阅读说明：本技术 激光驱动器、芯片以及激光器驱动方法 (Laser driver, chip and laser driving method ) 是由 洪明 林永辉 于 2021-09-18 设计创作，主要内容包括：本申请公开一种激光驱动器、芯片以及激光器驱动方法,以提供一种较为成熟的调顶功能集成方案,且调顶电路同时兼容调幅调顶和调频调顶功能；同时克服了现有技术中调顶失真以及调顶参数不易控制的问题。本申请提供的一种激光驱动器,激光驱动器用于连接至激光器,并驱动激光器输出所需光信号,且激光驱动器包括：调顶模块,用于获取调顶信号,并根据调顶信号生成调顶电流,调顶模块还用于连接至激光器,并将调顶电流输出至激光器；业务模块,用于获取业务信号,并根据业务信号生成业务电流,业务模块还用于连接至激光器,并将业务电流输出至激光器；调顶电流和业务电流共同驱动激光器,使激光器根据调顶信号以及业务信号出射光信号。(The application discloses a laser driver, a chip and a laser driving method, which aims to provide a mature top-adjusting function integration scheme, and a top-adjusting circuit is compatible with both amplitude-adjusting top-adjusting and frequency-adjusting top-adjusting functions; meanwhile, the problems of set-top distortion and difficult control of set-top parameters in the prior art are solved. The application provides a laser driver, laser driver is used for being connected to the laser instrument to drive the laser instrument and export required optical signal, and laser driver includes: the top-adjusting module is used for acquiring a top-adjusting signal and generating a top-adjusting current according to the top-adjusting signal, and is also used for connecting to the laser and outputting the top-adjusting current to the laser; the service module is used for acquiring a service signal and generating a service current according to the service signal, and is also used for connecting to the laser and outputting the service current to the laser; the top-tuning current and the service current jointly drive the laser, so that the laser emits light signals according to the top-tuning signal and the service signal.)

1. A laser driver, comprising:

the top-adjusting module is used for acquiring a top-adjusting signal and generating a top-adjusting current according to the top-adjusting signal, and is also used for connecting to the laser and outputting the top-adjusting current to the laser;

the service module is used for acquiring a service signal and generating a service current according to the service signal, and is also used for connecting to the laser and outputting the service current to the laser;

and the top-adjusting current and the service current jointly drive the laser, so that the laser emits light signals according to the top-adjusting signals and the service signals.

2. The laser driver of claim 1, wherein the set-top module comprises a first operational amplifier, a set-top digital-to-analog conversion unit, a first N-type triode, and a set-top resistor, and further comprises:

the first operational amplifier comprises a non-inverting input end and an inverting input end, wherein the non-inverting input end is used for obtaining the set-top signal, and the output end of the first operational amplifier is connected to the grid electrode of the first N-type triode;

the top-adjusting digital-to-analog conversion unit is connected to the non-inverting input end of the first operational amplifier through a first resistor and is used for providing a first voltage to the non-inverting input end of the first operational amplifier;

the drain electrode of the first N-type triode is used for being connected to the laser, the source electrode of the first N-type triode is grounded through the top adjusting resistor, and the non-grounded end of the top adjusting resistor is further connected to the inverting input end of the first operational amplifier.

3. The laser driver of claim 2, further comprising a register, connected to the set-top dac and the set-top resistor, for controlling a magnitude of the first voltage output by the set-top dac and controlling a resistance of the set-top resistor.

4. The laser driver of claim 1, wherein the frequency-modulated top-modulated signal comprises an amplitude-modulated top-modulated signal and a frequency-modulated top-modulated signal, and wherein the amplitude-modulated top-modulated signal comprises a digital signal and the frequency-modulated top-modulated signal comprises an analog signal.

5. The laser driver of claim 4, wherein the digital signal comprises a Manchester-encoding-based digital signal, and wherein the analog signal comprises one of a sine analog signal and a cosine analog signal.

6. The laser driver of claim 2, further comprising a bias module for connecting to the laser and outputting a bias current to the laser.

7. The laser driver of claim 6, wherein the bias module comprises a bias current source having one end for connecting to the laser and the other end connected to ground for outputting a bias current to the laser.

8. The laser driver of claim 6, wherein the bias module comprises a bias digital-to-analog conversion unit, a subtractor, a voltage division unit, a second operational amplifier, a second N-type transistor, and a bias resistor, wherein:

the bias digital-to-analog conversion unit is used for providing bias voltage;

the subtractor comprises a first input end and a second input end, the first input end is connected to the offset digital-to-analog conversion unit, and the second input end is connected to the output end of the top-adjusting digital-to-analog conversion unit through the voltage division unit;

the second operational amplifier comprises a non-inverting input end and an inverting input end, the non-inverting input end is connected to the output end of the subtracter, and the output end of the second operational amplifier is connected to the grid electrode of the second N-type triode;

the drain electrode of the second N-type triode is connected to the drain electrode of the first N-type triode, the source electrode of the second N-type triode is grounded through the biasing resistor, and the non-grounded end of the biasing resistor is further connected to the inverting input end of the second operational amplifier.

9. The laser driver of claim 8, wherein the voltage divider unit comprises a second resistor and a third resistor, wherein a first terminal of the third resistor is connected to the output terminal of the set-top dac unit, a second terminal of the third resistor is connected to a first terminal of the second resistor, a second terminal of the second resistor is connected to ground, a first terminal of the second resistor is further connected to a second input terminal of the subtractor, and:

the resistance value of the second resistor is equal to that of the bias resistor, and the resistance value of the third resistor is equal to the difference value of the top-adjusting resistor and the bias resistor.

10. The laser driver of claim 1, wherein the service module comprises:

the switch is used for switching on and off states according to the service signal, conducting when the service signal is at a high level, and switching off when the service signal is at a low level, and one end of the switch is used for being connected to the laser;

and one end of the service current source is grounded, and the other end of the service current source is connected to the other end of the switch and is used for providing service current.

