JP2024047526A - Optical Modules - Google Patents

Abstract

[Problem] To provide an optical module capable of suppressing phase shift by making the temperature distribution closer to uniform. [Solution] An optical module according to an embodiment includes an optical element having a first side, a second side intersecting the first side, and a third side opposite the second side, a housing in which the optical element is housed, a thermoelectric cooler mounted inside the housing on which the optical element is mounted, a drive circuit arranged on the first side of the optical element, a first bonding pad arranged on the second side of the optical element, and a first wiring pattern provided on the frame of the housing and connected to the first bonding pad of the optical element via a first bonding wire, and the thermoelectric cooler has a plurality of Peltier elements arranged at intervals. The interval between the plurality of Peltier elements located on the second side is narrower than the interval between the plurality of Peltier elements located at the center of the optical element. [Selected Figure] Figure 3

Description

This disclosure relates to an optical module.

Patent Document 1 describes an optical transmission module. The optical transmission module has an optical modulation element optically coupled to an optical semiconductor laser element. The optical transmission module includes a temperature control device having a substrate having a main surface and a back surface, a first mounting portion on the main surface of the substrate via a first temperature control element and mounting a semiconductor laser element, and a second mounting portion on the main surface of the substrate via a second temperature control element and mounting an optical modulation element. The optical transmission module further includes a package that houses the semiconductor laser element, the optical modulation element, and the temperature control device, and an intermediate block that is disposed between the first temperature control element and the second temperature control element and is fixed to the main surface of the substrate.

JP 2021-174892 A

In an optical module equipped with a Mach-Zehnder (MZI) modulator, the Mach-Zehnder modulator adjusts the phase by using refractive index changes caused by electro-optical effects such as the quantum confined Stark effect and the Pockels effect. The Mach-Zehnder modulator has two waveguides that extend parallel to each other. If the temperature distribution in these two waveguides becomes non-uniform, the optical path length between p and n will change, and a phase shift may occur. Therefore, it may be necessary to make the temperature distribution more uniform and suppress the phase shift.

The present disclosure aims to provide an optical module that can reduce phase shifts by making the temperature distribution closer to uniform.

The optical module according to the present disclosure includes an optical element having a first side, a second side intersecting the first side, and a third side opposite the second side, a housing in which the optical element is housed, a thermoelectric cooler mounted inside the housing on which the optical element is mounted, a drive circuit arranged on the first side of the optical element, a first bonding pad arranged on the second side of the optical element, and a first wiring pattern provided on the frame of the housing and connected to the first bonding pad of the optical element via a first bonding wire, and the thermoelectric cooler has multiple Peltier elements arranged at intervals. The interval between the multiple Peltier elements located on the second side is narrower than the interval between the multiple Peltier elements located in the center of the optical element.

According to this disclosure, it is possible to make the temperature distribution more uniform and suppress phase shifts.

FIG. 1 is a partial cross-sectional view showing the internal structure of an optical module according to an embodiment. FIG. 2 is a plan view showing the optical element of the optical module of FIG. FIG. 3 is a plan view showing a schematic diagram of the thermoelectric cooler and the modulation element of the optical module shown in FIG. FIG. 4 is a graph showing the temperature distribution in the width direction of the optical module according to the first embodiment and the optical module according to the first comparative example. FIG. 5 is a graph different from FIG. 4, which shows the temperature distribution in the width direction of the optical module according to the first embodiment and the optical module according to the first comparative example. FIG. 6 is a graph showing the phase shift of the optical module according to the first embodiment and the optical module according to the first comparative example. FIG. 7 is a partial cross-sectional view showing the internal structure of the optical module according to the first modified example. FIG. 8 is a plan view illustrating a thermoelectric cooler and a modulation element of an optical module according to a second modified example. FIG. 9 is a graph showing the temperature distribution in the width direction of the optical module according to Example 2 and the optical module according to Comparative Example 2. FIG. 10 is a graph different from FIG. 9, which shows the temperature distribution in the width direction of the optical module according to Example 2 and the optical module according to Comparative Example 2. In FIG. FIG. 11 is a graph showing the phase shift of the optical module according to the second embodiment and the optical module according to the second comparative example. FIG. 12 is a plan view illustrating a thermoelectric cooler and a modulation element of an optical module according to a third modified example. FIG. 13 is a graph showing the temperature distribution in the width direction of the optical module according to Example 3 and the optical module according to Comparative Example 2. FIG. 14 is a graph different from FIG. 13 , which shows the temperature distribution in the width direction of the optical module according to Example 3 and the optical module according to Comparative Example 2. In FIG. FIG. 15 is a plan view illustrating a thermoelectric cooler and a modulation element of an optical module according to a fourth modified example.

[Description of the embodiments of the present disclosure]
First, the contents of the embodiment of the optical module according to the present disclosure will be listed and described. The optical module according to one embodiment includes: (1) an optical element having a first side, a second side intersecting the first side, and a third side opposite to the second side, a housing in which the optical element is housed, a thermoelectric cooler mounted inside the housing and on which the optical element is mounted, a drive circuit arranged on the first side of the optical element, a first bonding pad arranged on the second side of the optical element, and a first wiring pattern provided on the frame of the housing and connected to the first bonding pad of the optical element via a first bonding wire, and the thermoelectric cooler includes a plurality of Peltier elements arranged at intervals. The interval between the plurality of Peltier elements located on the second side is narrower than the interval between the plurality of Peltier elements located at the center of the optical element.

In this optical module, an optical element is mounted on a thermoelectric cooler. The optical element and the thermoelectric cooler are housed in a housing. The optical element has a second side and a third side opposite to the second side. A first bonding pad is arranged on the second side of the optical element. The frame of the housing has a first wiring pattern connected to the first bonding pad of the optical element via a first bonding wire. Since the first bonding pad and the first bonding wire are provided on the second side, heat is more likely to flow in and out on the second side compared to the center of the optical element. In this optical module, multiple Peltier elements are arranged at intervals on the thermoelectric cooler, and the interval between the multiple Peltier elements located on the second side is narrower than the interval between the multiple Peltier elements located in the center of the optical element. Therefore, since the Peltier elements are densely arranged on the second side compared to the center of the optical element, the influence of heat flow in and out on the second side can be reduced. Therefore, the temperature distribution of the optical element can be made closer to uniform, and phase shifts can be suppressed.

