A protection circuit, a protection method, and an optical network device

Abstract

Embodiments of the present invention disclose a protection circuit, a protection method, and an optical network device for achieving overcurrent protection for different types of avalanche photodiodes (APDs). The protection circuit shown in the embodiments of the present invention includes: a power supply module, an image circuit, a processing module, and a branch switching module; the image circuit includes a first triode and a second triode, the branch switching module includes at least two parallel branches and a conduction switch, the conduction switch is connected between the power supply module and the second ends of the at least two parallel branches, the processing module is connected to the conduction switch, and the processing module is configured to control the conduction switch to conduct one of the power supply module and the at least two parallel branches, and among the at least two parallel branches, the resistances of different branches are different.

Description

Technical Field

[0001] This application relates to the field of optical communication, and in particular, to a protection circuit, a protection method, and an optical network device. Background Art

[0002] In existing optical network devices, an avalanche photon diode (APD) is usually used as a photoelectric conversion device.

[0003] To protect the safety of the APD, the prior art provides a protection circuit as shown in Figure 1 The protection circuit includes a power supply module 101, a first resistor 103, a second resistor 104, and an APD 102 connected in sequence. The protection circuit further includes a metal-oxide-semiconductor field-effect transistor (MOSFET) 105. Hereinafter, MOSFET will be abbreviated as MOS. Among them, the source electrode of MOS 105 is connected between the first resistor 103 and the second resistor 104, the drain electrode of MOS 105 is grounded, and the gate electrode of MOS 105 is connected between the second resistor 104 and the APD 102. The power supply module 101 is used to provide a bias voltage to the APD 102. The APD 102 performs photoelectric conversion on the received optical signal to generate an electrical signal. When the current of the electrical signal increases, the voltage drop of the first resistor 103 increases, thereby playing a role in current limiting and voltage reduction. The voltage drop of the second resistor 104 increases, causing MOS 105 to conduct. The conducting MOS 105 can clamp the further increase of the bias voltage on the APD 102 to prevent the APD 102 from being damaged due to excessive bias voltage.

[0004] However, for different types of APDs, the requirements for the voltage range of the bias voltage vary greatly. To ensure that different types of APDs can obtain a sufficiently large bias voltage to ensure that each type of APD can perform photoelectric conversion normally, the resistance values of the first resistor 103 and the second resistor 104 need to be relatively small. However, when the resistance value of the first resistor 103 is relatively small, the voltage dividing ability of the first resistor 103 is weak and cannot play a good role in current limiting and voltage reduction. When the resistance value of the second resistor 104 is relatively small, the voltage required for MOS 105 to conduct is relatively large, and the time required for MOS 105 to conduct is also relatively long. It is easy to occur that the APD 102 may be damaged before MOS 105 conducts. Summary of the Invention

[0005] Embodiments of the present invention provide a protection circuit, a protection method, and an optical network device, which are used to implement overload protection for different types of APDs.

[0006] In a first aspect, an embodiment of the present invention provides a protection circuit for protecting an avalanche photodiode (APD). The protection circuit includes a power supply module, a mirror circuit, a processing module, and a branch switching module. The mirror circuit includes a first triode and a second triode. The base of the first triode is connected to the base of the second triode. The collector of the second triode has a first output terminal and a second output terminal. The first output terminal is connected to the base of the second triode, and the second output terminal is used to connect to the APD. The branch switching module includes at least two parallel branches and a conduction switch. The first ends of the at least two parallel branches are connected to the first emitter, and the second emitter is connected to the power supply module. Herein, the first emitter is the emitter of the first triode, and the second emitter is the emitter of the second triode, or the first emitter is the emitter of the second triode, and the second emitter is the emitter of the first triode. The conduction switch is connected between the power supply module and the second ends of the at least two parallel branches. The processing module is connected to the conduction switch and is used to control the conduction switch to conduct one of the branches between the power supply module and the at least two parallel branches. Among the at least two parallel branches, the resistances of different branches are different.

[0007] It can be seen that the processing module can control the conduction switch to conduct one of the branches between the power supply module and the branch switching module according to the magnitude of the bias voltage of the APD. If the optical power of the optical signal received by the APD is too large and the probability of the APD being overloaded is relatively high, the branch conducted by the conduction switch can reduce the bias voltage transmitted to the APD to avoid the APD being overloaded. If the optical power of the optical signal received by the APD is small and the probability of the APD being overloaded is relatively low, the branch conducted by the conduction switch can increase the magnitude of the bias voltage transmitted to the APD, thus effectively ensuring that the APD can perform photoelectric conversion normally.

[0008] It can be seen that even for different types of APDs, according to the different requirements of the APD for the bias voltage, the conduction switch can conduct the branches with different resistances included in the power supply module and the branch switching module to effectively prevent different types of APDs from being overloaded.

[0009] Based on the first aspect, in an optional implementation manner, the first emitter is the emitter of the second triode, the second emitter is the emitter of the first triode, and the protection circuit includes a first branch connected between the second emitter and the power supply module; the at least two parallel branches include a second branch and a third branch, the ratio between the resistance value of the third branch and the resistance value of the first branch is a first ratio, the ratio between the resistance value of the second branch and the resistance value of the first branch is a second ratio, and the first ratio is greater than the second ratio; if the processing module determines that the voltage value of the APD is greater than or equal to a preset value, the processing module controls the conduction switch to conduct the power supply module and the third branch, and if the processing module determines that the voltage value of the APD is less than the preset value, the processing module controls the conduction switch to conduct the power supply module and the second branch.

[0010] It can be seen that when the optical power of the optical signal received by the APD is too large and the probability of the APD being overloaded is relatively high, the conduction switch conducts the power supply module and the third branch, so as to effectively reduce the voltage value of the bias voltage transmitted from the power supply module to the APD, and effectively avoid the overload of the APD. If the optical power of the optical signal received by the APD is small and the probability of the APD being overloaded is relatively low, the conduction switch conducts the power supply module and the second branch, so as to effectively increase the voltage value of the bias voltage transmitted from the power supply module to the APD and ensure that the APD can perform normal optoelectronic conversion.

[0011] Based on the first aspect, in an optional implementation manner, the first emitter is the emitter of the first triode, the second emitter is the emitter of the second triode, and the protection circuit includes a fourth branch connected between the second emitter and the power supply module; the at least two parallel branches include a fifth branch and a sixth branch, the ratio between the resistance value of the fifth branch and the resistance value of the fourth branch is a third ratio, the ratio between the resistance value of the sixth branch and the resistance value of the fourth branch is a fourth ratio, and the third ratio is greater than the fourth ratio; if the processing module determines that the voltage value of the APD is greater than or equal to a preset value, the processing module controls the conduction switch to conduct the power supply module and the fifth branch, and if the processing module determines that the voltage value of the APD is less than the preset value, the processing module controls the conduction switch to conduct the power supply module and the sixth branch.

[0012] It can be seen that when the optical power of the optical signal received by the APD is too high and the probability of the APD being overloaded is relatively high, the conduction switch conducts the power supply module and the fifth branch to effectively reduce the voltage value of the bias voltage transmitted from the power supply module to the APD, effectively avoiding the overload of the APD. If the optical power of the optical signal received by the APD is small and the probability of the APD being overloaded is relatively low, the conduction switch conducts the power supply module and the sixth branch to effectively increase the voltage value of the bias voltage transmitted from the power supply module to the APD, ensuring that the APD can perform normal optoelectronic conversion.

[0013] Based on the first aspect, in an optional implementation manner, the processing module is configured to determine the voltage value of the APD to determine whether the voltage value of the APD is greater than or equal to the preset value.

[0014] Based on the first aspect, in an optional implementation manner, the processing module is connected between the second output terminal and the cathode of the APD.

[0015] Based on the first aspect, in an optional implementation manner, the processing module is connected to the collector of the first triode. The processing module is further configured to detect the magnitude of the detection current output by the collector of the first triode, and the processing module is configured to determine the voltage value of the APD according to the magnitude of the detection current.

[0016] Based on the first aspect, in an optional implementation manner, the protection circuit further includes a resistor and a MOS field effect transistor. The second output terminal of the second triode is respectively connected to the source electrode of the MOS and the first end of the resistor. The drain electrode of the MOS is grounded, and the gate electrode of the MOS and the second end of the resistor are respectively configured to be connected to the cathode of the APD.

