Media adapters for multimode waveguide interconnections

Abstract

To provide, generally, electronic systems having photonic integrated circuits (PICs), and more specifically, media adaptors for multimode waveguide interconnects.SOLUTION: Example implementations described herein involve a media adaptor configured to provide electrical / optical and optical / electrical conversion for a multimode waveguide (MMWG) interconnect, the media adaptor involving one or more ball grid arrays and a tail-cut fiber array block (tcFAB) that is connected to a first array of photodiodes and a second array of laser diodes from direct optical wire (DOW) bonding.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application is based on and claims the benefit of priority from U.S. Provisional Patent Application No. 63 / 248,241, filed September 24, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety for all purposes.

[0002] The present disclosure relates generally to electronic systems having photonic integrated circuits (PICs), and more particularly to media adapters for multimode waveguide interconnects. [Background technology]

[0003] There has been a recent development of electrical printed circuit boards with embedded optical waveguides to provide light that is to be converted into electrical signals and vice versa. Such systems are known as printed optical circuit boards and are referred to herein as printed optical boards (POBs).

[0004] In systems with PICs on POBs, hereafter referred to as "PIC systems," optical connectors become congested in the immediate vicinity of the system-on-chip (SoC) as the copper traces of the PIC system collapse toward zero. Unfortunately, no optical input / output (I / O) standard exists for this congested bus environment. The PIC's inputs and outputs (equivalent to the I / O buffers and bond pads of an electrical system), also known as the off-chip optical bus, do not have any candidate solutions, industry consensus, or standards activity. This lack of a solution is an ongoing challenge faced by connector manufacturers involved with PIC components.

[0005] There have been recent developments in printed optical board (POB) design involving waveguides embedded within the circuit board. Figure 1 shows an exemplary POB system. Specifically, Figure 1 shows the optical waveguide core layers and processes embedded in the printed circuit board (PCB) material. The arrows indicate the direction of the light path from the optical module to the SoC. Because the optical and electrical layers are aligned during manufacturing, the assembly house does not need to provide extra alignment. However, the material system requires a new lamination process, which increases costs and results in unknown field product reliability.

[0006] FIG. 2 illustrates a multimode waveguide (MMW) system. In the example illustrated in FIG. 2, there are one or more multimode waveguide (MMW) PICs 206 connected to a POB 210 to interface with chiplets 208 connected to an ultra-fiber optic cable 203 through a waveguide-to-fiber cable connector 202. Each of the one or more MMW PICs 206 includes an MMW 205 configured to facilitate optical signals from the MMW PIC to the POB, and is connected through a bidirectional channel to an integrated digital equalizer 201 configured to perform electrical-to-optical signal conversion. In a system such as described herein, the MMW PICs 206 and PICs 208 can be configured to perform aggregation, optical switching (e.g., switching functions), and electrical functions, depending on the desired implementation. Such an implementation can avoid a single-mode approach.

[0007] The built-in digital equalizer 201 is configured to perform electrical-to-optical signal conversion for outgoing signals from the MMW PIC 206 through the MMW 205, or optical-to-electrical signal conversion for incoming signals from the MMW 205 to the MMW PIC 206. In one example, the built-in digital equalizer 201 may involve a serializer / deserializer (SERDES) linear or nonlinear equalizer scheme to compensate for impairments that the MMW 205 may generate. Impairments induced by the MMW 205 (either from the multimode waveguide or fiber) are in the form of modal dispersion, which is deterministic noise such as reflections and insertions, that can be compensated for by the built-in digital equalizer 201, whether it is a linear or nonlinear equalizer. The built-in digital equalizer 201 interfaces between the MMW PIC 206 and the MMW 205 through a chip-to-waveguide connector 211. As described herein, the built-in digital equalizer 201 is utilized for channel signal impairments across the optical path.

[0008] The MMW bus 204 includes waveguides embedded in the POB 210 connected to the PIC 206 through a waveguide-to-waveguide connector 207 for consolidating optical signals traveling through the POB 210. The waveguide-to-waveguide connector 207 is an optical signal-to-optical signal interface that directs optical signals along the signal flow direction 200 through the MMW bus 204 for outgoing signals or from the MMW bus 204 to the MMW PIC 206 for incoming signals.

