Patent Publication Number: US-2022224073-A1

Title: Optical module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of International Application No. PCT/CN2021/080967 filed on Mar. 16, 2021, which claims priority to Chinese Patent Application No. 202010406778.8 filed on May 14, 2020, which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the field of optical communication technologies, and in particular, to an optical module. 
     BACKGROUND 
     Due to the higher and higher requirements for communication bandwidth in the field of optical fiber communication, global optical communication is in a period of rapid development. In the field of high-speed data communication, in order to ensure data transmission for a long distance at a high speed, an optical module is generally used to transmit and receive light of different wavelengths in the field. 
     SUMMARY 
     An optical module is provided. The optical module includes a circuit board and a light emitting assembly. The circuit board includes a first circuit board ground line, a second circuit board ground line and a circuit board signal line. The light emitting assembly is connected to the circuit board, and the light emitting assembly includes a spacer and a laser chip. The spacer includes a first spacer ground line, a second spacer ground line and a spacer signal line. The first spacer ground line is connected to the first circuit board ground line through a first connection line, the spacer signal line is connected to the circuit board signal line through a second connection line, and the second spacer ground line is connected to the second circuit board ground line through a third connection line. The laser chip is disposed on the spacer and configured to emit an optical signal based on an electrical signal from the circuit board. An anode of the laser chip is electrically connected to the spacer signal line, and a cathode of the laser chip is electrically connected to the first spacer ground line or the second spacer ground line. Connection relationships among the first spacer ground line, the second spacer ground line, the first circuit board ground line and the second circuit board ground line include at least one of the followings: the first spacer ground line is connected to the second spacer ground line through a fourth connection line; the first spacer ground line is connected to the second circuit board ground line through a fifth connection line; the second spacer ground line is connected to the first circuit board ground line through a sixth connection line; or, the first circuit board ground line is connected to the second circuit board ground line through a seventh connection line. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe technical solutions in the present disclosure more clearly, accompanying drawings to be used in some embodiments of the present disclosure will be introduced briefly below. However, the accompanying drawings to be described below are merely accompanying drawings of some embodiments of the present disclosure, and a person of ordinary skill in the art may obtain other drawings according to these drawings. In addition, the accompanying drawings to be described below may be regarded as schematic diagrams, and are not limitations on actual sizes of products, actual processes of methods and actual timings of signals to which the embodiments of the present disclosure relate. 
         FIG. 1  is a diagram showing a connection relationship of an optical communication system, in accordance with some embodiments; 
         FIG. 2  is a diagram showing a structure of an optical network terminal, in accordance with some embodiments; 
         FIG. 3  is a diagram showing a structure of an optical module, in accordance with some embodiments; 
         FIG. 4  is a diagram showing an exploded structure of an optical module, in accordance with some embodiments; 
         FIG. 5  is a diagram showing structures of a light emitting assembly and a circuit board, in accordance with some embodiments; 
         FIG. 6  is a diagram showing an exploded structure of a light emitting assembly, in accordance with some embodiments; 
         FIG. 7  is a diagram showing a structure of a spacer, in accordance with some embodiments; 
         FIG. 8  is a diagram showing a connection manner between a circuit board and a light emitting assembly, in accordance with some embodiments; 
         FIG. 9  is a partial structural diagram of a circuit board and a light emitting assembly, in accordance with some embodiments; 
         FIG. 10  is a partial side view of a circuit board and a spacer, in accordance with some embodiments; and 
         FIG. 11  is a partial structural diagram of a circuit board and a spacer, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The technical solutions in the embodiments of the present disclosure will be described below clearly and completely with reference to the accompanying drawings in the embodiments of the present disclosure. However, the described embodiments are merely some but not all of embodiments of the present disclosure. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present disclosure shall be included in the protection scope of the present disclosure. 
     Unless the context requires otherwise, throughout the specification and the claims, the term “comprise” and other forms thereof such as the third-person singular form “comprises” and the present participle form “comprising” are construed as being open and inclusive, i.e., “including, but not limited to”. In the description, the terms such as “one embodiment”, “some embodiments”, “exemplary embodiments”, “example”, “specific example” or “some examples” are intended to indicate that specific features, structures, materials, or characteristics related to the embodiment(s) or example(s) are included in at least one embodiment or example of the present disclosure. Schematic representations of the above terms do not necessarily refer to the same embodiment(s) or example(s). In addition, the specific features, structures, materials, or characteristics described herein may be included in any one or more embodiments or examples in any suitable manner. 
     Hereinafter, the terms “first” and “second” are only used for descriptive purposes, and cannot be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, features defined as “first” and “second” may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, the term “a plurality of” means two or more unless otherwise specified. 
     In the description of some embodiments, the term “coupled” and “connected” and their extensions may be used. For example, the term “connected” may be used in the description of some embodiments to indicate that two or more components are in direct physical or electrical contact with each other. For another example, the term “coupled” may be used in the description of some embodiments to indicate that two or more components are in direct physical or electrical contact. However, the term “coupled” or “communicatively coupled” may also mean that two or more components are not in direct contact with each other, but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the contents herein. 
