Method and apparatus for matching impedance of optical components using tapered transmission lines

Abstract

A method and apparatus for matching different impedances of an optical component and a package for optical communication using a tapered transmission line (or cone) are provided. The cone can be configured to include a first portion, a second portion, and a third portion, each portion corresponding to a different component. As an example, the first portion of the cone can be configured to be assigned to a driver of a flexible joint on a printed circuit board (PCB), the second portion of the cone can be configured to be assigned to a flexible circuit, and the third portion of the cone can be configured to be assigned to a transistor outline (TO) and a submount including a directly modulated laser (DML). The cone is configured to minimize the amount of impedance mismatch between the optical component and the package.

Description

Technical Field

[0001] The present disclosure relates to design and implementation techniques for matching the impedance of optical components, for example, by means of tapered transmission lines in optical devices or equipment, and in particular, to methods and techniques for matching different impedance values ​​of directly modulated lasers (DMLs) and packages using tapered transmission lines. Background Art

[0002] A common problem associated with the development of optical subassemblies (OSAs) is the impedance mismatch between the test equipment and the device under test (DUT). Currently, there are several examples of impedance mismatch. For example, there are examples of impedance mismatch associated with directly modulated lasers (DMLs) and other components. DMLs are typically distributed feedback (DFB) lasers or Fabry-Perot (FP) lasers, which have an inherent impedance of about 10 ohms. One of the internal components is a transmitter optical subassembly (TOSA), which is responsible for converting electrical signals into optical signals and then transmitting the optical signals through an optical fiber channel. In addition, the DML transmitter circuit is typically designed to have an impedance of 25 ohms, so the TOSA package has an impedance of 25 ohms. As a result, an example of impedance mismatch will occur, and in order to solve this problem, a matching resistor can be added in series with the DML to match the impedance with 25 ohms. In addition, the DML can be mounted on a submount and encapsulated in a TOSA package with an impedance of 25 ohms, and the TOSA package is electrically connected to the printed circuit board assembly through a flexible circuit. In this case, there will be a significant impedance mismatch between the DML and peripheral devices such as submounts, TOSA packages, and flex circuits, causing design issues and degrading system performance.

[0003] As an example, many test engineers have difficulty characterizing the performance of a DML, DML's Chip-on-Carrier (CoC), or packaged DML TOSA when the DML TOSA is based on a 25-ohm design. When measuring a DML CoC or DML TOSA, test engineers use the impedance conversion function provided by a lightwave component analyzer (LCA) with an impedance of 50 ohms. However, to properly use the impedance conversion function, accurate calibration of the test board is usually required. In addition, due to issues such as where the interface point between 50 ohms and 25 ohms will be located and how to calibrate the impedance to the interface point, which often trouble many test engineers, there are several options for developing an evaluation board for a DML TOSA.

[0004] In addition, for DML chip characterization such as S parameters, the DML chip is usually mounted on the CoC, so it can be characterized relatively accurately using the impedance conversion function of the LCA through proper calibration. However, when DML TOSA samples are to be provided to customers, the problem may become complicated because the customer's test equipment will usually have an impedance of 50 ohms and will use a 50 ohm system for measurement without proper calibration. Therefore, when the customer does not have a well-calibrated evaluation board, it will be difficult for the customer to accurately measure the TOSA performance. In addition, the same problem may occur when the customer tries to use a pulse pattern generator (PPG) with an impedance of 50 ohms to view the optical performance.

[0005] Furthermore, in the case of Mach-Zehnder modulator (MZM) designs, the MZM is typically packaged in a package with an impedance value of 50 ohms, but the impedance of a typical InP-based MZM chip may be in the range of 20 ohms to 40 ohms, resulting in an impedance mismatch. Therefore, the submount needs to have an impedance of 50 ohms, and in addition, the termination must also have a typical impedance of 50 ohms. Therefore, for the characterization of the MZM chip, the same test issues as the DML characterization may occur. Therefore, the CoC has a 50 ohm line, and when testing the MZM chip mounted on the CoC, it also has the same calibration issues as the DML TOSA because the impedance value of the submount is 50 ohms. In some other cases, some engineers may try to drive a 50 ohm EML TOSA with a 25 ohm driver IC, or drive a 50 ohm driver IC with a 25 ohm TOSA. However, these examples are rare cases, although such experimental work can be attempted in various embodiments of the transceiver.

[0006] Therefore, there is still a prominent problem of impedance mismatch in optical component design and transceiver implementation.Therefore, there is still a need for enhanced technology for solving the significant impedance difference between optical components to be assembled in a package. Summary of the invention

[0007] In the prior art, there is a need to solve the impedance matching problem. For example, effective matching of different impedance values ​​will solve many difficulties involved in the testing of optical components such as directly modulated laser (DML) lasers, Mach-Zehnder modulators (MZMs), and will also solve problems encountered in the implementation of evaluation boards for various optical components such as DML transmitter optical subassemblies (TOSAs) and / or MZM TOSAs.

