JP2019101346A - Optical transmission module and optical module - Google Patents

Abstract

To provide an optical transmission module which realizes reduction in the size and increase in the density of equipment while suppressing noise.SOLUTION: The optical transmission module includes: a light source (3) for generating a continuous light; at least one modulator (2) for modulating the continuous light; a pair of direct-current lines (21, 22) connected to the light source, the pair of direct-current lines flowing a direct current to be supplied to the light source; and a pair of modulated-current lines (23, 24) connected to the modulator, the pair of modulated-current lines applying a modulation signal to be supplied to the modulator. In the optical transmission module, at least one of the direct-current lines of the pair or at least one of the modulated-current line of the pair intersect with each other at least once.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical transmission module and an optical module incorporating the same.

  As a signal source of optical communication, a semiconductor light modulator integrated type light emitting element in which an optical modulator and a semiconductor laser element are integrated is used. A semiconductor light modulator integrated light emitting element is mounted on a chip carrier and used. The chip carrier is provided with a modulation current line for applying a high frequency signal to the optical modulator and a DC current line for passing a current to the semiconductor laser element.

  Patent Document 1 discloses a differential transmission circuit in which a pair of transmission line conductors constituting a differential transmission line cross each other in order to suppress a delay time difference between two differential signals in a differential transmission line having a bending region. It is disclosed.

Patent document 2 is an optical transmission module structure of a single power supply drive system that enables both suppression of peaking in small signal transmission characteristics (S ₂₁ ) and reduction in small signal reflection characteristics (S ₁₁ ). An optical semiconductor element mounting substrate on which an optical semiconductor element having a modulator is mounted, and a ground electrode, an input transmission path for inputting an electric signal to the optical modulator, and a termination resistance for the input electric signal are formed on the substrate surface And an anode electrode of the light modulator connected to the ground electrode by a bonding wire is provided on the surface of the optical semiconductor element, and the electrode on the ground side of the termination resistor and the light modulator Discloses an optical semiconductor element mounting substrate connected to another anode electrode of the semiconductor device by another bonding wire.

JP, 2012-199904, A JP 2007-286454 A

  The high frequency signal applied to the light modulator interferes with the light source (semiconductor laser device), the current applied to the light source is modulated, and noise may occur in the optical signal. Specifically, since a high frequency signal is applied to the optical modulator, a modulation current flows, and when the modulation current fluctuates, the magnetic field fluctuates. The driving current of the light source, which should be essentially constant, fluctuates because the magnetic field generates an electromotive force in the direct current line that flows the current to the light source, and the intensity and the wavelength of the light output from the light source fluctuate and are fluctuated. Since the light modulator further modulates the output light of the light source, noise is generated in the light signal output from the light modulator.

  FIG. 8 shows a top view of a semiconductor optical modulator integrated light emitting element mounted on a chip carrier of an optical transmission module according to the prior art. The semiconductor light modulator integrated light emitting element 1 including the modulator unit 2 and the light source unit 3, the chip capacitor 5, the termination resistor 4, the six via holes 6, and the modulation current line 23 are on the ground (GND) pattern 30 of the chip carrier 101. Provided in Here, the modulator unit is an electroabsorption modulator, and the light source unit 3 is a distributed feedback laser.

  The Au wire 11 electrically connects the modulation current line 23, the modulator unit 2, and the termination resistor 4. The Au wire 12 electrically connects the chip capacitor 5 and the light source unit 3. The via hole 6 electrically connects the GND pattern 30 on the chip carrier 101 on which the semiconductor light modulator integrated light emitting element 1 is mounted to the grounded back surface of the chip carrier 101. The termination resistor 4 is impedance matched so as to suppress reflection of the modulation current supplied to the modulator unit 2 through the Au wire 11.

