Optical fiber cable coupling assembly

Abstract

Numerous examples of fiber optic cable coupling assemblies and components thereof are disclosed. In one example, a fiber optic cable coupling assembly includes a coupling plate including a plurality of lasers and a plurality of photodiodes; and a mechanical-optical interface, the mechanical-optical interface comprising a first plurality of ferrules and a plurality of lasers, where each laser of the plurality of lasers is aligned with a ferrule of the first plurality of ferrules; and a second plurality of ferrules and a plurality of photodiodes, wherein each photodiode of the plurality of photodiodes is aligned with a ferrule of the second plurality of ferrules.

Description

[0001] Priority Statement

[0002] This application claims priority to U.S. Provisional Application No. 63 / 509,090, filed June 20, 2023, entitled “Low-Cost Silicon Photodiode based Active Optical Cable,” and U.S. Patent Application No. 18 / 628,628, filed April 5, 2024, entitled “Fiber Optic Cable Coupling Assembly.” Technical Field

[0003] Numerous examples of fiber optic cable coupling assemblies have been disclosed. Background Technology

[0004] Due to limitations in physical layer media and components, the data rates for high-speed communications in modern data centers are reaching their limits. There are trade-offs between bandwidth, physical reachability, and cost. For example, active cable (AEC) based on high-quality electrical coaxial cable can maintain an electrical bandwidth of 50 GHz within a 5-meter reachability, but further increases in bandwidth or reachability are not feasible. Above 50 GHz, signal attenuation becomes too high for transceiver circuitry to recover the underlying signal. Further trade-offs involving propagation mode control and signal attenuation create further limitations on reachability, making it economically impossible to have a reachability greater than 3 meters. The simple solution of manufacturing parallel electrical coaxial cable is also limited by the relatively bulky physical size of parallel coaxial cable cabling. Furthermore, parallel cable cabling results in high power consumption, which is proportional to the number of parallel coaxial cables.

[0005] Fiber optic cables, with their small physical size and high bandwidth capacity, can achieve much longer reach than conventional cables. Active optical cables (AOCs) are a type of cable cabling technology with fixed lengths. AOCs have the same electrical inputs and outputs as AECs, but use optical fibers to transmit high-bandwidth signals. Traditional implementations of high-bandwidth AOCs are expensive due to the high assembly cost of the optical engines used for transmitting (TX) and receiving (RX) signals, and the availability of lasers and photodiodes that can operate at bandwidths greater than 50 GHz. Total cost of ownership is a major bottleneck for the widespread replacement of AECs with AOCs. Summary of the Invention

[0006] There is a need for a low-cost AOC that uses parallel optical fibers with silicon dies to provide data center connectivity. These silicon dies integrate high-speed avalanche photodiodes (APDs), transimpedance amplifiers (TIAs), and vertical-cavity surface-emitting laser (VCSEL) drivers in a low-cost fiber-coupled package. Compared to the reachability and bandwidth available in AECs, this AOC has a longer reachability (e.g., 50 meters) and greater bandwidth (e.g., 800 Gbps).

[0007] This article discloses embodiments of integrated silicon-based photodiodes or avalanche photodiodes with TIA and VCSEL laser drivers for achieving simple multi-fiber alignment.

[0008] APDs are used on the receive (RX) side of cables. Compared to standard photodiodes, APDs offer superior bandwidth and sensitivity. As integrated components on the same silicon substrate as TIAs, the linear array or matrix arrangement of APDs can be photolithographically defined to achieve a high level of dimensional accuracy in fiber array coupling alignment. Typically, integrated silicon APDs have optical wavelength responsivity from 200 nm to 900 nm, with peak responsivity between 600 nm and 700 nm. While this is shorter than the wavelengths typically used for fiber optic data communication, fiber optic cable attenuation is less than 1 dB at 600 nm to 700 nm over distances up to 50 meters. Integrated APDs allow for reductions of several orders of magnitude in parasitic intrinsic resistance, inductance, and capacitance (RLC) from the bonding pads and bonding lines between discrete photodiodes and TIA dies.

[0009] VCSELs are used on the transmit (TX) side of the cable. Depending on the requirements of the parallel fiber optic cable, the VCSEL array is arranged in a linear or matrix format. Due to the sensitivity of the APD, the VCSEL modulation current can be kept low while achieving the required cable reachability. This results in lower connection energy / bits compared to other solutions.

[0010] The electrical output of the APD / TIA and the electrical input of the laser driver / VCSEL are coupled to the high-speed transceiver chip to form one end of a typical AOC cable.

[0011] This paper describes several mechanisms and methods for aligning and assembling optical fibers in linear or matrix arrays using precision fiber ferrule fixing devices and photolithographically defined alignment frames. The ferrule fixing devices and coupling fixing devices allow fiber alignment to be completed in a single batch. Unlike the processes used in standard optical engine constructions, this single batch is a low-cost, single-step passive alignment process. To increase cable data rates, the number of optical fibers can be increased without proportionally increasing manufacturing costs. The ferrule fixing devices and coupling fixing devices are manufactured in batch mode. High-speed signals between the coupling assembly and the transceiver chip can be transmitted via one or more impedance-controlled flexible printed circuits (FPCs) or through PCB vias. This component integration approach enables several possibilities for reducing AOC manufacturing and deployment costs.