[0017] It can be seen that the conducting MOS can further reduce the bias voltage transmitted to the APD, avoiding the situation where the APD is damaged due to overload.

[0018] Based on the first aspect, in an optional implementation manner, within the first time period, the processing module is configured to control the power supply module to output a first power. The starting moment of the first time period is the moment when the power supply module starts to supply power to the APD. Within the second time period, the processing module is configured to control the power supply module to output a second power. The starting moment of the second time period is the end moment of the first time period. The power value of the first power is less than the power value of the second power.

[0019] Based on the first aspect, in an optional implementation manner, the processing module is further connected to the power supply module.

[0020] It can be seen that the processing module controls the power supply module to transmit the first power with a relatively small power value to the APD within the first time period, effectively avoiding the situation that the optical power of the optical signal received by the APD is too large and causing overload within the first time period, and effectively ensuring the safety of the APD.

[0021] In a second aspect, an embodiment of the present invention provides a protection method for protecting an avalanche photodiode APD. The method includes: according to the voltage value of the APD, controlling a conduction switch to conduct one of a power supply module and at least two parallel branches. The first ends of the at least two parallel branches are connected to a mirror circuit, the mirror circuit is connected to the APD, the conduction switch is connected between the power supply module and the second ends of the at least two parallel branches, and among the at least two parallel branches, the resistance values of different branches are different.

[0022] For the description of the beneficial effects shown in this aspect, please refer to the above first aspect, and no specific description will be given in this aspect.

[0023] Based on the second aspect, in an optional implementation manner, the controlling the conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD includes: if it is determined that the voltage value of the APD is greater than or equal to a preset value, controlling the conduction switch to conduct the power supply module and the third branch; or, if it is determined that the voltage value of the APD is less than the preset value, controlling the conduction switch to conduct the power supply module and the second branch; wherein, the mirror circuit includes a first triode and a second triode connected to each other. The first ends of the at least two parallel branches are connected to the emitter of the second triode, the emitter of the first triode is connected to the power supply module, the ratio between the resistance value of the third branch and the resistance value of the first branch is a first ratio, the ratio between the resistance value of the second branch and the resistance value of the first branch is a second ratio, the first ratio is greater than the second ratio, and the first branch is connected between the emitter of the first triode and the power supply module.

[0024] Based on the second aspect, in an optional implementation manner, controlling the conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD includes: if it is determined that the voltage value of the APD is greater than or equal to a preset value, controlling the conduction switch to conduct the power supply module and the fifth branch; or, if it is determined that the voltage value of the APD is less than the preset value, controlling the conduction switch to conduct the power supply module and the sixth branch; wherein, the mirror circuit includes a first triode and a second triode connected to each other, the first ends of the at least two parallel branches are connected to the emitter of the first triode, the emitter of the second triode is connected to the power supply module, the ratio between the resistance value of the fifth branch and the resistance value of the fourth branch is a third ratio, the ratio between the resistance value of the sixth branch and the resistance value of the fourth branch is a fourth ratio, the third ratio is greater than the fourth ratio, and the fourth branch is connected between the emitter of the second triode and the power supply module.

[0025] Based on the second aspect, in an optional implementation manner, before controlling the conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD, the method further includes: determining the voltage value of the APD; determining whether the voltage value of the APD is greater than or equal to the preset value.

[0026] Based on the second aspect, in an optional implementation manner, determining the voltage value of the APD includes: detecting the magnitude of the detection current output by the collector of the first triode, the mirror circuit including the first triode and the second triode connected to each other; determining the voltage value of the APD according to the magnitude of the detection current.

[0027] Based on the second aspect, in an optional implementation manner, the method further includes: within a first time period, controlling the power supply module to output a first power, the starting moment of the first time period being the moment when the power supply module starts to supply power to the APD; within a second time period, controlling the power supply module to output a second power, the starting moment of the second time period being the end moment of the first time period, the power value of the first power being less than the power value of the second power.

[0028] Based on the second aspect, in an optional implementation manner, before controlling the conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD, the method further includes: at the starting moment, controlling the conduction switch to conduct the power supply module and the third branch, the starting moment being the moment when the power supply module starts to supply power to the APD.

[0029] Based on the second aspect, in an optional implementation, before controlling the conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD, the method further includes: at the starting moment, controlling the conduction switch to conduct the power supply module and the fifth branch, and the starting moment is the moment when the power supply module starts to supply power to the APD.

[0030] In a third aspect, an embodiment of the present invention provides an optical network device. The optical network device includes the protection circuit shown in any item of the first aspect above. The optical network device further includes an avalanche photodiode APD. The cathode of the APD is connected to the second output end of the collector of the second triode, and the anode of the APD is connected to the processing module. The APD is configured to receive an optical signal and perform optoelectronic conversion to obtain an electrical signal, and the processing module obtains the electrical signal and is configured to perform signal processing on the electrical signal.

[0031] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium. Computer instructions are stored in the computer-readable storage medium. When the computer instructions run on a computer, the computer is caused to execute the method shown in the second aspect.

[0032] In a fifth aspect, an embodiment of the present invention provides a chip, including a processor. The processor is configured to read and execute a computer program stored in a memory to execute the method shown in the second aspect.

[0033] Optionally, the chip further includes a memory, and the memory is connected to the processor through a circuit or a wire.

[0034] In a sixth aspect, an embodiment of the present invention provides a computer program product. The computer program product includes computer program code. When the computer program code runs on a computer, the computer is caused to execute the method shown in the second aspect.

[0035] In a seventh aspect, an embodiment of the present invention provides a communication system, including an optical line terminal and an optical network unit connected to the optical line terminal. The optical line terminal includes the protection circuit shown in the first aspect above for executing the method shown in the second aspect, and / or, the optical network unit includes the protection circuit shown in the first aspect above for executing the method shown in the second aspect. Description of the Drawings

[0036] Figure 1 It is a structural example diagram of the protection circuit provided by the prior art;

[0037] Figure 2 It is a structural example diagram of the system provided by the present application;

[0038] Figure 3 The first structural example diagram of the protection circuit provided by this application;

[0039] Figure 4 The flowchart of the steps of the first embodiment of the protection method provided by this application;

[0040] Figure 5 The second structural example diagram of the protection circuit provided by this application;

[0041] Figure 6 The third structural example diagram of the protection circuit provided by this application;

[0042] Figure 7 The fourth structural example diagram of the protection circuit provided by this application;

[0043] Figure 8 The fifth structural example diagram of the protection circuit provided by this application;

[0044] Figure 9 The sixth structural example diagram of the protection circuit provided by this application;

[0045] Figure 10 The flowchart of the steps of the second embodiment of the protection method provided by this application;

[0046] Figure 11 The seventh structural example diagram of the protection circuit provided by this application;

[0047] Figure 12 The example diagram of the change in the voltage value of the voltage on the APD provided by this application;

[0048] Figure 13 The structural example diagram of the optical network device provided by this application. Detailed implementation manners

[0049] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

[0050] The terms "first", "second", etc. in the specification, claims and above-mentioned drawings of this application are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments described here can be implemented in an order different from that shown or described here.

[0051] The present application provides a protection circuit, which is used to provide overcurrent protection for different types of APDs, avoiding the damage of different types of APDs due to excessive bias voltage. To better understand the protection circuit provided by the present application, the following first combines Figure 2 to illustrate the structure of the system to which the protection circuit provided by the present application is applied. In this embodiment, the system to which the protection circuit provided by the present application is applied is taken as an example of a passive optical network (PON) for exemplary illustration. Among them, Figure 2 is an exemplary structural diagram of an embodiment of the PON provided by the present application.

[0052] Figure 2 In , the optical line terminal (OLT) 201 is used to provide a network-side interface for the optical access network (OAN). The OLT 201 is connected to the upper-layer network-side devices (such as switches, routers, etc.) and is connected to one or more optical distribution networks (ODNs) 202 at the lower layer.

[0053] The ODN 202 includes a passive optical splitter for optical power distribution, a backbone optical fiber connected between the passive optical splitter and the OLT 201, and a branch optical fiber connected between the passive optical splitter and the optical network unit (ONU) 203.

