JP4848719B2 - Optical device and optical communication device - Google Patents

Description

  The present invention relates to an optical device and an optical communication apparatus. Specifically, a phase correction means for correcting the phase difference of the differential signal is provided in the connection pattern for transmitting the differential signal for driving the light emitting element and / or the differential signal generated by the light receiving element. Communication characteristics are obtained.

  With the rapid increase in communication demand in recent years, high-speed and large-capacity networks have been achieved by using optical communication. In such optical communication, for example, an optical communication module corresponding to a standard called XFP (10 Gigabit Small Form Factor Pluggable) is used.

  In the optical communication module, an optical subassembly called TOSA (Transmitter Optical Sub-Assembly) or ROSA (Receiver Optical Sub-Assembly) is used. In the optical subassembly, for example, as described in Patent Document 1, a can packaged optical device having a light emitting / receiving element is used, and a circuit board on which an integrated circuit or the like is mounted and the optical device are connected by a flexible substrate. And stored in one housing. Furthermore, an optical connector is provided integrally with the housing so that the optical fiber can be fixed at a predetermined position with respect to the optical device of the can package, and the fixed optical fiber can be removed.

JP 2003-249711 A

  By the way, when driving a light emitting element such as a surface emitting laser element, the surface emitting laser element is driven using a differential signal in order to reduce the influence of noise or the like. Further, the connection pattern used for transmitting the differential signal is formed symmetrically so that the phase difference of the differential signal does not fluctuate greatly during the transmission of the differential signal.

  However, when connecting the surface emitting laser element and the connection pattern, for example, a surface emitting laser element 90 is placed on the connection pattern PTb for transmitting one of the differential signals, as shown in FIG. When the cathode of the surface emitting laser element 90 and the connection pattern PTb are connected, the anode of the surface emitting laser element 90 is connected to the connection pattern PTa for transmitting the other signal of the differential signal using the bonding wire BW. Become.

  For this reason, even if the connection patterns PTa and PTb are formed symmetrically, the cathode and the anode of the surface emitting laser element 90 are different in connection method with the connection pattern, so that the phase difference of the differential signal varies. When the phase difference fluctuates in this way, the pass characteristic (S21) does not become a flat characteristic due to a dip in which the signal level is attenuated as shown in FIG. 11A. FIG. 11B shows the phase difference characteristics.

  Here, for example, when communication is performed using a method in which frequency components are distributed over a wide frequency band, such as high-speed serial transmission, it is desirable that the pass characteristic is a flat characteristic. However, if communication is performed using the optical device as described above, there is a possibility that the communication characteristics may be deteriorated because a dip occurs in the pass characteristics.

  Accordingly, the present invention provides an optical device and an optical communication apparatus that can obtain good communication characteristics.

Light device according to the present invention includes a mount substrate on which a light emitting element or a light receiving element is mounting location, is formed on the mounting board, the differential signal for driving the mounted light emitting element, or It said first and second connection patterns for transmitting placed on the differential signal generated by the light receiving element has a light-emitting device or the light receiving element is the placement has one electrode the first A stub for correcting the phase difference between the signals of any one of the differential signals , and the other electrode is electrically connected to the second connection pattern by a bonding wire. The second connection pattern is formed.

  According to the present invention, the phase correction means for correcting the phase difference of the differential signal is provided in the connection pattern for transmitting the differential signal for driving the light emitting element and / or the differential signal generated by the light receiving element. Therefore, the phase difference of the differential signal is kept at the correct phase difference, the passing characteristic becomes flat, and good communication characteristics can be obtained.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of the optical communication apparatus. The optical communication apparatus 10 includes, for example, a transmission optical subassembly 20 called TOSA (Transmitter Optical Sub-Assembly), a reception optical subassembly 30 called ROSA (Receiver Optical Sub-Assembly), and transmission / reception. The processing substrate 40 is configured to be stored in one housing.

  The transmission / reception processing board 40 is provided with control circuits 42 and 43. The control circuit 42 is for controlling the operation of the transmission optical subassembly 20, processing of signals to be transmitted, communication with devices connected to the connector terminal portion 41, and the like. The control circuit 43 is for controlling the operation of the receiving optical subassembly 30, processing of received signals, communication with devices connected to the connector terminal portion 41, and the like.