     The phrase “at least one of A, B and C” has a same meaning as the phrase “at least one of A, B or C”, and they both include the following combinations of A, B and C: only A, only B, only C, a combination of A and B, a combination of A and C, a combination of B and C, and a combination of A, B and C. 
     The phrase “A and/or B” includes the following three combinations: only A, only B, and a combination of A and B. 
     The use of the phrase “applicable to” or “configured to” herein means an open and inclusive language, which does not exclude devices that are applicable to or configured to perform additional tasks or steps. 
     The term “about”, “substantially” or “approximately” as used herein includes a stated value and an average value within an acceptable range of deviation of a particular value. The acceptable range of deviation is determined by a person of ordinary skill in the art, considering measurement in question and errors associated with measurement of a particular quantity (i.e., limitations of a measurement system). 
     The term such as “parallel”, “perpendicular” or “equal” as used herein includes a stated condition and a condition similar to the stated condition. A range of the similar condition is within an acceptable range of deviation. The acceptable range of deviation is determined by a person of ordinary skill in the art, considering measurement in question and errors associated with measurement of a particular quantity (i.e., limitations of a measurement system). For example, the term “parallel” includes absolute parallelism and approximate parallelism, and an acceptable range of deviation of the approximate parallelism may be, for example, a deviation within 5°; the term “perpendicular” includes absolute perpendicularity and approximate perpendicularity, and an acceptable range of deviation of the approximate perpendicularity may also be, for example, a deviation within 5°. The term “equal” includes absolute equality and approximate equality, and an acceptable range of deviation of the approximate equality may be, for example, a difference between two equals of less than or equal to 5% of either of the two equals. 
     It will be understood that when a layer or element is referred to as being on another layer or substrate, the layer or element can be directly on another layer or substrate, or there is intermediate layer(s) between the layer or element and another layer or substrate. 
     In optical communication technology, an optical signal is used to carry information to be transmitted, and the optical signal carrying the information is transmitted to an information processing device such as a computer through an information transmission device such as an optical fiber or an optical waveguide, so as to achieve information transmission. Due to the passive transmission characteristic of the optical signal when being transmitted through the optical fiber or the optical waveguide, low-cost and low-loss information transmission may be achieved. In addition, since a signal transmitted by the information transmission device such as the optical fiber or the optical waveguide is an optical signal, and a signal that may be recognized and processed by the information processing device such as a computer is an electrical signal, in order to establish information connection between the information transmission device such as the optical fiber or the optical waveguide and the information processing device such as the computer, there is a need to achieve interconversion between the electrical signal and the optical signal. 
     In the field of optical fiber communication technology, an optical may achieve interconversion between the optical signal and the electrical signal. The optical module includes an optical port and an electrical port. The optical module achieves optical communication with the information transmission device such as the optical fiber or the optical waveguide through the optical port, and the optical module achieves electrical connection to an optical network terminal (e.g., an optical modem) through the electrical port. The electrical connection is mainly to implement power supply,  120  signal transmission, data signal transmission, and grounding functions. The optical network terminal transmits the electrical signal to the information processing device such as a computer through a network cable or wireless fidelity (Wi-Fi). 
       FIG. 1  is a diagram showing a connection relationship of an optical communication system, in accordance with some embodiments. As shown in  FIG. 1 , an optical communication system includes a remote server  1000 , a local information processing device  2000 , an optical network terminal  100 , an optical module  200 , an optical fiber  101  and a network cable  103 . 
     An end of the optical fiber  101  is connected to the remote server  1000 , and another end thereof is connected to the optical network terminal  100  through the optical module  200 . The optical fiber itself supports long-distance signal transmission, for example, signal transmission over several kilometers (6 kilometers to 8 kilometers). On this basis, if repeaters are used, theoretically, it may be possible to achieve infinite-distance transmission. Therefore, in a typical optical communication system, a distance between the remote server  1000  and the optical network terminal  100  may typically reach several kilometers, dozens of kilometers, or hundreds of kilometers. 
     An end of the network cable  103  is connected to the local information processing device  2000 , and another end thereof is connected to the optical network terminal  100 . The local information processing device  2000  includes one or more of a router, a switch, a computer, a mobile phone, a tablet computer or a television. 
     A physical distance between the remote server  1000  and the optical network terminal  100  is greater than a physical distance between the local information processing device  2000  and the optical network terminal  100 . Connection between the local information processing device  2000  and the remote server  1000  is achieved by the optical fiber  101  and the network cable  103 , and connection between the optical fiber  101  and the network cable  103  is achieved by the optical module  200  and the optical network terminal  100 . 
     The optical module  200  includes an optical port and an electrical port. The optical port is configured for connecting the optical fiber  101 , so that a bidirectional optical signal connection between the optical module  200  and the optical fiber  101  is established. The electrical port is configured for connecting the optical network terminal  100 , so that a bidirectional electrical signal connection is established between the optical module  200  and the optical network terminal  100 . The optical module  200  may achieve interconversion between the optical signal and the electrical signal, so that a connection is established between the optical fiber  101  and the optical network terminal  100 . 