[0054] When the OLT 201 needs to transmit a downstream optical signal to the ONU 203, the ODN 202 transmits the downstream optical signal from the OLT 201 to each ONU through the passive optical splitter. Similarly, when the ONU 203 needs to transmit an upstream optical signal to the OLT 201, the ODN converges the upstream optical signal from the ONU 203 and then transmits it to the OLT 201.

[0055] The ONU 203 provides a user-side interface for the OAN and is connected to the ODN 202 at the same time. If the ONU 203 is used in the fiber to the home (FTTH) scenario, and the ONU including the user port function is called an optical network termination (ONT). In the present application, the ONU or ONT is uniformly referred to as the optical network unit ONU.

[0056] The protection circuit shown in this application can be set in the OLT 201 to avoid overload during the optoelectronic conversion of the APD when the OLT 201 receives the upstream optical signal from the ONU 203. The protection circuit shown in this application can also be set in the ONU 203 to avoid overload during the optoelectronic conversion of the APD when the ONU 203 receives the downstream optical signal from the OLT 201. The structure of the protection circuit provided by this application will be described below in combination with each embodiment. Embodiment 1

[0057] This embodiment will describe the structure of the protection circuit in combination with Figure 3 shown as follows:

[0058] The protection circuit shown in this embodiment includes a power supply module 301. The input end of the power supply module 301 is connected to the device power supply of the optical network device. The power supply module 301 receives the voltage from the device power supply of the optical network device and converts this voltage into the bias voltage required for the operation of the APD. To achieve normal optoelectronic conversion, the APD requires a relatively high bias voltage. The power supply module 301 can boost the voltage from the device power supply to reach the bias voltage required for the operation of the APD.

[0059] The protection circuit shown in this embodiment further includes a first resistor 303 connected between the output end of the power supply module 301 and the APD 302. For the convenience of description, the resistance value of the first resistor 303 is taken as R1 as an example for illustrative purposes. The first resistor 303 plays a role of current limiting and voltage reduction in the protection circuit to prevent the APD 302 from being overloaded.

[0060] Specifically, when the power supply module 301 supplies power to the APD 302, if the current flowing through the first resistor 303 is I1, then the voltage drop of the first resistor 303 is I1 * R1. It can be seen that the larger the current value of the current I1, the larger the voltage drop of the first resistor 303.

[0061] It can be seen that the voltage output by the power supply module 301 is reduced after being divided by the first resistor 303, so that the bias voltage transmitted to the APD 302 is reduced, thereby avoiding the APD 302 from being overloaded due to receiving an excessive bias voltage and being damaged.

[0062] The protection circuit shown in this embodiment further includes a mirror circuit connected between the first resistor 303 and the APD 302. The mirror circuit specifically includes a first triode 304 and a second triode 305. The first triode 304 and the second triode 305 shown in this embodiment are both PNP type triodes, and the base of the first triode 304 is connected to the base of the second triode 305.

[0063] The connection mode of the mirror circuit and the first resistor 303 may be: the first end of the first resistor 303 is connected to the power supply module 301, and a first branch is connected between the second end of the first resistor 303 and the emitter of the first triode 304. The first branch shown in this embodiment includes one or more resistors. If the first branch includes multiple resistors, this embodiment does not limit the specific connection mode of the multiple resistors included in the first branch. For example, the multiple resistors included in the first branch are connected in series, or in parallel, or in a series-parallel manner.

[0064] For better understanding, this embodiment takes the first branch including a second resistor 306 as an example for illustrative description. For the convenience of description, the resistance value of the second resistor 306 is taken as R2 as an example for illustrative description. The first end of the second resistor 306 is connected to the second end of the first resistor 303, the second end of the second resistor 306 is connected to the emitter of the first triode 304, and the power supply module 301 is connected to the emitter of the first triode 304 via the first resistor 303 and the second resistor 306 in sequence.

[0065] The connection mode of the mirror circuit and the APD 302 may be: the collector of the second triode 305 has a first output terminal 307 and a second output terminal 308 connected in parallel. The first output terminal 307 is connected to the base of the first triode 304, and the second output terminal 308 is connected to the cathode of the APD 302.

[0066] The protection circuit further includes a branch switching module. The branch switching module includes a parallel module 313 and a conduction switch 309. Among them, the parallel module 313 includes two or more parallel branches. This embodiment does not limit the number of parallel branches included in the parallel module 313, as long as the parallel module 313 includes two or more parallel branches and the resistance values of different branches are different.

[0067] This embodiment takes the parallel module 313 including two parallel branches, namely the second branch and the third branch, as an example for illustrative description. The second branch may include one or more resistors, and the third branch may also include one or more resistors. For the description of the resistors included in the second branch and the description of the resistors included in the third branch, please refer to the description of the resistors included in the first branch, and no specific details will be elaborated here.

[0068] For better understanding, this embodiment takes the second branch including a third resistor 310 and the third branch including a fourth resistor 311 as an example for illustrative description. For the convenience of description, the resistance value of the third resistor 310 is R3 and the resistance value of the fourth resistor 311 is R4 as an example for illustrative description.

[0069] The connection method of the branch switching module in the protection circuit is described as follows:

[0070] The first end of the parallel module 313 included in the branch switching module is connected to the emitter of the second triode 305. Specifically, the third resistor 310 and the fourth resistor 311 are in parallel, and the first ends of the third resistor 310 and the fourth resistor 311 are both connected to the emitter of the second triode 305. The second end of the parallel module 313 included in the branch switching module is connected to the conduction switch 309, and this conduction switch 309 is also connected to the power supply module 301 and the processing module 312.

[0071] The connection mode of the second end of the parallel module 313 to the conduction switch 309 can be that the processing module 312 controls the conduction switch 309 to conduct with the second end of the third resistor 310 to realize the connection between the second end of the parallel module 313 and the conduction switch 309. Or, the connection mode of the second end of the parallel module 313 to the conduction switch 309 can also be that the processing module 312 controls the conduction switch 309 to conduct with the second end of the fourth resistor 311 to realize the connection between the second end of the parallel module 313 and the conduction switch 309.

[0072] In this embodiment, the specific switch type of the conduction switch 309 is not limited. As long as this conduction switch 309 can conduct one branch included in the power supply module 301 and the parallel module 313 under the control of the trigger signal sent by the processing module, the conduction switch shown in this embodiment can be a MOS switch circuit, multiple single-pole single-throw switches, a single-pole double-throw switch, or a single-pole multi-throw switch, etc. As long as this conduction switch 309 can realize the on-off of the power supply module 301 and any branch included in the parallel module 313 under the control of the trigger signal from the processing module.

[0073] In this embodiment, by the resistances of the first branch, the second branch, and the third branch, the magnitude of the voltage transmitted to the APD 302 via the collector of the second triode 305 can be adjusted, thereby realizing the over-current protection of the APD 302. The following is a specific description in combination with Figure 4 as shown, where Figure 4 is the step flowchart of the first embodiment of the protection method provided by this application.

[0074] Step 401: At the starting moment of power supply, the conduction switch conducts the power supply module and the third branch.

[0075] If at the starting moment of power supply, the conduction switch 309 has conducted the power supply module 301 and the third branch, then the conduction switch maintains the state of conducting the power supply module and the third branch unchanged.

[0076] If, at the starting moment of power supply, the conducting switch 309 conducts the power supply module 301 and the second branch, or the conducting switch 309 does not conduct any branch included in the power supply module 301 and the parallel module 313, the processing module sends a trigger signal to the conducting switch to instruct the conducting switch to conduct the power supply module and the third branch.

[0077] Specifically, the processing module 312 controls the conducting switch 309 to conduct with the second end of the fourth resistor 311, so as to realize the conduction between the power supply module 301 and the third branch, thereby realizing the overcurrent protection of the APD 302 at the starting moment of power supply. Wherein, the starting moment of power supply refers to the moment when the power supply module 301 starts to supply power to the APD 302.

[0078] The following explains the reason why the conducting switch 309 conducting the power supply module 301 and the third branch can effectively avoid the overcurrent of the APD 302 at the starting moment of power supply:

[0079] In this embodiment, the ratio between the resistance value of the third branch and the resistance value of the first branch is the first ratio K1. As Figure 3 shown in the example, the first ratio K1 = the resistance value of the third branch / the resistance value of the first branch = R3 / R2. The ratio between the resistance value of the second branch and the resistance value of the first branch is the second ratio k2. As Figure 3 shown in the example, the second ratio k2 = the resistance value of the second branch / the resistance value of the first branch = R4 / R2.

