Anti-crosstalk differential EML chip structure

Abstract

The invention discloses an anti-crosstalk differential EML chip structure, which comprises a PCB (Printed Circuit Board), a carrier plate, a DSP (Digital Signal Processor) chip arranged on the PCB, and an EML chip arranged on the carrier plate, an electro-absorption modulator, a load resistor Rm1 and a load resistor Rm2 are installed on the EML chip, differential wiring is carried out on the PCB and the carrier plate, and when a differential signal advances to the EML chip, one end of the differential signal is used for driving the electro-absorption modulator and an on-chip accessory circuit including the load resistor Rm1, and the other end of the differential signal is used for driving the load resistor Rm2. According to the invention, while a mainstream optical module design is compatible, the channel crosstalk problem in the optical module is effectively reduced, the anti-interference capability is improved, and the signal integrity of a channel is improved.

Description

Technical Field

[0001] The invention relates to the technical field of lasers, and in particular to a differential EML chip structure with crosstalk resistance. Background Art

[0002] With the rapid development of AI technology, especially the widespread application of generative AI tools such as ChatGPT, the demand for computing power networks has exploded. As an important foundation and solid base for computing power networks, the demand for optical communication networks has also surged. The implementation of emerging technologies such as cloud computing, big data, artificial intelligence, and virtual reality has led to an exponential growth in data traffic. As a key component for data transmission, the market demand for optical modules has also increased significantly, especially for 800G and 1.6T optical modules. High-speed optical modules can meet the market's demand for high speed, high density, low power consumption, and excellent reliability, and are therefore very popular.

[0003] As core components of high-speed optical communications, 800G and 1.6T optical modules face many technical challenges, among which crosstalk is particularly critical. Crosstalk refers to the phenomenon of signal interference between channels caused by electromagnetic coupling between different signal lines in an optical module. This interference will reduce signal quality, increase bit error rate, and affect the performance and stability of the entire optical communication system.

[0004] Specifically, the optical module contains complex circuits and signal channels. These channels will generate electromagnetic waves during high-speed transmission. If the electromagnetic shielding is not in place, it will interfere with other channels. This electromagnetic interference will become more serious as the signal frequency increases and the channel spacing decreases. Taking the 800G optical module as an example, Figure 1 As shown in the figure, for the 8×100G 800G optical module, there are 8 transmission channels between the DSP and the optical chip. Due to the small spacing between the channels, crosstalk is very likely to occur, resulting in the degradation of the quality of the transmitted signal eye diagram. For the 4×200G 800G optical module, although the number of transmission channels between the DSP and the optical chip has become 4, the rate has doubled, and the corresponding signal frequency has also doubled. At such a high frequency, the antenna radiation effect caused by the increase in electrical size is very obvious, the spatial radiation increases, and crosstalk is more likely to occur. Summary of the invention

[0005] The purpose of the present invention is to provide a differential EML chip structure with crosstalk resistance to solve the signal crosstalk problem in a high-speed optical module and improve the signal transmission quality.

[0006] To achieve the above objectives, the following technical solutions are adopted:

[0007] A crosstalk-resistant differential EML chip structure comprises a PCB board, a carrier board, a DSP chip mounted on the PCB board, and an EML chip mounted on the carrier board; an electro-absorption modulator, a load resistor Rm1 and a load resistor Rm2 are mounted on the EML chip, differential routing is performed on both the PCB board and the carrier board, and when a differential signal travels to the EML chip, one end of the differential signal is used to drive the electro-absorption modulator and its on-chip auxiliary circuits including the load resistor Rm1, and the other end of the differential signal is used to drive the load resistor Rm2.

[0008] Furthermore, the resistance of the load resistor Rm2 matches the equivalent impedance of the electro-absorption modulator and its auxiliary circuits.

[0009] Furthermore, the resistance value of the load resistor Rm2 ranges from 20 to 60 ohms.

[0010] By adopting the above scheme, the beneficial effects of the present invention are:

[0011] The present invention innovatively designs a differential EML chip, which can effectively reduce the channel crosstalk problem inside the optical module, improve the anti-interference ability, and enhance the signal integrity of the channel while being compatible with the mainstream optical module design. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the structure of an existing 800G optical module;

[0013] Figure 2 It is a schematic diagram of the structure of an existing EML chip driven by a single-ended signal;

[0014] Figure 3 A brief design diagram of the existing EML chip circuit driven by a single-ended signal;

[0015] Figure 4 It is a structural schematic diagram of the present invention;

[0016] Figure 5 It is a partial enlarged schematic diagram of the present invention;

[0017] Figure 6 A brief circuit design diagram of the present invention;

[0018] Figure 7 Comparison chart of real-time waveforms of EML chip simulation driven by single-ended signal and differential signal;

[0019] Figure 8 This is a comparison chart of the difference in far-end crosstalk between single-ended signals and differential signals with the same line width, line spacing and gap;

[0020] Fig. 9This is a comparison chart of the near-end crosstalk differences between single-ended signals and differential signals with the same line width, line spacing and gap.

