Test method based on APC and AER loop electrical measurement circuit

文档序号:307991 发布日期:2021-11-26 浏览:10次 中文

阅读说明:本技术 一种基于apc和aer环路电学测量电路的测试方法 (Test method based on APC and AER loop electrical measurement circuit ) 是由 祝晓辉 陶蕤 陈盛文 赵欣 毛毅 李广生 于 2021-10-28 设计创作,主要内容包括:本发明提出了一种基于APC和AER环路电学测量电路的测试方法,新型的、纯电学领域的关于APC和AER功能的测试电路。不需要激光器、监控PD(MPD)、光纤和光学示波器,用普通的分离器件来代替激光器和MPD,用电学示波器来检测电信号,在很大程度上可以降低APC和AER环路测试的成本和复杂度。(The invention provides a test method based on an APC (automatic Power control) and AER (automatic energy recovery) loop electrical measurement circuit, and relates to a novel test circuit related to APC and AER functions in the pure electrical field. The laser, the Monitoring PD (MPD), the optical fiber and the optical oscilloscope are not needed, the laser and the MPD are replaced by common separation devices, and the electric oscilloscope is used for detecting electric signals, so that the cost and the complexity of the APC loop test and the AER loop test can be reduced to a great extent.)

1. A test method based on APC and AER loop electrical measurement circuits is provided, which uses the APC and AER loop electrical measurement circuits to detect electrical signals,

the APC loop and AEC loop electrical measurement circuit comprises an electrical oscilloscope, error code instrument equipment, a laser driver, an analog conversion circuit and a VEB/R current generation circuit;

the analog conversion circuit comprises a resistor R1, a resistor R2 and a triode Q1;

the error code instrument equipment is connected with the laser driver, the resistor R1 is connected with the laser driver after being connected with a VDD power supply, and the resistor R1 is respectively used for transmitting IBIAS direct current for determining the average light power of the laser and IMOD alternating current for determining the extinction ratio of the laser;

the resistor R2 is connected with the emitter of the triode Q1 after being connected with a VDD power supply; the base electrode of the triode Q1 is connected with the resistor R1, the collector electrode of the triode Q1 is connected with the output end of the VEB/R current generating circuit, receives the VER/R current sent by the VEB/R current generating circuit, then is connected with the laser driver, and sends IMPD current to the laser driver;

the triode Q1 is a PNP type triode;

the method is particularly operable to:

step 1: simulating a laser by using a resistor R1 as an on-resistance, and marking the current flowing through a resistor R1 as I1;

step 2: detecting the voltage V1 at the base electrodes of the resistor R1 and the triode Q1 by using an electrical oscilloscope, and calculating the value of the current I1 through the voltage V1 and the resistor R1;

and step 3: a voltage-to-current conversion circuit is formed by using a resistor R2 and a transistor Q1, and the proportion of a flowing current I1 and extraction of an error term are carried out; marking the current flowing through the resistor R2 and the triode Q1 as I2;

and 4, step 4: setting the ratio of the resistors R2 and R1 so as to simulate the mirror proportion relation between the current I1 and the IMPD current;

and 5: the VEB/R current is generated by using a VEB/R current generation circuit, is marked as I3, is merged with the current I2 through the compensation of the current I3 as an error term, and is connected to an IMPD interface of the laser driver as an IMPD current;

step 6: the IMPD current is used to implement the auto extinction ratio control AER function and the auto average power control APC function, respectively.

2. The APC and AER loop based electrical measurement circuit test method of claim 1, wherein said VEB/R current generation circuit comprises a transistor Q2, a transistor Q3, a transistor Q4, a transistor Q5, a resistor R22, a resistor R23, an NMOS transistor M1 and an NMOS transistor M2;

the emitter of the triode Q4 is connected with the collector of the triode Q5; the base electrodes of the triode Q2, the triode Q3 and the triode Q4 are connected together; the resistor R22 is connected with the emitter of the triode Q2 after being connected with a VDD power supply; the resistor R23 is connected with the emitter of the triode Q3 after being connected with a VDD power supply; the emitter of the triode Q5 is connected with a VDD power supply; the base electrode of the triode Q5 is connected with the emitter electrode of the triode Q4; the base electrode of the triode Q4 is also connected with the collector electrode in a lap joint manner;