[0008] Today, all directly modulated lasers (DMLs) in transistor outline (TO) packages are assembled in a 25 ohm header or a 25 ohm TO header. The impedance of all commercially available DML driver integrated circuits (ICs) is approximately 25 ohms. Thus, in the prior art, the impedance from the driver IC to the TO pin input plus the submount is always matched to 25 ohms, even if the actual impedance of the DML is approximately 10 ohms. In addition, it is noted that when the impedance of the DML driver IC is approximately 25 ohms (single-ended) and the DML impedance is approximately 10 ohms, this results in an S-parameter S11 (reflection coefficient or return loss) of approximately -7.3 dB, which can be improved by using various aspects of the present technology.

[0009] In one aspect of the present disclosure, a system, technique, or method is provided for matching the impedance of a directly modulated laser (DML) using a tapered transmission line. As an example, the tapered transmission line or cone is configured to include a first portion, a second portion, and a third portion. The first portion of the cone is configured to be assigned to a driver of a flexible joint on a printed circuit board (PCB) or printed wiring board (PWB), the second portion of the cone is configured to be assigned to a flexible circuit, and the third portion of the cone is configured to be assigned to a TO and submount including the DML. In addition, in one aspect of the present disclosure, the impedance of the TO package is modified to obtain an accurate cone design because the impedance of the TO package is also part of the cone.

[0010] In one aspect of the present disclosure, the DML is enclosed in a package, which may be a TO, ceramic box, combination on board optics (COBO), or chip on board (COB) package.

[0011] In one aspect of the present disclosure, the first portion of the cone is configured to correspond to the TO and the internal submount.

[0012] In another aspect of the present disclosure, the first portion of the cone includes a first three segments, the second portion includes a second fifteen segments, and the third portion includes a third three segments.

[0013] In another aspect of the present disclosure, the first and third sections are relatively short, and the impedance values ​​of the first and third sections can be respectively approximated to the average of the three sections, sometimes at the expense of slightly reduced performance.

[0014] In another aspect of the present disclosure, an optical communication device or equipment is provided, such that the optical communication device or equipment may include a DML disposed in a package, a DML driver IC, and a cone disposed between the DML and the DML driver IC. The cone is configured to match different impedances of the DML driver IC, the DML, and / or the package.

[0015] In another aspect of the present disclosure, the impedance of the DML may be approximately 10 ohms and the impedance of the DML driver IC may be approximately 25 ohms.

[0016] In another aspect of the present disclosure, the cone of an optical communication device or equipment may include a first portion, a second portion, and a third portion. The first portion is allocated to the driver of the flexible joint on the PCB or PWB, the second portion is allocated to the flexible circuit, and the third portion is allocated to the TO and the submount.

[0017] In another aspect of the disclosure, a first portion of a cone in an optical communication device or equipment includes a first set of three segments, a second portion of the cone includes a second set of fifteen segments, and a third portion of the cone includes a third set of three segments.

[0018] In another aspect of the present disclosure, the impedance of the first and third portions of the cone in an optical communication device or equipment are respectively approximated to the average of the three segments, sometimes at the expense of slightly reduced performance.

[0019] In another aspect of the present technology, an optical communication device is provided. The optical communication device is configured to include a package having a first impedance, an optical component having a second impedance, and a cone coupled to the optical component and the package. The cone coupled to the optical component and the package is configured to minimize the amount of impedance mismatch between the first impedance and the second impedance.

[0020] In another aspect of the present disclosure, the optical components of the optical communication equipment may be enclosed in a package. Alternatively, part of the optical components of the optical communication equipment may be outside the package.

[0021] In another aspect of the present disclosure, optical communication equipment may include a directly modulated laser, a Mach-Zehnder modulator laser, or a vertical cavity surface emitting laser as an optical component.

[0022] In another aspect of the present disclosure, a cone of optical communication equipment may be designed to match the impedance of an optical component to the impedance of a package.

[0023] In another aspect of the present disclosure, the package may be a TO, ceramic box, COBO or COB package.

[0024] In another aspect of the present disclosure, a cone of optical communication equipment is designed to match a second impedance of an optical component to a first impedance of a package.

[0025] Thus, implementations of one or more aspects of the present technology may provide numerous benefits because impedance matching is superior to prior art, including lower drive voltage and less power consumption, less reflections, less RF radiation, and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] These and other features, aspects and advantages of the present disclosure will become better understood from the following description, appended claims and accompanying drawings, in which:

[0027] Figure 1 is a diagram conceptually illustrating an embodiment of the present disclosure;

[0028] Figure 2A , 2B and 2C are diagrams illustrating a perspective view of an example embodiment in one aspect of the present disclosure;

[0029] Figure 2D is a diagram conceptually illustrating impedance matching of an example embodiment in one aspect of the present disclosure;

[0030] Figure 2E is a reflection coefficient response of an example embodiment in one aspect of the present disclosure;