(2) In the above (1), the optical element may be a multimode interference device having a first optical waveguide through which a first signal light propagates and a second optical waveguide through which a second signal light different from the first signal light propagates. The first optical waveguide may be provided on the second side of the multimode interference device from the center, and the second optical waveguide may be provided on the third side of the multimode interference device from the center. In this case, the temperature of the first optical waveguide located on the second side and the temperature of the second optical waveguide located on the third side can be made closer to uniform.

(3) In the above (1) or (2), the optical module may include a second bonding pad arranged on the third side of the optical element, and a second wiring pattern provided on the frame of the housing and connected to the second bonding pad of the optical element via a second bonding wire. The interval between the multiple Peltier elements located on the third side may be narrower than the interval between the multiple Peltier elements located in the center of the optical element. In this case, since the second bonding pad and the second bonding wire are provided on the third side, heat is more likely to flow in and out on the third side compared to the center of the optical element. In this optical module, the interval between the multiple Peltier elements located on the third side is narrower than the interval between the multiple Peltier elements located in the center of the optical element. Therefore, since the Peltier elements are densely arranged on the third side compared to the center of the optical element, the influence of heat flow in and out on the third side can be reduced. Therefore, the temperature distribution of the optical element can be made closer to uniform, and phase shift can be suppressed.

(4) In any of (1) to (3) above, the optical module may include a third bonding pad arranged on the first side of the optical element, and a third wiring pattern provided in the drive circuit and connected to the third bonding pad of the optical element via a third bonding wire. The interval between the multiple Peltier elements located on the first side may be narrower than the interval between the multiple Peltier elements located in the center of the optical element. In this case, since the third bonding pad and the third bonding wire are provided on the first side, heat inflow and outflow is more likely to occur on the first side than in the center of the optical element. In this optical module, the interval between the multiple Peltier elements located on the first side is narrower than the interval between the multiple Peltier elements located in the center of the optical element. Therefore, since the Peltier elements are densely arranged on the first side compared to the center of the optical element, the influence of heat inflow and outflow on the first side can be reduced. Therefore, the temperature distribution of the optical element can be made closer to uniform, and phase shift can be suppressed.

(5) In the above (4), the drive circuit may be a heating element. The drive circuit is arranged on the first side of the optical element. In this optical module, as described above, Peltier elements are densely arranged on the first side of the optical element on which the drive circuit is arranged. This reduces the effect of heat flowing in and out of the drive circuit, making the temperature distribution of the optical element closer to uniform and suppressing phase shifts.

An optical module according to another embodiment includes (6) an optical element having a first side, a second side intersecting the first side, and a third side opposite the second side, a housing in which the optical element is housed, a thermoelectric cooler disposed inside the housing and on which the optical element is mounted, a first heat capacity section located around the optical element, and a second heat capacity section located around the optical element and at a location different from the first heat capacity section. The heat capacity of the first heat capacity section is greater than the heat capacity of the second heat capacity section. The thermoelectric cooler has multiple Peltier elements arranged at intervals. The interval between the multiple Peltier elements located on the first heat capacity section side is narrower than the interval between the multiple Peltier elements located on the second heat capacity section side.

In this optical module, an optical element is mounted on a thermoelectric cooler, and the optical element and the thermoelectric cooler are housed in a housing. The optical element has a second side and a third side opposite to the second side. A first heat capacity section and a second heat capacity section located at a different location from the first heat capacity section are arranged around the optical element. The heat capacity of the first heat capacity section is larger than that of the second heat capacity section. Therefore, the first heat capacity section is more likely to cause heat to flow in and out of the optical element than the second heat capacity section. In this optical module, multiple Peltier elements are arranged at intervals on the thermoelectric cooler, and the interval between the multiple Peltier elements located on the first heat capacity section side is narrower than the interval between the multiple Peltier elements located on the second heat capacity section side. Therefore, since the Peltier elements are densely arranged on the first heat capacity section side compared to the second heat capacity section side, the influence of heat flow in and out on the first heat capacity section side can be reduced. Therefore, the temperature distribution of the optical element can be made closer to uniform, and phase shifts can be suppressed.

[Details of the embodiment of the present disclosure]
Specific examples of optical modules according to embodiments of the present disclosure will be described below with reference to the drawings. The present invention is not limited to the following examples, but is intended to include all modifications within the scope of the claims and equivalents thereto. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and duplicate descriptions are omitted as appropriate. In addition, the drawings may be partially simplified or exaggerated for ease of understanding, and the dimensional ratios and the like are not limited to those shown in the drawings.

Figure 1 is a partial cross-sectional view showing the internal structure of an optical module 1 as an example. As shown in Figure 1, the optical module 1 includes a rectangular parallelepiped housing 2, and an input assembly 3 and an output assembly 4 extending from the housing 2. The input assembly 3 and the output assembly 4 each have a cylindrical shape. The housing 2 has a first side wall 2b extending along a first direction D1, a pair of second side walls 2c extending along a second direction D2 intersecting the first direction D1, and a bottom wall 2d on which each component of the optical module 1 is mounted. The first direction D1 is the longitudinal direction of the optical module 1, and the second direction D2 is the width direction of the optical module 1.

The first side wall 2b extends in both the first direction D1 and the third direction D3. The third direction D3 is a direction intersecting both the first direction D1 and the second direction D2, and corresponds to the height direction of the optical module 1. The pair of second side walls 2c are aligned along the first direction D1, and each second side wall 2c extends in both the second direction D2 and the third direction D3. The bottom wall 2d extends in both the first direction D1 and the second direction D2 at one end of the first side wall 2b and the second side wall 2c in the third direction D3. The pair of first side walls 2b and the pair of second side walls 2c constitute a frame body 2g of the housing 2 that has a frame shape when viewed from the third direction D3.

The input assembly 3 and the output assembly 4 extend from one of the pair of second side walls 2c along the first direction D1. The input assembly 3 and the output assembly 4 are aligned along the second direction D2. The input assembly 3 is a part that inputs input light L1 from the outside of the optical module 1 to the inside of the optical module 1. The output assembly 4 is a part that outputs output light L4 from the inside of the optical module 1 to the outside of the optical module 1. Each of the input assembly 3 and the output assembly 4 has a built-in lens. The input assembly 3 has a lens holder 3b that holds the lens of the input assembly 3, and the output assembly 4 has a lens holder 4b that holds the lens of the output assembly 4.