     For example, an optical signal from the optical fiber  101  is converted into an electrical signal by the optical module  200 , and then the electrical signal is input into the optical network terminal  100 . An electrical signal from the optical network terminal  100  is converted into an optical signal by the optical module  200 , and then the optical signal is input into the optical fiber  101 . Since the optical module  200  is a tool for achieving interconversion between the optical signal and the electrical signal, and doesn&#39;t have a data processing function, the information does not change in the above photoelectric conversion process. 
     The optical network terminal  100  includes a housing in a substantially cuboid shape, an optical module interface  102  and a network cable interface  104  that are disposed on the housing. The optical module interface  102  is configured for connecting the optical module  200 , so that a bidirectional electrical signal connection is established between the optical network terminal  100  and the optical module  200 . The network cable interface  104  is configured for connecting the network cable  103 , so that a bidirectional electrical signal connection is established between the optical network terminal  100  and the network cable  103 . Connection between the optical module  200  and the network cable  103  is established through the optical network terminal  100 . 
     For example, the optical network terminal  100  transmits an electrical signal from the optical module  200  to the network cable  103 , and transmits an electrical signal from the network cable  103  to the optical module  200 . Therefore, the optical network terminal  100 , as a master monitor of the optical module  200 , may monitor operation of the optical module  200 . In addition to the optical network terminal  100 , the master monitor of the optical module  200  may further includes an optical line terminal (OLT). 
     A bidirectional signal transmission channel has been established between the remote server  1000  and the local information processing device  2000  through the optical fiber  101 , the optical module  200 , the optical network terminal  100  and the network cable  103 . 
       FIG. 2  is a diagram showing a structure of an optical network terminal, in accordance with some embodiments. In order to clearly show a connection relationship between the optical module  200  and the optical network terminal  100 ,  FIG. 2  only shows a structure of the optical network terminal  100  that is related to the optical module  200 . As shown in  FIG. 2 , the optical network terminal  100  further includes a circuit board  105  disposed in the housing, a cage  106  disposed on a surface of the circuit board  105 , a heat sink  107  disposed on the cage  106 , and an electrical connector disposed inside the cage  106 . The electrical connector is configured for connecting the electrical port of the optical module  200 ; and the heat sink  107  has protruding portions such as fins that increase a heat dissipation area. 
     The optical module  200  is inserted into the cage  106  of the optical network terminal  100  and is fixed by the cage  106 . Heat generated by the optical module  200  is conducted to the cage  106  and is then dissipated through the heat sink  107 . After the optical module  200  is inserted into the cage  106 , the electrical port of the optical module  200  is connected to the electrical connector inside the cage  106 , so that a bidirectional electrical signal connection is established between the optical module  200  and the optical network terminal  100 . In addition, the optical port of the optical module  200  is connected to the optical fiber  101 , so that a bidirectional optical signal connection is established between the optical module  200  and the optical fiber  101 . 
       FIG. 3  is a diagram showing a structure of an optical module, in accordance with some embodiments.  FIG. 4  is a diagram showing an exploded structure of an optical module, in accordance with some embodiments. As shown in  FIGS. 3 and 4 , the optical module  200  includes a shell, a circuit board  30 , a light emitting assembly  40  and a light receiving assembly  60  that are disposed in the shell. 
     The shell includes an upper shell  201  and a lower shell  202 . The upper shell  201  is covered on the lower shell  202  to form the shell having two openings  204  and  205 , and an outer contour of the shell is generally in a cuboid shape. 
     In some embodiments, the lower shell  202  includes a bottom plate  2021  and two lower side plates  2022  that are located on two sides of the bottom plate  2021  and disposed perpendicular to the bottom plate  2021 ; the upper shell  201  includes a cover plate  2011 , and the cover plate  2011  covers the two lower side plates  2022  of the lower shell  202  to form the shell. 
     In some embodiments, the lower shell  202  includes a bottom plate  2021  and two lower side plates  2022  that are located on two sides of the bottom plate  2021  and disposed perpendicular to the bottom plate  2021 ; the upper shell  201  includes a cover plate  2011  and two upper side plates that are located on two sides of the cover plate  2011  and disposed perpendicular to the cover plate  2011 . The two upper side plates are combined with the two lower side plates  2022  respectively, so that the upper shell  201  covers the lower shell  202 . 
     A direction of a connection line between the two openings  204  and  205  may be the same as a longitudinal direction of the optical module  200 , or may not be the same as the longitudinal direction of the optical module  200 . For example, the opening  204  is located at an end (a right end in  FIG. 3 ) of the optical module  200 , and the opening  205  is also located at an end (a left end in  FIG. 3 ) of the optical module  200 . Alternatively, the opening  204  is located at an end of the optical module  200 , and the opening  205  is located at a side of the optical module  200 . The opening  204  is the electrical port, and a connecting finger  310  of the circuit board  30  extends out from the electrical port  204 , and is inserted into the master monitor (e.g., the optical network terminal  100 ). The opening  205  is the optical port, and is configured for connecting the external optical fiber  101 , so that the optical fiber  101  is connected to the light emitting assembly  40  and the light receiving assembly  60  that are inside the optical module  200 . The circuit board  30  and optoelectronic devices such as the light emitting assembly  40  and the light receiving assembly  60  are in the above shell. 
