CN112398541B

CN112398541B - Optical module

Info

Publication number: CN112398541B
Application number: CN202011223403.4A
Authority: CN
Inventors: 张加傲; 王欣南; 慕建伟
Original assignee: Hisense Broadband Multimedia Technology Co Ltd
Current assignee: Hisense Broadband Multimedia Technology Co Ltd
Priority date: 2020-11-05
Filing date: 2020-11-05
Publication date: 2022-05-17
Anticipated expiration: 2040-11-05
Also published as: CN112398541A

Abstract

The application provides an optical module, which comprises a circuit board and a light emitting device, wherein the light emitting device comprises a ceramic substrate, an EML laser and a first capacitor, a first film resistor and a second film resistor are arranged on the surface of the ceramic substrate, the EML laser comprises a light emitting area and an electric absorption modulation area, the first capacitor and the first film resistor are connected in series to form an RC circuit, the RC circuit is connected in parallel with the electric absorption modulation area, the first film resistor and the second film resistor are connected in parallel, the RC circuit can enable the impedance of the EML laser and the output impedance to be matched with the characteristic impedance between a laser driving chip and the laser, but the first film resistor generates deviation impedance during processing, so that the impedance matching performance of the RC circuit is poor, the first film resistor and the second film resistor are connected in parallel to eliminate the deviation impedance of the first film resistor as much as possible, and further improve the impedance matching performance of the RC circuit, and the integrity of signal transmission in the optical module is ensured.

Description

Optical module

Technical Field

The application relates to the technical field of optical communication, in particular to an optical module.

Background

When the optical module sends a signal, a golden finger introduces an electric signal into a laser driving chip, the laser driving chip transmits the electric signal to a laser, and then the laser is used for converting the electric signal into an optical signal, wherein the laser driving chip is connected with the laser through a lead, the lead has certain characteristic impedance, and as the impedance of the laser driving chip is rated, in order to ensure the signal integrity between the laser driving chip and the laser, the impedance output by the laser needs to be matched with the characteristic impedance, wherein the matching specifically means that the impedance value output by the laser reaches a characteristic impedance value.

Disclosure of Invention

The application provides an optical module, makes the impedance and the characteristic impedance phase-match of laser instrument output and then guarantees the signal integrality between laser instrument driver chip and the laser instrument.

A light module, comprising:

a circuit board;

the light emitting device is electrically connected with the circuit board and used for converting an electric signal into an optical signal;

the light emitting device includes:

the ceramic substrate is used for bearing a device;

the EML laser is carried by the ceramic substrate, comprises a light emitting area and an electric absorption modulation area and is used for converting an electric signal into an optical signal;

a first capacitor;

the first thin film resistor is arranged on the surface of the ceramic substrate and is connected with the first capacitor in series to form an RC circuit, and the RC circuit is connected with the electro-absorption modulation region in parallel;

and the second film resistor is arranged on the surface of the ceramic substrate, is connected with the first film resistor in parallel and is used for compensating the offset impedance of the first film resistor.

Has the advantages that: the application provides an optical module, including circuit board and light emitting device, light emitting device includes ceramic substrate, EML laser and first electric capacity, ceramic substrate surface is equipped with first film resistor and second film resistor, the EML laser is including sending out light zone and electric absorption modulation zone, wherein, first electric capacity and first film resistor establish ties into the RC circuit with electric absorption modulation zone is parallelly connected, first film resistor and second film resistor are parallelly connected, the RC circuit is the matching circuit, this circuit can make the impedance of EML laser and the impedance of output and the characteristic impedance match between laser drive chip and the laser instrument to guarantee signal transmission's integrality, but because first film resistor can produce the deviation impedance that deviates from ideal impedance 5% -10% to the upper limit when processing, lead to the impedance matching performance variation of RC circuit, through parallelly connected first film resistor and second film resistor in this application in order to eliminate first film resistor as far as possible The deviation impedance is as close as possible to the ideal impedance of the first film resistor, so that the impedance matching performance of the RC circuit is improved, and the integrity of signal transmission in the optical module is ensured.

Drawings

In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without any creative effort.