the NMOS tube M1 and the NMOS tube M2 are grounded to form a clamping current mirror and are respectively connected with a collector electrode of the triode Q3 and a collector electrode of the triode Q4;

the collector of the triode Q2 is connected with the collector of the triode Q1;

the triode Q2, the triode Q3, the triode Q4 and the triode Q5 are PNP type triodes and are the same triodes as the triode Q1; the NMOS tube M1 and the NMOS tube M2 are the same NMOS tube; the resistor R22 and the resistor R23 are the same resistor;

the specific operation of generating the VEB/R current in the step 5 is as follows:

step 5.1: a current mirror with the ratio of 1:1 is formed by an NMOS tube M1 and an NMOS tube M2 of the clamping current mirror, the currents of emitting electrodes of a triode Q3 and a triode Q4 are adjusted to be equal, and the currents of a resistor R23 and a triode Q5 are also adjusted to be equal;

step 5.2: the transistor Q3 and the transistor Q4 are provided as the same transistor, and serve as a clamping voltage, so that the voltage VEB of the resistor R23 and the transistor Q5 are equal;

step 5.3: a transistor Q2 and a resistor R22 are used as the copy of a branch of the transistor Q3 and the resistor R23, so that the current of VEB/R22, namely the VEB/R current, is also the current I3.

3. The APC and AER loop electrical measurement circuit based test method of claim 2, wherein the conversion formula of the calculation between the voltage V1 and the current I1 is as follows:

in the formula, V1 is the voltage at the base of the resistor R1 and the transistor Q1, VDD is the input power voltage, I1 is the current flowing through the resistor R1, and R1 is the resistance of the resistor R1.

4. The APC and AER loop electrical measurement circuit-based test method of claim 3, wherein the current I2 through resistor R2 is calculated as follows:

in the formula, VDD is an input power voltage, I2 is a current flowing through the resistor R2, R2 is a resistance value of the resistor R2, VEB is a voltage value at the resistor R22, the resistor R23 and the transistor Q5, R is a resistance value of the resistor R22 and the resistor R23, and I1 is a current flowing through the resistor R1.

5. The APC and AER loop electrical measurement circuit-based test method of claim 4, wherein said IMPD current is calculated as follows:

6. the APC and AER loop electrical measurement circuit-based test method of claim 5, wherein said current I1 is the sum of IBIAS DC current and IMOD AC current, and is expressed as follows:

7. the APC and AER loop electrical measurement circuit-based test method of claim 1, wherein the resistance R1 has a value in the range of 10 Ω -15 Ω.

Technical Field

The invention belongs to the technical field of laser measurement and adjustment of a communication optical module, and particularly relates to a test method based on an APC (automatic Power control) and AER (automatic optical Circuit) loop electrical measurement circuit.

Background

With the rapid development of services such as large videos, VR/AR, Internet of things and the like, the demand of users on bandwidth is higher and higher, and the fiber to the home is more and more widely applied.

In high-speed optical communication applications, the performance of semiconductor lasers directly determines the quality of the optical signal in the optical fiber transmission line. The characteristics of the laser show great difference along with the change of the environmental temperature, which is mainly shown in that the threshold current of the laser is obviously increased along with the increase of the temperature, and the luminous efficiency is also reduced along with the increase of the temperature. How to enable the laser to still maintain excellent luminescence performance under different environments is a very critical technology in the field of optical communication.

In order to maintain a fast turn-on speed of the laser and avoid optical signal distortion, a proper average optical power needs to be set. If the optical power is set too low, the laser may be below the threshold current when transmitting a "0" pulse, the laser is off, and the laser is on when transmitting a "1" pulse. Frequent switching on and off of the laser increases the photoelectric delay of the laser and slows down the switching speed. If the average optical power setting of the laser is too large, there is a risk of burning out the laser. The appropriate average optical power allows the laser to remain continuously on without frequent switching on and off, while avoiding the risk of burning out the laser. The Automatic Power Control (APC) technology monitors the average light emitting Power of the laser in real time, and feeds back and adjusts the BIAS Current (BIAS Current) of the laser, so that the laser can maintain a proper working state under different environments, and the laser shows excellent light emitting performance.

