multi-channel polarization holding unit is held on the optical fiber holding substrate in a state in which a polarization plane between both ends of the optical fiber is rotated by an amount corresponding to a polarization rotation angle in the optical isolator. An optical module characterized in that   The optical module according to claim 1, wherein the light emitting element of the multi-channel light emitting unit is a semiconductor laser in which the oscillation wavelengths of the plurality of channels are different from each other. Each light emitting element of the multi-channel light emitting unit and one end of each optical fiber of the multi-channel polarization holding unit are connected via a first gradient index lens,
The optical module according to claim 1, wherein a second gradient index lens is connected to the other end of each optical fiber of the multichannel polarization holding unit.   The optical module according to claim 3, wherein a focal length of the first gradient index lens is shorter than a focal length of the second gradient index lens.   The light input from the multi-channel light emitting unit to the multi-channel polarization holding unit is linearly polarized light, and the plane of polarization coincides with the high-speed axis or the low-speed axis of the optical fiber of the multi-channel polarization holding unit. The optical module according to claim 1, wherein the linearly polarized state is maintained while the light propagates through the optical fiber. The optical isolator has a polarizing plate and a Faraday rotator,
2. The optical module according to claim 1, wherein an angle formed between a plane of polarization of incident light to the optical isolator and a plane of polarization of outgoing light from the optical isolator is 45 degrees or 90 degrees.   2. An optical path conversion mirror for converting an optical axis direction from 70 degrees to 90 degrees is disposed on an optical path connecting the optical isolator and the multichannel diffraction grating type optical coupler. The optical module as described. In the second gradient index lens, the end surface opposite to the end surface connected to the optical fiber is set so that the angle formed with the optical axis direction is 35 degrees to 45 degrees,
4. The optical module according to claim 3, wherein the first gradient index lens is set so as to convert the optical axis direction from 70 degrees to 90 degrees.   2. The optical module according to claim 1, wherein an optical waveguide for guiding input light is connected to the diffraction grating type optical coupler. On the surface of the optical fiber holding substrate, a plurality of grooves having a predetermined shape are formed linearly and in parallel,
The optical module according to claim 1, wherein each optical fiber of the multi-channel polarization holding unit is disposed in the groove. The light emitting device of the multi-channel light emitting unit has an active layer,
2. The optical module according to claim 1, wherein the multi-channel light emitting unit is arranged in such a direction that a surface on which the active layer is formed is in contact with a surface of the optical fiber holding substrate. . The light emitting device of the multi-channel light emitting unit has an active layer,
2. The multi-channel light emitting unit according to claim 1, wherein the multi-channel light emitting unit is disposed in an orientation such that a surface opposite to a side on which the active layer is formed is in contact with a surface of the optical fiber holding substrate. Optical module. A multi-channel light emitting unit having a plurality of light-emitting elements and a plurality of channels, a multi-channel polarization holding unit having a plurality of optical fibers and a plurality of channels, and the multi-channel polarization holding unit An optical fiber holding substrate, an optical isolator, and a multi-channel diffraction grating type optical coupler, each light-emitting element of the multi-channel light-emitting unit, and each optical fiber of the multi-channel polarization holding unit One end is optically connected, each optical fiber of the multi-channel polarization holding unit and the other end, and the multi-channel diffraction grating type optical coupler are optically connected, and the multi-channel polarization holding unit The optical isolator is disposed on an optical path connecting the multi-channel diffraction grating type optical coupler, and the multi-channel polarization holding unit is equivalent to a polarization rotation angle of the optical isolator. In a state in which the polarization plane across the serial optical fiber is twisted to rotate, an optical module configured held in the optical fiber holding substrate,
An optical circuit board on which at least the diffraction grating type optical coupler is formed,
The optical circuit board is:
An optical modulator for converting the modulated electrical signal into an optical signal;
A receiver for converting the modulated optical signal into an electrical signal;
A modulator driving circuit for driving the optical modulator;
A photoreceiver drive circuit for driving the photoreceiver;
A wavelength multiplexer / demultiplexer for multiplexing / demultiplexing light of a plurality of wavelengths,
An optical transmission / reception apparatus, wherein the plurality of wavelengths are multiplexed and transmitted / received. An optical module mounting method according to claim 1,
An alignment marker for mounting the multi-channel light emitting part formed on the surface of the optical fiber holding substrate, and a passive alignment step of adjusting the positional relationship between the multi-channel light emitting part based on image information;
A first active alignment step of adjusting a positional relationship between the optical fiber holding substrate and the optical circuit substrate while actually driving the multi-channel light emitting unit and monitoring light coupling efficiency;
A method for mounting an optical module, comprising:   The positional relationship between the multi-channel light emitting unit mounting substrate for mounting the multi-channel light emitting unit and the optical fiber holding substrate is adjusted while actually driving the multi-channel light emitting unit and monitoring the light coupling efficiency. The optical module mounting method according to claim 14, further comprising a second active alignment step.

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