Fig. 1 is a schematic diagram of a connection relationship of an optical communication terminal;

FIG. 2 is a schematic diagram of an optical network unit;

fig. 3 is a schematic structural diagram of an optical module provided in an embodiment of the present application;

fig. 4 is an exploded structural schematic diagram of an optical module provided in an embodiment of the present application;

fig. 5 is a schematic diagram of an internal structure of an optical module according to an embodiment of the present disclosure;

fig. 6 is an exploded schematic view of a light emitting device according to an embodiment of the present application;

fig. 7 is a schematic partial structure diagram of a light emitting device provided in an embodiment of the present application;

fig. 8 is an equivalent circuit diagram illustrating connection of components in a light emitting device according to an embodiment of the present application;

fig. 9 is a schematic diagram of a comparison result obtained by simulation in the embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

One of the core links of optical fiber communication is the interconversion of optical and electrical signals. The optical fiber communication uses optical signals carrying information to transmit in information transmission equipment such as optical fibers/optical waveguides, and the information transmission with low cost and low loss can be realized by using the passive transmission characteristic of light in the optical fibers/optical waveguides; meanwhile, the information processing device such as a computer uses an electric signal, and in order to establish information connection between the information transmission device such as an optical fiber or an optical waveguide and the information processing device such as a computer, it is necessary to perform interconversion between the electric signal and the optical signal.

The optical module realizes the function of interconversion of optical signals and electrical signals in the technical field of optical fiber communication, and the interconversion of the optical signals and the electrical signals is the core function of the optical module. The optical module is electrically connected with an external upper computer through a golden finger on an internal circuit board of the optical module, and the main electrical connection comprises power supply, I2C signals, data signals, grounding and the like; the electrical connection mode realized by the gold finger has become the mainstream connection mode of the optical module industry, and on the basis of the mainstream connection mode, the definition of the pin on the gold finger forms various industry protocols/specifications.

Fig. 1 is a schematic diagram of connection relationship of an optical communication terminal. As shown in fig. 1, the connection of the optical communication terminal mainly includes the interconnection among the optical network terminal 100, the optical module 200, the optical fiber 101 and the network cable 103;

one end of the optical fiber 101 is connected with a far-end server, one end of the network cable 103 is connected with local information processing equipment, and the connection between the local information processing equipment and the far-end server is completed by the connection between the optical fiber 101 and the network cable 103; and the connection between the optical fiber 101 and the network cable 103 is made by the optical network terminal 100 having the optical module 200.

An optical port of the optical module 200 is externally connected to the optical fiber 101, and establishes bidirectional optical signal connection with the optical fiber 101; an electrical port of the optical module 200 is externally connected to the optical network terminal 100, and establishes bidirectional electrical signal connection with the optical network terminal 100; the optical module realizes the interconversion of optical signals and electric signals, thereby realizing the establishment of information connection between the optical fiber and the optical network terminal; specifically, the optical signal from the optical fiber is converted into an electrical signal by the optical module and then input to the optical network terminal 100, and the electrical signal from the optical network terminal 100 is converted into an optical signal by the optical module and input to the optical fiber.

The optical network terminal is provided with an optical module interface 102, which is used for accessing an optical module 200 and establishing bidirectional electric signal connection with the optical module 200; the optical network terminal is provided with a network cable interface 104, which is used for accessing the network cable 103 and establishing bidirectional electric signal connection with the network cable 103; the optical module 200 is connected to the network cable 103 through the optical network terminal 100, specifically, the optical network terminal transmits a signal from the optical module to the network cable and transmits the signal from the network cable to the optical module, and the optical network terminal serves as an upper computer of the optical module to monitor the operation of the optical module.

At this point, a bidirectional signal transmission channel is established between the remote server and the local information processing device through the optical fiber, the optical module, the optical network terminal and the network cable.

Common information processing apparatuses include routers, switches, electronic computers, and the like; the optical network terminal is an upper computer of the optical module, provides data signals for the optical module, and receives the data signals from the optical module, and the common upper computer of the optical module also comprises an optical line terminal and the like.

Fig. 2 is a schematic diagram of an optical network terminal structure. As shown in fig. 2, the optical network terminal 100 has a circuit board 105, and a cage 106 is disposed on a surface of the circuit board 105; an electric connector is arranged in the cage 106 and used for connecting an electric port of an optical module such as a golden finger; the cage 106 is provided with a heat sink 107, and the heat sink 107 has a projection such as a fin that increases a heat radiation area.

