KR20140072793A - Multi-channel transmitter Optical Sub Assembly - Google Patents

Abstract

The present invention relates to a multi-channel optical transmission sub-assembly. The multi-channel optical transmission sub-assembly includes: a stem including a sub-mount; a plurality of light sources mounted on the sub-mount; a common ground pad which is formed on the sub-mount and uniformly connected to ground electrodes of the light sources; a common lead pin which is installed on the stem and connected to the common ground pad; and a thermistor which is mounted on the sub-mount with the light sources.

Description

[0001] The present invention relates to a multi-channel optical transmission sub-assembly,

The present invention relates to a multi-channel optical transmission subassembly having a structure in which a plurality of light sources are mounted on one stem.

A WDM-based fiber to the home (FTTH), that is, a WDM-PON (passive optical network) is a method in which communication is performed between a central office and a subscriber using wavelengths set for each subscriber. This scheme is independent of the time division multiplexing (TDM) scheme and can provide independent and large-capacity communication services for each subscriber, has superior security, and has an advantage of modulating and demodulating the light source for only one subscriber.

An essential component for constructing such an optical communication system is a transmitter optical sub-assembly (TOSA). In general, since a single light source is mounted on a single package, TOSA is required for the number of channels in order to construct a multi-channel system. As a result, there is a disadvantage that the system configuration cost and the consumption space are large. This is the case with the conventional TOSA using a Distributed Feedback Laser Diode (DFB-LD) or a Fabry-Perot Laser Diode (FP-LD).

In order to solve these drawbacks, there has been proposed a hybrid optical transceiver module of Korean Patent Registration No. 10-0825728. According to the example, the hybrid optical transceiver module includes a first package of a Transmitter Optical Sub-Assembly (TOSA) structure and a second package of a Planar Lightwave Circuit (PLC) .

The first package includes a laser diode for outputting an optical signal for transmission. The second package includes a photodiode for receiving an optical signal for reception input through an optical fiber, an optical waveguide for transmitting a transmission optical signal emitted from the first package to the optical fiber, And a wavelength division multiplexer (WDM) for dividing a high-power optical signal for transmission and a reception optical signal.

Although the optical transceiver module can provide a multi-channel light source in one package, the use of a PLC is required, which may cause a disadvantage that the optical transceiver module is bulky. Also, the optical transceiver module is required to multiplex the optical waveguide using one optical waveguide using a wavelength divider, which may cause a large loss.

On the other hand, in order to package a multi-light source into one TOSA, the number of pins for current injection and temperature control must be sufficient. For example, to package a 4-channel light source into a single TOSA, there are eight pins for current injection (eight anode pins and two cathode pins per channel), a TEC (Thermo- Two pins for temperature control using an electric cooler, and two pins for temperature monitoring. A total of 12 pins are required.

In this case, since the number of pins is large, it is common to use a butterfly type package in order to package the pins in one TOSA. As a result, the volume of the package becomes large. Further, when a laser diode that outputs light vertically to the package is used, packaging is difficult. As another example, in the case of a QSFP (Quad Small Form Factor Pluggable) optical module, since signal lines must be independently allocated, they can not be packaged in a TO-stem (transistor outline-stem) structure.

In order to reduce the volume of the multi-channel light source package, a TO-can type package can be used, but in this case, there is a drawback that the number of the pins is insufficient. In order to overcome such disadvantages, a common pin can be designated. If a commonly used pin corresponds to a signal line, crosstalk may occur.

The object of the present invention is to provide a multi-channel optical transmission system capable of reducing crosstalk in a volume-reduced package form and integrating light sources and lead pins in a volume-reduced stem even when mounting a plurality of light sources in one stem Subassembly.

According to an aspect of the present invention, there is provided a multi-channel optical transmission subassembly including: a stem having a submount; a plurality of light sources mounted on the submount; A common lead pad provided on the stem and connected to the common ground pad, and a thermistor mounted on the sub mount together with the light sources.