[0009] The PIC 208 may include both an MMW PIC and a single-mode waveguide (SMW) PIC and is configured to connect to the super fiber optic cable 203 through a waveguide-to-fiber cable connector 202. The PIC 208 also connects to the POB 210 using a chip-to-waveguide connector 211 to interface the PIC 208 with the MMW bus 204. Similarly, the PIC 208 may also include an equalizer to facilitate optical-to-electrical signaling for the launch signal 200 from the MMW PIC 206 to the PIC 208, or electrical-to-optical signaling for the ingress signal to the MMW bus 204. The PIC 208 is configured to convert optical signals received from the MMW bus 204 through the chip-to-waveguide connector 211 into electrical signals, which can then be converted back to optical signals for output to the super fiber optic cable 203, such as a single-mode fiber (SMF) cable.

[0010] 2, PIC 206 may be in the form of a transport PIC (tPIC), and PIC 208 may be in the form of a switch PIC (swPIC). In the exemplary implementation described herein, the tPIC is configured to have a multimode waveguide interface facilitated by waveguide connector 211, while the switch PIC has both a multimode waveguide interface as well as an SMF interface for cable 203. Summary of the Invention [Means for solving the problem]

[0011] Aspects of the present disclosure involve a media adapter configured to provide electrical-to-optical and optical-to-electrical conversion for multimode waveguide (MMWG) interconnections, the media adapter including one or more ball grid arrays, a tail-cut fiber array block (tcFAB) connected to a first array of photodiodes and a second array of laser diodes via direct optical wire (DOW) coupling.

[0012] Aspects of the present disclosure relate to a multimode waveguide (MMWG) interconnect that can include a media adapter configured to provide electrical-to-optical and optical-to-electrical conversion for the multimode waveguide (MMWG) interconnect, the media adapter having one or more ball grid arrays, a tail-cut fiber array block (tcFAB) connected by direct optical wire (DOW) coupling to a first array of photodiodes and a second array of laser diodes, and a printed circuit board with the MMWG connected by the DOW coupling to the media adapter. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 illustrates an exemplary printed optical board (POB) system. [Figure 2] FIG. 1 illustrates an exemplary multimode waveguide system. [Figure 3] FIG. 1 illustrates an exemplary proposed interconnection scheme for chip-modules from using optical multimode waveguides (MMWGs) and media / MMWG adapters (MAs) according to an exemplary implementation. [Figure 4] FIG. 1 is a block diagram of the proposed MMWG interconnection. [Figure 5] 1 shows an abstract link model of the proposed MMWG interconnection. [Figure 6] FIG. 1 illustrates an MMWG interconnection system according to an exemplary implementation. [Figure 7(A)] 1 illustrates an exemplary media adapter according to a first embodiment. [Figure 7(B)] 1 illustrates an exemplary media adapter according to a first embodiment. [Figure 7(C)] FIG. 1 shows a comparison between standard FAB and tcFAB. [Figure 8] FIG. 1 illustrates an exemplary media adapter according to a second embodiment. [Figure 9] FIG. 10 illustrates an exemplary media adapter according to a third embodiment. [Figure 10]FIG. 10 illustrates an exemplary media adapter according to a fourth embodiment. [Figure 11] FIG. 10 illustrates an exemplary media adapter according to a fifth embodiment. [Figure 12] FIG. 10 illustrates an exemplary media adapter according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following detailed description provides further details of the figures and exemplary implementations of the present application. Redundant element reference numbers and descriptions between figures are omitted for clarity. The terminology used throughout this specification is provided by way of example and is not intended to be limiting. The exemplary implementations described herein can be used alone or in combination with other exemplary implementations described herein or any other desired implementations.

[0015] The exemplary implementations described herein involve an MMWG interconnect system that can reduce or replace copper traces with optical multimode waveguides. In the exemplary implementations described herein, the media / MMWG adapter (MA) or media adapter is a thin layer without digital filters for electrical-to-optical and optical-to-electrical conversion. The MAs described herein can be vertically integrated into two-dimensional areas in an interposer-like fashion. The terms "media adapter" and "MMWG adapter" may be used interchangeably herein.

[0016] FIG. 3 illustrates an exemplary proposed interconnection scheme for chip-modules using optical multimode waveguides (MMWGs) and media / MMWG adapters (MAs) according to an exemplary implementation. Specifically, FIG. 3 illustrates the use of MMWGs 303 and MAs 302 to maintain pluggable optics within faceplate 304. In the exemplary implementation described herein, MAs 302 are in the form of thin electrical interfaces, as described herein below. An exemplary implementation utilizes printed optical waveguides (specifically MMWGs) inside PCB layers for interconnection paths between a system-on-chip (SoC) / switch chip 301 and an optical module, such as fiber 305, or another chip depending on the desired implementation. This system increases interconnect bandwidth and power efficiency (bits / pJ) and eliminates human error during the assembly process.

