JP2016038486A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module that can achieve a reduction in thickness.SOLUTION: An optical module 1 comprises a light emitting/receiving element 21, an optical coupling part 25, a circuit substrate 13 to be mounted with electronic components 19, an electric connector 40 connected to one end of the circuit substrate 13, an optical cable 2 that includes an optical fiber 6 connected to the optical coupling part 25, and a housing 12 for housing the circuit substrate 13. The circuit substrate 13 includes a first substrate 13a to which the electric connector 40 is connected, a second substrate 13b to be mounted with the optical coupling part 25, and a coupling part 13c that couples the first substrate 13a and the second substrate 13b to each other. The second substrate 13b is disposed to be offset relative to the first substrate 13a in a direction opposite to a first surface M3 on which the optical coupling part 25 is disposed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an optical module.

As an optical cable for transmitting and receiving large-capacity data, there is an active optical cable (AOC). AOC has a function of correcting distortion of a signal waveform that occurs during transmission.
Patent Document 1 describes an optical module that can be used for AOC. In this optical module, an electrical signal is input from an electrical connector and converted into an optical signal by a photoelectric conversion unit mounted on a circuit board. Then, an optical signal is transmitted through an optical fiber optically connected to the photoelectric conversion unit.

JP2013-137479A

  The optical module described above is connected to an electronic device such as a personal computer or a portable information terminal. In recent years, electronic devices are becoming thinner. Therefore, it is desired to further reduce the thickness of optical modules connected to these electronic devices.

  Therefore, an object of the present invention is to provide an optical module that can be thinned.

  One embodiment of the present invention includes a circuit board on which an optical element, an optical coupling unit, and an electronic component are mounted, an electrical connector connected to one end of the circuit board, an optical cable including an optical fiber connected to the optical coupling unit, and a circuit An optical module comprising a housing for housing a board, wherein the circuit board includes a first board to which an electrical connector is connected, a second board on which the optical coupling portion is mounted, a first board, and a second board. And the second substrate is disposed so as to be offset with respect to the first substrate in a direction opposite to the first surface on which the optical coupling portion is disposed. .

  According to the present invention, an optical module capable of being thinned is provided.

1 is a perspective view of an optical module according to a first embodiment of the present invention. It is sectional drawing of an optical cable. It is a disassembled perspective view of an optical module. It is sectional drawing of an optical module. It is sectional drawing of an electrical connector. It is sectional drawing which shows the principal part of an optical module. It is sectional drawing of the optical module which concerns on the modification of this invention. It is sectional drawing which shows the principal part of the optical module which concerns on another modification of this invention. It is sectional drawing of the optical module which concerns on another modification of this invention. FIG. 10 is a plan view of the optical module shown in FIG. 9.

[Description of Embodiment of Present Invention]
First, embodiments of the present invention will be listed and described.

  One embodiment of the present invention includes a circuit board on which an optical element, an optical coupling unit, and an electronic component are mounted, an electrical connector connected to one end of the circuit board, an optical cable including an optical fiber connected to the optical coupling unit, and a circuit An optical module comprising a housing for housing a board, wherein the circuit board includes a first board to which an electrical connector is connected, a second board on which the optical coupling portion is mounted, a first board, and a second board. And the second substrate is disposed so as to be offset with respect to the first substrate in a direction opposite to the first surface on which the optical coupling portion is disposed. .

  According to this optical module, since the optical coupling part, which is a relatively bulky part, can be efficiently accommodated in the housing, the optical module can be thinned.

  Further, the first surface may be mounted with an electronic component having the greatest height in the normal direction of the first surface. Thereby, the bulky electronic component can be arranged in the housing.

  A heat radiating portion that thermally connects the circuit board and the housing may be mounted on the second surface, which is the back surface of the first surface. The height of the second gap between the second surface and the housing in the normal direction of the second surface is the same as the first surface of the first gap between the first surface and the housing. It is preferable to be smaller than the height in the line direction. Thereby, a thermal radiation part can be made thin. Therefore, the heat generated in the optical coupling part and the electronic component can be efficiently radiated through the circuit board.

  A portion where the optical fiber is bent along a plane parallel to the first surface may be disposed in the first gap between the first surface and the housing. Thereby, when changing the direction which the front-end | tip of an optical fiber faces, the space which accommodates the part by which the optical fiber was bent is securable.