[0012] A system and method for automatically optimizing the signal in each optical fiber through closed-loop feedback control to reduce operating power, increase manufacturing yield, and reduce maintenance costs are also described. Attached Figure Description

[0013] Figure 1 The fiber optic cable coupling assembly is described.

[0014] Figure 2A , Figure 2B and Figure 2C The fiber optic cable coupling assembly is described.

[0015] Figure 3 The fiber optic cable coupling assembly is described.

[0016] Figure 4A and Figure 4B It shows Figure 3 Additional details on the vertical coupling fixing device of the fiber optic cable coupling assembly.

[0017] Figure 5 Depicting what can be used as Figure 4A and Figure 4B An alternative to the vertical coupling fixing device is a vertical coupling fixing device.

[0018] Figure 6 Depicting what can be used as Figure 4A , Figure 4B and Figure 5 A side view of the vertical coupling fixing device as an alternative to the vertical coupling fixing device.

[0019] Figure 7 A top view of the coupling plate is depicted. Figure 8 The alignment box is depicted.

[0020] Figure 9 A cross-section of the ferrule fixing device aligned with the alignment frame is depicted.

[0021] Figure 10 The alignment box is depicted.

[0022] Figure 11 A cross-section of the ferrule fixing device aligned with the alignment frame is depicted.

[0023] Figure 12 A top view of the coupling plate is depicted.

[0024] Figure 13 A cross-section of the ferrule fixing device aligned with the alignment frame is depicted.

[0025] Figure 14 A top view of the coupling plate is depicted.

[0026] Figure 15 The electrical aspects of the fiber optic cable coupling assembly are described.

[0027] Figure 16 The closed-loop control and optimization of performance metrics are described.

[0028] Figure 17 The control can be described by optimizing the circuit settings.

[0029] Figure 18A , Figure 18B and Figure 18C An embodiment of multiple APDs per fiber is described.

[0030] Figure 19 An embodiment of multiple APDs per fiber is described.

[0031] Figure 20A and Figure 20B An embodiment with an alignment frame including a laser and an APD is depicted.

[0032] Figure 21 A system comprising two devices communicating using a fiber optic cable coupling assembly is described. Detailed Implementation

[0033] Figure 1 A fiber optic cable coupling assembly 100 is depicted. The fiber optic cable coupling assembly 100 is connected to an electrical connector 101 and a fiber optic cable bundle 102. The fiber optic cable coupling assembly 100 receives optical signals from the fiber optic cable bundle 102, converts the optical signals into electrical signals, and transmits the electrical signals through the electrical connector 101. Similarly, the fiber optic cable coupling assembly 100 receives electrical signals from the electrical connector 101, converts the electrical signals into optical signals, and transmits the optical signals through the fiber optic cable bundle 102.

[0034] Figure 2A An isometric view of an optical fiber cable coupling assembly 200 is depicted. The optical fiber cable coupling assembly 200 is... Figure 1An embodiment of the fiber optic cable coupling assembly 100 is described. The fiber optic cable coupling assembly 200 includes a PCB 201, a transceiver chip 202, gold fingers 203, an FPC 204, an alignment frame 205, a coupling fixing device 206, a mechanical-optical interface 207, a coupling plate 208, precision guide pins / holes 209, a collar 210, an optical device 211 (which may be a mirror or prism), and a collar 212. The fiber optic cable coupling assembly 200 is optionally physically mounted on a component containing... Figure 1 At the end of the AOC cable of the fiber optic cable bundle 102 in the middle.

[0035] PCB 201 holds transceiver chip 202, which is mated between electrical connector 101 (not shown) and fiber optic cable coupling assembly 200. At one end of PCB 201, gold fingers 203 are connected to electrical connector 101 (not shown), which in turn connects to an external system such as a server. Gold fingers 203 can form QSFP (Quad Small Form Factor) connectors, SFP (Small Form Factor) connectors, or other types of connectors.

[0036] The coupling fixing device 206 forms a structure that establishes a precise reference to the mechanical-optical interface (MOI) 207, which is here a fiber optic ferrule fixing device that guides multiple optical fibers from the fiber optic cable bundle.

[0037] The coupling fixing device 206 also forms a protective layer around one or more silicon dies containing the APD, TIA, and laser driver. The VCSEL and APD are arranged in an array configuration within the alignment frame 205. The coupling fixing device 206 can be made of ceramic, metal, or plastic and is glued to the coupling plate 208. The coupling plate 208 can be a laminated PCB. Alternatively, the coupling plate 208 can be a ceramic PCB for high thermal stability. The coupling fixing device 206 has at least one precision guide pin / hole 209 to allow for repeatable alignment of the mechatronic interface 207.