The optical module 1 comprises an optical base 11 mounted on the bottom wall 2d, and a filter 12 and a composite filter block 13 mounted on the optical base 11. The filter 12 transmits the input light L1 from the input assembly 3. The filter 12 inputs the input light L1 to the composite filter block 13. The composite filter block 13 is disposed on the opposite side of the filter 12 from the input assembly 3. The composite filter block 13 has a plurality of reflective surfaces 13b that reflect the input light L1.

The multiple reflecting surfaces 13b include a first reflecting surface 13c, a second reflecting surface 13d, a third reflecting surface 13f, and a fourth reflecting surface 13g. The first reflecting surface 13c and the second reflecting surface 13d are aligned along the second direction D2. The position of the third reflecting surface 13f in the second direction D2 is shifted from the position of the first reflecting surface 13c in the second direction D2 and the position of the second reflecting surface 13d in the second direction D2. The position of the fourth reflecting surface 13g in the second direction D2 is shifted from the position of the first reflecting surface 13c in the second direction D2 and the position of the second reflecting surface 13d in the second direction D2. The third reflecting surface 13f and the fourth reflecting surface 13g are aligned along the second direction D2.

The input light L1 that enters the composite filter block 13 from the filter 12 along the first direction D1 is reflected by the first reflecting surface 13c in the second direction D2. The input light L1 reflected by the first reflecting surface 13c is reflected by the second reflecting surface 13d in the first direction D1 and exits in the direction opposite the input assembly 3.

The output light L2 and output light L3, which will be described in detail later, are input to the composite filter block 13 from the side opposite the output assembly 4 along the first direction D1. The output light L2 is reflected in the second direction D2 by the third reflecting surface 13f. The output light L2 reflected by the third reflecting surface 13f is reflected in the first direction D1 by the fourth reflecting surface 13g. The output light L3 passes through the fourth reflecting surface 13g. The composite filter block 13 outputs the output light L2 and output light L3 to the output assembly 4 as output light L4. The output light L4 output to the output assembly 4 is output to the outside of the optical module 1.

The optical module 1 comprises a temperature control device (thermoelectric cooler) 21 mounted on the bottom wall 2d, a modulation element carrier 22 mounted on the temperature control device 21, and a modulation element (optical element) 30 mounted on the modulation element carrier 22. The optical module 1 comprises an input lens system 24, a first output lens system 25, and a second output lens system 26. The temperature control device 21 is a TEC (Thermo Electric Cooler).

The modulation element 30 is, for example, a multimode interference device in which a Mach-Zehnder interferometer is formed on an indium phosphide (InP) substrate. The modulation element 30 may also be an element in which an optical waveguide is formed on a Si substrate. As an example, the modulation element 30 includes indium phosphide (InP), silicon dioxide (SiO ₂ ), and benzocyclobutene (BCB). The temperature control device 21 and the modulation element 30 will be described in detail later. The input lens system 24 is mounted between the modulation element 30 and the composite filter block 13. The first output lens system 25 and the second output lens system 26 are mounted on both sides of the input lens system 24 in the second direction D2.

The optical module 1 includes a heat sink 41 located on the opposite side of the composite filter block 13 from the modulation element 30, and a driver IC (drive circuit) 42 mounted on the heat sink 41. FIG. 2 is a plan view showing the modulation element 30. The modulation element 30 is, for example, a multimode interference device having multiple optical waveguides. As shown in FIG. 2, the modulation element 30 includes, for example, a modulator chip 31, an input port 32, a first output port 33b, a second output port 33c, a branching section 34, a first multiplexing section 35b, a second multiplexing section 35c, optical waveguides 36a to 36h, a first monitor port 37b, and a second monitor port 37c.

As shown in Figs. 1 and 2, the planar shape of the modulator chip 31 is, for example, rectangular. The modulator chip 31 has sides 31b and 31c extending in the first direction D1 and sides 31d and 31f extending in the second direction D2. The input port 32 is an optical port into which the input light L1 output from the composite filter block 13 (second reflecting surface 13d) enters via the input lens system 24. The input port 32 is located on the side 31d. For example, the input port 32 is located at the center of the side 31d in the second direction D2. The driver IC 42 is located on the side 31f (first side) of the modulation element 30.

The first output port 33b is an optical port that outputs the output light (first signal light) L2 to the first output lens system 25, and the second output port 33c is an optical port that outputs the output light (second signal light) L3 to the second output lens system 26. The output light L2 output from the first output port 33b passes through the first output lens system 25 and enters the composite filter block 13. The output light L3 output from the second output port 33c passes through the second output lens system 26 and enters the composite filter block 13. The first output port 33b and the second output port 33c are provided on the side 31d of the modulator chip 31. The first output port 33b and the second output port 33c are arranged in positions symmetrical to each other with respect to the input port 32.

The branching unit 34 branches the input light L1 input from the input port 32 into the optical waveguides 36a to 36h. The first multiplexing unit 35b multiplexes the signal light (a portion of the multiple signal lights) that has propagated through the optical waveguides 36e to 36h, and provides it to the first output port 33b as output light L2. The second multiplexing unit 35c multiplexes the signal light (the remainder of the multiple signal lights) that has propagated through the optical waveguides 36a to 36d, and provides it to the second output port 33c as output light L3.

The modulation element 30 has modulation electrodes 38a to 38h, parent phase adjustment electrodes 38j to 38m, and a child phase adjustment electrode (not shown). The modulation electrodes 38a to 38h are provided on the optical waveguides 36a to 36h, respectively. The modulation electrodes 38a to 38h apply modulated voltage signals to the optical waveguides 36a to 36h to change the refractive index of the light passing through the optical waveguides 36a to 36h. This modulates the phase of the light propagating through the optical waveguides 36a to 36h.

