Optical receiving module, optical transmitting module and optical transceiving module

Abstract

Disclosed in the present application are an optical receiving module, an optical transmitting module and an optical transceiving module, which are used for reducing loss, increasing gain and reducing noise. In the optical receiving module, impedance matching is performed by means of a first stepped-impedance transformation planar transmission line or a first lumped-element network, where impedance matching may be achieved not by using resistors, but by using capacitors and inductors, such that the loss of a radio-frequency signal during transmission can be reduced, thereby increasing gain and reducing noise. In the optical transmitting module, impedance matching is performed by means of a second stepped-impedance transformation planar transmission line or a second lumped-element network, where impedance matching may be achieved not by using resistors, but by using capacitors and inductors, such that the loss of a radio-frequency signal during transmission can be reduced, thereby increasing gain and reducing noise.

Description

A receiving optical module, a transmitting optical module and a transceiving optical module

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application No. 202410978889.4, filed on July 19, 2024, entitled “A receiving optical module, a transmitting optical module and a transceiving optical module”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of optical fiber communication technology, in particular to a receiving optical module, a transmitting optical module and a transceiving optical module. BACKGROUND

[0004] Compared with the traditional radio frequency transmission link, the radio over fiber (RoF) transmission link has the advantages of large bandwidth, small loss, light weight and anti-electromagnetic interference, and can be applied to large bandwidth application scenarios of wireless communication systems. The characteristics of the RoF link are that the conversion of the radio frequency signal and the optical signal is completed through the electro-optical conversion of the transmitting optical module first, then the remote transmission is completed through the optical fiber, and finally the conversion of the optical signal and the radio frequency signal is completed through the photoelectric conversion of the receiving optical module to output the radio frequency signal, so as to replace the microwave assembly or the cable transmission of the radio frequency signal. According to the modulation type, the RoF transmission link can be divided into: direct modulation type (i.e. the transmitting optical module adopts a direct modulation laser scheme), external modulation type (i.e. the transmitting optical module adopts a combination scheme of a laser and an electro-optical modulator). In the direct modulation type RoF transmission link, the direct modulation laser in the transmitting optical module realizes the electro-optical conversion function, and the photodetector (PD) in the receiving optical module realizes the photoelectric conversion function.

[0005] At present, in the transmitting optical module, since the internal resistance of the direct modulation laser is generally 5-10 ohms, a 40-45 ohm resistor is usually connected in series between the direct modulation laser and the radio frequency transmission circuit connected thereto for impedance matching. However, in actual application, a large part of the power of the radio frequency signal transmitted by the radio frequency transmission circuit is consumed by the 40-45 ohm resistor connected in series, resulting in that the power of the radio frequency signal transmitted to the direct modulation laser is small, and the electro-optical modulation efficiency of the direct modulation laser is reduced.

[0006] And, in the receiving optical module, since the internal resistance of the photodetector is usually as high as several thousand ohms, a 50-ohm resistor is usually connected in parallel between the photodetector and the radio frequency transmission circuit connected thereto for impedance matching. However, in actual applications, the 50-ohm resistor connected in parallel will take away a part of the output photocurrent, resulting in a matching loss of 6dB in the power of the transmitted radio frequency signal. Therefore, in the RoF transmission link, the current resistance matching scheme of the transmitting optical module and the receiving optical module is all lossy matching, resulting in a low gain and a poor noise figure of the RoF link, which greatly limits the application range of the RoF technology. SUMMARY

[0007] Embodiments of the present application provide a receiving optical module, a transmitting optical module and a transceiving optical module to reduce loss, improve gain and reduce noise.

[0008] In a first aspect, embodiments of the present application provide a receiving optical module, which includes a photodetector and a first stepped transformation planar transmission line. The first stepped transformation planar transmission line includes sequentially connected 1st to Mth transmission line subsegments. The 1st transmission line subsegment is connected to a signal output port of the photodetector, and the Mth transmission line subsegment is used to connect a radio frequency input end of a radio frequency transmission circuit, so as to realize impedance matching through the first stepped transformation planar transmission line. In embodiments of the present application, based on the actually measured direct current, scattering parameter data under different input optical powers, different bias voltages and different frequencies, a photodetector circuit model related to the input optical power, the bias voltage and the frequency is established to accurately represent the photoelectric conversion process of the photodetector. Then, the established photodetector circuit model is used to perform simulation based on the requirements of matching a large bandwidth (for example, 10GHz-13GHz) and a transmission coefficient greater than or equal to 0.9, to obtain the first stepped transformation planar transmission line meeting the above requirements. That is, the first stepped transformation planar transmission line needs to be segmented, and the impedances of adjacent segments need to be designed to be different. Based on this, the first stepped transformation planar transmission line is designed to realize impedance matching, which can minimize the loss of the radio frequency signal in the output process, effectively reduce the loss of the radio frequency signal in the output process compared with using a resistor for impedance matching, thereby improving the gain and reducing the noise figure of the entire RoF network system, and further a high-performance RoF transmission link can be obtained.

[0009] M can be an integer and M≥3, i.e., the first stepped transformation planar transmission line is divided into at least three sections. In order to match the impedance, and meet the requirements of matching a large bandwidth (e.g., 10 GHz-13 GHz) and a transmission coefficient greater than or equal to 0.9, the impedance of at least one of the second transmission line section to the M-1th transmission line section can be less than the impedance of the first transmission line section. Through simulation, it is found that if the impedance of the first transmission line section to the Mth transmission line section is set to increase in an increasing trend from small to large, impedance matching can also be achieved, but the bandwidth is usually less than 0.5 GHz when the impedance matching is performed using this impedance variation trend, resulting in a narrow matching bandwidth and a greatly limited application range.

[0010] In some embodiments, M≥4, i.e., the first stepped transformation planar transmission line is divided into at least four sections, and the impedance variation law of the first transmission line section to the Mth transmission line section is adjusted, e.g., the impedance of each of the first transmission line section to the Mth transmission line section can be sequentially reduced, increased, and then reduced again, so as to further improve the transmission coefficient on the basis of matching a large bandwidth.

[0011] In some embodiments, since the first transmission line section is connected to the signal output port of the photodetector, and the Mth transmission line section is connected to the corresponding radio frequency transmission circuit, in order to compensate for the impedance of the first transmission line section and the Mth transmission line section, the impedance of the first transmission line section to the Mth transmission line section can be first reduced and then increased to be greater than the impedance of the Mth transmission line section, and finally reduced to the impedance of the Mth transmission line section. Exemplarily, the impedance of the first transmission line section to the ath transmission line section connected in sequence can be first gradually reduced, and then the impedance of the ath transmission line section to the bth transmission line section connected in sequence can be first gradually increased and increased to be greater than the impedance of the Mth transmission line section. Then, the impedance of the bth transmission line section to the Mth transmission line section connected in sequence is gradually reduced.

[0012] In some embodiments, in order to obtain a larger transmission coefficient at certain frequency points (e.g., 2.4 GHz, 5 GHz), the impedance of the second transmission line section can be less than the impedance of the first transmission line section and the impedance of the third transmission line section, or the impedance of the third transmission line section can be less than the impedance of the second transmission line section and the impedance of the fourth transmission line section, and the impedance of the second transmission line section can be less than the impedance of the first transmission line section. By setting in this way, the inflection point of the impedance reduction can be set at the impedance of the second transmission line section or the impedance of the third transmission line section, and the transmission coefficient at certain frequency points can be further improved.

[0013] In some embodiments, in order to obtain a larger transmission coefficient at certain frequency points (for example, 2.4 GHz, 5 GHz), the impedance of the M-1th transmission line subsection can be greater than the impedance of the Mth transmission line subsection and the impedance of the M-2th transmission line subsection, or the impedance of the M-2th transmission line subsection can be greater than the impedance of the M-1th transmission line subsection and the impedance of the M-3th transmission line subsection, and the impedance of the M-1th transmission line subsection is greater than the impedance of the Mth transmission line subsection. By setting in this way, the inflection point of the impedance rise can be set at the impedance of the M-1th transmission line subsection or the impedance of the M-2th transmission line subsection, which can further improve the transmission coefficient at certain frequency points.

[0014] For the specific number of transmission line subsections, a suitable value can be selected by those skilled in the art based on the needs of impedance matching, large bandwidth, high transmission coefficient, low noise and other performances, as well as considerations such as the size and cost of the receiving optical module 200. For example, the specific number of transmission line subsections can be set to 3-20. In actual application, if the number of transmission line subsections is too small, the impedance variation trend of the transmission line subsections will not be effective. If the number of transmission line subsections is too large, the size will be too large, the loss will increase, and the design and processing difficulty will increase, resulting in increased cost. Therefore, considering the influence of cost and performance, in the embodiments of the present application, 4≤M≤10 is set to balance the influence of cost and performance. For example, M can be 4, 6, 8, 9, 10, etc., which is not limited here.

[0015] On the basis of matching a large bandwidth, in order to further improve the transmission coefficient, the difference between the impedance of the 1st transmission line subsection and the output impedance of the signal output port of the photodetector can be close to zero or equal to zero, and the difference between the impedance of the Mth transmission line subsection and the input impedance of the radio frequency input end of the corresponding radio frequency transmission circuit can be close to zero or equal to zero.

[0016] In some embodiments, the first stepped transformation plane transmission line can include but is not limited to a stepped transformation microstrip line or a stepped transformation stripline. For example, when the first stepped transformation plane transmission line is set as a stepped transformation microstrip line, the stepped transformation microstrip line is divided into the 1st transmission line subsection to the Mth transmission line subsection. When the first stepped transformation plane transmission line is set as a stepped transformation stripline, the stepped transformation stripline is divided into the 1st transmission line subsection to the Mth transmission line subsection.

[0017] In some embodiments, the receiving optical module further comprises a first receiving component, a first end of the first receiving component is connected with one of the first transmission line sub-section and the Mth transmission line sub-section, and a second end of the first receiving component is configured to be connected with the power supply input port or the ground input port. The first receiving component is configured to couple a signal of the power supply input port or the ground input port to the transmission line sub-section connected therewith and block the radio frequency signal. In this way, a direct current voltage or a ground voltage can be input through the first receiving component, and the radio frequency signal leakage can be blocked or reduced.

[0018] In some embodiments, in order to reduce the influence of the first receiving component on the impedance and the radio frequency signal leakage of each transmission line sub-section in the first stepped transition plane transmission line, the first end of the first receiving component can be connected to a connection between the first transmission line sub-section and the second transmission line sub-section.

[0019] In some embodiments, the first receiving component can comprise a first quarter wavelength transmission line or a first receiving inductor, so that a simple device can be used to both transmit a voltage and block the radio frequency signal.

[0020] In some embodiments, when the second end of the first receiving component is configured to be connected with the power supply input port, the receiving optical module further comprises a first receiving ground capacitor and a second receiving component, wherein a first electrode of the first receiving ground capacitor is connected with the first ground port of the photodetector, a second electrode of the first receiving ground capacitor is configured to be connected with the power supply input port, a first end of the second receiving component is connected with the first ground port of the photodetector, and a second end of the second receiving component is configured to be connected with the power supply input port. The second receiving component and the first receiving ground capacitor are respectively configured to couple a signal of the power supply input port to the first ground port of the photodetector, and the second receiving component is further configured to block the radio frequency signal. In this way, the second receiving component and the first receiving ground capacitor can be grounded, and the radio frequency signal leakage can be blocked or reduced.

[0021] In some embodiments, the second receiving component comprises a second quarter wavelength transmission line or a second receiving inductor, so that a simple device can be used to both transmit a voltage and block or reduce the amount of radio frequency signal.

[0022] In some embodiments, when the second end of the first receiving component is configured to be connected with the power supply input port, the receiving optical module further comprises a second receiving ground capacitor, wherein a first electrode of the second receiving ground capacitor is connected with the first ground port of the photodetector, and a second electrode of the second receiving ground capacitor is configured to be connected with the power supply input port. In this way, a simple device can be used to both transmit a voltage and block or reduce the amount of radio frequency signal.

[0023] In some embodiments, the receiving optical module further comprises a third receiving ground capacitor, a first electrode of the third receiving ground capacitor is connected with the second ground port of the photodetector, and a second electrode of the third receiving ground capacitor is used to connect the ground input port. In this way, the transmission voltage and the blocking or reducing of the RF signal passing amount can be realized by using simple devices.

[0024] In a second aspect, the embodiments of the present application provide another receiving optical module. The receiving optical module comprises a photodetector and a first lumped element network. A first end of the first lumped element network is connected with a signal output port of the photodetector, and a second end of the first lumped element network is used to connect a RF input end of a RF transmission circuit to realize impedance matching through the first lumped element network. In order to reduce the loss, the first lumped element network comprises a plurality of receiving matching capacitors and a plurality of receiving matching inductors. The plurality of receiving matching inductors are connected in series between the signal output port of the photodetector and the RF input end of the RF transmission circuit. The two ends of at least part of the receiving matching inductors are respectively connected with the first end of one receiving matching capacitor. The second end of the plurality of receiving matching capacitors is used to connect a ground input port. In this way, the impedance matching can be realized by using capacitors and inductors instead of resistors, and the loss in the process of RF signal transmission can be reduced.

[0025] In addition, in some embodiments of the present application, the photodetector circuit model related to the input optical power, the bias voltage and the frequency can be established based on the actually measured DC, scattering parameter data under different input optical powers, different bias voltages and different frequencies, so as to accurately characterize the photoelectric conversion process of the photodetector. Then, the established photodetector circuit model is used to simulate to obtain the number of capacitors and inductors, and the change rule of the capacitance value of the capacitor and the inductance value of the inductor, which meet the requirements of matching a large bandwidth (for example, 10GHz-13GHz) and the transmission coefficient being greater than or equal to 0.9. In the direction from the signal output port of the photodetector to the RF input end of the RF transmission circuit, the inductance values of the plurality of receiving matching inductors show a decreasing trend, and the capacitance values of the plurality of receiving matching capacitors show a decreasing trend. Based on this, the capacitors and inductors in the first lumped element network are designed to realize impedance matching, which can minimize the loss of the RF signal in the output process. Compared with using resistors to realize impedance matching, the loss of the RF signal in the output process can be effectively reduced, so as to improve the gain of the entire RoF network system, reduce the noise coefficient, and thus a high-performance RoF transmission link can be obtained.

[0026] In some embodiments, the plurality of receiving matching inductances comprises a first receiving matching inductance and a second receiving matching inductance, and the plurality of receiving matching capacitances comprises a first receiving matching capacitance, a second receiving matching capacitance, and a third receiving matching capacitance, wherein a first end of the first receiving matching inductance, a first end of the first receiving matching capacitance, and a first end of the first lumped element network are connected to each other, a second end of the first receiving matching inductance, a first end of the second receiving matching inductance, and a first end of the second receiving matching capacitance are connected to each other, a second end of the second receiving matching inductance, a first end of the third receiving matching capacitance, and a second end of the first lumped element network are connected to each other, and a second end of the first receiving matching capacitance, a second end of the second receiving matching capacitance, and a second end of the third receiving matching capacitance are connected to the ground input port. In this way, the first lumped element network can be implemented by using a simple structure to achieve impedance matching.

[0027] In some embodiments, the receiving optical module further comprises a third receiving inductance, a first end of the third receiving inductance is connected to the signal output port of the photodetector, and a second end of the third receiving inductance is connected to the power supply input port. In this way, a simple device can be used to not only transmit voltage but also block radio frequency signals.

[0028] In some embodiments, the receiving optical module further comprises a fourth receiving ground capacitance, a first electrode of the fourth receiving ground capacitance is connected to the first ground port of the photodetector, and a second electrode of the fourth receiving ground capacitance is connected to the ground input port. In this way, a simple device can be used to not only transmit voltage but also block or reduce the amount of radio frequency signals.

[0029] In some embodiments, the receiving optical module further comprises a fifth receiving ground capacitance, a first electrode of the fifth receiving ground capacitance is connected to the second ground port of the photodetector, and a second electrode of the fifth receiving ground capacitance is connected to the ground input port. In this way, a simple device can be used to not only transmit voltage but also block or reduce the amount of radio frequency signals.

[0030] In a third aspect, the embodiments of the present application provide a transmitting optical module, which comprises a direct modulation laser and a second stepped transformation planar transmission line, the second stepped transformation planar transmission line comprises a first transmission line subsegment to an Nth transmission line subsegment connected in sequence, the first transmission line subsegment is connected to a radio frequency output end of a radio frequency transmission circuit, and the Nth transmission line subsegment is connected to a signal input port of the direct modulation laser to achieve impedance matching through the second stepped transformation planar transmission line.

[0031] In the present application, based on the DC current (I)-voltage (V) data, scattering parameter data and output different optical power under different bias voltage and different frequency actually measured, the direct modulation laser circuit model related to bias voltage, frequency and output optical power can be established to accurately characterize the electro-optical conversion process of the direct modulation laser. Then, the established laser circuit model is used, and based on the requirements of matching a large bandwidth (for example, 2GHz-6GHz) and a transmission coefficient greater than or equal to 0.9, simulation is performed to obtain a second ladder transformation planar transmission line meeting the above requirements. That is, the second ladder transformation planar transmission line needs to be segmented, and the impedance of adjacent segments needs to be designed to be different. Based on this, the second ladder transformation planar transmission line is designed to realize impedance matching, which can minimize the loss of the radio frequency signal in the output process. Compared with using resistance for impedance matching, the loss of the radio frequency signal in the output process can be effectively reduced, thereby improving the gain of the entire RoF network system, reducing the noise coefficient, and further obtaining a high-performance RoF transmission link.