The Extinction Ratio (ER) is another key index of the laser emission performance, and is used to measure the distinction between "1" light pulse and "0" pulse emitted from the laser. When P1 represents the optical power of a "1" optical pulse and P0 represents the optical power of a "0" optical pulse, the extinction ratio is defined as 10lg (P1/P0). The extinction ratio needs to be large enough to allow a receiving end chip downstream of the fiber transmission to obtain a sufficiently low bit error rate. Similar to the significance of the presence of APC, the threshold current of the laser increases with an increase in ambient temperature, the light emission efficiency decreases, and the extinction ratio decreases. The Automatic Extinction Ratio control (AER) technique maintains the Extinction Ratio of the laser by detecting the Extinction Ratio information of the laser and by feeding back and adjusting the Modulation Current (Modulation Current) of the laser.

In a conventional test circuit, both APC and AER need to build a complete photoelectric test environment, including devices and equipment such as a Laser Driver (LDD), a Laser Diode (LD), a Monitor PD (MPD), an optical fiber, an optical oscilloscope, and an error detector, as shown in fig. 1. And obtaining indexes such as average light power, extinction ratio and the like of the optical eye through an optical oscilloscope. In some testing applications, such as reliability testing, the testing environment increases the testing cost and difficulty.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a test method based on an APC (automatic Power control) and AER (automatic energy recovery) loop electrical measurement circuit, and relates to a novel test circuit related to APC and AER functions in the pure electrical field. The laser, the Monitoring PD (MPD), the optical fiber and the optical oscilloscope are not needed, the laser and the MPD are replaced by common separation devices, and the electric oscilloscope is used for detecting electric signals, so that the cost and the complexity of the APC loop test and the AER loop test can be reduced to a great extent.

The specific implementation content of the invention is as follows:

the invention provides a test method based on an APC (automatic Power control) and AER (automatic energy recovery) loop electrical measurement circuit, which is used for detecting an electrical signal;

the APC loop and AEC loop electrical measurement circuit comprises an electrical oscilloscope, error code instrument equipment, a laser driver, an analog conversion circuit and a VEB/R current generation circuit;

the analog conversion circuit comprises a resistor R1, a resistor R2 and a triode Q1;

the error code instrument equipment is connected with the laser driver, the resistor R1 is connected with the laser driver after being connected with a VDD power supply, and the resistor R1 is respectively used for transmitting IBIAS direct current for determining the average light power of the laser and IMOD alternating current for determining the extinction ratio of the laser;

the resistor R2 is connected with the emitter of the triode Q1 after being connected with a VDD power supply; the base electrode of the triode Q1 is connected with the resistor R1, the collector electrode of the triode Q1 is connected with the output end of the VEB/R current generating circuit, receives the VER/R current sent by the VEB/R current generating circuit, then is connected with the laser driver, and sends IMPD current to the laser driver;

the triode Q1 is a PNP type triode;

the method is particularly operable to:

step 1: simulating a laser by using a resistor R1 as an on-resistance, and marking the current flowing through a resistor R1 as I1;

step 2: detecting the voltage V1 at the base electrodes of the resistor R1 and the triode Q1 by using an electrical oscilloscope, and calculating the value of the current I1 through the voltage V1 and the resistor R1;

and step 3: a voltage-to-current conversion circuit is formed by using a resistor R2 and a transistor Q1, and the proportion of a flowing current I1 and extraction of an error term are carried out; marking the current flowing through the resistor R2 and the triode Q1 as I2;

and 4, step 4: setting the ratio of the resistors R2 and R1 so as to simulate the mirror proportion relation between the current I1 and the IMPD current;

and 5: the VEB/R current is generated by using a VEB/R current generation circuit, is marked as I3, is merged with the current I2 through the compensation of the current I3 as an error term, and is connected to an IMPD interface of the laser driver as an IMPD current;

step 6: the IMPD current is used to implement the auto extinction ratio control AER function and the auto average power control APC function, respectively.