[0031] Figure 3 is a reflection coefficient response of an example embodiment in one aspect of the present disclosure;

[0032] Figure 4 is an example cone design in one aspect of the present disclosure;

[0033] Figure 5A and 5B is an output response of an example embodiment in one aspect of the present disclosure;

[0034] Fig. 6A and 6B illustrates an output response of an example embodiment in one aspect of the present disclosure;

[0035] Fig. 7A and 7B illustrates a reflection coefficient response of an example embodiment in one aspect of the present disclosure;

[0036] Fig. 8A and 8B illustrates a reflection coefficient response of an example embodiment in one aspect of the present disclosure;

[0037] Fig. 9 is another example cone design in one aspect of the present disclosure;

[0038] Fig. 10A , 10B and 10C illustrate an output response of an example embodiment in one aspect of the present disclosure;

[0039] Fig.11A and 11B illustrates an output response of an example embodiment in one aspect of the present disclosure;

[0040] Fig. 12Aand 12B illustrates an output response of an example embodiment in one aspect of the present disclosure;

[0041] Fig.13A and 13B illustrates an output response of an example embodiment in one aspect of the present disclosure;

[0042] Fig.14A and 14B illustrates an output response of an example embodiment in one aspect of the present disclosure;

[0043] Fig.15A and 15B illustrates an output response of an example embodiment in one aspect of the present disclosure;

[0044] Fig.16A and 16B shows an output response of an example embodiment in one aspect of the present disclosure;

[0045] Fig.17A and 17B illustrates an output response of an example embodiment in one aspect of the present disclosure; and

[0046] Fig.18A and 18B An output response of an example embodiment in one aspect of the present disclosure is illustrated. DETAILED DESCRIPTION

[0047] A detailed description of illustrative examples will now be set forth below in conjunction with various drawings. The following description is intended to be exemplary and in no way limits the scope of the present technology. It provides detailed examples of possible implementations and is not intended to represent the only configuration in which the concepts described herein can be practiced. Thus, the detailed description includes specific details for providing a thorough understanding of the various concepts, and it is noted that these concepts can be practiced without these specific details. In some cases, well-known structures and components are shown in block diagram form to avoid confusing these concepts. It is noted that the same reference numerals are used in the drawings to represent the same elements and features.

[0048] Additionally, methods and apparatus of example embodiments that implement various features of the present technology are described herein. References to "one embodiment" or "an embodiment" in the description herein are intended to indicate that a particular feature, structure, or characteristic described in conjunction with the example embodiment is included in at least one embodiment of the present technology or disclosure. The phrases "in one embodiment" or "an embodiment" or "an example embodiment" in various places in the description herein do not necessarily all refer to the same embodiment.

[0049] In the following description, specific details are given to provide a thorough understanding of the example embodiments. However, one of ordinary skill in the art will appreciate that the example embodiments can be practiced without these specific details. Well-known circuits, structures, and techniques may not be shown in detail to avoid obscuring the example embodiments (e.g., circuits in block diagrams, interconnections, etc.).

[0050] Additionally, the term "transistor outline (TO)" as used herein refers to an industry standard governing the design and dimensions of current conducting microelectronic packages and housings, as the common and customary meaning used in the optical industry. A typical TO package may include two components: a TO header and a TO cap. The TO header is configured to provide power to the components of the package, and the TO cap is configured to ensure smooth transmission of optical signals, including an optical transmitter, such as a laser diode, and an optical receiver, such as a photodiode.

[0051] In addition, although the exemplary embodiments herein describe various aspects of the present technology with reference to standard designs and sizes of TO packages, the application of the present technology is not limited thereto and can be applied to packages of other designs, sizes, and types. As an example, the package can be a TO, a ceramic box, a combination of optical devices on a board (COBO), a chip on a board (COB) package, or any other package type.

[0052] In the present disclosure, the term "DML" as used herein shall refer to a directly modulated laser or directly modulated laser diode and / or directly modulated vertical cavity surface emitting laser (VCSEL). In general, directly modulated lasers (DMLs) provide cost-effective transmitters compared to externally modulated lasers (EMLs) that use continuous wave lasers and then electro-absorption modulators (EAMs). An advantage of DMLs is that they are simple relative to EMLs, and thus various embodiments of the present technology are presented using DMLs for illustrative purposes. However, the application of the present technology disclosed herein is not limited thereto.

[0053] In addition, sometimes, DML is also called distributed feedback (DFB) laser due to its structure, in which a single chip is used with simple circuits, thereby occupying a small space and consuming low power. It places information on the light beam by modulating the on / off electrical input generated by the driver integrated circuit (IC), which is directly applied to the laser diode that generates the modulated optical signal output. Therefore, the general application of DML is for lower data rate applications and shorter distances.