[0038] Fiber ferrules 210 extend horizontally within the mechanical-optical interface 207. Each fiber in the AOC fiber bundle is assigned its own ferrule within the mechanical-optical interface 207. For each fiber, the received optical signal is reflected by optical device 211 into the vertical ferrule 212 of the mechanical-optical interface. In the example shown, fiber ferrules 210 and vertical ferrules 212 are connected at approximately a 90-degree angle, but other angles can be used. To receive optical signals from the fiber, a lens 213, built into the mechanical-optical interface 207, focuses the optical signal onto the APD. To transmit the signal to the fiber, lens 213 focuses the VCSEL laser output into the vertical ferrule 212 of the mechanical-optical interface, and the VCSEL laser output is reflected by optical device 211 into the fiber.

[0039] High-speed signals between coupling board 208 and PCB 201 can be connected via FPC 204 or through PCB vias. The FPC can be made of polyimide or Teflon for good high-frequency characteristics.

[0040] Figure 2B A side view of certain components of a fiber optic cable coupling assembly 200, including a PCB 201, a transceiver chip 202, an FPC 204, and a coupling fixing device 206, is depicted.

[0041] Figure 2C A side view of certain components of a fiber optic cable coupling assembly 200, including a mechanical-optical interface 207, a precision guide pin / hole 209, a fiber optic ferrule 210, an optical device 211, and a mechanical-optical interface vertical ferrule 212, is depicted.

[0042] Figure 3 An isometric view of a fiber optic cable coupling assembly 300 is depicted, which is another embodiment of the fiber optic cable coupling assembly 100. The fiber optic cable coupling assembly 300 includes a PCB 301, a transceiver chip 302, gold fingers 303, an FPC 304, a section 305, a coupling fixing device 306, a mechanical-optical interface 307, a fiber optic ferrule fixing device 308, and a coupling plate 309.

[0043] and Figure 2A , Figure 2B and Figure 2C Unlike the coupling fixing device 206 in the fiber optic cable coupling assembly 200, the coupling fixing device 306 is arranged in a vertical position perpendicular to the PCB 301. The advantage of this embodiment is that, compared to... Figure 2A , Figure 2B and Figure 2C Compared to the mechanical-optical interface 207, the mechanical-optical interface 307 is simpler because the optical signals received from and sent to the optical fiber do not need to change direction and do not require optical equipment 211.

[0044] The coupling fixing device 306 forms a structure that precisely matches the mechanical-optical interface 307, which guides the... Figure 1Multiple optical fibers are contained in the fiber optic cable bundle 102. A coupling fixing device 306 also forms protection around one or more silicon dies containing an APD, TIA, and laser driver. The VCSEL and APD are arranged in an array configuration within an alignment frame. The coupling fixing device 306 can be made of ceramic, metal, or plastic. The coupling fixing device 306 is glued to a coupling plate 309. The coupling plate 309 can be a laminated PCB. Alternatively, the coupling plate 309 can be a ceramic PCB for high thermal stability. The coupling fixing device 306 has at least one precision guide pin (or hole) to ensure alignment with the mechanical-optical interface 307. A ferrule extends horizontally inside the fiber optic ferrule fixing device 308. Each optical fiber in the fiber optic cable bundle 102 is assigned its own ferrule in the mechanical-optical interface 307. The optical fibers (optionally via lenses) are directly coupled to the APD or VCSEL array elements.

[0045] Figure 4A and Figure 4B Showing from Figure 3 Additional details of the coupling fixing device 306 of the fiber optic cable coupling assembly 300, wherein portions of the coupling fixing device 401 and the ferrule fixing device 402 are cut off for clarity. The FPC 405 connects the coupling plate to the main PCB. The coupling fixing device 401 and the ferrule fixing device 402 are perpendicular to the fiber bundle 403 (which is the fiber in the fiber optic cable bundle 102). The coupling fixing device 401 has at least one guide pin 404 (or hole) to ensure precise placement of the fiber ferrule 407 to ensure alignment. The coupling fixing device 401 also forms protection around one or more silicon dies having an APD, TIA, and laser driver 406. The VCSEL and APD are arranged in an array configuration. Preferably, at least two pairs of guide pins and holes are used to limit face-to-face rotation between the coupling fixing device 401 and the fiber ferrule fixing device 402. The fiber ferrule is constructed into the ferrule fixing device 402 in an array configuration having one or more rows. Each fiber in the fiber bundle 403 is fixed to the fiber ferrule at the exit hole of the fiber ferrule.

[0046] Figure 5 A vertical coupling fixing device 501 is shown. The vertical coupling fixing device 501 is... Figure 4A and Figure 4B A variation of the coupling fastener 401. The vertical coupling fastener 501 is coupled to multiple FPCs 502 and 503. The number of FPCs can be increased by expanding the vertical dimension of the coupling plate to support additional tape-adhesive (TAB) rows for connecting the FPCs. Figure 5 An embodiment with additional rows of APD 504 and VCSEL 505 is also shown to illustrate that the number of optical fibers can be increased to increase the AOC data rate.