  The electronic component includes a waveform shaper, and the first substrate includes the waveform shaper. The first substrate and the housing are thermally connected to each other in the normal direction of the first surface, and the second substrate and the housing are thermally connected to each other in the normal direction of the second surface. It is preferable that Thereby, the optical coupling part and the waveform shaper which are parts having a large calorific value can be thermally separated.

  The connecting part may be equipped with an electronic component. Thereby, the mounting density of electronic components is improved, and the circuit board can be reduced in size.

  The optical coupling portion includes a ferrule having a hole for holding the optical fiber, the housing includes an introduction portion for introducing the optical fiber from the rear end, and the height from the first surface to the hole is from the first surface to the introduction portion. It may be approximately the same as the height up to. Thereby, the optical fiber introduced into the housing is held in the optical coupling portion without being bent in the height direction. Therefore, damage to the optical fiber can be prevented.

[Details of the embodiment of the present invention]
Specific examples of the optical module according to the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to the claim are included. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
As shown in FIG. 1, the optical module 1 according to the first embodiment includes an optical cable 2 and a connector module 3. The optical cable 2 transmits optical signals in both directions. The connector module 3 is connected to an electronic device such as a personal computer, converts an optical signal transmitted through the optical cable 2 into an electrical signal, and outputs the electrical signal to the electronic device. The connector module 3 converts an electrical signal output from the electronic device into an optical signal and outputs the optical signal to the optical cable 2.

  As shown in FIG. 2, the optical cable 2 includes an optical fiber tape 4, an inner tube 7, an intervening layer 8, and a metal layer 9. The optical fiber tape 4 is formed by arranging a plurality of optical fibers 6 in parallel and integrating them in a tape shape with a coating resin. The optical fiber tape 4 is accommodated in the inner tube 7. Furthermore, the inner tube 7 is covered with an intervening layer 8 which is a tensile strength fiber. The intervening layer 8 is covered with a metal layer 9 made of a plurality of metal fibers. The metal layer 9 is covered with an outer cover 11 made of an insulating resin.

  The optical fiber 6 is a small diameter HPCF (HPCF: Hard Plastic Clad Fiber). The optical fiber 6 has a glass core and a hard plastic clad. The diameter of the core is 80 μm as an example. According to such an optical fiber 6, it is difficult to break even when the optical fiber 6 is bent to a small diameter. Moreover, according to the optical fiber 6, the increase in the optical loss by bending can be suppressed. The optical fiber 6 may be an AGF (AGF: All Glass Fiber) having a glass core and a glass cladding.

  The inner tube 7 is made of an insulating resin. Examples of the insulating resin include PVC (Polyvinylchloride) which is a non-halogen flame retardant resin. The intervening layer 8 is a tensile fiber such as an ultrafine aramid fiber. The metal layer 9 is a metal braid obtained by braiding a plurality of tin-plated conductive wires. The jacket 11 is made of an insulating resin. Examples of this insulating resin include polyolefin.

  As shown in FIG. 1, the connector module 3 includes a housing 12, an electrical connector 40, and a circuit board 13 (see FIG. 3). The electrical connector 40 is provided at the front end of the housing 12. The circuit board 13 is accommodated in the housing 12. In the following description, for convenience of explanation, the electrical connector 40 side is called “front” and the optical cable 2 side is called “rear”. And as FIG. 1 shows, the direction orthogonal to this front-back direction D1 is called the width direction D2. A direction perpendicular to each of the front-rear direction D1 and the width direction D2 is referred to as a height direction D3.

  As shown in FIG. 3, the housing 12 includes a metal housing 14 and a resin housing 16. The metal housing 14 dissipates heat generated from the circuit board 13 and the like to the outside. The metal housing 14 includes a cover 14a having a substantially U-shaped cross section and a base plate 14b having a substantially U-shaped cross section, and defines an internal space that accommodates the circuit board 13 and the like. An electrical connector 40 is disposed at the front end of the metal housing 14. An optical cable holding part 17 is attached to the rear end of the metal housing 14. The optical cable holding part 17 has a plate-like base part 17a. The metal housing 14 is made of a metal material having a high thermal conductivity. The thermal conductivity of the metal material is preferably 100 W / m · K or more. For example, the metal housing 14 is made of steel (Fe-based), tin (tin-plated copper), stainless steel, copper, brass, aluminum, or the like.

  As shown in FIG. 4, the housing 12 has an introduction portion 14 c. The introduction part 14c introduces the optical fiber 6 into the accommodation space K from the rear end. The introduction portion 14c has a center axis A1 in the height direction D3 that coincides with a center axis AX in the height direction D3 of the electrical connector 40 described later. The rear wall of the metal housing 14 including the introduction portion 14c may be configured separately from the cover 14a and the base plate 14b.