In order to better realize the invention, further, the VEB/R current generating circuit comprises a transistor Q2, a transistor Q3, a transistor Q4, a transistor Q5, a resistor R22, a resistor R23, an NMOS tube M1 and an NMOS tube M2;

the emitter of the triode Q4 is connected with the collector of the triode Q5; the base electrodes of the triode Q2, the triode Q3 and the triode Q4 are connected together; the resistor R22 is connected with the emitter of the triode Q2 after being connected with a VDD power supply; the resistor R23 is connected with the emitter of the triode Q3 after being connected with a VDD power supply; the emitter of the triode Q5 is connected with a VDD power supply; the base electrode of the triode Q5 is connected with the emitter electrode of the triode Q4; the base electrode of the triode Q4 is also connected with the collector electrode in a lap joint manner;

the NMOS tube M1 and the NMOS tube M2 are grounded to form a clamping current mirror and are respectively connected with a collector electrode of the triode Q3 and a collector electrode of the triode Q4;

the collector of the triode Q2 is connected with the collector of the triode Q1;

the triode Q2, the triode Q3, the triode Q4 and the triode Q5 are PNP type triodes and are the same triodes as the triode Q1; the NMOS tube M1 and the NMOS tube M2 are the same NMOS tube; the resistor R22 and the resistor R23 are the same resistor;

the specific operation of generating the VEB/R current in the step 5 is as follows:

step 5.1: a current mirror with the ratio of 1:1 is formed by an NMOS tube M1 and an NMOS tube M2 of the clamping current mirror, the currents of emitting electrodes of a triode Q3 and a triode Q4 are adjusted to be equal, and the currents of a resistor R23 and a triode Q5 are also adjusted to be equal;

step 5.2: the transistor Q3 and the transistor Q4 are provided as the same transistor, and serve as a clamping voltage, so that the voltage VEB of the resistor R23 and the transistor Q5 are equal;

step 5.3: a transistor Q2 and a resistor R22 are used as the copy of a branch of the transistor Q3 and the resistor R23, so that the current of VEB/R22, namely the VEB/R current, is also the current I3.

To better implement the present invention, further, the calculation conversion formula between the voltage V1 and the current I1 is as follows:

in the formula, V1 is the voltage at the base of the resistor R1 and the transistor Q1, VDD is the input power voltage, I1 is the current flowing through the resistor R1, and R1 is the resistance of the resistor R1.

To better implement the present invention, further, the formula of the current I2 flowing through the resistor R2 is as follows:

in the formula, VDD is an input power voltage, I2 is a current flowing through the resistor R2, R2 is a resistance value of the resistor R2, VEB is a voltage value at the resistor R22, the resistor R23 and the transistor Q5, R is a resistance value of the resistor R22 and the resistor R23, and I1 is a current flowing through the resistor R1.

In order to better implement the present invention, further, the calculation formula of the IMPD current is as follows:

in order to better implement the present invention, further, the current I1 is a sum of IBIAS direct current and IMOD alternating current, and a specific expression is as follows:

in order to better implement the present invention, further, the resistance value of the resistor R1 ranges from 10 Ω to 15 Ω.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the invention adopts a common separation device to replace a laser and Monitor PD (MPD), does not need to arrange the laser, the MPD, an optical fiber and an optical oscilloscope, and only detects an electric signal through an electric oscilloscope, thereby greatly reducing the cost and the complexity of APC and AER loop tests. The test is realized in a convenient and quick lap joint mode with low cost. The test circuit and the test method can be easily realized by the public.

Drawings

FIG. 1 is a prior art circuit schematic;

FIG. 2 is a schematic circuit diagram of the present invention;

FIG. 3 is a simulation waveform for the 1Gbps PRBS7 mode;

fig. 4 is a simulation waveform at a data rate of 100 Mbps.

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and therefore should not be considered as a limitation to the scope of protection. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1:

the embodiment provides a test method based on an APC (automatic Power control) and AER (automatic energy recovery) loop electrical measurement circuit, which is used for detecting electrical signals; as shown in figure 2 of the drawings, in which,

the APC loop and AEC loop electrical measurement circuit comprises an electrical oscilloscope, error code instrument equipment, a laser driver, an analog conversion circuit and a VEB/R current generation circuit;

the analog conversion circuit comprises a resistor R1, a resistor R2 and a triode Q1;

the error code instrument equipment is connected with the laser driver, the resistor R1 is connected with the laser driver after being connected with a VDD power supply, and the resistor R1 is respectively used for transmitting IBIAS direct current for determining the average light power of the laser and IMOD alternating current for determining the extinction ratio of the laser;

