JP4146211B2 - Optical module, optical switch constituting the same, and optical matrix switch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is an optical module that can be applied to an optical communication system and whose output characteristics are controlled by electricity, an optical switch constituting the optical module, and an optical matrixOn the switchRelated.
[0002]
[Prior art]
While the increase in capacity of optical communication has progressed and the transmission capacity has been increased by the WDM (wavelength division multiplexing) system, an increase in the throughput of the path switching function in the node is strongly demanded. The path switching is currently performed by an electrical switch after converting the transmitted optical signal to an electrical signal, but in order to take advantage of the characteristics of the optical signal that is high speed and wideband, an optical switch is used to switch the path. It is necessary to reduce the size and power consumption of the node device by switching the path with the signal. As a specific system using such an optical switch, an optical cross-connect or an optical add / drop multiplexing system is required to be realized, and an optical switch is required as a key device.
[0003]
A conventional example of such an optical switch is shown in FIG. The upper part of the drawing in FIG. 9 is a substrate of a 1 × 128 optical switch 901 using the thermo-optic effect of a quartz lightwave circuit (PLC), and the lower part of the drawing is the lower part of the drawing. This is an electric wiring board 921 on which an IC (integrated circuit) 925 for driving the optical switch is mounted, and both constitute a 1 × 128 optical switch module.
[0004]
As for the PLC board, a unit optical switch with two inputs and two outputs is used as a 1 × 2 optical switch 903 as shown in the figure, and a plurality of 1 × 2 optical switches 903 are used in a 7-stage tree shape to obtain 1 × 128 optical matrix switches are formed on the same substrate (see Non-Patent Document 1).
[0005]
There are various construction methods for the 1 × 2 optical switch 903 in FIG. 9, but in a quartz-based PLC, two arm waveguides having a thermo-optic phase shifter (thin film heater) 1007 as shown in FIG. 10. A Mach-Zehnder interferometer type 2 × 2 optical switch (MZI optical switch) in which both ends of 1001 are connected by two 3 dB couplers 1003 and 1009 is used. In the 1 × 2 optical switch used in the present invention, for example, 61b is an unconnected waveguide. In this MZI optical switch, two arm waveguides 1001 having the same length are symmetric MZI optical switches, and two arm waveguides 1001 are provided with a half-wavelength optical path length difference. We will call it a switch here.
[0006]
In the symmetric MZI optical switch, when the thermo-optic phase shifter 1007 is not driven (energized), the light propagates in the cross path (61a → 62b) according to a known interference principle, and the thermo-optic phase shifter 1007 is driven to perform thermo-optics. When the optical path length difference of half wavelength is given due to the effect, it propagates in the bar path (61a → 62a).
[0007]
Further, when the drive amount to the thermo-optic heater 1007 is adjusted to continuously change the optical path length difference between the two arm waveguides 1001 from zero to a half wavelength, the optical path is continuously changed from the cross path to the bar path. Change. That is, it operates not only as an ON / OFF switch but also as an analog switch. Therefore, the MZI optical switch can be operated as an attenuator by adjusting the distribution ratio between the cross path and the bar path, or can be operated as a branching unit that performs multicasting or broadcasting as necessary.
[0008]
By configuring this basic optical switch shown in FIG. 10 in a tree shape as shown in FIG. 9, a 1 × 128 optical switch 901 can be realized. Note that a gate optical switch 905 is added to the eighth stage in FIG. 9 to increase the extinction ratio.
[0009]
As the gate optical switch 905, an asymmetric MZI optical switch is used. In this asymmetric type MZI optical switch, when the thermo-optic phase shifter 1007 is not driven (energized), light propagates in the bar path (61a → 62a), drives the thermo-optic phase shifter, and the half-wavelength due to the thermo-optic effect. When the difference in optical path length is canceled, the light propagates through the cross path (61a → 62b). This asymmetric MZI optical switch is known to have less crosstalk in the cross path, and normally, the gate optical switch transmits light through only one port and the other ports block light. Many. Therefore, a cross-port with a higher extinction ratio can be used for the gate optical switch 905 when this asymmetric optical switch is used, and power consumption can be saved.
[0010]
Thermo-optic switches using quartz waveguides combine glass film deposition techniques such as flame deposition (FHD) and chemical vapor deposition (CVD) with microfabrication techniques such as reactive ion etching (RIE). Produced. Specifically, on a substrate 1015 such as a silicon wafer, a glass film to be a lower cladding layer is first deposited, and then a core layer having a refractive index slightly higher than that of the cladding layer is deposited. Then, the core pattern 1011 to be an optical circuit is patterned by a microfabrication technique, and subsequently a glass film to be the upper clad layer 1013 is deposited. Finally, a thin film heater 1007 to be a thermo-optic phase shifter and wiring for supplying power thereto 1005 is formed to produce an optical switch chip. A power supply line and an optical fiber are connected to the optical switch chip, and the optical switch module is completed by storing it in a case with a radiation fin.
[0011]
An electric drive circuit of the heater 1007 is shown in FIG. As shown in the figure, a driving analog power supply circuit 1101 is connected to the heater of one arm of the MZI of each 1 × 2 optical switch 903 so that an optimum voltage (current) for driving the MZI is obtained. The electrical digital switch 1103 is connected to the opposite side of the heater, and the electrical digital switch 1103 is turned on / off in response to the on / off of the optical switch 903. Since there are 255 1 × 2 optical switches 903, there are 255 drive power supply circuits 1101 and 255 electric digital switches 1103, respectively.
[0012]
In the actually manufactured 1 × 128 optical switch, excellent characteristics of an average insertion loss of 0.4 dB and an average on / off extinction ratio of 40 dB were obtained.
[0013]
Although an example of an optical switch has been described above, a variable optical attenuator can be similarly configured by using the same MZI optical switch and changing the amount of phase change in an analog manner. Is actually made. The variable optical attenuator is an essential device for equalizing the light intensity of each wavelength of the wavelength-multiplexed signal light, and has recently been in high demand.