The optical module 200 is inserted into the optical network terminal, specifically, the electrical port of the optical module is inserted into the electrical connector inside the cage 106, and the optical port of the optical module is connected to the optical fiber 101.

The cage 106 is positioned on the circuit board, and the electrical connector on the circuit board is wrapped in the cage, so that the electrical connector is arranged in the cage; the optical module is inserted into the cage, held by the cage, and the heat generated by the optical module is conducted to the cage 106 and then diffused by the heat sink 107 on the cage.

Fig. 3 is a schematic structural diagram of an optical module according to an embodiment of the present disclosure, and fig. 4 is an exploded structural diagram of the optical module. The following describes the optical module in the optical communication terminal according to the foregoing embodiment with reference to fig. 3 and 4; as shown in fig. 3 and 4, an optical module 200 provided in the embodiment of the present application includes an upper housing 201, a lower housing 202, an unlocking member 203, a circuit board 300, and an optical transceiver module 400.

The upper shell 201 is covered on the lower shell 202 to form a wrapping cavity with two openings; the outer contour of the packaging cavity generally presents a square body. Specifically, the lower housing 202 includes a main board and two side boards located at two sides of the main board and arranged perpendicular to the main board; the upper shell comprises a cover plate, and the cover plate covers two side plates of the upper shell to form a wrapping cavity; the upper shell may further include two side walls disposed at two sides of the cover plate and perpendicular to the cover plate, and the two side walls are combined with the two side plates to cover the upper shell 201 on the lower shell 202.

The two openings may be two ends (204, 205) in the same direction, or two openings in different directions; one opening is an electric port 204, and a gold finger of the circuit board extends out of the electric port 204 and is inserted into an upper computer such as an optical network terminal; the other opening is an optical port 205 for external optical fiber access to connect with the optical transceiver module 400 inside the optical module; the photoelectric devices such as the circuit board 300 and the optical transceiver module 400 are positioned in the packaging cavity.

The assembly mode of combining the upper shell and the lower shell is adopted, so that the circuit board 300, the optical transceiver module 400 and other devices can be conveniently installed in the shells, and the upper shell and the lower shell form the outermost packaging protection shell of the module; the upper shell and the lower shell are made of metal materials generally, electromagnetic shielding and heat dissipation are achieved, the shell of the optical module cannot be made into an integral component generally, and therefore when devices such as a circuit board are assembled, the positioning component, the heat dissipation component and the electromagnetic shielding component cannot be installed, and production automation is not facilitated.

The unlocking component 203 is located on the outer wall of the wrapping cavity/lower shell 202, and is used for realizing the fixed connection between the optical module and the upper computer or releasing the fixed connection between the optical module and the upper computer.

The unlocking component 203 is provided with a clamping component matched with the upper computer cage; the end of the unlocking component can be pulled to enable the unlocking component to move relatively on the surface of the outer wall; the optical module is inserted into a cage of the upper computer, and the optical module is fixed in the cage of the upper computer by a clamping component of the unlocking component; by pulling the unlocking component, the clamping component of the unlocking component moves along with the unlocking component, so that the connection relation between the clamping component and the upper computer is changed, the clamping relation between the optical module and the upper computer is released, and the optical module can be drawn out from the cage of the upper computer.

The circuit board 300 is provided with circuit traces, electronic components (such as capacitors, resistors, triodes, and MOS transistors), and chips (such as an MCU, a laser driver chip, a limiting amplifier chip, a clock data recovery CDR, a power management chip, and a data processing chip DSP).

The circuit board 300 connects the electrical devices in the optical module together according to the circuit design through circuit wiring to realize the electrical functions of power supply, electrical signal transmission, grounding and the like.

The circuit board is generally a hard circuit board, and the hard circuit board can also realize a bearing effect due to the relatively hard material of the hard circuit board, for example, the hard circuit board can stably bear a chip; when the optical transceiver component is positioned on the circuit board, the rigid circuit board can also provide stable bearing; the hard circuit board can also be inserted into an electric connector in the upper computer cage, and specifically, a metal pin/golden finger is formed on the surface of the tail end of one side of the hard circuit board and is used for being connected with the electric connector; these are not easily implemented with flexible circuit boards.