[0054] Furthermore, even assuming that the impedance of the DML is purely resistive, its impedance is a complex impedance of about 10 ohms. Also note that adding a small resistor will reduce the effect of the complex impedance of the DML. And the addition of a small resistor will slightly increase the load impedance and provide better impedance matching and overall performance. Thus, slightly reducing the source impedance and slightly increasing the load impedance may also help achieve better impedance matching.

[0055] In one aspect of the present disclosure, in order to better understand impedance matching, a brief description of impedance matching of two impedances Z1 and Z2 is provided herein, such as Figure 1 As shown in . Using a tapered transmission line within a specific frequency range, two impedances Z1 and Z2 can be matched. Impedance mismatch or impedance transformation is a traditional problem in radio frequency (RF) and microwave applications. As an example, the RF system may be a 50 ohm based system and the Yagi antenna may have an impedance value of about 73 ohms. Therefore, Figure 1 This example provides one of the traditional problems of impedance mismatch. A general method of dealing with this impedance mismatch can be described in an article published in 1956 by RW Klopfenstein, entitled "A Transmission Line Taper of Improved Design", Proceedings of the IRE, pp. 31-35, January 1956, the contents of which are incorporated herein by reference in their entirety. It should also be noted that the use of a tapered line impedance matching network can be implemented in a variety of techniques, and the present technology is not limited to the embodiments described in the current disclosure. That is, the impedance matching network can be designed with a continuous cone or a tapered transmission line using a variety of techniques.

[0056] However, this method or similar methods or techniques have not been applied to the field of optical communications, especially in the design of various optical components, including transmitter optical subassemblies (TOSAs), receiver optical subassemblies (ROSAs), and other optical transceivers in different packages. The present disclosure provides the application of various techniques or methods for matching impedance using tapered transmission lines, especially in the design of TOSAs and optical transceivers. However, the application of the present disclosure is not limited to this.

[0057] In one aspect of the present disclosure, a tapered transmission line is used to reduce impedance mismatch in the design of an optical device or equipment. For example, the use of a tapered transmission line in the design of an optical device can enable several application areas. As an example, in one or more aspects of the present disclosure, an impedance converter using a tapered transmission line (or cone) can be applied to, among other things, the following situations: (i) characterization of a 25 ohm TOSA based on a test equipment with an impedance of 50 ohms, (ii) impedance matching of a DML TOSA between a submount / TOSA package and a DML chip with an impedance of 10 ohms, (iii) impedance matching between a 25 ohm driver IC and a 50 ohm TOSA, (iv) impedance matching between a 50 ohm driver IC and a 25 ohm TOSA, (v) impedance matching between a 50 ohm driver IC and a 20-30 ohm Mach-Zehnder modulator (MZM), (vi) impedance matching in VCSEL design, and many other situations. In the examples disclosed herein, it should also be noted that the DML has very low impedance and often results in impedance mismatches due to different impedance values ​​between components as described above (e.g., 10 ohms vs. 25 ohms.) Thus, while an absorbing resistor-capacitor (RC) circuit may be implemented between the transmission line and ground to attempt to address the impedance mismatch, a tapered transmission line or cone may be used or implemented to match different impedance values ​​in different types of packages, such as ceramic boxes, TO, COBO, or COB packages.

[0058] First, you can use Figure 2A-2C The tapered transmission line shown in Figure 1 can be used to achieve impedance matching over a very wide bandwidth. FIG. 2A to FIG. 2C Different perspective views of example embodiments of the present technology are shown. Figure 2A-2C are different perspective views of an example embodiment of a TO-type TOSA. Figure 2A is a side view of an example embodiment according to one aspect of the present disclosure. In an example, a DML is disposed on a submount in a TO. Figure 2B is a bottom perspective view of an example embodiment showing an example cone disposed on a submount according to one aspect of the present disclosure. Figure 2C is a bottom view of an example embodiment showing a cone disposed on a flexible circuit according to one aspect of the present disclosure. In addition, in one aspect of the present disclosure, although Figure 2A-2C The cone in the example of FIG. 5 is shown as being located on the submount and the flexible circuit, but the location of the cone may not be limited thereto, and thus the cone may be disposed at any location between the DML and the DML driver IC.

[0059] Figure 2Dis a diagram conceptually illustrating another example embodiment of the present technology. In the example, a tapered transmission line (or cone) is designed or implements an impedance match between a driver output impedance of 25 ohms (Z1) and a DML impedance of 10 ohms (Z2). In the example, the matching impedance of the cone can be implemented via two separate impedances or implementations (e.g., a first portion of the cone for the flex circuit and a second portion of the cone for the submount divided under the Zx impedance of the TO header). Alternatively, as described above, the matching impedance can be implemented with a single cone.