[0014]
Other high-demand optical circuits, such as dispersion compensators, polarization dispersion compensation circuits, or gain equalizers, can be realized with MZI optical switches and circuits that combine phase shifters and optical waveguides as described above. It is.
[0015]
[Non-Patent Document 1]
T. Watanabe et. Al., "Silica-based PLC 1 × 128 thermo-optic switch," Proc. 27^th ECOC '01, Tu.L.1,2, Amsterdam, 2001
[0016]
[Problems to be solved by the invention]
The problem of the present invention will be described below using the 1 × 128 PLC thermo-optic switch (PLC-TOSW) shown in FIG. 9 as an example. This 1 × 128 PLC thermo-optic switch has the following problems.
(1) The area of the electric wiring part in the PLC substrate is enlarged.
(2) A large number of driving analog power supply circuits are required. In the above example, as described above, as many as 255 power supply circuits are required.
(3) The number of wire bondings between the PLC substrate and the driving IC mounting substrate increases. In the example of FIG. 9, 255 electrode pads 911 and 915 and 255 electrode pads for connection to the upper drive circuit are required, for a total of 510 electrode pads.
(4) A prober having a considerably large number of pins is required for the inspection process, and accordingly, a highly accurate prober aligning device is required.
[0017]
Hereinafter, it demonstrates in order.
(1) In FIG. 9, there are 255 thermo-optic phase shifters (heaters) to be driven on the substrate, and both ends thereof are connected to wire electrode pads 911 on the substrate end by gold wirings 907 and 909. Therefore, as many as 255 gold wirings 907 and 909 need to be laid out on the substrate without crossing, and the area of the electrical wiring is greatly increased as the scale of the optical circuit increases and the number of channels increases.
[0018]
This electric wiring area is estimated quantitatively. Ta₂The gold wiring for driving the N-film heater is preferably a gold thin-layer wiring considering the patterning on the optical waveguide substrate where warpage or the like exists, and the amount of current necessary for driving the heater is reduced. Considering the width, it is desirable that the width is about 50 μm. It is desirable that the gap between the wirings is about 50 μm. If the area required for the development of the electrical wiring is estimated under these conditions, the wiring width is 51.2 mm with 510 wirings. In the example of FIG. 9, the substrate size is 60 mm × 60 mm, and the wiring length when it is routed to the end of the substrate is an average of 4 cm. Therefore, the area of the electric wiring portion from the heater to the digital switch side is 20 cm.²It becomes. Using a core with a small allowable bending radius suitable for miniaturization and a clad having a relative refractive index difference of 1.5%, the area of the optical circuit itself is 20 mm × 60 mm = 12 cm.²It is downsized. Since the optical circuit and the electrical wiring itself can intersect, the downsizing of the PLC optical switch substrate is limited by the area of the electrical wiring portion.
[0019]
(2) In the example of the 1 × 128 PLC thermo-optic switch in FIG. 9, there are 255 thermo-optic phase shifters (heaters) to be driven on the substrate. Therefore, as many as 255 driving (power supply) circuits are required.
[0020]
(3) In (1), the 510 wires on the PLC board need to be individually connected to the drive circuit 925 mounted on another board. Here, the connection between the substrates is usually performed by wire bonding. If the wire bonding electrodes 911 and 915 are 150 μm wide and the gap is 50 μm, the pitch is 200 μm, and if the number of wire bonding is 510, the width is as long as 104 mm.
[0021]
Here, as a method of fixing the PLC substrate and the electronic circuit mounting substrate, a method of sticking the PLC substrate on a substrate including a larger electronic circuit, or a method of arranging the PLC substrate and the electronic circuit substrate side by side on the third substrate. There is. Regardless of which method is used, wire bonding is performed at 200 ° C., for example, and therefore, there is a possibility that stress is applied to the wire 913 due to the difference in contraction due to the difference in thermal expansion coefficient of each substrate and the reliability is impaired. .
[0022]
(4) Furthermore, in the process of actually producing the module, an inspection process for evaluating the optical characteristics and electrical characteristics by driving the heater by contacting an electrode prober from the outside at the stage of the PLC substrate is essential. is there. For this evaluation, in the conventional example, it is necessary to contact the electric prober with 510 electrode pads at the same time, and a special and expensive electric prober and a aligning device capable of contacting the electrode pad in parallel with high accuracy are required. It was.
[0023]
The problems of the optical module in which the driving electric circuit and the optical circuit are electrically connected have been listed by taking the 1 × 128 optical switch as an example. This problem is caused by the fact that the optical circuits and electrical circuits that have been increased in scale and multi-channel (multi-port) have not been optimized as a whole. For example, in the above example, the electrical circuit is optimized even though a large number of heaters that are to be driven by the electrical circuit on the optical waveguide substrate are arranged in widely dispersed locations due to circumstances specific to the optical circuit. Due to not being. A similar situation exists in optical circuits other than the 1 × N optical switch, and is a problem common to optical modules whose output characteristics are controlled by electricity. For example, a similar problem exists in an N × N matrix optical switch, a variable optical attenuator and its array module, a dispersion compensation circuit, and a gain equalization circuit.
[0024]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to reduce the area of an electric wiring portion on a substrate in an optical module in which a driving electric circuit and an optical waveguide circuit are electrically connected. By reducing the number of connecting wires from the PLC board to the outside and reducing the number of analog drive circuits, the optical waveguide board can be downsized, and the number of gold wires between boards where reliability is a concern can be greatly reduced. The object is to eliminate the need for an IC mounting substrate for driving an optical switch or an optical variable attenuator, to reduce the module size, and to simplify the characteristic evaluation by reducing the electrode terminals of the prober.
[0025]
It is a further object of the present invention to provide an optical switch and an optical matrix suitable for such an optical module.