     With help of an assembly manner of combining the upper shell  201  with the lower shell  202 , it may be easier to install the circuit board  30  and the optoelectronic devices such as the light emitting assembly  40  and the light receiving assembly  60  into the shell, and the upper shell  201  and the lower shell  202  may provide sealing and protection for these devices. In addition, with help of a shell with a split structure, in a case where the circuit board  30 , the optoelectronic devices such as the light emitting assembly  40  and the light receiving assembly  60  are assembled, it may be easier to arrange the positioning elements, heat dissipation elements and electromagnetic shielding elements of these devices, which facilitates automated production. 
     In some embodiments, the upper shell  201  and the lower shell  202  are made of a metallic material, which helps achieve electromagnetic shielding and heat dissipation. 
     In some embodiments, the optical module  200  further includes an unlocking component  203  on an outer wall of the shell thereof, and the unlocking component  203  is configured to implement or release a fixed connection between the optical module  200  and the master monitor. 
     For example, the unlocking component  203  is on outer walls of the two lower side plates  2022  of the lower shell  202 , and includes an engagement element that is matched with a cage of the master monitor (e.g., the cage  106  of the optical network terminal  100 ). In a case where the optical module  200  is inserted into the cage of the master monitor, the optical module  200  is fixed in the cage of the master monitor through the engagement element of the unlocking component  203 . In a case where the unlocking component  203  is pulled, the engagement element of the unlocking component  203  moves with the pulling, and then a connection relationship between the engagement element and the master monitor is changed to release the engagement between the optical module  200  and the master monitor, so that the optical module  200  may be pulled out of the cage of the master monitor. 
     The circuit board  30  includes circuit wires, electronic elements and chips. Through the circuit wires, the electronic elements and the chips are connected together according to circuit design, so as to implement power supply, electrical signal transmission, and grounding functions. The electronic elements may include, for example, a capacitor, a resistor, a triode, and a metal-oxide-semiconductor field-effect transistor (MOSFET). The chips may include, for example, a microcontroller unit (MCU), a laser driver chip, a limiting amplifier, a clock and data recovery (CDR) chip, a power management chip or a digital signal processing (DSP) chip. 
     The circuit board  30  is generally a rigid circuit board. Since it is made of a relatively hard material, the rigid circuit board may also have a support function. For example, the rigid circuit board may stably support the electronic elements and the chips; in a case where the light emitting assembly  40  and the light receiving assembly  60  are on the circuit board, the rigid circuit board may also stably support the light emitting assembly  40  and the light receiving assembly  60 . The rigid circuit board may also be inserted into an electrical connector inside the cage of the master monitor. 
     The circuit board  30  further includes a connecting finger  310  formed on an end surface thereof, and the connecting finger  310  includes a plurality of independent pins. The circuit board  30  is inserted into the cage  106 , and is conductively connected to the electrical connector inside the cage  106  through the connecting finger  310 . The connecting finger  310  may be disposed on only one surface (e.g., an upper surface shown in  FIG. 4 ) of the circuit board  30 , or may be disposed on both the upper and lower surfaces of the circuit board  30  to adapt to an occasion where a large number of pins are needed. The connecting finger  310  is configured to establish electrical connection with the master monitor to implement power supply, grounding,  120  signal transmission and data signal transmission functions. 
     Of course, flexible circuit boards are also used in some optical modules. A flexible circuit board is generally used in conjunction with a rigid circuit board as a supplement for the rigid circuit board. For example, the rigid circuit board  30  may be connected to the light emitting assembly  40  and the light receiving assembly  60  through the flexible circuit boards instead of the circuit wires. 
     The light emitting assembly  40  is configured to convert a data electrical signal into a data optical signal. The light receiving assembly  60  is configured to convert a data optical signal into a data electrical signal. 
       FIG. 5  is a diagram showing structures of a light emitting assembly and a circuit board, in accordance with some embodiments.  FIG. 6  is a diagram showing an exploded structure of a light emitting assembly, in accordance with some embodiments. As shown in  FIGS. 5 and 6 , the light emitting assembly  40  includes a case, a spacer  43 , a laser chip  44  and a lens  45 . 
     As shown in  FIG. 5 , components such as the spacer  43 , the laser chip  44  and the lens  45  are mounted in the case, and the case forms encapsulation and protection for these components. The circuit board  30  is inserted into the case of the light emitting assembly  40 , and is electrically connected to components in the case through metal connection lines (e.g., gold lines). Of course, these components may also be packaged in a non-hermetic manner. 
     As shown in  FIG. 6 , the case of the light emitting assembly  40  includes a cover plate  41  and a lower case  42  with a cavity, and the cover plate  41  is fastened on the lower case  42  to form an accommodating cavity. The components such as the spacer  43 , the laser chip  44  and the lens  45  are disposed in the accommodating cavity. 