  The resin housing 16 covers the metal housing 14 and is formed of a resin material such as polycarbonate. The boot 15 is attached to the rear end of the resin housing 16 and covers the optical cable holding portion 17. The rear end of the boot 15 is bonded to the jacket 11 of the optical cable 2.

  The circuit board 13 is accommodated in the accommodation space K. The circuit board 13 has an insulating substrate and a pattern wiring P. The insulating substrate is, for example, a glass epoxy substrate or a ceramic substrate. The pattern wiring P is formed on the surface or inside of the insulating substrate. The pattern wiring P is, for example, gold (Au), aluminum (Al), or copper (Cu).

  The circuit board 13 includes a first board 13a, a connecting portion 13c, and a second board 13b from the front along the front-rear direction D1. The circuit board 13 is bent between the first board 13a and the connecting part 13c, and is further bent between the connecting part 13c and the second board 13b.

  On the first surface M3 of the circuit board 13, a waveform shaper 19a, a light emitting / receiving element 21, an IC (not shown) for controlling the light emitting / receiving element 21, and a lens module 22 are mounted. An electrical connector 40 is attached to the front end of the circuit board 13. Various electronic components 19c are attached to both surfaces of the connecting portion 13c.

  As shown in FIG. 5, the electrical connector 40 includes a main body 41 and a pair of terminals 42. The main body 41 holds the pair of terminals 42 with a predetermined gap. The main body 41 has a connection port insertion part 41a and a board insertion part 41b. The connection port insertion part 41 a is formed in front of the main body 41. The board insertion part 41 b is formed behind the main body 41.

  The terminal 42 ensures electrical connection between the optical module 1 and the electronic device. The terminal 42 has a terminal contact portion 42a, and ensures electrical connection by sandwiching the contact terminal of the connection port of the electronic device.

  Moreover, the terminal 42 has the board | substrate contact part 42b formed in the board | substrate insertion part 41b. The board contact portion 42b secures electrical connection by sandwiching the pattern wiring P of the circuit board 13.

  A plurality of electronic components 19 are mounted on the circuit board 13. The electronic component 19 is mounted on the first substrate 13a, the second substrate 13b, and the connecting portion 13c. The electronic component 19 includes a CDR (Clock Data Recovery) device that is a power supply circuit and a waveform shaper 19a.

  The optical coupling unit 25 includes a light emitting / receiving element 21, an IC (not shown) that controls the light emitting / receiving element, a lens module 22, and a ferrule 23. The optical coupling unit 25 converts an optical signal transmitted through the optical cable 2 into an electrical signal. The optical coupling unit 25 converts the electrical signal output from the electronic device into an optical signal and outputs the optical signal to the optical cable 2.

  The light emitting / receiving element 21 includes a light emitting element and a light receiving element. The light emitting element is, for example, a laser diode (LD) or a surface emitting laser (VCSEL). The light receiving element is, for example, a photodiode (PD: Photo Diode).

  The light emitting / receiving element (optical element) 21 is optically connected to the optical fiber 6. As shown in FIG. 4, the lens module 22 is disposed on the circuit board 13. The lens module 22 covers the light emitting / receiving element 21. The lens module 22 includes a reflection part and a lens. The reflection unit deflects the light emitted from the light emitting element so as to be coupled to the optical fiber 6. The reflection unit deflects the light emitted from the optical fiber 6 so as to be coupled to the light receiving element. The lens condenses the light emitted from the light emitting element so as to be coupled to the optical fiber 6. The lens condenses the light emitted from the optical fiber 6 so as to be coupled to the light receiving element.

  A ferrule 23 is attached to the end of the optical fiber 6. The ferrule 23 is coupled to the lens module 22 so that the optical fiber 6 and the light emitting / receiving element 21 are optically connected.

  The heat dissipating sheet (heat dissipating part) 43 is disposed between the circuit board 13 and the metal housing 14. The heat radiation sheet 43 has a function of thermally connecting the circuit board 13 and the metal housing 14 and transmitting heat generated from the electronic component 19 and the light emitting / receiving element 21 to the metal housing 14. The heat dissipation sheet 43 is formed from a material having thermal conductivity and flexibility.

  The term “thermally connected” here means that a path capable of transferring heat is established by physical connection. Therefore, in the present embodiment, heat transfer through a medium such as air does not correspond to thermal connection.