[0060] Figure 2E A diagram conceptually illustrating impedance matching according to an embodiment of one or more aspects of the present disclosure is illustrated. Figure 2E The reflection response of a tapered transmission line over a GHz frequency bandwidth, for example, the reflection coefficient response, is shown. Figure 2D As shown in , reflections above 10 GHz (e.g., F min ) is maintained below -20 dB. That is, in an example, according to one aspect of the present disclosure, using a cone design including a tapered transmission line, the reflection of the passband is about -20 dB. In addition, in an example, the maximum reflection coefficient or S11 value at zero frequency can be determined by: 20*log((Z2-Z1) / (Z1+Z2)), where Z1 is the first impedance and Z2 is the second impedance. In addition, in the cone design, F can be specified min and above F min That is, for given values ​​of dielectric material, such as dielectric constant and material thickness, the length of the cone design (or cone) can be determined and / or varied according to the cone design theory described in Klopfenstein, which is incorporated by reference in its entirety as described above. Thus, in one embodiment, since F min At lower frequencies, the length of the cone to be designed can be increased based on the desired matching characteristics as described below.

[0061] For illustration purposes, this article provides a design example of an impedance converter (or impedance matching) from 50 ohms to 25 ohms based on the use of a tapered transmission line. Note that the 50 ohm to 25 ohm conversion may be important in the design of an evaluation board for characterizing a 25 ohm DML TOSA, in the design of a submount for characterizing a Mach-Zehnder modulator (MZM), and in the design of a printed wiring board (PWB) between a 50 ohm driver IC and a 25 ohm DML TOSA.

[0062] In one aspect of the present disclosure, in one example, it is necessary to match different impedances between a 50 ohm measurement device (evaluation board) and a 25 ohm DML TOSA. In this case, a design such as Figure 3The reflection coefficient response shown in Figure 4 The cone design shown in . In the example, the maximum reflection coefficient or S11 value at zero frequency can be determined by the following formula: 20*log((Z2-Z1) / (Z1+Z2)), where Z1 is 25 ohms and Z2 is 50 ohms, and therefore, the maximum S11 response at zero frequency is calculated to be -9.54dB. In addition, for these input values, the reflection coefficient response S11 and transfer function response S21 (of the designed cone) over the frequency range are as follows Figure 5A and Figure 5B as shown in .

[0063] Furthermore, in another example, a substrate material with a dielectric constant of 9.8, a substrate thickness of 100um, and a conductor thickness of 3um may be used in the example of DML TOSA design. Furthermore, aluminum oxide (Al2O3) or aluminum nitride (AIN) may be used in the submount design, and a tapered transmission line may be implemented to match different impedance values ​​between a driver IC impedance of 50 ohms and a DMLTOSA impedance of 25 ohms. In an example, the target of impedance matching between two different impedance values ​​may be at 10 GHz (F min ) and above, the reflection coefficient (S11) is -20dB. Figure 2E and Figure 3 as shown in .

[0064] In one aspect of the present disclosure, for the implementation of a tapered transmission line, a taper including a microstrip taper can be used for impedance matching, and the design geometry of the taper can be that the total length of the tapered transmission line can be 3.63 mm, including 21 step-length segmented taper sections, such as Figure 4 . In another embodiment, the cone may include a coplanar waveguide or a coplanar stripline. In an example, each segment of the tapered transmission line may have a different width dimension (in mm) but the same length (e.g., 173 um), and impedance value (in ohms). It should also be noted that while specific dimensions of a tapered transmission line or cone are used herein for purposes of clarity and illustration, the present disclosure of the technology is not limited thereto, and other dimensions in accordance with one or more aspects of the present disclosure may be used.

[0065] Return to reference Figure 3 and Figure 4 The cone design goal can be to make the maximum value of the reflection coefficient S11 response above 10GHz (F min ) is maintained at about -20dB. Therefore, it is noted that F min is 10 GHz, and the passband reflection is about -20 dB. Also, note that the reflection coefficient or S11 response below 10 GHz becomes larger as the frequency decreases toward zero frequency. Figure 3 As shown in , the maximum reflection coefficient S11 response at zero frequency is shown to be about -9.54dB, which is given by Figure 2E That is, in the example, the maximum reflection coefficient or S11 value at zero frequency can be determined by the following formula: 20*log((Z2-Z1) / (Z1+Z2)), where Z1 is 25 ohms and Z2 is 50 ohms, and in the example, the maximum S11 response at zero frequency is calculated to be -9.54 dB.

[0066] In addition, as mentioned above, for the example design, Figure 4 As shown in , the cone can be designed so that the total length of the desired tapered transmission line is determined to be 3.633 mm, with 21 steps, and with a step length of 0.173 mm. Figure 4 As seen in , the segments of the designed cone include different impedance values ​​and width values. That is, the characteristic impedance of the tapered transmission line can be modified by tapering the width of the transmission line, thereby creating a desired impedance cone by increasing or decreasing the width of the transmission line (microstrip line, stripline, etc.).

[0067] use Figure 3 and Figure 4 The design parameters shown in Figure 5A and Figure 5B The output simulation results of the example design of impedance matching between 25 ohms and 50 ohms shown in , show the reflection coefficient response S11 and transfer function response S21 (of the designed cone) over the frequency range.