[0047] Figure 6 A side view of the vertical coupling fixing device 602 is shown. The vertical coupling fixing device 602 can be used as... Figure 4A and Figure 4B The coupling fixing device 401 and Figure 5 An alternative to the vertical coupling fixture 501 is provided. The vertical coupling fixture 602 is coupled via PCB through-holes 606 to multiple FPCs 604 and FPC 605 connected to the back of the coupling plate 603. The number of FPCs can be increased by expanding the vertical dimension of the coupling plate to support additional rows of PCB through-holes. FPCs 604 and FPC 605 are connected to the AOC PCB 601.

[0048] Figure 7 A top view of the coupling plate 701 and its components, surrounded by the coupling fixing device 702, is shown. The coupling plate 701 can be a horizontal embodiment ( Figure 2A , Figure 2B , Figure 2C ) or vertical embodiment ( Figures 3 to 5 Part of the process. An APD array 703 is fabricated on a silicon die 704. The silicon die 704 includes a TIA and a laser driver; the TIA is used to amplify the signal from the APD array 703, and the laser driver is used to provide current to control the VCSEL array 705. The coupling plate 701 also contains both digital and analog control circuitry for adjusting the APD bias, TIA amplification, and laser drive current.

[0049] VCSEL array 705 is constructed on a reserved region (VCSEL region 706) having a photolithographically defined alignment frame 711. The alignment frame 711 also surrounds each APD in the APD array 703. Each VCSEL is connected to a silicon die 704 using wire bonding 710 and a photolithographically defined metal interconnect. Optionally, the rows of VCSEL array 705 and the rows of APD array 703 are aligned. The number of silicon dies 704 can be increased depending on the total bandwidth requirements of the AOC product.

[0050] The silicon die 704 is attached to the coupling plate 701 using standard silicon die packaging technology. The silicon die 704 is electrically connected to the coupling plate 701 using wire bonding 707 or through a through-silicon via (TSV) or a combination of both. Active circuitry for APD biasing, TIA, laser driver, and other control can be present anywhere on the silicon die 704 outside the APD array.

[0051] exist Figure 7In the example, two silicon dies 704 and 708 are mounted on a coupling plate 701. This embodiment also features a TAB area 709 for attaching the FPC. If high-speed signals are connected to the AOC PCB via PCB vias, the TAB area 709 is not required.

[0052] Figure 8 Alignment frame 801 for VCSEL and fiber placement is shown. Alignment frame 801 is photolithographically defined. Alignment frame 801 is... Figure 7 An example embodiment of alignment frame 711 is shown. Alignment frames 801 are defined using an organic material (e.g., polyimide, SU-8, or benzocyclobutene (BCB)) and are processed directly on the silicon wafer prior to dicing. Multiple photolithographically defined layers can be used to create cell walls 805 of appropriate height to facilitate VCSEL placement and alignment. Each VCSEL die 802 in the VCSEL array is placed in one alignment frame 801 of the alignment frames 801, and each APD 803 is placed in one alignment frame 801 of the alignment frames 801.

[0053] The alignment frame 801 also helps to precisely place the optical fiber on top of the APD 803. Furthermore, an optical lens 804 or a microlens can be placed within the alignment frame 801 on top of the APD 803 using photolithography to increase the intensity of the optical signal received by the active region of the APD. The APD 803 can be further optimized using photolithographically defined anti-reflective coatings and optical filters.

[0054] Figure 9 A cross-section of a collar retainer 901, usable within mechanical-optical interfaces 207 and 307, is shown. The collar retainer 901 includes a transmitting collar 902 and a receiving collar 903. The transmitting collar 902 and receiving collar 903 are flush with the bottom side of the collar retainer 901. Alignment frames are patterned on a silicon die 908. A hole 907 at the bottom of the transmitting collar 902 is offset below a hole 910 at the bottom of the receiving collar 903 to accommodate the height difference between the top of the VCSEL array 904 and the top of the alignment frame array 906 in which the APD 905 and APD lens 909 are placed. The gap between the transmitting collar 902 and the VCSEL 904 is kept as small as possible to maximize VCSEL coupling. Similarly, the gap between the receiving collar 903 and the APD 905 and APD lens 909 is kept as small as possible to maximize the APD signal.

[0055] exist Figure 2A , Figure 2B and Figure 2CIn an embodiment of the fiber optic cable coupling assembly 200, the transmitting ferrule 902 and the receiving ferrule 903 are ferrules 212 (roughly perpendicular to the optical fiber), and the VCSEL array 904 transmits the optical signal to the transmitting ferrule 902 and to the optical device 211 (in... Figure 2A , Figure 2B and Figure 2C As shown in the figure, the optical device 211 then transmits the optical signal to the optical fiber, and the APD 905 and the APD lens 909 receive the light from the optical device 211 that receives the optical signal from the optical fiber from the receiving ferrule 903.

[0056] exist Figure 3 In an embodiment of the fiber optic cable coupling assembly 300, the transmitting ferrule 902 and the receiving ferrule 903 contain optical fibers themselves and exchange optical signals directly with the VCSEL array 904, APD 905 and APD lens 909.