  A direct current is injected into the light source unit 3 via the chip capacitor 5 and the Au wire 12 to output continuous (CW: Continuous Waveform) light. A modulation voltage is applied to the modulation current line 23 and the ground pattern 30 in the modulator unit 2, and the CW light is modulated to generate an optical signal. At this time, the modulation current flowing to the modulator unit 2 generates an electromotive force in the drive circuit of the light source unit 3 by electromagnetic induction. Due to the electromotive force, the direct current (drive current) supplied to the light source unit 3 is modulated, and noise may be generated in the continuous light output from the light source unit 3.

  In order to suppress noise of CW light output from such a light source unit 3, a chip capacitor 5 as a bypass capacitor is provided between the light source unit 3 and a power supply (not shown) for supplying a drive current to the light source unit 3. Provided. The chip capacitor 5 can suppress the modulation of the voltage by storing or releasing the charge even if the voltage is modulated by the addition of the electromotive force to the drive current to the light source unit 3. As a result, the chip capacitor 5 can suppress the noise by stabilizing the drive current of the light source unit 3.

  However, the chip capacitor requires an installation area, and in the case where a plurality of light sources are mounted, the chip capacitor is required for each light source. Therefore, chip capacitors have been a hindrance to miniaturizing and high-density mounting of optical transmission modules.

  Therefore, an object of the present invention is to provide an optical transmission module that realizes miniaturization and high density mounting while suppressing noise, and an optical module using the same.

  (1) A light transmission module according to the present invention comprises a light source generating continuous light, at least one modulator modulating the continuous light, and a pair of DC current lines connected to the light source and flowing DC current supplied to the light source And a modulation current line pair connected to the modulator and applying a modulation signal supplied to the modulator. Only one of the lines constituting the DC current line pair or the lines constituting the modulation current line pair intersects at least once.

  (2) In the optical transmission module according to (1), the lines forming the DC current line pair may intersect at least once.

  (3) The optical transmission module according to (2) may further include a plurality of modulators and a plurality of modulation current pairs respectively connected to the plurality of modulators.

  (4) The optical transmission module according to any one of (1) to (3) may further include one semiconductor substrate. The light source may be integrated with the modulator on the one semiconductor substrate to constitute a modulator integrated light source.

  (5) In the optical transmission module described in (4), it may further have one carrier. The modulator integrated light source may be mounted on the one carrier.

  (6) The optical transmission module according to any one of (1) to (3) may further have one carrier. The modulator and the light source may be mounted on the one carrier.

  (7) In the optical transmission module according to any one of (1) to (6), the modulator may be an electroabsorption modulator.

  (8) In the optical transmission module according to any one of (1) to (6), the modulator may be a Mach-Zehnder modulator.

  (9) In the optical transmission module according to any one of (1) to (8), the first line constituting the DC current line pair is a first member, and a second member separated from the first member. And a metal wire connecting the first member and the second member, the second line constituting the DC current line pair comprising a first straight portion, a second straight portion, and the first straight portion and the first straight portion. Integrally has a bend located between two straight parts, the first member extends parallel to the first straight part, and is on one straight line with the second straight part, The second member extends in parallel with the second straight portion and exists on one straight line with the first straight portion, and the bent portion and the metal wire are lateral to the pair of modulated current lines. May cross.

  (10) The optical module according to the present invention includes the optical transmission module according to any one of (1) to (9), and a printed circuit board connected to the optical transmission module and a lens.

  The optical transmission module of the present application does not use large parts, but suppresses that the modulation component applied to the modulator affects the direct current injected to the light source, and injects a stable direct current to the light source. It becomes possible to provide an optical transmission module excellent in characteristics and compact and an optical module incorporating the same.