[0068] Fig. 6A and Figure 6B The figure shows different F min In another aspect of the present disclosure, the present disclosure provides other example techniques or methods for impedance conversion (e.g., from 25 ohms to 10 ohms). As an example, with different F min Multiple designs of values ​​can be Fig. 6A and Figure 6B The implementation is shown in . Fig. 6A The diagram shows F min The first design for 10 GHz and a passband reflection of -30 dB resulted in a taper design with an output length of 5.84 mm and 21 steps. Figure 6B The figure shows a 5 GHz F min The second design with a passband reflection of -25 dB resulted in a cone design with 21 steps and an output length of 9.68 mm.

[0069] In one aspect of the present disclosure, for the purpose of illustration, in another example, a tapered impedance converter (e.g., 25 ohms to 10 ohms) for a DFB package may be implemented. In the case of a DFB TO, the impedance of the TO header is typically about 25 ohms, and the internal sub-mount may be designed with a 25 ohm transmission line, and a 10 ohm DFB chip may be mounted on top of the 25 ohm transmission line. Because the 10 ohm impedance is terminated at the end of the 25 ohm transmission line, a DFBTO design without the present technology may result in poor reflection coefficient S11 and transfer function S21 responses. However, by implementing a tapered transmission line according to one or more aspects of the present disclosure, the reflection coefficient and transfer function responses S11 and S21 may be significantly improved, respectively.

[0070] In another aspect of the present disclosure, in an example design of a taper for a 25 ohm TOSA package, certain input parameters may be used to design a 25 ohm to 10 ohm taper. As an example, Fig. 7A As shown in , the design conditions can be provided as follows: the substrate material is 99.8% alumina, the substrate thickness is 200um, the gold thickness is 2um, and the dielectric constant is 9.8, and the input parameters can be set as: Z1 = 10 ohms, Z2 = 25 ohms, F min =5GHz, and passband reflection = -20dB. For the above design conditions and input parameters, the desired output result with the designed tapered length of 7.65mm and 21 steps can be obtained, such as Fig. 7A and Figure 7B as shown in .

[0071] However, in the example, it is noted that the designed taper length of 7.65 mm may not be suitable for a submount for a DFB TO, because the typical length available in a TO56 for a DFB laser is typically about 1-2 mm, which is a much shorter length than the designed taper length. Therefore, the design conditions may need to be changed and the process may need to be repeated to obtain a more practical taper design length suitable for a TO56. However, it should also be noted that in another aspect of the present disclosure, the initial design length may be applicable and used for a different type of package, such as a box package with relatively large internal dimensions. Alternatively, a taper design with a smaller taper length may also be obtained by a relaxed design specification.

[0072] In another aspect of the present disclosure, the length of the designed cone can be controlled by using a thinner substrate thickness and a larger load impedance. As an example, in the example, the thickness of the substrate can be changed to 150um, and the load impedance Z1 can be changed to 13 ohms, resulting in a designed cone with a length of 6.61mm and 21 steps, which is Fig. 8A and Figure 8B Shown in.

[0073] However, note that even with a substrate thickness of 150 um, the designed length of the cone (eg, 6.61 mm) may still be larger than desired. Thus, the load impedance may be further modified based on trial and error until the desired result is obtained.

[0074] As described above, by utilizing the cone design, better impedance matching can be achieved in an optical device or equipment including a DML package, and the improved impedance matching helps improve the overall performance. Thus, even if there are some changes in source impedance, load impedance, printed wiring board (PWB) line impedance, TO / submount impedance, etc., the overall performance of the optical system, device or equipment may become very good.

[0075] In another aspect of the present disclosure, the impedance values ​​of the PWB and TO and sub-mounts can be fixed to specific values, respectively. Even if there are some changes in the PWB and TO and sub-mounts, the overall performance will not be greatly affected. In addition, the flexible circuit can be designed with a modified or simpler cone design, which may be easier to implement.

[0076] As described above, the cone can be designed and implemented to match different impedance values, for example, to address the impedance mismatch between 25 ohms and 10 ohms. In addition, using certain design requirements, the total length of the cone may be 19 mm, which may be too long to be implemented in a flexible circuit and DML TO, so multiple iterations of the cone design and modifications of the input parameters may be required. In addition, the designed cone may include multiple parts, such as three parts, which correspond to Fig. 9 As an example, the three parts of the cone may include (i) a first part or segment for the driver to the flexible joint on the printed circuit board (PCB), (ii) a second part or segment for the flex circuit, and (iii) a third part or segment for the TO and submount including the DML. In addition, since the impedance of the TO package is also part of the cone, the impedance of the TO package must be modified to obtain an accurate cone design.

[0077] Fig. 9 An example taper design in one aspect of the present disclosure is illustrated. In the example, the first portion of the designed taper corresponding to the PCB or PWB is 2.73 mm in length, the second portion of the designed taper corresponding to the flex circuit is 13.65 mm in length, and the third portion of the designed taper corresponding to the TO and submount is 2.73 mm in length. Thus, the designed taper length becomes a total taper length of 19.11 mm, which may be too long to be implemented in a flex circuit, so further design iterations may be required based on different input parameters.