[0032] In addition, N can be an integer and N≥3, that is, the second ladder transformation planar transmission line is divided into at least 3 segments. In order to perform impedance matching and meet the requirements of matching a large bandwidth (for example, 2GHz-6GHz) and a transmission coefficient greater than or equal to 0.9, the impedance of at least one of the second transmission line subsection to the N-1 transmission line subsection can be less than the impedance of the N transmission line subsection.

[0033] In some embodiments, N≥5, that is, the second ladder transformation planar transmission line is divided into at least 5 segments, and the impedance variation law of the first transmission line subsection to the N transmission line subsection is adjusted. For example, the impedance of each of the first transmission line subsection to the N transmission line subsection can be sequentially increased, decreased, increased, and decreased, so as to further improve the transmission coefficient on the basis of matching a large bandwidth.

[0034] In some embodiments, since the first transmission line sub-section connects the corresponding radio frequency transmission circuit, and the Nth transmission line sub-section connects the direct modulation laser, in order to compensate the impedance of the first transmission line sub-section and the Nth transmission line sub-section, the impedance of the first transmission line sub-section to the Nth transmission line sub-section can be sequentially increased first, then sequentially decreased to be less than the impedance of the Nth transmission line sub-section, then sequentially increased to be greater than the impedance of the Nth transmission line sub-section, and finally sequentially decreased to the impedance of the Nth transmission line sub-section. For example, the impedance of the sequentially connected first transmission line sub-section to the cth transmission line sub-section is gradually increased. And since the Nth transmission line sub-section connects the direct modulation laser, in order to compensate the impedance of the Nth transmission line sub-section, the impedance of the sequentially connected cth transmission line sub-section to the dth transmission line sub-section can be decreased first, and the impedance of the dth transmission line sub-section is decreased to be less than the input impedance of the direct modulation laser. Then, the impedance of the sequentially connected dth transmission line sub-section to the eth transmission line sub-section is gradually increased, and the impedance of the eth transmission line sub-section is increased to be greater than the input impedance of the direct modulation laser. Then, the impedance of the sequentially connected eth transmission line sub-section to the Nth transmission line sub-section is gradually decreased.

[0035] In some embodiments, in order to obtain a larger transmission coefficient at certain frequency points (such as 2.4 GHz, 5 GHz), the impedance of the second transmission line sub-section can be greater than the impedance of the first transmission line sub-section and the impedance of the third transmission line sub-section, or the impedance of the third transmission line sub-section can be greater than the impedance of the second transmission line sub-section and the impedance of the fourth transmission line sub-section, and the impedance of the second transmission line sub-section is greater than the impedance of the first transmission line sub-section. By setting in this way, the inflection point of the first increase in impedance can be set at the impedance of the second transmission line sub-section or the impedance of the third transmission line sub-section, and the transmission coefficient at certain frequency points can be further improved.

[0036] In some embodiments, in order to obtain a larger transmission coefficient at certain frequency points (such as 2.4 GHz, 5 GHz), the impedance of the N-1th transmission line sub-section can be greater than the impedance of the Nth transmission line sub-section and the impedance of the N-2th transmission line sub-section, the impedance of the N-2th transmission line sub-section can be less than the impedance of the Nth transmission line sub-section and the impedance of the N-3th transmission line sub-section, or the impedance of the N-2th transmission line sub-section can be greater than the impedance of the N-1th transmission line sub-section and the impedance of the N-3th transmission line sub-section, the impedance of the N-1th transmission line sub-section can be greater than the impedance of the Nth transmission line sub-section, and the impedance of the N-3th transmission line sub-section can be less than the impedance of the Nth transmission line sub-section and the impedance of the N-4th transmission line sub-section. By setting in this way, the inflection point of the second increase in impedance can be set at the impedance of the N-1th transmission line sub-section or the impedance of the N-2th transmission line sub-section, and the transmission coefficient at certain frequency points can be further improved.

[0037] In some embodiments, for the specific number of transmission line sub-sections, the skilled in the art can select appropriate values based on the needs of performance such as impedance matching, large bandwidth, high transmission coefficient and low noise, and considerations such as the size and cost of the transmitting optical module. For example, the specific number of transmission line sub-sections can be set to 3-20. In practical applications, if the number of transmission line sub-sections is too small, the impedance variation trend of the transmission line sub-sections will not be effective. If the number of transmission line sub-sections is too large, the size will be too large, the loss will increase, and the design and processing difficulty will increase, resulting in increased cost. Therefore, by considering the influence of cost and performance, in the embodiments of the present application, 5≤N≤10 is set to balance the influence of cost and performance. For example, N can be 5, 6, 8, 9, 10, etc., which is not limited herein.

[0038] In some embodiments, on the basis of matching a large bandwidth, in order to further improve the transmission coefficient, the difference between the impedance of the first transmission line sub-section and the output impedance of the radio frequency output end of the radio frequency transmission circuit connected thereto can be close to zero or equal to zero, and the difference between the impedance of the Nth transmission line sub-section and the input impedance of the signal input port of the direct modulation laser can be close to zero or equal to zero.

[0039] In some embodiments, the second stepped transformation planar transmission line includes, but is not limited to, a stepped transformation microstrip line or a stepped transformation stripline. For example, when the second stepped transformation planar transmission line is set as a stepped transformation microstrip line, the stepped transformation microstrip line is divided into the first transmission line sub-section to the Nth transmission line sub-section. When the second stepped transformation planar transmission line is set as a stepped transformation stripline, the stepped transformation stripline is divided into the first transmission line sub-section to the Nth transmission line sub-section.

[0040] In some embodiments, the transmitting optical module further includes a first transmitting component, a first end of the first transmitting component is connected to one of the first transmission line sub-section to the Nth transmission line sub-section, and a second end of the first transmitting component is used to connect the power supply input port. And the second receiving component is used to couple the signal of the power supply input port to the transmission line sub-section connected thereto and block the radio frequency signal. In this way, the second receiving component can be used to input direct current voltage and block or reduce radio frequency signal leakage.

[0041] In some embodiments, in order to reduce the influence of the first transmitting component on the impedance and radio frequency signal leakage of each transmission line sub-section in the second stepped transformation planar transmission line, the first end of the first transmitting component can be connected to the connection between the first transmission line sub-section and the second transmission line sub-section.

[0042] In some embodiments, the first transmitting component includes a third quarter wavelength transmission line or a first transmitting inductor, so that simple devices can be used to not only transmit voltage but also block or reduce the amount of radio frequency signal passing through.

[0043] In some embodiments, the transmitting optical module further comprises a first transmitting ground capacitor, a first electrode of the first transmitting ground capacitor is connected with the ground port of the direct modulation laser, and a second end of the first transmitting ground capacitor is used to connect the ground input port, so that a simple device can be used to realize both transmission of voltage and blocking or reducing of RF signal transmission.

[0044] In some embodiments, the transmitting optical module further comprises a second transmitting ground capacitor, a first electrode of the second transmitting ground capacitor is connected with the signal input port of the direct modulation laser, and a second end of the second transmitting ground capacitor is used to connect the ground input port, so that a simple device can be used to realize both transmission of voltage and blocking or reducing of RF signal transmission.

[0045] In the fourth aspect, the embodiments of the present application provide another transmitting optical module, which comprises a direct modulation laser and a second lumped element network, wherein a first end of the second lumped element network is used to connect a RF output end of a RF transmission circuit, a second end of the second lumped element network is connected with a signal input port of the direct modulation laser to perform impedance matching through the second lumped element network. In order to reduce loss, the second lumped element network comprises a plurality of transmitting matching capacitors and a plurality of transmitting matching inductors, the plurality of transmitting matching inductors are connected in series between the RF output end of the RF transmission circuit and the signal input port of the direct modulation laser, two ends of at least part of the transmitting matching inductors are connected with a first end of one transmitting matching capacitor in one-to-one correspondence, and second ends of the plurality of transmitting matching capacitors are used to connect a ground input port. In this way, impedance matching can be realized by using capacitors and inductors instead of resistors, and loss in the process of RF signal transmission can be reduced.

[0046] And, in the present application, based on the DC current (I)-voltage (V) data, scattering parameter data and output different optical power actually measured under different bias voltage and different frequency, the direct modulation laser circuit model related to bias voltage, frequency and output optical power can be established to accurately characterize the electro-optical conversion process of the direct modulation laser. Then, the established laser circuit model is used, and based on the requirements of matching a large bandwidth (for example, 2GHz-6GHz) and a transmission coefficient greater than or equal to 0.9, simulation is performed to obtain the number of capacitors and inductors that meet the above requirements, and the change law of the capacitance value of the capacitor and the inductance value of the inductor. Among them, in the direction from the radio frequency output end of the radio frequency transmission circuit to the signal input port of the direct modulation laser, the inductance values of the plurality of transmitting matching inductors show an increasing trend, and the capacitance values of the plurality of transmitting matching capacitors show an increasing trend. Based on this, the capacitors and inductors in the second lumped element network are designed to achieve impedance matching, which can minimize the loss of the radio frequency signal in the output process, effectively reduce the loss of the radio frequency signal in the output process compared with using resistance for impedance matching, thereby improving the gain of the entire RoF network system, reducing the noise coefficient, and thus obtaining a high-performance RoF transmission link.

[0047] In some embodiments, the plurality of transmitting matching inductors includes a first transmitting matching inductor, a second transmitting matching inductor, and a third transmitting matching inductor, and the plurality of transmitting matching capacitors includes a first transmitting matching capacitor, a second transmitting matching capacitor, and a third transmitting matching capacitor, wherein a first end of the first transmitting matching inductor, a first end of the first transmitting matching capacitor, and a first end of the second lumped element network are connected to each other, a second end of the first transmitting matching inductor, a first end of the second transmitting matching inductor, and a first end of the second transmitting matching capacitor are connected to each other, a second end of the second transmitting matching inductor, a first end of the third transmitting matching inductor, and a first end of the third transmitting matching capacitor are connected to each other, a second end of the third transmitting matching inductor is connected to a second end of the second lumped element network, and a second end of the first transmitting matching capacitor, a second end of the second transmitting matching capacitor, and a second end of the third transmitting matching capacitor are all used to connect the ground input port. With this arrangement, the second lumped element network can be implemented using a simple structure to achieve impedance matching.

[0048] In some embodiments, the transmitting optical module further includes a second transmitting inductor, a first end of the second transmitting inductor is connected to the signal input port of the direct modulation laser, and a second end of the second transmitting inductor is used to connect the power supply input port. With this arrangement, simple devices can be used to not only transmit voltage but also block or reduce the amount of radio frequency signal passing through.

[0049] In some embodiments, the transmitting optical module further comprises a third transmitting ground capacitor, a first electrode of the third transmitting ground capacitor is connected with the ground port of the direct modulation laser, and a second electrode of the third transmitting ground capacitor is used to connect the ground input port. With the arrangement, simple devices can be used to realize both transmission of voltage and blocking or reducing of RF signal passing amount.

[0050] In some embodiments, the transmitting optical module further comprises a fourth transmitting ground capacitor, a first electrode of the fourth transmitting ground capacitor is connected with the ground port of the direct modulation laser, and a second electrode of the fourth transmitting ground capacitor is used to connect the ground input port. With the arrangement, simple devices can be used to realize both transmission of voltage and blocking or reducing of RF signal passing amount.

[0051] In the fifth aspect, the embodiments of the present application further provide a transceiving optical module, which comprises one or more receiving optical modules and one or more transmitting optical modules. The receiving optical module is the receiving optical module in the first aspect or the receiving optical module in any of the embodiments of the first aspect, or the receiving optical module is the receiving optical module in the second aspect or the receiving optical module in any of the embodiments of the second aspect. And the transmitting optical module is the transmitting optical module in the third aspect or the transmitting optical module in any of the embodiments of the third aspect, or the transmitting optical module is the transmitting optical module in the fourth aspect or the transmitting optical module in any of the embodiments of the fourth aspect. Due to the transmitting optical module and the receiving optical module described above, the loss of RF signal in the output process can be reduced as much as possible, compared with using a resistor for impedance matching, the loss of RF signal in the output process can be effectively reduced, so as to improve the gain of the entire RoF network system, reduce the noise coefficient, and thus a high-performance RoF transmission link can be obtained.

[0052] In the sixth aspect, the embodiments of the present application further provide an electronic device, which comprises the receiving optical module in the first aspect or the receiving optical module in any of the embodiments of the first aspect, or the receiving optical module in the second aspect or the receiving optical module in any of the embodiments of the second aspect; or the transmitting optical module in the third aspect or the transmitting optical module in any of the embodiments of the third aspect, or the transmitting optical module in the fourth aspect or the transmitting optical module in any of the embodiments of the fourth aspect; or the transceiving optical module in the fifth aspect. The electronic device can be various devices, such as a server, a routing device, a switching device or other communication devices. BRIEF DESCRIPTION OF DRAWINGS

[0053] FIG. 1a is a structural schematic diagram of an optical wireless network system in the related art;

[0054] FIG. 1b is another structural schematic diagram of an optical wireless network system in the related art;

[0055] FIG. 2 is a structural block diagram of a receiving optical module provided by the embodiments of the present application;

[0056] Fig. 3a is a structural schematic diagram of a first stepped transformation planar transmission line, a radio frequency transmission circuit and a photoelectric detector according to an embodiment of the present application;

[0057] Fig. 3b is another structural schematic diagram of a first stepped transformation planar transmission line, a radio frequency transmission circuit and a photoelectric detector according to an embodiment of the present application;

[0058] Fig. 3c is still another structural schematic diagram of a first stepped transformation planar transmission line, a radio frequency transmission circuit and a photoelectric detector according to an embodiment of the present application;

[0059] Fig. 4 is a three-dimensional structural schematic diagram of a receiving optical module and an optical fiber according to an embodiment of the present application;

[0060] Fig. 5a is an equivalent circuit structural schematic diagram of a receiving optical module according to an embodiment of the present application;

[0061] Fig. 5b is a specific structural schematic diagram corresponding to Fig. 5a;

[0062] Fig. 6 is another equivalent circuit structural schematic diagram of a receiving optical module according to an embodiment of the present application;

[0063] Fig. 7 is still another equivalent circuit structural schematic diagram of a receiving optical module according to an embodiment of the present application;

[0064] Fig. 8 is a structural block diagram of a transmitting optical module according to an embodiment of the present application;

[0065] Fig. 9 is a structural schematic diagram of a second stepped transformation planar transmission line, a radio frequency transmission circuit and a directly modulated laser according to an embodiment of the present application;

[0066] Fig. 10a is a structural schematic diagram of a transmitting optical module according to an embodiment of the present application;

[0067] Fig. 10b is a structural schematic diagram of a transmitting PCB according to an embodiment of the present application;

[0068] Fig. 11 is an equivalent circuit structural schematic diagram of a receiving optical module according to an embodiment of the present application;

[0069] Fig. 12 is another equivalent circuit structural schematic diagram of a transmitting optical module according to an embodiment of the present application.

[0070] 10 - center side communication device; 11 - baseband signal processing circuit; 12 - first radio frequency transmission circuit; 13 / 23 / 500 - transmitting optical module; 15 / 24 - transceiving optical module; 20 - remote side communication device; 14 / 21 / 200 - receiving optical module; 22 - second radio frequency transmission circuit; 211 - photodetector; 212 - first ladder transfer plane transmission line; 213 - housing; 2131 - accommodating space; 214 - first lumped element network; 310 - first receiving component; 311 - first quarter wavelength transmission line; 320 - second receiving component; 411 - metal shielding layer; 412 - grounding line; 413 - switching line; 414 - power supply transmission line; 511 - directly modulated laser; 512 - second ladder transfer plane transmission line; 513 - second lumped element network; 610 - first transmitting component; CP1 - first receiving grounding capacitor; CP2 - second receiving grounding capacitor; CP3 - third receiving grounding capacitor; CP4 - fourth receiving grounding capacitor; CP5 - fifth receiving grounding capacitor; CP6 - sixth receiving grounding capacitor; LP1 - first receiving inductor; LP2 - second receiving inductor; LP3 - third receiving inductor; CY1 - first transmitting grounding capacitor; CY2 - second transmitting grounding capacitor; CY3 - third transmitting grounding capacitor; CY4 - fourth transmitting grounding capacitor; LY1 - first transmitting inductor; LY2 - second transmitting inductor; Lm1 - first receiving matching inductor; Lm2 - second receiving matching inductor; Ln1 - first transmitting matching inductor; Ln2 - second transmitting matching inductor; Ln3 - third transmitting matching inductor; Cm1 - first receiving matching capacitor; Cm2 - second receiving matching capacitor; Cm3 - third receiving matching capacitor; Cn1 - first transmitting matching capacitor; Cn2 - second transmitting matching capacitor; Cn3 - third transmitting matching capacitor; G LD - ground port; S LD - signal input port; F1 - first direction; F2 - second direction; S PD - signal output port; G PD1 - first ground port; G PD2 - second ground port. DETAILED DESCRIPTION

[0071] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings. The specific operation methods in the method embodiments can also be applied to the device embodiments or system embodiments. It should be noted that in the description of the present application, "multiple" can be understood as "at least two". In addition, it should be understood that in the description of the present application, the words "first", "second", etc. are only used for the purpose of distinguishing the description, and cannot be understood as indicating or implying relative importance, nor can it be understood as indicating or implying order.