11. A chip comprising a laser driver according to any of claims 1 to 10, the chip further integrating a laser, the laser being connected to the laser driver and emitting a desired optical signal following a driving current of the laser driver.

12. A laser driving method, comprising the steps of:

providing a set top signal, the set top signal comprising one of a frequency modulated set top signal and an amplitude modulated set top signal;

acquiring a top-adjusting current according to the top-adjusting signal;

acquiring a service current according to the service signal;

and outputting the top adjusting current and the service current to the laser so as to drive the laser.

13. The laser driving method according to claim 12, wherein the step of obtaining the set-top current according to the set-top signal comprises:

providing a first operational amplifier, wherein the first operational amplifier comprises a non-inverting input end and an inverting input end, the output end of the operational amplifier is connected to the grid electrode of a first N-type triode, the source electrode of the first N-type triode is grounded through a top-adjusting resistor, the drain electrode of the first N-type triode is connected to the laser, and the inverting input end of the first operational amplifier is connected to the non-grounding end of the top-adjusting resistor;

providing a first voltage;

coupling the first voltage and the capping signal to a non-inverting input of the operational amplifier.

14. The laser driving method according to claim 13, wherein the magnitude of the first voltage is adjusted, and/or the magnitudes of the set-top resistor and the set-top resistor are adjusted, thereby adjusting the magnitude of the set-top current.

15. The laser driving method according to claim 12, wherein the step of obtaining the service current from the service signal comprises:

providing a service current source, wherein one end of the service current source is grounded, and the other end of the service current source is connected to the laser through a switch;

and when the service signal exists, the service current source and the laser are switched on, and the service current source provides service current for the laser.

16. The laser driving method according to claim 12, further comprising the steps of:

providing a bias current to the laser;

and adjusting the magnitude of the bias current to make the sum of the set top current and the bias current constant.

Technical Field

The application relates to the field of optical signal transmission, in particular to a laser driver, a chip and a laser driving method.

Background

In an Optical communication Network with a LAN (local area Network) -WDM (Wavelength Division Multiplexing) architecture, for example, in the field of wireless 5G fronthaul (AAU) connection DU (distribution Unit) networking architecture and WDM PON (Passive Optical Network), a vertex-adjusting technique (PT) is often used to implement Optical module Wavelength pairing between a near end and a far end and related OAM management (Operation Administration and Maintenance).

Each channel typically carries two types of information, one being traffic and the other being tone-top. The service signal transmits high-speed service data, and the top-tuning signal is used for monitoring management data. The basic principle of the tuning technology is to load a low-speed tuning signal in a high-speed service signal at a transmitting end, and analyze the tuning signal at a receiving end through the technologies of filtering, sampling and the like so as to transmit monitoring and operation management information such as wavelength adjustment, temperature monitoring and the like.

The top-adjusting technology is generally divided into two modes of frequency modulation and top adjustment and amplitude modulation and top adjustment, and different system manufacturers select different top-adjusting modes according to use scenes and use habits; correspondingly, a module manufacturer can also design a corresponding optical module according to the requirements of a system manufacturer, and a corresponding top-adjusting circuit is carried on a board level to be matched with frequency-adjusting top-adjusting or amplitude-adjusting top-adjusting; meanwhile, the phenomena that the schemes of different system manufacturers are incompatible, the board distribution space of a module manufacturer is short, and the board distribution design is complicated often exist. In addition, the current industry has few schemes for integrating the top-tuning function in the optical transceiver chip.

In the prior art, a modulation signal output after the top-adjusting modulation generally has a large distortion problem, and the problem that the top-adjusting power and the top-adjusting depth are difficult to accurately control also exists. The modulation depth refers to: in the case of the double sideband amplitude modulation mode, a limited peak amplitude offset value must be imposed. Typically the ratio of the difference between the maximum and minimum amplitudes of the modulated wave to the sum of the maximum and minimum amplitudes of the carrier wave, expressed as a percentage.

Disclosure of Invention

In view of this, the present application provides a laser driver, a chip and a laser driving method, so as to provide a mature tuning function integration scheme, and the tuning circuit is compatible with both am tuning and fm tuning functions, and can overcome the problems of tuning distortion and uneasy control of tuning parameters in the prior art.

The application provides a laser driver, laser driver is used for being connected to the laser instrument, and drives the laser instrument and export required optical signal, and laser driver includes: the top-adjusting module is used for acquiring a top-adjusting signal and generating a top-adjusting current according to the top-adjusting signal, and is also used for connecting to the laser and outputting the top-adjusting current to the laser; the service module is used for acquiring a service signal and generating a service current according to the service signal, and is also used for connecting to the laser and outputting the service current to the laser; and the top-adjusting current and the service current jointly drive the laser, so that the laser emits light signals according to the top-adjusting signals and the service signals.

Optionally, the set-top module includes a first operational amplifier, a set-top digital-to-analog conversion unit, a first N-type triode, and a set-top resistor, and: the first operational amplifier comprises a non-inverting input end and an inverting input end, wherein the non-inverting input end is used for obtaining the set-top signal, and the output end of the first operational amplifier is connected to the grid electrode of the first N-type triode; the top-adjusting digital-to-analog conversion unit is connected to the non-inverting input end of the first operational amplifier through a first resistor and is used for providing a first voltage to the non-inverting input end of the first operational amplifier; the drain electrode of the first N-type triode is used for being connected to the laser, the source electrode of the first N-type triode is grounded through the top adjusting resistor, and the non-grounded end of the top adjusting resistor is further connected to the inverting input end of the first operational amplifier.