It is a schematic diagram which shows the structure of the optical transmission apparatus with which the optical module which concerns on 1st embodiment of this application was mounted. It is the schematic which shows an optical transmission module, a printed circuit board, and a flexible substrate. FIG. 6 illustrates a top view of a semiconductor light modulator integrated light emitting device mounted on a chip carrier of the light transmitting module according to the first embodiment of the present application. FIG. 10 illustrates a top view of a semiconductor optical modulator integrated light emitting device mounted on a chip carrier of an optical transmission module according to a second embodiment of the present application. FIG. 10 shows a top view of a semiconductor optical modulator integrated light emitting element mounted on a chip carrier of an optical transmission module according to a third embodiment of the present application. FIG. 10 illustrates a top view of a semiconductor light modulator integrated light emitting device mounted on a chip carrier of an optical transmission module according to a fourth embodiment of the present application. FIG. 20 illustrates a top view of a semiconductor light modulator integrated light emitting device mounted on a chip carrier of an optical transmission module according to a fifth embodiment of the present application. The top view of the semiconductor light modulator integration type light emitting element mounted in the chip carrier of the light transmission module concerning the conventional technology is expressed.

First Embodiment
FIG. 1 is a schematic view showing the configuration of an optical transmission apparatus equipped with an optical module according to the first embodiment of the present application. A plurality of optical modules 200 are attached to the optical transmission device 400 by the electrical connectors 202, respectively. The optical transmission device 400 is, for example, a large-capacity router or switch. The optical transmission device 400 has, for example, the function of a switch, and is disposed in a base station or the like. The optical transmission device 400 acquires data for reception (electrical signal for reception) from the optical module 200, and uses the IC 206 mounted on the circuit board 204 to determine what data is to be transmitted to where. , Transmit data (electrical signal for transmission) and transmit the data to the corresponding optical module 300.

The optical module 300 includes a printed circuit board 310, a flexible substrate 312, and an optical subassembly 314 for converting an optical signal and an electrical signal from at least one to the other. The printed circuit board 310 is an inflexible rigid board. The printed board 310 and the optical subassembly 314 are connected via the flexible board 312. Electrical signals are transmitted from the printed circuit board 10 to the optical subassembly 314 via the flexible board 312. In addition, an electrical signal is transmitted from the optical subassembly 314 to the printed circuit board 310 via the flexible board 312. The light conversion element of the light subassembly 314 is an element that converts one of an optical signal and an electric signal into the other. A light conversion element that converts an electrical signal into an optical signal is a light emitting element, and a light conversion element that converts an optical signal into an electrical signal is a light receiving element. The light subassembly 314 includes at least one (for example, both) of a light emitting element and a light receiving element. An optical fiber 316 is connected to the optical subassembly 314 for input and output of optical signals.

FIG. 2 is a schematic view showing an optical subassembly, a printed board and a flexible board. The optical subassembly 314 is connected to one end of the flexible substrate 312. The other end of the flexible substrate 312 is electrically connected to the printed circuit board 310 in an overlapping manner. The optical transmission module 300 of the present application is an optical subassembly having a transmission function. The optical transmission module 300 includes a signal source (details will be described later) that internally generates an optical signal, a lens (not shown) for optically coupling the output light thereof to the optical fiber 316, and the like.

  FIG. 3 shows a top view of a semiconductor optical modulator integrated light emitting element which is a signal source mounted on a chip carrier of an optical transmission module according to an embodiment of the present application. The semiconductor light modulator integrated light emitting element 1 including the modulator unit 2 and the light source unit 3, the termination resistor 4, the DC current lines 21 and 22 electrically connected to the light source unit 3, and the modulator unit 2 electrically The modulation current lines 23 and 24 to be connected are provided on the chip carrier 101.

  The light source unit 3 is preferably, but not limited to, a distributed feedback laser diode (DFB-LD). The light source unit 3 is a CW light source.