A flexible circuit board is also used in a part of the optical module to supplement a rigid circuit board; the flexible circuit board is generally used in combination with a rigid circuit board, for example, the rigid circuit board may be connected to the optical transceiver module by using the flexible circuit board.

The optical transceiver module 400 includes two parts, namely an optical transmitter and an optical receiver, which are respectively used for transmitting and receiving optical signals. The emission secondary module generally comprises a light emitter, a lens and a light detector, wherein the lens and the light detector are respectively positioned on different sides of the light emitter, light beams are respectively emitted from the front side and the back side of the light emitter, and the lens is used for converging the light beams emitted from the front side of the light emitter so that the light beams emitted from the light emitter are converging light to be conveniently coupled to an external optical fiber; the optical detector is used for receiving the light beam emitted by the reverse side of the optical emitter so as to detect the optical power of the optical emitter. Specifically, light emitted by the light emitter enters the optical fiber after being converged by the lens, and the light detector detects the light emitting power of the light emitter so as to ensure the constancy of the light emitting power of the light emitter. The optical transceiver module 400 will be described in detail below.

Fig. 5 is a schematic diagram of an internal structure of an optical module according to an embodiment of the present disclosure; as shown in fig. 5, the optical transceiver module 400 in the foregoing embodiment includes an optical transmitter 500 and an optical receiver 700, and the optical module further includes a round-square tube 600 and an optical fiber adapter 800, in this embodiment, the optical transceiver sub-module is preferably an optical fiber adapter 800 for connecting optical fibers, that is, the optical fiber adapter 800 is embedded on the round-square tube 600 for connecting optical fibers. Specifically, the round and square tube 600 is provided with a third tube opening 603 for inserting the optical fiber adapter 800, the optical fiber adapter 800 is embedded into the third tube opening 603, the light emitting device 500 and the light receiving device 700 respectively establish optical connection with the optical fiber adapter 800, light emitted from the light receiving and emitting assembly and received light are transmitted through the same optical fiber in the optical fiber adapter, that is, the same optical fiber in the optical fiber adapter is a transmission channel for light entering and exiting from the light receiving and emitting assembly, and the light receiving and emitting assembly realizes a single-fiber bidirectional light transmission mode.

The round and square tube 600 is used for carrying the light emitting device 500 and the light receiving device 700, and in the embodiment of the present application, the round and square tube 600 is made of a metal material, which is beneficial to realizing electromagnetic shielding and heat dissipation. The round and square tube body 600 is provided with a first tube orifice 601 and a second tube orifice 602, and the first tube orifice 601 and the second tube orifice 602 are respectively arranged on the adjacent side walls of the round and square tube body 600. Preferably, the first nozzle 601 is disposed on a side wall of the round and square tube 600 in the length direction, and the second nozzle 602 is disposed on a side wall of the round and square tube 600 in the width direction.

The light emitting device 500 is embedded in the first pipe orifice 601, and the light emitting device 500 is in heat conduction contact with the round and square pipe body 600 through the first pipe orifice 601; the light receiving device 700 is embedded in the second pipe port 602, and the light receiving device 700 is in heat-conducting contact with the round-square pipe body 600 through the second pipe port 602. Alternatively, the light emitting device 500 and the light receiving device 700 are press-fitted directly into the round and square tube body 600, and the round and square tube body 600 is in contact with the light emitting device 500 and the light receiving device 700, respectively, directly or through a heat transfer medium. So the heat dissipation that circle square body can be used to light emitting device 500 and light receiving device 700 guarantees light emitting device 500 and light receiving device 700.