One end of each of the modulation electrodes 38a to 38h is electrically connected to a respective RF pad 39a to 39h for signal input via a wiring pattern. The RF pads 39a to 39h for signal input are electrically connected to the driver IC 42. The other end of each of the modulation electrodes 38a to 38h is electrically connected to a respective signal pad 40a to 40h for signal termination via a wiring pattern. The parent phase adjustment electrodes 38j to 38m are electrically connected to each of the bias pads 39j to 39m via a wiring pattern. The child phase adjustment electrodes are connected to each of the bias pads 40j to 40q for adjustment signal input via a wiring pattern.

Figure 3 is a plan view showing the temperature control device 21, the modulation element 30, and the driver IC 42. As shown in Figure 3, the driver IC 42 has an electrode pad 42b. The electrode pads 42b are arranged along the second direction D2 at the end of the driver IC 42 on the modulation element 30 side. The optical module 1 has a wiring pattern (first wiring pattern) 2h provided on the frame 2g of the housing 2. The wiring pattern 2h is arranged along the first direction D1 at the end of the housing 2 in the second direction D2. The modulation element 30 has an electrode pad 30c at a position facing the driver IC 42, and the electrode pad 30c is arranged along the second direction D2. The optical module 1 has a bonding wire W2 that electrically connects the electrode pad 30c and the electrode pad 42b to each other.

For example, the modulation element 30 has a control terminal (first bonding pad) 30b. The control terminals 30b are arranged along the first direction D1 on the side 31c (second side). The wiring pattern 2h is connected to the control terminal 30b of the modulation element 30 via a bonding wire (first bonding wire) W1. Furthermore, the optical module 1 has a thermistor 28. The thermistor 28 is disposed, for example, between the modulation element 30 and the composite filter block 13. The thermistor 28 is electrically connected to a pad 2j provided on the frame body 2g via a bonding wire W3.

The temperature control device 21 has a plurality of Peltier elements 27. The plurality of Peltier elements 27 are arranged in a grid pattern so as to be aligned along the first direction D1 and the second direction D2. The plurality of Peltier elements 27 are arranged with a spacing S therebetween. For example, the spacing S between two Peltier elements 27 aligned along the second direction D2 varies depending on the position of the Peltier element 27 in the second direction D2. The spacing S between the plurality of Peltier elements 27 located on the side 31c (the control terminal 30b side of the modulation element 30, or the wiring pattern 2h side of the housing 2) is narrower than the spacing S between the plurality of Peltier elements 27 located on the side 31b. In other words, the plurality of Peltier elements 27 are arranged more densely on the side 31c than on the side 31b.

The interval S between the multiple Peltier elements 27 located on the side 31c is narrower than the interval S between the multiple Peltier elements 27 located at the center of the modulation element 30. The center of the optical element (modulation element 30) refers to the center of the optical element (modulation element 30) when viewed from the third direction D3. For example, the interval S1 between the Peltier element 27 located closest to the side 31c and the Peltier element 27 located second closest to the side 31c is narrower than the interval S2 between the Peltier element 27 located second closest to the side 31c and the Peltier element 27 located third closest to the side 31c. The interval S2 is narrower than the interval S3 between the Peltier element 27 located third closest to the side 31c and the Peltier element 27 located fourth closest to the side 31c. As an example, the interval S1 is 0.15 mm, the interval S2 is 0.2 mm, and the interval S3 is 0.25 mm. The interval S between the multiple Peltier elements 27 located at the center of the modulation element 30 may be the same as the interval S3.

Next, the effects of the optical module 1 according to the present embodiment will be described. In the optical module 1, the modulation element 30 is mounted on the temperature control device 21. The modulation element 30 and the temperature control device 21 are housed in the housing 2. The modulation element 30 has a side 31c and a side 31b facing the side 31c. A control terminal 30b is arranged on the side 31c of the modulation element 30 as a first bonding pad. The frame body 2g of the housing 2 has a wiring pattern 2h connected to the control terminal 30b of the modulation element 30 via a bonding wire W1. Since the control terminal 30b and the bonding wire W1 are provided on the side 31c, heat is more likely to flow in and out on the side 31c side than on the side 31b side. In the optical module 1, a plurality of Peltier elements 27 are arranged on the temperature control device 21 at intervals S, and the interval S between the plurality of Peltier elements 27 located on the side 31c side is narrower than the interval S between the plurality of Peltier elements 27 located on the side 31b side. Therefore, since the Peltier elements 27 are densely arranged on the side 31c side compared to the side 31b side, the influence of heat flow in and out on the side 31b side can be reduced. This makes the temperature distribution of the modulation element 30 closer to uniform, suppressing phase shifts.

In other words, since the control terminal 30b and the bonding wire W1 are provided on the side 31c side, heat is more likely to flow in and out on the side 31c side than in the center of the modulation element 30. In the optical module 1, the spacing S between the multiple Peltier elements 27 located on the side 31c side is narrower than the spacing S between the multiple Peltier elements 27 located in the center of the modulation element 30. Therefore, the Peltier elements 27 are densely arranged on the side 31c side compared to the center of the modulation element 30. This reduces the influence of heat flow in and out on the side 31c side, and makes the temperature distribution of the modulation element 30 more uniform, thereby suppressing phase shifts.

As described above, the modulation element 30 may be a multimode interference device having first optical waveguides 36e-36h through which output light L2, which is a first signal light, propagates, and second optical waveguides 36a-36d through which output light L3, which is a second signal light different from the output light L2, propagates. The first optical waveguides 36e-36h may be provided on the side 31b side of the multimode interference device, and the second optical waveguides 36a-36d may be provided on the side 31c side of the multimode interference device. In this case, the temperature of the first optical waveguides 36e-36h located on the side 31b side and the temperature of the second optical waveguides 36a-36d located on the side 31c side can be made closer to uniform.

Figure 4 is a graph showing the analysis results of the temperature distribution of the modulation element in the optical module according to Example 1 and the temperature distribution of the modulation element in the optical module according to Comparative Example 1 (the difference between the temperature distribution of the modulation element when the temperature of the optical module is 35 ° C. and the temperature distribution of the modulation element when the temperature of the optical module is 75 ° C.). The optical module according to Example 1 is the same as the optical module 1 described above. The optical module according to Comparative Example 1 differs from the optical module 1 in that the intervals between the two Peltier elements arranged along the width direction (second direction D2) are the same (multiple Peltier elements are uniformly arranged). The horizontal axis of Figure 4 indicates the displacement in the width direction (X direction), and the vertical axis of Figure 4 indicates the temperature difference on the line Z (see Figure 3) extending in the X direction when the center of the end (side 31b) opposite the control terminal of the modulation element is set to 0. As shown in Figure 4, in the optical module according to Comparative Example 1, the temperature becomes higher as it approaches the control terminal side. On the other hand, in the optical module of Example 1, the temperature rise is kept to 0.05°C or less even when approaching the control terminal, and it can be seen that the temperature distribution is closer to uniform.