     The laser chip  44  converts a data electrical signal from the circuit board  30  into a data optical signal, and light emitted by the laser chip  44  is converged through the lens  45  and then enters an optical fiber adapter  54  (as shown in  FIG. 4 ). The light emitted by the laser chip  44  is transmitted to the optical fiber  101  through the optical fiber adapter  54  and is finally transmitted to an outside of the optical module  200  through the optical fiber  101 . 
     In some embodiments, the spacer  43  is electrically connected to the circuit board  30  and a laser chip  44 , and the spacer  43  is configured to transmit signals and bear devices. 
       FIG. 7  is a diagram showing a structure of a spacer, in accordance with some embodiments. As shown in  FIG. 7 , the spacer  43  includes an insulating heat-conducting layer  434  and a metal layer  435 . 
     The insulating heat-conducting layer  434  and the metal layer  435  are stacked, and a side of the insulating heat-conducting layer  434  away from the metal layer  435  is in contact with a semiconductor cooler or the case of the light emitting assembly  40 . 
     In some embodiments, since ceramic materials have good thermal conductivity and insulating properties, the insulating heat-conducting layer  434  is made of ceramic materials. Of course, materials of the insulating heat-conducting layer  434  are not limited to this. 
     The metal layer  435  is electrically connected to the circuit board  30  and the laser chip  44 , so as to transmit a high-frequency data electrical signal from the circuit board  30  to the laser chip  44 . The laser chip  44  emits an optical signal based on the electrical signal. A ground-signal-ground (GSG) mode is used as a transmission mode of high-frequency data electrical signals between the circuit board  30  and the metal layer  435 , and the metal layer  435  includes a first spacer ground line  431 , a spacer signal line  432  and a second spacer ground line  433 . The first spacer ground line  431  and the second spacer ground line  433  are disposed on two opposite sides of the spacer signal line  432 . For example, the first spacer ground line  431  and the second spacer ground line  433  are disposed, in a direction perpendicular to an extension direction of the spacer signal line  432 , on two opposite sides of the spacer signal line  432 . 
     It will be noted that, layouts of the first spacer ground line  431 , the spacer signal line  432  and the second spacer ground line  433  are not limited to the above design, and other layouts may be designed according to requirements such as a signal transmission rate and layouts of components. 
     In some embodiments, a cathode of the laser chip  44  may be fixed on the first spacer ground line  431  or the second spacer ground line  433  by welding or conductive glue, so that the cathode of the laser chip  44  is electrically connected to the first spacer ground line  431  or the second spacer ground line  433 . An anode of the laser chip  44  may be connected to the spacer signal line  432  through a connection line. 
     During the operation of the optical module  200 , a high-frequency data electrical signal from the master monitor is transmitted to chips such as the clock and data recovery chip and the laser driver chip through the connecting finger  310  of the circuit board  30 . The chips such as the clock and data recovery chip and the laser driver chip perform processing such as signal shaping and amplitude adjustment on the high-frequency data electrical signal received by the optical module  200 , so as to obtain a modulation signal capable of modulating light into an optical signal. Then, the modulation signal is transmitted to the laser chip  44  disposed on the spacer  43 , so that the laser chip  44  emits a data optical signal based on the modulation signal. 
       FIG. 8  is a diagram showing a connection manner between a circuit board and a light emitting assembly, in accordance with some embodiments.  FIG. 9  is a partial structural diagram of a circuit board and a light emitting assembly, in accordance with some embodiments. As shown in  FIGS. 8 and 9 , in order to ensure the signal transmission mode is the GSG mode, the circuit board  30  includes a first circuit board ground line  301 , a circuit board signal line  302  and a second circuit board ground line  303  that are disposed on its surface. The first circuit board ground line  301  and the second circuit board ground line  303  are arranged on two opposite sides of the circuit board signal line  302 . For example, the first circuit board ground line  301  and the second circuit board ground line  303  are arranged, in a direction perpendicular to an extension direction of the circuit board signal line  302 , on two opposite sides of the circuit board signal line  302 . Wires of the spacer  43  and the circuit board  30  are connected together through connection lines  50  with help of a wire bonding process. As shown in  FIG. 9 , the first spacer ground line  431  of the spacer  43  is connected to the first circuit board ground line  301  of the circuit board  30  through a first connection line  501 , the spacer signal line  432  of the spacer  43  is connected to the circuit board signal line  302  of the circuit board  30  through a second connection line  502 , and the second spacer ground line  433  of the spacer  43  is connected to the second circuit board ground line  303  of the circuit board  30  through a third connection line  503 , so as to send the high-frequency data electrical signal from the circuit board  30  to the laser chip  44  disposed on the spacer  43 . 
     Through the above connection manner, the laser chip  44  emits an optical signal based on a high-frequency data electrical signal and a bias current which are from the circuit board  30 . The optical signal enters the optical fiber adapter  54  through the lens  45 , and finally is transmitted to the outside of the optical module through the optical fiber  101  connected to the optical fiber adapter  54 . 