  The modulator unit 2 is provided to modulate the CW light emitted from the light source unit 3. The modulator unit 2 may be an electro-absorption (EA) modulator or a Maha-Zehnder (MZ) modulator. In the illustrated embodiment, the modulator section 2 is an EA type modulator. In the present embodiment, the light source (light source unit 3) and the modulator (modulator unit 2) constitute a modulator integrated light source integrated on one semiconductor substrate. The cathodes of the light source unit and the modulator unit are common to the semiconductor substrate side, and are connected to the chip carrier 101 on the back side of the semiconductor substrate (the opposite surface of the surface on which the light source and the modulator are formed). .

  The chip carrier 101 is a ceramic substrate such as AlN having a conductor film formed on the surface. The semiconductor light modulator integrated light emitting element 1 and the chip carrier 101 are joined by solder.

  In the illustrated embodiment, the modulation current lines 23 and 24 (a pair of modulation current lines) connected to the modulator unit 2 are the anode side modulation current line of the modulator unit 2 and the cathode side modulation current line of the modulator unit 2 respectively. It is. In the illustrated embodiment, the DC current lines 21 and 22 connected to the light source unit 3 are respectively a cathode side DC current line of the light source unit 3 and an anode side DC current line pair of the light source unit 3.

  The termination resistor 4 is impedance matched so as to suppress reflection of the modulation current supplied to the modulator unit 2 through the Au wire 11. In the present embodiment, it is 50Ω. The Au wire 11 electrically connects the modulation current line 23, the modulator unit 2, and the termination resistor 4. The Au wire 12 electrically connects the DC current line 22 and the light source unit 3. The Au wire 13 is included in the DC current line 21 and provided so as to cross the DC current line 22.

  The direct current line 21 includes a first member 21a, a second member 21b, and an Au wire 13 connecting the first member and the second member. The first member 21a and the second member 21b are spatially separated. The Au wire 13 connects the first member 21a and the second member 21b. The DC current line 22 integrally includes a straight portion 22a, a straight portion 22b, and a bent portion located between the straight portion 22a and the straight portion 22b. The first member 21a extends in parallel with the straight portion 22a, and exists on one straight line with the straight portion 22b. The second member 21b extends in parallel with the straight portion 22b, and exists on one straight line together with the straight portion 22a. The bent portion of the DC current line 22 crosses the Au wire 13 at the side of the modulation current lines 23 and 24.

  A modulation voltage (modulation signal) is applied to modulate the CW light emitted from the light source unit 3. As a result, the modulation current of the modulator unit 2 flows through the modulation current lines 23 and 24. The surrounding magnetic field also fluctuates with the fluctuation of the flowing modulation current. The driving current of the light source unit 3 fluctuates because an electromotive force is generated in the driving current circuit of the light source unit 3 including the DC current lines 21 and 22 due to the magnetic field fluctuation. As a result, noise is generated in the light signal emitted from the light source unit 3.

  However, in the optical transmission module according to the present embodiment, the drive current circuit including the DC current lines 21 and 22 is crossed by the Au wire 13. The drive current circuit is divided into two closed circuits in a region where the DC current lines 21 and 22 cross each other. Therefore, the direction of the electromotive force that the surrounding magnetic field fluctuation causes in one closed circuit is opposite to the direction of the electromotive force that the surrounding magnetic field fluctuation causes in the other closed circuit. The two cancel each other. As described above, when the electromotive forces cancel each other, the induced current due to the modulation current is suppressed, and the fluctuation of the drive current of the light source unit 3 is also suppressed. As a result, noise generated in the light signal emitted from the light source unit 3 can be suppressed.

  The driving current of the light source unit 3 can be stabilized by intersecting the DC current lines 21 and 22 of the light source unit 3. Therefore, in the optical transmission module according to the present embodiment, the chip capacitor 5 used in the conventional structure of FIG. 8 is unnecessary, and as a result, the chip carrier size of the optical transmission module can be reduced.