[0057] Figure 10 Another embodiment of the photolithographically defined alignment frame 1001 is shown. For clarity, the horizontal sidewalls are omitted from the figures. The alignment frame 1001 includes a VCSEL alignment frame 1002, which is etched into the silicon surface using bulk micromachining techniques commonly used in MEMS (Micro-Electro-Mechanical Systems) fabrication. Additional height can be added to the VCSEL alignment frame 1002, which is made of a photolithographically defined organic material. The APD alignment frame 1003 is also created using a photolithographically defined organic material.

[0058] Figure 11 A cross-section of the ferrule retainer 1101 is depicted. The top of the alignment frame for the VCSEL array 1108 and the top of the alignment frame for the APD array 1109 are on the same plane. The end 1111 of the transmitting ferrule 1106 and the end 1110 of the receiving ferrule 1107 are flush with the bottom side of the ferrule retainer 1101. This simplifies the design of the fiber optic ferrule retainer 1101 because no offset is required on the silicon die side of the retainer. Another advantage of this embodiment is that the signal electrodes can be connected to the VCSEL array using photolithography-defined metal—rather than wire bonding—as part of the silicon wafer manufacturing process. This is beneficial for the design and fabrication of high-frequency operations.

[0059] Figure 12A top view of an embodiment of coupling plate 1201 is shown, in which separate APD / TIA dies 1202 and laser driver dies 1203 are directly mounted on coupling plate 1201. For clarity, coupling fasteners are omitted in the figure. Dies 1202 and 1203 are connected to coupling plate 1201 using wire bonding or TSV, or a combination of both. Additional connections 1207 and 1208 can be formed between dies 1202 and 1203, and between dies 1205 and 1206, respectively, using fan-out wafer-level packaging technology. VCSEL arrays and alignment frames 1209 can be directly built onto coupling plate 1201. Alternatively, VCSEL arrays and alignment frames 1211 can be built onto a separate PCB 1210, which can be made of laminated or ceramic materials. This is indicated by dashed lines in the figure.

[0060] Figure 13 A cross-section of the ferrule retainer 1312 is depicted. The ferrule retainer 1312 is designed such that the ends of the transmitting ferrule 1313 and the receiving ferrule 1314 are flush with the bottom side of the retainer. If the alignment frame 1309 is directly built onto the coupling plate 1301, the hole 1315 for the transmitting ferrule 1313 is offset below the hole 1317 for the receiving ferrule 1314 to take into account the height difference between the top of the VCSEL array 1316 and the top of the APD alignment frame array 1318. If the alignment frame is built onto a separate PCB, the thickness of the separate PCB and the APD / TIA die can be adjusted so that the top of the alignment frame is on the same plane, such as... Figure 10 The embodiment described above simplifies the design of the collar retainer 1312 because no offset is required on the VCSEL side of the retainer. By keeping the PCB and silicon die at the same height, fan-out wafer-level packaging technology can be used to connect the signal electrodes to the VCSEL array. This is used in the creation of Figure 12 The connection 1207 and connection 1208 were completed in the same photolithography process.

[0061] Figure 14Another embodiment of the coupling plate is shown. The coupling plate 1401 includes silicon dies 1402 and 1404 (upper silicon dies) mounted on another silicon die 1403 (lower silicon die). For clarity, coupling fasteners are omitted in the figure. The lower and upper dies are assembled using 3D stacked silicon die packaging technology, which may include the use of wire bonding or TSV, or a combination of both. Any number of upper and lower dies can be present. Upper dies 1402 and 1404 include an APD array 1405 and a VCSEL array 1406 with photolithographically defined alignment frames. Upper dies 1402 and 1404 also include TIA and laser driver (LD) circuitry. For example, the lower die 1403 may contain complete transceiver chip circuitry. The transceiver circuitry includes RX / TX analog circuitry as well as DSP and retimer circuitry typically found on separate chips on AOC PCBs. This embodiment significantly reduces the size of the AOC PCB and simplifies / reduces high-speed signal paths, thereby reducing overall power requirements.

[0062] Figure 15 Electrical aspects of the embodiments described herein are illustrated. The APD 1506, VCSEL 1507, TIA 1508, and laser driver 1509 are integrated into a single die or package 1501, which is mounted on a coupling plate 1503. Transceiver functions such as receiver 1510, transmitter 1511, DSP 1512, DSP 1513, and gearbox 1514 are integrated into separate dies or packages 1502 on the main AOC PCB 1504. For each APD 1506 and TIA 1508 pair, the high-frequency performance of the APD 1506 critically depends on the parasitic resistance, inductance, and capacitance (RLC) 1505 between the APD 1506 and TIA 1508. By moving the APD 1506 and TIA 1508 closer together on the same chip, these parasitic RLC 1505s are significantly reduced by several orders of magnitude. Silicon APDs have a very high intrinsic gain-bandwidth product. By integrating the APD 1506 close to the TIA 1508 on the same silicon die, the reduction in photodiode bandwidth caused by the extrinsic RLC 1505s is minimized.