     In some embodiments, the circuit board  30  includes a ground metal layer  320 , and the ground metal layer  320  is disposed on a surface of the circuit board  30  opposite to a surface of the circuit board  30  on which the first circuit board ground line  301  is located. The spacer  43  includes a ground metal layer  436 , and the ground metal layer  436  is disposed on a side of the insulating heat-conducting layer  434  away from the metal layer  435 . The circuit board  30  or the spacer  43  includes a ground hole. A ground hole of the circuit board  30  corresponds to at least one of the first circuit board ground line  301  or the second circuit board ground line  303 , and a ground hole of the spacer  43  corresponds to at least one of the first spacer ground line  431  or the second spacer ground line  433 , so that at least one of the first circuit board ground line  301 , the second circuit board ground line  303 , the first spacer ground line  431  or the second spacer ground line  433  is electrically connected to a corresponding ground metal layer through a corresponding ground hole, so that a return path of a high-frequency signal is shortened. 
     For example, the circuit board  30  includes a ground hole corresponding to the first circuit board ground line  301 . The ground hole penetrates the circuit board  30 , so that the first circuit board ground line  301  is electrically connected to the ground metal layer  320  of the circuit board  30 . Alternatively, the spacer  43  includes a ground hole corresponding to the first spacer ground line  431 . The ground hole penetrates the spacer  43 , so that the first spacer ground line  431  is electrically connected to the ground metal layer  436  of the spacer  43 . Alternatively, the circuit board  30  includes a ground hole corresponding to the second circuit board ground line  303 , and the spacer  43  includes a ground hole corresponding to the second spacer ground line  433 . The ground hole corresponding to the second circuit board ground line  303  penetrates the circuit board  30 , so as to achieve an electrical connection between the second circuit board ground line  303  and the ground metal layer  320  of the circuit board  30 . The ground hole corresponding to the second spacer ground line  433  penetrates the spacer  43 , so as to achieve an electrical connection between the second spacer ground line  433  and the ground metal layer  436  of the spacer  43 . 
     In order to improve a communication rate of the optical module  200 , a plurality of groups of optical emission paths are arranged inside the optical module  200 , for example, four groups of optical emission paths are shown in  FIG. 8 . The more the number of optical emission paths, the larger a volume of the optical module  200 . In order to meet miniaturization requirements of the optical module  200 , there is a need to reduce a size of each group of the optical emission paths. As a result, ground lines of the spacer  43  and the circuit board  30  are relatively thin, that is, areas of the ground lines are small, and thus a ground hole may not be disposed at a position of a ground line. 
     To this end, in some embodiments, as shown in  FIG. 9 , connections among the first spacer ground line  431 , the second spacer ground line  433 , the first circuit board ground line  301  and the second circuit board ground line  303  further include at least one of the followings: the first spacer ground line  431  of the spacer  43  is connected to the second spacer ground line  433  of the spacer  43  through a fourth connection line  504 , the first spacer ground line  431  of the spacer  43  is connected to the second circuit board ground line  303  of the circuit board  30  through a fifth connection line  505 , the second spacer ground line  433  of the spacer  43  is connected to the first circuit board ground line  301  of the circuit board  30  through a sixth connection line  506 , or the first circuit board ground line  301  of the circuit board  30  is connected to the second circuit board ground line  303  of the circuit board  30  through a seventh connection line  507 . 
     Ground lines of the spacer  43  and the circuit board  30  are connected together by at least one of the fourth connection line  504  to the seventh connection line  507 , so that a length of a return path of a high-frequency data electrical signal and an area surrounded by the return path of the high-frequency data electrical signal may be effectively reduced, and in turn, electromagnetic interference radiation of signals is reduced, signal crosstalk between paths is prevented, and transmission of the high-frequency data electrical signal between the circuit board  30  and the spacer  43  is kept in the GSG mode. 
     Signal transmission is performed between the circuit board  30  and the spacer  43  through the second connection line  502 . Since a connection line is usually thin, that is, a diameter of the connection line is small, and parasitic inductance introduced by the connection line is large. In addition, with improvement of the communication rate of the optical module, the parasitic inductance introduced by the connection line continues to increase, and influence on optoelectronic performance of the optical module is also more and more obvious. Therefore, the number of each of the above first connection line  501  to third connection line  503  is set to be two or more, and a diameter of each of an entirety formed by first connection lines  501 , an entirety formed by second connection lines  502  and an entirety formed by third connection lines  503  may be increased. In this way, inductance generated during operation of the optical module may be reduced, so that the optoelectronic performance of the optical module is improved. 
     Of course, the present disclosure is not limited to providing a plurality of first connection lines  501 , a plurality of second connection lines  502  or a plurality of third connection lines  503 . In some embodiments, there are only a plurality of the first connection lines  501 , or there are only a plurality of the second connection lines  502 , or there are only a plurality of the third connection lines  503 . In other embodiments, there are a plurality of the first connection lines  501  and a plurality of the second connection lines  502 , or there are a plurality of the first connection lines  501  and a plurality of the third connection lines  503 , or there are a plurality of the second connection lines  502  and a plurality of the third connection lines  503 . 