  The transmission optical subassembly 20 and the transmission / reception processing substrate 40 are connected by a connection substrate, that is, a flexible substrate 29 having flexibility. Similarly, the receiving optical subassembly 30 and the transmission / reception processing board 40 are connected by a flexible board 39. The flexible substrates 29 and 39 have less loss even when a signal supplied from the transmission / reception processing substrate 40 to the transmission optical subassembly 20 or a signal supplied from the reception optical subassembly 30 to the transmission / reception processing substrate 40 is at a high frequency. Thus, for example, a transmission line having a microstrip line structure adjusted to a predetermined impedance characteristic is used.

  The transmission / reception processing board 40 has the connector terminal portion 41 as described above. By attaching the connector terminal portion 41 to a connector provided in another device or the like, the optical communication device 10 is connected to another device. Etc. can be electrically connected. In FIG. 1, a connection pattern for connecting the circuit elements of the transmission / reception processing board 40 and the flexible boards 29 and 39, a connection pattern for connecting the circuit elements and the connector terminal portion 41, and the like are omitted.

  2A and 2B are diagrams for explaining a schematic configuration of the transmission optical subassembly 20, FIG. 2A is a front view of the transmission optical subassembly 20, and FIG. 2B is a cross-section taken along the line II ′ in FIG. 2A. FIG.

  The transmission optical subassembly 20 includes a holder 21 and a can package transmission optical device 22 housed in the holder 21. In FIG. 2B, only the holder 21 is shown in cross section.

  The holder 21 has a recess 211 for attaching the transmission optical device 22, and a light passage hole 212 into which an optical fiber is inserted is formed at the center of the recess 211.

  The transmission optical device 22 has a configuration in which a cap 221 is sealed to a disc-shaped stem 222. The cap 221 has a window or lens 221a for emitting laser light to the outside. The lens 221a condenses the laser light emitted from the surface emitting laser element provided in the transmitting optical device 22 on the core of the optical fiber. The internal configuration of the transmission optical device 22 will be described later.

  The transmitting optical device 22 is positioned and fixed to the holder 21 so that the laser light emitted through the lens 221a is efficiently incident on the core of the optical fiber inserted into the light passage hole 212 of the holder 21. . By fixing the holder 21 and the transmission optical device 22 in this way, the laser light emitted from the transmission optical device 22 is efficiently incident on the core of the optical fiber simply by inserting the optical fiber into the holder 21. Thus, the optical fiber can be positioned by the holder 21.

  Similarly to the transmission optical subassembly 20, the reception optical subassembly 30 is configured by fixing the reception optical device of the package to the holder, and can be emitted from the optical fiber simply by inserting the optical fiber into the holder. The optical fiber is positioned by the holder so that the laser beam is efficiently incident on the receiving optical device 32.

  Next, the transmission optical device 22 will be described. FIG. 3 is a perspective view showing the inside of the transmission optical device 22. 4A is a front view showing the inside of the transmission optical device 22, and FIG. 4B is a schematic sectional view taken along the line II-II ′ of FIG. 4A.

  The disc-shaped stem 222 is provided with through holes 223a to 223d through which the terminals 231a to 231d are inserted. A mount substrate 241 is fixed to the upper surface of the stem 222. The mount substrate 241 is a ceramic substrate that is a high dielectric material.

  The mount substrate 241 is provided with a surface emitting laser element 242 for emitting laser light and a light receiving element 243 for monitoring the emission level of the laser light. Further, a connection pattern for connecting the surface emitting laser element 242 and the light receiving element 243 to the terminals is formed on the disc-shaped stem 222.

  The connection patterns are connected to the connection pattern 244a to which the anode of the surface emitting laser element 242 is connected, the connection pattern 244c on which the cathode side of the surface emitting laser element 242 is mounted, the connection pattern 244b to be connected to the terminal 231a, and the terminal 231b. The connection pattern 244d and the connection pattern 244e on which the cathode side of the light receiving element 243 is placed, and each connection pattern is adjusted to a predetermined impedance characteristic so as to reduce loss as a microstrip line structure.

  The anode of the surface emitting laser element 242 and the connection pattern 244a are connected by a bonding wire. A connection pattern 244b is connected to the connection pattern 244a via a resistor 245a, and the connection pattern 244b and the terminal 231a are connected by a bonding wire.

  A connection pattern 244d is connected to the connection pattern 244c on which the surface emitting laser element 242 is mounted and connected to the cathode of the surface emitting laser element 242 via a resistor 245b, and the connection pattern 244d and the terminal 231b are connected by a bonding wire. Connecting. The anode of the light receiving element 243 is connected to the terminal 231c, and the connection pattern 244e on which the cathode side of the light receiving element 243 is mounted is connected to the terminal 231d. The resistors 245a and 245b are for limiting the amplitude when the surface emitting laser element 242 is pulse-driven.