[0072] It should be noted that the same reference signs in the drawings of the present application represent the same or similar structures, and thus repeated description thereof will be omitted. The words expressing position and direction described in the present application are described with reference to the drawings, but can be changed as needed, and the changes are included in the scope of protection of the present application. The drawings of the present application are only used to show the relative positional relationship and do not represent the true proportion.

[0073] The receiving optical module, the transmitting optical module and the transceiving optical module provided by the embodiments of the present application are described below in combination with the drawings.

[0074] The RoF transmission link can be divided into direct modulation type and external modulation type according to the modulation type. Among them, the direct modulation type RoF transmission link has the advantages of effective low cost, high integration, etc., and is the most mature in application. The embodiments of the present application mainly improve the transmitting optical module and the receiving optical module in the direct modulation type RoF transmission link.

[0075] FIG. 1a is a schematic diagram of a structure of an optical wireless network system in the related art. Referring to FIG. 1a, the RoF network system can include a center side communication device 10 and a remote side communication device 20, and the center side communication device 10 and the remote side communication device 20 are connected through an optical fiber. The center side communication device 10 includes a baseband signal processing circuit 11, a first radio frequency transmission circuit 12 and a transmitting optical module 13, the output end of the baseband signal processing circuit 11 is connected with the radio frequency transmission end of the first radio frequency transmission circuit 12, the radio frequency output end of the first radio frequency transmission circuit 12 is connected with the radio frequency input port of the transmitting optical module 13, and the output end of the transmitting optical module 13 is used to connect the optical fiber. The remote side communication device 20 includes a receiving optical module 21 and a second radio frequency transmission circuit 22, the input end of the receiving optical module 21 is used to connect the optical fiber, and the radio frequency output port of the receiving optical module 21 is connected with the radio frequency input end of the second radio frequency transmission circuit 22.

[0076] In operation, the center side communication device 10 generates a baseband signal, and converts the baseband signal into a radio frequency signal through the baseband signal processing circuit 11 and the first radio frequency transmission circuit 12, and then converts the radio frequency signal into an optical signal through the transmitting optical module 13, and transmits the optical signal to the remote side communication device 20 through the optical fiber. In the remote side communication device 20, the received optical signal is converted into a radio frequency signal through the receiving optical module 21, and then the radio frequency signal is transmitted through the second radio frequency transmission circuit 22.

[0077] Fig. 1b is another structural schematic diagram of a radio-over-fiber network system in the related art. Referring to Fig. 1b, the RoF network system can include a center-side communication device 10 and a remote-side communication device 20 connected through an optical fiber. The center-side communication device 10 includes a baseband signal processing circuit 11, a first radio frequency transmission circuit 12, and a transceiver optical module 15, which can include a transmitting optical module 13 and a receiving optical module 14. The output of the baseband signal processing circuit 11 is connected to the first radio frequency transmission end of the first radio frequency transmission circuit 12. The radio frequency output of the first radio frequency transmission circuit 12 is connected to the radio frequency input port of the transmitting optical module 13. The output of the transmitting optical module is used to connect the optical fiber. The radio frequency input of the first radio frequency transmission circuit 12 is connected to the radio frequency output port of the receiving optical module 14. The input of the receiving optical module 14 is used to connect the optical fiber. The remote-side communication device 20 includes a transceiver optical module 24 and a second radio frequency transmission circuit 22, which can include a transmitting optical module 23 and a receiving optical module 21. The input of the receiving optical module 21 is used to connect the optical fiber. The radio frequency output port of the receiving optical module 21 is connected to the radio frequency input of the second radio frequency transmission circuit 22. The radio frequency input port of the transmitting optical module 23 is connected to the radio frequency output of the second radio frequency transmission circuit 22. The output of the transmitting optical module 23 is used to connect the optical fiber. It can be understood that the transceiver optical module can be one or more, and the transmitting optical module and the receiving optical module in the transceiver optical module can also be one or more, which is not limited herein.

[0078] In operation, the central side communication device 10 generates a baseband signal, and converts the baseband signal into a radio frequency signal through the baseband signal processing circuit 11 and the first radio frequency transmission circuit 12, and then converts the radio frequency signal into an optical signal through the transmitting optical module 13, and transmits the optical signal to the remote side communication device 20 through an optical fiber. In the remote side communication device 20, the received optical signal is converted into a radio frequency signal through the receiving optical module 21, and then the radio frequency signal is transmitted through the second radio frequency transmission circuit 22. In addition, the second radio frequency transmission circuit 22 can also receive a radio frequency signal and output the received radio frequency signal to the transmitting optical module 23, convert the radio frequency signal into an optical signal through the transmitting optical module 23, and then transmit the optical signal to the central side communication device 10 through an optical fiber. In the central side communication device 10, the received optical signal is converted into a radio frequency signal through the receiving optical module 14 and output to the first radio frequency transmission circuit 12. In some embodiments, the first radio frequency transmission circuit 12 in FIG. 1b not only has the function of transmitting a radio frequency signal to the transmitting optical module 13, but also has the function of receiving a radio frequency signal output from the receiving optical module 14. In addition, the second radio frequency transmission circuit 22 not only has the function of receiving a radio frequency signal output from the receiving optical module 21, but also has the function of receiving a radio frequency signal output from an external device (such as a terminal device), and outputting the received radio frequency signal output from the external device to the transmitting optical module 23 after a series of processing.

[0079] In a RoF transmission link, a direct modulation laser scheme is usually used in a transmitting optical module. Since the internal resistance of a direct modulation laser is generally 5-10 ohms, a 40-45 ohm resistor is usually connected in series between the radio frequency transmission circuit (such as the first radio frequency transmission circuit 12 in FIGS. 1a and 1b or the second radio frequency transmission circuit 22 in FIG. 1b) and the direct modulation laser to achieve impedance matching. However, in actual applications, a large part of the power of the radio frequency signal transmitted by the radio frequency transmission circuit is consumed by the 40-45 ohm resistor connected in series, resulting in a decrease in the power of the radio frequency signal transmitted to the direct modulation laser, and causing the electro-optical modulation efficiency of the direct modulation laser to decrease.

[0080] In addition, in a RoF transmission link, a photodetector is usually used in a receiving optical module. Since the internal resistance of the photodetector is usually as high as several thousand ohms, a 50 ohm resistor is usually connected in parallel between the radio frequency transmission circuits (such as the second radio frequency transmission circuit 22 in FIGS. 1a and 1b or the first radio frequency transmission circuit 12 in FIG. 1b) to achieve impedance matching. However, in actual applications, the 50 ohm resistor connected in parallel will divert a part of the output photocurrent, resulting in a 6 dB matching loss in the power of the radio frequency signal output by the photodetector.

[0081] Therefore, in the RoF transmission link, the current resistance matching scheme of the transmitting optical module and the receiving optical module is lossy matching, which results in low gain (e.g., -45 dB ~ 25 dB) and poor noise figure (e.g., 35 dB ~ 56 dB) of the RoF link, greatly limiting the application range of the RoF technology. Therefore, the embodiments of the present application provide a transmitting optical module and a receiving optical module to reduce loss, improve gain, and reduce noise.

[0082] The structure of the receiving optical module provided by the embodiments of the present application will be described in detail below in combination with specific embodiments. It can be understood that the following embodiments are only illustrative of the specific structure of the receiving optical module, and in specific implementation, the specific structure of the receiving optical module is not limited to the following structure provided by the embodiments of the present application, but can also be other structures known by those skilled in the art based on the same concept, which is not limited herein.

[0083] FIG. 2 is a structural block diagram of a receiving optical module provided by an embodiment of the present application. Referring to FIG. 2, the receiving optical module 200 provided by the embodiments of the present application can include a photodetector 211 and a first stepped transformation planar transmission line 212. The signal output port S of the photodetector 211 is connected to the signal input port of the first stepped transformation planar transmission line 212, and the ground port G of the photodetector 211 is connected to the ground port of the first stepped transformation planar transmission line 212. PD The first stepped transformation planar transmission line 212 is connected to the RF input end of the corresponding RF transmission circuit 110, so as to perform impedance matching through the first stepped transformation planar transmission line 212. In addition, the input end of the photodetector 211 is used to input an optical signal, and the photodetector 211 outputs an RF signal after photoelectric conversion of the optical signal. The RF signal is input to the corresponding RF transmission circuit 110 through the first stepped transformation planar transmission line 212, and the RF signal is output through the RF transmission circuit 110. The photodetector involved in the present application can include a photodiode (PD), for example, the photodiode includes one or more of a PIN photodiode (PIN-PD) and an avalanche photodiode (APD). In some embodiments, the photodetector can be a PD chip, and the PD chip can include various structures, for example, the PD chip can include a ground-signal-ground (GSG) type PD chip or a ground-signal (GS) type PD chip. The GSG type PD chip can have three ports: a signal output port, a first ground port, and a second ground port. The GS type PD chip can have two ports: a signal output port and a first ground port. In some embodiments, the connection mode between the signal output port of the PD chip and the first stepped transformation planar transmission line can be designed according to the specific form of the PD chip. Exemplarily, the connection mode includes but is not limited to welding, wire bonding (such as gold wire bonding), etc.

[0084] In some embodiments of the present application, based on the measured different input optical power, and direct current, scatter (S) parameter data under different bias voltage and different frequency, a photodetector circuit model related to input optical power, bias voltage and frequency can be established to accurately characterize the photoelectric conversion process of the photodetector. The photodetector circuit model can include three regions: a direct current parameter region, a chip intrinsic region, and a parasitic parameter region. The direct current parameter region includes a voltage-controlled current source and a diode connected in parallel to represent the direct current parameter characteristics of the photodetector with the voltage-controlled current source and the diode in parallel. The chip intrinsic region includes a first capacitor and a first resistor to represent the junction capacitance of the photodetector with the first capacitor (the junction capacitance is a variable capacitance, and the junction capacitance is related to the bias voltage and the optical power), and to represent the drift resistance of the photodetector with the first resistor (the drift resistance is a variable resistance, and the drift resistance is related to the bias voltage and the optical power). The parasitic parameter region includes a second capacitor, a second resistor, and a first inductor to represent the parasitic resistance of the photodetector with the second resistor, to represent the parasitic inductance of the photodetector with the first inductor, and to represent the parasitic capacitance of the photodetector with the second capacitor.

[0085] With the established photodetector circuit model, and based on the requirement of matching a large bandwidth (for example, 10GHz-13GHz) and a transmission coefficient greater than or equal to 0.9, simulation is performed to obtain a first stepped transformation planar transmission line that meets the above requirements. That is, the first stepped transformation planar transmission line needs to be segmented, and the impedances of adjacent segments need to be designed to be different. Based on this, the first stepped transformation planar transmission line is designed to achieve impedance matching, which can minimize the loss of the radio frequency signal in the output process, effectively reduce the loss of the radio frequency signal in the output process compared to using a resistor for impedance matching, thereby improving the gain of the entire RoF network system, reducing the noise coefficient, and thus obtaining a high-performance RoF transmission link.

[0086] In some embodiments, the first stepped transformation planar transmission line 212 can include sequentially connected 1st transmission line sub-segment to Mth transmission line sub-segment, the 1st transmission line sub-segment is connected with the signal output port S PD In some examples, the receiving optical module 200 of the present application can be applied to the remote side communication device 20 in the scenario shown in FIG. 1a and FIG. 1b, and then the Mth transmission line sub-segment connected radio frequency transmission circuit 110 can be the second radio frequency transmission circuit 22. In yet other examples, the receiving optical module 200 of the present application can be applied to the center side communication device 10 in the scenario shown in FIG. 1b, and then the Mth transmission line sub-segment connected radio frequency transmission circuit 110 can be the first radio frequency transmission circuit 12.

[0087] And M can be an integer and M≥3, that is, the first ladder transformation plane transmission line 212 is divided into at least 3 segments. In order to match the impedance, and meet the requirements of matching a large bandwidth (for example, 10GHz-13GHz) and a transmission coefficient greater than or equal to 0.9, the impedance of at least one of the second transmission line segment to the M-1th transmission line segment can be less than the impedance of the first transmission line segment. Through simulation, it is found that if the impedance of the first transmission line segment to the Mth transmission line segment is set to increase in an increasing trend from small to large, impedance matching can also be achieved, but when using this impedance change trend for impedance matching, the bandwidth is usually less than 0.5GHz, resulting in a narrow matching bandwidth and a greatly limited application range.

[0088] In order to match a larger bandwidth and improve the transmission coefficient, the difference between the impedance Rx1 of the first transmission line segment and the output impedance R PD of the signal output port S SPD of the photodetector 211 can be close to zero or equal to zero, and the difference between the impedance Rx M of the Mth transmission line segment and the input impedance R in of the input end of the corresponding radio frequency transmission circuit 110 can be close to zero or equal to zero.

[0089] It can be understood that the difference between the impedance R X1 of the first transmission line segment and the output impedance R PD of the signal output port S SPD of the photodetector 211 close to zero means that the difference can be between ±ΔR m1 . Wherein, ΔR m1 may be equal to 0, or ΔR m1 may not be equal to 0, but a value close to zero, for example, ΔR m1 may be 0.001, -0.01, 0.1, 0.2, 0.3, etc. It can be understood by those skilled in the art that by setting the difference between the impedance R X1 of the first transmission line segment and the output impedance R PD of the signal output port S SPD of the photodetector 211 close to or equal to zero, a large bandwidth, a high transmission coefficient, and a low noise can be achieved. Therefore, in some embodiments, those skilled in the art can set the specific value of ΔR m1 according to the requirements of the actual application scene on the premise of meeting the purpose, which is not limited in this application.

[0090] And the difference between the impedance Rx M of the Mth transmission line segment and the input impedance Rin The difference between the impedance Rx m2 and the input impedance R m2 may be equal to 0, or the difference ΔR m2 may not be equal to 0, but a value close to 0, for example, ΔR m2 may be 0.001, -0.01, 0.1, 0.2, 0.3, etc. Those skilled in the art can understand that when the difference between the impedance Rx M of the Mth transmission line subsection and the input impedance R in of the RF input end of the connected RF transmission circuit 110 is close to 0 or equal to 0, a large bandwidth, a high transmission coefficient, and low noise can be achieved. Therefore, in some embodiments, those skilled in the art can set the specific value of ΔR m2 according to the needs of the actual application scenario on the premise of meeting the purpose, which is not limited in this application. In addition, ΔR m1 and ΔR m2 may be the same or different, which can be determined according to the needs of the actual application scenario, which is not limited here.

[0091] In some embodiments, M≥4, that is, the first stepped transformation plane transmission line 212 is divided into at least 4 sections, and the impedance variation law of the 1st transmission line subsection to the Mth transmission line subsection is adjusted, for example, the impedance of each transmission line subsection in the 1st transmission line subsection to the Mth transmission line subsection can be sequentially reduced, increased, and then reduced, so as to further improve the transmission coefficient on the basis of matching a large bandwidth. Exemplarily, since the 1st transmission line subsection is connected to the signal output port S PD of the photodetector 211, in order to compensate for the impedance of the 1st transmission line subsection, the impedance of each transmission line subsection in the sequentially connected 1st transmission line subsection to the ath transmission line subsection can be sequentially reduced. Since the Mth transmission line subsection is connected to the corresponding RF transmission circuit 110, in order to compensate for the impedance of the Mth transmission line subsection, the impedance of each transmission line subsection in the sequentially connected ath transmission line subsection to the bth transmission line subsection can be sequentially increased and increased to be greater than the impedance of the Mth transmission line subsection. Then, the impedance of each transmission line subsection in the sequentially connected bth transmission line subsection to the Mth transmission line subsection is sequentially reduced.

[0092] In some embodiments, in order to obtain a larger transmission coefficient at certain frequency points (e.g. 2.4 GHz, 5 GHz), a can be set to 2, i.e. the impedance of the 2nd transmission line subsection is smaller than the impedance of the 1st transmission line subsection and the impedance of the 3rd transmission line subsection, or a can also be set to 3, i.e. the impedance of the 3rd transmission line subsection is smaller than the impedance of the 2nd transmission line subsection and the impedance of the 4th transmission line subsection, and the impedance of the 2nd transmission line subsection is smaller than the impedance of the 1st transmission line subsection. With such a setting, the inflection point of the impedance rise can be set at the impedance of the 2nd transmission line subsection or the impedance of the 3rd transmission line subsection, which can further improve the transmission coefficient at certain frequency points.

[0093] In some embodiments, in order to obtain a larger transmission coefficient at certain frequency points (e.g. 2.4 GHz, 5 GHz), b can be set to M-1, i.e. the impedance of the M-1th transmission line subsection is greater than the impedance of the Mth transmission line subsection and the impedance of the M-2th transmission line subsection, or b can also be set to M-2, i.e. the impedance of the M-2th transmission line subsection is greater than the impedance of the M-1th transmission line subsection and the impedance of the M-3th transmission line subsection, and the impedance of the M-1th transmission line subsection is greater than the impedance of the Mth transmission line subsection. With such a setting, the inflection point of the impedance rise can be set at the impedance of the M-1th transmission line subsection or the impedance of the M-2th transmission line subsection, which can further improve the transmission coefficient at certain frequency points.