[0032]
[Means for Solving the Problems]
  To achieve the above object, an optical switch according to the present invention is an optical module comprising an optical switch and a plurality of electronic circuits for driving for changing the output characteristics by changing the refractive index of the optical switch. The driving electronic circuit is connected to the optical switch together with the optical switch.One input waveguide fabricated on a substrate, N (N is an integer greater than or equal to 3) output waveguides, and a plurality of 1 × 2 optical switches connecting the input waveguides and the output waveguides The 1 × N optical switch is provided with a gate optical switch capable of transmitting, blocking, or changing light intensity in the output waveguide.AboveAn analog optical switch whose path is continuously switched by an electric signal level controlled by an electronic circuit for driving, and the analog optical switch includes an electric digital switch for cutting off the electric signal level from the electronic circuit for driving ,The driving electronic circuit is shared by the plurality of 1 × 2 optical switches such that the number of the driving electronic circuits is smaller than the number of the 1 × 2 optical switches, When the 1 × N optical switch performs a switching operation, only one of the 1 × 2 optical switches in each stage is driven, and wiring connecting from the analog driving power source to the 1 × N optical switch is a substrate of the optical switch. In the above, each stage of the 1 × N optical switch is aggregated and shared by one,The electrical digital switch is integrated by an electronic integrated circuit manufacturing process.
[0033]
The optical matrix switch of the present invention isAn optical module comprising an optical switch and a plurality of electronic circuits for driving for changing the output characteristics by changing the refractive index of the optical switch, the electronic circuit for driving together with the optical switch and the optical switch SwitchIt consists of M (M is an integer greater than or equal to 2) input waveguides, N (N is an integer greater than or equal to 2) output waveguides, and M × N optical crosspoint switches fabricated on a substrate. , N) No. optical crosspoint switch is an optical crosspoint switch that connects the mth input waveguide and the nth output waveguide (where 1 ≦ m ≦ M, 1 ≦ n ≦ N) The optical cross point switch is a double optical switch composed of a 1 × 2 optical switch, a 2 × 1 optical switch, and a waveguide in the optical cross point switch unit, the 1 × 2 optical switch and the 2 × 1 Optical switchAboveAnalog optical switch whose path is continuously switched by the electric signal level controlled by the driving electronic circuit.InThe analog optical switch includes an electric digital switch for cutting off an electric signal level from the driving electronic circuit;The electronic circuit for the drive circuit is shared by the plurality of dual optical switches so that the number of electronic circuits for the drive circuit is smaller than the number of the dual optical switches. When the optical cross point switch performs a switching operation, only one of the dual optical switches grouped for each input waveguide is driven and connected to the dual optical switch from an analog driving power source. The wiring is divided into two parts, a 1 × 2 optical switch group and a 2 × 1 optical switch group constituting the grouped dual optical switch, and each is separately integrated on the optical switch substrate. SharedIt is characterized by that.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Before describing individual embodiments of the present invention, first, a basic configuration common to each embodiment of the present invention will be described below with reference to the drawings.
[0035]
(Basic configuration)
With respect to the electric circuit for driving the heater shown in FIG. 9, the present inventors have found that the basic optical switch that is turned on when the optical switch is in operation does not exist at random, but obeys certain constraints, and By arranging the constraints, we have newly found that even if the drive power supply circuit is integrated into several circuits and used in common, the degree of freedom is not impaired at all or almost.
[0036]
Here, an example of a 1 × N optical switch tree-type shared drive power supply will be described. Assuming that the 1 × N optical switch is configured in a tree-type and n stages using the 1 × 2 optical switch as a basic switch, an arbitrary a-stage (1 ≦ a ≦ n) basic switch (for example, 3 in the third stage) -1, 3-2, 3-3, and 3-4), there is only one basic optical switch that is in the current drive state (ON state), and there is a certain output waveguide Of the N gate optical switches on the road, only one is in the current drive state (ON state).
[0037]
Here, when the 1 × 2 optical switch is an MZI optical switch circuit as shown in FIG. 10, an example of an electric circuit for driving the circuit is as shown in FIG. As shown in FIG. 11, a driving power source (driving circuit) 1101 capable of analog output is provided at one end of the electric wiring of the heater 1007, and an electric digital switch 1103 is connected to the other end. The analog power supply circuit 1101 is set in advance to an optimum driving voltage for each optical switch 903. On the other hand, the electric digital switch 1103 uses an IC (integrated circuit) in which a large number of transistor circuits are integrated, and performs a conduction / cut-off (ON / OFF) operation in response to a TTL level input. Here, as shown in the example of the 1 × 8 optical switch in FIG. 12, the analog drive circuit 1101 is shared by the optical switches 903 in each stage.
[0038]
FIG. 13 shows a more detailed circuit configuration of FIG. As shown in the figure, even if the analog drive circuit 1301 is shared, only one unit is in the ON state at each stage at the same time. Therefore, the analog drive circuit 1301 is individually adjusted to the optical switch 903. There is no loss of the individual adjustment function that can be applied. By performing this sharing on the PLC substrate, the area of the electric wiring portion on the substrate can be reduced, the number of connection wires from the PLC substrate to the outside can be reduced, and the analog drive circuit can be reduced.
[0039]
However, with the recent increase in the scale of optical switches, there is an increasing need for further reduction in size by reducing the electrical wiring on the substrate. Therefore, returning to the example of the 1 × 128 optical switch in FIG. In FIG. 9, the driving signal feeding line 907 on the upper side of the figure is connected to the analog driving circuit 1101 on the analog feeding side, and the heater driving wiring 923 on the lower side of the figure is connected to the electric digital switch 1103. . The analog power supply side can be shared at each stage according to the sharing described above with reference to FIGS.