[0017] 4 shows a block diagram of the proposed MMWG interconnect according to an example implementation. The MMWG interconnect system is defined to replace copper traces with an MMWG 303 embedded in a PCB 401 and a newly defined thin interface, the Media / MMWG Adapter (MA) 302, on either end of the MMWG 303. The MA 302 is located in close proximity to the SoC 301 and to an optical module 402 configured to facilitate pluggable optics, or it can be embedded inside a cage depending on the desired implementation.

[0018] FIG. 5 shows an abstract link model of the proposed MMWG interconnection according to an exemplary implementation. To achieve power efficiency in the MMWG interconnection, the MA function is further explained in the link model shown in FIG. 5. An electrical switch output buffer drives the MA 302 at the transmitter to perform electrical-to-optical signal conversion and transmit the optical signal through the MMWG 303. The optical signal is terminated by optical-to-electrical conversion at the input of the MA 302 at the receiver just before the faceplate 304. The MA 302 is made of low-power consumption components, as described herein below. The remaining path from the receiver side of the fiber 305 is in the reverse order. That is, the MMWG link eliminates copper traces except for the electrical interface points at the MA, which add extra power consumption along with new integration factors. As a result, the length of the copper traces can be significantly reduced or completely eliminated. Furthermore, optical connections can also be significantly reduced to connect to the MMWG on the PCB.

[0019] FIG. 6 illustrates an MMWG interconnect system according to an exemplary implementation. In the exemplary implementations described herein, electrical traces are minimized, while optical traces are also shortened through the use of MMWG interconnects. The MMWG interconnects can have a 2D interface with MA 302, as shown at 601, in that they can be oriented anywhere on the X,Y plane to interface with the MA according to a desired implementation. As shown in FIG. 6, the MA can also be embedded inside a cage, as shown by MA 602. Such a cage can also be part of faceplate 304 according to a desired implementation.

[0020] As shown below in Figures 7(A) through 12, described herein is a media / MMWG adapter configured to provide electrical-to-optical and optical-to-electrical conversion for multimode waveguide (MMWG) interconnections, the media adapter including one or more ball grid arrays (e.g., dummy ball grid arrays and / or signal ball grid arrays), a tail-cut fiber array block (tcFAB) connected to a first array of photodiodes and a second array of laser diodes via direct optical wire (DOW) coupling.

[0021] 7(A) and 7(B) show an exemplary media adapter according to a first embodiment. In the exemplary implementation described herein, direct optical wire (DOW) bonding is used to facilitate the media adapter. Because the media adapter functions in the optical domain, the wires must be transmitted in the optical domain and are thereby coupled through the use of polymer wire bonding as opposed to electrical wire bonding. In the example of FIG. 7(B), there is one array of laser diodes (LDs) for emitting light and DOW-coupled to the optical transmitter chip, and another array of photodiodes (PDs) for receiving light DOW-coupled to the optical receiver chip, as indicated by LD / PD-coupled DOW 705. The arrangement of the laser diodes / photodiodes and the arrangement of the optical receiver and transmitter chips can be interchanged according to the desired implementation.

[0022] The transmitter and receiver (Tx / Rx) chips 701 are coupled to a modified tail-cut fiber array block (tcFAB) 704 that has been modified to truncate the fibers at the far end of the FAB where they would normally protrude from the FAB. The resulting cleaved sections are polished, and the tcFAB 704 is then wire bonded using DOW bonding. Essentially, the modified tcFAB 704 can thus function as a miniature waveguide block.

[0023] One or more ball grid arrays are used to bond the media adapter to the PCB via solder to align the MMWG with the optical transmitter and receiver. Additionally, fibers in the FAB can be connected to the ball grid array via electrical wire bonds to facilitate electrical signals to the electrical chips to facilitate electrical / optical and optical / electrical connections.

[0024] 7(A) and 7(B), signal ball grid array 703 is used to facilitate electrical connection to the chip, while dummy ball grid array 702 is used to facilitate alignment to the printed circuit board or printed optical board. Signal ball grid array 703 connects the media adapter to chip 301, the fibers of the tcFAB are connected to signal ball grid array 703 through electrical coupling, and chip 301 is electrically connected to signal ball grid array 703.

[0025] As shown in Figures 7(A) and 7(B), dummy ball grid array 702 connects the media adapter to printed circuit board 730 via solder to align tcFAB 704 with MMWG 303 of the MMWG interconnect. tcFAB 704 connects to MMWG 303 of the MMWG interconnect through DOW bonding. As shown in Figure 7(B), the MMWG is DOW bonded from the PCB to the media adapter to facilitate connection to tcFAB 704, and electrical traces on the PCB are wire bonded from the electrical chip through signal ball grid array 703 to tcFAB 704.