[0080] This embodiment is exemplarily described by taking the first ratio being greater than the second ratio as an example;

[0081] Specifically, the power supply module 301 outputs a first current I1, the collector of the first triode 304 outputs a detection current I3, and the collector of the second triode 305 outputs a second current I2. The second current I2 output by the collector of the second triode 305 can supply power to the APD 302 to ensure the normal optoelectronic conversion of the APD 302.

[0082] According to the principle of the mirror circuit, when the conducting switch 309 conducts the power supply module 301 and the third branch, I3 / I2 = the first ratio K1. When the conducting switch 309 conducts the power supply module 301 and the second branch, I3 / I2 = the second ratio K2.

[0083] When the second current I2 generated by the optoelectronic conversion of the APD302 is constant, the larger the ratio of I3 / I2, the larger the detection current I3 at the collector of the first triode 304. Since I1 = I2 + I3, it can be seen that the larger the detection current I3, the larger I1 will be. From the above description, the corresponding voltage drop generated by the voltage division of the first resistor 303 is I1*R1. It can be seen that the larger I1 is, the larger the voltage drop of the first resistor 303 is, thereby reducing the bias voltage transmitted to the APD302 and realizing the overcurrent protection of the APD302. In this embodiment, the specific values of the first ratio K1 and the second ratio K2 are not limited, as long as the first ratio K1 is greater than the second ratio K2.

[0084] In this embodiment, the values of the first ratio K1 and the second ratio K2 can be determined according to the magnitude of the bias voltage required for the optoelectronic conversion of the APD302. For example, the first ratio K1 is within a preset range. When the value of the first ratio K1 is the maximum value of the preset range, the bias voltage transmitted to the APD302 can satisfy the normal optoelectronic conversion of the APD302. When the value of the first ratio K1 is the minimum value of the preset range, the APD302 will not be overloaded. For example, the preset range can be greater than 1 and less than or equal to 5. For the description of the value of the second ratio K2, please refer to the description of the first ratio K1, and the details will not be elaborated here. For example, the value of the second ratio K2 is 1.

[0085] In this embodiment, at the starting moment of power supply, to avoid the optical power of the optical signal received by the APD302 being too large at the starting moment of power supply, which may cause the bias voltage of the APD302 to be too large and damage the APD302, the conduction switch 309 conducts the power supply module 301 and the third branch at the starting moment of power supply. Since the value of the first ratio K1 is relatively large, the voltage division of the first resistor 303 will be relatively large, thereby reducing the magnitude of the bias voltage transmitted to the APD302 and avoiding the overload of the APD302 at the starting moment of power supply.

[0086] Step 401 shown in this embodiment is an optional step. In other examples, at the starting moment of power supply, as long as it is ensured that the conduction switch conducts one of the branches included in the parallel module to ensure that the power supply module can supply power to the APD302.

[0087] Step 402, the processing module determines whether the voltage value of the APD is greater than or equal to a preset value. If so, step 403 is executed; if not, step 404 is executed.

[0088] First, the optional situations of the execution timing of step 402 shown in this embodiment are described:

[0089] Case 1

[0090] Step 402 shown in this embodiment can be executed after step 401. It can be seen that at the starting moment of power supply, after the conducting switch turns on the power supply module and the third branch, step 402 can be executed to determine whether the voltage value of APD302 is greater than or equal to a preset value.

[0091] Case 2

[0092] Step 402 shown in this embodiment can be executed at the starting moment of power supply to determine whether the voltage value of APD302 is greater than or equal to a preset value at the starting moment of power supply.

[0093] Case 3

[0094] Step 402 shown in this embodiment can be executed at any moment during the process of the power supply module 301 supplying power to APD302, so as to avoid a sudden change in the optical power of the optical signal received by APD302, resulting in APD overload.

[0095] For example, the processing module can preset a detection period in advance. The processing module can execute step 402 shown in this embodiment every other detection period. The duration of this detection period is not limited in this embodiment. Another example is that the processing module can randomly execute step 402 shown in this embodiment during the process of the power supply module 301 supplying power to APD302.

[0096] The following gives an exemplary description of several optional solutions for the processing module to determine whether the voltage value of APD302 is greater than or equal to a preset value:

[0097] Solution 1

[0098] The structure shown in this solution can be referred to Figure 5 As shown, the processing module includes a processor 502 and a detector 501. The processor 502 is respectively connected to the power supply module 301, the conducting switch 309, and the detector 501. The detector 501 is connected between the processor 502 and the cathode of the APD302. Specifically, the detector 501 is connected between the APD cathode and the second output terminal 308 of the collector of the second triode 305.

[0099] The detector 501 is used to detect the voltage value of the APD302. The specific type of this detector 501 is not limited in this embodiment. For example, the detector 501 can be an analog to digital converter (ADC), and the detector 501 can transmit the detected voltage value of the APD302 to the processor 502.

[0100] The processor 502 prestores the preset value, and the processor 502 determines whether the voltage value of the APD 302 from the detector 501 is greater than or equal to the preset value. In this embodiment, the device type of the processor 502 is not limited. For example, the processor 502 may be one or more field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), system on chips (SoCs), central processor units (CPUs), network processors (NPs), digital signal processing circuits (DSPs), micro controller units (MCUs), programmable logic devices (PLDs), or other integrated chips, which are not specifically limited in this embodiment.

[0101] Solution 2

[0102] In Solution 1, the processor and the detector included in the processing module are taken as two independent devices for illustration. In this method, the processor and the detector shown may be the same device. For example, the processor may be an ASIC, and the ASIC can implement the functions of the detector in Solution 1.

[0103] Solution 3

[0104] As Figure 6 shown, the processing module shown in this solution also includes a processor 503 and a comparator 601. For the description of the processor 503, please refer to Solution 1 shown above, and details are not repeated here.

[0105] The input end of the comparator 601 shown in this solution is connected to the cathode of the APD 302, the output end of the comparator 601 is connected to the processor 503, and the comparator 601 is also connected to a reference voltage source 602. The reference voltage source 602 is used to transmit a reference voltage to the comparator 601, and the voltage value of the reference voltage is the preset value.

[0106] If the comparator 601 determines that the voltage value of the APD 302 is greater than or equal to the preset value, it sends a first indication message to the processor 503, and the processor 503 determines that the voltage value of the APD 302 is greater than or equal to the preset value according to the first indication message. If the comparator 601 determines that the voltage value of the APD 302 is less than the preset value, it sends a second indication message to the processor 503, and the processor 503 determines that the voltage value of the APD 302 is less than the preset value according to the second indication message.

[0107] Solution 4

[0108] As Figure 7 shown, the processing module shown in this solution includes a detector 701 and a processor 702. For the description of the detector 701 and the processor 702, please refer to Solution 1 or Solution 2, and details are not elaborated here.

[0109] The detector 701 shown in this solution is respectively connected to the processor 702 and the collector of the first triode 304. The detector 701 is used to detect the magnitude of the detection current I3 output by the collector of the first triode 304 and send the current value of the detection current I3 to the processor 702.

[0110] The processor 702 determines the voltage value of the APD 302 according to the magnitude of the detection current I3. The specific process may be as follows:

[0111] First, as shown in step 401, the conduction switch 309 is in a state of conducting the power supply module 301 and the fourth resistor 311, so I3 / I2 = the first ratio K1. When the processor 702 has obtained the detection current I3, I2 can be determined, where I2 = I3 / the first ratio K1. I1 can also be determined, where I1 = I2 + I3.

[0112] Second, the processor 702 determines , where, is the voltage value of the APD 302, U1 is the voltage output by the power supply module 301, U2 is the voltage of the first resistor 303 = I1 * R1. If the conduction switch has conducted the power supply module 301 and the third resistor 310, then U3 = I3 * R3. If the conduction switch has conducted the power supply module 301 and the fourth resistor 311, then U3 = I3 * R4, or U3 = I3 * R2.

[0113] Third, the processor 702 pre-stores the preset value, and the processor 702 can then determine whether the voltage value of the APD 302 is greater than or equal to the preset value.

[0114] Step 403: The processing module controls the conduction switch to conduct the power supply module and the third branch.

