JP2010287671A - Optical transmission module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission module in which the power consumption of an electronic cooling element is decreased by decreasing an amount of inflow of heat generated by impedance-matching resistance provided in a transmission line on a wiring board for external electric connection to the electronic cooling element. <P>SOLUTION: The optical transmission module 1 includes: a Peltier module 16 mounted with an LD (Laser Diode) to control the temperature adjustment of the LD; and the wiring board 13f arranged at a position physically apart from the Peltier module 16 and provided with the impedance-matching resistance 21 and a transmission line 13h for feed power to the LD where the resistance 21 is electrically connected to the LD through a metal wire W. The wiring board 13f has a heat dissipation pattern 13j, and the heat dissipation pattern 13j is thermally coupled to the resistance 21 by a heat conductive member 22, to dissipate heat generated by the resistance 21 through the heat dissipation pattern 13j. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical transmission module having a light emitting device to which a high frequency electrical signal is input.

  An optical transmission module (particularly for high speed) used for optical communication includes, for example, a light emitting element such as an LD (LD: Laser Diode) driven by an integrated circuit (IC) provided outside the module, And an electronic cooling element such as a Peltier module for the purpose of temperature control of the light emitting element. With this Peltier module, it is possible to prevent the influence of temperature on the electro-optical output characteristics of the light emitting element. The light emitting element is mounted on the Peltier module via a submount, and a wiring pattern serving as a transmission line for the light emitting element is formed on the submount.

  In optical communication, an impedance matching resistor is provided in the transmission line between the light emitting element and the IC in order to suppress the reflection loss of the electric signal in the transmission line. In consideration of the transmission characteristics of the optical transmission module, the impedance matching resistor is preferably provided in the immediate vicinity of the light emitting element, and is often provided in a transmission line formed in a submount on the Peltier module. However, in this embodiment, since Joule heat generated by the impedance matching resistor flows into the Peltier module via the submount, a large amount of power is required for the Peltier module.

On the other hand, in the optical transmission module disclosed in Patent Document 1, low power consumption is achieved with the configuration shown in FIG.
The optical transmission module of FIG. 8 uses the following wiring substrate 102 for the casing 100 for electrical connection between an element such as a Peltier module 101 or a light emitting element mounted inside the casing 100 and an element outside the casing 100. To make up part of. The wiring board 102 has a portion where the lead pin 103 is attached exposed to the outside of the housing 100, and a portion where the transmission line 102 a serving as a signal input line to the light emitting element is provided is located inside the housing 100. It is arranged at a position physically separated from the Peltier module 101.

  In the illustrated optical transmission module, the position where the impedance matching resistor 102b is provided is not in the transmission line 104a formed in the submount 104 on the Peltier module 101, but in the transmission line 102a on the wiring board 102 and emits light. The position is close to the element. With this configuration, heat generated in the impedance matching resistor 102b can be prevented from flowing into the Peltier module 101, and power consumption can be suppressed.

JP-A-6-318863

  However, even in the configuration of FIG. 8, Joule heat generated in the impedance matching resistor 102b on the wiring board 102 causes the transmission line 102a of the wiring board 102 and the transmission line 104a of the submount 104 on which the light emitting element is mounted. Is transmitted to the submount 104 via the metal wire W that electrically connects to the Peltier module 101.

  In view of the above circumstances, the present invention reduces the amount of heat flowing into the electronic cooling element generated by the impedance matching resistor provided in the transmission line on the wiring board for electrical connection with the outside, An object of the present invention is to provide an optical transmission module that reduces power consumption in an electronic cooling element.

  In order to solve the above-described problems, the optical transmission module of the present invention includes a cooling element on which a light-emitting element is mounted and performs temperature adjustment of the light-emitting element, and the cooling element is disposed at a position physically separated from the light-emitting element. A wiring board provided with a resistance for impedance matching and a transmission line, and the resistor is electrically connected to the light-emitting element through a metal wire. It has a pattern, and the heat dissipation pattern and the resistor are thermally coupled by a heat conducting member, and heat generated by the resistor is radiated through the heat dissipation pattern.

  The heat conducting member may be a ribbon wire. Further, it is preferable that an inductor element is provided on the heat radiation pattern, and the resistor is thermally and electrically connected via a heat conducting member. The transmission line may be for differential signals. The resistance for impedance matching may be a thin film resistor or a chip-type resistance element.

  According to the optical transmission module of the present invention, the heat radiation pattern is provided on the wiring board, and the impedance matching resistor on the wiring board and the heat radiation pattern are thermally coupled. Since heat can be released to the outside through the heat radiation pattern, heat inflow to the electronic cooling element can be reduced, and power consumption in the electronic cooling element can be reduced.