[0040]
  On the other hand, the electric digital switch side is conventionally connected to the external substrate 921 and the wire 913 at the gold wire electrode pads 911 and 915 after being individually routed to the substrate end by the gold wiring 909 and connected to the driving IC 925. Yes. In the present invention, the electric circuit including the IC 925 is configured as shown in FIG. In the tree type 1 × 128 optical switch 901 in FIG. 9, there are 255 unit optical switches 903 (indicated by # 1 to # 255 in FIG. 14). Four 64-bit driving ICs 925-1 to 925-4 are connected to each heater 1107 of the unit optical switch 903 as shown in FIG. 14. These driving ICs 925-1 to 925-4 are CMOS LSIs (CMOS large-scale integrated circuits) incorporating a shift register (not shown) and a latch (not shown), and the above-mentioned digital switch 1103 and signal / parallel. It has both functions of a conversion circuit (not shown). The driving ICs 925-1 to 925-4 are connected in cascade as shown in FIG.MultistageBy connecting), they can be synchronized with each other and expanded to 64 bits × 4 = 256 bits.
[0041]
For the driving ICs 925-1 to 925-4, as shown in FIG. 15, by using a 1 MHz clock signal and assigning on / off of the output to each heater 1107 to each time axis for each clock, The ON / OFF operation of each gate (905 in FIG. 9) is realized within a latch pulse of 0.26 ms. The switching speed of the thermo-optic switch is 2 ms, for example, which is sufficiently slow compared to the clock signal. Therefore, on the relationship between input and output, it is possible to control the on / off of 256 heaters 1107 with three input signals. It becomes.
[0042]
In the example of FIG. 15, an example in which the clock speed is 1 MHz is given. However, if the clock speed is increased 10 times, 2,560 heaters can be easily latched and switched every 0.26 ms. As described above, it is possible to control many heaters by appropriately selecting the clock speed.
[0043]
Further, in the present invention, as will be described later with reference to FIG. 1, the driving ICs 925-1 to 925-4 are placed on the PLC substrate while keeping the small bare chip (the size is, for example, 2 mm × 7 mm). Since it is mounted, the wiring between the heater and the IC on the PLC substrate can be integrated, and 255 wirings can be integrated into only three signal lines. For this reason, the area of the electrical wiring is greatly reduced, and the area of the PLC substrate can be reduced.
[0044]
Furthermore, in the present invention, since the driving IC is mounted on the PLC board, the number of wirings to be taken out from the PLC board is greatly reduced to 20. As a result, the number of wires between the PLC board and the electric circuit board on which the electric drive circuit is mounted is also 20, and the number of wire bonding can be greatly reduced from 510 to 20.
[0045]
In the present invention, the module is greatly reduced in size by eliminating the driving IC mounting substrate.
[0046]
Furthermore, in the present invention, since the driving IC is mounted on the PLC board, the number of blower electrodes when inspecting at the level of the PLC board before manufacturing the module is reduced from 510 to 20 in the manufacturing process. It is possible to simplify the prober and the apparatus used for alignment.
[0047]
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0048]
(First embodiment)
FIG. 1 shows the structure of an optical module according to the first embodiment of the present invention. This embodiment is an example of a 1 × 128 PLC thermo-optic switch according to the present invention in which a driving IC is mounted on a PLC substrate. For simplification of the drawing, the wiring of the basic optical switches after the fourth stage is omitted. Here, 101 is a 1 × 128 PLC thermo-optic switch (1 × 128 optical switch), 103 is a 1 × 2 optical switch, 104 is an optical waveguide, 105 is a gate optical switch, 107 is a gold wire for driving a heater, 109 is a basic switch A driving IC (bare chip), 111 is a control signal gold wiring, 113 is an electrode pad, 115 is a gold wire, 117 is an electrode pad, and 119 is a driving signal feeding line (feeding line for driving power supply circuit).
[0049]
The configuration of the 1 × 2 optical switch 103 and the optical waveguide 104 in the present embodiment is the same as the configuration of FIG. 10 described above. In the 1 × 128 PLC thermo-optic switch 101, an optical waveguide 104 is formed on a Si substrate by a flame deposition method, and the MZI circuit of the 1 × 2 optical switch 103 is formed with the structure shown in FIG. And as heater 1007, Ta₂The N film is formed in a pattern, and a patterned gold thin film is used for the electric wiring 1005 for routing the N film on the Si substrate.
[0050]
The configuration of this embodiment is different from the conventional example in the following electrical wiring structure. That is, as shown in FIG. 1, the feeder line 119 for the drive power supply circuit is shared on the PLC substrate to reduce the electrical wiring area, and the heater drive IC 109 is mounted on the PLC substrate as a bare chip. .
[0051]
In the heater driving IC bare chip 109, as shown in the enlarged detail view of FIG. 2, the electrode pads 201 and 202 are fixed upward on the PLC substrate. One electrode pad 201 is an electrode pad connected to the heater of the basic optical switch 103. The other electrode pad 202 is an electrode pad connected to the gate control signal, and is a GND terminal, a clock terminal, a latch terminal, and a signal terminal from the left in FIG. A gold thin film wiring 111 is drawn out from the latter electrode pad 202.
[0052]
Then, the electrode pads 201 and 202 on the PLC substrate and the electrode pads 203 and 204 on the heater driving IC 109 are connected by gold wires 205 and 206. Further, the IC 109 and the gold wires 205 and 206 are sealed with a silicone resin (not shown) to improve reliability. Such an IC bare chip mounting form itself is generally used in an electric wiring board, and reliability is ensured unlike wire bonding between boards as shown in FIG.
[0053]
It should be noted here that in an optical waveguide circuit board of a large-scale optical switch, it is necessary to disperse and arrange a large number of hundreds of phase shifters (heaters) over a wide area on the optical waveguide circuit board. Is that there is. However, it is very difficult to produce a fine electric wiring process on the optical waveguide circuit board, and the drive electric circuit of these phase shifters (heaters) is placed on the same substrate (optical waveguide circuit board). Manufacturing is a new problem different from manufacturing a conventional electric circuit and integrated circuit, and is a new problem.
[0054]
This new problem has been solved by mounting the gates of the driving ICs on the Si substrate and grouping (sharing) them as shown in FIG. 14 and FIG. Note that it is not simply that the driving IC is mounted on the Si substrate. For reference, there has been no report on an example in which an optical switch driving IC or control IC is mounted on a PLC board.