[0078] In addition, as mentioned above, Fig. 9In the example shown, the designed cone may include three parts. That is, the designed cone includes a first part corresponding to the PWB, a second part corresponding to the flexible circuit, and a third part corresponding to the TO and the sub-mount. In the example, the length of the first part is 2.73 mm, and the first part includes three segments. The length of the second part is 13.6 mm and the second part includes fifteen segments. The length of the third part is 2.73 mm, and the third part includes three segments. In addition, in the example, each segment x has a width of X (in mm or inches) and an impedance value of Z0 (in ohms).

[0079] In addition, in the example, it is noted that the first and third parts of the cone are relatively short, and their impedances can be approximated as the average of the three segments included therein, respectively. In addition, for the flex circuit, the total length of the flex circuit can be 13.65 mm, which may be too long to fit, and thus may lead to further iterations of the cone length design. In addition, for the second part, the segments can be divided into 5 subgroups, and the average impedance of each subgroup can be used for the new impedance of each subgroup.

[0080] Fig. 10A , Fig. 10B and Fig. 10C Shows relative to Fig. 9 Simulation results for a modified cone design of . Note that in the accompanying figures and graphs, whenever applicable, the red trace is for the original cone design and the blue trace is for the modified cone design.

[0081] FIGS. 11 and 12 illustrate the optimization results of the modified cone design relative to the original cone design. In another aspect of the present disclosure, the modified cone design can be further optimized by changing the lengths of the different portions or segments. As an example, the length of the flex circuit can be reduced from 2.73 mm to 2 mm per segment. When the length of the flex circuit is reduced, as shown in FIGS. 11 and 12, the S33 (the response of the modified cone design) response deteriorates with increasing frequency, however, the S43 response (the response of the modified cone design) improves slightly at the expense of S33 degradation, as shown in the overlay graphs.

[0082] Fig.11A and Fig. 11B The graph shows the optimized results when the length of the flex circuit is reduced from 2.73 mm to 2 mm per section. Fig. 12A and Fig. 12B Another optimization result is shown when the length of the flexible circuit can be reduced from 2.73 mm to 1.5 mm per section. Fig. 12A and Fig. 12BAs shown in , while the S33 response gets worse with increasing frequency, the S43 response improves at the expense of the S33 response degradation. Note that when the length of each section is further reduced to 1.3 mm, S21 improves even more at high frequencies at the expense of S11 degradation.

[0083] Fig.13A and Fig. 13B Another optimization result of the modified cone design is shown. In one aspect of the present disclosure, the load impedance can be varied. As an example, the load impedance can be changed from 10 ohms to 15 ohms, and the length of the flex circuit is also reduced from 2.73 mm per segment to 2 mm.

[0084] Fig.14A and Fig. 14B Another optimization result of the modified cone design is shown. In one aspect of the present disclosure, the source impedance can be varied. As an example, the source impedance can be varied from 25 ohms + / - 10% (22.5 ohms to 27.5 ohms), and the length of the flex circuit is also reduced from 2.73 mm per section to 2 mm.

[0085] Fig.15A and Fig. 15B Another optimization result of the modified cone design is illustrated. In one aspect of the present disclosure, both the source impedance and the load impedance are varied. As an example, the source impedance is set to 22.5 ohms and the load impedance is set to 12 ohms. The length of the flex circuit can be reduced from 2.73 mm per segment to 2 mm.

[0086] Fig.16A and Fig. 16B Another optimization result of the modified cone design is shown. In one aspect of the present disclosure, the PWB line impedance is changed from 20.44 ohms to 25 ohms, and the length of the flexible circuit is also reduced from 2.73 mm per segment to 2 mm. In addition, it is noted that even if the line impedance of the PWB can be 25 ohms according to the usual design, the overall performance will not be greatly affected.

[0087] Fig.17A and Fig. 17B Another optimization result of the modified cone design is shown. In one aspect of the present disclosure, the impedance of the TO and submount can be changed from 12.22 ohms to 13.22 ohms. 13.22 ohms is the impedance of the last section of the flex circuit. The length of the flex circuit can be reduced from 2.73 mm to 2 mm per section. In the example, even if the impedance of the TO and submount is slightly increased to the same value as the impedance of the last section of the flex circuit, the overall performance is not greatly affected.

[0088] Fig.18A and Fig.18BAnother optimization result of the modified cone design is illustrated. In one aspect of the present disclosure, in the example, the impedance of the TO and submount can be set to 13.22 ohms. The PWB impedance can also be set to 25 ohms. The load impedance can also be changed from 10 ohms to 13 ohms. The length of the flex circuit can be reduced from 2.73 mm to 2 mm per segment. Note that the overall S21 performance is well maintained even though the impedance of the TO and submount is slightly increased and the PWB impedance is set to 25 ohms. Note also that the S43 and S33 responses show the best performance when the load impedance is 13 ohms. Further, note that in the example, the 10 ohm load shows the worst performance because the impedance of the TO plus submount is increased.