[0026] FIG. 7C shows a comparison between a standard FAB and a tcFAB. In the embodiments herein, a standard FAB 710 is replaced by a tcFAB 704. The standard FAB 710 includes a fiber pigtail 713, whereas in this embodiment, the fiber pigtail 713 of the standard FAB 710 is cut 712 with an optical wire bond to repurpose the FAB 710 as a tcFAB 704 for the embodiments herein. In the examples of FIGS. 7A and 7B, the tcFAB 704 is disposed on a substrate 740, with the receiver chip and transmitter chip 701 on opposite sides of the substrate from the tcFAB 704.

[0027] 8 shows an exemplary media adapter according to a second embodiment. In this exemplary embodiment, the dummy ball grid array can be eliminated if alignment is possible without the use of the dummy ball grid array. Thus, only a signal ball grid array 803 is used to save space for the media adapter if necessary.

[0028] 9 shows an exemplary media adapter according to a third embodiment. In this exemplary embodiment, the transmitter and receiver chips 901 are located directly below the tcFAB on the same side of the substrate on which the tcFAB is located. This contrasts with placing the transmitter and receiver chips 901 on opposite sides of the substrate to save space on the substrate for the MA while eliminating the dummy ball grid array.

[0029] 10 shows an exemplary media adapter according to a fourth embodiment, in which the dummy ball grid array and signal ball grid array are maintained, but the transmitter and receiver chips 1001 are placed under the tcFAB.

[0030] 11 and 12 show an exemplary media adapter according to the fifth embodiment. In this exemplary embodiment, the transmitter and receiver chips 1101 are located on a substrate for the MA on the same side as the tcFAB (e.g., adjacent to the tcFAB). Such an exemplary implementation may be useful for implementations in which the transmitter and receiver chips 1101 can be placed on the substrate on the same side as the tcFAB, as opposed to the opposite side. The example in FIG. 11 includes a dummy ball grid array, but if alignment is available, the dummy ball grid array can be omitted, as shown in FIG. 12.

[0031] As described herein, the above-described media adapters can participate in systems involving multi-mode waveguide (MMWG) interconnects and printed circuit boards having the MMWGs connected to the media adapters by direct optical wire bonding.

[0032] Moreover, other implementations of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the teachings of the present application. Various aspects and / or components of the above-described exemplary implementations may be used alone or in any combination. It is intended that the specification and exemplary implementations be considered as exemplary only, with a true scope and spirit of the present application being indicated by the following claims. [Explanation of symbols]

[0033] 201 Built-in digital equalizer 202 Waveguide-Fiber Cable Connector 203 Ultra Fiber Optic Cable 208 Chiplets 210 Printed Optical Board

Claims

1. 1. A media adapter configured to provide electrical-to-optical and optical-to-electrical conversion for a multimode waveguide (MMWG) interconnection, comprising: one or more ball grid arrays provided on one surface of the substrate; a tail-cut fiber array block (tcFAB) on one face of the substrate, connected to a first array of photodiodes and a second array of laser diodes via direct optical wire (DOW) coupling, and optically connected to the MMWG through cut sections of fiber; wherein the cut portion of the fiber is provided at an end of the tcFAB.

2. 2. The media adapter of claim 1, wherein the one or more ball grid arrays comprise a dummy ball grid array that connects the media adapter to a printed circuit board through solder to align the tcFAB with the MMWG of the MMWG interconnect, and the tcFAB is connected to the MMWG of the MMWG interconnect through a DOW bond.

3. the one or more ball grid arrays comprise a signal ball grid array connecting a media adapter to a chip; the tcFAB is connected to the signal ball grid array through an electrical coupling; the chip is electrically connected to the signal ball grid array; 2. The media adapter of claim 1.

4. further comprising a transmitter chip and a receiver chip; the first array of photodiodes is connected to the receiver chip and the second array of laser diodes is connected to the transmitter chip; 2. The media adapter of claim 1.

5. the receiver chip and the transmitter chip are disposed on opposite sides of the tcFAB in a thickness direction of the substrate; 5. The media adapter of claim 4.

6. the receiver chip and the transmitter chip are disposed on one surface of the substrate below the tcFAB; 5. The media adapter according to claim 4.

7. the receiver chip and the transmitter chip are disposed on the one surface of the substrate together with the tcFAB; 5. The media adapter according to claim 4.

8. 10. The media adapter of claim 1, wherein the media adapter is connected to one or more multimode waveguides of a printed circuit board by a DOW coupling as part of a multimode waveguide interconnect.

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