Optionally, the digital-to-analog converter further includes a register, connected to the vertex-adjusting digital-to-analog conversion unit and the vertex-adjusting resistor, and configured to control a magnitude of the first voltage output by the vertex-adjusting digital-to-analog conversion unit and a resistance of the vertex-adjusting resistor.

Optionally, the amplitude modulation and top modulation signal includes a digital signal, and the frequency modulation and top modulation signal includes an analog signal.

Optionally, the digital signal includes a digital signal based on manchester encoding, and the analog signal includes one of a sine analog signal and a cosine analog signal.

Optionally, the laser further comprises a bias module, wherein the bias module is connected to the laser and outputs a bias current to the laser.

Optionally, the bias module includes a bias current source, one end of the bias current source is used for being connected to the laser, and the other end of the bias current source is grounded and used for outputting a bias current to the laser.

Optionally, the bias module includes a bias digital-to-analog conversion unit, a subtractor, a voltage division unit, a second operational amplifier, a second N-type triode, and a bias resistor, wherein: the bias digital-to-analog conversion unit is used for providing bias voltage; the subtractor comprises a first input end and a second input end, the first input end is connected to the offset digital-to-analog conversion unit, and the second input end is connected to the output end of the top-adjusting digital-to-analog conversion unit through the voltage division unit; the second operational amplifier comprises a non-inverting input end and an inverting input end, the non-inverting input end is connected to the output end of the subtracter, and the output end of the second operational amplifier is connected to the grid electrode of the second N-type triode; the drain electrode of the second N-type triode is connected to the drain electrode of the first N-type triode, the source electrode of the second N-type triode is grounded through the biasing resistor, and the non-grounded end of the biasing resistor is further connected to the inverting input end of the second operational amplifier.

Optionally, the voltage dividing unit includes a second resistor and a third resistor, wherein a first end of the third resistor is connected to the output end of the set-top digital-to-analog converting unit, a second end of the third resistor is connected to the first end of the second resistor, a second end of the second resistor is grounded, the first end of the second resistor is further connected to the second input end of the subtractor, and: the resistance value of the second resistor is equal to that of the bias resistor, and the resistance value of the third resistor is equal to the difference value of the top-adjusting resistor and the bias resistor.

Optionally, the service module includes: the switch is used for switching on and off states according to the service signal, conducting when the service signal is at a high level, and switching off when the service signal is at a low level, and one end of the switch is used for being connected to the laser; and one end of the service current source is grounded, and the other end of the service current source is connected to the other end of the switch and is used for providing service current.

The application also provides a chip, including the laser driver, the chip still integrates the laser instrument, the laser instrument is connected to the laser driver to follow the required light signal of laser driver's driving current outgoing.

The application also provides a laser driving method, which comprises the following steps: providing a set top signal, the set top signal comprising one of a frequency modulated set top signal and an amplitude modulated set top signal; acquiring a top-adjusting current according to the top-adjusting signal; acquiring a service current according to the service signal; and outputting the top adjusting current and the service current to the laser so as to drive the laser.

Optionally, when the set-top current is obtained according to the set-top signal, the method includes the following steps: providing a first operational amplifier, wherein the first operational amplifier comprises a non-inverting input end and an inverting input end, the output end of the operational amplifier is connected to the grid electrode of a first N-type triode, the source electrode of the first N-type triode is grounded through a top-adjusting resistor, the drain electrode of the first N-type triode is connected to the laser, and the inverting input end of the first operational amplifier is connected to the non-grounding end of the top-adjusting resistor; providing a first voltage;

coupling the first voltage and the capping signal to a non-inverting input of the operational amplifier.

Optionally, the magnitude of the first voltage is adjusted, and/or the magnitudes of the second voltage and the set-top resistor are adjusted, so that the magnitude of the set-top current is adjusted.

Optionally, when the service current is obtained according to the service signal, the method includes the following steps: providing a service current source, wherein one end of the service current source is grounded, and the other end of the service current source is connected to the laser through a switch; and when the service signal exists, the service current source and the laser are switched on, and the service current source provides service current for the laser.

Optionally, the method further comprises the following steps: providing a bias current to the laser; and adjusting the magnitude of the bias current to make the sum of the set top current and the bias current constant.

The laser driver, the chip and the laser driving method in the application can directly convert the top-adjusting signal into the top-adjusting current, the top-adjusting current is directly superposed with the service current and applied to the laser, so that the working point of the modulating signal is not influenced, the probability of outputting the distorted modulating signal is reduced, the implementation mode is simpler, the interference is smaller, the crosstalk between the signals and the interference to the working point are effectively avoided, and the precision and the stability of the signals are improved.

In addition, the laser driver, the chip and the laser driving method can realize a frequency modulation and top modulation mode and an amplitude modulation and top modulation mode in the chip, and the corresponding circuit of the laser driver is integrated in the chip, so that the board distribution space of the optical module provided with the laser is saved, and the design flexibility of the optical module is improved.

And the top adjusting mode of the top adjusting module integrated in the chip can be freely selected, the top adjusting power and the top adjusting depth can be adjusted, and the chip has great significance for the degree of freedom of module design of a module manufacturer and the technical use flexibility of a system manufacturer.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a laser driver according to an embodiment of the present application.

Fig. 2 is a schematic structural diagram of the laser driver according to an embodiment of the present application.

Fig. 3 is a schematic structural diagram of the bias module in an embodiment of the present application.

Fig. 4 is a flowchart illustrating a laser driving method according to an embodiment of the present disclosure.

Detailed Description

The research finds that the above problems exist in the prior art because, in the prior art, a low-speed tuning signal is loaded to a driving power supply voltage in advance, and then the power supply voltage is coupled to a modulation signal, the power supply voltage may affect a working point of the modulation signal, the modulation signal is affected by interference, and the coupled modulation signal may be distorted.