Fig. 6 is an exploded view of a light emitting device according to an embodiment of the present application; fig. 7 is a partial structural schematic diagram of a light emitting device provided in an embodiment of the present application; as shown in fig. 6 and 7, in the embodiment of the present application, the light emitting device 500 includes a stem 501, a TEC502 disposed on a surface of the stem, a base 503 disposed on a surface of the TEC502, and a ceramic substrate 504 disposed on a surface of the base 503, and specifically, the light emitting device 500 is packaged in a TO coaxial package, and the stem 501 is used TO support and carry the TEC502, the base 503, and the ceramic substrate 504; the lower surface of the TEC502 directly contacts the upper surface of the tube seat 501, and the upper surface of the TEC502 directly contacts the lower surface of the base 503, that is, one heat exchange surface of the TEC502 directly sticks to the upper surface of the tube seat 501, and the other heat exchange surface directly sticks to the lower surface of the base 503; the base 503 is used to support the ceramic substrate 504. In this example, the base 503 mainly plays a role of heat dissipation and load bearing, and the material of the base 503 includes, but is not limited to, tungsten copper, raft alloy, SPCC (Steel Plate Cold rolled Commercial, Cold rolled carbon Steel), copper, etc. to facilitate the heat generated by the optoelectronic device to be transferred to the TEC502 for heat dissipation; the ceramic substrate 504 is made of alumina ceramics, aluminum nitride ceramics and the like, a functional circuit of a laser chip is engraved on the surface of the ceramic substrate 504 and used for signal transmission, an EML laser 505 is arranged on the surface of the ceramic substrate 504, the EML laser 505 is an integrated device of a laser DFB and an electro-absorption modulator EA, the laser DFB converts an electric signal into an optical signal, and the electro-absorption modulator EA performs coding modulation on the optical signal and then outputs the optical signal, so that the output optical signal carries information. The electro-absorption modulator is one of the commonly used optical modulators, and has the characteristics of high response speed and low power consumption, so that the electro-absorption modulator is widely applied to transmission of high-speed optical signals.

In the application, the EML laser 505 is very sensitive to temperature change, and the EML laser 505 needs to be heated or cooled by the TEC502, so that the EML laser 505 is regulated to be at a constant working temperature. The light emitting device 500 of the present application further comprises a thermistor disposed on the base 503 for collecting the operating temperature of the EML laser 505 and further monitoring the operating temperature of the EML laser 505. Specifically, the temperature of the EML laser 505 is collected in real time through a thermistor, and the collected temperature of the EML laser 505 is fed back to a thermoelectric cooler driving circuit, and the thermoelectric cooler driving circuit determines that a heating or cooling current is input into the TEC502 according to the received temperature of the EML laser 505, so that the heating or cooling of the EML laser 505 is realized, and the temperature of the EML laser 505 can be controlled within a target temperature range.

When the optical module performs signal transmission, a gold finger introduces an electrical signal into a laser driver chip, the laser driver chip transmits the electrical signal to an EML laser 505, and then the EML laser 505 converts the electrical signal into an optical signal, wherein the laser driver chip and the EML laser 505 are connected by a wire, the wire has a certain characteristic impedance, because of the rated impedance output by the laser driver chip, when the impedance output by the EML laser 505 does not match with the characteristic impedance, the transmission signal between the laser driver chip and the laser will be lost, and the integrity of the signal is reduced, so in order to ensure the integrity of the signal, it is necessary to ensure that the impedance output by the EML laser 505 matches with the characteristic impedance, it should be noted that the matching means that the impedance value output by the EML laser 505 reaches the characteristic impedance value, that is, the EML laser 505 outputs an impedance value that matches the characteristic impedance value.

In the present application, the first thin-film resistor 506 is connected in parallel to the EML laser 505, and at this time, the first thin-film resistor 506 has an impedance matching function, and finally, the impedance output by the EML laser 505 is made to be consistent with the characteristic impedance, so the first thin-film resistor 506 may be referred to as a matching resistor; since the space of the ceramic substrate 504 is small, the first thin film resistor 506 is generally a thin film resistor, which is formed by sintering one area of the ceramic substrate 504, and the process is complicated, but since the first thin film resistor 506 generates a deviation impedance which deviates from the ideal impedance by 5% -10% to the upper limit during processing, the deviation impedance is an irresistible factor, and the existence of the deviation impedance reduces the impedance matching performance of the first thin film resistor 506, the second thin film resistor 507 is provided in the present application, the second thin film resistor 507 is connected in parallel with the first thin film resistor 506, and further the deviation impedance which deviates to the upper limit is compensated, taking the ideal impedance value of the first thin film resistor 506 as an example of 50 Ω, when the deviation impedance of 10% is generated, the impedance value of the first thin film resistor 506 is 1250 Ω, when the impedance value of the second thin film resistor 507 is 1250 Ω, because the first thin film resistor 506 and the second thin film resistor 507 are on the same ceramic substrate, the second thin film resistor 507 has the same upper limit characteristic, the impedance of the second thin film resistor 507 is 1375 Ω after the upper limit characteristic is reached, and the equivalent impedance of the first thin film resistor 506 and the second thin film resistor 507 after the two thin film resistors are connected in parallel is 52.88 Ω and is closer to the ideal impedance value of 50 Ω, so that the impedance matching performance of the first thin film resistor 506 is improved, wherein the second thin film resistor 507 can be in a thin film resistor form.