[0021] The accompanying drawings illustrate:

[0022] 1. PCB board; 2. Carrier board; 3. DSP chip; 4. EML chip; 41. Electro-absorption modulator. DETAILED DESCRIPTION

[0023] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] Reference Figures 1 to 9 As shown, the present invention provides a differential EML chip structure with crosstalk resistance, including a PCB board 1, a carrier board 2, a DSP chip 3 installed on the PCB board 1, and an EML chip 4 installed on the carrier board 2; an electro-absorption modulator 41, a load resistor Rm1 and a load resistor Rm2 are installed on the EML chip 4, differential routing is performed on both the PCB board 1 and the carrier board 2, and when the differential signal travels to the EML chip 4, one end of the differential signal is used to drive the electro-absorption modulator 41 and its on-chip auxiliary circuits including the load resistor Rm1, and the other end of the differential signal is used to drive the load resistor Rm2.

[0025] Traditional EML chip 4 design is usually driven by a single-ended signal. Figure 2 The wiring from the output of the DSP chip 3 to the front end of the EAM (electroabsorption modulator 41) is a single-ended design. Although the structure is simple, crosstalk is very likely to occur in a high-speed optical module. The circuit schematic diagram is shown in FIG. Figure 3 As shown; In order to reduce the crosstalk inside the high-speed optical module, the present invention creatively proposes a differential EML chip 4 circuit design, such as Figure 4-5 As shown, the EML chip 4 is driven by a differential signal. Differential routing is performed on both the optical module PCB board 1 and the carrier (carrier board 2). When the differential signal travels to the EML chip 4, one end of the differential signal drives the EAM and its on-chip auxiliary circuits including the load resistor Rm1, and the other end drives the load resistor Rm2. The specific circuit schematic diagram is shown in FIG. Figure 6 As shown; wherein, the resistance of the on-chip load resistor Rm2 needs to match the equivalent impedance of the EAM and its associated circuits so as to suppress the common-mode noise of the differential drive, especially the common-mode noise in the frequency band above 30 GHz.

[0026] In a preferred embodiment, the resistance range of the load resistor Rm2 is between 20 and 60 ohms; Figures 8 to 9As shown in the figure, the differences in far-end crosstalk and near-end crosstalk of single-ended signals and differential signals with the same line width and line spacing and the same gap are compared. Under the same driving signal swing, the crosstalk of the differential driving signal is nearly 20dB lower than that of the single-ended signal.

[0027] In summary, in the present invention, the differential signal is transmitted through two signal lines, one of which transmits the original signal and the other transmits a signal with a phase opposite to the original signal. When the two signal lines are interfered, the interference signals will cancel each other out on the two lines, thereby improving the accuracy of the signal and improving the anti-crosstalk capability. Please refer to Figure 7 By simulating the real-time waveform, we can see that there are serious interference signals on the individual traces. However, when the signals are subtracted at the EAM, the differential signal obtained is still relatively clean, which significantly improves the signal-to-noise ratio and thus improves the channel transmission quality.

[0028] Therefore, the differential signal driving design of the present invention has significant anti-interference capability in high-speed optical modules. Compared with single-ended signal driving, differential signal driving can reduce far-end crosstalk and near-end crosstalk, thereby improving signal integrity and reducing bit error rate.

[0029] The above are only preferred embodiments of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A differential EML chip structure with crosstalk resistance, comprising a PCB board, a carrier board, a DSP chip mounted on the PCB board, and an EML chip mounted on the carrier board; an electro-absorption modulator, a load resistor Rm1 and a load resistor Rm2 are mounted on the EML chip, characterized in that: Differential routing is performed on both the PCB board and the carrier board, and when the differential signal travels to the EML chip, one end of the differential signal is used to drive the electro-absorption modulator and its on-chip auxiliary circuits including the load resistor Rm1, and the other end of the differential signal is used to drive the load resistor Rm2.

2. The crosstalk-resistant differential EML chip structure according to claim 1, characterized in that: The resistance value of the load resistor Rm2 matches the equivalent impedance of the electro-absorption modulator and its auxiliary circuits.

3. The crosstalk-resistant differential EML chip structure according to claim 2, characterized in that: The resistance value of the load resistor Rm2 ranges from 20 to 60 ohms.

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