[0063] The integrated system described in this invention has several significant advantages. First, in various embodiments, the bill of materials (BOM) cost of the integrated system is greatly reduced due to the elimination of multiple components (i.e., photodiodes). Second, manufacturing costs are significantly reduced because there is only a single passive alignment step with a precision-machined coupling plate and ferrule fixing device. Third, there is a yield advantage because each fiber in the array can be individually optimized through closed-loop control of the AOC performance metric. The third point will be further discussed in the following figures.

[0064] Figure 16 The integration method of the embodiments described herein illustrates how it allows for closed-loop control and optimization of AOC performance metrics.

[0065] The optimization circuit 1606 generates and outputs settings for APD bias, the TIA response of the receive-side (RX) APD die 1615, and the LD waveform of the transmit-side (TX) APD die 1616. These settings affect the performance characteristics of the RX-side APD 1618, the RX-side TIA 1619, and the TX-side VCSEL 1620. Additionally, the optimization circuit 1606 outputs settings for the DSP filters in the DSP chip 1617. The feedback input to the optimization circuit 1606 can be an analog or digital signal from the RX PCB 1603 or the TX PCB 1605.

[0066] The optimization circuit 1606 can exist on both RX PCB 1603 and TX PCB 1605, as AOC cables are typically bidirectional. Each circuit can work together, with one designated as the primary circuit and the other as the secondary circuit. Alternatively, each circuit can operate independently, or one of the circuits can be disabled. The feedback signals 1601 and 1614 used for optimization can originate from either RX PCB 1603 or TX PCB 1605 and can be analog or digital signals.

[0067] There are two feedback control paths. Signaling for control path 1602 is contained within an AOC PCB. Signaling for control path 1604 requires communication between the RX and TX ends of the AOC cable bundle 1607. This is accomplished either via test / calibration equipment 1610 or via signaling 1621 for the control path through the AOC cable bundle 1607. Signaling 1621 for the control path can use any wired or self-organizing optical protocol. Examples of wired signaling protocols include JTAG and I2C, but any custom signaling protocol can be used. This requires at least two wires to be routed between the RX PCB 1603 and the TX PCB 1605. For optical signaling, several fiber optic paths are allocated to transmit optimized inputs and settings for other fiber optic paths within the AOC cable bundle 1607. Alternatively, low-frequency signals can be transmitted through each fiber, including optimized inputs and settings. Fiber optics can carry both high-frequency and low-frequency signals simultaneously. The optimization circuit 1606 operates the APD / TIA on the RX side of the cable and the VCSEL / LD on the TX side of the cable, as well as the transceiver chips on the TX / RX side. The optimized settings are written to one-time programmable or non-volatile memory registers (OTP / NVM) 1611, 1612, and 1613.

[0068] Figure 17 The types of control that can be set by optimization circuit 1703 are further illustrated. APD bias 1701 and TIA response 1702 improve the detection of the received signal by APD 1708 and TIA 1707. Laser driver (LD) waveform 1704 affects the quality of the transmitted signal from VCSEL 1706. DSP filter settings 1705 optimize the performance of DSP 1709. The input to optimization circuit 1703 is derived from APD / TIA signals 1710 and / or DSP metrics 1711 and passed through feedback control circuit 1712.

[0069] The entire system can be optimized using AOC cables to maximize performance or minimize power consumption. Furthermore, each RX-to-TX path within the bundle can be individually optimized during manufacturing and throughout the cable's lifespan. As another example, for shorter cable lengths or lower data rates, simpler DSP algorithms can be used, or the DSP can be omitted entirely, resulting in application-specific power savings.

[0070] During cable manufacturing, the optimization circuit 1703 is used in a test / calibration apparatus to compensate for manufacturing variations in AOC components and alignment, which increases AOC cable yield. Another method to increase AOC production is to add redundant fiber optic cables to the fiber bundle. Due to component integration and single passive alignment used in this invention, adding redundant fiber requires only a small cost.

[0071] By activating the optimization circuit 1703 during field operations, end users gain several key benefits. First, adjustments can be made to compensate for changes in AOC components, connected systems, or the external environment. This improves the field reliability of AOC cable deployments. Second, cable maintenance is simplified. Problems detected in data links by connected equipment can be remotely identified and categorized by isolating poorly performing fiber optic links and checking whether the cable is the root cause. This software-defined maintenance workflow reduces data center maintenance costs.

[0072] The fiber core diameter in multimode fiber is 50 micrometers. Typically, one APD corresponds to each fiber. Due to the high sensitivity of integrated silicon APDs, each APD will be much smaller than 50 micrometers. This is especially true for APDs that have been optimized for high-frequency operation. This leads to the possibility of using multiple APDs for each fiber. Figure 18A Alignment boxes 1801, 1802, and 1803 are depicted, each of which receives an optical fiber. Alignment box 1801 contains one APD, alignment box 1802 contains two APDs, and alignment box 1803 contains four APDs. Figure 18B Alignment box 1802 containing two APD 1804s is shown. A typical area of ​​the multimode fiber core is shown by circle 1805. A single multimode fiber will be coupled to both APD 1804s.