[0094] In some embodiments, for the specific number of transmission line subsections, a person skilled in the art can select a suitable value based on the needs of performance such as impedance matching, large bandwidth, high transmission coefficient and low noise, as well as considerations such as the size and cost of the receiving optical module 200. For example, the specific number of transmission line subsections can be set to 3-20. In actual applications, if the number of transmission line subsections is too small, the impedance variation trend of the transmission line subsections will not be effective. If the number of transmission line subsections is too large, it will result in a too large size, increased loss, and increased difficulty in design and processing, resulting in increased cost. Therefore, taking into account the influence of cost and performance, in some embodiments, 4≤M≤10 is set to balance the influence of cost and performance. For example, M can be 4, 6, 8, 9, 10, etc., which is not limited herein.

[0095] In some embodiments, the first stepped transformation planar transmission line 212 can be formed by a stepped transformation microstrip line or a stepped transformation stripline. For example, when the first stepped transformation planar transmission line 212 is set as a stepped transformation microstrip line, the stepped transformation microstrip line is divided into the 1st transmission line subsection to the Mth transmission line subsection. When the first stepped transformation planar transmission line 212 is set as a stepped transformation stripline, the stepped transformation stripline is divided into the 1st transmission line subsection to the Mth transmission line subsection.

[0096] The following takes the first stepped transformation planar transmission line 212 formed by using stepped transformation microstrip line as an example to illustrate the structure of the first stepped transformation planar transmission line 212 provided by the embodiments of the present application.

[0097] FIG. 3a is a schematic diagram of one structure of the first stepped transformation planar transmission line 212, the radio frequency transmission circuit 110 and the photoelectric detector 211 provided by the embodiments of the present application. Referring to FIG. 3a, the first stepped transformation planar transmission line 212 can include the first transmission line sub-section Xa1 to the sixth transmission line sub-section Xa6 connected in sequence, wherein the first transmission line sub-section Xa1 is connected to the signal output port S PD The electrical connection can be realized by welding or wire bonding (such as gold wire bonding), the first transmission line sub-section Xa1 to the sixth transmission line sub-section Xa6 are connected in series in sequence, and the sixth transmission line sub-section Xa6 is used to connect the radio frequency input end of the corresponding radio frequency transmission circuit 110. Moreover, the impedances of the first transmission line sub-section Xa1 to the sixth transmission line sub-section Xa6 can satisfy the following relationship: R Xa2 <R Xa1 , R Xa2 <R Xa3 , R Xa3 <R Xa4 , R Xa4 <R Xa5 , R Xa5 >R Xa6 . Wherein, R Xa1 represents the impedance of the first transmission line sub-section Xa1, R Xa2 represents the impedance of the second transmission line sub-section Xa2, R Xa3 represents the impedance of the third transmission line sub-section Xa3, R Xa4 represents the impedance of the fourth transmission line sub-section Xa4, R Xa5 represents the impedance of the fifth transmission line sub-section Xa5, and R Xa6 represents the impedance of the sixth transmission line sub-section Xa6.

[0098] FIG. 3b is another schematic diagram of one structure of the first stepped transformation planar transmission line 212, the radio frequency transmission circuit 110 and the photoelectric detector 211 provided by the embodiments of the present application. Referring to FIG. 3b, the first stepped transformation planar transmission line 212 can include the first transmission line sub-section Xb1 to the sixth transmission line sub-section Xb6 connected in sequence, wherein the first transmission line sub-section Xb1 is connected to the signal output port S PD The electrical connection can be realized by welding or wire bonding, the first transmission line sub-section Xb1 to the sixth transmission line sub-section Xb6 are connected in series in sequence, and the sixth transmission line sub-section Xb6 is used to connect the radio frequency input end of the corresponding radio frequency transmission circuit 110. Moreover, the impedances of the first transmission line sub-section Xb1 to the sixth transmission line sub-section Xb6 can satisfy the following relationship: RXb2 <R Xb1 , R Xb3 <R Xb2 , R Xb3 <R Xb4 , R Xb4 <R Xb5 , R Xb5 <R Xb6 , R Xb1 represents the impedance of the first transmission line sub-section Xb1, R Xb2 represents the impedance of the second transmission line sub-section Xb2, R Xb3 represents the impedance of the third transmission line sub-section Xb3, R Xb4 represents the impedance of the fourth transmission line sub-section Xb4, R Xb5 represents the impedance of the fifth transmission line sub-section Xb5, and R Xb6 represents the impedance of the sixth transmission line sub-section Xb6.

[0099] Fig. 3c is another structural schematic diagram of the first ladder conversion planar transmission line 212, the radio frequency transmission circuit 110 and the photoelectric detector 211 provided by the embodiment of the present application. Referring to Fig. 3c, the first ladder conversion planar transmission line 212 can include the first transmission line sub-section Xc1 to the ninth transmission line sub-section Xc9 connected in sequence, wherein the first transmission line sub-section Xc1 is connected to the signal output port S PD The electrical connection can be realized by welding or wire bonding, the first transmission line sub-section Xc1 to the ninth transmission line sub-section Xc9 are connected in series in sequence, and the ninth transmission line sub-section Xc9 is used to connect the radio frequency input end of the corresponding radio frequency transmission circuit 110. Moreover, the impedances of the first transmission line sub-section Xc1 to the ninth transmission line sub-section Xc9 can satisfy the following relationship: R Xc2 <R Xc1 , R Xc3 <R Xc2 , R Xc3 <R Xc4 , R Xc4 <R Xc5 , R Xc5 <R Xc6 , R Xc6 <R Xc7 , R Xc7 <R Xc8 , R Xc8 <R Xc9 , R Xc1 represents the impedance of the first transmission line sub-section Xc1, R Xc2 represents the impedance of the second transmission line sub-section Xc2, R Xc3 represents the impedance of the third transmission line sub-section Xc3, R Xc4 represents the impedance of the fourth transmission line sub-section Xc4, R Xc5R represents the impedance of the 5th transmission line sub-section Xc5 Xc6 R represents the impedance of the 6th transmission line sub-section Xc6 Xc7 R represents the impedance of the 7th transmission line sub-section Xc7 Xc8 R represents the impedance of the 8th transmission line sub-section Xc8 Xc9 R represents the impedance of the 9th transmission line sub-section Xc9

[0100] It can be understood that the above embodiments are only illustrative of the specific structure of the first ladder conversion planar transmission line 212, and in specific implementation, the specific structure of the first ladder conversion planar transmission line 212 is not limited to the above structure provided by the embodiments of the present application, but can also be other structures known by those skilled in the art based on the same concept, which is not limited here.

[0101] In some embodiments of the present application, the first stepped transformation planar transmission line 212 is integrated with the photodetector 211 as a separate device (such as a PD chip) to form a receiving optical module 200, and the receiving optical module 200 is mounted or arranged on a circuit board (such as a printed circuit board (PCB)) provided with a corresponding radio frequency transmission circuit, so that the receiving optical module 200 is electrically connected with the corresponding radio frequency transmission circuit. For example, referring to FIG. 4, which is a three-dimensional structural schematic diagram of a receiving optical module and an optical fiber according to an embodiment of the present application, the receiving optical module 200 can include a housing 213, the housing 213 having an accommodation space 2131 inside, and a substrate (such as an insulating substrate) is arranged in the accommodation space 2131, and the PD chip and the first stepped transformation planar transmission line 212 are arranged on the substrate. In the first direction F1, an optical fiber connection port is arranged on one surface of the housing 213, one side of the optical fiber connection port is connected with a PD optical coupling assembly, and the other side of the optical fiber connection port is used to connect one end of an optical fiber access assembly, and the other end of the optical fiber access assembly is connected with an optical fiber. In operation, the light of the optical fiber is coupled into the light receiving area of the PD chip through the PD optical coupling assembly, and the photoelectric conversion is performed through the PD chip to output a radio frequency signal. In the second direction F2, a power supply input port assembly, a radio frequency output port assembly, and a ground input port assembly are arranged on one surface of the housing 213 at intervals, wherein the power supply input port assembly can be used as a power supply input port to input a direct current voltage, the radio frequency output port assembly can be used as the radio frequency output port to output the radio frequency signal to the second radio frequency transmission circuit 22, and the ground input port assembly can be used as a ground input port to realize grounding. In some embodiments, the power supply input port assembly, the radio frequency output port assembly, and the ground input port assembly can be inserted into the circuit board to realize the conduction of the direct current voltage and the ground voltage and the transmission of the radio frequency signal. It can be understood that the first stepped transformation planar transmission line 212 can also be integrated in the PD chip to improve the integration and further realize miniaturization.

[0102] Since the PD chip has not only a signal output port but also a ground port, other components need to be arranged in the receiving optical module 200 to realize the overall function of the PD chip.

[0103] Fig. 5a is a schematic diagram of an equivalent circuit structure of a receiving optical module according to an embodiment of the present application, and Fig. 5b is a schematic diagram of a specific structure corresponding to Fig. 5a. Referring to Figs. 5a and 5b, taking the structure of the first stepped transformation planar transmission line 212 shown in Fig. 3a and a GSG type PD chip as an example, the receiving optical module 200 can include: a photodetector 211 disposed on a substrate, the first stepped transformation planar transmission line 212, a first receiving component 310, a first receiving ground capacitor CP1, a second receiving component 320, and a third receiving ground capacitor CP3. The signal output port S PD The sixth transmission line segment Xa6 is connected with the radio frequency output port of the receiving optical module 200, and the radio frequency output port of the receiving optical module 200 is connected with a corresponding radio frequency transmission circuit. The first end of the first receiving component 310 is connected with one of the first transmission line segment Xa1 to the Mth transmission line segment, and the second end of the first receiving component 310 is used to connect the ground input port. The first electrode of the first receiving ground capacitor CP1 is connected with the first ground port G PD1 of the photodetector 211, and the second electrode of the first receiving ground capacitor CP1 is used to connect the ground input port. The first end of the second receiving component 320 is connected with the first ground port G PD1 of the photodetector 211, and the second end of the second receiving component 320 is used to connect the power supply input port. The first electrode of the third receiving ground capacitor CP3 is connected with the second ground port G PD2 of the photodetector 211, and the second electrode of the third receiving ground capacitor CP3 is used to connect the ground input port, so that the second ground port G PD2 of the photodetector 211 is grounded through the third receiving ground capacitor CP3. In this way, the receiving optical module can be implemented by using simple devices, which can not only reduce the transmission loss of the radio frequency signal, but also reduce the cost.

[0104] The first receiving component 310 is used to couple the signal of the ground input port to the transmission line segment connected therewith, so that the ground voltage input by the ground input port can be input to the signal output port S PD of the photodetector 211. Moreover, since the signal output port S PD of the photodetector 211 is used to output the radio frequency signal, in order to avoid the radio frequency signal from leaking to the ground, the first receiving component 310 can also be used to block the radio frequency signal, so that the radio frequency signal can enter the corresponding radio frequency transmission circuit through the first stepped transformation planar transmission line 212 as much as possible. Further, in order to reduce the influence of the first receiving component 310 on the impedance of each transmission line segment in the first stepped transformation planar transmission line 212 and the radio frequency signal leakage, the first end of the first receiving component 310 can be connected to the connection between the first transmission line segment and the second transmission line segment.

[0105] For example, referring to FIG. 5b, the first receiving component 310 can include a first quarter wavelength transmission line 311. Alternatively, the first receiving component 310 can also include a first receiving inductor. In this way, simple devices can be used to achieve both transmission of voltage and blocking or reducing of RF signal transmission. Of course, in actual applications, the first receiving component 310 can also be configured as other devices that can achieve the above functions, which are not limited herein. In addition, the purpose of configuring the first receiving component 310 is to transmit the ground voltage and to block the RF signal transmission. However, in actual applications, a small amount of RF signal can leak to the ground through the first receiving component 310, but the leakage is usually not too much, and the influence on the transmission coefficient and noise is small and can be ignored.

[0106] The second receiving component 320 and the first receiving ground capacitor CP1 are respectively used to couple the signal of the power supply input port to the first ground port G PD1 , so as to input the DC voltage input by the power supply input port to the first ground port G PD1 of the photodetector 211. In addition, in order to avoid the RF signal generated by the photodetector 211 from leaking to the power supply input port, the second receiving component 320 can be used to block the RF signal transmission, so that the RF signal is transmitted into the corresponding RF transmission circuit through the first stepped transformation plane transmission line 212 as much as possible. For example, referring to FIG. 5a and FIG. 5b, the second receiving component 320 can include a second receiving inductor LP2. In this way, simple devices can be used to achieve both transmission of ground voltage and blocking or reducing of RF signal transmission. Of course, in actual applications, the second receiving component 320 can also be configured as other devices that can achieve the above functions, for example, a second quarter wavelength transmission line, which are not limited herein. In addition, the second receiving component 320 is configured to transmit the ground voltage and to block or reduce the RF signal transmission. In actual applications, a small amount of RF signal can leak to the DC voltage end through the second receiving component 320, but the leaked RF signal is usually weak, and the influence on the transmission coefficient and noise is small and can be ignored.

[0107] Referring to FIG. 5b, the photodetector 211 and the first stepped transformation planar transmission line 212 are disposed on one side of the substrate, and a whole surface of the other side of the substrate is coated with a ground conductive layer (for example, a metal layer), which is connected to a ground input port assembly. The sixth transmission line subsegment of the first stepped transformation planar transmission line 212 is connected to a radio frequency output port assembly. In order to reduce signal interference, a metal shielding layer 411 can be disposed between the photodetector 211 and the substrate, and the metal shielding layer 411 is connected to the ground conductive layer through a plurality of vias AX1 penetrating the substrate to achieve grounding. The metal shielding layer can also serve as the second electrode of the first receiving ground capacitor CP1 and the second electrode of the third receiving ground capacitor CP3. Alternatively, the second electrode of the first receiving ground capacitor CP1 and the second electrode of the third receiving ground capacitor CP3 can also be connected to the metal shielding layer by soldering or other connection methods. In addition, the first end of the first quarter wavelength transmission line 311 is connected to the junction between the first transmission line subsegment Xa1 and the second transmission line subsegment Xa2. The side of the substrate provided with the photodetector 211 is also provided with a ground wire 412, and the second end of the first quarter wavelength transmission line is connected to the ground wire 412, and the ground wire 412 is connected to the ground conductive layer through a plurality of vias AX2 penetrating the substrate to achieve grounding. The side of the substrate provided with the photodetector 211 is also provided with a switching wire 413, and the first electrode of the first receiving ground capacitor CP1 is connected to the switching wire 413 by wire bonding (for example, gold wire bonding), and the first end of the second receiving inductor is also connected to the switching wire 413 by wire bonding (for example, gold wire bonding), to achieve the mutual connection between the first electrode of the first receiving ground capacitor CP1, the first end of the second receiving inductor, and the first ground port G PD1 of the photodetector 211. In addition, the side of the substrate provided with the photodetector 211 is also provided with a power supply transmission line 414, and the second end of the second receiving inductor is connected to the power supply transmission line 414 by wire bonding (for example, gold wire bonding), and the power supply transmission line 414 is connected to a power supply input port assembly to achieve direct current voltage input. It is worth mentioning that FIG. 5b is only an example to illustrate the specific structure that can be achieved by the photodetector 211 and the first stepped transformation planar transmission line 212, and in specific implementation, the specific structure is not limited to the above-mentioned structure provided by the embodiments of the present application, but can also be other structures known by those skilled in the art based on the same concept, which is not limited here.

[0108] Fig. 6 is another equivalent circuit structure diagram of the receiving optical module according to an embodiment of the present application. Referring to Fig. 6, the embodiment is a variation of the embodiment shown in Fig. 5a. The same parts are not described here again. The different parts are as follows: the receiving optical module 200 comprises a photodetector 211, a first stepped transformation planar transmission line 212, a first receiving component 310, a second receiving ground capacitor CP2 and a third receiving ground capacitor CP3. The signal output port S PD The sixth transmission line sub-section Xa6 is connected with the radio frequency output port of the receiving optical module 200, and the radio frequency output port of the receiving optical module 200 is connected with the corresponding radio frequency transmission circuit. The first end of the first receiving component 310 is connected with one of the first transmission line sub-section to the Mth transmission line sub-section, and the second end of the first receiving component 310 is used for connecting the power supply input port. The first electrode of the second receiving ground capacitor CP2 is connected with the first ground port G PD1 of the photodetector 211, and the second electrode of the second receiving ground capacitor CP2 is used for connecting the ground input port, so that the first ground port G PD1 of the photodetector 211 is grounded through the second receiving ground capacitor CP2. The first electrode of the third receiving ground capacitor CP3 is connected with the second ground port G PD2 of the photodetector 211, and the second electrode of the third receiving ground capacitor CP3 is used for connecting the ground input port, so that the second ground port G PD2 of the photodetector 211 is grounded through the third receiving ground capacitor CP3. According to the embodiment, the receiving optical module can be realized by simple devices, and the transmission loss and cost of the radio frequency signal can be reduced.

[0109] Exemplarily, the first receiving component 310 can also be set as a first receiving inductor LP1, which can not only transmit the ground voltage, but also block the radio frequency signal. Alternatively, the first receiving component 310 can be set as a first quarter wavelength transmission line.

