CN114530760A - Method for independently controlling average optical power and extinction ratio and driving circuit - Google Patents

Abstract

The present invention provides a method for independently controlling average optical power and extinction ratio. By adding a compensation current source, when the switch is in an on state, the current flowing through the laser is I ₀ , and when the switch is in an off state, the current flowing through the laser is I 0 . The current is I ₁ ; and the size of the compensation current source is adjusted so that I ₀ +I ₁ =2I _UP , where I _UP is the size of the bias current source. The invention also provides a circuit for independently controlling the average optical power and the extinction ratio.

Description

A method and driving circuit for independently controlling average optical power and extinction ratio

technical field

The invention belongs to the field of electronic circuits, in particular to a laser driving circuit.

Background technique

Figure 1 shows the characteristic curve of the relationship between the laser input current and the laser output optical power. When the input current of the laser changes rapidly between I ₀ and I ₁ , the output optical power of the laser varies in the range of P ₀ to P ₁ . The average value of the currents I ₀ and I ₁ is defined as the average laser operating current I _bias ; the current The difference between I ₁ and I ₀ is the laser modulation current I _mod =I ₁ -I ₀ ; the laser output optical power corresponding to the average current is the average optical power Pav; the ratio of the laser optical power P ₁ to P ₀ is the extinction ratio ER =10logP ₁ /P ₀ .

FIG. 2 is a schematic diagram of a laser driving circuit. When the switch is in the on state in the figure, the current flowing through the laser is I ₀ =I _UP - I _DN , and when the switch is in the off state, the current flowing through the laser is I ₁ =I _UP . Therefore, for the laser driving circuit shown in the figure, the average current I _bias =I _{UP -IDN} /2, and the modulation current I _mod = _IDN . The average current I _bias is not only related to I _UP , but also related to I _DN , adjusting the laser The modulation current I _mod will change the average current I _bias of the laser, so that the average optical power and extinction ratio of the laser cannot be adjusted separately, which brings certain inconvenience to the application.

In the application of the optical module composed of the laser driving circuit and the laser, it is often hoped that the bias current I _bias and the modulation current I _mod flowing into the laser can be controlled intuitively and independently, so that the average optical power and extinction ratio of the light emitted by the laser can be easily controlled. . However, when the laser driving circuit in FIG. 2 adjusts the extinction ratio of the laser (ie, adjusts the I _mod current), it will affect the average current I _bias flowing into the laser, thereby affecting the average optical power of the laser.

SUMMARY OF THE INVENTION

The main technical problem to be solved by the present invention is to achieve the purpose that the average current I _bias and the modulation current I _mod flowing into the laser can be independently and intuitively adjusted, and I _bias and I _mod will not affect each other, so as to achieve the average optical power and extinction of the laser. than the purpose of independent control.

In order to solve the above technical problems, the present invention provides a method for independently controlling the average optical power and the extinction ratio, which is characterized in that: when the switch is in an on state by adding a compensation current source, the current flowing through the laser is I ₀ , the current flowing through the laser when the switch is off is I ₁ ; and the size of the compensation current source is adjusted to make I ₀ +I ₁ =2I _UP , where I _UP is the size of the bias current source.

In a preferred embodiment: the added compensation current source is I _S , when the switch is in the on state, the current flowing through the laser I ₀ =I _UP - I _DN + I _S , when the switch is in the off state, The current flowing through the laser I ₁ = I _UP +I _S ;

Then the average current I _bias =(I ₀ +I ₁ )/2=I _UP -(IDN _{-2I S} )/2, let I _S = _IDN /2, then the average current I _bias =I _UP , where I _DN is the size of the modulating current source, and I _S is the size of the compensation current source.

In a preferred embodiment: when the switch is in an on state, the current flowing through the laser I ₀ =I _UP -I _S , when the switch is in an off state, the current flowing through the laser I ₁ =I _UP +I _S ;

Then I _bias =(I ₀ +I ₁ )/2=I _UP -( I _DN -I _S )/2, let I _DN =I _S , then the average current I _bias =I _UP , where I _DN is the modulation current source The size of I _S is the size of the compensation current source.

The invention provides a driving circuit for independently controlling average optical power and extinction ratio, including: a bias current source and a modulation current source, and also a compensation current source connected in parallel with the bias current source; the size of the compensation current source is half of the modulation current source;

The bias current source and the modulation current source are connected in series through the switch.

In a preferred embodiment: the modulation current source and the compensation current source are a single current source.

In a preferred embodiment, the modulation current source and the compensation current source are a plurality of sub-current sources connected in parallel.

In a preferred embodiment: the modulation current source corresponds to the sub-current source in the compensation current source one-to-one, and the size of the sub-current source in the compensation current source is the size of the corresponding sub-current source in the modulation current source. half.

The invention also provides a driving circuit for independently controlling the average optical power and extinction ratio, including: a bias current source and a modulation current source, and a compensation current source connected in parallel with the bias current source; the size of the compensation current source is Same as modulating current source;

The bias current source and the modulation current source are connected in series through the first switch, and the modulation current source and the compensation current source are connected in series through the second switch.