[0115] In this embodiment, when the processing module determines that the voltage value of the APD 302 is greater than or equal to the preset value, it indicates that the optical signal received by the current APD 302 is a large optical signal. Here, the large optical signal means that the optical power of the optical signal is greater than the threshold. When the APD 302 receives this large optical signal for photoelectric conversion, it is prone to overload. In this embodiment, the conduction switch 309 is controlled to conduct the power supply module 301 and the third branch, thereby reducing the magnitude of the bias voltage transmitted to the APD 302 and effectively avoiding overload of the APD 302.

[0116] If, when the processing module determines that the voltage value of the APD 302 is greater than or equal to the preset value, the power supply module and the third branch are in a conducting state, then the processing module does not need to switch the on / off state of the current conduction switch, and only needs to maintain the conducting state of the power supply module and the third branch.

[0117] Step 404: The processing module controls the conduction switch to conduct the power supply module and the second branch.

[0118] When the processing module determines that the voltage value of the APD 302 is less than the preset value, it indicates that the optical signal received by the current APD 302 is a small optical signal. Here, the small optical signal means that the optical power of the optical signal is less than or equal to the threshold. When the APD 302 receives this small optical signal for photoelectric conversion, it is not prone to overload. When the APD 302 is not overloaded, the processing module can control the conduction switch 309 to conduct the power supply module 301 and the second branch, which can increase the voltage value transmitted to the APD 302 as much as possible to improve the photoelectric conversion efficiency of the APD 302.

[0119] If, when the processing module determines that the voltage value of the APD 302 is less than the preset value, the power supply module and the second branch are in a conducting state, then the processing module does not need to switch the on / off state of the current conduction switch, and only needs to maintain the conducting state of the power supply module and the second branch.

[0120] Step 405: At the end of power supply, the conduction switch conducts the power supply module and the third branch.

[0121] The end of power supply shown in this embodiment means that the optical signal sent to the APD 302 has been disconnected. For example, if the protection circuit shown in this embodiment is set in the ONU, then the end of power supply means the moment when the OLT no longer sends a downstream optical signal to the ONU. Another example is that if the protection circuit is set in the OLT, then the end of power supply means the moment when the ONU no longer sends an upstream optical signal to the OLT.

[0122] If the step executed by the processing module is step 403 before the power supply end moment, at the power supply end moment, the conduction switch maintains the conduction state of the power supply module and the third branch unchanged. If the step executed by the processing module is step 404 before the power supply end moment, at the power supply end moment, the processing module controls the conduction switch to conduct the power supply module and the third branch.

[0123] At the power supply end moment, the conduction switch 309 conducts the power supply module 301 and the third branch, which can effectively ensure that in the case where the APD 302 receives an optical signal again, the overload protection of the APD 302 can be effectively realized. For specific descriptions, please refer to step 401, and no further details will be elaborated here.

[0124] In other examples, at the power supply end moment, the processing module can return to execute step 402. If the processing module determines through step 402 that the voltage value of the APD is greater than or equal to the preset value, at the power supply end moment, the conduction switch conducts the power supply module and the third branch, so that when the APD receives an optical signal next time, the power supply module supplies power to the APD through the third branch.

[0125] If the processing module determines through step 402 that the voltage value of the APD is less than the preset value, at the power supply end moment, the conduction switch conducts the power supply module and the second branch, so that when the APD receives an optical signal next time, the power supply module supplies power to the APD through the second branch.

[0126] As can be seen from this embodiment, the processing module can control the conduction switch to conduct one of the branches of the power supply module and the parallel module according to the magnitude of the bias voltage of the APD, that is, when the voltage value of the APD 302 is greater than or equal to the preset value, the branch conducted by the conduction switch can reduce the bias voltage transmitted to the APD 302 to avoid the overload of the APD 302. When the voltage value of the APD 302 is less than the preset value, the branch conducted by the conduction switch can increase the magnitude of the bias voltage transmitted to the APD 302, thus effectively ensuring that the APD 302 can perform photoelectric conversion normally.

[0127] It can be seen that even for different types of APDs, according to the different requirements of the APD for the bias voltage, the conduction switch can conduct the branches with different resistance values in the power supply module and the parallel module to ensure that when the optical power of the optical signal received by the APD is too large, there will be no overload situation, and it can also ensure that the APD can perform photoelectric conversion normally. Embodiment 2

[0128] Based on Embodiment 1, the protection circuit provided in this embodiment can better provide overload protection for the APD. In the case where the APD receives an optical signal with the same optical power magnitude, the protection circuit shown in Embodiment 2 can further reduce the possibility of APD overload.

[0129] As Figure 8 shown, the protection circuit shown in this embodiment includes a power supply module 801, a first resistor 802, a mirror circuit 803, a branch switching module 804, and a processing module 805. For specific descriptions, please refer to those shown in Embodiment 1 and will not be elaborated in this embodiment.

[0130] The protection circuit shown in this embodiment further includes a fifth resistor 807 and a field effect transistor MOS806. For ease of explanation, the resistance value of the fifth resistor 807 is taken as R5 as an example for exemplary illustration below.

[0131] The collector of the second triode 808 included in the mirror circuit 803 has a first output terminal, a second output terminal, and a third output terminal connected in parallel. For the descriptions of the first output terminal and the second output terminal, please refer to those shown in Embodiment 1 and will not be elaborated in this embodiment. The third output terminal is connected to the branch switching module 804.

[0132] The second output terminal of the collector of the second triode 808 is respectively connected to the source of the MOS806 and the first end of the fifth resistor 807. The drain of the MOS806 is grounded. The gate of the MOS806 and the second end of the fifth resistor 807 are respectively connected to the cathode of the APD809. For the specific description of the APD809, please refer to those shown in Embodiment 1 and will not be elaborated.

[0133] The function of the MOS806 shown in this embodiment is described below:

[0134] This embodiment takes the MOS806 as a specific N-type metal-oxide-semiconductor (NMOS) transistor as an example for description. In other examples, the MOS806 can also be a P-type metal-oxide-semiconductor (PMOS) transistor.

[0135] In this embodiment, if the voltage drop across the fifth resistor 807 is greater than or equal to the conduction threshold, the MOS 806 conducts. Among them, the voltage drop across the fifth resistor 807 is I2 * R5, and the I2 is the current output by the collector of the second triode 808. When the MOS 806 conducts, the first current I1 output by the power supply module 801 increases. The voltage drop across the first resistor 802 = I1 * R1. It can be seen that when I1 increases, the voltage drop across the first resistor 802 increases, and the voltage division of the first resistor 802 increases, resulting in a decrease in the bias voltage transmitted to the APD 809, thereby avoiding damage to the APD 809 due to overload. If the voltage drop across the fifth resistor 807 is less than the conduction threshold, the MOS 806 is cut off, so that when the APD 809 is not overloaded, the bias voltage transmitted to the APD 809 is increased to improve the efficiency of the APD 809 for optoelectronic conversion.

[0136] It can be seen that as shown in this embodiment, the bias voltage transmitted to the APD can be further reduced through the conducting MOS, avoiding the situation that the APD is damaged due to overload. Embodiment Three

[0137] This embodiment combines Figure 9 to illustrate another structure of the protection circuit as shown:

[0138] The protection circuit shown in this embodiment includes a power supply module 901, a mirror circuit 903, a processing module 904, and a first resistor 905. For specific descriptions, please refer to those shown in Embodiment One and will not be elaborated in this embodiment.

[0139] The first end of the first resistor 905 is connected to the power supply module 901, and a fourth branch is connected between the second end of the first resistor 905 and the emitter of the second triode 906 included in the mirror circuit 903.

[0140] The fourth branch shown in this embodiment includes one or more resistors. For the description of the manner in which the fourth branch includes one or more resistors, please refer to the description of the first branch including one or more resistors shown in Embodiment One, and no specific limitation is made in this embodiment.

[0141] For better understanding, this embodiment takes the fourth branch including a sixth resistor 908 as an example for illustrative description. For ease of description, the resistance value of the sixth resistor 908 is taken as R6 for illustrative description. It can be seen that the first end of the sixth resistor 908 is connected to the second end of the first resistor 905, and the second end of the sixth resistor 908 is connected to the emitter of the second triode 906. The power supply module 901 is connected to the emitter of the second triode 906 via the first resistor 905 and the sixth resistor 908.