[0110] In order to stabilize the direct current voltage, a sixth receiving ground capacitor CP6 can also be arranged in the receiving optical module 200. The first electrode of the sixth receiving ground capacitor CP6 is connected with the first end of the first receiving inductor, and the second electrode of the sixth receiving ground capacitor CP6 is used for connecting the ground input port. Of course, in some other embodiments of the present application, the performance of the receiving optical module 200 meets the requirements, and the sixth receiving ground capacitor CP6 can also be removed to reduce the number of capacitor devices.

[0111] In some embodiments, the specific structure diagram corresponding to Fig. 6 can be designed with reference to Fig. 5b, and details are not described here again.

[0112] In some other embodiments of the present application, in addition to using the first stepped-impedance transmission line for impedance matching, a lumped-element network formed by capacitors and inductors can also be used for impedance matching. For example, FIG. 7 is a schematic diagram of another equivalent circuit structure of a receiving optical module according to an embodiment of the present application. Referring to FIG. 7, the embodiment is a variation of the embodiment shown in FIG. 5a, and the same parts are not described again here. The differences between the two embodiments are as follows: the receiving optical module 200 includes a photodetector 211 and a first lumped-element network 214, wherein a first end of the first lumped-element network 214 is connected to a signal output port S of the photodetector 211, and a second end of the first lumped-element network 214 is connected to a radio frequency input end of a corresponding radio frequency transmission circuit, so that impedance matching is performed through the first lumped-element network 214. In order to reduce loss, the first lumped-element network 214 includes a plurality of receiving matching capacitors (for example, Cm1-Cm3) and a plurality of receiving matching inductors (for example, Lm1-Lm2), and the plurality of receiving matching inductors are connected in series between the signal output port S of the photodetector 211 and the radio frequency input end of the radio frequency transmission circuit. At least one receiving matching capacitor is connected between the two ends of each receiving matching inductor, and the second ends of the plurality of receiving matching capacitors are connected to a ground input port. In this way, instead of using a resistor for impedance matching, a capacitor and an inductor are used to achieve impedance matching, which can reduce the loss in the process of radio frequency signal transmission. PD PD In some embodiments of the present application, based on the measured direct current, scatter (S) parameter data at different input optical powers, different bias voltages and different frequencies, a photodetector circuit model related to the input optical power, the bias voltage and the frequency can be established to accurately characterize the photoelectric conversion process of the photodetector 211. The photodetector circuit model can include three regions: a direct current parameter region, a chip intrinsic region and a parasitic parameter region. The direct current parameter region includes a voltage-controlled current source and a diode connected in parallel to represent the direct current parameter characteristics of the photodetector. The chip intrinsic region includes a third capacitor and a third resistor, wherein the third capacitor is used to represent the junction capacitance of the photodetector (the junction capacitance is a variable capacitance, and the junction capacitance is related to the bias voltage and the optical power), and the third resistor is used to represent the drift resistance of the photodetector (the drift resistance is a variable resistance, and the drift resistance is related to the bias voltage and the optical power). The parasitic parameter region includes a fourth capacitor, a fourth resistor and a second inductor, wherein the fourth resistor is used to represent the parasitic resistance of the photodetector, the second inductor is used to represent the parasitic inductance of the photodetector, and the fourth capacitor is used to represent the parasitic capacitance of the photodetector.

[0113] In some embodiments of the present application, based on the measured direct current, scatter (S) parameter data at different input optical powers, different bias voltages and different frequencies, a photodetector circuit model related to the input optical power, the bias voltage and the frequency can be established to accurately characterize the photoelectric conversion process of the photodetector 211. The photodetector circuit model can include three regions: a direct current parameter region, a chip intrinsic region and a parasitic parameter region. The direct current parameter region includes a voltage-controlled current source and a diode connected in parallel to represent the direct current parameter characteristics of the photodetector. The chip intrinsic region includes a third capacitor and a third resistor, wherein the third capacitor is used to represent the junction capacitance of the photodetector (the junction capacitance is a variable capacitance, and the junction capacitance is related to the bias voltage and the optical power), and the third resistor is used to represent the drift resistance of the photodetector (the drift resistance is a variable resistance, and the drift resistance is related to the bias voltage and the optical power). The parasitic parameter region includes a fourth capacitor, a fourth resistor and a second inductor, wherein the fourth resistor is used to represent the parasitic resistance of the photodetector, the second inductor is used to represent the parasitic inductance of the photodetector, and the fourth capacitor is used to represent the parasitic capacitance of the photodetector.

[0114] ​Based on the established photoelectric detector circuit model, and based on the requirements of matching a large bandwidth (for example, 10GHz-13GHz) and a transmission coefficient greater than or equal to 0.9, simulation is performed to obtain the number of capacitors and inductors that meet the above requirements, as well as the variation law of the capacitance value of the capacitor and the inductance value of the inductor. Among them, in the direction from the signal output port S PD In the direction from the signal output port of the photoelectric detector to the radio frequency input end of the radio frequency transmission circuit, the inductance values of the plurality of receiving matching inductors (for example, Lm1-Lm2) have a decreasing trend, and the capacitance values of the plurality of receiving matching capacitors (for example, Cm1-Cm3) have a decreasing trend. Based on this, the capacitors and inductors in the first lumped element network 214 are designed to achieve impedance matching, which can minimize the loss of the radio frequency signal in the output process, effectively reduce the loss of the radio frequency signal in the output process compared to using a resistor for impedance matching, thereby improving the gain of the entire RoF network system, reducing the noise coefficient, and thus obtaining a high-performance RoF transmission link.

[0115] In some embodiments of the present application, in the direction from the signal output port of the photoelectric detector to the radio frequency input end of the radio frequency transmission circuit, the difference in inductance value of each adjacent receiving matching inductor in the partially or entirely sequentially connected receiving matching inductors can be the same. For example, taking four sequentially connected receiving matching inductors as an example, in the direction from the signal output port of the photoelectric detector to the radio frequency input end of the radio frequency transmission circuit, the four receiving matching inductors are named as: a first receiving matching inductor, a second receiving matching inductor, a third receiving matching inductor, and a fourth receiving matching inductor, wherein the inductance value of the first receiving matching inductor is greater than the inductance value of the second receiving matching inductor, the inductance value of the second receiving matching inductor is greater than the inductance value of the third receiving matching inductor, and the inductance value of the third receiving matching inductor is greater than the inductance value of the fourth receiving matching inductor. Moreover, the difference in inductance value between the first receiving matching inductor and the second receiving matching inductor is ΔL11, the difference in inductance value between the second receiving matching inductor and the third receiving matching inductor is ΔL21, and the difference in inductance value between the third receiving matching inductor and the fourth receiving matching inductor is ΔL31, ΔL11=ΔL21=ΔL31. Thus, in the direction from the signal output port of the photoelectric detector to the radio frequency input end of the radio frequency transmission circuit, the inductance value of the receiving matching inductor can be made to decrease at an equal difference. Moreover, the present application does not limit the specific values of ΔL11, ΔL21, and ΔL31, which can be determined according to the requirements of the actual application scenario.

[0116] In some embodiments of the present application, in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit, the inductance values of the sequentially connected partial or all receiving matching inductors decrease in turn. For example, taking four sequentially connected receiving matching inductors as an example, in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit, the four receiving matching inductors are named as a first receiving matching inductor, a second receiving matching inductor, a third receiving matching inductor and a fourth receiving matching inductor, wherein the inductance value of the first receiving matching inductor is greater than the inductance value of the second receiving matching inductor, the inductance value of the second receiving matching inductor is greater than the inductance value of the third receiving matching inductor, and the inductance value of the third receiving matching inductor is greater than the inductance value of the fourth receiving matching inductor. Moreover, the inductance value difference between the first receiving matching inductor and the second receiving matching inductor is ΔL12, the inductance value difference between the second receiving matching inductor and the third receiving matching inductor is ΔL22, and the inductance value difference between the third receiving matching inductor and the fourth receiving matching inductor is ΔL32, ΔL12>ΔL22>ΔL32. Thus, in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit, the inductance values of the receiving matching inductors decrease based on the inductance value differences decreasing in turn. Moreover, the present application does not limit the specific values of ΔL12, ΔL22 and ΔL32, which can be determined according to the requirements of actual application scenarios.

[0117] In some embodiments of the present application, in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit, the inductance values of the sequentially connected partial or all receiving matching inductors can also be arranged to increase in turn. For example, taking four sequentially connected receiving matching inductors as an example, in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit, the four receiving matching inductors are named as a first receiving matching inductor, a second receiving matching inductor, a third receiving matching inductor and a fourth receiving matching inductor, wherein the inductance value of the first receiving matching inductor is greater than the inductance value of the second receiving matching inductor, the inductance value of the second receiving matching inductor is greater than the inductance value of the third receiving matching inductor, and the inductance value of the third receiving matching inductor is greater than the inductance value of the fourth receiving matching inductor. Moreover, the inductance value difference between the first receiving matching inductor and the second receiving matching inductor is ΔL13, the inductance value difference between the second receiving matching inductor and the third receiving matching inductor is ΔL23, and the inductance value difference between the third receiving matching inductor and the fourth receiving matching inductor is ΔL33, ΔL13<ΔL23<ΔL33. Thus, in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit, the inductance values of the receiving matching inductors can be arranged to decrease based on the increasing difference. In addition, the present application does not limit the specific values of ΔL13, ΔL23 and ΔL33, which can be determined according to the requirements of the actual application scenario.

[0118] It can be understood that the above is only an example to illustrate some embodiments in which the inductance values of the receiving matching inductors decrease in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit. In other embodiments, other rules can also be used to realize the embodiments in which the inductance values of the receiving matching inductors decrease, as long as the above-mentioned inductance values of the receiving matching inductors decrease are met, which belong to the protection scope of the present application, and the specific embodiments are not limited herein.

[0119] In some embodiments of the present application, in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit, the difference between the capacitance values of each adjacent receiving matching capacitor in the sequentially connected partial or all receiving matching capacitors is the same. For example, taking four sequentially connected receiving matching capacitors as an example, in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit, the four receiving matching capacitors are named as: the first receiving matching capacitor, the second receiving matching capacitor, the third receiving matching capacitor and the fourth receiving matching capacitor, wherein the capacitance value of the first receiving matching capacitor is greater than the capacitance value of the second receiving matching capacitor, the capacitance value of the second receiving matching capacitor is greater than the capacitance value of the third receiving matching capacitor, and the capacitance value of the third receiving matching capacitor is greater than the capacitance value of the fourth receiving matching capacitor. Moreover, the difference between the capacitance values of the first receiving matching capacitor and the second receiving matching capacitor is ΔC11, the difference between the capacitance values of the second receiving matching capacitor and the third receiving matching capacitor is ΔC21, and the difference between the capacitance values of the third receiving matching capacitor and the fourth receiving matching capacitor is ΔC31, ΔC11 = ΔC21 = ΔC31. Thus, the difference between the capacitance values of the receiving matching capacitors can be reduced in the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit. In addition, the present application does not limit the specific values of ΔC11, ΔC21 and ΔC31, which can be determined according to the requirements of the actual application scenario.

[0120] In other embodiments of this application, in the direction from the signal output port of the photodetector to the RF input port of the RF transmission circuit, the capacitance difference between adjacent receiving matching capacitors in some or all of the sequentially connected receiving matching capacitors may decrease sequentially. For example, taking four sequentially connected receiving matching capacitors as an example, in the direction from the signal output port of the photodetector to the RF input port of the RF transmission circuit, these four receiving matching capacitors are named: first receiving matching capacitor, second receiving matching capacitor, third receiving matching capacitor, and fourth receiving matching capacitor. The capacitance value of the first receiving matching capacitor is greater than that of the second receiving matching capacitor, the capacitance value of the second receiving matching capacitor is greater than that of the third receiving matching capacitor, and the capacitance value of the third receiving matching capacitor is greater than that of the fourth receiving matching capacitor. Furthermore, the capacitance difference between the first and second receiving matching capacitors is ΔC12, the capacitance difference between the second and third receiving matching capacitors is ΔC22, and the capacitance difference between the third and fourth receiving matching capacitors is ΔC32, where ΔC12 > ΔC22 > ΔC32. Therefore, the capacitance value of the receiving matching capacitor can be reduced based on a successively decreasing difference in the direction from the signal output port of the photodetector to the RF input port of the RF transmission circuit. Furthermore, this application does not limit the specific values ​​of ΔC12, ΔC22, and ΔC32, which can be determined according to the requirements of the actual application scenario.

[0121] In some embodiments of the present application, the capacitance values of the sequentially connected partial or all receiving matching capacitors increase in the direction from the signal output port of the photodetector to the RF input end of the RF transmission circuit. For example, taking four sequentially connected receiving matching capacitors as an example, in the direction from the signal output port of the photodetector to the RF input end of the RF transmission circuit, the four receiving matching capacitors are named as a first receiving matching capacitor, a second receiving matching capacitor, a third receiving matching capacitor, and a fourth receiving matching capacitor. The capacitance value of the first receiving matching capacitor is greater than that of the second receiving matching capacitor, the capacitance value of the second receiving matching capacitor is greater than that of the third receiving matching capacitor, and the capacitance value of the third receiving matching capacitor is greater than that of the fourth receiving matching capacitor. In addition, the capacitance value difference between the first receiving matching capacitor and the second receiving matching capacitor is ΔC13, the capacitance value difference between the second receiving matching capacitor and the third receiving matching capacitor is ΔC23, and the capacitance value difference between the third receiving matching capacitor and the fourth receiving matching capacitor is ΔC33. Thus, the capacitance values of the receiving matching capacitors decrease in the direction from the signal output port of the photodetector to the RF input end of the RF transmission circuit based on the increasing difference. In addition, the present application does not limit the specific values of ΔC13, ΔC23, and ΔC33, which can be determined according to the requirements of the actual application scenario.

[0122] It can be understood that the above is only an example to illustrate some embodiments in which the capacitance values of the receiving matching capacitors decrease in the direction from the signal output port of the photodetector to the RF input end of the RF transmission circuit. In other embodiments, other rules can be used to implement embodiments in which the capacitance values of the receiving matching capacitors decrease, as long as the above-mentioned trend of decreasing capacitance values of the receiving matching capacitors is met, which belongs to the protection scope of the present application, and the specific embodiments are not limited herein.

[0123] As an example, referring to FIG. 7, the plurality of receiving matching inductors includes a first receiving matching inductor Lm1 and a second receiving matching inductor Lm2, and the plurality of receiving matching capacitors includes a first receiving matching capacitor Cm1, a second receiving matching capacitor Cm2, and a third receiving matching capacitor Cm3. The first end of the first receiving matching inductor Lm1 is connected to the first end of the first receiving matching capacitor Cm1 and the signal output port S PDThe second end of the first receiving matching inductor Lm1 is connected with the first end of the second receiving matching inductor Lm2 and the first end of the second receiving matching capacitor Cm2 respectively, the second end of the second receiving matching inductor Lm2 is connected with the first end of the third receiving matching capacitor Cm3 and the radio frequency output port respectively, and the second end of the first receiving matching capacitor Cm1, the second end of the second receiving matching capacitor Cm2 and the second end of the third receiving matching capacitor Cm3 are all connected to the ground input port. Thus, the first lumped element network can be realized by using a simple structure to achieve impedance matching. In addition, the radio frequency output port is used for connecting to the radio frequency input port of the radio frequency transmission circuit.

[0124] The inductance value of the first receiving matching inductor Lm1 is greater than the inductance value of the second receiving matching inductor Lm2. The capacitance value of the first receiving matching capacitor Cm1 is greater than the capacitance value of the second receiving matching capacitor Cm2, and the capacitance value of the second receiving matching capacitor Cm2 is greater than the capacitance value of the third receiving matching capacitor Cm3. Exemplarily, the difference between the capacitance value of the first receiving matching capacitor Cm1 and the capacitance value of the second receiving matching capacitor Cm2 is Δ1, and the difference between the capacitance value of the second receiving matching capacitor Cm2 and the capacitance value of the third receiving matching capacitor Cm3 is Δ2, Δ1 can be equal to Δ2, or Δ1 can be greater than Δ2, or Δ1 can be less than Δ2, which is not limited herein. It can be understood that the example is only used to illustrate the specific structure of the first lumped element network 214, and the specific structure of the first lumped element network 214 is not limited to the above structure provided by the embodiment of the present application, and can also be other structures known by those skilled in the art based on the same concept, which is not limited herein.

[0125] In some embodiments, the receiving optical module 200 of FIG. 7 can further include a third receiving inductor LP3, a first end of the third receiving inductor LP3 is connected to the signal output port S PD The second end of the third receiving inductor LP3 is connected to the power supply input port. Thus, the direct current voltage of the power supply input port can be coupled to the signal output port S PD of the photodetector 211 through the third receiving inductor LP3. In some embodiments, the third receiving inductor LP3 can also be connected to the signal output port S PD of the photodetector 211. In some embodiments, the third receiving inductor LP3 can also block or reduce the amount of radio frequency signals passing through, so that the radio frequency signals can enter the corresponding radio frequency transmission circuit through the first lumped element network 214 as much as possible. In actual application, a small amount of radio frequency signals may

[0126] In some embodiments, the receiving optical module 200 of FIG. 7 can further include a fourth receiving ground capacitor CP4, a first electrode of the fourth receiving ground capacitor CP4 being connected with the first ground port G PD1 A second electrode of the fourth receiving ground capacitor CP4 is used to connect the ground input port. In this way, the first ground port G PD1 is grounded through the fourth receiving ground capacitor CP4. In some embodiments, the fourth receiving ground capacitor CP4 can also block or reduce the amount of radio frequency signals passing through. In actual applications, there can be a small amount of radio frequency signals leaking through the fourth receiving ground capacitor CP4, but the amount of the leaked radio frequency signals is usually small, and the weak leaked radio frequency signals have little effect on the transmission coefficient and noise, which can be ignored.