It is a figure which shows an example of the optical transmission module of this invention. It is a figure which shows the state before mounting various elements of the optical transmission module of FIG. It is a figure which shows the state after mounting various elements of the optical transmission module of FIG. It is a figure explaining the characteristic part of the optical transmission module of FIG. It is a figure explaining the other example of the optical transmission module of this invention. It is a figure explaining the other example of the optical transmission module of this invention. It is a figure explaining the other example of the optical transmission module of this invention. It is a figure explaining the conventional optical transmission module.

The optical transmission module of the present invention will be described below with reference to the drawings. In the description of the drawings, similar parts are denoted by the same reference numerals, and redundant description is omitted.
First, the outline of the optical transmission module of the present invention will be described with reference to FIGS.
For example, as shown in FIG. 1, the optical transmission module of the present invention includes an optical transmission unit 10 that converts a high-frequency electric signal input from the outside into an optical signal and outputs the optical signal, and a housing 11 of the optical transmission unit 10. And an optical coupling portion 30 into which a ferrule attached to the front end of the optical fiber cable is inserted. The optical coupling unit 30 is aligned and fixed with respect to the optical transmission unit 10, and the light emitted from the LD in the optical transmission unit 10 is coupled to the optical fiber of the inserted ferrule. .

  The optical transmitter 10 includes a housing 11 having a rectangular parallelepiped shape, and lead pins 15a and 15b attached to the side surface 13b and the rear portion 13c of the housing 11, respectively. The lead pin 15b is used for the purpose of giving a high frequency modulation signal to the LD inside the housing 11, and the lead pin 15a is used for supplying power to the electronic cooling element, outputting a signal from the temperature measuring element, and monitoring the optical output. This is provided for input / output of a DC signal or a low-frequency signal, such as signal output from the light receiving element and supply of drive current to the LD.

  As shown in FIGS. 2 and 3, the housing 11 includes a bottom plate 12 made of a material having a high thermal conductivity such as CuW, a side wall 13 that is airtightly joined to an edge of the bottom plate 12 by brazing, and the bottom plate 12. And a lid 14 (see FIG. 1) that closes the space formed by the side wall 13 from above.

  On the bottom plate 12, a Peltier module 16 as an electronic cooling element is mounted. The side wall 13 includes a metal plate 13d made of a metal such as kovar, which forms the front surface 13a, and a multilayer ceramic portion 13e made of an alumina-based material, which forms a frame to which the metal plate 13d is attached. The multilayer ceramic portion 13e is obtained by superposing a ceramic layer 13g on a multilayer ceramic substrate 13f. The multilayer ceramic substrate 13f is a wiring substrate in which a metal layer including a wiring pattern is formed on the surface of a plurality of ceramic layers, and electrically connects various components in the housing 11 and the lead pins 15a and 15b. Is for. Hereinafter, the multilayer ceramic substrate 13f is referred to as a wiring substrate 13f. As will be described later, a transmission line for signal input to the LD is formed on the wiring board 13f, and an impedance matching resistor is provided in the transmission line.

Further, in the housing 11, in addition to the above-described Peltier module 16, an LD 17 as a light emitting element, a lens member 18 for making collimated light the emitted light from the LD 17, and an optical output from the LD 17 are monitored. And a semiconductor light receiving element (PD: Photo Diode) 19.
The LD 17 is of a DFB (Distributed Feedback) type, for example, and is mounted on the submount 20 attached to the Peltier module 16. The lens member 18 is directly mounted on the Peltier module 16, and the PD 19 is mounted on the wiring board 13f so as to receive the rear light from the LD 17.

The submount 20 on which the LD 17 is mounted includes, for example, an insulating layer made of AlN, which is an insulating material having good thermal conductivity, and a metal layer including a wiring pattern such as a transmission line for signal input to the LD 17. . In addition to the LD 17, a temperature measuring element for measuring the temperature of the LD 17 is mounted on the submount 20.
The LD 17 on the submount 20 is electrically connected to the transmission line on the wiring board 13f by a bonding wire W spanned from the transmission line on the submount 20.

  With the configuration as described above, the optical transmission module 1 can convert an electrical signal input via the lead pin 15b into a signal light by the LD 17 and output it as collimated light by the lens member 18, The optical output can be monitored by the PD 19 for feedback control of the optical output. Further, in order to obtain a desired light output characteristic, the temperature of the LD 17 can be controlled by the Peltier module 16.

  Then, the characteristic part of this invention is demonstrated using FIG. 4 (A) is a top view showing the inside of the optical transmission module 1 with the lid 14 of FIG. 1 removed, and FIG. 4 (B) is an enlarged view of the main part of FIG. 4 (A). In order to clearly show the part related to the characteristic part of the present invention, illustration of other parts is omitted as appropriate.

  In the optical transmission module 1, as shown in FIG. 4, transmission lines 13h and 20a serving as signal input lines to the LD are formed on the wiring board 13f and the submount 20 on the Peltier module. 13j and 20a are electrically connected through a metal wire W. The impedance matching resistor 21 is provided at a position close to the LD of the transmission line 13h on the wiring board 13f provided at a position physically separated from the Peltier module 16.