  The terminals 231a to 231d are coaxially aligned with the through holes 223a to 223d. Thereafter, the through holes 223a to 223d are filled with, for example, a glass sealing material, thereby fixing the terminals 231a to 231d and simultaneously sealing the through holes 223a to 223d.

  Here, when a substrate with a high relative dielectric constant is used as the mount substrate 241, the speed of the signal flowing through the connection pattern is slower than when a substrate with a low relative dielectric constant is used. Therefore, the electrical length of the connection pattern when using a substrate having a high relative dielectric constant is shorter than the physical length. On the other hand, since the bonding wire is provided in the space, the electrical length and the physical length are equal. For this reason, if the connection patterns 244a and 244c are formed symmetrically, the phase delay of the signal supplied to the cathode becomes larger than the signal supplied to the anode, and the phase difference of the differential signal fluctuates. Therefore, the physical length of the connection pattern 244c connected to the cathode is shortened to reduce the phase delay of the signal supplied to the cathode, or the physical length of the connection pattern 244a connected to the anode is lengthened to the anode. If the phase delay of the supplied signal is increased, the phase difference of the differential signal can be corrected to 180 degrees. However, there is a limit to shortening the physical length of the connection pattern 244c. In order to reduce the size of the transmission optical device 22, there is a limit to increasing the physical length of the connection pattern 244a. For this reason, phase correction means is provided in the connection pattern 244a, for example, to delay the phase of the signal supplied to the anode so that the phase difference of the differential signal supplied to the surface emitting laser element 242 becomes 180 degrees. To correct.

  As this phase correction means, for example, a stub 244as is provided in the connection pattern 244a. Providing the stub 244as increases the capacitive load and increases the phase delay of the signal supplied to the anode. Therefore, the phase difference of the differential signal supplied to the surface emitting laser element 242 can be corrected. Here, the size of the stub 244as is set so that the phase difference of the differential signal becomes 180 degrees due to the phase delay of the signal supplied to the anode.

  As described above, when the surface emitting laser element 242 is differentially driven, by providing the phase correction means, even if the connection method of the connection pattern is different between the cathode and the anode of the surface emitting laser element 242, By correcting the phase difference of the differential signal supplied to the surface emitting laser element 242 to an optimum phase difference, it is possible to obtain a flat passing characteristic and to obtain a good communication characteristic.

  By the way, when the fluctuation amount of the phase difference of the differential signal changes due to the characteristic variation of the flexible substrate 29 or the mount substrate 241, a pattern of the stub 244as is formed on the mount substrate 241, and the phase of one signal is set to a predetermined amount. There is a possibility that the phase difference of the differential signal cannot be corrected to a good state only by delaying only by this amount. Therefore, even if characteristic variations of the flexible substrate 29 and the mount substrate 241 occur, the phase delay amount can be adjusted, so that the phase difference of the differential signal supplied to the surface emitting laser element 242 can be improved. An optical device for transmission that can be corrected will be described with reference to FIG. In FIG. 5, for simplicity of description, the resistors 245a and 245b are omitted, and the connection pattern 244a and the terminal 231a are connected, and the connection pattern 244c and the terminal 231b are connected.

  In the connection pattern 244a, not only the stub 244as but also the stub 244at is formed. Further, on the stub 244at, a capacity varying means is provided that makes it possible to adjust the phase delay amount by varying the capacity of the stub. By using a micro electro mechanical system (MEMS) device such as the MEMS switch 25 as the capacity varying means, the capacity of the stub can be adjusted without using a large substrate area.

  FIG. 6 shows a schematic configuration of the contact portion of the MEMS switch 25. FIG. 7 is a schematic sectional view taken along the line III-III ′ of FIG. 6 in order to explain the operation of the MEMS switch 25.

  In the MEMS switch 25, an electrode support portion 250 is formed on both sides of the stub 244at, and a deformable electrode plate 251 is installed on the electrode support portion 250 to form a shunt-type switch configuration. A dielectric layer 255de is formed on the stub 244at. The electrode plate 251 is grounded, and the distance between the electrode plate 251 and the stub 244at is controlled so that the capacitance of the capacitor formed by the electrode plate 251 and the stub 244at can be varied. In this way, if the capacitance of the capacitor can be varied, it is possible to adjust the phase lag of the signal supplied to the anode, and even if the amount of variation in the phase difference of the differential signal changes, the differential signal Can be corrected with high accuracy.