Furthermore, since the modulation signal is loaded with a tuning signal, there is a problem of nonlinearity when the modulation signal is converted into a modulation current for driving the laser. At this time, no matter whether a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) or a bipolar Junction Transistor (bjt) NPN high-speed amplifier tube is used, the voltage-to-current process is nonlinear, and besides further aggravating the distortion of the signal, the parameter indexes such as the set-top power and the set-top depth are not easy to be accurately controlled.

The laser driver, the chip, and the method for driving the laser LD are further described below with reference to the drawings and the embodiments.

Fig. 1 is a schematic structural diagram of a laser driver according to an embodiment of the present application.

The application provides a laser driver, laser driver is used for being connected to laser LD, and drive laser LD output required optical signal, and laser driver includes: the set-top module 100 is configured to acquire a set-top signal and generate a set-top current Ipt according to the set-top signal, and the set-top module 100 is configured to connect to the laser LD and output the set-top current Ipt to the laser LD. The set-top signal comprises one of a frequency modulated set-top signal and an amplitude modulated set-top signal. The laser driver further includes a service module 103, configured to obtain a service signal and generate a service current according to the service signal, where the service module 103 is further configured to connect to a laser LD and output the service current to the laser LD.

In this embodiment, the set-top signal is directly converted into a set-top current Ipt, and the set-top current Ipt is directly superimposed on the service current to drive the laser LD together, so that the laser LD emits an optical signal according to the set-top signal and the service signal.

In this embodiment, the low-speed set top signal and the high-speed service signal have no coupling relationship before being converted into the set top current Ipt and the modulation current of the corresponding laser LD, and it is no longer necessary to load the set top signal to the supply voltage first, and therefore it is no longer necessary to couple the supply voltage loaded with the set top signal to the modulation signal, and therefore the operating point of the modulation signal is not affected, so that the distorted modulation signal is output, the implementation is simpler, the interference is less, the crosstalk between the signals and the interference to the operating point are effectively avoided, and the accuracy and the stability of the signal are improved.

The Laser LD may be a Direct Modulated Laser (DML) or an Electro-absorption Modulated Laser (EML).

The service current is needed to drive the laser LD, and a bias current, which may be provided by a bias module. As shown in fig. 1 and 2. The bias module comprises a bias current source Ibias which outputs bias current to the laser LD so that the laser LD works in a normal working state.

Because the laser driver directly carries out current conversion on the top-adjusting signal, the laser driver can realize the corresponding top-adjusting function no matter the top-adjusting signal is a frequency-modulation top-adjusting signal or an amplitude-modulation top-adjusting signal. The set top signal comprises one of a frequency modulated set top signal and an amplitude modulated set top signal.

The fm topping signal corresponds to a low-frequency periodic signal with a small amplitude, such as a sine signal or a cosine signal in an analog signal. The amplitude modulation and top modulation signal is only a low-frequency signal with small amplitude, and periodicity is not required any more. Accordingly, the am capping signal may comprise a digital signal, and the digital signal comprises a digital signal based on manchester encoding. Manchester encoding is a method of transmitting code information and a clock synchronization signal together to a counterpart by including a clock and data in a signal stream. Each symbol of the manchester code is modulated to two levels so that the data transmission rate is only 1/2 times the modulation rate.

It should be noted that the small amplitude referred to herein means that the amplitude of the pilot tone signal is one hundredth or one thousandth of the amplitude of the traffic signal. The amplitude of the amplitude modulated set top box signal and the amplitude of the frequency modulated set top box signal may be set as desired by those skilled in the art.

The top-adjusting module 100 includes a first operational amplifier 101, a top-adjusting digital-to-analog conversion unit PT _ DAC, a first N-type transistor MN1, and a top-adjusting resistor R1. The first operational amplifier 101 includes a non-inverting input terminal and an inverting input terminal, where the non-inverting input terminal is used to obtain the set-top signal. The set-top digital-to-analog conversion unit PT _ DAC is connected to the non-inverting input terminal of the first operational amplifier 101 through a first resistor R0, and is configured to provide a first voltage to the non-inverting input terminal of the first operational amplifier 101. The grid electrode of the first N-type triode MN1 is connected to the output end of the first operational amplifier 101, the drain electrode of the first N-type triode is used for being connected to the laser LD, and the source electrode of the first N-type triode is grounded through the top-adjusting resistor R1. The non-grounded end of the top-tuning resistor R1 is also connected to the inverting input terminal of the first operational amplifier 101.

In this embodiment, the first operational amplifier 101 is an electronic integrated circuit including a multi-stage amplifier circuit, and the input stage of the electronic integrated circuit is a differential amplifier circuit, which has high input resistance and zero drift suppression capability; the intermediate stage mainly performs voltage amplification, has high voltage amplification factor and is generally composed of a common emitter amplification circuit; the output stage is connected with the load, has the characteristics of strong loading capacity and low output resistance, and the output signal of the first operational amplifier 101 is in direct proportion to the signal voltage difference of the two input ends.

In other embodiments, the structure of the first operational amplifier 101 may be provided as needed, and the actual implementation may be diversified.

The set-top digital-to-analog conversion unit PT _ DAC is connected to the non-inverting input terminal of the first operational amplifier 101 through a first resistor R0, and the set-top signal is pulled up to the first voltage output by the set-top digital-to-analog conversion unit PT _ DAC through the first resistor R0.

When the signal and the first voltage of transferring to the same phase input end of first operational amplifier 101, because great voltage difference between same phase input end and the inverting input end, first N type triode MN1 switches on, the source electrode and the drain electrode of first N type triode MN1 communicate, laser instrument LD one end is connected to a voltage VCC, and the other end passes through the source electrode and the drain electrode ground connection of first N type triode MN 1.

