JP2002111110A - Optical communication module - Google Patents

Abstract

(57) [Problem] To provide an optical communication module capable of shortening a wire bonding length to a level that does not adversely affect high-frequency characteristics. SOLUTION: A first substrate provided with a light emitting element and a second substrate having a tapered tip at the tip and having a coplanar electrode structure data transmission line extending to the tip formed on the surface are provided. An optical communication module is shown. The second substrate is positioned and fixed relative to the first substrate such that the tapered tip is close to above the surface of the light emitting element, and the tapered tip is And the data transmission line and the light emitting element are connected by a wire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication module used in an optical communication system, and more particularly to a 2.4 Gbi optical communication module.
The present invention relates to an optical communication module equipped with a distributed feedback laser diode with an electro-absorption modulator used for a communication speed of t / s or more.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and speeding-up of optical communication systems, development of a communication light source module having a small size and high-speed performance is expected. FIG. 1 shows a plan view and a front view of a conventional light emitting device using a microstrip line as a data transmission line. Here, an example in which a light-emitting element with an electro-absorption modulator is used as a light-emitting element will be described.

A light emitting element with an electroabsorption modulator 11 is a high-speed light emitting element in which a modulator 12 and a semiconductor laser 13 are integrated. When the semiconductor laser 13 resonates, emitted light having a constant light intensity propagates along the waveguide in the direction of the broken line. The modulator 12 applies a high-frequency signal perpendicularly to the laser light waveguide to absorb and transmit light, thereby obtaining light intensity modulation.

[0004] The light emitting element 11 with an electroabsorption modulator formed on the Si submount 22 is provided with a terminating resistor 14 for impedance matching. A wiring substrate 23 in which wiring for applying a bias current to the semiconductor laser 13 is patterned on a ceramic substrate and plated on the back surface for solder bonding is also solder-bonded on the base component 21 as shown in the figure. Have been.

[0005] A data transmission line 24 is provided on the transmission line support member 25, and is connected to an electrode bonding pad of the modulator 12 by a wire 31. Here, the electrode bonding pads of the modulator 12 and the electrode bonding pads on the transmission line support member 25 are arranged at the same height so that the wires 31 are shortened.

[0006]

In order to improve the high-speed performance of the light emitting device, it is necessary to reduce the size of the electrode bonding pad of the light emitting device. However, to reduce the width of the light emitting device, there is a limit in the manufacturing process. is there. In other words, when mounting the light emitting element, wire bonding for wiring between the electrode pad of the light emitting element and the data transmission line is used, but this is an obstacle to reducing the width of the light emitting element.

That is, the length of the wire bonding is determined by the width of the element and the position of the electrode, and it is difficult to make the wiring short, and the inductance component has a bad influence on the high frequency characteristics. For this reason, the high speed performance of the light emitting element cannot be sufficiently achieved.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a wire bonding length having a high frequency characteristic regardless of the width of a light emitting element and the position of an electrode bonding pad. An object of the present invention is to provide an optical communication module that can be shortened to a level that does not adversely affect the optical communication module.

[0009]

Means for Solving the Problems The present invention (claim 1) provides:
A first substrate on which a light emitting element is provided, and a second substrate having a tapered tip at a surface and a data transmission line having a coplanar electrode structure extending to the tip formed on a surface thereof; The second substrate is mounted on the first substrate so that the tip of the shape is close to above the surface of the light emitting element.
An optical communication module, wherein the data transmission line and the light emitting element are connected to each other by a wire at the tapered tip.

The present invention (claim 2) provides the optical communication module according to claim 1, further comprising a third substrate provided with a wiring for supplying power to the light emitting element. .

According to a third aspect of the present invention, in the first aspect, the first substrate and the second substrate are provided on a base component having a step. Provide a module.

According to a fourth aspect of the present invention, in the third aspect, the base component is a conductive component, the data transmission line is provided with a ground line, and the data transmission line is provided on the second substrate. The optical communication module is characterized in that the ground wire is grounded to the base component by the provided through hole.

According to a fifth aspect of the present invention, in the third aspect, the base component is a conductive component, the data transmission line is provided with a ground line, and a side surface of the second substrate is provided. An optical communication module is provided, wherein the ground wire is grounded to the base component by metallization.

According to a sixth aspect of the present invention, in the first aspect, the light emitting device includes a semiconductor laser with an electro-absorption modulator and a terminating resistor for impedance matching. I will provide a.