  In the illustrated embodiment, the semiconductor light modulator integrated light emitting element 1 includes only one modulator unit 2, but may include a plurality of modulator units 2. In the case where the semiconductor light modulator integrated light emitting element 1 includes two modulator sections 2 and the two modulation current line pairs connected to each are arranged in parallel, as shown in FIG. By crossing the DC current line pair connected to the portion 3, the influence of noise caused by the modulation current flowing in the two modulation current line pairs can be suppressed. Further, the same effect can be obtained even in the case where both of the two modulation current line pairs are crossed, without crossing the DC current line pairs. Furthermore, when the DC current line pair is not crossed, and only one of the two modulated current line pairs is crossed, crosstalk between the two modulated current line pairs can be suppressed. And, at least the influence of the crossed modulation current line pair on the DC current line pair can be suppressed. The same effect can be obtained when the number of modulator sections is not limited to two and a plurality of modulator sections are provided.

Second Embodiment
FIG. 4 shows a top view of the semiconductor optical modulator integrated light emitting device mounted on the chip carrier of the optical transmission module according to the second embodiment of the present application. The present embodiment is the same as the first embodiment except that the Au wire 13 is disposed perpendicularly to the modulation current lines 23 and 24.

  The Au wire 13 is included in the DC current line 21 so as to cross the DC current line 22 and is orthogonal to the modulation current lines 23 and 24. Therefore, almost no electromotive force is generated in the Au wire 13 due to electromagnetic induction of the modulation current flowing to the modulator unit 2.

Third Embodiment
FIG. 5 shows a top view of a semiconductor optical modulator integrated light emitting device mounted on a chip carrier of an optical transmission module according to a third embodiment of the present application. The difference between the present embodiment and the first embodiment is the arrangement of the DC current lines 21 and 22, the modulation current lines 23 and 24, and the termination resistor 4. More specifically, the DC current line 21 and the modulation current line 24 are disposed behind the semiconductor light modulator integrated light emitting element 1 (a position opposite to the light emitting end of the light source unit 3), and the Au wires 12 and 13 It is not included in the direct current line 22 and the direct current line 21 does not include the Au wire 13. Furthermore, the arrangement of the DC current lines 21 and 22 is reversed. The arrangement of the modulation current lines 23, 24 is similarly reversed to that of the first embodiment. The termination resistor 4 is disposed on the right side of the semiconductor light modulator integrated light emitting element 1 in FIG.

  It can be seen from the figure that the carrier width is reduced by arranging the DC current line 21 and the modulation current line 24 behind the semiconductor light modulator integrated light emitting element 1. As a result, further miniaturization and high density mounting of the optical transmission module can be realized. Although the arrangement on the anode side and the cathode side of the current line connected to the modulator unit 2 and the light source unit 3 is reversed compared to the first embodiment, the DC current line 21 connected to the light source unit 3 , 22 cross each other to obtain the same effect as that of the first embodiment.

Fourth Embodiment
FIG. 6 shows a top view of a semiconductor optical modulator integrated light emitting device mounted on a chip carrier of an optical transmission module according to a fourth embodiment of the present application. In the present embodiment, the direct current line 21 is bent outward in a region intersecting with the Au wire 13, and the arrangement of the direct current line 21 and the Au wires 12 and 13 is different accordingly. And it is the same as that of a third embodiment except arrangement of termination resistance 4. Also in the present embodiment, the carrier width can be reduced and reduced as in the third embodiment shown in FIG. 5 to realize further miniaturization and high density mounting of the optical transmission module. And although the direction of crossing of a 3rd embodiment and a direct current line is opposite, the same effect as a 3rd embodiment is acquired.

Fifth Embodiment
FIG. 7 shows a top view of the semiconductor optical modulator integrated light emitting device mounted on the chip carrier of the optical transmission module according to the fifth embodiment of the present application. The present embodiment differs from the first embodiment in that not the DC current line but the modulation current line intersect. The modulation current line 24 includes the Au wire 14, and the modulation current line 23 is bent outward in a region intersecting the Au wire 14. And, the DC current line does not cross at the side of the intersection of the modulation current line.

