Optical Module

Abstract

The positions at which electrode pads are arranged can be made more flexible, and electrical interconnects to be installed can be reduced. In addition, the degree of integration of a chip increases, making it possible to realize a large-scale device (optical switch etc.). In an optical module of the present invention, an interposer (an electrical connection intermediary component with electrode pins attached onto upper and lower faces in an array) is laid over a chip that includes a device configured by using a planar lightwave circuit (PLC) fixed onto a fixing metal plate, and a control substrate for driving the device is laid over the interposer. These components are mechanically fixed by a fixing screw or the like, and the electrode pads of the chip and the control substrate are connected to each other via the interposer.

Claims

1. An optical module comprising: a planar lightwave circuit having an electrode pad on an upper face; a control substrate for driving the planar lightwave circuit, the control substrate being arranged above the upper face of the planar lightwave circuit and having an electric pad on a lower face opposing the upper face of the planar lightwave circuit; and an electrical intermediary component arranged between the upper face of the planar lightwave circuit and the lower face of the control substrate, wherein the electrode pad of the planar lightwave circuit and the electrode pad of the control substrate are connected to each other via the electrical intermediary component.

2. The optical module according to claim 1, wherein the electrical intermediary component has a lead pin.

3. The optical module according to claim 2, wherein a portion of the lead pin is of a spring type.

4. The optical module according to claim 1, wherein the planar lightwave circuit and the control substrate are electrically connected to each other using a plurality of the electrical intermediary components.

5. The optical module according to claim 1, wherein the number of at least one of the planar lightwave circuit, the electrical intermediary component, and the control substrate is more than one.

6. The optical module according to claim 1, wherein the electrical intermediary component is laid over a plurality of the planar lightwave circuits and is connected thereto.

7. The optical module according to claim 6, wherein the control substrate is laid over a plurality of the planar lightwave circuits, and a screw is arranged between the planar lightwave circuits.

8. The optical module according to claim 1, wherein the electrical intermediary component is an interposer.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 is a top view showing a conventional quartz PLC optical switch bare module.

[0028] FIG. 2 is a diagram showing an electrical interconnect layout of a conventional PLC.

[0029] FIG. 3(a) is a top view showing a quartz PLC optical switch bare module that has an electrical mounting method of Embodiment 1. FIG. 3(b) is a cross-sectional view showing the quartz PLC optical switch bare module that has the electrical mounting method of Embodiment 1.

[0030] FIG. 4 is a diagram showing a layout of PLC electrical interconnects of Embodiment 2.

[0031] FIG. 5(a) is a top view showing a quartz PLC optical switch bare module that has an electrical mounting method of Embodiment 2.

[0032] FIG. 5(b) is a cross-sectional view showing the quartz PLC optical switch bare module that has the electrical mounting method of Embodiment 2.

[0033] FIG. 6 is a top view showing a quartz PLC optical switch bare module that has an electrical mounting method of Embodiment 3.

[0034] FIG. 7 is a diagram showing an example of a combination of PLC chips and interposers.

DESCRIPTION OF EMBODIMENTS

[0035] Hereinafter, an optical device according to embodiments of the present invention will be described.

Embodiment 1

[0036] Embodiment 1 will describe a 16×16 multicast switch that realizes a planar electrical connection structure using a commercially available interposer (an electrical connection intermediary component with electrode pins attached on the upper and lower faces in an array).

[0037] In this embodiment, an interposer with a lead pin portion of the spring type is used in order to address warping of the chip of the planar lightwave circuit.

[0038] FIGS. 3(a) and 3(b) show a top view and a cross-sectional view, respectively, of a multicast switch module 300. The multicast switch module 300 includes a quartz-based planar lightwave circuit (PLC, planar lightwave circuit chip) 303 that is connected to an optical fiber 302 and constitutes an optical circuit, a control substrate 305 that drives and controls the optical circuit, and an interposer (interposer components) 301 that connects the PLC 303 and the control substrate 305 to each other. The multicast switch module 300 also includes a fixing plate 306 and screws 308 for fixing the PLC 303, the control substrate 305, and the interposer 301. Note that the control substrate may be an insulating substrate formed by impregnating glass fiber with epoxy resin.

[0039] FIG. 4 shows a schematic view of a layout an optical circuit and electrical interconnects of the PLC. The PLC includes 256 optical switches, each of which includes a Mach-Zehnder interferometer 304. An electrode pad 307 is arranged near each of the arranged optical switches, and a heater in the Mach-Zehnder interferometer 304 and the electrode pad 307 are connected by an electrical interconnect. The electrode pad 307 may include Au, for example.

[0040] As is understood by comparing the conventional electrical interconnect layout shown in FIG. 2 with the electrical interconnect layout in this embodiment in FIG. 4, the electrical interconnect length in this embodiment is greatly smaller than that in the conventional example, and the electrical interconnect length in this embodiment is equal for all of the switches. Accordingly, the electrical interconnects in the PLC chip surface can be reduced.