The present invention (claim 7) provides the optical communication module according to claim 3, wherein the base component is CuW having high thermal conductivity.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Embodiment 1 FIGS. 1 (a), 1 (b) and 1 (c) are a plan view, a front view and a side view of an embodiment of an optical communication module according to the present invention. FIG. FIG. 1D is an enlarged view showing a portion of the optical communication module according to the embodiment of the present invention where light intensity modulation is performed. In this embodiment, an example in which a light-emitting element with an electro-absorption modulator is used as a light-emitting element will be described.

The light emitting device with an electro-absorption modulator 101 is a high-speed light emitting device in which a modulator 102 and a semiconductor laser 103 are integrated. When the semiconductor laser 103 resonates, the emitted light having a constant light intensity propagates along the waveguide in the direction of the broken line. The modulator 102 absorbs and transmits light by applying a high-frequency signal vertically to the laser optical waveguide, thereby obtaining light intensity modulation.

As a result, the spread of the optical spectrum of the emitted light is suppressed as compared with the conventional semiconductor laser direct modulation, and high-speed, large-capacity optical communication of several tens of gigabits / second is possible even over long distances.

The light emitting device of this embodiment is a base component 201
Is formed on. The base component 201 is made of a metal having high thermal conductivity, for example, CuW, and a conductive film that can be soldered and has excellent electric characteristics is provided on the entire surface. The conductive film can be formed by, for example, Au plating.

The base component 201 is provided with a step, and the Si submount 202 is soldered on the base component 201 as shown in the figure. A common example of a submount of a light emitting element is a bulk of Si having an entire surface plated with Au. Also in this case, the Si submount 202 is provided with Au plating on the entire surface of the Si, and the light emitting element 101 with the electroabsorption modulator and the terminating resistor 104 for impedance matching are provided.
This terminating resistor 104 for impedance matching is
It is composed of, for example, a resistance pattern of 50Ω and an electrode pattern formed on the surface of the ceramic substrate, and plating for solder bonding formed on the back surface of the ceramic substrate. In addition, a wiring substrate 203 made of a ceramic substrate in which wiring for applying a bias current to the semiconductor laser 103 is patterned on the front surface and plated on the back surface for solder bonding.
Are soldered onto the base component 201 as shown. The wiring substrate 203 is provided with wiring for supplying power to the light emitting element.

A data transmission line 204 having a coplanar electrode structure and having a characteristic impedance of, for example, 50Ω is provided on the transmission line support member 205 to form a microstrip line data transmission line structure. The transmission line support member 205 for supporting the data transmission line 204 is made of a ceramic substrate such as aluminum nitride or alumina, and has one end previously cut with a diamond saw or the like, and has a tapered portion 205a. The tapered portion 205a only needs to have an effect of sufficiently reducing the length of the wire, and does not necessarily need to have a completely acute angle as shown here. Also, the data transmission line 20
A pair of grounding lines 206 are provided on both sides of 4.
The ground line 206 is grounded to the base component by metallizing the side surface of the transmission line support member 205.

The transmission line supporting member 205 is a base component 2
No. 01 is accurately adhered to the support 201a. The alignment is performed by the transmission line support member 20.
5 protrudes above the electrode bonding pad of the modulator 102 and the data transmission line 20.
4 so as to be closest to the electrode bonding pad of the modulator 102 without contact. Therefore, the electrode bonding pad of the modulator 102 and the data transmission line 204 can be connected with an extremely short wire 301.

In general, it is necessary to reduce the bonding pad and the element capacitance in order to enable the light emitting element to operate at high speed. However, the width of the element is limited both thermally and structurally. Inductance becomes a problem. However, with such a structure, the problem of inductance due to wires can be substantially avoided.

As shown in FIG. 1D, the bonding pad 102a of the modulator 102 is provided across the laser light waveguide LP. However, performing wire bonding requires the laser light waveguide LP
Since it causes mechanical and thermal damage, it cannot be performed immediately above the laser light waveguide LP. Therefore, the actual wire bonding is performed at positions on both sides of the laser light guide LP, avoiding the upper part.

Conventionally, the wire length between the light emitting element and the transmission line was limited to about 300 μm in width of the light emitting element and required about 500 μm. According to the present invention, the transmission line can be arranged so as to cover the light emitting element. In addition, since the transmission line is tapered, the bonding length can be reduced without being restricted by the wire length due to the thickness of the transmission line.