[0127] In some embodiments, the receiving optical module 200 of FIG. 7 further includes a fifth receiving ground capacitor CP5, a first electrode of the fifth receiving ground capacitor CP5 being connected with the second ground port G PD2 A second electrode of the fifth receiving ground capacitor CP5 is used to connect the ground input port. In this way, the second ground port G PD2 is grounded through the fifth receiving ground capacitor CP5. In some embodiments, the fifth receiving ground capacitor CP5 can also block or reduce the amount of radio frequency signals passing through. In actual applications, there can be a small amount of radio frequency signals leaking through the fifth receiving ground capacitor CP5, but the amount of the leaked radio frequency signals is usually small, and the weak leaked radio frequency signals have little effect on the transmission coefficient and noise, which can be ignored.

[0128] The present application also simulates the structure shown in FIG. 7 with the output impedance of the photodetector 211 being 15+j19.7 ohms and the input impedance of the connected radio frequency transmission circuit being 50 ohms. For the impedance matching requirement of the 4.5 GHz frequency point, by setting the inductance value of the first receiving matching inductor Lm1 to 0.61 nH, the inductance value of the second receiving matching inductor Lm2 to 0.56 nH, the capacitance value of the first receiving matching capacitor Cm1 to 1.2 pF, the capacitance value of the second receiving matching capacitor Cm2 to 0.3 pF, and the capacitance value of the third receiving matching capacitor Cm3 to 0.22 pF, the transmission coefficient of the radio frequency signal in the transmission process can be greater than 0.95, so that the loss of the radio frequency signal in the transmission process can be reduced as much as possible.

[0129] In some embodiments, the specific structure diagram of FIG. 7 can be designed with reference to FIG. 5b, and details are not described here.

[0130] In summary, the embodiment of the present application reduces the loss of the radio frequency signal in the output process in the optical receiving module by using the first ladder conversion plane transmission line or the first lumped element network as the impedance matching device in the optical receiving module. Similarly, in the transmitting optical module, the problem of using resistance for impedance matching and causing the power of the radio frequency signal to be damaged also exists. The structure of the transmitting optical module provided by the embodiment of the present application is described in detail in combination with specific embodiments. It can be understood that the following embodiments are only used to illustrate the specific structure of the transmitting optical module, and the specific structure of the transmitting optical module is not limited to the following structure provided by the embodiment of the present application, but can also be other structures known by those skilled in the art based on the same concept, which is not limited here.

[0131] FIG. 8 is a structure block diagram of a transmitting optical module provided by the embodiment of the present application. Referring to FIG. 8, the transmitting optical module 500 provided by the embodiment of the present application can include a direct modulation laser 511 and a second ladder conversion plane transmission line 512. The radio frequency output end of the corresponding radio frequency transmission circuit 120 is connected to the signal input port S LD of the direct modulation laser 511 through the second ladder conversion plane transmission line 512 for impedance matching. The radio frequency output end of the corresponding radio frequency transmission circuit 120 outputs the radio frequency signal, which is output to the signal input port S LD of the direct modulation laser 511 through the second ladder conversion plane transmission line 512. The direct modulation laser 511 performs photoelectric conversion to convert the radio frequency signal into an optical signal and outputs the optical signal. The direct modulation laser involved in the present application can include a direct modulation semiconductor laser (laser diode, LD).

[0132] In some embodiments of the present application, a direct modulation laser circuit model related to bias voltage, frequency and output optical power can be established based on measured direct current (I)-voltage (V) data, scatter (S) parameter data and output optical power at different bias voltages and different frequencies, so as to accurately characterize the electro-optical conversion process of the direct modulation laser. The direct modulation laser circuit model can include three regions: a direct current parameter region, a chip intrinsic region and a parasitic parameter region. The direct current parameter region includes a current source to represent the direct current parameter characteristics of the direct modulation laser. The chip intrinsic region includes a fifth capacitor and a fifth resistor to represent the junction capacitance of the direct modulation laser by the fifth capacitor (the junction capacitance is a variable capacitance, and the junction capacitance is related to the bias voltage), and to represent the drift resistance of the direct modulation laser by the fifth resistor (the drift resistance is a variable resistance, and the drift resistance is related to the bias voltage). The parasitic parameter region includes a sixth capacitor, a sixth resistor and a third inductor to represent the parasitic resistance of the direct modulation laser by the sixth resistor, to represent the parasitic inductance of the direct modulation laser by the third inductor, and to represent the parasitic capacitance of the direct modulation laser by the sixth capacitor.

[0133] The established laser circuit model is used to simulate a second stepped transformation planar transmission line that meets the requirements of matching a large bandwidth (e.g., 2 GHz to 6 GHz) and a transmission coefficient greater than or equal to 0.9. That is, the second stepped transformation planar transmission line needs to be segmented, and the impedances of adjacent segments need to be designed to be different. Based on this, the second stepped transformation planar transmission line is designed to achieve impedance matching, which can minimize the loss of the radio frequency signal during output. Compared with using a resistor for impedance matching, the loss of the radio frequency signal during output can be effectively reduced, thereby improving the gain of the entire RoF network system, reducing the noise coefficient, and further obtaining a high-performance RoF transmission link.

[0134] In some embodiments, the second stepped transformation planar transmission line 512 can include sequentially connected first transmission line sub-segments to Nth transmission line sub-segments, the first transmission line sub-segment is used to connect the radio frequency output end of the corresponding radio frequency transmission circuit 120, and the Nth transmission line sub-segment is connected to the signal input port S LD In some examples, the transmitting optical module 500 of the present application can be applied to the central side communication device 10 in the scenarios shown in FIGS. 1a and 1b, and the radio frequency transmission circuit 120 connected to the first transmission line sub-segment can be the first radio frequency transmission circuit 12. In yet other examples, the receiving optical module 200 of the present application can be applied to the remote side communication device 20 in the scenario shown in FIG. 1b, and the radio frequency transmission circuit 120 connected to the first transmission line sub-segment can be the second radio frequency transmission circuit 22.

[0135] N can be an integer and N≥3, i.e., the second stepped transformation plane transmission line 512 is divided into at least three sections. In order to match the impedance, and meet the requirements of matching a large bandwidth (e.g., 2 GHz-6 GHz) and a transmission coefficient greater than or equal to 0.9, the impedance of at least one of the second transmission line section to the N-1th transmission line section can be less than the impedance of the Nth transmission line section. Through simulation, it is found that if the impedance of the first transmission line section to the Nth transmission line section is set to decrease in a decreasing trend from large to small, impedance matching can also be achieved, but the bandwidth is usually less than 0.5 GHz when impedance matching is performed using this impedance variation trend, resulting in a narrow matching bandwidth and a greatly limited application range.

[0136] In order to match a larger bandwidth and improve the transmission coefficient, the impedance R Y1 of the first transmission line section can be less than the output impedance R ot of the radio frequency output end of the radio frequency transmission circuit 120 connected thereto, and the difference between the impedance R YN of the Nth transmission line section and the input impedance R LD of the signal input port S SLD of the direct modulation laser 511 is close to zero or equal to zero.

[0137] It can be understood that the difference between the impedance R Y1 of the first transmission line section and the output impedance R ot of the radio frequency output end of the radio frequency transmission circuit 120 connected thereto is close to zero, which means that the difference is between ±ΔR n1 , where ΔR n1 may be equal to 0, or ΔR n1 may not be equal to 0, but a value close to zero, for example, ΔR n1 may be 0.001, -0.01, 0.1, 0.2, 0.3, etc. It can be understood by those skilled in the art that by setting the difference between the impedance R Y1 of the first transmission line section and the output impedance R ot of the radio frequency output end of the radio frequency transmission circuit 120 connected thereto to be close to zero or equal to zero, a large bandwidth, a high transmission coefficient, and low noise can be achieved. Therefore, in some embodiments, those skilled in the art can set the specific value of ΔR n1 according to the requirements of the actual application scenario under the premise of meeting the purpose, which is not limited in this application.

[0138] In addition, the difference between the impedance R YN of the Nth transmission line section and the input impedance R SLD of the signal input port of the direct modulation laser is close to zero, which means that the difference is between ±ΔR n2ΔR n2 may equal 0, or ΔR n2 may not equal 0, but a value close to 0, for example, ΔR n2 may be 0.001, -0.01, 0.1, 0.2, 0.3, etc. Those skilled in the art can understand that when the difference between the impedance R YN of the Nth transmission line subsection and the input impedance R SLD of the signal input port of the direct modulation laser is close to 0 or equal to 0, a large bandwidth, a high transmission coefficient, and low noise can be achieved. Therefore, in some embodiments, those skilled in the art can set the specific value of ΔR n2 according to the needs of the actual application scenario on the premise of meeting the purpose, which is not limited herein. In addition, ΔR n1 and ΔR n2 may be the same or different, which can be determined according to the needs of the actual application scenario, which is not limited herein.

[0139] In some embodiments, N≥5, i.e., the second stepped transformation plane transmission line 512 is divided into at least 5 sections, and the impedance variation law of the 1st transmission line subsection to the Nth transmission line subsection is adjusted, for example, the impedance of each transmission line subsection in the 1st transmission line subsection to the Nth transmission line subsection can be sequentially increased, decreased, increased again, and decreased again, so as to further improve the transmission coefficient on the basis of matching a large bandwidth. Exemplarily, since the 1st transmission line subsection is connected to the corresponding radio frequency transmission circuit 120, in order to compensate for the impedance of the 1st transmission line subsection, the impedance of each transmission line subsection in the 1st transmission line subsection to the cth transmission line subsection connected in sequence can be sequentially increased. Since the Nth transmission line subsection is connected to the signal input port S LD of the direct modulation laser 511, in order to compensate for the impedance of the Nth transmission line subsection, the impedance of each transmission line subsection in the cth transmission line subsection to the dth transmission line subsection connected in sequence can be sequentially decreased, and the impedance of the dth transmission line subsection is decreased to be less than the input impedance R SLD of the direct modulation laser 511. Then, the impedance of each transmission line subsection in the dth transmission line subsection to the e th transmission line subsection connected in sequence can be sequentially increased, and the impedance of the e th transmission line subsection is increased to be greater than the input impedance R SLD of the direct modulation laser 511. Then, the impedance of each transmission line subsection in the e th transmission line subsection to the Nth transmission line subsection connected in sequence can be sequentially decreased.

[0140] In some embodiments, in order to obtain a larger transmission coefficient at certain frequency points (e.g. 2.4 GHz, 5 GHz), c can be set to 2, i.e. the impedance of the second transmission line sub-section is greater than the impedance of the first transmission line sub-section and the impedance of the third transmission line sub-section, or c can also be set to 3, i.e. the impedance of the third transmission line sub-section is greater than the impedance of the second transmission line sub-section and the impedance of the fourth transmission line sub-section, and the impedance of the second transmission line sub-section is greater than the impedance of the first transmission line sub-section. With such settings, the inflection point of the first increase in impedance can be set at the impedance of the second transmission line sub-section or the impedance of the third transmission line sub-section, which can further improve the transmission coefficient at certain frequency points.

[0141] In some embodiments, in order to obtain a larger transmission coefficient at certain frequency points (e.g. 2.4 GHz, 5 GHz), e can be set to N-1, i.e. the impedance of the N-1th transmission line sub-section is greater than the impedance of the Nth transmission line sub-section and the impedance of the N-2th transmission line sub-section, and the impedance of the N-2th transmission line sub-section is less than the impedance of the Nth transmission line sub-section and the impedance of the N-3th transmission line sub-section, or e can also be set to N-2, i.e. the impedance of the N-2th transmission line sub-section is greater than the impedance of the N-1th transmission line sub-section and the impedance of the N-3th transmission line sub-section, and the impedance of the N-1th transmission line sub-section is greater than the impedance of the Nth transmission line sub-section, and the impedance of the N-3th transmission line sub-section is less than the impedance of the Nth transmission line sub-section and the impedance of the N-4th transmission line sub-section. With such settings, the inflection point of the second increase in impedance can be set at the impedance of the N-1th transmission line sub-section or the impedance of the N-2th transmission line sub-section, which can further improve the transmission coefficient at certain frequency points.

[0142] In some embodiments, for a specific number of transmission line sub-sections, a person skilled in the art can select a suitable value based on the needs of performance such as impedance matching, large bandwidth, high transmission coefficient and low noise, as well as considerations such as the size and cost of the light emitting module 500. For example, the specific number of transmission line sub-sections can be set to 3-20. In actual applications, if the number of transmission line sub-sections is too small, the impedance variation trend of the transmission line sub-sections will not be effective. If the number of transmission line sub-sections is too large, the size will be too large, the loss will increase, and the design and processing difficulty will increase, resulting in an increase in cost. Therefore, considering the influence of cost and performance, in some embodiments, 5≤N≤10 is set to balance the influence of cost and performance. For example, N can be 5, 6, 8, 9, 10, etc., which is not limited herein.

[0143] In some embodiments, the second step-transformed planar transmission line 512 can be formed using a step-transformed microstrip line or a step-transformed stripline. For example, when the second step-transformed planar transmission line 512 is configured as a step-transformed microstrip line, the step-transformed microstrip line is divided into a first transmission line segment to an Nth transmission line segment. When the second step-transformed planar transmission line 512 is configured as a step-transformed stripline, the step-transformed stripline is divided into a first transmission line segment to an Nth transmission line segment.

[0144] The following example illustrates the structure of the second step-transformed plane transmission line 512 provided in this application embodiment, using a step-transformed microstrip line to form the second step-transformed plane transmission line 512.

[0145] Figure 9 is a schematic diagram of a second step-change planar transmission line 512, an RF transmission circuit 120, and a directly modulated laser provided in an embodiment of this application. Referring to Figure 9, the second step-change planar transmission line 512 may include a first transmission line segment Ya1 to a sixth transmission line segment Ya6 connected in sequence. The first transmission line segment Ya1 is used to connect to the corresponding RF transmission circuit 120, and the sixth transmission line segment Ya6 is connected to the signal input port S of the directly modulated laser 511. LD Electrical connections can be achieved using soldering or wire bonding, with the first transmission line segment Ya1 to the sixth transmission line segment Ya6 connected in series. Furthermore, the impedances of the first transmission line segment Ya1 to the sixth transmission line segment Ya6 can satisfy the following relationship: R Ya2 >R Ya1 R Ya3 >R Ya2 R Ya4 <R Ya3 R Ya5 >R Ya4 R Ya6 <R Ya5 Furthermore, R Ya4 <R Ya6 Among them, R Ya1 R represents the impedance of the first transmission line segment Ya1. Ya2 R represents the impedance of the second transmission line segment Ya2. Ya3 R represents the impedance of the third transmission line segment Ya3. Ya4 R represents the impedance of the fourth transmission line segment Ya4. Ya5 R represents the impedance of the 5th transmission line segment Ya5. Ya6 This represents the impedance of the 6th transmission line segment Ya6.

[0146] It is understood that the above embodiments are merely examples illustrating the specific structure of the second step transformation plane transmission line 512. In specific implementations, the specific structure of the second step transformation plane transmission line 512 is not limited to the structure provided in the embodiments of the present invention, but may also be other structures known to those skilled in the art based on the same concept. No specific limitations are made here.

[0147] In some embodiments of this application, the second step-conversion plane transmission line 512 and the directly modulated laser 511 can be integrated as independent devices to form a transmitting optical module 500. The transmitting optical module 500 is then mounted or disposed on a circuit board (e.g., a printed circuit board, PCB) with a corresponding radio frequency transmission circuit, so that the transmitting optical module 500 is electrically connected to the corresponding radio frequency transmission circuit. For example, FIG10a is a schematic diagram of a transmitting optical module provided in an embodiment of this application, and FIG10b is a schematic diagram of a transmitting PCB provided in an embodiment of this application. Referring to FIG10a and FIG10b, the transmitting optical module 500 may include: a directly modulated laser 511 and a transmitting PCB, with the second step-conversion plane transmission line 512 disposed on the transmitting PCB. One end of the transmitting PCB is soldered to the directly modulated laser 511, and one end of the transmitting PCB has port components respectively connected to the signal input port, ground port, detection port, and power supply input port of the directly modulated laser 511. The other end of the transmitting PCB is provided with multiple interlocking connectors spaced apart from each other to mount the connectors onto a circuit board with corresponding RF transmission circuits. Specifically, the Nth transmission line segment of the second-step conversion plane transmission line 512 is connected to a port assembly on the transmitting PCB that connects to the signal input port of the directly modulated laser 511, thereby achieving an electrical connection between the Nth transmission line segment and the signal input port of the directly modulated laser 511, as well as an electrical connection between the detection port and other detection circuits. The first transmission line segment of the second-step conversion plane transmission line 512 is connected to the connector (as an RF input port), so that after the transmitting optical module 500 is mounted onto the circuit board with the corresponding RF transmission circuit, an electrical connection can be achieved between the first transmission line segment and the corresponding RF transmission circuit. In some embodiments, a port assembly connecting the signal input port, ground port, detection port, and power supply input port can be inserted into the circuit board to achieve the conduction of DC voltage and ground voltage, as well as the transmission of RF signals. Understandably, the second step-transformation plane transmission line 512 can also be integrated into the direct-modulation laser 511 to improve integration and further achieve miniaturization.