  The distance between the electrode plate 251 and the stub 244at is controlled using electrostatic attraction or thermal deformation. That is, by applying a continuous control voltage to an electrode (not shown) and deforming the electrode plate 251 to the stub 244at side by electrostatic attraction, the distance between the electrode plate 251 and the stub 244at can be varied. In addition, the electrode plate 251 is formed by laminating two materials having different thermal expansion coefficients, and the electrode plate 251 is heated to the stub 244at side by supplying a control current to the electrode plate 251 and heating the electrode plate 251. The distance between the electrode plate 251 and the stub 244at can be varied by thermal deformation.

  Here, for example, when a control signal (control voltage or control current) is not supplied, the gap between the electrode plate 251 and the stub 244at is wide as shown in FIG. 7A. In this case, since the capacitance is small, the phase delay is small. When a control signal is supplied and the distance between the electrode plate 251 and the stub 244at is narrowed as shown in FIG. 7B, the capacitance increases and the phase delay of the signal increases. In other words, the phase difference of the differential signal can be adjusted by controlling the distance between the electrode plate 251 and the stub 244at by the control signal.

  The MEMS switch 25 is controlled by a control circuit 42 provided on the transmission / reception processing board 40, for example. That is, the laser light emission level is detected by the light receiving element 243 and the detection result is supplied to the control circuit 42. The control circuit 42 stores control information on how to control the electrical length in accordance with the laser light emission level, and generates a control signal based on the control information in accordance with the laser light emission level. Further, the generated control signal is supplied to one terminal of the MEMS switch 25 via the flexible substrate 29 and the terminal 231e. The other terminal of the MEMS switch 25 is connected to the stem 222 that is grounded. In this way, it is possible to automatically control so that the phase difference of the differential signal is in a good state, so that a flat pass characteristic can be obtained easily and easily.

  In the above-described embodiment, the transmission optical device 22 of the transmission optical subassembly 20 has been described. However, the phase correction means is also provided for the reception optical device of the reception optical subassembly 30 as described above. . That is, assuming that a light receiving element is used instead of the surface emitting laser element 242, a phase correction means is provided in a connection pattern connected to the light receiving element by a bonding wire. Further, the light receiving element 243 for monitoring the output of the laser light is deleted.

  In this way, even if the connection method of the connection pattern is different between the anode side and the cathode side of the light receiving element, the phase difference of the differential signal supplied to the control circuit 43 is corrected to an optimum state. Therefore, it is possible to obtain a flat passing characteristic and a good communication characteristic.

  Next, an example in which the stub 244as is provided will be described. As shown in FIG. 8A, the mount substrate 241 is configured as a multilayer substrate in which ceramic substrates 246 and 248 are provided between three conductor layers 244, 247 and 249. As shown in FIG. 8B, connection patterns 244a to 244e are formed on the first conductor layer 244. A stub 244as is formed in the connection pattern 244a.

  A ground layer 247a is formed on the second conductor layer 247 as shown in FIG. 8C. A ceramic substrate (alumina) is provided as a dielectric layer 246 between the first conductor layer 244 and the second conductor layer 247, and the connection patterns 244 a, 244 b and 244 d of the first conductor layer 244 and the second conductor layer 247 are in contact with each other. A microstrip line is formed with the formation 247a. The thickness of the dielectric layer 246 is 0.15 mm, and the relative dielectric constant is 9.2.

  On the third conductor layer 249, a ground layer 249a is formed as shown in FIG. 8D. A ceramic substrate (alumina) is provided as the dielectric layer 248 between the second conductor layer 247 and the third conductor layer 249. The ground layer 247a of the second conductor layer 247 and the ground layer 249a of the third conductor layer 249 are electrically connected by vias, through holes, or the like, so that the connection pattern 244c of the first conductor layer 244 and the third conductor layer 249 are in contact with each other. A microstrip line is formed with the formation 249a. The thickness of the dielectric layer 248 is 0.2 mm, and the relative dielectric constant is 9.2. Thus, since the connection pattern 244c forms a microstrip line with the ground layer 249a, the dielectric layer becomes thicker than when the ground layer 247a forms a microstrip line, and the pattern of the connection pattern 244c. When the width is constant, the effective relative dielectric constant becomes small. Therefore, the phase delay of the signal supplied to the cathode can be reduced.