  The heat generated in the electronic component 19b is transmitted to the base plate 14b through the heat dissipation sheet 43. Next, the heat is transferred to the electrical connector 40 and the optical cable holding unit 17 connected to the metal housing 14. The heat transmitted to the electrical connector 40 is released to an external device to which the electrical connector 40 is connected. The heat transmitted to the optical cable holding unit 17 is transmitted to the metal layer 9 of the optical cable 2. The heat transmitted to the metal layer 9 is released to the outside through the outer cover 11.

  Hereinafter, the positional relationship of the component parts in the connector module 3 will be described in detail.

  The circuit board 13 will be described. As shown in FIG. 6, the first board 13 a is a part including the front end of the circuit board 13 and is arranged on the front side in the accommodation space K. An electrical connector 40 is attached to the front end of the first substrate 13a. The first substrate 13a has an upper surface M1 and a back surface M2, and an electronic component 19d is attached to the upper surface M1 and the back surface M2.

  In addition, the first substrate 13a is disposed at the approximate center between the cover 14a and the base plate 14b in the height direction D3, and is disposed on the central axis AX. A gap S1 is formed between the upper surface M1 and the cover 14a. A gap S2 is formed between the back surface M2 and the base plate 14b. The height of the gap S1 in the normal direction (height direction D3) of the upper surface M1 is substantially equal to the height of the gap S2 in the normal direction (height direction D3) of the back surface M2.

  The second board 13 b is a part including the rear end of the circuit board 13 and is arranged on the rear side in the accommodation space K. The second substrate 13b has an upper surface (first surface) M3 and a lower surface (second surface) M4. A waveform shaper 19a having the largest height in the normal direction (height direction D3) is mounted on the upper surface M3. An electronic component 19 is mounted on the lower surface M4.

  The second substrate 13b is disposed so as to be offset in the direction of the lower surface M4 with respect to the first substrate 13a, and the lower surface M4 is close to the base plate 14b. That is, the second substrate 13b is disposed so as to be offset toward the base plate 14b with respect to the central axis AX. A first gap S3 is formed between the upper surface M3 and the cover 14a. A second gap S4 is formed between the lower surface M4 and the base plate 14b. The height of the second gap S4 is smaller than the height of the first gap S3. That is, the second gap S4 is reduced by the height obtained by offsetting the second substrate 13b, and the height of the first gap S3 is increased. Further, the gap S3 includes a gap S5 between the electrical connector 40 and the lens module 22. Further, the gap S4 includes a gap S6 that is between the electrical connector 40 and the electronic component 19b.

  A heat radiation sheet 43 is mounted on the lower surface M4. The upper surface of the heat dissipation sheet 43 is physically and thermally connected to the electronic component 19b on the lower surface M4. The lower surface of the heat dissipation sheet 43 is physically and thermally connected to the base plate 14b. In this way, the circuit board 13 and the base plate 14 b are thermally connected via the heat dissipation sheet 43.

  The ferrule 23 will be described. The ferrule 23 is disposed on the central axis AX on the rear end side of the upper surface M3. The ferrule 23 has a hole 23 a that holds the optical fiber 6. The hole 23a extends along the front-rear direction D1 and is disposed on the central axis AX. That is, the hole 23a is disposed on the central axis A1 of the introduction portion 14c. In order to arrange the hole 23a at such a position, the offset length of the second substrate 13b is made substantially the same as the height SF from the upper surface M3 to the central axis A1.

  The electrical connector 40 will be described. The first substrate 13a and the introduction portion 14c overlap the central axis AX of the electrical connector 40. Therefore, the electrical connector 40 and the first substrate 13a are disposed substantially coaxially. Further, the electrical connector 40 and the introduction portion 14c are arranged substantially coaxially. As shown in FIG. 5, in the electrical connector 40, the pair of terminals 42 are spaced apart from each other along the height direction D <b> 3. A gap S7 is formed between the terminal contact portions 42a. A gap S8 is formed between the substrate contact portions 42b. The center axis AX of the electrical connector 40 is defined by the center point of the gaps S7 and S8 in the height direction D3.