FIG. 3 shows a simple equivalent circuit of this embodiment.
L1 is the inductance of the wire 301 between the transmission line and the light emitting element, and L2 is the wire 30 between the light emitting element and the terminating resistor.
2, L3 is the inductance of the wire 303 between the terminating resistor and the ground, and Rohm is the modulator 10
The internal resistance 2 and Cpn is the capacitance of the modulator 102.

In the conventional example, the length of the wire between the transmission line and the light emitting element needs to be about 500 μm. In this case, the inductance of the wire is 0.5 nH. In the embodiment according to the present invention, the wire length can be reduced to about 100 μm, and the inductance 0 due to the wire can be reduced to 0.1 nH. In addition to the above values, other values are L2 = 0.5 nH, L3 = 0.0
5nH, R = 50Ω, Rohm = 10Ω, Cpn = 0.
The calculation was performed using the above equivalent circuit using a common numerical value of 4 pF. FIG. 4 shows a calculation result of the conventional example, and FIG. 3 shows a calculation result of the present invention. It can be seen that the frequency response characteristic of 16.4 GHz is improved to 18 GHz or more according to the present invention in the conventional example.

FIG. 5 is a plan view and a front view showing a modification of the above embodiment of the light emitting device according to the present invention. here,
Through hole 20 opened in transmission line support member 205
The ground wire 206 is connected to the support base 201 by 5a, so that the grounding is more effectively performed.

In the embodiment, the present invention has been described based on the light emitting element with an electroabsorption modulator. However, the light emitting element may be a semiconductor laser which performs direct modulation, and the terminating resistor is not necessarily located on the submount. It is not a must.

[0030]

According to the present invention, the thickness of the data transmission line can be eliminated and the wire bonding length can be reduced by forming the data transmission line with a tapered shape on the light emitting element side using a coplanar electrode structure. This makes it possible to improve high-frequency characteristics.

[Brief description of the drawings]

FIG. 1 shows a light emitting device with an electroabsorption modulator according to the present invention, wherein (a) is a plan view, (b) is a front view, (c) is a side view, and (d) is light intensity modulated. FIG.

FIG. 2 is a simple equivalent circuit of a light emitting device with an electroabsorption modulator according to the present invention.

FIG. 3 is a calculation result of a frequency response characteristic of the equivalent circuit of FIG. 2 for the light emitting device with an electroabsorption modulator according to the present invention.

4 is a calculation result of a frequency response characteristic of the equivalent circuit of FIG. 2 for a light emitting element with an electro-absorption modulator according to a conventional example.

FIG. 5 is a view showing a light emitting device with an electroabsorption modulator according to the present invention.

FIG. 6 is a view showing a conventional light emitting device with an electroabsorption modulator.

[Explanation of symbols]

101 Light Emitting Element with Electroabsorption Modulator 102 Modulator Portion of Light Emitting Element with Electroabsorption Modulator 103 Laser Diode Portion of Light Emitting Element with Electroabsorption Modulator 104 Terminating Resistance 21, 201 Base Component 22, 202 Submount 23, 203 Wiring board 24, 204 Coplanar type data transmission line 301, 302, 303 Bonding wire 205 Transmission line support member

Claims (7)

[Claims] 1. A first substrate provided with a light emitting element, and a second substrate having a tapered tip end and a coplanar electrode structure data transmission line formed on the surface extending to the tip end. The second substrate is positioned and fixed relative to the first substrate such that the tip of the tapered shape approaches above the surface of the light emitting element, and the second substrate is fixed to the first substrate. An optical communication module, wherein the data transmission line and the light emitting element are connected by a wire at a tip. 2. The optical communication module according to claim 1, further comprising a third substrate provided with a wiring for supplying electric power to said light emitting element. 3. The optical communication module according to claim 1, wherein the first substrate and the second substrate are provided on a base component having a step. 4. The base component is a conductive component,
4. The data transmission line according to claim 3, wherein a ground line is provided on the data transmission line, and the ground line is grounded to the base component by a through hole provided in the second substrate. Optical communication module. 5. The base component is a conductive component,
4. The data transmission line is provided with a ground line, and the ground line is grounded to the base component by side metallization of the second substrate.
An optical communication module according to item 1. 6. The optical communication module according to claim 1, wherein the light emitting element includes a semiconductor laser with an electro-absorption modulator and a terminating resistor for impedance matching. 7. The optical communication module according to claim 3, wherein the base component is made of CuW having high thermal conductivity.