[0041] This PLC optical switch can be produced using a common method, such as those described in NPL 1 to 3.

[0042] An optical fiber 302 with a total of 32 cores for input and output is connected to an input-output portion of a PLC end face. The quartz-based planar lightwave circuit (PLC) 303, which is fixed onto the fixing plate 306 with an adhesive, and the control substrate 305 for driving the PLC are fixed to each other with the screws via the interposer 301.

[0043] At this time, the positions at which the interposer 301, the PLC 302, and the control substrate 305 for driving the PLC are fixed are aligned using pins. These pins are guide pins 309, and the pins may be or need not be provided with screws. The positioning can be done due to the guide pins 309 passing through holes in the interposer 301 and holes in the control substrate 305 and being fitted to recessed portions of the fixing plate 306. Note that the guide pins 309 may be provided at any positions at which the guide pins 309 do not pass through the PLC 303, passes through the holes in the interposer 301 and the holes in the control substrate 305, and is fitted to the recessed portion of the fixing plate 306.

[0044] The control substrate 305 for driving the PLC is covered from above by a CrCu plate (not shown) in which screw holes are formed, and a base plate, e.g. the fixing plate 306 that contains CuCr, and the CuCr plate, which is the uppermost face, are screwed with each other. By thus screwing, lead pins (hinge electrodes) 301a of the interposer of the spring type are pressed against the PLC 303 and the electrode pads 305a of the control substrate 305 for driving the PLC, and are brought into contact therewith and fixed thereto.

[0045] The configuration of the module in the top view and the cross-sectional view is as shown in FIGS. 3(a) and 3(b). The PLC 303 is fixed onto the fixing plate 306. The interposer 301 and the control substrate 305 for driving the PLC are stacked on the PLC 303, and the PLC 303, the interposer 301, and the control substrate 305 for driving the PLC are mechanically fixed. The fixing plate 306 and the PLC 303 are fixed using an adhesive. By providing (making) holes in the fixing plate 306, the interposer 301, and the control substrate 305 for driving the PLC, the fixing plate 306 that contains metal, the interposer 301, and the control substrate 305 for driving the PLC are fixed with the screws 308 through the holes. At this time, a metal plate (not shown) may be inserted onto the control substrate 305 for driving the PLC such that the pressure of the screws 308 are uniformly applied to the entire face of the control substrate 305 for driving the PLC. The pad electrodes 307 of the PLC 303, the lead pins (hinge electrodes) 301b of the interposer, and the electrode pads 307 of the control substrate 305 for driving the PLC need to be positioned, and the positioning is performed using the guide pins 309 in addition to the aforementioned screws 308 for fixation. The lead pins 301b of the interposer are of the spring type.

[0046] By the above steps, a multicast switch module 300 was produced that includes: a planar lightwave circuit PLC 303 that has electrode pads on an upper face; a control substrate 305 for driving the planar lightwave circuit that is arranged above the upper face of the planar lightwave circuit and have electrode pads on a lower face opposing the upper face of the planar lightwave circuit; and an electrical intermediary member arranged between the upper face of the planar lightwave circuit and the lower face of the control substrate 305, e.g. an interposer 301, wherein the electrode pads of the planar lightwave circuit 303 and the electrode pads of the control substrate 305 are connected to each other via the electrical intermediary members.

[0047] Electrical characteristics and optical properties of the thus-produced 16×16 multicast switch module was evaluated.

[0048] It was discovered that all terminals were conductive, and the variation in resistance values was ±0.1Ω. Thus, uniform contact was confirmed at all terminals. This variation in the resistance values is smaller than the variation in the case of wire bonding connection of the conventional optical switch (FIGS. 1 and 2). The main reason for this result is considered to be a smaller variation in the interconnect length on the chip in this embodiment than that in the case of the wire bonding method.

[0049] Next, optical properties of the optical switch were evaluated. The transmission loss, extinction ratio, and so on were obtained that are equal to those of an optical module that employs the conventional wire bonding method. This made it possible to realize a 16×16 MCS that uses an interposer in the electrical mounting method. A smaller switch than a conventional one was able to be realized.

Embodiment 2

[0050] This embodiment will describe a 32×32 multicast switch that uses four interposer 501 on one chip.

[0051] If the chip size increases as the number of integrated switches increases, consideration needs to be given to the influence of warping of the chip.

[0052] There are cases where an interposer whose lead pin portion is of the spring type is used in order to address warping of the chip, but if the amount of warping of the chip increases, it can be expected that the amount of warping cannot be addressed only with the spring of the lead pin of the interposer. Embodiment 2 will describe electrical mounting for addressing warping of the chip by using a plurality of interposers for one chip.

[0053] FIG. 5 shows a 32×32 multicast switch 500 in Embodiment 2. The constituent components are the same as those in Embodiment 1, whereas this embodiment addresses warping of the chip by using four interposers.