The first operational amplifier 101 constructs feedback between the inverting input terminal and the output terminal through the first N-type transistor MN1, and the output voltage of the first operational amplifier 101 is influenced by the input voltage of the non-inverting input terminal in an initial state, so that the input signal of the inverting input terminal of the first operational amplifier 101 follows the signal input by the non-inverting input terminal. Referring to fig. 1 and 2, in the embodiment shown in fig. 1 and 2, the voltage input by the inverting input terminal and the voltage input by the forward input terminal are both the top-adjusting voltage, and the top-adjusting voltage and the first voltage output by the top-adjusting digital-to-analog conversion unit PT _ DAC are related to the amplitude of the top-adjusting signal.

Because the first operational amplifier 101 can better follow the input tuning signal, the tuning current Ipt converted from the tuning signal has no problem of nonlinearity.

The set-top module 100 further includes a register, connected to the set-top digital-to-analog conversion unit PT _ DAC and the set-top resistor R1, for controlling a magnitude of the first voltage output by the set-top digital-to-analog conversion unit PT _ DAC and controlling a resistance of the set-top resistor R1.

In one embodiment, the register includes a set-top digital-to-analog conversion unit PT _ DAC register connected to the set-top digital-to-analog conversion unit PT _ DAC for controlling an output voltage of the set-top digital-to-analog conversion unit PT _ DAC. The register further comprises a top-adjusting resistor R1 register connected to the top-adjusting resistor R1 and used for controlling the resistance value of the top-adjusting resistor R1.

Because the magnitude of the set-top current Ipt is related to the set-top voltage and the resistance value of the set-top resistor R1, and is a result of dividing the set-top voltage by the set-top resistor R1, the set-top voltage is related to the coupling mode and the first voltage output by the set-top digital-to-analog conversion unit PT _ DAC, so that the first voltage of the set-top digital-to-analog conversion unit PT _ DAC can be adjusted through the register, and the resistance value of the set-top resistor R1 can be adjusted, that is, the magnitude of the set-top current Ipt can be adjusted, and the adjustment of the set-top power can be realized.

In one embodiment, the tuning signal may be applied to the non-inverting input terminal of the first operational amplifier 101 by ac coupling. The alternating current Coupling (AC Coupling) is to remove a direct current component in the pilot tone signal through blocking capacitance Coupling. At this time, the tuning depth of the tuning process is related to the output voltage of the tuning DAC unit PT _ DAC, the resistance of the tuning resistor R1, and the swing of the tuning signal.

In other embodiments, the non-inverting input terminal of the first operational amplifier 101 may also be applied with the vertex-modulated signal by dc coupling. At this time, the tuning depth of the tuning process is determined by the output voltage of the tuning DAC PT _ DAC and the resistance of the tuning resistor R1.

As can be seen from the above, the tuning depth of the tuning process can be adjusted by the first voltage output by the tuning DAC, the resistance value of the tuning resistor R1, and the swing of the tuning signal, or by the first voltage output by the tuning DAC and the resistance value of the tuning resistor R1.

Therefore, when the first voltage of the output of the vertex-adjusting digital-to-analog conversion unit PT _ DAC and the resistance value of the vertex-adjusting resistor R1 are adjustable, the vertex-adjusting depth is also adjustable.

Moreover, since a common mode point needs to be provided when the ac coupling is performed, when the set-top signal is input to the non-inverting input terminal of the first operational amplifier 101 in the ac coupling manner, the output voltage of the set-top digital-to-analog conversion unit PT _ DAC may provide a common mode voltage for the set-top signal, so as to provide the common mode point. When the set-top signal is input to the non-inverting input terminal of the first operational amplifier 101 by using dc coupling, the output voltage of the set-top digital-to-analog conversion unit PT _ DAC may provide a maximum voltage for the set-top signal, where the maximum voltage refers to a voltage indicated by a high level.

Referring to fig. 3, a schematic structural diagram of the bias module 102 in an embodiment is shown.

In this embodiment, the laser driver further comprises a bias module 102, and the bias module 102 is configured to be connected to the laser LD and output a bias current to the laser LD.

In the embodiment shown in fig. 1 and 2, the bias module 102 includes a bias current source Ibias, one end of the bias current source Ibias is used for connecting to the laser LD, and the other end of the bias current source Ibias is grounded for outputting a bias current to the laser LD.

In the embodiment shown in fig. 3, the BIAS module 102 includes a BIAS digital-to-analog conversion unit BIAS _ DAC, a subtractor 301, a second operational amplifier 302, a second N-type transistor MN2, and a BIAS resistor Rbias, where the BIAS digital-to-analog conversion unit BIAS _ DAC is configured to provide a BIAS voltage, one end of the subtractor 301 is connected to the BIAS digital-to-analog conversion unit BIAS _ DAC, and the other end is connected to the top-tuning module 100 through a voltage divider. The voltage divider comprises a second resistor R2 and a third resistor R3, the resistance of the second resistor R2 is equal to the bias resistor Rbias, and the resistance of the third resistor R3 is equal to the difference between the top-adjusting resistor R1 and the bias resistor Rbias.

The non-inverting input terminal of the second operational amplifier 302 is connected to the output terminal of the subtractor 301. The gate of the second N-type transistor MN2 is connected to the output terminal of the second operational amplifier 302, the drain is connected to the service module 103 and the bias module 102, the source is grounded through the bias resistor Rbias, and the non-grounded terminal of the bias resistor Rbias is also connected to the inverting input terminal of the second operational amplifier 302.

The subtractor 301 is one of basic integrated operational amplifier circuits, and is generally implemented by an operational circuit formed by an integrated operational amplifier and a feedback network. The signal output by the output end of the subtractor 301 is the difference between the offset voltage and the output voltage of the set-top digital-to-analog conversion unit PT _ DAC.