In a preferred embodiment: the modulation current source and the compensation current source are a single current source.

In a preferred embodiment, the modulation current source and the compensation current source are a plurality of sub-current sources connected in parallel.

Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

In the present invention, a current source is added to cancel the component of the I _DN current in the expression of the average current I _bias , so that I _bias =I _UP , so that the average current I _bias and the modulation current I _mod flowing into the laser can be independently and intuitively adjusted without affecting each other, so as to achieve the purpose of independent control of the average optical power and extinction ratio of the laser.

Description of drawings

Fig. 1 is the characteristic curve diagram of the relationship between the laser input current and the laser output optical power;

2 is a schematic diagram of a laser drive circuit in the prior art;

Fig. 3 is the schematic diagram of preferred embodiment 1 of the present invention;

Fig. 4 is the schematic diagram of preferred embodiment 2 of the present invention;

Fig. 5 is the schematic diagram of preferred embodiment 3 of the present invention;

Fig. 6 is the schematic diagram of the preferred embodiment 4 of the present invention;

Fig. 7 is the schematic diagram of the preferred embodiment 5 of the present invention;

FIG. 8 is a schematic diagram of the preferred embodiment 6 of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to 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. The embodiments of the present invention, and all other embodiments obtained by those of ordinary skill in the art without creative efforts, fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "top/bottom", etc. are based on the orientations shown in the accompanying drawings Or the positional relationship is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed to indicate or imply relative importance.

In the description of the present invention, it should be noted that, unless otherwise expressly specified and limited, the terms "installation", "provided with", "sleeve/connection", "connection", etc., should be understood in a broad sense, such as " "connection", which can be a wall-mounted connection, a detachable connection, or an integral connection, a mechanical connection, an electrical connection, a direct connection, or an indirect connection through an intermediate medium, or an internal connection between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

This embodiment provides a method for independently controlling the average optical power and extinction ratio. By adding a compensation current source, when the switch is in an on state, the current flowing through the laser is I ₀ , and when the switch is in an off state, the current flowing through the laser is I 0 . The current is I ₁ ; and the size of the compensation current source is adjusted so that I ₀ +I ₁ =2I _UP , where I _UP is the size of the bias current source. Therefore, the purpose of independent and intuitive adjustment of the average current I _bias flowing into the laser and the modulation current I _DN can be achieved without affecting each other, so as to achieve the purpose of independent control of the average optical power and extinction ratio of the laser.

In order to implement the above method, this embodiment provides three specific circuits.

Example 1

Referring to FIG. 3, a driving circuit for independently controlling average optical power and extinction ratio includes: a bias current source and a modulation current source, and also includes a compensation current source connected in parallel with the bias current source; the compensation current source has a size I _s is half of the modulation current source I _DN ; the bias current source and the modulation current source are connected in series through a switch.

After the above design, when the switch is on, the current flowing through the laser I ₀ =I _UP - I _DN +I _S , when the switch is off, the current flowing through the laser I ₁ =I _UP +I _S ; then I _bias =(I ₀ +I ₁ )/2=I _UP −

(IDN- _2Is )/2, since _IDN = _2Is , the _average current _Ibias = _IUP . I _UP is the size of the bias current source.

Example 2

Referring to FIG. 4 , the difference between this embodiment and Embodiment 1 is that the modulation current source I _DN and the compensation current source Is described in _Embodiment 1 are a single current source. In this embodiment, the modulation current source I _DN and the compensation current source I _s1 are multiple sub-current sources connected in parallel. In addition, the modulation current source I _DN corresponds to the sub-current source in the compensation current source I _s1 one-to-one, and the size of the sub-current source in the compensation current source _Is is the corresponding sub-current in the modulation current source I _DN half of the source.

After calculation, the average current flowing into the laser I _bias =N*I _P1 -1/2(Imod1+Imod2+...+Imodn), and I _P1 =Ibiasp1+Imod1/2N+Imod2/2N+...+Imod2/2N, the final calculation I _bias =N*I _biasp1 . In this way, the purpose of independent control of the I _bias current and the I _mod current of the laser is achieved.

Example 3

Referring to Fig. 5, the added compensation current source is I _S1 =I _mod1 /2N+I _{mod2 /2N+...+I modn} /2N, after calculation, the average current flowing into the laser I _bias =N*I _P1 -1/2(I _{mod1 + I mod2 + . _ _ _ _} In this way, the purpose of independent control of the Ibias current and the Imod current of the laser is achieved.