[0054] Although the number of optical switches accommodated is four times the number of switches in Embodiment 1, the electrical interconnect layout is basically the same as that of the switch in Embodiment 1. The PLC fixed to a fixing metal plate and control substrates for driving the PLC are connected to each other via the four interposers 501. As a result of measuring resistance values with an assembled module, all terminals were confirmed to be conductive, and the amount of variation in the resistance values was ±0.1Ω. Obtained values of the transmission loss and the extinction ratio were equal to those obtained when using the conventional (FIGS. 1 and 2) wire bonding. Accordingly, a 32×32 switch to which an electrical mounting method using the interposers 501 was applied was able to be realized.

[0055] The number of interposers to be mounted on the PLC is not limited to four, and any number of interposers may be mounted. The control substrate 505 for driving the PLC to be placed over the interposers may be divided into a plurality of control substrates, or may be a single control substrate.

Embodiment 3

[0056] Embodiment 3 will describe an optical switch module 600 shown in FIG. 6 in which electrodes of a plurality of PLC chips are connected to each other using interposers 601. Here, a multicast switch MCS will be described that is configured by combining a 16×16 multicast switch with three PLC switches, namely 1×2 switch 603a and 16×8 switches 603. Note that the two PLC switches 603 may be formed by dividing one PLC switch.

[0057] The 1×2 PLC switch 603a and the 16x8 PLC switches 603 are optically connected to each other via an optical waveguide, and the 1×2 PLC switch 603a and the 16×8 PLC switches 603 are connected to optical fibers 602a and 602, respectively. The 16×8 multicast switches 603 and the 1×2 switch 603a that use PLCs are fixed onto a fixing plate 606, which is a substrate for releasing heat. As shown in FIG. 6, control substrates 605, which are control boards, are placed over the plurality of PLCs 603 so as to cover the PLCs 603.

[0058] One or more interposers 601 that mediate the PLCs 603 and the control substrates 605 may be used as substrates.

[0059] The PLCs 603, the control substrates 605, and the interposers 601 are fixed using screws 608, similarly to Embodiment 1. At this time, by fixing, with the screws 608a, not only the two ends of each of the control substrates 605 but also an intermediate portion thereof sandwiched between the plurality of PLCs 603, lead pins of the interposers 601 are uniformly pressed against electrode pins of the control substrates 605 and the PLCs 603 over the entire face, and the electrical connection state between the electrode pads of the control substrates 605 and the lead pints of the interposers 601 can be made uniform over the entire face, and the electrical connection state between the electrode pads of the PLCs 603 and the lead pins of the interposers 601 can also be made uniform over the entire face.

[0060] This configuration in which divided chips are integrally connected by interposers is effective in the case of mounting uplink and downlink MCSs on one control board in a multicast switch for a ROADM system.

[0061] FIG. 6 discloses an optical switch module 600 in which one interposer 601 is laid over two PLCs 603 chips and connected thereto. Meanwhile, FIG. 7 discloses an optical switch module 700 in which n n×1 switches 702-1, 702-2, . . . 702-n (n is a natural number) and n Mn×N switches 703-1, 703-2, . . . 703-n (n is a natural number) are optically connected to each other via optical waveguides. The nxl switches 702-1, 702-2, . . . 702-n and the Mn×N switches 703-1, 703-2, . . . 703-n are formed on a fixing plate (not shown), and interposers 701 are formed so as to be laid over the n×1 switches 702-1, 702-2, . . . 702-n. Also, a plurality of interposers 701 are formed so as to be laid over the Mn×N switches 703-1, 703-2, . . . 703-n. A control substrate is formed over the interposers 701.

[0062] The number of PLC chips over which the interposers 701 are laid may be any number, and the method for dividing the control substrate to cover these interposers 701 from above may also be any method. For example, as indicated by dotted lines in FIG. 7, a control substrate 705a may cover the Mn×N switches 703-1 and 703-2. Also, as indicated by dash-dot lines in FIG. 7, a control substrate 705b may cover the Mn×N switch 703-n. Further, as indicated by dash-double dot lines in FIG. 7, a control substrate 705c may cover the nxl switches 702-1, 702-2, . . . 702-n.

[0063] The electrical mounting method in Embodiments 1 to 3 of the present invention can be applied to not only optical switches but also optical modules that need to be electrically driven. The type of planar lightwave circuit is not limited to a quartz PLC, and may alternatively be SiPh (silicon photonics) or the like. The present invention is effective since it can also reduce the chip size of a small-scale optical switch.

INDUSTRIAL APPLICABILITY

[0064] The present invention can be applied to optical modules that include a planar lightwave-type optical device for use in optical communication.

REFERENCE SIGNS LIST

[0065] 300 Multicast switch module [0066] 301 Interposer [0067] 301a Lead pin (hinge electrode) [0068] 301b Lead pin (hinge electrode) [0069] 302 Optical fiber [0070] 303 Planar lightwave circuit (PLC) [0071] 304 Mach-Zehnder interferometer [0072] 305 Control substrate [0073] 306 Fixing plate [0074] 307 Electrode pad [0075] 308 Screw [0076] 309 Guide pin