[0089] In various aspects of the present disclosure, in one example, better impedance matching of DML packages matched at 25 ohms has been demonstrated based on implementations of a taper design between components. Thus, even with some variations in source impedance, load impedance, and TO / submount impedance, the overall performance of an optical device or equipment employing a DML package and taper design has been shown to have significant improvements. It should also be noted that slightly lowering the source impedance and slightly increasing the load impedance may also result in better impedance matching.

[0090] In addition, in another aspect of the present disclosure, the cone can be designed and implemented to achieve higher performance from PWB to DML. In another aspect of the present disclosure, the PWB and TO and submount impedance can be fixed to one value, and even if there are some changes in the PWB and TO and submount, the overall performance will not be significantly affected. In addition, the flex can be designed with one or more modified cone designs, which makes it easier to implement.

[0091] Thus, the present disclosure provides a new novel cone design and its application for impedance matching between various components in optical devices or equipment. As an example, the different impedances of the DML and the DML driver in the TO package can be effectively matched, thereby improving the performance of the DML packaged in the TO and the overall performance of the optical communication device, system or equipment including the same.

[0092] In addition, therefore, embodiments of the present technology can bring many benefits, including better matching design, improved performance, lower driving voltage and less power consumption, reduced reflections, reduced RF radiation, etc.

[0093] As indicated above, various methods, techniques, arrangements, or variations thereof may be implemented to match different impedance values ​​using the design and implementation of tapered transmission lines in optical devices or equipment.Other embodiments of the present technology are also possible and are not limited to the embodiments disclosed herein.

[0094] In the present disclosure, if there is no obvious opposite meaning in the context, the singular form may include the plural form. In addition, as used herein, the article "one" is intended to include one or more items. In addition, unless clearly described in the present disclosure, any element, action, step or instruction used in the present disclosure should not be interpreted as being essential or indispensable to the present disclosure. As used herein, unless otherwise clearly stated, the term "comprise" and the variant of the term, such as "comprising", "comprises" and "comprised" are not intended to exclude other additions, parts, integers or steps. The terms "first", "second" and the like used herein can be used to describe various parts, but the parts are not limited by the above terms. The above terms are only used to distinguish a part from other parts without departing from the scope of the present disclosure. In addition, as used herein, the term "and / or" includes a combination of multiple associated items or any item in multiple associated items. In addition, it is noted that when describing an element "coupled" or "connected" to another element, the element can be directly coupled or directly connected to another element, or the element can be coupled or connected to another element by a third element. In addition, the terms "including" or "having" as used herein indicate the presence of the features, operations, components, steps, quantities, parts, or any combination thereof described herein. In addition, the terms "including" or "having" do not exclude the possibility of the presence or addition of one or more other features, operations, components, steps, quantities, parts, or combinations. In addition, the article "a" as used herein is intended to include one or more items. In addition, unless explicitly stated in the present disclosure, any element, action, step, or instruction used in the present disclosure should not be interpreted as essential or indispensable to the present disclosure.

[0095] Although the present technology has been illustrated with the specific examples described herein for the purpose of describing example embodiments, it will be appreciated by those skilled in the relevant art that a variety of alternative and / or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. Thus, the present disclosure is intended to cover any changes or variations of the examples and / or embodiments shown and described herein without departing from the spirit and technical scope of the present disclosure.

Claims

1. An optical communication device, comprising: Directly modulated laser DML in a package, a DML driver integrated circuit IC coupled to the DML, and The cone is set between the DML driver IC and the DML, wherein the cone is configured to match different impedance values ​​of the DML driver IC and the DML disposed within the package, minimizing an impedance mismatch between a first impedance value of the DML and a second impedance value of the DML driver IC, The cone is configured to include a first part, a second part and a third part, and wherein the first part of the cone is assigned to a driver of a flexible joint on a printed circuit board PCB, the second part of the cone is assigned to a flexible circuit, and the third part of the cone is assigned to a package, the package including a transistor outline TO, a ceramic box, a board-mounted optical device combination COBO or a chip-on-board COB package. 2 . The optical communication device according to claim 1 , wherein an impedance of the DML is 10 ohms, and an impedance of the DML driver IC is 25 ohms.

3. The optical communication device according to claim 1, Wherein the package is a transistor outline TO, And the third part of the cone is allocated to the TO and the submount.

4. The optical communication device of claim 3, wherein the first portion of the cone comprises a first set of three segments, the second portion of the cone comprises a second set of fifteen segments, and the third portion of the cone comprises a third set of three segments.

5. The optical communication device of claim 4, wherein the impedance of the first portion is an average value of three sections of the first portion, and the impedance of the third portion is an average value of three sections of the third portion.

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