Specifically, the first thin film resistor 506 is used to make the impedance value output by the EML laser 505 match the characteristic impedance value, and the second thin film resistor 507 is used to compensate the offset impedance generated by the first thin film resistor 506 during processing to eliminate the offset impedance as much as possible, so that the impedance of the first thin film resistor 506 is restored to the ideal impedance value as much as possible; the EML laser 505 in this application includes a light emitting region 5051 and an electro-absorption modulation region 5052, the first thin film resistor 506 is connected in parallel with the electro-absorption modulation region 5052, the second thin film resistor 507 is connected in parallel with the first thin film resistor 506, and the second thin film resistor 507 is also connected in parallel with the electro-absorption modulation region 5052, that is, the first thin film resistor 506, the second thin film resistor 507, and the electro-absorption modulation region 5052 are connected in parallel, and specifically, the first thin film resistor 506 may be disposed behind the light emitting region 5051, and the second thin film resistor 507 may be disposed in front of the light emitting region 5051.

Meanwhile, when the impedance output by the EML laser 505 is not well matched with the characteristic impedance, the EML laser 505 may reflect a part of the signal, and the signal returns to the EML laser 505 along the original path, so as to reduce the performance of the signal, and may even cause distortion of the signal, and the first thin-film resistor 506 and the second thin-film resistor provided in the present application may simultaneously absorb the reflected part of the signal, and the second thin-film resistor is provided in front of the EML laser 505 in the present application, so as to further suppress the signal reflected by the EML laser 505.

In the present application, the second thin film resistor 507 is connected in parallel to the front of the EML laser 505, so that the high frequency reflection is well suppressed. In contrast, in the present application, a comparative simulation test is performed on whether the second thin-film resistor 507 is connected in parallel in front of the EML laser 505, and a test result is shown in fig. 9, where fig. 9 includes two curves, for convenience of description, a thinner curve is referred to as a first curve, and a thicker curve is referred to as a second curve, where the first curve is a result that the second thin-film resistor 507 is not connected in parallel in front of the EML laser 505, and the second curve is a result that the second thin-film resistor 507 is connected in parallel in front of the EML laser 505, and it can be seen from fig. 8 that adding a parallel resistor in a frequency band of 5 to 13GHZ has a better effect of suppressing reflection, and has better signal integrity corresponding to the laser.

As shown in fig. 7, the optical module provided in the embodiment of the present application further includes a first capacitor 508 and a second capacitor 509, where the first capacitor 508 and the second capacitor 509 are both disposed on the surface of the base 503, that is, the ceramic substrate 504, the first capacitor 508 and the second capacitor 509 are all disposed on the surface of the base 503, where the first capacitor 508 and the first thin-film resistor 506 are connected in series to form an RC circuit, the second thin-film resistor and the electro-absorption modulation region are connected in parallel, the circuit is disposed on the periphery of the EML laser 505, the surface of the base 503 has a first circuit region capable of transmitting signals, the first circuit region is a signal line transmission layer formed by a metal material, the positive electrode and the negative electrode of the first capacitor 508 are disposed on two opposite surfaces, where the negative electrode is disposed on the lower surface (bottom surface), the positive electrode is disposed on the upper surface (top surface), the negative electrode of the first capacitor 508 is connected to the first circuit region, the positive electrode of the first capacitor 508 is connected to one end of the first thin film resistor 506, and the first capacitor 508 has the functions of alternating current and direct current connection and accordingly reduces power consumption. The second capacitor 509 has a filtering function, specifically, the amplitude of voltage fluctuation of the EML laser 505 can be reduced, in this embodiment, the second capacitor 509 similarly has a positive electrode and a negative electrode, the positive electrode and the negative electrode are disposed on two opposite surfaces, wherein the negative electrode is disposed on the lower surface (bottom surface), the positive electrode is disposed on the upper surface (top surface), the negative electrode of the second capacitor 509 is also connected to the first circuit region, and the positive electrode of the second capacitor 509 is connected to the light emitting region 5051.