Example 4

Referring to FIG. 6 , this embodiment provides a driving circuit for independently controlling average optical power and extinction ratio, including: a bias current source _IP2 , a compensation current source _IS , a switch Q1 , a switch Q2 , a load Z1 , a load Z2 and modulation current source I _N2 ; the upper end of the bias current source _IP2 is connected to the power supply VDD, and the lower end is connected to the upper end of the load Z1; the compensation current source _IS is connected in parallel with the bias current source _IP2 ; The lower end is connected to the upper end of the switch tube Q1; the lower end of the switch tube Q1 is connected to the upper end of the modulation current source I _N2 ; the upper end of the load Z2 is connected to the lower end of the bias current source, and the lower end of the load Z2 is connected to the upper end of the switch tube Q2; The lower end of the tube Q2 is connected to the upper end of the modulation current source I _N2 ; the lower end of the modulation current source I _N2 is grounded; the anode end of the laser is connected to the upper end of the switch tube Q2, and the cathode is grounded; the switch tube Q1 and the switch tube Q2 constitute the differential pair of the drive circuit. , the control terminals of the switch tube Q1 and the switch tube Q2 are respectively connected to one end and the other end of the differential input signal. In the embodiment, the switch transistor Q1 and the switch transistor Q2 are implemented by using NPN transistors, and may also be implemented by using other devices (eg, NMOS transistors).

Through the above design, when the input differential signal of the input differential pair tube is switched at high speed, the average current flowing through the laser I _bias =I _P2 +I _{S -IN2} , and the compensation current source I _S =I _N2 is designed, so that I _bias = _IP2 . Therefore, the bias current flowing through the laser is controlled by the bias current source _IP2 , and the modulation current is controlled by the modulation current source _IN2 .

Example 5

Referring to FIG. 7 , the difference between this embodiment and Embodiment 4 is that the current magnitude of the compensation current source is I _S2 =I _N2 /N. After calculation, the average laser current I _bias = _N *I _biasp2 , I _mod =IN2 , achieves the expected independent control of I _bias and I _mod , thereby realizing the independent control of the average optical power and extinction ratio of the laser.

Example 6

Referring to FIG. 8 , the magnitude of the current of the compensation current source in the figure is I _S2 = _IN2 /2N. After calculation, the average current of the laser I _bias =N*I _biasp2 , and I _mod =I _N2 , achieving the desired purpose of independent control of I _bias and I _mod .

The above is only a preferred embodiment of the present invention, but the design concept of the present invention is not limited to this. Insubstantial changes are acts that violate the protection scope of the present invention.

Claims (10)

1. A method for independently controlling average optical power and extinction ratioCharacterized in that: when the switch is in a conducting state by adding the compensating current source, the current flowing through the laser is I₀The current flowing through the laser when the switch is in the off state is I₁(ii) a And adjusting the magnitude of the compensating current source such that I₀+I₁＝2I_UP，I_UPIs the magnitude of the bias current source.

2. The method of claim 1, wherein the step of independently controlling the average optical power and the extinction ratio comprises: when the switch is in the conducting state, a current I flows through the laser₀＝I_UP-I_DN+I_SWhen the on-light is in off state, the current I flowing through the laser₁＝I_UP+I_S；

Then the average current I_bias＝(I₀+I₁)/2＝I_UP-(I_DN-2I_S) /2, order I_DN＝2I_SAverage current I_bias＝I_UPIn which I_DNTo modulate the magnitude of the current source, I_STo compensate for the size of the current source.

3. The method of claim 1, wherein the step of independently controlling the average optical power and the extinction ratio comprises: when the switch is in the conducting state, a current I flows through the laser₀＝I_UP-I_SWhen the switch-on light is in the off state, the current I flowing through the laser₁＝I_UP+I_S；

Then I_bias＝(I₀+I₁)/2＝I_UP-(I_DN-I_S) /2, order I_DN＝I_SAverage current I_bias＝I_UPIn which I_DNTo modulate the magnitude of the current source, I_STo compensate for the size of the current source.

4. A driver circuit for independently controlling average optical power and extinction ratio, comprising: the modulation current source is connected with the bias current source and the modulation current source; the size of the compensation current source is half of that of the modulation current source;

the bias current source and the modulation current source are connected in series through a switch.

5. The driving circuit of claim 4, wherein the driving circuit is capable of independently controlling the average optical power and the extinction ratio, and further comprises: the modulation current source and the compensation current source are a single current source.

6. The driving circuit of claim 4, wherein the driving circuit is capable of independently controlling the average optical power and the extinction ratio, and further comprises: the modulation current source and the compensation current source are a plurality of sub current sources connected in parallel.

7. The driving circuit of claim 6, wherein the driving circuit is capable of independently controlling the average optical power and the extinction ratio, and further comprises: the modulation current sources and the sub current sources in the compensation current source are in one-to-one correspondence, and the size of the sub current source in the compensation current source is half of that of the corresponding sub current source in the modulation current source.

8. A driver circuit for independently controlling average optical power and extinction ratio, comprising: the modulation current source is connected with the bias current source and the modulation current source; the magnitude of the compensation current source is the same as that of the modulation current source;

the bias current source and the modulation current source are connected in series through a first switch, and the modulation current source and the compensation current source are connected in series through a second switch.

9. The driving circuit for independently controlling average optical power and extinction ratio of claim 8, wherein: the modulation current source and the compensation current source are a single current source.

10. The driving circuit for independently controlling average optical power and extinction ratio as claimed in claim 8, wherein: the modulation current source and the compensation current source are a plurality of sub current sources connected in parallel.

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