  In the optical module 1, the circuit board 13 includes a first board 13a to which the electrical connector 40 is connected, a second board 13b on which the optical coupling unit 25 is mounted, a first board 13a, and a second board 13b. And a connecting portion 13c that connects the two. Accordingly, the position of the second substrate 13b can be made different from the position of the first substrate 13a. And the 2nd board | substrate 13b is arrange | positioned with respect to the 1st board | substrate 13a so that it may offset in the direction opposite to the upper surface M3 in which the optical coupling part 25 is arrange | positioned. Therefore, according to the optical module 1, the optical coupling unit 25, which is a relatively bulky component, can be efficiently accommodated in the housing 12, so that the optical module 1 can be thinned.

  In the circuit board 13, the first board 13a and the second board 13b are connected by a connecting part 13c. Therefore, the relative positions of the first substrate 13a and the second substrate 13b can be maintained without using separate components. Therefore, the configuration of the optical module 1 can be simplified.

  Further, the first board 13 a is disposed on the central axis AX of the electrical connector 40. More specifically, a reference axis passing through the center of the first substrate 13a in the height direction D3 coincides with the central axis AX. Accordingly, the pair of terminals 42 are line symmetric with respect to the reference axis in the height direction D3. Therefore, the electrical connector 40 can be attached to the circuit board 13 in a stable form.

  Further, according to the arrangement of the second substrate 13b, the introduction portion 14c and the hole 23b can be arranged coaxially. Therefore, the optical fiber 6 can be arranged substantially linearly from the introduction portion 14c to the hole 23a. According to such an arrangement of the optical fiber 6, the optical fiber 6 does not physically interfere with the circuit board 13 between the introduction portion 14c and the hole 23a. Therefore, the optical fiber 6 can be protected. Furthermore, in order to avoid interference between the optical fiber 6 and the circuit board 13, it is not necessary to provide a recess or notch at the rear end of the circuit board 13. Therefore, the strength reduction of the circuit board 13 can be prevented. Further, the lens module 22 and the like can be easily arranged.

  Further, the waveform shaper 19a having the largest height in the normal direction of the upper surface M3 is mounted on the upper surface M3. Thereby, the bulky waveform shaper 19a can be arranged in the housing 12.

  In the optical module 1, a heat radiation sheet 43 that thermally connects the circuit board 13 and the housing 12 is mounted on the lower surface M4 that is the surface on the back side of the upper surface M3. The height of the second gap S4 between the lower surface M4 and the housing 12 in the normal direction of the lower surface M4 is the height of the first gap S3 between the upper surface M3 and the housing 12 in the normal direction of the upper surface M3. Smaller than height. Thereby, the thermal radiation sheet 43 can be made thin. Therefore, the thermal resistance between the circuit board 13 and the metal housing 14 is reduced. According to the reduction in thermal resistance, heat is efficiently transmitted from the circuit board 13 to the metal housing 14. Therefore, heat generated in the optical coupling unit 25 and the electronic component 19 can be efficiently radiated through the circuit board 13.

  Moreover, in the optical module 1, it becomes possible to arrange | position the electronic component 19 with large height in 1st clearance gap S3, and to arrange | position the electronic component 19 with low height in 2nd clearance gap S4. Therefore, the accommodation efficiency in the accommodation space K of the optical module 1 can be increased. Therefore, the optical module 1 can be reduced in size.

  The optical coupling unit 25 includes a ferrule 23 including a hole 23 a that holds the optical fiber 6. The housing 12 includes an introduction portion 14c for introducing the optical fiber 6 from the rear end. The height from the upper surface M3 to the hole 23c is substantially the same as the height from the upper surface M3 to the introduction portion 14c. Thereby, the optical fiber 6 introduced into the housing 12 is held by the optical coupling portion 25 without being bent in the height direction D3. Therefore, damage to the optical fiber 6 can be prevented.

  The connection part 13c carries the electronic component 19. Thereby, the mounting density of the electronic components 19 improves, and the circuit board 13 can be reduced in size.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  FIG. 7 shows an optical module 1A according to a modification. The optical module 1A is different from the optical module 1 in that the first substrate 13a is equipped with a waveform shaper 19a. In the optical module 1A, the first substrate 13a and the metal housing 14 are thermally connected to each other in the normal direction of the upper surface M3. Specifically, a heat radiation sheet 44 is disposed between the waveform shaper 19a and the cover 14a. The heat generated by the waveform shaper 19a is transmitted to the cover 14a via the heat dissipation sheet 44.

  In the optical module 1A, the second substrate 13b and the metal housing 14 are thermally connected to each other in the normal direction of the lower surface M4. The heat generated in the optical coupling unit 25 is transmitted to the base plate 14 b through the heat dissipation sheet 43. Thereby, the optical coupling part 25 and the waveform shaper 19a which are components with a large calorific value can be thermally separated.