  FIG. 9 shows characteristics when the mount substrate 241 is configured as shown in FIG. By forming the stub 244as in the connection pattern 244a of the mount substrate 241 and correcting the phase difference of the differential signal, the pass characteristic (S21) reduces the occurrence of dip as shown in FIG. It became flat characteristics. Further, the phase difference characteristic is as shown in FIG. 9B, which can be reduced as compared with FIG. 11B.

It is a perspective view which shows schematic structure of an optical communication apparatus. It is a figure which shows the structure of the optical subassembly for transmission. It is a perspective view which shows the inside of the optical device for transmission. It is a figure which shows the inside of the optical device for transmission. It is a figure which shows the other structure of the optical device for transmission. It is a figure which shows schematic structure of the contact part of a MEMS switch. It is a figure for demonstrating operation | movement of a MEMS switch. It is a figure which shows the structure of an Example. It is a figure which shows the characteristic of an Example. It is a figure which shows the conventional structure. It is a figure which shows the conventional characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical communication apparatus, 20 ... Optical subassembly for transmission, 21 ... Holder, 22 ... Optical device for transmission, 25 ... MEMS switch, 29, 39 ... Flexible substrate, 30 ... Receiving optical subassembly, 32 ... Receiving optical device, 40 ... Transmission / reception processing board, 41 ... Connector terminal section, 42,43 ... Control circuit, 90,242 ... Light emitting laser element, 211... Recess, 212... Light passage hole, 221... Cap, 221 a .. lens, 222 .. stem, 223 a to 223 d .. through hole, 231 a to 231 e. Terminals, 241 ... mount substrate, 243 ... light receiving element, 244 ... first conductor layer, 244a to 244e ... connection pattern, 244as, 244at ... stub, 246, 248, 255de・Dielectric layer, 247 ... second conductor layer, 247a, 249a ... ground layer, 249 ... third conductor layer, 250 ... electrode support, 251 ... electrode plate

Claims (7)

A mounting substrate on which a light emitting element or a light receiving element is mounting location,
Wherein formed on the mounting board, placed on said differential signal for driving the light emitting element or the first and second connection for transmitting a differential signal generated by the placed light receiving element, With patterns,
Have
In the light emitting element or the light receiving element placed above, one electrode is electrically connected to the first connection pattern, and the other electrode is electrically connected to the second connection pattern by a bonding wire,
An optical device in which a stub for correcting a phase difference between signals of any one of the differential signals is formed in the second connection pattern . On the stub optical device according to claim 1 in which the capacity of the stub provided capacity varying means for varying and adjustable phase between the signals of the one of the differential signal by the variable capacity means. The optical device according to claim 2 , wherein the capacity varying unit is configured using a device of a micro electro mechanical system. A transmission / reception processing board on which a circuit is mounted;
An optical device connected to the transmission / reception processing board;
With
The optical device is:
A mounting substrate on which a light emitting element or a light receiving element is mounted;
A plurality of terminals electrically connected to the transmission / reception processing board;
The light emitting element formed and placed on the mount substrate for connecting two electrodes of the light emitting element or light receiving element placed on the mount substrate to two of the plurality of terminals. differential signal for driving, or the first and second connection patterns for transmitting the differential signal generated by the placed light receiving element,
Have
In the light emitting element or the light receiving element placed above, one electrode is electrically connected to the first connection pattern, and the other electrode is electrically connected to the second connection pattern by a bonding wire,
An optical communication apparatus , wherein a stub for correcting a phase difference between any of the differential signals is formed in the second connection pattern . The optical communication apparatus according to claim 4 , wherein a capacitance variable unit that varies a capacitance of the stub is provided on the stub, and the phase between any of the differential signals can be adjusted by the capacitance variable unit. The light emitting element that is electrically connected to the first and second connection patterns and a light receiving element that detects an emission level of light from the light emitting element are mounted on the mount substrate,
In accordance with a detection result of a light receiving element that detects an emission level of light from the light emitting element , the capacitance variable means is controlled by a circuit mounted on the transmission / reception processing board, whereby the difference supplied to the light emitting element The optical communication device according to claim 5 , wherein a phase difference between the signals of the motion signal is corrected. Depending on the emission level of the light from the light emitting element indicated by the detection result, to obtain a flat pass characteristic with respect to the frequency of how to control the electrical length corresponding to the first and second connection patterns Control information is stored in a control circuit mounted on the transmission / reception processing board,
Wherein the control circuit, based on the control information, by controlling the control signal of the variable volume means, according to claim 6 for correcting the phase difference between the signals of the differential signal supplied to the light emitting element Optical communication device.

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