Figure 5 is a graph showing the analysis results of the temperature distribution of the modulation element in the optical module of Example 1 and the temperature distribution of the modulation element in the optical module of Comparative Example 1 (the difference between the temperature distribution of the modulation element when the temperature of the optical module is 35°C and the temperature distribution of the modulation element when the temperature of the optical module is -5°C). As shown in Figure 5, in the optical module of Comparative Example 1, the temperature decreases as you get closer to the control terminal. On the other hand, in the optical module of Example 1, the temperature drop is kept to 0.05°C or less even when you get closer to the control terminal, and it can be seen that the temperature distribution is closer to uniform.

Figure 6 is a graph showing the analysis results of the phase shift of the first optical waveguide and the second optical waveguide in each of the optical module according to Example 1 and the optical module according to Comparative Example 1. As shown in Figure 6, in the optical module according to Comparative Example 1, a phase shift of 0.45π/°C occurred in the first optical waveguide, and a phase shift of 2.88π/°C occurred in the second optical waveguide. In contrast, in the optical module according to Example 1, a phase shift of 0.37π/°C occurred in the first optical waveguide, and a phase shift of 0.89π/°C occurred in the second optical waveguide. Thus, in Example 1, in which the arrangement of the Peltier elements becomes denser as it approaches the control terminal, the phase shift can be suppressed compared to Comparative Example 1, in which the arrangement of the Peltier elements is uniform. In particular, it was found that the optical module according to Example 1 can significantly suppress the phase shift in the width direction.

Next, various modified examples of the optical module according to the present disclosure will be described. Some of the configurations of the optical modules according to the various modified examples described below are the same as some of the configurations of the optical module 1 described above. Therefore, in the following description, descriptions that overlap with the description of the configuration of the optical module 1 will be omitted as appropriate by assigning the same reference numerals.

Figure 7 is a perspective view showing the internal structure of an optical module 1A according to a first modified example. Since part of the configuration of the optical module 1A is the same as part of the configuration of the optical module 1 described above, in the following, explanations that overlap with the explanation of the optical module 1 will be omitted as appropriate by assigning the same reference numerals. The optical module 1A has optical components different from those of the optical module 1. The optical module 1A has two temperature control devices 21, which are arranged side by side along the first direction D1. The two temperature control devices 21 are a first temperature control device 21A1 and a second temperature control device 21A2.

The optical module 1A has a tunable light source base 51 mounted on the first temperature control device 21A1, a tunable light source carrier 52 mounted on the tunable light source base 51, and a tunable light source element 53 mounted on the tunable light source carrier 52. The optical module 1A further has a plurality of lenses 54 mounted on the tunable light source base 51, a plurality of wavelength control monitor elements 55, a thermistor 56, an etalon filter 57, and an isolator 58. The light L11 output from the tunable light source element 53 is input to the plurality of lenses 54, and the light L11 transmitted through the plurality of lenses 54 is input to the isolator 58.

The optical module 1A has a modulation element base 61 mounted on the second temperature control device 21A2 and a modulation element carrier 62 mounted on the modulation element base 61, and the above-mentioned modulation element 30 is mounted on the modulation element carrier 62. The optical module 1A has a composite filter block 63 mounted on the modulation element base 61, a polarization synthesis filter 64, and a light receiving element 65 for monitoring the intensity of the modulated output light. The light L11 transmitted through the isolator 58 is input to the composite filter block 63 and the polarization synthesis filter 64. In the polarization synthesis filter 64, the output light L2 and the output light L3 are multiplexed and enter the composite filter block 63. A part of the multiplexed output light L2 and the output light L3 passes through the composite filter block 63 and is output from the output assembly 4 with a sleeve to the outside of the optical module 1. The remaining part of the multiplexed output light L2 and the output light L3 is reflected at the composite filter block 63 and monitored by the light receiving element 65 for monitoring the intensity of the modulated output light.

The optical module 1A has a first optical path adjustment filter 71, a mirror 72, a second optical path adjustment filter 73, a polarization separation filter 74, a lens 75 having a first lens portion 75b, a second lens portion 75c, and a third lens portion 75d, and a demodulation element carrier 76. The first optical path adjustment filter 71, the mirror 72, the second optical path adjustment filter 73, the polarization separation filter 74, the lens 75, and the demodulation element carrier 76 are mounted on the bottom wall 2d of the housing 2.

The optical module 1A has a TIA (Trans Impedance Amplifier) 77 mounted on a heat sink 41, a demodulation element 78 mounted on a demodulation element carrier 76, and an FPC (Flexible Printed Circuit) 79 extending from the housing 2 to the side opposite the input assembly 3 and the output assembly 4. The input light L1 input from the input assembly 3 to the inside of the optical module 1 passes through the first optical path adjustment filter 71 and enters the polarization separation filter 74.

A portion of the input light L1 that reaches the polarization separation filter 74 passes through the polarization separation filter 74 and enters the first lens portion 75b of the lens 75. The remaining portion of the input light L1 that reaches the polarization separation filter 74 is reflected twice by the polarization separation filter 74 and enters the third lens portion 75d of the lens 75. Light L11 enters the second optical path adjustment filter 73 and the mirror 72 from the composite filter block 63 in the second direction D2. Light L11 is reflected by the mirror 72 in the first direction D1 and enters the second lens portion 75c of the lens 75. The optical module 1A according to the first modified example has been described above. This optical module 1A also provides the same effects as the optical module 1 described above.