     Of course, numbers of the first connection lines  501  to third connection lines  503  may be the same or different. For example, as shown in  FIG. 9 , numbers of the first connection lines  501  to the third connection lines  503  are the same, and each are two. In addition, ground lines of the circuit board  30  and ground lines of the spacer  43  are connected together through connection lines, instead of setting ground holes at positions of circuit board ground lines and spacer ground lines; solder joints of the connection lines occupy a smaller area than the ground holes. Therefore, numbers of first connection lines  501 , the second connection lines  502  and the third connection lines  503  may be increased, for limited areas of the circuit board ground lines and the spacer ground lines. 
     It will be noted that, it is not limited to only using a method of connecting ground lines of the circuit board  30  and ground lines of the spacer  43  through connection lines to shorten the return path of the high-frequency signal. According to actual areas of the ground lines of the spacer  43  and the ground lines of the circuit board  30 , it is possible to shorten the return path of the high-frequency signal with help of combining the manner of connecting the ground lines of the circuit board to the ground lines of the spacer through the connection lines, with a manner of connecting the ground lines of the circuit board and the ground lines of the spacer to a corresponding ground metal layer through a corresponding ground hole. 
     For example, the first spacer ground line  431  of the spacer  43  is connected to the second spacer ground line  433  of the spacer  43  through the fourth connection line  504 , and the first circuit board ground line  301  and the second circuit board ground line  303  of the circuit board  30  are connected to the ground metal layer  320  of the circuit board  30  through ground holes. Alternatively, the first spacer ground line  431  of the spacer  43  is connected to the second circuit board ground line  303  of the circuit board  30  through the fifth connection line  505 , and the second spacer ground line  433  of the spacer  43  is connected to the ground metal layer  436  of the spacer  43  through a ground hole. Alternatively, the second spacer ground line  433  of the spacer  43  is connected to the first circuit board line  301  of the circuit board  30  through the sixth connection line  506 , and the second circuit board ground line  303  of the circuit board  30  is connected to the ground metal layer  320  of the circuit board  30  through a ground hole. Alternatively, the first circuit board ground line  301  of the circuit board  30  is connected to the second circuit board ground line  303  of the circuit board  30  through the seventh connection line  507 , and the first spacer ground line  431  and the second spacer ground line  433  of the spacer  43  are connected to the ground metal layer  436  of the spacer  43  through ground holes. 
       FIG. 10  is a partial side view of a circuit board and a spacer, in accordance with some embodiments. The impedance matching requirements (e.g., 50 ohms±10%) need to be met for the signal transmission between the circuit board  30  and the spacer  43 , that is, a length of a connection line for connecting the spacer signal line  432  of the spacer  43  and the circuit board signal line  302  of the circuit board  30  is limited by the impedance matching requirements. Therefore, in order to facilitate the control of lengths of the first connection line  501 , the second connection line  502  and the third connection line  503 , as shown in  FIG. 10 , the first connection line  501 , the second connection line  502  and the third connection line  503  are welded first, during wire bonding, and then other connection lines for connecting ground lines are welded. 
     In some embodiments, in a case where the above connection lines are welded, ends of the connection lines may be melted into metal solder balls at a high temperature, and then the connection lines may be welded to the above ground lines or signal lines through the metal solder balls by applying certain pressure. Alternatively, in order to improve welding speed, ends of the connection lines may be welded to the above ground lines or signal lines by a pressure welding method (e.g., using a gold wire bonding cleaver). Alternatively, both ends of each connection line are welded by a combination of the above two welding methods. 
     As shown in  FIG. 10 , the fifth connection line  505  is covered on the first connection line  501  to the third connection line  503  (the second connection line  502  and the third connection line  503  are not shown in  FIG. 10 ), that is, the first connection line  501  to the third connection line  503  are spatially surrounded by the fifth connection line  505 , so that the high-frequency data electrical signal transmitted between the circuit board  30  and the spacer  43  may be covered, and it is possible to keep the signal transmission mode between the circuit board  30  and the spacer  43  to be the GSG mode. Based on the same principles, the sixth connection line  506  may also cover on the first connection line  501  to the third connection line  503 . 
     In addition, in order to nicely cover the first connection line  501  to the third connection line  503 , the fourth connection line  504  and the seventh connection line  507  are respectively arranged on outer sides of the first connection line  501 , the second connection line  502  and the third connection line  503 . That is, solder joints of the fourth connection line  504  on the spacer ground lines are disposed at positions closer to the laser chip  44  than solder joints of the first connection line  501  to the third connection line  503  on the spacer ground lines, and solder joints of the seventh connection line  507  on the circuit board ground lines are disposed at positions closer to the connecting finger of the circuit board  30  than solder joints of the first connection line  501  to the third connection line  503  on the circuit board ground lines. 