In the embodiment shown in fig. 3, the voltage dividing unit is connected to the output end of the set-top digital-to-analog converting unit PT _ DAC, and is configured to divide the output voltage of the set-top digital-to-analog converting unit PT _ DAC and output the divided voltage result to one input end of the subtractor 301.

The voltage dividing unit includes a second resistor R2 and a third resistor R3, wherein a first end of the third resistor R3 is connected to the output end of the vertex-adjusting digital-to-analog converting unit PT _ DAC, a second end of the third resistor R3 is connected to the first end of the second resistor R2, a second end of the second resistor R2 is grounded, a first end of the second resistor R2 is further connected to the second input end of the subtractor 301, a resistance value of the second resistor R2 is equal to a resistance value of the bias resistor Rbias, and a resistance value of the third resistor R3 is equal to a difference value between the vertex-adjusting resistor R1 and the bias resistor Rbias.

The bias module 102 further comprises a second operational amplifier 302, wherein a non-inverting input of the second operational amplifier 302 is connected to the output of the subtractor 301, and an inverting input of the second operational amplifier 302 is connected to the output of the second operational amplifier 302, so that the inverting input of the second operational amplifier 302 follows the positive input of the second operational amplifier 302.

The voltage obtained by one input end of the subtractor 301 is Vpt × R2/R1, when the output voltage Vpt of the set-top digital-to-analog conversion unit PT _ DAC is dc-coupled to the subtractor 301, the voltage obtained by the input end of the subtractor 301 is Vpt × R2/R1, and the output voltage of the subtractor 301 is Vbias-Vpt × R2/R1. The bias current Ibias is (Vbias-Vpt R2/R1)/R2, and the top-adjusting current Ipt is Vpt/R1.

When the output voltage Vbias of the vertex-adjusting digital-to-analog conversion unit PT _ DAC is ac-coupled to the subtractor 301, the voltage obtained at the input terminal of the subtractor 301 is Vpt × R2/2 × R1, and the output voltage of the subtractor 301 is Vbias-Vpt × R2/2 × R1. The bias current Ibias is (Vbias-Vpt R2/2R 1)/R2. The top-adjusting current Ipt is Vpt/2R 1.

At this time, the sum of the bias current Ibias and the set-top current Ipt is Vbias/R2, which is a constant value, regardless of the dc coupling or the ac coupling.

Therefore, in this embodiment, with the biasing module 102, automatic adjustment of power is also enabled. The BIAS digital-to-analog conversion unit BIAS _ DAC can automatically adjust the magnitude of the BIAS current according to the magnitude of the top-adjusting current Ipt so as to compensate the change of the output optical power caused by the change of the top-adjusting current Ipt, thereby offsetting the optical power generated by the top-adjusting current Ipt, and correspondingly compensating the phenomenon of the average optical power change caused by a top-adjusting signal, thereby ensuring the stability of the average optical power output by the laser LD to which the laser driver is connected.

Therefore, as long as the set-top function is enabled, the laser driver can realize automatic power control, and keep the sum of the bias current and the set-top current Ipt constant, so that the output average optical power is not affected when the set-top is enabled and the set-top parameter is adjusted, a corresponding compensation mechanism, namely automatic power control compensation, is performed on the phenomenon that the average optical power is changed due to the set-top signal, and the stability of the output average optical power is ensured.

In some other embodiments, a current mirror structure may be used to achieve automatic power control. The automatic power control aims to keep the jack current Ipt and the bias current constant, so that the jack current Ipt can flow through the bias current by current mirror image, thereby achieving the purpose of constant current.

The service module 103 includes: one end of the switch K1 is connected to the laser, and is used for switching on and off according to the service signal, wherein the switch K1 is switched on when the service signal is at a high level, and is switched off when the service signal is at a low level; and a service current source Imod having one end connected to ground and the other end connected to the second end of the switch K1, for providing a service current to the laser LD when the switch K1 is turned on.

The service module 103 provides the service current only when a service signal is at a high level. The service current, the bias current and the set top current Ipt drive the laser LD together, so that the laser LD outputs a required optical signal.

In this embodiment, the set-top signal is converted into the set-top current Ipt, and the set-top current Ipt is loaded to the bias current, so that the problem of modulation signal distortion caused by modulating the power supply signal by using the set-top signal when the modulation signal is obtained is avoided, and the problem of nonlinearity when the modulation signal is converted into the modulation current caused by the modulation signal distortion is also avoided. In addition, due to the existence of the register, the value of the first voltage output by the set-top digital-to-analog conversion unit PT _ DAC and the resistance value of the set-top resistor R1 can be adjusted, so that the set-top power and the set-top depth of the laser driver are adjusted through the corresponding register, and the output precision of the set-top signal and the flexibility of the set-top operation are improved. In addition, the invention also provides an automatic power control circuit of the laser LD under the condition of enabling the top-adjusting function, thereby ensuring the working stability of the laser LD.

In addition, in the embodiment, because the corresponding top-adjusting function circuit is integrated, the top-adjusting mode can be freely selected, and the top-adjusting power and the top-adjusting depth can be adjusted, the method has great significance for the degree of freedom of module design of a module manufacturer and the technical use flexibility of a system manufacturer.

In the embodiment of the application, a chip is further provided, and the chip comprises the laser driver.

Due to the laser driver in the embodiment, the chip can realize a frequency modulation and top modulation mode and also realize an amplitude modulation and top modulation mode, and the corresponding circuit of the laser driver is integrated in the chip, so that the board distribution space of the optical module provided with the laser LD is saved, and the design flexibility of the optical module is improved.

Moreover, the tuning mode of the tuning module 100 integrated in the chip can be freely selected, and the tuning power and the tuning depth can be adjusted, so that the tuning module has great significance for the module design freedom degree of a module manufacturer and the technical use flexibility of a system manufacturer.

In the embodiment of the application, a laser LD driving method is also provided.