Figure 8 is a plan view showing the temperature control device 21B, the modulation element 30B, the driver IC 42, and the frame body 2k of the housing 2B of the optical module 1B according to the second modified example. As shown in Figure 8, the optical module 1B further has a wiring pattern 2p (second wiring pattern) provided on the frame body 2k of the housing 2B. The wiring pattern 2p is arranged along the first direction D1 on the opposite side of the wiring pattern 2h as viewed from the modulation element 30B. The modulation element 30B further has a control terminal (second bonding pad) 30d. The control terminal 30d is arranged along the first direction D1 on the side of the side 31b (third side). The wiring pattern 2p is connected to the control terminal 30d of the modulation element 30B via a bonding wire (second bonding wire) W4.

The temperature control device 21B has multiple Peltier elements 27. The spacing S between the multiple Peltier elements 27 located on the side 31b (the control terminal 30d side of the modulation element 30, or the wiring pattern 2p side of the housing 2B) is narrower than the spacing S between the multiple Peltier elements 27 located in the center of the modulation element 30. In other words, the multiple Peltier elements 27 are arranged more densely on the side 31b compared to the center of the modulation element 30.

For example, the distance S11 between the Peltier element 27 located closest to side 31b and the Peltier element 27 located second closest to side 31b is narrower than the distance S12 between the Peltier element 27 located second closest to side 31b and the Peltier element 27 located third closest to side 31b. The distance S12 is narrower than the distance S13 between the Peltier element 27 located third closest to side 31b and the Peltier element 27 located fourth closest to side 31b. As an example, the distance S11 is 0.15 mm, the distance S12 is 0.2 mm, and the distance S13 is 0.25 mm.

As described above, the optical module 1B according to the second modification includes a control terminal 30d arranged on the side 31b of the modulation element 30B, and a wiring pattern 2p provided on the frame body 2k of the housing 2B and connected to the control terminal 30d of the modulation element 30B via a bonding wire W4. The interval S between the multiple Peltier elements 27 located on the side 31b is narrower than the interval between the multiple Peltier elements 27 located at the center of the modulation element 30B. Since the control terminal 30d and the bonding wire W4 are provided on the side 31b, heat is more likely to flow in and out of the side 31b than in the center of the modulation element 30B. In the optical module 1B, the interval S between the multiple Peltier elements 27 located on the side 31b is narrower than the interval S between the multiple Peltier elements 27 located at the center of the modulation element 30B. Therefore, since the Peltier elements 27 are densely arranged on the side 31b compared to the center of the modulation element 30B, the influence of heat flow in and out on the side 31b can be reduced. This makes it possible to make the temperature distribution of the modulation element 30B more uniform and suppress phase shifts.

9 is a graph showing the analysis results of the temperature distribution of the modulation element in the optical module according to Example 2 and the temperature distribution of the modulation element in the optical module according to Comparative Example 2 (the difference between the temperature distribution of the modulation element when the temperature of the optical module is 35° C. and the temperature distribution of the modulation element when the temperature of the optical module is 75° C.). The optical module according to Example 2 is the same as the optical module 1B described above. The optical module according to Comparative Example 2 differs from the optical module 1B in that the intervals between the two Peltier elements 27 arranged along the width direction (second direction D2) are the same (multiple Peltier elements are uniformly arranged). The horizontal axis of FIG. 9 indicates the displacement in the width direction, and the vertical axis of FIG. 9 indicates the temperature difference on the line Z (see FIG. 8) extending in the X direction when the center of the side 31b of the modulation element is set to 0. As shown in FIG. 9, in the optical module according to Example 2, the temperature change is suppressed to 0.05° C. or less in the X direction compared to Comparative Example 2, and it can be seen that the temperature distribution is closer to uniform.

Figure 10 is a graph showing the analysis results of the temperature distribution of the modulation element in the optical module of Example 2 and the temperature distribution of the modulation element in the optical module of Comparative Example 2 (the difference between the temperature distribution of the modulation element when the temperature of the optical module is 35°C and the temperature distribution of the modulation element when the temperature of the optical module is -5°C). As shown in Figure 10, in the optical module of Example 2, the temperature change in the X direction is suppressed to 0.05°C or less compared to Comparative Example 2, and it can be seen that the temperature distribution is closer to uniform.

Figure 11 is a graph showing the analysis results of the phase shift of the first optical waveguide and the second optical waveguide in each of the optical module according to Example 2 and the optical module according to Comparative Example 2. As shown in Figure 11, in the optical module according to Comparative Example 2, a phase shift of 0.73π/°C occurred in the first optical waveguide, and a phase shift of 3.06π/°C occurred in the second optical waveguide. In contrast, in the optical module according to Example 2, a phase shift of 0.47π/°C occurred in the first optical waveguide, and a phase shift of 0.5π/°C occurred in the second optical waveguide. Thus, in Example 2, in which the arrangement of the Peltier elements becomes denser as it approaches the control terminal 30d, the phase shift can be suppressed compared to Comparative Example 2, in which the arrangement of the Peltier elements is uniform. In particular, it was found that the optical module according to Example 2 can significantly suppress the phase shift in the width direction.

Figure 12 is a plan view showing the temperature control device 21C, the modulation element 30C, the driver IC 42, and the frame body 2k of the housing 2B of the optical module 1C according to the third modified example. The driver IC 42 is a heating element. As shown in Figure 12, in the optical module 1C, the temperature control device 21C has a plurality of Peltier elements 27. The interval T between two Peltier elements 27 arranged along the first direction D1 varies depending on the position of the Peltier element 27 in the first direction D1. The interval T between the plurality of Peltier elements 27 located on the first side, side 31f (the electrode pad 30c side of the modulation element 30C, or the driver IC 42 side, which is the driving circuit) is narrower than the interval T between the plurality of Peltier elements 27 located at the center of the modulation element 30C. That is, the plurality of Peltier elements 27 are arranged more densely on the side 31f side than in the center of the modulation element 30C.

For example, the distance T1 between the Peltier element 27 located closest to side 31f and the Peltier element 27 located second closest to side 31f is narrower than the distance T2 between the Peltier element 27 located second closest to side 31f and the Peltier element 27 located third closest to side 31f. Distance T2 is narrower than the distance T3 between the Peltier element 27 located third closest to side 31f and the Peltier element 27 located fourth closest to side 31f. As an example, distance T1 is 0.15 mm, distance T2 is 0.2 mm, and distance T3 is 0.25 mm.