[0055]
The drive circuit using this IC is as already described with reference to FIGS. 13 to 15, and 256 heaters 1107 are driven simultaneously by three heater control signals of clock, latch, and signal (data). Can do.
[0056]
In the present embodiment, the following effects can be obtained by adopting the configuration described above.
(1) Reduction of the area of electrical wiring in the PLC board
(2) Reduction in module size by eliminating the need for an IC mounting board
(3) Reduction of the number of wire bondings between the PLC board and the electronic circuit board
(4) Simplification of inspection process
[0057]
Hereinafter, it demonstrates in order.
(1) Reduction of the area of electrical wiring in the PLC board
In the conventional example as shown in FIG. 9, since it is necessary to route all the heater driving gold wirings to the electrode pads on the substrate end, the area of the electrical wiring portion is increased by the amount of routing, and the entire substrate is enlarged. On the other hand, in the present embodiment shown in FIG. 1, the driving IC gates are mounted on the Si substrate and grouped, so that 255 heater wirings are routed to the driving ICs arranged in the immediate vicinity ( Short distance), the area of the electrical wiring on the PLC substrate is greatly reduced.
[0058]
This reduction in wiring area is estimated quantitatively. Ta₂For example, a maximum current of 60 mA needs to flow through the N film heater. For this purpose, it is desirable that the gold wiring has a width of about 50 [mu] m in consideration of patterning into an optical waveguide substrate that is more difficult to manufacture than a Si substrate having a warp rate. The gap between wirings must be 50 μm. If the area required for the electric wiring development is estimated under these conditions, the total wiring width of 256 wirings is 25.6 mm. As a typical example, if the wiring length from each heater to the heater driving IC is 15 mm on average and the wiring length when the heater driving gold wiring is routed to the end of the substrate without using the heater driving IC is 60 mm on average, The area of the electrical wiring part on the switch side is 1/4.
[0059]
Since this reduction in the area of the electrical wiring is independent of the effects (2) and (3) above, the layout of the IC should be such that the area of the electrical wiring is minimized or the wiring is minimized. The heater driving IC 109 may be arranged on the optical waveguide substrate so as to achieve this.
[0060]
1 and FIG. 9 are schematic diagrams, and the detailed electrical wiring layout is too fine to describe, but the area of the optical waveguide substrate of the conventional 1 × 128 optical switch shown in FIG. 9 is 57 mm × 60 mm. Therefore, as described above, the downsizing of the PLC substrate is limited by the electric wiring portion. On the other hand, in the present embodiment, the area of the electric wiring portion can be reduced to ¼, whereby the PLC substrate can be reduced to 30 mm × 60 mm.
[0061]
(2) Reduction in module size by eliminating the need for an IC mounting board
As a matter of course, since the heater driving IC is mounted on the PLC board, the module size is reduced only in the IC mounting board portion.
[0062]
(3) Reduction of the number of wire bondings between the PLC board and the electronic circuit board
In this embodiment, since the heater driving IC is mounted on the PLC substrate, the number of wire bondings between the substrates can be greatly reduced. In this example, the number of wires between the substrates is about 510 in the conventional example, but in this embodiment, 3 signal lines and 17 other power lines are added to drastically reduce to 20 in total. To do. With this number of about 20, the wire connection between the substrates spreads over a width of several tens mm or more unlike the conventional example, and there is no concern about reliability. In the present embodiment, the area for wire bonding is reduced to a width of 2.8 mm, or it is possible to connect them individually with a cable or the like without using a wire, so there is no problem with wire bonding.
[0063]
(4) Simplification of inspection process
Further, also in the present embodiment, in the process of actually producing a module, there is a process of inspecting whether or not a product having a desired characteristic is formed by driving an electric prober from the outside at the stage of the PLC board. It is essential. In the conventional example, it is necessary to simultaneously contact the 510 electrode pads with the electric prober. Therefore, a special and expensive electric prober and a aligning device capable of contacting the electric prober with high parallelism are required. On the other hand, in the present embodiment shown in FIG. 1, the number of electrode pads to be contacted is greatly reduced to 14, so that an inexpensive electric prober can be easily in contact with the electrode pads and inspected. The cost and working time of necessary members and devices can be greatly reduced.
[0064]
To summarize the above description, in this embodiment, the IC for driving the optical switch is directly mounted on the PLC substrate with a bare chip, so that the routing of the electric wiring part is greatly reduced, the PLC substrate is downsized, and the space between the substrates is reduced. The number of gold wires can be greatly reduced from 256 to 14 and the yield reliability can be improved. Further, in the present embodiment, the module size can be further reduced by the amount that the driving IC mounting substrate becomes unnecessary. In addition, the prober and apparatus required for the inspection process are simplified, and cost reduction and work time can be reduced.
[0065]
Further, not only one large-scale switch as shown in FIG. 1, but also an 8 × 2 optical switch array used in, for example, an optical add / drop multiplexer / demultiplexer is integrated on the same PLC substrate. Even if the present invention is applied, the same effect as described above can be obtained. FIG. 3 shows an example of the configuration. In FIG. 3, the electrical wiring between the basic optical switch 103 and the IC 109 is omitted for simplification of the drawing.
[0066]
Also, the same effects as described above can be obtained by applying the present invention to the variable optical attenuator, its array module, dispersion compensation circuit, and gain equalization circuit.
[0067]
Further, the present invention can be similarly applied to an optical switch using an optical circuit other than the PLC substrate, and it goes without saying that the same effect as that of the PLC substrate can be obtained. For example, LiNbO₃Even in an optical switch using an (LN) optical waveguide, by applying the present invention, it is possible to obtain the same effect as in the case of a PLC substrate.
[0068]
(Second Embodiment)
FIG. 4 shows the configuration of a 4 × 4 optical matrix switch according to the second embodiment of the present invention. In the 4 × 4 optical matrix switch 401, four input waveguides 407 and four output waveguides 409 intersect at 16 points in a lattice shape, and a double-type optical crosspoint switch 411 is provided at each of the intersections. It has been placed.