the resistor R2 is connected with the emitter of the triode Q1 after being connected with a VDD power supply; the base electrode of the triode Q1 is connected with the resistor R1, the collector electrode of the triode Q1 is connected with the output end of the VEB/R current generating circuit, receives the VER/R current sent by the VEB/R current generating circuit, then is connected with the laser driver, and sends IMPD current to the laser driver;

the triode Q1 is a PNP type triode;

the method is particularly operable to:

step 1: simulating a laser by using a resistor R1 as an on-resistance, and marking the current flowing through a resistor R1 as I1;

step 2: detecting the voltage V1 at the base electrodes of the resistor R1 and the triode Q1 by using an electrical oscilloscope, and calculating the value of the current I1 through the voltage V1 and the resistor R1;

and step 3: a voltage-to-current conversion circuit is formed by using a resistor R2 and a transistor Q1, and the proportion of a flowing current I1 and extraction of an error term are carried out; marking the current flowing through the resistor R2 and the triode Q1 as I2;

and 4, step 4: setting the ratio of the resistors R2 and R1 so as to simulate the mirror proportion relation between the current I1 and the IMPD current;

and 5: the VEB/R current is generated by using a VEB/R current generation circuit, is marked as I3, is merged with the current I2 through the compensation of the current I3 as an error term, and is connected to an IMPD interface of the laser driver as an IMPD current;

step 6: the IMPD current is used to implement the auto extinction ratio control AER function and the auto average power control APC function, respectively.

The working principle is as follows: the error detector device of fig. 2 is used to load the driver of the laser LD with an input signal. An electrical oscilloscope is used for detecting the voltage signal of the node V1. The ratio of the resistances of the resistors R1 and R2 is 1: N, and the ratio of the current on the analog laser to the MPD current is N: 1.

Replacing the LD in fig. 1 with a resistor R1 of about 15 ohms, setting the ratio of R2 and R1 can simulate the mirror ratio relationship between the current I1 and the MPD current IMPD on the LD. Q1 is realized by PNP tube, and a proportion of I1 is extracted, and an error term, VEB/R2 is also carried out, as shown in formula (2). The right half circuit shown in FIG. 2 is used to produce a DC current of VEB/R2 from Q2-Q5, M1-M2, and resistors R22 and R23, as shown in formula (3), to cancel the error term of the proportional current extracted from Q1. In FIG. 2, Q1-Q5 are composed of PNPs of the same type, and M1 and M2 are composed of NMOSs of the same type to form a 1:1 clamp current mirror. The I2 and I3 currents are merged and then flow to the IMPD port of the LDD, which is equivalent to the current IMPD generated by the MPD in fig. 1, and as shown in formula (4), the current IMPD also includes a dc current and an ac current, which are respectively used for implementing APC and AER functions.

The resistor R1 is used for simulating the on-resistance of the laser and is about 10-15 ohms. The current flowing through the resistor R1 is denoted as I1, and includes a direct current IBIAS that determines the average optical power of the laser and an alternating current IMOD that determines the extinction ratio of the laser, as shown in equation (5). The resistor R2 and the PNP tube Q1 form a voltage-to-current conversion circuit, as shown in formula (2), for extracting the current I1 flowing through the laser. Finally, combining I2 and I3 together, as shown in equation (4), cancels the current in the VEB/R2 portion

The observation point is changed from the laser in fig. 1 to the voltage point V1 in fig. 2 through the optical fiber to the optical port of the optical oscilloscope. From V1 and the known values of VDD and R1, V1 can be converted to the actual current flowing through the laser, including the dc current IBIAS that determines the average optical power of the laser and the ac current IMOD that determines the extinction ratio of the laser.