The optical module 1C includes a bonding wire W2 disposed on the side 31f of the modulation element 30C, and an electrode pad 42b provided on the driver IC 42 and connected to the electrode pad 30c (third bonding pad) of the modulation element 30 via the bonding wire W2 (third bonding wire). The interval T between the multiple Peltier elements 27 located on the side 31f is narrower than the interval T between the multiple Peltier elements 27 located at the center of the modulation element 30C. Since the electrode pad 30c and the bonding wire W2 are provided on the side 31f, heat is more likely to flow in and out on the side 31f side than in the center of the modulation element 30C. In the optical module 1C, the interval T between the multiple Peltier elements 27 located on the side 31f side is narrower than the interval T between the multiple Peltier elements 27 located at the center of the modulation element 30C. Therefore, since the Peltier elements 27 are densely arranged on the side 31f side compared to the center of the modulation element 30C, the influence of heat flow in and out on the side 31f side can be reduced. This makes it possible to make the temperature distribution of the modulation element 30C more uniform and suppress phase shifts.

In the optical module 1C, the driver IC 42, which is a driving circuit, is a heating element, and the driver IC 42 is arranged on the side 31f of the modulation element 30C. In the optical module 1C, as described above, the Peltier elements 27 are densely arranged on the side 31f of the modulation element 30C on which the driver IC 42 is arranged. This reduces the influence of heat flowing in and out from the driver IC 42, which is a heating element, and makes the temperature distribution of the modulation element 30C closer to uniform, thereby suppressing phase shifts.

Figure 13 is a graph showing the analysis results of the temperature distribution of the modulation element in the optical module according to Example 3 and the temperature distribution of the modulation element in the optical module according to Comparative Example 2 (the difference between the temperature distribution of the modulation element when the temperature of the optical module is 35°C and the temperature distribution of the modulation element when the temperature of the optical module is 75°C). The optical module according to Example 3 is the same as the optical module 1C described above. The horizontal axis of Figure 13 indicates the displacement in the width direction, and the vertical axis of Figure 13 indicates the temperature difference on line Z (see Figure 12) extending in the X direction when the center of side 31b of the modulation element is set to 0. As shown in Figure 13, in the optical module according to Example 3, the temperature change is suppressed to 0.05°C or less even when it is farther away from side 31b than in Comparative Example 2, and it can be seen that the temperature distribution is closer to uniform.

Figure 14 is a graph showing the analysis results of the temperature distribution of the modulation element in the optical module of Example 3 and the temperature distribution of the modulation element in the optical module of Comparative Example 2 (the difference between the temperature distribution of the modulation element when the temperature of the optical module is 35°C and the temperature distribution of the modulation element when the temperature of the optical module is -5°C). As shown in Figure 14, in the optical module of Example 3, the temperature change in the X direction is suppressed to 0.05°C or less compared to Comparative Example 2, and it can be seen that the temperature distribution is closer to uniform.

Figure 15 is a plan view that shows a schematic diagram of the temperature control device 21D, the modulation element 30D, the driver IC 42, and the frame body 2k of the housing 2B of the optical module 1D according to the fourth modified example. The optical module 1D differs from the optical module 1B described above in the number of bonding wires W4. The optical module 1D includes a first heat capacity portion P1 located around the modulation element 30D, and a second heat capacity portion P2 located around the modulation element 30D and at a different location from the first heat capacity portion P1.

The first heat capacity portion P1 is located on the side 31c when viewed from the modulation element 30D. The first heat capacity portion P1 includes a control terminal 30b arranged on the side 31c of the modulation element 30D, a bonding wire W1, and a wiring pattern 2h. The second heat capacity portion P2 is located on the side 31b when viewed from the modulation element 30D. The second heat capacity portion P2 includes a control terminal 30d arranged on the side 31b of the modulation element 30D, a bonding wire W4, and a wiring pattern 2p. The number of bonding wires W1 is greater than the number of bonding wires W4. Therefore, the heat capacity of the first heat capacity portion P1 is greater than the heat capacity of the second heat capacity portion P2. That is, the heat flow from the first heat capacity portion P1 to the modulation element 30D is greater than the heat flow from the second heat capacity portion P2 to the modulation element 30D.

In the temperature adjustment device 21D, the spacing S between two Peltier elements 27 aligned along the second direction D2 varies depending on the position of the Peltier elements 27 in the second direction D2. The spacing S between the Peltier elements 27 located on the first heat capacity portion P1 side (side 31c side) is narrower than the spacing S between the Peltier elements 27 located on the second heat capacity portion P2 side (side 31b side). In other words, the Peltier elements 27 are arranged more densely on the first heat capacity portion P1 side compared to the second heat capacity portion P2 side.

For example, the interval S1 between the Peltier element 27 located closest to side 31c and the Peltier element 27 located second closest to side 31c is narrower than the interval S21 between the Peltier element 27 located closest to side 31b and the Peltier element 27 located second closest to side 31b. For example, the interval S2 between the Peltier element 27 located second closest to 331c and the Peltier element 27 located third closest to side 31c is narrower than the interval S22 between the Peltier element 27 located second closest to side 31b and the Peltier element 27 located third closest to side 31b. For example, the interval S3 between the Peltier element 27 located third closest to side 31c and the Peltier element 27 located fourth closest to side 31c is the same as the interval S23 between the Peltier element 27 located third closest to side 31b and the Peltier element 27 located fourth closest to side 31b. As an example, the spacing S1 is 0.15 mm, the spacing S21 is 0.18 mm, the spacing S2 is 0.2 mm, the spacing S22 is 0.23 mm, and the spacing S3 and the spacing S23 are 0.25 mm.

In the optical module 1D, a modulation element 30D is mounted on the temperature control device 21D, and the modulation element 30D and the temperature control device 21D are housed in the housing 2B. The modulation element 30D has a side 31b and a side 31c opposite to the side 31b. A first heat capacity portion P1 and a second heat capacity portion P2 located at a different location from the first heat capacity portion P1 are arranged around the modulation element 30D. The heat capacity of the first heat capacity portion P1 is larger than that of the second heat capacity portion P2. Therefore, the first heat capacity portion P1 is more likely to cause heat to flow in and out of the modulation element 30D than the second heat capacity portion P2. In the optical module 1D, a plurality of Peltier elements 27 are arranged at intervals in the temperature control device 21D, and the interval S between the plurality of Peltier elements 27 located on the first heat capacity portion P1 side is narrower than the interval S between the plurality of Peltier elements 27 located on the second heat capacity portion P2 side. Therefore, since the Peltier elements 27 are densely arranged on the first heat capacity portion P1 side compared to the second heat capacity portion P2 side, the influence of heat flow in and out on the first heat capacity portion P1 side can be reduced. This makes the temperature distribution of the modulation element 30D closer to uniform, suppressing phase shifts.