According to the present invention, it is possible to reduce thermal and electrical crosstalk in a volume-reduced package form. In addition, according to the present invention, even when a plurality of light sources are mounted on one stem, the light sources and the lead pins can be integrated on the reduced-volume stem.

1 is a block diagram of a multi-channel optical transmission subassembly in accordance with an embodiment of the present invention;
FIG. 2 is a graph comparing an example in which a light source and a thermistor are mounted on a single submount, and a wavelength variation in an A light source in an example mounted on dual submounts. FIG.
Fig. 3 is a view showing another example in Fig. 1 in which a common ground pad is connected to light sources;
Fig. 4 is a view showing a wiring structure for a common ground pad in Fig. 1; Fig.
Fig. 5 is a view showing a wiring structure for a common ground pad according to another example in Fig.
Fig. 6 is a view for explaining the area setting of the common ground pad in Fig. 5; Fig.
FIG. 7 is a cross-sectional view schematically showing the structure of light sources in FIG. 5; FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a multi-channel optical transmission subassembly according to an embodiment of the present invention.

Referring to FIG. 1, a multi-channel optical transmission subassembly 100 includes a stem 110, a plurality of light sources 120, a common ground pad 130, a common lead pin 140, a thermistor , 150).

The stem 110 functions as a base member in the multi-channel optical transmission subassembly 100. The stem 110 may comprise a TO-stem. The stem 110 may be formed in a cylindrical shape of a metal. The stem 110 may include a submount 112. The submount 112 may be mounted on the mounting surface 111 corresponding to one of the circular surfaces of the stem 110.

The light sources 120 are mounted on the submount 114. The light sources 120 may be mounted on the submount 112 by a technique such as flip chip bonding or die bonding. The light sources 120 are arranged in a row and can output optical signals of different wavelengths. Accordingly, the multi-channel optical transmission subassembly 100 may have the same number of multi-channels as the number of the light sources 120. The light sources 120 may be composed of a semiconductor laser or the like. Each of the light sources 120 may include an anode electrode and a cathode electrode. When the anode electrode controls the amount of current injected into the light source 120, the cathode electrode may be used as the ground electrode. Alternatively, when the cathode electrode controls the amount of current injected into the light source 120, the anode electrode may be used as the ground electrode.

A common ground pad 130 is formed in the submount 112. The common ground pad 130 may be disposed adjacent to the ground electrodes of the light sources 120. The common ground pads 130 are connected in common to the ground electrodes of the light sources 120.

The common lead pin 140 is installed in the stem 110. The common lead pin 140 is inserted into a through hole formed in the stem 110 in a direction perpendicular to the mounting surface 111 of the stem 110 and protruded to a surface opposite to the mounting surface 111 of the stem 110 . A dielectric may be filled in the through hole to surround the common lead pins 140. The common lead pins 140 may be made of a conductive metal material. The common lead pins 140 are connected to the common ground pad 130. The common lead pin 140 can be connected to the common ground pad 130 by a wiring method using wires or the like.

The thermistor 150 is mounted on the submount 112 along with the light sources 120. The thermistor 150 is for sensing the temperature of the light sources 120 when the light sources 120 are driven. The temperature information sensed by the thermistor 150 is provided to an external control unit and the external control unit controls the driving of the thermal electric cooler 160 based on the sensed temperature information so that the temperature of the light sources 120 becomes a set value Do not exceed.

One electrode of the thermistor 150 may be commonly connected to the common ground pad 130 together with the ground electrodes of the light sources 120. Therefore, the number of the lead pins can be reduced by one compared with the case where two lead pins are provided so as to be connected to both electrodes of the thermistor 150. As a result, the stem 110 may have the effect of reducing the installation space for the thermistor lead pin. The thermistor 150 may be mounted on the submount 112 by being separated from the common ground pad 130 and one electrode may be connected to the common lead pin 140 by wiring or the like.

The ground electrodes of the light sources 120 may be connected to the common ground pad 130 by wiring and flip chip bonding. When a current is injected into the anode electrodes of the light sources 120, a return current flows through the ground path. If the ground electrodes of the light sources 120 are connected to the common ground pad 130 by wiring, the area of the path through which the return current flows may be small, and electric crosstalk may occur. Therefore, in order to reduce the electrical crosstalk, the ground electrodes of the light sources 120 may be connected to the common ground pad 130 by using only flip chip bonding without using wiring as shown in FIG.