     In some embodiments, in order to nicely cover the first connection line  501  to the third connection line  503  and to be grounded, the number of each of the above fourth connection line  504  to the seventh connection line  507  may be set to be two or more. Of course, the present disclosure is not limited to providing a plurality of fourth connection lines  504  to seventh connection lines  507 . In some embodiments, there may be only a plurality of fourth connection lines  504 , or there may be only a plurality of fifth connection lines  505  and a plurality of sixth connection lines  506 , or there may be only a plurality of fourth connection lines  504 , a plurality of sixth connection lines  506  and a plurality of seventh connection lines  507 . 
     Of course, the numbers of the above fourth connection lines  504  to seventh connection lines  507  may be the same or different. For example, as shown in  FIG. 9 , there are two seventh connection lines  507 , one fourth connection lines  504 , two fifth connection lines  505  and two sixth connection lines  506 . 
     Generally, the circuit board  30  is designed as a multi-layer circuit board, and circuits of the circuit board  30  are laid out on various layers of the circuit board  30  to reduce an area of the circuit board  30 .  FIG. 11  is a partial structural diagram of a circuit board and a spacer, in accordance with some embodiments. As shown in  FIG. 11 , the light emitting assembly  40  further includes a backlight detector  46 . The backlight detector  46  is disposed on a backlight side of the laser chip  44 . The optical fiber adapter  54  is disposed on a light-emitting side of the laser chip  44 . The laser chip  44  includes a light outlet for emitting an optical signal in an M direction and a light outlet for emitting an optical signal in an N direction. A light-sensitive surface of the backlight detector  46  corresponds to the light outlet of the laser chip  44  for emitting the optical signal in the M direction. Among optical signals emitted by the laser chip  44 , a high-power optical signal propagates toward the optical fiber adapter  54  (in the N direction), and a low-power optical signal propagates toward the backlight detector  46  (in the M direction). 
     The backlight detector  46  is configured to receive the low-power optical signal emitted by the laser chip  44  and monitor power of the low-power optical signal emitted by the laser chip  44 . Power of light entering the backlight detector  46  is generally much smaller than total power of light emitted by the laser chip  44 , and the power of the light entering the backlight detector  46  is usually set to be 1/10 of the total power of the light emitted by the laser chip  44 . Power of the light emitted by the laser chip  44  in the N direction may be monitored by the backlight detector  46 . 
     The backlight detector  46  generates a photocurrent based on the received optical signal, and transmits the photocurrent to a microprocessor  31  disposed on a surface of the circuit board  30 . Since the above photocurrent signal is a low-frequency signal, wires for transmitting the low-frequency signal are arranged on a layer of the circuit board  30  that is different from a layer on which the microprocessor  31  is located. For example, the microprocessor  31  is disposed on a first layer of the circuit board  30 , and the wires for transmitting the low-frequency signal are arranged on a second or third layer of the circuit board  30 . 
     In order to achieve an electrical connection between the backlight detector  46  and the microprocessor  31 , and shorten a transmission distance of the low-frequency signal, as shown in  FIG. 11 , the circuit board  30  includes a backlight detector welding hole  304 , and a position of the backlight detector welding hole  304  corresponds to a position of the second circuit board ground line  303 . The backlight detector welding hole  304  is electrically connected to the second circuit board ground line  303 , and the backlight detector welding hole  304  extends to a layer of the circuit board  30  for transmitting the low-frequency signal. The backlight detector  46  is electrically connected to the second spacer ground line  433 . In this case, the backlight detector  46  is electrically connected to the microprocessor  31  through the second spacer ground line  433 , the third connection line  503 , the second circuit board ground line  303 , the backlight detector welding hole  304  and the wires for transmitting the low-frequency signal. The photocurrent output by the backlight detector  46  may be transmitted to the microprocessor  31 , so as to achieve power monitoring of the light emitted by the laser chip  44  in the N direction. 
     In some embodiments, the circuit board  30  includes a bias current source welding hole  305 , and a position of the bias current source welding hole  305  corresponds to the position of the second circuit board ground line  303 . The bias current source welding hole  305  is electrically connected to the second circuit board ground line  303 , and the bias current source welding hole  305  extends to a layer of the circuit board  30  for transmitting the bias current signal. The laser chip  44  is electrically connected to the second spacer ground line  433 . In this case, the laser chip  44  is electrically connected to the laser driver chip  32  through the second spacer ground line  433 , the third connection line  503 , the second circuit board ground line  303 , the bias current source welding hole  305 , and wires for transmitting the bias current signal. The bias current output by the laser driver chip  32  is transmitted to the laser chip  44 . 
     Of course, the above backlight detector welding hole  304  and the bias current source welding hole  305  may also be disposed at positions corresponding to the first circuit board ground line  301 . By disposing the backlight detector welding hole  304  and the bias current source welding hole  305  at positions corresponding to the ground lines, the area of the circuit board  30  and a signal transmission distance between devices may be reduced. 
     The foregoing descriptions are merely specific implementations of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or replacements that a person skilled in the art could readily conceive of within the technical scope of the present disclosure shall be included in the protection scope of the present disclosure. Therefore, the scope of the present disclosure shall be subject to the protection scope of the claims.