[0069]
FIG. 5 shows an enlarged view of the double type optical cross point switch 411. An intra-unit waveguide 421 is connected between the 1 × 2 optical switch 415 and the 2 × 1 optical switch 416 constituting the double type optical crosspoint switch 411. As shown in FIG. 4, four drive signal feed lines 403 in the vertical direction respectively connect the 1 × 2 optical switch 415 and the shared drive (power supply) circuit for the 1 × 2 optical switch in each line. . Also, four drive signal power supply lines 405 in the horizontal direction connect between the 2 × 1 optical switch 416 and the shared drive (power supply) circuit for the 2 × 1 optical switch, respectively.
[0070]
Specific configurations of the double type optical cross point switch 411 and the electric control circuit are shown in FIG. In the figure, 401 is an optical matrix chip, 411 is a dual optical switch unit, 601 is a shared drive (analog power) circuit for the 1 × 2 optical switch, and 602 is a shared drive (analog) for the 2 × 1 optical switch. A power supply circuit 603 is an electric digital switch.
[0071]
As the 1 × 2 optical switch 415 and the 2 × 1 optical switch 416 constituting the double type optical crosspoint switch 411, MZI optical switches provided with a half-wavelength optical path length difference are used as in the prior art. In each MZI optical switch, electrical wiring is connected to thermo-optic heaters 617 and 618 on an arm waveguide having a short optical path length. An electrical digital switch 603 is connected to one of the electrical wirings, and drive power supplies (drive circuits) 601 and 602 capable of analog output are connected to the other. The electric digital switch 603 uses an IC in which a large number of transistor circuits are integrated, and performs a conduction / cut-off (ON / OFF) operation in response to a TTL level input.
[0072]
As shown in FIG. 4 and FIG.
(1) The analog drive circuit is shared for each output waveguide for the 1 × 2 optical switch, and shared for each input waveguide for the 2 × 1 optical switch, and
(2) The heater driving IC is mounted on the PLC substrate as a bare chip.
[0073]
Next, this will be described.
With reference to FIGS. 4 and 5, the sharing of the analog drive circuit (1) will be described first. Four optical crosspoint switches SW in the shared drive circuit 1a_{x, 1}; 1 × 2 optical switches with x = 1 to 4 are connected in parallel, and SW is similarly switched to 2a to 3a_{x, 2}~ SW_{x, 4}Are connected in parallel. The shared drive circuit 1b includes four optical crosspoint switches SW._{1, y}; 2 × 1 optical switches with y = 1 to 4 are connected in parallel, and similarly SW to 2b to 3b_{2, y}~ SW_{4, y}Are connected in parallel.
[0074]
Thereby, the number of drive circuits can be reduced from 16 at the time of individual connection to 8. In addition, since the wiring to the drive circuit is partially shared for each shared drive circuit, the wiring area is reduced and the electrical connection terminals from the switch chip are also reduced.
[0075]
Further, (2) the heater driving IC 109 is mounted on the PLC substrate with a bare chip, which is different from the conventional example. The mounting form is as described in FIG. In FIG. 4, the IC bare chip 109 and 32 MZI circuits each are connected by heater driving wirings, and the MZI circuit is turned on / off as the electric digital switch 603. Also in the N × N matrix switch, the same effects as described in detail in the items (1) to (4) in the first embodiment are produced as in the first embodiment. For example, there are 32 electrical digital switches 603 corresponding to 32 optical crosspoints, but the distance between the heaters 618 to IC109 is integrated into 3 in the IC, so the area of the electrical wiring section is reduced. The number of wires between the substrates is also reduced. Although the 4 × 4 matrix switch has been described here, such a reduction effect becomes more significant as the scale of the optical matrix switch chip is larger.
[0076]
For the two 3 dB couplers (see 1003 and 1007 in FIG. 10) in the MZI optical switch this time, directional couplers having two waveguides close to several μm were used. This is because the directional coupler has a lower insertion loss than other means. However, the 3 dB coupler is not limited to this configuration, and is configured by other means, for example, a multimode interferometer (MZI) coupler using a multimode waveguide or a plurality of these couplers connected in cascade. Of course, a wavelength independent coupler (WINC) may be used.
[0077]
    (Third embodiment)
  FIG. 7 illustrates a transmission module including a variable optical attenuator using an MZI circuit formed on a quartz-based PLC substrate as a third embodiment of the present invention. In this transmission module, a plurality of LD elements 701 for WDM signals are arranged on the left side of FIG.₁~ Λ_NMach-Zehnder type using an MZI circuit made of silica-based PLC that is connected to the output side of the LD element 701 via an optical fiber 703.Variable lightThe array module of the attenuator 707 is formed on the PLC substrate 705, and theVariable lightThere is a PLC substrate including an arrayed waveguide grating (AWG) 717 connected to the output side of the attenuator 707 via an optical fiber 715 (optical waveguides such as AWG are omitted and not shown).
[0078]
In the MZI circuit, an IC 709 for driving the variable optical attenuator 707 is mounted on the same substrate with a bare chip. Here, 711 is a gold wiring for driving the heater, and 713 is a gold wiring for driving the IC. This variable optical attenuator 707 is obtained by operating the above-described MZI circuit (Mach-Zehnder interference type optical switch) of FIG. 10 with an analog continuous current. However, the driving IC 709 controls not only the mere gate SW (switch) but also the amount of current that flows to the variable optical attenuator 707, and the analog amount of current is determined by a separate control signal that digitizes the amount of current to flow. I have control. The IC used for this control may be a single IC or a combination of a plurality of ICs as long as the variable optical attenuator 707 can be analog-controlled as a result. Also in the PLC substrate 705 including such a variable optical attenuator 707, the electrical wiring on the substrate is integrated into an IC mounted in the same manner as in the first embodiment, and in the first embodiment (1 ) To (4) have the same effects as listed.