  As described above, the fluctuating current generates an induced magnetic field generated from each of the lines constituting the modulated current lines 23, 24 by electromagnetic induction, and the induced magnetic field generates an electromotive force in the DC current lines 21, 22 connected to the light source unit 3. By generating the noise, noise is generated in the light source unit 3 and the DC current lines 21 and 22. However, when the modulation current lines 23 and 24 cross each other, induced magnetic fields generated from the lines constituting the modulation current lines 23 and 24 are generated in different directions by electromagnetic induction. As a result, the induced magnetic fields generated cancel each other, and noise to the light source unit 3 and the DC current lines 21 and 22 is suppressed. Thus, the effect of the present invention can be obtained by crossing only one of the lines connected to the modulator unit 2 or the light source unit 3.

  In the light transmitting module according to the first to fifth embodiments described above, the modulator unit 2 and the light source unit 3 are provided on the semiconductor light modulator integrated light emitting element 1, but the modulator unit 2 and the light source unit 3 are It does not have to be accumulated.

  DESCRIPTION OF SYMBOLS 1 semiconductor light modulator integrated type light emitting element, 2 modulator part, 3 light source part, 4 termination resistance, 5 chip capacitor, 6 via hole, 11 Au wire, 12 Au wire, 12 Au wire, 13 Au wire, 14 Au wire, 21 direct current line , 22 DC current line, 23 modulation current line, 24 modulation current line, 30 GND pattern, 101 chip carrier, 200 optical module, 202 electrical connector, 204 circuit board, 206 IC, 300 optical transmission module, 310 printed board, 312 flexible Substrate, 314 optical subassembly, 316 optical fiber, 400 optical transmission device.

Claims (10)

Light source that generates continuous light,
At least one modulator that modulates the continuous light;
An optical transmission comprising: a DC current line pair connected to the light source and flowing DC current supplied to the light source; and a modulated current line pair connected to the modulator and applying a modulation signal supplied to the modulator A module,
Only one of the lines constituting the DC current line pair or the lines constituting the modulation current line pair intersects at least once.
An optical transmission module characterized by The optical transmission module according to claim 1, wherein the lines constituting the DC current line pair intersect at least once.
An optical transmission module characterized by The optical transmission module according to claim 2, wherein
A plurality of modulators, and a plurality of modulation current pairs respectively connected to the plurality of modulators;
An optical transmission module characterized by The optical transmission module according to any one of claims 1 to 3, further comprising one semiconductor substrate,
The light source constitutes a modulator integrated light source by being integrated on the one semiconductor substrate together with the modulator.
An optical transmission module characterized by The optical transmission module according to claim 4, further comprising one carrier.
The modulator integrated light source is mounted on the one carrier,
An optical transmission module characterized by The optical transmission module according to any one of claims 1 to 3, further comprising one carrier.
The modulator and the light source are mounted on the one carrier,
An optical transmission module characterized by   The optical transmission module according to any one of claims 1 to 6, wherein the modulator is an electro-absorption modulator.   The optical transmission module according to any one of claims 1 to 6, wherein the modulator is a Mach-Zehnder modulator. The optical transmission module according to any one of claims 1 to 8, wherein
The first line constituting the DC current line pair includes a first member, a second member separated from the first member, and a metal wire connecting the first member and the second member,
The second line constituting the DC current line pair integrally has a first straight portion, a second straight portion, and a bent portion located between the first straight portion and the second straight portion.
The first member extends parallel to the first straight portion, and exists on one straight line with the second straight portion.
The second member extends in parallel with the second straight portion, and exists on one straight line with the first straight portion.
The bent portion and the metal wire intersect at a side of the modulated current line pair.
An optical transmission module characterized by   An optical module comprising: the optical transmission module according to any one of claims 1 to 9; and a printed circuit board connected to the optical transmission module and a lens.

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