  FIG. 8 shows an optical module 1B according to another modification. The optical module 1B is different from the optical module 1 in that the connecting portion 13d is a flexible printed board having flexibility. According to the connecting portion 13d, the offset height of the second substrate 13b in the height direction D3 can be easily adjusted.

  9 and 10 show an optical module 1C according to still another modification. The optical module 1C is different from the optical module 1 in that the optical fiber 6 has a bent portion 6b. The bent portion 6b is a portion where the optical fiber 6 is bent along a plane parallel to the upper surface M3, and is disposed in the first gap S3. According to the bending part 6b, it becomes possible to suppress the bending of the optical fiber 6 in the height direction D3. Therefore, the optical module 1C can be made thinner and shortened in the front-rear direction D1. Further, when changing the direction in which the tip of the optical fiber 6 faces, a space for accommodating the bent portion 6b can be secured.

DESCRIPTION OF SYMBOLS 1,1A, 1B, 1C ... Optical module, 2 ... Optical cable, 3 ... Connector module, 4 ... Optical fiber tape, 6 ... Optical fiber, 6b ... Bending part, 7 ... Inner tube, 8 ... Interposition layer, 9 ... Metal layer 11 ... jacket, 12 ... housing, 13 ... circuit board, 13a ... first board, 13b ... second board, 13c, 13d ... connecting part, 14 ... metal housing, 14a ... cover, 14b ... base plate, 14c DESCRIPTION OF SYMBOLS ... Introduction part, 15 ... Boot, 16 ... Resin housing, 17 ... Optical cable holding part, 19 ... Electronic component, 19a ... Wave shape shaper, 19d ... Electronic component, 21 ... Light emitting / receiving element (optical element), 22 ... Lens module, 23 ... Ferrule, 23a ... Hole, 25 ... Optical coupling part, 40 ... Electrical connector, 41 ... Main body, 41a ... Connection port insertion part, 41b ... Substrate insertion part, 42 ... Terminal, 4 a ... terminal contact portion, 42b ... substrate contact portion, 43, 44 ... heat dissipation sheet, A1, AX ... central axis, D1 ... front-back direction, D2 ... width direction, D3 ... height direction, K ... accommodation space, M1 ... top surface , M2 ... back surface, M3 ... top surface (first surface), M4 ... bottom surface (second surface), P ... pattern wiring, S1, S2, S5, S6, S7 ... gap, S3 ... first gap, S4 ... first 2 gaps.

Claims (9)

A circuit board on which an optical element, an optical coupling part, and an electronic component are mounted, an electrical connector connected to one end of the circuit board, an optical cable including an optical fiber connected to the optical coupling part, and the circuit board are accommodated An optical module comprising a housing,
The circuit board is
A first substrate to which the electrical connector is connected;
A second substrate on which the optical coupling unit is mounted;
A connecting portion for connecting the first substrate and the second substrate;
The second module is an optical module arranged so as to be offset with respect to the first substrate in a direction opposite to the first surface on which the optical coupling unit is arranged.   The optical module according to claim 1, wherein the first surface is mounted with an electronic component having a height in the normal direction of the first surface.   The optical module according to claim 1, wherein a heat radiating portion that thermally connects the circuit board and the housing is mounted on a second surface that is a surface on the back side of the first surface.   The height of the second gap between the second surface and the housing in the normal direction of the second surface is the first gap of the first gap between the first surface and the housing. The optical module according to claim 3, wherein the optical module is smaller than a height in a normal direction of the surface.   The first gap between the first surface and the housing has a portion where the optical fiber is bent along a plane parallel to the first surface. An optical module according to claim 1. The electronic component includes a waveform shaper,
The optical module according to claim 1, wherein the first substrate is mounted with the waveform shaper. The first substrate and the housing are thermally connected to each other in a normal direction of the first surface;
The optical module according to claim 6, wherein the second substrate and the housing are thermally connected to each other in a normal direction of a second surface that is a surface on the back side of the first surface.   The optical module according to any one of claims 1 to 7, wherein the connecting portion mounts the electronic component. The optical coupling unit includes a ferrule having a hole for holding the optical fiber,
The housing includes an introduction portion for introducing the optical fiber from a rear end;
The optical module according to any one of claims 1 to 8, wherein a height from the first surface to the hole substantially coincides with a height from the first surface to the introduction portion.

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