[0079]
In the present embodiment, a variable optical attenuator using a silica-based PLC has been described as an example. However, the present invention can be similarly applied to optical waveguide circuits made of other materials. Of course, the type of optical circuit is not MZI, but it is of course possible to use, for example, a Y branch.
[0080]
(Fourth embodiment)
FIG. 8 shows, as a fourth embodiment of the present invention, a PLC-LN type optical switch manufactured by end-bonding a PLC substrate and an LN optical waveguide substrate, from an optical signal having multiple wavelengths. The wavelength selector which selects arbitrary wavelengths is illustrated. In FIG. 8, 801 is a first PLC substrate including an arrayed waveguide grating, and 803 is a second LiNbO.₃The (LN) substrate 805 is a third PLC substrate including an arrayed waveguide grating, and these three substrates are end-face bonded in this order by a bonding means such as an adhesive. Reference numeral 809 denotes a driving IC mounted on the second LN substrate 803, and 811 denotes LiNbO formed on the LN substrate 803.₃An optical waveguide, 813 is a heater driving gold wiring, and 815 is an IC control gold wiring.
[0081]
In this embodiment, an arrayed waveguide grating (AWG) is used for the PLC substrates 801 and 805 (optical waveguides such as AWG are omitted and not shown), and the MZI circuit 807 includes a coupler and an LN substrate on the PLC substrate 801. And an LN optical waveguide 811 on 803. Then, the phase change corresponding to the half wavelength necessary for the optical switch operation is given by the electro-optic effect due to the voltage applied to the heater on the LN optical waveguide 811. In this example, the MZI optical switch is used as an ON / OFF type optical gate switch.
[0082]
An N wavelength WDM signal (wavelength; λ) input from the optical input port on the left side of FIG.₁, Λ₂, Λ₃, ... λ_N) Is divided into each wavelength by the AWG on the first PLC substrate 801. Subsequently, each desired wavelength is selected by a gate switch by the MZI circuit 807 on the second substrate 803 at the center. Subsequently, the selected one or more wavelengths are multiplexed again by the output AWG on the third PLC substrate 805. As described above, the PLC-LN type optical switch according to the present embodiment functions as a wavelength selector that selects an arbitrary wavelength from the multi-wavelength optical signal. In FIG. 8, as an example, the wavelength λ₂An example of selecting only the optical signal is given.
[0083]
As in this embodiment, by combining a quartz PLC substrate with an optical waveguide circuit of another material, a menu of abundant optical circuits such as AWG realized by the PLC substrate can be used. Since the curvature radius of a certain optical waveguide is smaller in the PLC, there is an advantage that a highly functional circuit can be manufactured in a small size. As an optical switch, when LN is used, there is an advantage that high-speed optical switching can be realized with low power consumption.
[0084]
Even in a circuit including an optical switch in which such a PLC-LN substrate is combined, by mounting the IC directly on the optical circuit substrate, the same as described in (1) to (4) of the first embodiment. There is an effect.
[0085]
In the present embodiment, an example of the wavelength selector has been described, but the same effect can be obtained with other optical circuits. For example, a tree-like optical switch similar to that shown in FIG. 1, for example, a 1 × 8 optical switch can be configured using the structure of the present embodiment. In the 1 × 8 optical switch in that case, the same effects as described in (1) to (4) of the first embodiment can be obtained.
[0086]
(Other embodiments)
As mentioned above, although several preferable embodiment of this invention was illustrated, this invention is not limited to these embodiment, if it is in the range described in each claim of the claim, these embodiment Such modifications, replacement with other elements having equivalent functions, simple design changes such as dimensions and number, etc. are all included in the embodiments of the present invention.
[0087]
【The invention's effect】
As described above, according to the present invention, in an optical circuit such as an optical switch, the size of the electric wiring portion on the optical waveguide substrate is reduced by sharing, so that the substrate itself is also reduced in size for driving or control. IC mounting board for driving optical switches and optical variable attenuators by significantly reducing the number of gold wires between boards where reliability is a concern by mounting the IC on the optical waveguide board with bare chips Is eliminated, and the module size can be reduced.
[0088]
Furthermore, according to the present invention, the number of electrode terminals (electrode pads) of the prober used for evaluating the characteristics of the optical waveguide substrate as an inspection process in the production of an optical circuit is greatly reduced, and the evaluation work is simplified. There is also an effect that the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a configuration of a 1 × 128 PLC thermo-optic switch mounted with an IC bare chip according to a first embodiment of the present invention.
2 is an enlarged view showing details of a mounting portion of the IC bare chip of FIG. 1; FIG.
FIG. 3 is a schematic plan view showing a configuration in which an IC bare chip is mounted on 8 arrays of 2 × 2 optical switches in a modification of the first embodiment of the present invention.
FIG. 4 is a schematic plan view showing a configuration in which an IC bare chip is mounted on a PLC chip of a 4 × 4 matrix optical switch according to a second embodiment of the present invention.
5 is an enlarged view of the dual optical switch of FIG. 4 constituting an optical matrix switch that can be completely individually driven with a small number of drive circuits.
FIG. 6 is a circuit diagram showing a specific circuit configuration in a second embodiment of the present invention.
FIG. 7 is a schematic plan view illustrating a configuration of a transmission module including a variable optical attenuator according to a third embodiment of the present invention.
FIG. 8 is a schematic plan view illustrating a configuration of a wavelength selector according to a fourth embodiment of the present invention.
FIG. 9 is a schematic plan view showing a configuration of a conventional 1 × 128 PLC thermo-optic switch.
FIGS. 10A and 10B are diagrams showing the configuration of the Mach-Zehnder interferometer type optical switch of FIG. 9, wherein FIG. 10A is a plan view, FIG. It is sectional drawing which follows a section line.
11 is a circuit diagram showing a circuit configuration of the electric drive circuit of FIG. 9. FIG.