The driving method includes the steps of: providing a set top signal, the set top signal comprising one of a frequency modulated set top signal and an amplitude modulated set top signal; acquiring a top-adjusting current according to the top-adjusting signal; acquiring a service current according to the service signal; and outputting the top adjusting current and the service current to the laser so as to drive the laser.

Fig. 4 is a schematic flow chart illustrating steps of a method for driving a laser LD according to an embodiment of the present application.

In this embodiment, the laser LD driving method includes the steps of:

step S101: providing a set top signal comprising one of a frequency modulated set top signal and an amplitude modulated set top signal.

The fm topping signal corresponds to a low-frequency periodic signal with a small amplitude, such as a sine signal or a cosine signal in an analog signal. The amplitude modulation and top modulation signal is only a low-frequency signal with small amplitude, and periodicity is not required any more. Accordingly, the am capping signal may comprise a digital signal, and the digital signal comprises a digital signal based on manchester encoding.

It should be noted that the small amplitude referred to herein means that the amplitude of the pilot tone signal is one hundredth or one thousandth of the amplitude of the traffic signal. The amplitude of the amplitude modulated set top box signal and the amplitude of the frequency modulated set top box signal may be set as desired by those skilled in the art.

Step S102: and acquiring a set top current Ipt according to the set top signal.

When the set top current Ipt is obtained according to the set top signal, the method comprises the following steps: providing a first operational amplifier 101, wherein the first operational amplifier 101 comprises a non-inverting input terminal and an inverting input terminal, the output terminal of the operational amplifier is connected to the gate of a first N-type triode, the source of the first N-type triode MN1 is grounded through a top-adjusting resistor R1, the drain of the first N-type triode MN1 is connected to the laser LD, and the inverting input terminal of the first N-type triode is connected to the non-ground terminal of the top-adjusting resistor R1; providing a first voltage; coupling the first voltage and the capping signal to a non-inverting input of the operational amplifier.

Specifically, in this embodiment, the first voltage is provided by the set-top digital-to-analog conversion unit PT _ DAC, and since the magnitude of the set-top current Ipt is related to the magnitude of the set-top voltage and the resistance of the set-top resistor R1, the magnitude of the set-top voltage is related to the first voltage output by the set-top digital-to-analog conversion unit PT _ DAC and the coupling manner as a result of dividing the set-top voltage by the set-top resistor R1. Therefore, the adjustment of the magnitude of the set-top current Ipt can be realized by adjusting the first voltage output by the set-top digital-to-analog conversion unit PT _ DAC and the resistance value of the set-top resistor R1, so as to realize the adjustment of the set-top power.

The coupling mode comprises direct current coupling and alternating current coupling. When the set-top signal is loaded to the non-inverting input terminal of the first operational amplifier 101 in an ac coupling manner, the set-top depth of the set-top processing is related to the output voltage of the set-top digital-to-analog conversion unit PT _ DAC, the resistance value of the set-top resistor R1, and the swing amplitude of the set-top signal.

When the set-top signal is applied to the non-inverting input terminal of the first operational amplifier 101 by means of dc coupling, the set-top depth of the set-top processing is determined by the output voltage of the set-top digital-to-analog conversion unit PT _ DAC and the resistance of the set-top resistor R1.

As can be seen from the above, the tuning depth of the tuning process can be adjusted by the first voltage output by the tuning DAC, the resistance value of the tuning resistor R1, and the swing of the tuning signal, or by the first voltage output by the tuning DAC and the resistance value of the tuning resistor R1.

Therefore, when the first voltage of the output of the vertex-adjusting digital-to-analog conversion unit PT _ DAC and the resistance value of the vertex-adjusting resistor R1 are adjustable, the vertex-adjusting depth is also adjustable.

Step S103: and adjusting the top adjusting power and the top adjusting depth. Specifically, the magnitude of the first voltage output by the set-top digital-to-analog conversion unit PT _ DAC is adjusted, and/or the magnitude of the set-top resistor R1 is adjusted, so as to adjust the magnitude of the set-top current Ipt, and thus adjust the set-top power and the set-top depth.

In some embodiments, the set-top digital-to-analog conversion unit PT _ DAC and the set-top resistor R1 are both connected to a register, and the register controls the magnitude of the first voltage output by the set-top digital-to-analog conversion unit PT _ DAC and controls the magnitude of the set-top resistor R1. Therefore, the first voltage is adjusted through the register, and/or the magnitude of the top-adjusting resistor R1 is adjusted, so that the magnitude of the top-adjusting current Ipt is adjusted, and therefore the top-adjusting power and the top-adjusting depth are adjusted.

Step S104: and acquiring the service current according to the service signal.

When the service current is obtained according to the service signal, the method comprises the following steps: providing a service current source Imod, wherein one end of the service current source Imod is grounded, and the other end of the service current source Imod is connected to the laser LD through a switch K1; and when the service signal exists, the first current source and the laser LD are switched on, and the first current source provides service current for the laser LD.

The service module 103 provides the service current only when there is a service signal. The service current, the bias current and the set top current Ipt drive the laser LD together, so that the laser LD outputs a required optical signal.

Step S105: and outputting the bias current, the set top current Ipt and the service current to the laser LD.

In this embodiment, a bias current is provided to the laser. The sum of the set-top current Ipt and the bias current may be made constant by controlling the magnitude of the bias current.

In some embodiments, the constant of the set-top current Ipt and the sum of the bias currents may be achieved by the bias module 102.