[0073] The APDs within a single alignment frame can be independently biased to achieve different levels of signal amplification. Most importantly for this invention, the APDs can be used as mixers. Figure 18C The demodulation circuit 1806 using an APD is depicted. A frequency generator 1807 generates reference signals to modulate the APD operating in the linear portion of the APD amplification curve. In this example, n pairs of reference signals are generated. The first pair is V applied to APDs 1808-1a and 1808-1b. r cos(w1t+p1) and V r sin(w1t+p1), where APD 1808-1a is used for the in-phase component and APD 1808-1b is used for the quadrature component shifted by 90 degrees. Each APD is followed by a TIA1809 and a low-pass filter (LPF) 1810, which allows further processing of these two signals in downstream circuitry 1811 to detect phase and amplitude. This design is also followed for the remaining pairs of n pairs of reference signals. For example, the nth pair is V r cos(w) n t+p n ) and V r sin(w) n t+p nThese methods are applied to APD 1808-NA and 1808-nb. This approach allows for the demodulation of phase information in optical signals using less complex transceiver circuitry and facilitates the use of higher-order quadrature amplitude modulation (QAM) schemes to increase data rates.

[0074] Figure 19 Another embodiment with multiple APDs per fiber is shown. Alignment box 1901 has four APDs 1903 within a region of the multimode fiber core, as shown in circle 1902. A single multimode fiber is coupled to all four APDs. Each quadrant 1904 of the alignment box is associated with a different bandpass optical filter to filter narrowband light wavelengths. The optical filters can be defined by deposition and photolithography. This design enables high-bandwidth multimode fibers to support wavelength division multiplexing (WDM) with up to four signal wavelengths 1905 at AOC distances up to 50 m.

[0075] Figure 20A An embodiment is shown with a VCSEL 2002 and an APD 2006 within the same alignment box 2001. This embodiment uses the APD 2006 to monitor the output level of the VCSEL 2002, and the APD output signal can be... Figure 17 Another input to the optimized circuit 1703 is provided. The VCSEL die size and the position of the VCSEL's active light-emitting region 2005 can be customized. The VCSEL's active region 2005 is surrounded by the fiber core 2004 and the fiber cladding 2003. The APD 2006 is integrated on the die inside the alignment frame 2001 and adjacent to the VCSEL 2002. Even though the APD 2006 is outside the fiber cladding 2003, the APD 2006 can use reflected light from the fiber to monitor the VCSEL 2002. Adding the APD 2006 in this way does not increase cost because the APD 2006 can be added as part of silicon integration.

[0076] Figure 20B Another embodiment is shown with VCSEL 2008 and APD 2012 within the same alignment frame 2007. This embodiment has both VCSEL active region 2011 and APD 2012 within fiber core 2009. The fiber can be used bidirectionally, serving as both a transmitter (via VCSEL 2008) and a receiver (via APD 2012). For example, this could be useful in communications according to communication standards with asymmetric modes that require unequal numbers of RX and TX paths to increase the transmission rate in one direction. This embodiment can be used as either an RX path or a TX path as needed.

[0077] Figure 21System 2100 is depicted. System 2100 includes devices 2101a and 2101b, and electrical connectors 101a and 101b (which are... Figure 1 The instantiation of electrical connector 101), fiber optic cable coupling assemblies 100a and 100b (which are Figure 1 (Instantiation of fiber optic cable coupling assembly 100) and fiber optic cable bundle 102. Devices 2101a and 2101b can be servers, routers, switches, storage devices, or any other electrical equipment.

[0078] During operation, device 2101a sends a signal to device 2101b by transmitting an electrical signal through electrical connector 101a. The electrical signal is converted into an optical signal by fiber optic cable coupling assembly 100a, and the optical signal is transmitted through fiber optic cable bundle 102. The optical signal is received by fiber optic cable coupling assembly 100b. The optical signal is converted into an electrical signal by fiber optic cable coupling assembly 100b, and the electrical signal is transmitted to device 2101b through electrical connector 101b. Device 2101a can send a signal to device 2101b in reverse using the same path.

[0079] It should be noted that, as used herein, both the terms “above” and “on” include “directly on” (without intermediate material, elements, or space between them) and “indirectly on” (with intermediate material, elements, or space between them). Similarly, the term “adjacent” includes “directly adjacent” (without intermediate material, elements, or space between them) and “indirectly adjacent” (with intermediate material, elements, or space between them), “mounted to” includes “directly mounted to” (without intermediate material, elements, or space between them) and “indirectly mounted to” (with intermediate material, elements, or space between them), and “electrically coupled” includes “directly electrically coupled to” (without intermediate material or elements between them that electrically connect the elements together) and “indirectly electrically coupled to” (with intermediate material or elements between them that electrically connect the elements together). For example, forming elements “on a substrate” can include forming elements directly on the substrate where there is no intermediate material / element between them, and forming elements indirectly on the substrate where there is one or more intermediate materials / elements between them.