As shown in fig. 7, a first pad and a second pad are respectively disposed at two ends of the first thin film resistor 506, a third pad is disposed adjacent to the second pad, and an area formed by the first pad, the second pad and the third pad is disposed adjacent to an area occupied by the EML laser 505, for convenience of description, a metal wire between the first capacitor 508 and the first thin film resistor 506 is defined as a first metal wire, a metal wire between the first thin film resistor 506 and the EML laser 505 is defined as a second metal wire, a metal wire between the second capacitor 509 and the EML laser 505 is defined as a third metal wire, one end of the first metal wire is welded on the positive electrode of the first capacitor 508, the other end of the first metal wire is welded on the first pad, one end of the second metal wire is welded on the second pad, the other end of the second metal wire is welded on the positive electrode of the electro-absorption modulation region 5052, one end of the third metal wire is welded on the positive electrode of the second capacitor 509, the other end of the fourth metal wire is welded on a node of the third bonding pad, a fourth metal wire is led out from the other node of the third bonding pad, one end of the fourth metal wire is welded on the third bonding pad, and the other end of the fourth metal wire is welded on the anode of the light emitting region 5051.

The first lead is arranged between the anode of the first capacitor and the first film resistor, the second lead is arranged between the first film resistor and the anode of the electroabsorption modulation area, the third lead is arranged between the second capacitor and the light emitting area, the fourth lead is arranged between the anode of the electroabsorption modulation area and the fourth bonding pad, and the first lead, the second lead, the third lead and the fourth lead can be gold wires made of gold, and certainly, the first lead, the second lead, the third lead and the fourth lead can also be made of other metal materials.

Fig. 8 is an equivalent circuit diagram illustrating connection of components in a light emitting device according to an embodiment of the present application; as shown in fig. 8, the first thin film resistor and the first capacitor are connected in series to form an RC circuit, the branch where the electro-absorption modulation region is located and the branch where the second thin film resistor is located are connected in parallel, and the second capacitor is connected in parallel with the branch where the light-emitting region is located.

The surface of the ceramic substrate 504 has a second circuit area and a third circuit area, the second circuit area and the third circuit area are signal line transmission layers formed by metal materials, wherein a negative electrode of the EML laser 505 is connected to the second circuit area, and the EML laser 505 and the third circuit area are connected through a fifth metal wire, which mainly provides a power supply signal for the EML laser 505.

It can be seen that, the space for the second thin film resistor except the first pad, the second pad, the third pad, the first thin film resistor 506, the third circuit region and the EML laser 505 on the surface of the ceramic substrate 504 is small, the resistance value is often large, usually between 1000 Ω -1500 Ω, but the space for the second thin film resistor is small, and when the resistor with such a large resistance value is disposed in a small space, the second thin film resistor 507 is disposed in a zigzag arrangement in the small space in the present application, and of course, other arrangement forms may be used for arrangement, one end of the second thin film resistor 507 is grounded, and the other end is connected to the pad formed in the third circuit region.