According to the multi-channel optical transmission subassembly 100 having the above-described configuration, the light sources 120 and the thermistor 150 are mounted together on one submount 112. [ If the light source 120 and the thermistor 150 are mounted on the two separate first and second submounts, the temperature is monitored by the thermistor 150 and the portion where the heat is generated by the light sources 120, A large difference may occur between the actual temperature at the first submount and the measured temperature at the second submount.

In the semiconductor laser used as the light source 120, when the injection current is increased, a part is reduced to light and a part generates heat. The generated heat does not cause a big problem in a single light source composed of one channel, but in a multi-channel multi-light source, the operating characteristic is changed by changing the temperature of the adjacent channel. That is, if the operating characteristics are changed by changing the current of any one of the light sources, the operation characteristics of the ambient light sources are unintentionally changed due to the heat generated by the changed current. As a result, thermal crosstalk can be caused to a large extent.

However, when the light sources 120 and the thermistor 150 are mounted together on one submount 112 as in the present embodiment, even when the same operating conditions as those of the specific light source are changed, the operating wavelengths of the ambient light sources, And the like can be remarkably reduced. Thus, thermal crosstalk that one light source affects another light source can be reduced.

This effect will be described with reference to FIG. FIG. 2 shows a case where a light source and a thermistor are mounted on a single sub-mount and a light source and a thermistor are mounted on a separate dual sub-mount, respectively. FIG. 5 is a graph showing the wavelength change of the A light source according to the injection current change. FIG. As shown in Fig. 2, in the case where the light source and the thermistor are mounted on the single sub mount, the wavelength change of the A light source in the areas indicated by circles is 10 times As shown in Fig.

The ground electrodes of the light sources 120 are commonly connected to one common ground pad 130 and the common ground pads 130 are connected to one common And is connected to the lead pin 140. That is, one common lead pin 140 is commonly used for the ground electrodes of the light sources 120 via the common ground pad 130.

Accordingly, it is possible to reduce the number of the lead pins for ground electrodes, as compared with the case where the number of ground electrode lead pins is the same as the number of the ground electrodes to be connected independently of the ground electrodes of the light sources 120. For example, when the number of the light sources 120 is four, the number of the lead pins for ground electrodes can be reduced from four to one. Since one electrode of the thermistor 150 is commonly connected to the common ground pad 130 together with the ground electrodes of the light sources 120, the number of thermistor lead pins can be reduced from two to one. Therefore, since the stem 110 can reduce the installation space for the ground electrode lead pin and the thermistor lead pin, it is possible to integrate the light sources 120 and the common lead pin 140 in the stem 110 having a small volume There is an advantage. As a result, miniaturization of the package is possible.

On the other hand, the thermoelectric cooler 160 may be mounted on the mounting surface 111 of the stem 110. The thermoelectric cooler 160 may be disposed between the mounting surface 111 of the stem 110 and the submount 112. The thermoelectric cooler 160 is for cooling the light sources 120.

4 is a diagram showing a wiring structure for the common ground pad 130. As shown in FIG.

4, the first wires 171 reduce crosstalk by wiring two or more common ground pads 130 to the common lead pin 140. As shown in Fig. That is, the current injected into the anode of the light source 120 passes through the common ground pad 130 to the common lead pin 140. At this time, if the common ground pad 130 and the common lead pin 140 are wired by a single first wire 171, the path of the return current is small and electric crosstalk is likely to occur. However, if the common ground pad 130 and the common lead pin 140 are wired by the two or more first wires 171, the path of the return current is expanded, so that the crosstalk can be reduced.

At least one second wire 172 connects the common ground pad 130 to the stem 110 and at least one third wire 173 connects the common lead pin 140 to the stem 110 at least It is also possible to wire more than one. Therefore, since the return current path is further secured, the effect of reducing the crosstalk can be further enhanced.