On the wiring board 13f, a heat radiation pattern 13j made of a metal thin film such as Au is formed in the vicinity of the resistor 21, and the heat radiation pattern 13j and the transmission line 13h are coupled by a heat conducting member 22 ( By connecting), the heat radiation pattern 13j and the resistor 21 are thermally coupled.
Therefore, in the present optical transmission module 1, the heat generated by the impedance matching resistor 21 flows from the transmission line on the wiring board 31 f into the heat radiation pattern 13 j, so that the amount of heat flowing into the Peltier module 16 can be reduced. it can.

  Further, since the bottom plate 12 (see FIG. 3) of the housing 11 is in contact with the radiator, the bottom surface of the wiring board 13f in contact with the bottom plate 12 is formed with a solid metal pattern, and the top surface (surface opposite to the bottom surface). It is preferable to thermally connect the heat radiation pattern 13j provided to the solid metal pattern with a thermal via. Thereby, the heat generated by the resistor 21 can be transmitted to the radiator via the transmission line 13h, the heat conducting member 22, the heat radiation pattern 13j, the above-described thermal via, the solid metal pattern, and the bottom plate 12 of the housing 11. The amount of heat flowing into the Peltier module can be further reduced.

In the example of FIG. 4, the metal wire 22 is used as the heat conducting member 22, but a ribbon wire 23 may be used as shown in FIG. 5.
Since the bottom plate 12 of the housing is set to the ground potential, as described above, when heat is radiated from the heat radiation pattern 13j via the bottom plate 12 or the like, the potential of the heat radiation pattern 13j becomes the ground potential. In this case, when a good electrical conductor such as the metal wire 22 or the ribbon wire 23 is used as the heat conducting member, the heat radiation pattern 13j and the transmission line 13h are, for example, thermally coupled while ensuring electrical insulation. (Connected). Instead, as shown in FIG. 6, an inductor element 24 such as a ferrite bead inductor (FBI) is mounted on the heat radiation pattern 13j, and the FBI 24 and the transmission line 13h on the wiring board 13f are connected by a metal wire 22. The resistor 21 and the heat radiation pattern 13j may be thermally coupled via the inductor element 24 (and the metal wire 22). As a result, heat inflow of Joule heat generated by the resistor 21 to the Peltier module 16 is suppressed, and the inductor element 24 functions as a resistance component in a high frequency region exceeding 10 GHz, so that transmission characteristics can be improved.

In the above description, it is assumed that a single-ended signal is input. However, in the present invention, as shown in FIG. 7, transmission lines 13h ′, 20a designed with a differential 50Ω between a wiring board 13f ′ and a submount 20 ′. It can also be applied to the case where 'is formed and a differential signal is input. Of course, in this case, the impedance matching resistor 21 and the heat radiation pattern 13j are provided such that their positions with respect to the transmission line 13h ′ are symmetrical.
In the drawings used in the above description, a thin film resistor is used as the resistor 21, but the present invention can also be applied to impedance matching using a chip-type resistor.

DESCRIPTION OF SYMBOLS 1 ... Optical transmission module, 10 ... Optical transmission part, 11 ... Housing | casing, 12 ... Bottom plate, 13 ... Side wall, 13a ... Front surface, 13b ... Side surface, 13c ... Rear part, 13d ... Metal plate, 13e ... Multilayer ceramic part, 13f ... Multilayer ceramic substrate (wiring substrate), 13g ... ceramic layer, 13h ... transmission line, 13j ... radiation pattern, 14 ... lid, 15a, 15b ... lead pin, 16 ... Peltier module, 17 ... LD, 18 ... lens member, 19 ... PD, 20 ... submount, 20a ... transmission line, 21 ... resistance, 22 ... heat conduction member (metal wire), 23 ... ribbon wire, 24 ... inductor element, 30 ... optical coupling part.

Claims (6)

A cooling element on which the light emitting element is mounted and adjusting the temperature of the light emitting element, and the cooling element is disposed at a physically separated position, and an impedance matching resistor and a transmission line for supplying power to the light emitting element are provided. An optical transmission module, wherein the resistor is electrically connected to the light emitting element via a metal wire,
The wiring board has a heat dissipation pattern,
An optical transmission module, wherein the heat radiation pattern and the resistor are thermally coupled by a heat conducting member, and heat generated by the resistor is radiated through the heat radiation pattern.   The optical transmission module according to claim 1, wherein the heat conducting member is a ribbon wire.   3. The optical transmission module according to claim 1, wherein an inductor element is provided on the heat radiation pattern, and is thermally and electrically connected to the resistor via the heat conducting member.   The optical transmission module according to claim 1, wherein the transmission line is for a differential signal.   The optical transmission module according to claim 1, wherein the resistor is a thin film resistor.   The optical transmission module according to claim 1, wherein the resistor is a chip-type resistance element.

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