The above describes the embodiments and various modifications of the optical module according to the present disclosure. However, the present invention is not limited to the above-described embodiments or modifications. In other words, it will be easily recognized by those skilled in the art that various modifications and variations are possible within the scope of the present invention without changing the gist of the claims. For example, the shape, size, number, material, and arrangement of each component of the optical module are not limited to the above-described contents and can be modified as appropriate.

1, 1A, 1B, 1C, 1D...optical module 2...housing 2b...first side wall 2B...housing 2c...second side wall 2d...bottom wall 2g...frame body 2h...wiring pattern (first wiring pattern)
2j: pad 2k: frame 2p: wiring pattern (second wiring pattern)
3... Input assembly 3b... Lens holder 4... Output assembly 4b... Lens holder 11... Optical base 12... Filter 13... Composite filter block 13b, 13c, 13d, 13f, 13g... Reflecting surfaces 21, 21A1, 21A2, 21B, 21C, 21D... Temperature control device (thermoelectric cooler)
22: Modulation element carrier 24: Input lens system 25, 26: Output lens system 27: Peltier element 28: Thermistor 30, 30B, 30C, 30D: Modulation elements (optical elements)
30b...Control terminal (first bonding pad)
30c...electrode pad (third bonding pad)
30d...Control terminal (second bonding pad)
31...modulator chip 31b...side (third side)
31c...side (second side)
31d...side 31f...side (first side)
32...input port 33b...output port 33c...output port 34...branching section 35b, 35c...multiplexing section 36a, 36b, 36c, 36d, 36e, 36f, 36g, 36h...optical waveguide 37b...first monitor port 37c...second monitor port 38a, 38b, 38c, 38d, 38e, 38f, 38g, 38h...modulation electrodes 38j, 38k, 38l, 38m...parent phase adjustment Electrodes 39a, 39b, 39c, 39d, 39e, 39f, 39g, 39h... RF pads 39j, 39k, 39l, 39m... Bias pads 40a, 40b, 40c, 40d, 40e, 40f, 40g, 40h... Signal pads 40j, 40k, 40l, 40m, 40n, 40o, 40p, 40q... Bias pad 41... Heat sink 42... Driver IC (drive circuit)
42b...electrode pad 51...base for tunable light source 52...carrier for tunable light source 53...tunable light source element 54...lens 55...wavelength control monitor element 56...thermistor 57...etalon filter 58...isolator 61...base for modulation element 62...carrier for modulation element 63...composite filter block 64...polarized wave synthesis filter 65...light receiving element for monitoring modulation output light intensity 71...optical path adjustment filter 72...mirror 73...optical path adjustment filter 74...polarized wave separation filter 75...lens 75b...first lens portion 75c...second lens portion 75d...third lens portion 76...carrier for demodulation element 77...TIA (Trans Impedance Amplifier)
78: Demodulation element 79: FPC (Flexible Printed Circuit)
D1: first direction D2: second direction D3: third direction IC42: driver (drive circuit)
L1: input light L2: output light (first signal light)
L3: Output light (second signal light)
L4...output light P1...first heat capacity portion P2...second heat capacity portion S, S1, S2, S3, S3, S11, S12, S13, S21, S22, S23, T, T1, T2, T3...interval W1...bonding wire (first bonding wire)
W2: bonding wire (third bonding wire)
W3: bonding wire W4: bonding wire (second bonding wire)

Claims (6)

an optical element having a first side, a second side intersecting the first side, and a third side opposite to the second side;
a housing in which the optical element is housed;
a thermoelectric cooler mounted inside the housing and on which the optical element is mounted;
A drive circuit disposed on the first side of the optical element;
a first bonding pad disposed on the second side of the optical element;
a first wiring pattern provided on a frame of the housing and connected to the first bonding pad of the optical element via a first bonding wire;
Equipped with
The thermoelectric cooler includes a plurality of Peltier elements arranged at intervals;
the spacing between the Peltier elements located on the second side is narrower than the spacing between the Peltier elements located at the center of the optical element;
Optical module. the optical element is a multimode interference device having a first optical waveguide through which a first signal light propagates and a second optical waveguide through which a second signal light different from the first signal light propagates;
the first optical waveguide is provided on the second side from a center of the multi-mode interference device,
the second optical waveguide is provided on the third side from the center of the multi-mode interference device;
2. The optical module according to claim 1. a second bonding pad disposed on the third side of the optical element;
a second wiring pattern provided on a frame of the housing and connected to the second bonding pad of the optical element via a second bonding wire;
Equipped with
the spacing between the Peltier elements located on the third side is narrower than the spacing between the Peltier elements located at the center of the optical element;
3. The optical module according to claim 1 or 2. a third bonding pad disposed on the first side of the optical element;
a third wiring pattern provided in the drive circuit and connected to the third bonding pad of the optical element via a third bonding wire;
Equipped with
The spacing between the Peltier elements located on the first side is narrower than the spacing between the Peltier elements located at the center of the optical element.
3. The optical module according to claim 1 or 2. The drive circuit is a heating element.
5. The optical module according to claim 4. an optical element having a first side, a second side intersecting the first side, and a third side opposite to the second side;
a housing in which the optical element is housed;
a thermoelectric cooler disposed inside the housing and on which the optical element is mounted;
A first heat capacity portion located around the optical element;
a second heat capacity portion located around the optical element and at a different location from the first heat capacity portion;
Equipped with
The heat capacity of the first heat capacity portion is greater than the heat capacity of the second heat capacity portion,
The thermoelectric cooler includes a plurality of Peltier elements arranged at intervals;
The intervals between the Peltier elements located on the first heat capacity portion side are narrower than the intervals between the Peltier elements located on the second heat capacity portion side.
Optical module.

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