[0148] In some examples, the directly modulated laser 511 may include a directly modulated semiconductor laser (LD). Exemplarily, the directly modulated LD may include a Transmitter Optical Subassembly (TOSA). In practical applications, the connection method between the directly modulated laser 511 and the second step-transform plane transmission line 512 can be designed according to the specific configuration of the directly modulated laser 511. Exemplarily, the connection method includes, but is not limited to, soldering, wire bonding (e.g., gold wire bonding), etc.

[0149] Furthermore, since the directly modulated laser 511 has not only a signal input port but also a ground port, other components are needed in the transmitting optical module 500 to realize the overall function of the directly modulated laser 511. Figure 11 is a schematic diagram of an equivalent circuit structure of the receiving optical module provided in an embodiment of this application. The transmitting optical module 500 may include: a directly modulated laser 511, a second stepped-transformer plane transmission line 512 disposed on the transmitting PCB, a first transmitting component 610, a first transmitting ground capacitor CY1, and a second transmitting ground capacitor CY2. The first end of the first transmitting component 610 is connected to one of the transmission line segments from the first to the Nth transmission line segment, and the second end of the first transmitting component 610 is used to connect to the power supply input port. The first electrode of the first transmitting ground capacitor CY1 is connected to the ground port G of the directly modulated laser 511. LD (For example, a ground input port assembly on the transmitting PCB) is connected, and the second end of the first transmitting ground capacitor CY1 is used to connect to the ground input port (for example, a plug-in assembly on the transmitting PCB connected to the ground input port assembly), so that the ground port of the direct-modulated laser 511 is grounded through the first transmitting ground capacitor CY1. The first electrode of the second transmitting ground capacitor CY2 is connected to the signal input port S of the direct-modulated laser 511. LD (For example, a signal input port assembly on the transmitting PCB) connection, the second end of the second transmitting ground capacitor CY2 is used to connect to the ground input port (for example, a plug-in assembly on the transmitting PCB that is connected to the ground input port assembly).

[0150] The first transmitting component 610 couples the signal from the power supply input port to the transmission line segment connected thereto, thereby enabling the DC voltage input from the power supply input port to be input to the signal input port of the directly modulated laser 511. Furthermore, since the signal input port of the directly modulated laser 511 is used to input radio frequency (RF) signals, to prevent RF signal leakage, the first transmitting component 610 can also block or reduce the passage of RF signals, ensuring that the RF signals enter the signal input port of the directly modulated laser 511 via the second step-transformer plane transmission line 512 as much as possible. Further, to reduce the impact of the first transmitting component 610 on the impedance and RF signal leakage of each transmission line segment in the second step-transformer plane transmission line 512, the first end of the first transmitting component 610 can be connected to the junction between the first and second transmission line segments.

[0151] For example, referring to FIG11, the first transmitting component 610 may include a first transmitting inductor LY1, thereby transmitting DC voltage and blocking radio frequency signals. Alternatively, the first receiving component 310 may also include a third quarter-wavelength transmission line. Of course, in practical applications, the first transmitting component 610 may also be configured with other devices that can achieve the above functions, and this is not limited here. In addition, the purpose of setting the first transmitting component 610 is twofold: to transmit DC voltage and to block radio frequency signals. However, in practical applications, a small amount of radio frequency signal may leak through the first transmitting component 610, but this leakage is usually not large, and its impact on the transmission coefficient and noise is small and negligible.

[0152] It is understood that Figure 10b only illustrates the second step-transformation plane transmission line 512, and does not illustrate the first transmitting component 610, the first transmitting ground capacitor CY1, and the second transmitting ground capacitor CY2. The implementation of the first transmitting component 610, the first transmitting ground capacitor CY1, and the second transmitting ground capacitor CY2 can be determined according to the needs of the actual application scenario, and is not limited here.

[0153] In some embodiments of this application, in addition to using a second-step transformed plane transmission line 512 for impedance matching, a lumped element network formed by capacitors and inductors can also be used for impedance matching. For example, Figure 12 is a schematic diagram of another equivalent circuit structure of the transmitting optical module provided in an embodiment of this application. Referring to Figure 12, this embodiment is a modification of the embodiment shown in Figure 11. The similarities are not repeated here, but the differences are: the transmitting optical module 500 includes a directly modulated laser 511 and a second lumped element network 513, wherein the first end of the second lumped element network 513 is used to connect to the RF output terminal of the corresponding RF transmission circuit 120, and the second end of the second lumped element network 513 is connected to the signal input port S of the directly modulated laser 511. LDThe connection is configured to perform impedance matching via a second lumped element network 513. To reduce losses, the second lumped element network 513 may include multiple emitter matching capacitors (e.g., Cn1 to Cn3) and multiple emitter matching inductors (e.g., Ln1 to Ln3). These emitter matching inductors are connected in series between a first terminal and a second terminal of the second lumped element network 513. At least two ends of some of the emitter matching inductors are connected to the first terminal of an emitter matching capacitor, and the second terminals of the multiple emitter matching capacitors are used to connect to a ground input port. This configuration eliminates the need for resistors for impedance matching, instead using capacitors and inductors, thus reducing losses during RF signal transmission.

[0154] Furthermore, in some embodiments of this application, a circuit model of the directly modulated laser 511 related to the bias voltage, frequency, and output optical power can be established based on actually measured DC current (I)-voltage (V) data, scattering (S) parameter data, and different output optical power at different bias voltages and frequencies, to accurately characterize the electro-optical conversion process of the directly modulated laser 511. The circuit model of the directly modulated laser can include three regions: a DC parameter region, a chip intrinsic region, and a parasitic parameter region. The DC parameter region includes a current source to characterize the DC parameter characteristics of the directly modulated laser. The chip intrinsic region includes a seventh capacitor and a seventh resistor, with the seventh capacitor characterizing the junction capacitance of the directly modulated laser (the junction capacitance is a variable capacitance and is related to the bias voltage), and the seventh resistor characterizing the drift resistance of the directly modulated laser (the drift resistance is a variable resistance and is related to the bias voltage). The parasitic parameter region includes an eighth capacitor, an eighth resistor, and a fourth inductor, with the eighth resistor representing the parasitic resistance of the directly modulated laser, the fourth inductor representing the parasitic inductance of the directly modulated laser, and the eighth capacitor representing the parasitic capacitance of the directly modulated laser.

[0155] Using an established laser circuit model, and based on the requirements of a large matching bandwidth (e.g., 2GHz to 6GHz) and a transmission coefficient greater than or equal to 0.9, simulations were performed to obtain the number of capacitors and inductors that meet the above requirements, as well as the variation patterns of the capacitance and inductance values. Specifically, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the inductance values ​​of the multiple transmitter matching inductors and the capacitance values ​​of the multiple transmitter matching capacitors show an increasing trend. Based on this, the capacitors and inductors in the second lumped element network 513 are designed to achieve impedance matching. This minimizes the loss of the RF signal during output. Compared to impedance matching using resistors, this effectively reduces the loss of the RF signal during output, thereby improving the gain of the entire RoF network system, reducing the noise figure, and ultimately achieving a high-performance RoF transmission link.

[0156] In some embodiments of this application, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the inductance value difference between each adjacent emitter matching inductor in some or all of the sequentially connected emitter matching inductors can be the same. For example, taking four sequentially connected emitter matching inductors as an example, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the four emitter matching inductors are named as: first emitter matching inductor, second emitter matching inductor, third emitter matching inductor, and fourth emitter matching inductor, wherein the inductance value of the second emitter matching inductor is greater than the inductance value of the first emitter matching inductor, the inductance value of the third emitter matching inductor is greater than the inductance value of the second emitter matching inductor, and the inductance value of the fourth emitter matching inductor is greater than the inductance value of the third emitter matching inductor. Furthermore, the inductance difference between the first and second transmitter matching inductors is ΔL14, the inductance difference between the second and third transmitter matching inductors is ΔL24, and the inductance difference between the third and fourth transmitter matching inductors is ΔL34, where ΔL14 = ΔL24 = ΔL34. Therefore, the inductance values ​​of the transmitter matching inductors can be increased by equal differences in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser. Moreover, this application does not limit the specific values ​​of ΔL14, ΔL24, and ΔL34; they can be determined according to the requirements of the actual application scenario.

[0157] In other embodiments of this application, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the inductance difference between each adjacent emitter matching inductor in some or all of the sequentially connected emitter matching inductors may decrease sequentially. For example, taking four sequentially connected emitter matching inductors as an example, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the four emitter matching inductors are named as: first emitter matching inductor, second emitter matching inductor, third emitter matching inductor, and fourth emitter matching inductor, wherein the inductance value of the second emitter matching inductor is greater than the inductance value of the first emitter matching inductor, the inductance value of the third emitter matching inductor is greater than the inductance value of the second emitter matching inductor, and the inductance value of the fourth emitter matching inductor is greater than the inductance value of the third emitter matching inductor. Furthermore, the inductance difference between the first and second transmitter matching inductors is ΔL15, the inductance difference between the second and third transmitter matching inductors is ΔL25, and the inductance difference between the third and fourth transmitter matching inductors is ΔL35, where ΔL15 > ΔL25 > ΔL35. Therefore, the inductance value of the transmitter matching inductors can be increased based on successively decreasing differences in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser. Moreover, this application does not limit the specific values ​​of ΔL15, ΔL25, and ΔL35; they can be determined according to the requirements of the actual application scenario.

[0158] In some embodiments of this application, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the inductance difference between adjacent emitter matching inductors in some or all of the sequentially connected emitter matching inductors may increase sequentially. For example, taking four sequentially connected emitter matching inductors as an example, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the four emitter matching inductors are named as: first emitter matching inductor, second emitter matching inductor, third emitter matching inductor, and fourth emitter matching inductor, wherein the inductance value of the second emitter matching inductor is greater than the inductance value of the first emitter matching inductor, the inductance value of the third emitter matching inductor is greater than the inductance value of the second emitter matching inductor, and the inductance value of the fourth emitter matching inductor is greater than the inductance value of the third emitter matching inductor. Furthermore, the inductance difference between the first and second transmitter matching inductors is ΔL16, the inductance difference between the second and third transmitter matching inductors is ΔL26, and the inductance difference between the third and fourth transmitter matching inductors is ΔL36, where ΔL16 < ΔL26 < ΔL36. Therefore, the inductance value of the transmitter matching inductors can be increased based on these successively increasing differences in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser. Moreover, this application does not limit the specific values ​​of ΔL16, ΔL26, and ΔL36; they can be determined according to the requirements of the actual application scenario.

[0159] It is understood that the above are merely examples illustrating some possible implementations where the inductance value of the transmitter matching inductor increases in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser. In other embodiments, other rules can also be used to achieve the increasing trend of the inductance value of the transmitter matching inductor. As long as the increasing trend of the inductance value of the transmitter matching inductor provided in the embodiments of this application is satisfied, it falls within the protection scope of this application, and is not specifically limited here.

[0160] In some embodiments of this application, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the capacitance difference between adjacent emitter matching capacitors in some or all of the sequentially connected emitter matching capacitors can be the same. For example, taking four sequentially connected emitter matching capacitors as an example, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, these four emitter matching capacitors are named: first emitter matching capacitor, second emitter matching capacitor, third emitter matching capacitor, and fourth emitter matching capacitor. The capacitance value of the second emitter matching capacitor is greater than that of the first emitter matching capacitor, the capacitance value of the third emitter matching capacitor is greater than that of the second emitter matching capacitor, and the capacitance value of the fourth emitter matching capacitor is greater than that of the third emitter matching capacitor. Furthermore, the capacitance difference between the first and second emitter matching capacitors is ΔC14, the capacitance difference between the second and third emitter matching capacitors is ΔC24, and the capacitance difference between the third and fourth emitter matching capacitors is ΔC34, where ΔC14 = ΔC24 = ΔC34. Therefore, the capacitance value of the emitter matching capacitor can be increased differentially in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser. Furthermore, this application does not limit the specific values ​​of ΔC14, ΔC24, and ΔC34, which can be determined according to the requirements of the actual application scenario.

[0161] In other embodiments of this application, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the capacitance difference between adjacent emitter matching capacitors in some or all of the sequentially connected emitter matching capacitors may decrease sequentially. For example, taking four sequentially connected emitter matching capacitors as an example, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, these four emitter matching capacitors are named: first emitter matching capacitor, second emitter matching capacitor, third emitter matching capacitor, and fourth emitter matching capacitor. The capacitance value of the second emitter matching capacitor is greater than that of the first emitter matching capacitor, the capacitance value of the third emitter matching capacitor is greater than that of the second emitter matching capacitor, and the capacitance value of the fourth emitter matching capacitor is greater than that of the third emitter matching capacitor. Furthermore, the capacitance difference between the first and second emitter matching capacitors is ΔC15, the capacitance difference between the second and third emitter matching capacitors is ΔC25, and the capacitance difference between the third and fourth emitter matching capacitors is ΔC35, where ΔC15 > ΔC25 > ΔC35. Therefore, the capacitance value of the emitter matching capacitor can be increased based on a successively decreasing difference in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser. Furthermore, this application does not limit the specific values ​​of ΔC15, ΔC25, and ΔC35, which can be determined according to the requirements of the actual application scenario.

[0162] In some embodiments of this application, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, the capacitance difference between adjacent emitter matching capacitors in some or all of the sequentially connected emitter matching capacitors can be made to increase sequentially. For example, taking four sequentially connected emitter matching capacitors as an example, in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser, these four emitter matching capacitors are named: first emitter matching capacitor, second emitter matching capacitor, third emitter matching capacitor, and fourth emitter matching capacitor. The capacitance value of the second emitter matching capacitor is greater than that of the first emitter matching capacitor, the capacitance value of the third emitter matching capacitor is greater than that of the second emitter matching capacitor, and the capacitance value of the fourth emitter matching capacitor is greater than that of the third emitter matching capacitor. Furthermore, the capacitance difference between the first and second emitter matching capacitors is ΔC16, the capacitance difference between the second and third emitter matching capacitors is ΔC26, and the capacitance difference between the third and fourth emitter matching capacitors is ΔC36, where ΔC16 < ΔC26 < ΔC36. Therefore, the capacitance value of the emitter matching capacitor can be increased based on a sequentially increasing difference in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser. Furthermore, this application does not limit the specific values ​​of ΔC16, ΔC26, and ΔC36, which can be determined according to the requirements of the actual application scenario.

[0163] It is understood that the above are merely examples illustrating some possible implementations where the capacitance value of the transmitter matching capacitor increases in the direction from the RF output terminal of the RF transmission circuit to the signal input port of the directly modulated laser. In other embodiments, other rules can also be used to achieve the increasing capacitance value of the transmitter matching capacitor. As long as the increasing capacitance value of the transmitter matching capacitor provided in the embodiments of this application is satisfied, it falls within the protection scope of this application, and is not specifically limited here.

[0164] As an example, referring to Figure 12, the plurality of emitter matching inductors include a first emitter matching inductor Ln1, a second emitter matching inductor Ln2, and a third emitter matching inductor Ln3, and the plurality of emitter matching capacitors include a first emitter matching capacitor Cn1, a second emitter matching capacitor Cn2, and a third emitter matching capacitor Cn3. The first terminal of the first emitter matching inductor Ln1 is connected to the first terminal of the first emitter matching capacitor Cn1 and the RF input port, respectively. The second terminal of the first emitter matching inductor Ln1 is connected to the first terminal of the second emitter matching inductor Ln2 and the first terminal of the second emitter matching capacitor Cn2, respectively. The second terminal of the second emitter matching inductor Ln2 is interconnected with the first terminal of the third emitter matching inductor Ln3 and the first terminal of the third emitter matching capacitor Cn3. The second terminal of the third emitter matching inductor Ln3 is connected to the signal input port S of the direct-modulated laser 511. LD The second terminals of the first emitter matching capacitor Cn1, the second emitter matching capacitor Cn2, and the third emitter matching capacitor Cn3 are all connected to the ground input port. This configuration allows for a simple implementation of the second lumped-element network to achieve impedance matching. Furthermore, the RF input port is used to connect to the RF output of the RF transmission circuit.

[0165] The inductance value of the first transmitter matching inductor Ln1 is less than the inductance value of the second transmitter matching inductor Ln2, and the inductance value of the second transmitter matching inductor Ln2 is less than the inductance value of the third transmitter matching inductor Ln3. For example, the difference between the capacitance values ​​of the first transmitter matching inductor Ln1 and the second transmitter matching inductor Ln2 is Δ3, and the difference between the capacitance values ​​of the second transmitter matching inductor Ln2 and the third transmitter matching inductor Ln3 is Δ4. Δ3 and Δ4 can be equal, or Δ3 can be greater than Δ4, or Δ3 can be less than Δ4; this is not limited here.