The application provides an optical module, which comprises a circuit board and an optical emitting device, wherein the optical emitting device comprises a ceramic substrate, an EML laser, a first capacitor, a second capacitor, a first thin film resistor and a second thin film resistor, the EML laser is carried by the ceramic substrate and comprises a laser and an electric absorption modulator, the first capacitor is used for controlling the connection and disconnection of alternating current and direct current so as to reduce the power consumption, the second capacitor is used for reducing the voltage fluctuation of the laser, the first thin film resistor is used for enabling the impedance output by the laser to be matched with the characteristic impedance between a laser driving chip and the laser, but the first thin film resistor generates a deviation impedance which deviates from the ideal impedance by 5% -10% to the upper limit during processing, so the second thin film resistor is used for eliminating the deviation impedance of the first thin film resistor as far as possible and recovering to the vicinity of the ideal impedance of the first thin film resistor, wherein the respective connection mode is as follows: the first thin film resistor is connected with the electric absorption modulator in parallel, the second thin film resistor is connected with the first thin film resistor in parallel, the anode of the first capacitor is connected with one end of the first thin film resistor, the other end of the first thin film resistor is connected with the anode of the electric absorption modulator, the second capacitor is electrically connected with the laser, and the impedance output by the laser is matched with the characteristic impedance through the content, so that the signal integrity between the laser driving chip and the laser is ensured; meanwhile, when the laser impedance is not matched with the characteristic impedance, part of signals reflected by the laser can return along the original path, and distortion of the signals is caused, and the first thin film resistor and the second thin film resistor in the application can absorb the reflected signals, and the second thin film resistor is positioned in front of the EML laser and has the effect of strongly inhibiting the EML laser to reflect the signals, so that the impedance output by the laser can be matched with the characteristic impedance through the first thin film resistor and the second thin film resistor, and the signals reflected by the EML laser can be absorbed.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A light module, comprising:

a circuit board;

the light emitting device includes:

the ceramic substrate is used for bearing a device;

a first capacitor;

the second thin film resistor is arranged on the surface of the ceramic substrate, a fourth bonding pad is arranged at the position adjacent to the electro-absorption modulation region, and the second thin film resistor is connected to one side of the fourth bonding pad, arranged in a zigzag shape and connected with the first thin film resistor in parallel and used for compensating the offset impedance of the first thin film resistor;

the first thin film resistor and the second thin film resistor are respectively located on two sides of the electroabsorption modulation area and are respectively used for absorbing signals reflected by the two sides of the electroabsorption modulation area, and the second thin film resistor is also used for inhibiting signals reflected by the EML laser.

2. The optical module of claim 1, further comprising a base for carrying the first capacitor, the ceramic substrate, and a second capacitor, wherein:

the RC circuit, the branch where the electroabsorption modulation region is located and the branch where the second thin film resistor is located are connected in parallel;

the second capacitor is connected in parallel with the branch in which the light emitting area is located;

the two ends of the first thin film resistor are respectively provided with a first bonding pad and a second bonding pad, the first capacitor is connected to one end of the first thin film resistor through the first bonding pad, and the other end of the first thin film resistor is connected to one end of the electroabsorption modulation region through the second bonding pad;

a third bonding pad is arranged between the second capacitor and the light emitting area, and the second capacitor is connected to the light emitting area through the third bonding pad;

and a fourth bonding pad is arranged adjacent to the electro-absorption modulation region, the other end of the electro-absorption modulation region is connected to one side of the fourth bonding pad, and the second thin film resistor is connected to the other side of the fourth bonding pad.

3. The light module of claim 2, wherein a first wire is provided between the positive electrode of the first capacitor and the first thin film resistor, a second wire is provided between the first thin film resistor and the positive electrode of the electro-absorption modulation region, a third wire is provided between the second capacitor and the light emitting region, and a fourth wire is provided between the positive electrode of the electro-absorption modulation region and the fourth pad.

4. The optical module according to claim 2, wherein the base surface has a first circuit area, a negative electrode of the first capacitor is connected to the first circuit area, a negative electrode of the second capacitor is connected to the first circuit area, a positive electrode of the first capacitor is connected to the first thin film resistor, and a positive electrode of the second capacitor is connected to a positive electrode of the light emitting area.

5. The optical module according to claim 1, wherein the ceramic substrate surface has a second circuit region, the negative electrode of the light emitting region and the negative electrode of the electro-absorption modulation region are both connected to the second circuit region, and the positive electrode of the electro-absorption modulation region of the light emitting region is connected to the first thin film resistor.

6. The optical module of claim 2, wherein the ceramic substrate has a third circuit region thereon, and the second thin film resistor is connected to the electro-absorption modulation region through the third circuit region.

7. The optical module according to claim 1, wherein the second thin film resistor has a resistance value larger than that of the first thin film resistor to eliminate a deviation impedance of the first thin film resistor.