[0142] For the description of the connection method between the second triode 906 and the APD 909 shown in this embodiment, please refer to the first embodiment, and specific details will not be elaborated in this embodiment.

[0143] The protection circuit further includes a branch switching module, and the branch switching module includes a parallel module 910 and a conduction switch 911. Among them, the parallel module 910 includes two or more parallel branches. In this embodiment, the number of parallel branches included in the parallel module 910 is not limited, as long as the parallel module 910 includes two or more parallel branches and the resistance values of different branches are different.

[0144] In this embodiment, an example is given where the parallel module 910 includes two parallel branches, namely the fifth branch and the sixth branch. The fifth branch may include one or more resistors, and the sixth branch may also include one or more resistors. For the description of the resistors included in the fifth branch and the sixth branch, please refer to the description of the resistors included in the first branch, and specific details will not be elaborated.

[0145] For better understanding, in this embodiment, an example is given where the fifth branch includes a seventh resistor 912 and the sixth branch includes an eighth resistor 913. For ease of explanation, hereinafter, an example is given where the resistance value of the seventh resistor 912 is R7 and the resistance value of the eighth resistor 913 is R8.

[0146] The following describes the connection method of the branch switching module in the protection circuit:

[0147] The first end of the parallel module 910 included in the branch switching module is connected to the emitter of the first triode 907. Specifically, the seventh resistor 912 and the eighth resistor 913 are in parallel, and the first ends of the seventh resistor 912 and the eighth resistor 913 are both connected to the emitter of the first triode 907.

[0148] The second end of the parallel module 910 included in the branch switching module is connected to the conduction switch 911, and the conduction switch 911 is also connected to the power supply module 901 and the processing module 904.

[0149] The connection method between the second end of the parallel module 910 and the conduction switch 911 may be that the processing module 904 controls the conduction switch 911 to conduct with the second end of the seventh resistor 912 to realize the connection between the second end of the parallel module 910 and the conduction switch 911. Or, the connection method between the second end of the parallel module 910 and the conduction switch 911 may also be that the processing module 904 controls the conduction switch 911 to conduct with the second end of the eighth resistor 913 to realize the connection between the second end of the parallel module 910 and the conduction switch 911.

[0150] For the description of the specific switch type of the conduction switch 911 shown in this embodiment, please refer to Embodiment 1, and no further elaboration will be made in this embodiment.

[0151] In this embodiment, by the resistance values of the fourth branch, the fifth branch, and the sixth branch, the magnitude of the bias voltage transmitted to the APD 909 via the collector of the first triode 907 can be adjusted, thereby achieving overcurrent protection for the APD 909. The following will specifically describe with reference to Figure 10 as shown, where Figure 10 is the flowchart of the steps of the second embodiment of the protection method provided by this application.

[0152] Step 1001: At the starting moment of power supply, the conduction switch conducts the power supply module and the fifth branch.

[0153] If at the starting moment of power supply, the conduction switch 911 has already conducted the power supply module 901 and the fifth branch, then the conduction switch maintains the state of conducting the power supply module and the fifth branch unchanged.

[0154] If at the starting moment of power supply, the conduction switch 911 conducts the power supply module 901 and the sixth branch, or the conduction switch 911 does not conduct any branch included in the power supply module 901 and the parallel module 910, then the processing module sends a trigger signal to the conduction switch to instruct the conduction switch to conduct the power supply module and the fifth branch.

[0155] Specifically, the processing module 904 controls the conduction switch 911 to conduct with the second end of the seventh resistor 912, so as to realize the conduction of the power supply module 901 and the fifth branch, thereby achieving overcurrent protection for the APD 909 at the starting moment of power supply. Wherein, this starting moment of power supply refers to the moment when the power supply module 901 starts to supply power to the APD 909.

[0156] The following explains the reason why the conduction switch 911 conducting the power supply module 901 and the fifth branch can effectively avoid overcurrent of the APD 909 at the starting moment of power supply:

[0157] The ratio between the resistance value of the fifth branch and the resistance value of the fourth branch shown in this embodiment is the third ratio K3. As can be seen from the example shown in Figure 9 the third ratio K3 = resistance value of the fifth branch / resistance value of the fourth branch = R7 / R6.

[0158] The ratio between the resistance value of the sixth branch and the resistance value of the fourth branch is the fourth ratio K4. As can be seen from the example shown in Figure 9 the fourth ratio K4 = resistance value of the sixth branch / resistance value of the fourth branch = R8 / R6.

[0159] This embodiment is exemplarily described by taking the case where the third ratio K3 is greater than the fourth ratio K4 as an example.

[0160] Specifically, the power supply module 901 outputs a first current I1, the collector of the first triode 907 outputs a detection current I3, and the collector of the second triode 906 outputs a second current I2. The second current I2 output by the collector of the second triode 906 can supply power to the APD 909 to ensure normal photoelectric conversion of the APD 909.

[0161] According to the principle of the mirror circuit, when the conduction switch 911 conducts the power supply module 901 and the fifth branch, I3 / I2 = the third ratio K3. When the conduction switch 911 conducts the power supply module 901 and the sixth branch, I3 / I2 = the fourth ratio K4.

[0162] When the second current I2 generated by the photoelectric conversion of the APD 909 is constant, the larger the ratio of I3 / I2, the larger the detection current I3 consumed by the collector of the first triode 907. Since I1 = I2 + I3, it can be seen that the larger the detection current I3, the larger I1 will be. From the above description, the corresponding voltage drop generated by the voltage division effect of the first resistor 905 is I1*R1. It can be seen that the larger I1 is, the larger the voltage drop of the first resistor 905 is, thereby reducing the bias voltage transmitted to the APD 909 and realizing overcurrent protection for the APD 909. In this embodiment, the specific values of the third ratio K3 and the fourth ratio K4 are not limited, as long as the third ratio K3 is greater than the fourth ratio K4.

[0163] This embodiment can determine the values of the third ratio K3 and the fourth ratio K4 according to the value of the bias voltage required for the photoelectric conversion of the APD 909. For the description of the specific values, reference can be made to the description of the values of the first ratio K1 and the second ratio K2 shown in Embodiment 1, and no detailed description will be given in this embodiment.

[0164] In this embodiment, at the starting moment of power supply, to avoid the optical power of the optical signal received by the APD 909 being too large at the starting moment of power supply, which may cause the bias voltage of the APD 909 to be too large and damage the APD 909, at the starting moment of power supply, the conduction switch 911 conducts the power supply module 901 and the fifth branch. Since the value of the third ratio K3 is relatively large, the voltage division of the first resistor 905 will be larger, thereby reducing the magnitude of the bias voltage transmitted to the APD 909 and avoiding the overload of the APD 909 at the starting moment of power supply.

[0165] Step 1001 shown in this embodiment is an optional step. In other examples, at the starting moment of power supply, as long as it is ensured that the conduction switch conducts with one branch included in the parallel module to ensure that the power supply module can supply power to the APD909.

[0166] Step 1002, the processing module determines whether the voltage value of the APD is greater than or equal to a preset value. If so, step 1003 is executed; if not, step 1004 is executed.

[0167] First, the optional cases of the execution timing of step 1002 shown in this embodiment are described:

[0168] Case 1

[0169] Step 1002 shown in this embodiment can be executed after step 1001 is executed. It can be seen that at the starting moment of power supply, after the processing module controls the conduction switch to conduct the power supply module and the fifth branch, step 1002 can be executed to determine whether the voltage value of the APD is greater than or equal to the preset value.

[0170] Case 2

[0171] Step 1002 shown in this embodiment can be executed at the starting moment of power supply to determine whether the voltage value of the APD is greater than or equal to the preset value at the starting moment of power supply.

[0172] Case 3

[0173] Step 1002 shown in this embodiment can be executed at any moment during the process of the power supply module 901 supplying power to the APD to avoid a sudden change in the optical power of the optical signal received by the APD, resulting in APD overload. For specific descriptions, please refer to what is shown in Embodiment 1 and will not be elaborated here.

[0174] For the description of the specific manner in which the processing module shown in this embodiment determines whether the voltage value of the APD909 is greater than or equal to the preset value, please refer to what is shown in Embodiment 1 and will not be elaborated in this embodiment.

[0175] Step 1003, the processing module controls the conduction switch to conduct the power supply module and the fifth branch.