[0166] The capacitance value of the first emitter matching capacitor Cn1 is less than the capacitance value of the second emitter matching capacitor Cn2, and the capacitance value of the second emitter matching capacitor Cn2 is less than the capacitance value of the third emitter matching capacitor Cn3. For example, the difference between the capacitance values ​​of the first emitter matching capacitor Cn1 and the second emitter matching capacitor Cn2 is Δ5, and the difference between the capacitance values ​​of the second emitter matching capacitor Cn2 and the third emitter matching capacitor Cn3 is Δ6. Δ5 and Δ6 can be equal, or Δ5 can be greater than Δ6, or Δ5 can be less than Δ6; this is not limited here.

[0167] It is understood that this example is only to illustrate the specific structure of the second lumped element network 513. In specific implementation, the specific structure of the second lumped element network 513 is not limited to the structure provided in the embodiments of the present invention, and may also be other structures known to those skilled in the art based on the same concept. No specific limitation is made here.

[0168] In some embodiments, the emitting optical module 500 of FIG12 may further include a second emitting inductor LY2, the first end of the second emitting inductor LY2 being connected to the signal input port S of the direct-modulated laser 511. LD The second end of the second transmitting inductor LY2 is connected to the power supply input port. This configuration allows the DC voltage from the power supply input port to be coupled to the signal input port of the directly modulated laser 511 via the second transmitting inductor LY2, thus providing the signal input port S of the directly modulated laser 511. LD Power supply. In some embodiments, the second transmitting inductor LY2 can also be used to block or reduce the amount of radio frequency signal passing through, so that the radio frequency signal enters the direct-modulated laser 511 through the second lumped element network 513 as much as possible. In practical applications, a small amount of radio frequency signal may leak through the second transmitting inductor LY2, but the amount of leaked radio frequency signal is weak, and the weak leakage of radio frequency signal has little impact on the transmission coefficient and noise, and can be ignored.

[0169] In some embodiments, the emitting optical module 500 of FIG12 may further include a third emitting ground capacitor CY3, the first electrode of the third emitting ground capacitor CY3 being connected to the ground port G of the direct-modulated laser 511. LD The second terminal of the third transmitting ground capacitor CY3 is used to connect to the ground input port. This allows the ground port G of the direct-modulated laser 511 to be connected. LD Grounding is achieved through the third transmit grounding capacitor CY3. In some embodiments, the third transmit grounding capacitor CY3 can also be used to block or reduce the amount of radio frequency signal passing through. In practical applications, a small amount of radio frequency signal may leak through the third transmit grounding capacitor CY3, but the amount of leaked radio frequency signal is usually small, and the weak leaked radio frequency signal has a negligible impact on the transmission coefficient and noise.

[0170] In some embodiments, the emitting optical module 500 of FIG12 may also include a fourth emitting ground capacitor CY4. The first electrode of the fourth emitting ground capacitor CY4 is connected to the ground port of the direct-modulated laser 511, and the second end of the fourth emitting ground capacitor CY4 is used to connect to the ground input port. In some other embodiments of this application, if the performance of the emitting optical module 500 meets the requirements, the fourth emitting ground capacitor CY4 may be removed to reduce the number of capacitor components.

[0171] This application also takes the input impedance of the directly modulated laser 511 as 9.492-j14.9 ohms and the output impedance of the corresponding connected RF transmission circuit as 50 ohms as an example, and performs simulation with the structure shown in Figure 12. For the impedance matching requirement at the 2.7GHz frequency point, by setting the inductance value of the first transmitter matching inductor Ln1 to 1.12nH, the inductance value of the second transmitter matching inductor Ln2 to 1.14nH, the inductance value of the third transmitter matching inductor Ln3 to 1.66nH, the capacitance value of the first transmitter matching capacitor Cn1 to 0.56pF, the capacitance value of the second transmitter matching capacitor Cn2 to 0.97pF, and the capacitance value of the third transmitter matching capacitor Cn3 to 2.97pF, the transmission coefficient of the RF signal during transmission can be greater than 0.95, thereby minimizing the loss of the RF signal during transmission.

[0172] In some embodiments, the specific structural schematic diagram corresponding to FIG12 can be designed with reference to the structures shown in FIG10a to FIG11, and the details will not be elaborated here.

[0173] The optical module described in this application embodiment can be used in various devices, such as servers, routing devices, switching devices, or other communication devices.

[0174] The above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application.

Claims

1. A receiving optical module, characterized in that, The application relates to a receiving optical module. The receiving optical module comprises a photoelectric detector and a first stepped transformation planar transmission line, the first stepped transformation planar transmission line comprises sequentially connected first transmission line subsegments to Mth transmission line subsegments, the first transmission line subsegment is connected with a signal output port of the photoelectric detector, and the Mth transmission line subsegment is used for connecting a radio frequency input end of a radio frequency transmission circuit; M is an integer and M>=3; Impedances of at least one of the second transmission line subsegment to the M-1th transmission line subsegment are less than the impedance of the first transmission line subsegment.

2. The receiving optical module according to claim 1, wherein M>=4, the impedance of each of the first transmission line subsegment to the Mth transmission line subsegment is sequentially reduced, increased and then reduced again.

3. The receiving optical module according to claim 2, wherein The impedance of each of the first transmission line subsegment to the Mth transmission line subsegment is sequentially reduced, then sequentially increased to be greater than the impedance of the Mth transmission line subsegment, and finally sequentially reduced to the impedance of the Mth transmission line subsegment.

4. The receiving optical module according to claim 2 or 3, wherein The impedance of the second transmission line subsegment is less than the impedance of the first transmission line subsegment and the impedance of the third transmission line subsegment; Or, the impedance of the third transmission line subsegment is less than the impedance of the second transmission line subsegment and the impedance of the fourth transmission line subsegment, and the impedance of the second transmission line subsegment is less than the impedance of the first transmission line subsegment; Or, the impedance of the M-1th transmission line subsegment is greater than the impedance of the Mth transmission line subsegment and the impedance of the M-2th transmission line subsegment; Or, the impedance of the M-2th transmission line subsegment is greater than the impedance of the M-1th transmission line subsegment and the impedance of the M-3th transmission line subsegment, and the impedance of the M-1th transmission line subsegment is greater than the impedance of the Mth transmission line subsegment.

5. The receiving optical module according to any one of claims 2 to 4, wherein 4≤M≤10； Or, the difference between the impedance of the first transmission line subsegment and the output impedance of the signal output port of the photoelectric detector is close to zero or equal to zero, and the difference between the impedance of the Mth transmission line subsegment and the input impedance of the radio frequency input end of the radio frequency transmission circuit is close to zero or equal to zero; Or, the first stepped transformation planar transmission line comprises a stepped transformation microstrip line or a stepped transformation strip line.

6. The receiving optical module according to any one of claims 1 to 5, wherein The receiving optical module further comprises a first receiving component, a first end of the first receiving component is connected with one of the first transmission line subsegment to the Mth transmission line subsegment, and a second end of the first receiving component is used for connecting a power supply input port or a grounding input port; The first receiving component is used for coupling a signal of the power supply input port or the grounding input port to the transmission line subsegment connected with the first receiving component and blocking a radio frequency signal.

7. The receiving optical module according to claim 6, wherein The first end of the first receiving component is connected to a connection between the first transmission line subsegment and the second transmission line subsegment; or The first receiving component comprises a first quarter wavelength transmission line or a first receiving inductance.

8. The receiving optical module according to claim 6 or 7, wherein When the second end of the first receiving component is used for connecting the grounding input port, the receiving optical module further comprises a first receiving grounding capacitor and a second receiving component. The first electrode of the first receiving ground capacitor is connected to the first ground port of the photodetector, and the second electrode of the first receiving ground capacitor is used to connect the ground input port. The first receiving ground capacitor and the second receiving component are used to couple signals of the power supply input port to the first ground port of the photodetector, and the second receiving component is also used to block radio frequency signals.

9. The receiving optical module according to claim 8, wherein The second receiving component includes a second quarter-wavelength transmission line or a second receiving inductor.

10. The receiving optical module according to claim 6 or 7, wherein The second end of the first receiving component is used to connect the power supply input port, and the receiving optical module further includes a second receiving ground capacitor. The first electrode of the second receiving ground capacitor is connected to the first ground port of the photodetector, and the second electrode of the second receiving ground capacitor is used to connect the ground input port.

11. The receiving optical module according to any one of claims 1 to 10, wherein The receiving optical module further includes a third receiving ground capacitor, the first electrode of the third receiving ground capacitor is connected to the second ground port of the photodetector, and the second electrode of the third receiving ground capacitor is used to connect the ground input port.

12. A receiving optical module characterized by comprising: It includes: a photodetector and a first network of lumped elements; The first end of the first network of lumped elements is connected to the signal output port of the photodetector, and the second end of the first network of lumped elements is used to connect the radio frequency input end of the radio frequency transmission circuit; The first network of lumped elements includes a plurality of receiving matching capacitors and a plurality of receiving matching inductors, the plurality of receiving matching inductors are connected in series between the signal output port of the photodetector and the radio frequency input end of the radio frequency transmission circuit, and the two ends of at least part of the receiving matching inductors are connected to the first end of one of the receiving matching capacitors, and the second end of the plurality of receiving matching capacitors is used to connect the ground input port. In the direction from the signal output port of the photodetector to the radio frequency input end of the radio frequency transmission circuit, the inductance values of the plurality of receiving matching inductors show a decreasing trend, and the capacitance values of the plurality of receiving matching capacitors show a decreasing trend.

13. The receiving optical module of claim 12, wherein, The plurality of receiving matching inductors includes a first receiving matching inductor and a second receiving matching inductor, and the plurality of receiving matching capacitors includes a first receiving matching capacitor, a second receiving matching capacitor, and a third receiving matching capacitor. The first end of the first receiving matching inductor is connected to the first end of the first receiving matching capacitor and the signal output port of the photodetector, respectively, the second end of the first receiving matching inductor is connected to the first end of the second receiving matching inductor and the first end of the second receiving matching capacitor, respectively, the second end of the second receiving matching inductor is connected to the first end of the third receiving matching capacitor and the radio frequency input end of the radio frequency transmission circuit, respectively, and the second end of the first receiving matching capacitor, the second end of the second receiving matching capacitor, and the second end of the third receiving matching capacitor are all connected to the ground input port.

14. The receiving optical module according to claim 12 or 13, wherein The receiving optical module further comprises a third receiving inductor, a first end of the third receiving inductor is connected with a signal output port of the photodetector, and a second end of the third receiving inductor is used for connecting a power supply input port.

15. The receiving optical module according to any one of claims 13 to 14, wherein The receiving optical module further comprises a fourth receiving ground capacitor, a first electrode of the fourth receiving ground capacitor is connected with a first ground port of the photodetector, and a second electrode of the fourth receiving ground capacitor is used for connecting a ground input port; or, The receiving optical module further comprises a fifth receiving ground capacitor, a first electrode of the fifth receiving ground capacitor is connected with a second ground port of the photodetector, and a second electrode of the fifth receiving ground capacitor is used for connecting a ground input port.

16. An optical transmitting module, comprising: Comprise: A direct modulation laser and a second step transformation planar transmission line, the second step transformation planar transmission line comprises sequentially connected first to Nth transmission line subsegments, the first transmission line subsegment is used for connecting a radio frequency output end of a radio frequency transmission circuit, and the Nth transmission line subsegment is connected with a signal input port of the direct modulation laser; N is an integer and N≥3; Impedances of at least one of the second to N-1th transmission line subsegments are less than an impedance of the Nth transmission line subsegment.

17. The light emitting module of claim 16, wherein, N≥5, the impedance of each of the first to Nth transmission line subsegments is sequentially increased, decreased, increased again, and decreased again.

18. The light emitting module of claim 17, wherein, The impedance of each of the first to Nth transmission line subsegments is sequentially increased and then sequentially decreased to be less than the impedance of the Nth transmission line subsegment, then sequentially increased to be greater than the impedance of the Nth transmission line subsegment, and finally sequentially decreased to the impedance of the Nth transmission line subsegment.

19. The light emitting module of claim 17 or 18, wherein, The impedance of the second transmission line subsegment is greater than the impedance of the first transmission line subsegment and the impedance of the third transmission line subsegment; Or, the impedance of the third transmission line subsegment is greater than the impedance of the second transmission line subsegment and the impedance of the fourth transmission line subsegment, and the impedance of the second transmission line subsegment is greater than the impedance of the first transmission line subsegment; Or, the impedance of the N-1th transmission line subsegment is greater than the impedance of the Nth transmission line subsegment and the impedance of the N-2th transmission line subsegment, and the impedance of the N-2th transmission line subsegment is less than the impedance of the Nth transmission line subsegment and the impedance of the N-3th transmission line subsegment; Or, the impedance of the N-2th transmission line subsegment is greater than the impedance of the N-1th transmission line subsegment and the impedance of the N-3th transmission line subsegment, the impedance of the N-1th transmission line subsegment is greater than the impedance of the Nth transmission line subsegment, and the impedance of the N-3th transmission line subsegment is less than the impedance of the Nth transmission line subsegment and the impedance of the N-4th transmission line subsegment.

20. The light emitting module of any of claims 16-19, wherein, 5≤N≤10； Or, a difference between the impedance of the first transmission line subsegment and an output impedance of the radio frequency output end of the radio frequency transmission circuit is close to zero or equal to zero, and a difference between the impedance of the Nth transmission line subsegment and an input impedance of the signal input port of the direct modulation laser is close to zero or equal to zero; Or, the second step transformation planar transmission line comprises a step transformation microstrip line or a step transformation stripline.

21. The light emitting module of any of claims 16-20, wherein, The transmitting optical module further comprises a first transmitting component, a first end of the first transmitting component is connected with one of the first transmission line sub-section and the Nth transmission line sub-section, and a second end of the first transmitting component is used for connecting a power supply input port; The second receiving component is used for coupling a signal of the power supply input port to the transmission line sub-section connected therewith and blocking a radio frequency signal from passing through.

22. The light emitting module of claim 21, wherein, The first end of the first transmitting component is connected to a connection between the first transmission line sub-section and the second transmission line sub-section; or, The first transmitting component comprises a third quarter wavelength transmission line or a first transmitting inductance.

23. The light emitting module of any of claims 16-22, wherein, The transmitting optical module further comprises a first transmitting ground capacitor, a first electrode of the first transmitting ground capacitor is connected with a ground port of the direct modulation laser, and a second end of the first transmitting ground capacitor is used for connecting a ground input port; Alternatively, the transmitting optical module further comprises a second transmitting ground capacitor, a first electrode of the second transmitting ground capacitor is connected with a signal input port of the direct modulation laser, and a second end of the second transmitting ground capacitor is used for connecting a ground input port.

24. An optical transmitting module, comprising: Comprise: a direct modulation laser and a second lumped element network, a first end of the second lumped element network is used for connecting a radio frequency output of a radio frequency transmission circuit, and a second end of the second lumped element network is connected with a signal input port of the direct modulation laser; The second lumped element network comprises a plurality of transmitting matching capacitors and a plurality of transmitting matching inductances, the plurality of transmitting matching inductances are connected in series between the radio frequency output of the radio frequency transmission circuit and the signal input port of the direct modulation laser in sequence, two ends of at least part of the transmitting matching inductances are connected with a first end of one of the transmitting matching capacitors in one-to-one correspondence, and second ends of the plurality of transmitting matching capacitors are used for connecting a ground input port; In a direction from the radio frequency output of the radio frequency transmission circuit to the signal input port of the direct modulation laser, inductance values of the plurality of transmitting matching inductances show an increasing trend, and capacitance values of the plurality of transmitting matching capacitors show an increasing trend.

25. The light emitting module of claim 24, wherein, The plurality of transmitting matching inductances comprise a first transmitting matching inductance, a second transmitting matching inductance and a third transmitting matching inductance, and the plurality of transmitting matching capacitors comprise a first transmitting matching capacitor, a second transmitting matching capacitor and a third transmitting matching capacitor; A first end of the first transmitting matching inductance is connected with a first end of the first transmitting matching capacitor and the radio frequency output of the radio frequency transmission circuit respectively, a second end of the first transmitting matching inductance is connected with a first end of the second transmitting matching inductance and a first end of the second transmitting matching capacitor respectively, a second end of the second transmitting matching inductance and a first end of the third transmitting matching inductance are connected with each other, a second end of the third transmitting matching inductance is connected with the signal input port of the direct modulation laser, and second ends of the first transmitting matching capacitor, the second transmitting matching capacitor and the third transmitting matching capacitor are used for connecting the ground input port.

26. The light emitting module of claim 24 or 25, wherein, The transmitting optical module further comprises a second transmitting inductor, a first end of the second transmitting inductor is connected with the signal input port of the direct modulation laser, and a second end of the second transmitting inductor is used for connecting the power input port; Alternatively, the transmitting optical module further comprises a third transmitting ground capacitor, a first electrode of the third transmitting ground capacitor is connected with the ground port of the direct modulation laser, and a second end of the third transmitting ground capacitor is used for connecting the ground input port; Alternatively, the transmitting optical module further comprises a fourth transmitting ground capacitor, a first electrode of the fourth transmitting ground capacitor is connected with the ground port of the direct modulation laser, and a second end of the fourth transmitting ground capacitor is used for connecting the ground input port.

27. A transceiver optical module characterized by comprising: Comprise: one or more receiving optical modules according to any one of claims 1-15, and one or more transmitting optical modules according to any one of claims 16-26.

28. An electronic device, comprising: Comprise: a receiving optical module according to any one of claims 1-15, or a transmitting optical module according to any one of claims 16-26, or a transceiving optical module according to claim 27.

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