The BIAS module 102 includes a BIAS digital-to-analog conversion unit BIAS _ DAC, a subtractor 301, a second operational amplifier 302, a second N-type triode MN2, and a BIAS resistor Rbias, where the BIAS digital-to-analog conversion unit BIAS _ DAC is used to provide a BIAS voltage, one end of the subtractor 301 is connected to the BIAS digital-to-analog conversion unit BIAS _ DAC, and the other end is connected to the set-top module 100 through a voltage divider. The voltage divider comprises a second resistor R2 and a third resistor R3, the resistance of the second resistor R2 is equal to the bias resistor Rbias, and the resistance of the third resistor R3 is equal to the difference between the top-adjusting resistor R1 and the bias resistor Rbias.

The non-inverting input terminal of the second operational amplifier 302 is connected to the output terminal of the subtractor 301. The gate of the second N-type transistor MN2 is connected to the output terminal of the second operational amplifier 302, the drain is connected to the service module 103 and the bias module 102, the source is grounded through the bias resistor Rbias, and the non-grounded terminal of the bias resistor Rbias is also connected to the inverting input terminal of the second operational amplifier 302.

The subtractor 301 is one of basic integrated operational amplifier circuits, and is generally implemented by an operational circuit formed by an integrated operational amplifier and a feedback network. The signal output by the output end of the subtractor 301 is the difference between the offset voltage and the output voltage of the set-top digital-to-analog conversion unit PT _ DAC.

In the embodiment shown in fig. 3, the voltage dividing unit is connected to the output end of the set-top digital-to-analog converting unit PT _ DAC, and is configured to divide the output voltage of the set-top digital-to-analog converting unit PT _ DAC and output the divided voltage result to one input end of the subtractor 301.

A first end of a third resistor R3 in the voltage dividing unit is connected to an output end of the set-top digital-to-analog converting unit PT _ DAC, a second end of the third resistor R3 is connected to a first end of the second resistor R2, a second end of the second resistor R2 is grounded, the first end of the second resistor R2 is further connected to a second input end of the subtractor 301, a resistance value of the second resistor R2 is equal to a resistance value of the bias resistor Rbias, and a resistance value of the third resistor R3 is equal to a difference value between the set-top resistor R1 and the bias resistor Rbias.

When the input is ac-coupled, the voltage obtained at one input terminal of the subtractor 301 is Vpt R2/R1, the voltage obtained at the other input terminal is a bias voltage Vbias, the output voltage of the subtractor 301 is (Vbias-Vpt R2/R1), since the bias module 102 further includes a second operational amplifier 302, the non-inverting input terminal of the second operational amplifier 302 is connected to the output terminal of the subtractor 301, and the inverting input terminal of the second operational amplifier 302 is connected to the output terminal of the second operational amplifier 302, the inverting input terminal of the second operational amplifier 302 follows the non-inverting input terminal of the second operational amplifier 302, and the bias current Ibias is (Vbias-Vpt R2/R1)/R2. At this time, the sum of the bias current and the set top current Ipt, Vpt/R1, is Vbias/R2, and the sum is a constant value.

When the input is performed by direct current coupling, when the set-top digital-to-analog conversion unit PT _ DAC still outputs Vpt, the voltage obtained at one input terminal of the subtractor 301 is Vpt × R2/2 × R1.

At this time, the output voltage of the subtractor 301 is Vbias-Vpt R2/2R 1, so that the bias current Ibias is (Vbias-Vpt R2/2R 1)/R2, that is, (Vbias/R2-Vpt/2R 1), and since the roof-tuning current Ipt is Vpt/2R 1, the sum of the bias current and the roof-tuning current is Vbias/R2, which is a constant value.

Thus, in this embodiment, with the biasing module 102, automatic adjustment of power is also enabled. The BIAS digital-to-analog conversion unit BIAS _ DAC can automatically adjust the magnitude of the BIAS current according to the magnitude of the top-adjusting current Ipt so as to compensate the change of the output optical power caused by the change of the top-adjusting current Ipt, thereby offsetting the optical power generated by the top-adjusting current Ipt, and correspondingly compensating the phenomenon of the average optical power change caused by a top-adjusting signal, thereby ensuring the stability of the average optical power output by the laser LD to which the laser driver is connected.

Therefore, as long as the set-top function is enabled, the laser driver can realize automatic power control, and keep the sum of the bias current and the set-top current Ipt constant, so that when the set-top is enabled and the set-top parameter is adjusted, the output average optical power is not affected, a corresponding compensation mechanism, namely automatic power control compensation, is performed on the phenomenon that the average optical power is changed due to the set-top signal, and the stability of the output average optical power is ensured.

In some other embodiments, a current mirror structure may be used to achieve automatic power control. The automatic power control aims to keep the jack current Ipt and the bias current constant, so that the jack current Ipt can flow through the bias current by current mirror image, thereby achieving the purpose of constant current.

In this embodiment, by loading the set-top signal to the bias current, the problem of modulation signal distortion caused by modulating the power supply signal with the set-top signal when the modulation signal is obtained is avoided, and the problem of nonlinearity when the modulation signal is converted into the modulation current due to the modulation signal distortion is also avoided. In addition, the value of the first voltage can be adjusted, and the resistance value of the topping resistor R1 can be adjusted, so that the topping power and the topping depth of the laser driver can be adjusted, and the output accuracy of a topping signal and the flexibility of the topping operation are improved. In addition, the invention also performs automatic power control of the laser LD under the condition of enabling the top-adjusting function, and can ensure the working stability of the laser LD.

In addition, in the embodiment, because the corresponding top-adjusting function circuit is integrated, the top-adjusting mode can be freely selected, and the top-adjusting power and the top-adjusting depth can be adjusted, the method has great significance for the degree of freedom of module design of a module manufacturer and the technical use flexibility of a system manufacturer.

The above-mentioned embodiments are only examples of the present application, and not intended to limit the scope of the present application, and all equivalent structures or equivalent flow transformations made by the contents of the specification and the drawings, such as the combination of technical features between the embodiments and the direct or indirect application to other related technical fields, are also included in the scope of the present application.