(1)

(2)

(3)

(4)

(5)

(6)。

Example 2:

in this embodiment, on the basis of embodiment 1 above, in order to better implement the present invention, further, the VEB/R current generating circuit includes a transistor Q2, a transistor Q3, a transistor Q4, a transistor Q5, a resistor R22, a resistor R23, an NMOS transistor M1, and an NMOS transistor M2;

the emitter of the triode Q4 is connected with the collector of the triode Q5; the base electrodes of the triode Q2, the triode Q3 and the triode Q4 are connected together; the resistor R22 is connected with the emitter of the triode Q2 after being connected with a VDD power supply; the resistor R23 is connected with the emitter of the triode Q3 after being connected with a VDD power supply; the emitter of the triode Q5 is connected with a VDD power supply; the base electrode of the triode Q5 is connected with the emitter electrode of the triode Q4; the base electrode of the triode Q4 is also connected with the collector electrode in a lap joint manner;

the NMOS tube M1 and the NMOS tube M2 are grounded to form a clamping current mirror and are respectively connected with a collector electrode of the triode Q3 and a collector electrode of the triode Q4;

the collector of the triode Q2 is connected with the collector of the triode Q1;

the triode Q2, the triode Q3, the triode Q4 and the triode Q5 are PNP type triodes and are the same triodes as the triode Q1; the NMOS tube M1 and the NMOS tube M2 are the same NMOS tube; the resistor R22 and the resistor R23 are the same resistor;

the specific operation of generating the VEB/R current in the step 5 is as follows:

step 5.1: a current mirror with the ratio of 1:1 is formed by an NMOS tube M1 and an NMOS tube M2 of the clamping current mirror, the currents of emitting electrodes of a triode Q3 and a triode Q4 are adjusted to be equal, and the currents of a resistor R23 and a triode Q5 are also adjusted to be equal;

step 5.2: the transistor Q3 and the transistor Q4 are provided as the same transistor, and serve as a clamping voltage, so that the voltage VEB of the resistor R23 and the transistor Q5 are equal;

step 5.3: a transistor Q2 and a resistor R22 are used as the copy of a branch of the transistor Q3 and the resistor R23, so that the current of VEB/R22, namely the VEB/R current, is also the current I3.

The working principle is as follows: the NMOS tube M1-2, the PNP tube Q3-5, the resistor R22 and the resistor R23 form a VEB/R current generating circuit. M1 and M2 constitute a 1:1 current mirror, so that the emitter currents of Q3 and Q4 are equal, and the currents of R23 and Q5 are equal. Q3 and Q4 act as clamp voltages, and since their currents are the same and their models are the same, VEB for Q3 and Q4 are the same, and finally the voltage drop across resistor R23 is equal to the voltage drop of Q5, i.e., VEB. Q2 and resistor R22 are used as the copy of the circuit of Q3 and R23 to draw the current of VEB/R2, as shown in formula (3).

Other parts of this embodiment are the same as those of embodiment 1, and thus are not described again.

Example 3:

this embodiment is based on any of the above embodiments 1-2, and fig. 3 shows a simulation waveform of 1Gbps PRBS7 mode. The simulation software used is Spectre, and the waveform screenshot comes from a simulation result display window. R1=40 ohms, R2=800 ohms, IMOD =20mA, IBIAS =40 mA. I1 is the current through the laser, IBIAS + IMOD, V1 is the base voltage of Q1, V2 is the emitter voltage of Q1, and IMPD is I2+ I3, i.e. the MPD current sent to the LDD for APC and AER feedback in FIG. 2.

From the simulated waveform, I1 contained 40mA of IBIAS and 20mA of IMOD. IMPD contains an average current of 2mA and an alternating current of 0.81 mA. Since R2/R1=20, IMPD should theoretically consist of an average current of 2mA and an alternating current of 1 mA. The ac current on IMPD has a 0.19mA loss, limited by the parasitic capacitance from Q1. Parasitic capacitance can cause loss of ac capacitance. Therefore, the PNP should be selected with care that its parasitic capacitance cannot be too large, especially the base capacitance. The smaller the parasitic capacitance is, the smaller the alternating current loss of the IMPD is, and the proportional mirror of the laser current can be restored more accurately.

Other parts of this embodiment are the same as any of embodiments 1-2 described above, and thus are not described again.

Example 4:

in this embodiment, based on any of the above embodiments 1-3, the ac current loss of IMPD is reduced as the data rate is lower, as shown in fig. 4, which is a simulation waveform of the same test circuit at a data rate of 100 Mbps. Simulation software is used as Spectre, and the waveform screenshot comes from a simulation result display window. IMPD consists of an average current of 2mA and an ac current of 0.92mA, with an ac current loss of 80 uA.

Other parts of this embodiment are the same as any of embodiments 1 to 3, and thus are not described again.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.

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