[0176] For the execution process shown in step 1003 of this embodiment, please refer to the description of the process in which the conduction switch conducts the power supply module and the third branch in step 403 of Embodiment 1 and will not be elaborated in this embodiment.

[0177] Step 1004, the processing module controls the conduction switch to conduct the power supply module and the sixth branch.

[0178] For the execution process shown in step 1004 in this embodiment, please refer to the description of the process of turning on the switch to turn on the power supply module and the second branch shown in step 404 in Embodiment 1, and details are not described in this embodiment specifically.

[0179] Step 1005: At the power supply end moment, turn on the switch to turn on the power supply module and the fifth branch.

[0180] For the description of the power supply end moment, please refer to step 405 in Embodiment 1, and details are not described in this embodiment specifically.

[0181] If the step executed by the processing module before the power supply end moment is step 1003, then at the power supply end moment, the switch maintains the on state of the power supply module and the fifth branch unchanged. If the step executed by the processing module before the power supply end moment is step 1004, then at the power supply end moment, the processing module controls the switch to turn on the power supply module and the fifth branch.

[0182] In other examples, at the power supply end moment, the processing module can return to execute step 1002. If the processing module determines through step 1002 that the voltage value of the APD is greater than or equal to the preset value, then at the power supply end moment, the switch turns on the power supply module and the fifth branch, so that when the APD receives an optical signal next time, the power supply module supplies power to the APD through the fifth branch.

[0183] If the processing module determines through step 1002 that the voltage value of the APD is less than the preset value, then at the power supply end moment, the switch turns on the power supply module and the sixth branch, so that when the APD receives an optical signal next time, the power supply module supplies power to the APD through the sixth branch.

[0184] Optionally, for the structure of the protection circuit shown in this embodiment, reference can also be made to Figure 11 as shown in Figure 11 as shown, the protection circuit shown in this embodiment includes a power supply module 1101, a first resistor 1102, a mirror circuit 1103, a branch switching module 1104, and a processing module 1105. For specific descriptions, please refer to Embodiment 3, and details are not described in this embodiment specifically.

[0185] The protection circuit shown in this embodiment further includes a fifth resistor 1107 and a field effect transistor MOS1106. For ease of description, the resistance value of the fifth resistor 1107 is taken as R5 as an example for illustrative purposes. For specific descriptions of the fifth resistor 1107 and the field effect transistor MOS1106 shown in this embodiment, please refer to Embodiment 2, and details are not described in this embodiment specifically.

[0186] It can be seen that, as shown in this embodiment, the turned-on MOS1106 can further reduce the bias voltage transmitted to the APD, avoiding damage to the APD when it receives an optical signal with too high optical power, thereby providing a more secure overload protection for the APD.

[0187] As can be seen from this embodiment, the processing module can control the turned-on switch to turn on one branch of the power supply module and the parallel module according to the magnitude of the bias voltage of the APD. That is, when the voltage value of the APD is greater than or equal to the preset value, the branch turned on by the turned-on switch can reduce the bias voltage transmitted to the APD to avoid overload of the APD. When the voltage value of the APD is less than the preset value, the branch turned on by the turned-on switch can increase the magnitude of the bias voltage transmitted to the APD, thus effectively ensuring that the APD can perform normal optoelectronic conversion.

[0188] It can be seen that even for different types of APDs, according to the different requirements of the APD for the working bias voltage, the turned-on switch can turn on the branches with different resistance values in the power supply module and the parallel module to ensure that when the optical power of the optical signal received by the APD is too high, no overload will occur, and it can also ensure that the APD can perform normal optoelectronic conversion. Embodiment 4

[0189] Based on any one of Embodiments 1 to 3, the following specifically describes how the above embodiments can avoid APD overload in combination with Figure 12 shown as follows:

[0190] Figure 12 In the shown coordinate system, the abscissa represents time, and the unit can be seconds, and the ordinate represents the voltage value of the APD, and the unit can be volts. Figure 12 The curve 1201 in represents the voltage value of the bias voltage of the APD shown in the existing solution as the time of power supply from the power supply module to the APD changes, and the curve 1202 represents the voltage value of the bias voltage of the APD shown in this application as the time of power supply from the power supply module to the APD changes. Among them, the moment t0 is the starting moment of power supply shown in the above embodiment. For specific description, please refer to the description of the starting moment of power supply in Embodiment 1, and details will not be elaborated here.

[0191] Figure 12 The shown voltage value VM is the threshold voltage of the APD. Among them, this threshold voltage means that if the voltage value of the bias voltage transmitted from the power supply module to the APD is greater than or equal to this threshold voltage, the APD will be overloaded. If the voltage value of the bias voltage transmitted from the power supply module to the APD is less than this threshold voltage, the APD is in a safe state and will not be overloaded.

[0192] As shown in the existing solution, if the power supply module starts to supply power to the APD and the optical power of the optical signal received by the APD is too high, the voltage value transmitted by the power supply module to the APD exceeds the threshold voltage VM, resulting in APD overload. Continuing as Figure 12 shown by curve 1201, between t0 and t1 when the power supply module supplies power to the APD, the voltage value of the threshold voltage transmitted by the power supply module to the APD has exceeded the threshold voltage of the APD, resulting in damage to the APD due to overload.

[0193] As shown in the present application, if the optical power of the optical signal received by the APD is too high, the processing module can control the conduction switch to conduct a branch included in the power supply module and the parallel module shown in any of the above embodiments, thereby reducing the voltage value transmitted to the APD. For specific descriptions, please refer to the description of the adjustment method of the branch switching module shown in Embodiments 1 to 3, and details will not be elaborated here. Continuing as Figure 12 shown by curve 1202, between t0 and t1 when the power supply module supplies power to the APD, the adjustment process shown in any of Embodiments 1 to 3 is adopted, resulting in a decrease in the voltage value of the bias voltage transmitted by the power supply module to the APD, thereby ensuring that the voltage of the APD does not exceed the threshold voltage.

[0194] The processing module shown in this embodiment can further reduce the possibility of APD overload and effectively improve the safety of the APD. As shown in this embodiment, within the first time period, the processing module controls the power supply module to output the first power, and within the second time period, the processing module controls the power supply module to output the second power. The start time of the second time period is the end time of the first time period, and the power value of the first power is less than the power value of the second power.

[0195] Continuing to refer to Figure 12 shown, curve 1201 is shown in the existing solution. Since the power output by the power supply module is fixed, it is easy to have an APD overload situation at time t0 to t1. Curve 1202 is the solution shown in this embodiment. The processing module controls the power supply module to output a voltage with a lower power value (i.e., the first power value) within the time period when starting to supply power to the APD (i.e., the first time period), thereby effectively avoiding an APD overload situation within the first time period. Within the second time period, the processing module controls the power supply module to output a voltage with a higher power value (i.e., the second power value), thereby effectively improving the efficiency of the APD for optoelectronic conversion within the second time period. Embodiment 5

[0196] This embodiment provides an optical network device, which includes the protection circuit shown in any one of Embodiments 1 to 4 of the above embodiments. The optical network device shown in this embodiment can be an OLT or an ONU, which is not specifically limited in this embodiment. The following will be combined with Figure 13 shown to illustrate the structure of the optical network device shown in this embodiment:

[0197] This embodiment takes the structure of the protection circuit included in the optical network device as Figure 3 shown as an example for illustration. This protection circuit is connected to the cathode 302 of the APD 302. Specifically, the cathode of the APD 302 is connected to the second output terminal of the collector of the second triode 305.

[0198] The anode of the APD 302 is connected to the amplifier 1301. The type of this amplifier 1301 is not limited in this embodiment, as long as the amplifier 1301 can amplify the power of the electrical signal from the APD 302. For example, the amplifier 1301 can be a trans-impedance amplifier (TIA).

[0199] The protection circuit shown in this embodiment is also connected to the signal strength measurement module 1302. Specifically, the collector of the first triode 304 included in the protection circuit is connected to the signal strength measurement module 1302. The signal strength measurement module 1302 is used to measure the received signal strength indication (RSSI) according to the current from the collector of the first triode 304, and monitor the line for transmitting optical signals through this RSSI.

[0200] The APD 302 is used to receive optical signals and perform optoelectronic conversion to obtain electrical signals. The amplifier 1301 is used to obtain the electrical signals from the APD 302 and amplify the electrical signals to obtain amplified electrical signals. The processing module is used to obtain the amplified electrical signals from the amplifier 1301 and perform signal processing on the amplified electrical signals.