Claims

1. A fiber optic cable coupling assembly, comprising: A coupling plate, the coupling plate comprising multiple lasers and multiple photodiodes; as well as Mechatronic interface, the mechatronic interface comprising: A plurality of rings, wherein each of the plurality of lasers is aligned with a ring in the plurality of rings; as well as The second plurality of rings, wherein each of the plurality of photodiodes is aligned with a ring in the second plurality of rings.

2. The fiber optic cable coupling assembly as described in claim 1, characterized in that, The laser is a vertical cavity surface-emitting laser.

3. The optical fiber cable coupling assembly as described in claim 1, characterized in that, The photodiode is an integrated silicon photodiode capable of operating in avalanche mode.

4. The optical fiber cable coupling assembly as described in claim 1, characterized in that, The first plurality of ferrules and the second plurality of ferrules contain optical fibers from the optical fiber cable bundle.

5. The fiber optic cable coupling assembly as described in claim 1, characterized in that, The mechatronic interface further includes: A third plurality of collars, the third plurality of collars being connected to the first plurality of collars at approximately a 90-degree angle; and A fourth plurality of collars, which are connected to the second plurality of collars at an angle of approximately 90 degrees.

6. The fiber optic cable coupling assembly as described in claim 5, characterized in that, The third and fourth plurality of collars contain optical fibers from the optical fiber cable bundle.

7. The fiber optic cable coupling assembly of claim 6, further comprising a plane mirror or prism in the third plurality of ferrules and the fourth plurality of ferrules.

8. The fiber optic cable coupling assembly of claim 1, further comprising a transceiver coupled to the plurality of lasers and the plurality of photodiodes.

9. The fiber optic cable coupling assembly of claim 8, further comprising an electrical connector connected to the transceiver.

10. A coupling plate assembly, comprising: Coupler plate; A silicon die, wherein the silicon die is mounted on the coupling plate; A first plurality of alignment frames on the silicon die, each of the first plurality of alignment frames containing a laser; as well as A second plurality of alignment frames on the silicon die, each frame of the second plurality of alignment frames containing one or more photodiodes.

11. The coupling plate assembly as claimed in claim 10, characterized in that, The first plurality of alignment frames and the second plurality of alignment frames are defined by photolithography.

12. The coupling plate assembly as claimed in claim 11, characterized in that, The first plurality of alignment frames and the second plurality of alignment frames form an alignment frame array.

13. The coupling plate assembly as claimed in claim 10, characterized in that, The laser is a vertical cavity surface-emitting laser.

14. The coupling plate assembly as claimed in claim 10, characterized in that, The photodiode is an avalanche photodiode.

15. The coupling plate assembly of claim 10, wherein the top surface of the laser and the top surface of the photodiode are approximately in the same plane.

16. The coupling plate assembly of claim 10, further comprising a second die mounted on the coupling plate.

17. The coupling plate assembly as claimed in claim 10, characterized in that, The silicon die includes a transimpedance amplifier coupled to the photodiode.

18. The coupling plate assembly as claimed in claim 17, characterized in that, The silicon die includes a laser driver coupled to the laser.

19. The coupling plate assembly as claimed in claim 10, characterized in that, The alignment frame in the second plurality of alignment frames includes a plurality of photodiodes forming a mixer to demodulate the quadrature amplitude modulation signal.

20. The coupling plate assembly as claimed in claim 10, characterized in that, The alignment frame in the second plurality of alignment frames contains a plurality of photodiodes for performing wavelength division multiplexing.

21. A control system for an optical fiber cable coupling assembly, the control system comprising: Photodiode bias control circuit; Transimpedance amplifier; as well as An optimization circuit is provided to generate settings for the photodiode bias control circuit and the transimpedance amplifier.

22. The control system of claim 21, further comprising: Digital signal processor; The optimization circuitry generates settings for the digital signal processor.

23. The control system of claim 21, further comprising: An alignment frame, comprising a laser and a photodiode, wherein the photodiode provides a signal to the optimization circuit indicating the output level of the laser.

24. A control system for an optical fiber cable coupling assembly, the control system comprising: Laser driver; as well as An optimization circuit is provided for generating settings for the laser driver.

25. The control system of claim 24, further comprising: Photodiode bias control circuit; as well as Transimpedance amplifier; The optimized circuitry generates settings for the photodiode bias control circuit and the transimpedance amplifier.

26. The control system of claim 24, further comprising: An alignment frame, comprising a laser and a photodiode, wherein the photodiode provides a signal to the optimization circuit indicating the output level of the laser.

27. A coupling plate assembly, comprising: Coupler plate; A silicon die, wherein the silicon die is mounted on the coupling plate; as well as An alignment frame on the silicon die, the alignment frame including a laser and a photodiode.

28. The coupling plate assembly of claim 27, wherein the photodiode outputs a signal indicating the output level of the laser.

29. The coupling plate assembly as claimed in claim 27, characterized in that, In the first mode, the laser outputs light into the optical fiber, and in the second mode, the photodiode outputs a signal in response to receiving light from the optical fiber.

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