As shown in FIG. 5, the common ground pad 230 may be formed such that portions connected to the ground electrodes of the light sources 120 are separated from each other. Therefore, the common path to the return current used by the light sources 120 can be minimized, and the crosstalk can be reduced. That is, the common path exists only in one common lead pin 140.

The first wires 271 may be connected to the common ground pads 230, which are separated from each other, to the common lead pins 140. In addition, the second wires 272 can wire the common ground pads 230 separated from each other to the stem 110.

It is also possible that the common ground pads 230 are separated from the ground electrodes of the light sources 120 only by two or more, without being separated from each other. For example, when there are four ground electrodes of the light sources 120, the common ground pad may be divided into a portion connected to two ground electrodes of the four ground electrodes and a portion connected to the remaining two ground electrodes. Alternatively, the common ground pad may be divided into a portion connected to three ground electrodes among the four ground electrodes and a portion connected to the remaining one ground electrode.

As shown in FIG. 6, in order to make two or more wirings on one common ground pad 230, the area of the common ground pad 230 must be sufficiently large. When a solder ball 180 is used for wiring, the area of the common ground pad 230 should be at least twice as large as the cross-sectional area of the solder ball 180. For example, when the common ground pad 230 is rectangular, the length W of one side of the common ground pad 230 should be longer than the diameter? Of the solder ball 180, The length (L) should be at least twice the diameter (Φ) of the solder ball.

7 is a cross-sectional view schematically showing the structure of the light sources 120. As shown in FIG. Referring to FIG. 6, the light sources 120 may be formed of a semiconductor laser diode array. In the semiconductor laser diode array, a plurality of laser emitting units 121 are arranged in a line. And the laser emitting units 121 function as the light sources 120, respectively. The laser emitting units 121 are formed by stacking an active layer 123 and a conductive layer 124 on a substrate 122. Conductive layer 124 may include N- layer 124a and P-layer 124b. The N-layer 124a may be disposed closer to the substrate 122 than the P-layer 124b with the active layer 123 therebetween.

The laser emitting units 121 are formed in such a manner that the boundary portion is removed to the substrate 122. Therefore, since the N-layer 124a and the P-layer 124b can be physically separated between the laser emitting portions 121, the crosstalk can be reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation and that those skilled in the art will recognize that various modifications and equivalent arrangements may be made therein. It will be possible. Accordingly, the true scope of protection of the present invention should be determined only by the appended claims.

110 .. stem 112 .. submount
120 .. light source 130 .. common ground pad
140 .. Common Lead Pin 150 .. Thermistor

Claims (10)

A stem with a submount;
A plurality of light sources mounted on the submount;
A common ground pad formed on the submount and commonly connected to the ground electrodes of the light sources;
A common lead pin installed on the stem and connected to the common ground pad; And
A thermistor mounted on the submount with the light sources;
/ RTI > optical transmission subassembly. The method according to claim 1,
And one terminal of the thermistor is connected on the common ground pad. The method according to claim 1,
And first wires for wiring the common ground pad to at least two of the common lead pins. The method of claim 3,
And a second wire for routing the common ground pad to at least one or more of the stems. 5. The method of claim 4,
And a third wire for routing the common lead pin to at least one or more of the stems. The method according to claim 1,
Wherein the common ground pad is divided into at least two groups of parts connected to the ground electrodes of the light sources. The method according to claim 6,
Wherein the common ground pad is divided into portions connected to the ground electrodes of the light sources. The method according to claim 6,
And first wires for separately routing the separated portions of the common ground pad to the common lead pins. 9. The method of claim 8,
And second wires that respectively wire isolated portions of the common ground pad to the stem. ≪ Desc / Clms Page number 15 > The method according to claim 1,
Wherein the light sources comprise a semiconductor laser diode array;
Wherein the semiconductor laser diode array has a plurality of laser emitting units arranged in a row and stacking an active layer and a conductive layer on a substrate, and the boundary portions of the laser emitting units are removed to the substrate. Transmitting subassembly.

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