[0201] This embodiment takes the processing module 312 as an example for illustrative description to implement signal processing on the amplified electrical signals from the amplifier 1301. In other examples, the optical network device may further include a signal processing module independent of the processing module 312. This signal processing module is connected to the amplifier 1301 and is used to implement signal processing on the amplified electrical signals from the amplifier 1301. For the description of the type of the signal processing module, reference can be made to the description of the processor shown in Embodiment 1, which will not be elaborated here.

[0202] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A protection circuit for protecting an avalanche photodiode (APD), characterized in that, the protection circuit includes a power supply module, a mirror circuit, a processing module, and a branch switching module; the mirror circuit includes a first triode and a second triode, the base of the first triode is connected to the base of the second triode, the collector of the second triode has a first output terminal and a second output terminal, the first output terminal is connected to the base of the second triode, and the second output terminal is used to connect to the APD; the branch switching module includes at least two parallel branches and a conduction switch, the first ends of the at least two parallel branches are connected to the first emitter, and the second emitter is connected to the power supply module, wherein, the first emitter is the emitter of the first triode, the second emitter is the emitter of the second triode, or, the first emitter is the emitter of the second triode, and the second emitter is the emitter of the first triode; the conduction switch is connected between the power supply module and the second ends of the at least two parallel branches, the processing module is connected to the conduction switch, and the processing module is used to control the conduction switch to conduct one of the power supply module and the at least two parallel branches, and among the at least two parallel branches, the resistances of different branches are different.

2. The protection circuit according to claim 1, characterized in that, the first emitter is the emitter of the second triode, the second emitter is the emitter of the first triode, and the protection circuit includes a first branch connected between the second emitter and the power supply module; the at least two parallel branches include a second branch and a third branch, the ratio of the resistance of the third branch to the resistance of the first branch is a first ratio, the ratio of the resistance of the second branch to the resistance of the first branch is a second ratio, and the first ratio is greater than the second ratio; if the processing module determines that the voltage value of the APD is greater than or equal to a preset value, then the processing module controls the conduction switch to conduct the power supply module and the third branch, and if the processing module determines that the voltage value of the APD is less than the preset value, then the processing module controls the conduction switch to conduct the power supply module and the second branch.

3. The protection circuit according to claim 1, characterized in that, the first emitter is the emitter of the first triode, the second emitter is the emitter of the second triode, and the protection circuit includes a fourth branch connected between the second emitter and the power supply module; the at least two parallel branches include a fifth branch and a sixth branch, the ratio of the resistance of the fifth branch to the resistance of the fourth branch is a third ratio, the ratio of the resistance of the sixth branch to the resistance of the fourth branch is a fourth ratio, and the third ratio is greater than the fourth ratio; If the processing module determines that the voltage value of the APD is greater than or equal to a preset value, the processing module controls the conduction switch to conduct the power supply module and the fifth branch. If the processing module determines that the voltage value of the APD is less than the preset value, the processing module controls the conduction switch to conduct the power supply module and the sixth branch.

4. The protection circuit according to claim 2 or 3, wherein, the processing module is configured to determine the voltage value of the APD to determine whether the voltage value of the APD is greater than or equal to the preset value.

5. The protection circuit according to claim 4, wherein, the processing module is connected between the second output terminal and the cathode of the APD.

6. The protection circuit according to claim 2 or 3, wherein, the processing module is connected to the collector of the first triode, the processing module is further configured to detect the magnitude of the detection current output by the collector of the first triode, and the processing module is configured to determine the voltage value of the APD according to the magnitude of the detection current.

7. The protection circuit according to any one of claims 1 to 3, wherein, the protection circuit further includes a resistor and a MOS field effect transistor. The second output terminal of the collector of the second triode is respectively connected to the source of the MOS and the first end of the resistor. The drain of the MOS is grounded, and the gate of the MOS and the second end of the resistor are respectively used to be connected to the cathode of the APD.

8. The protection circuit according to any one of claims 1 to 3, wherein, in a first time period, the processing module is configured to control the power supply module to output a first power. The starting moment of the first time period is the moment when the power supply module starts to supply power to the APD. In a second time period, the processing module is configured to control the power supply module to output a second power. The starting moment of the second time period is the end moment of the first time period. The power value of the first power is less than the power value of the second power.

9. The protection circuit according to claim 8, wherein, the processing module is further connected to the power supply module.

10. A protection method for protecting an avalanche photodiode APD, wherein, the method is applied to a protection circuit, the protection circuit is as described in any one of claims 1 to 9, and the method includes: According to the voltage value of the APD, controlling a conduction switch to conduct one of the power supply module and at least two parallel branches. The first ends of the at least two parallel branches are connected to a mirror circuit, the mirror circuit is connected to the APD, the conduction switch is connected between the power supply module and the second ends of the at least two parallel branches, and among the at least two parallel branches, the resistances of different branches are different.

11. The protection method according to claim 10, wherein, the controlling a conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD includes: If it is determined that the voltage value of the APD is greater than or equal to a preset value, control the conduction switch to conduct the power supply module and the third branch; Or, If it is determined that the voltage value of the APD is less than the preset value, control the conduction switch to conduct the power supply module and the second branch; Wherein, the mirror circuit includes a first triode and a second triode connected to each other. The first ends of the at least two parallel branches are connected to the emitter of the second triode. The emitter of the first triode is connected to the power supply module. The ratio of the resistance value of the third branch to the resistance value of the first branch is a first ratio. The ratio of the resistance value of the second branch to the resistance value of the first branch is a second ratio. The first ratio is greater than the second ratio. The first branch is connected between the emitter of the first triode and the power supply module.

12. The protection method according to claim 10, Characterized in that, The controlling the conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD includes: If it is determined that the voltage value of the APD is greater than or equal to a preset value, control the conduction switch to conduct the power supply module and the fifth branch; Or, If it is determined that the voltage value of the APD is less than the preset value, control the conduction switch to conduct the power supply module and the sixth branch; Wherein, the mirror circuit includes a first triode and a second triode connected to each other. The first ends of the at least two parallel branches are connected to the emitter of the first triode. The emitter of the second triode is connected to the power supply module. The ratio of the resistance value of the fifth branch to the resistance value of the fourth branch is a third ratio. The ratio of the resistance value of the sixth branch to the resistance value of the fourth branch is a fourth ratio. The third ratio is greater than the fourth ratio. The fourth branch is connected between the emitter of the second triode and the power supply module.

13. The protection method according to claim 11 or 12, Characterized in that, Before controlling the conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD, the method further includes: Determine the voltage value of the APD; Determine whether the voltage value of the APD is greater than or equal to the preset value.

14. The protection method according to claim 13, Characterized in that, The determining the voltage value of the APD includes: Detect the magnitude of the detection current output by the collector of the first triode. The mirror circuit includes the first triode and the second triode connected to each other; Determine the voltage value of the APD according to the magnitude of the detection current.

15. The protection method according to any one of claims 10 to 12, Characterized in that, The method further includes: Within a first time period, control the power supply module to output a first power. The starting moment of the first time period is the moment when the power supply module starts to supply power to the APD; During a second time period, control the power supply module to output a second power. The starting moment of the second time period is the ending moment of the first time period, and the power value of the first power is less than the power value of the second power.

16. The protection method according to claim 11, wherein, before controlling the conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD, the method further includes: at a starting moment, control the conduction switch to conduct the power supply module and the third branch, and the starting moment is the moment when the power supply module starts to supply power to the APD.

17. The protection method according to claim 12, wherein, before controlling the conduction switch to conduct one of the power supply module and at least two parallel branches according to the voltage value of the APD, the method further includes: at a starting moment, control the conduction switch to conduct the power supply module and the fifth branch, and the starting moment is the moment when the power supply module starts to supply power to the APD.

18. An optical network device, wherein, the optical network device includes the protection circuit according to any one of claims 1 to 9. The optical network device further includes an avalanche photodiode APD. The cathode of the APD is connected to the second output end of the collector of the second triode, and the anode of the APD is connected to the processing module; the APD is configured to receive an optical signal and perform optoelectronic conversion to obtain an electrical signal, and the processing module obtains the electrical signal and is configured to perform signal processing on the electrical signal.

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