FIG. 12 is a schematic plan view showing a configuration example of a 1 × N optical switch that is a basic configuration of an embodiment of the present invention and in which a drive circuit is markedly shared.
13 is a circuit diagram showing a circuit configuration of a heater driving circuit of the 1 × N optical switch of FIG. 12. FIG.
FIG. 14 is a circuit diagram showing a configuration of an electric circuit including a driving digital IC, which is a basic configuration of the embodiment of the present invention.
15 is a time chart showing the timing of heater control signals applied to the heater array of FIG.
[Explanation of symbols]
  101 1 × 128 PLC thermo-optic switch (1 × 128 optical switch)
  103 1 × 2 basic optical switch
  104 Optical waveguide
  105 Gate optical switch
  107 Gold wiring for heater drive
  109 Basic switch drive IC (bare chip)
  111 Control signal gold wiring (gold thin film wiring)
  113 electrode pad
  115 gold wire
  117 electrode pad
  119 Drive signal feed line (feed line for drive power supply circuit)
  201, 202 electrode pad
  203, 204 electrode pads
  205,206 Gold wire
  401 4 × 4 optical matrix switch (optical matrix chip)
  403 Drive signal feed line
  405 Drive signal feeder
  407 Input waveguide
  409 Output waveguide
  411 Double optical cross point switch (double optical switch unit)
  415 1 × 2 optical switch
  416 2 × 1 optical switch
  421 In-unit waveguide
  601 Shared drive (analog power supply) circuit for 1 × 2 optical switch
  602 2x1 optical switch shared drive (analog power supply) circuit
  603 Electric digital switch
  701 LD element for WDM signal
  703 optical fiber
  705 PLC board
  707 Mach-Zehnder type made of quartz PLCVariable lightAttenuator
  709 IC for driving variable optical attenuator
  711 Gold wiring for heater drive
  713 Gold wiring for IC drive
  717 Arrayed Waveguide Grating (AWG)
  801 first PLC substrate including array waveguide grating
  803 Second LiNbO₃(LN) substrate
  805 Third PLC substrate including array waveguide grating
  807 Mach-Zehnder type circuit
  809 Driving IC mounted on the second LN substrate 803
  811 LiNbO formed on LN substrate 803₃Optical waveguide
  813 Heater drive gold wiring
  815 Gold wiring for IC control
  901 1 × 128 optical switch
  903 1 × 2 optical switch
  905 Gate optical switch
  907 Drive signal feed line
  909, 923 Heater driving gold wiring
  911 electrode pad
  913 gold wire
  915 electrode pad
  921 IC mounting board for driving optical switch
  923 IC control gold wiring
  925 IC module for driving (package)
  1001 Arm waveguide
  1003, 1009 3 dB coupler
  1005 Wiring
  1007 Thermo-optic phase shifter (thin film heater)
  1011 Core pattern
  1013 Clad layer
  1015 Substrate such as silicon wafer
  1101 Drive analog power supply circuit (unshared)
  1103 Electric digital switch
  1105 Electrical connection terminal
  1107 Heater
  1201 Drive signal feed line
  1301 Shared drive analog power supply circuit
  1403 Heater array on PLC substrate

Claims (2)

In the optical module configured by an electronic circuit of a plurality of drive for varying the output characteristics given refractive index change in the optical switch and the optical switch,
The electronic circuit for driving is mounted on the substrate of the optical switch together with the optical switch ,
The optical switch includes one input waveguide formed on a substrate of the optical switch and N ( N is an integer of 3 or more) and a plurality of 1 × 2 optical switches that connect the input waveguide and the output waveguide, allowing light to be transmitted, blocked, or variable in light intensity A 1 × N optical switch in which a gate optical switch is provided in the output waveguide,
The 1 × 2 optical switch is an analog optical switch whose path is continuously switched by an electric signal level controlled by the driving electronic circuit,
The analog optical switch includes an electric digital switch for cutting off the electric signal level from the driving electronic circuit,
The driving electronic circuit is shared by the plurality of 1 × 2 optical switches such that the number of the driving electronic circuits is smaller than the number of the 1 × 2 optical switches, When the 1 × N optical switch performs a switch operation, only one 1 × 2 optical switch of each stage is driven,
Wirings connecting from the analog drive power source to the 1 × N optical switch are aggregated and shared for each stage of the 1 × N optical switch on the optical switch substrate,
The optical digital switch is integrated by an electronic integrated circuit manufacturing process . In the optical module configured by an electronic circuit of a plurality of drive for varying the output characteristics given refractive index change in the optical switch and the optical switch,
The electronic circuit for driving is mounted on the substrate of the optical switch together with the optical switch ,
The optical switch includes M (on the substrate of the optical switch) M is an integer of 2 or more) input waveguides and N ( N is an integer of 2 or more) Output waveguide and M × N Consisting of 1 optical crosspoint switch ( m , n ) The optical crosspoint switch of No. is an optical crosspoint switch that connects the mth input waveguide and the nth output waveguide ( Where 1 ≦ m ≦ M , 1 ≦ n ≦ N) The optical cross point switch is a double optical switch composed of a 1 × 2 optical switch, a 2 × 1 optical switch, and an optical cross point switch unit waveguide,
The 1 × 2 optical switch and the 2 × 1 optical switch are analog optical switches whose paths are continuously switched according to an electric signal level controlled by the driving electronic circuit,
The analog optical switch includes an electric digital switch for cutting off an electric signal level from the driving electronic circuit,
The electronic circuit for the driving circuit is shared by the plurality of the dual optical switches so that the number of electronic circuits for the driving circuit is smaller than the number of the dual optical switches, Driving only one of the dual optical switches grouped for each of the input waveguides when the optical crosspoint switch performs a switch operation;
The wiring connecting the analog drive power source to the duplex optical switch is divided into two 1 × 2 optical switch groups and 2 × 1 optical switch groups constituting the grouped dual optical switches, and each is separately provided. An optical module, wherein the optical modules are aggregated and shared on a substrate of the optical switch .

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