Apparatus for driving electro-optic modulator

文档序号:1343815 发布日期:2020-07-17 浏览:16次 中文

阅读说明:本技术 用于驱动电光调制器的设备 (Apparatus for driving electro-optic modulator ) 是由 安东尼奥·穆西奥 卢卡·皮亚宗 于 2017-12-15 设计创作,主要内容包括:本发明涉及一种用于驱动电光调制器110的设备100。所述设备100包括分布式放大器101和分布式电流源102。所述分布式电流源102包括用于供电电压的DC输入103和与所述分布式放大器101连接的M个DC输出104,其中,M为大于等于1的自然数。所述分布式放大器101包括RF输入105、与所述电光调制器110连接的RF输出106以及与所述分布式电流源102的M个DC输出104连接的至少M个DC输入107。(The invention relates to an apparatus 100 for driving an electro-optical modulator 110. The device 100 comprises a distributed amplifier 101 and a distributed current source 102. The distributed current source 102 comprises a DC input 103 for a supply voltage and M DC outputs 104 connected to the distributed amplifier 101, where M is a natural number greater than or equal to 1. The distributed amplifier 101 comprises an RF input 105, an RF output 106 connected to the electro-optical modulator 110 and at least M DC inputs 107 connected to the M DC outputs 104 of the distributed current source 102.)

1. An apparatus (100) for driving an electro-optic modulator (110), the apparatus (100) comprising:

a distributed amplifier (101) and a distributed current source (102); wherein

The distributed current source (102) comprises a DC input (103) for a supply voltage and M DC outputs (104) connected to a distributed amplifier (101), wherein M is a natural number greater than or equal to 1;

the distributed amplifier (101) comprises a Radio Frequency (RF) input (105), an RF output (106) for connection to the electro-optical modulator (110), and at least M DC inputs (107) connected to the M DC outputs (104) of the distributed current source (102).

2. The apparatus (100) of claim 1, wherein:

the distributed current source (102) comprises M DC current sources (300) connected in parallel, each DC current source (300) being connected to one of the DC input (103) and the M DC outputs (104).

3. The apparatus (100) of claim 2, wherein:

the M DC current sources (300) are M transistors (400);

an output terminal of each transistor (400) is connected to the DC input (103), and an input terminal of the transistor (400) is connected to one of the M DC outputs (104) and a control terminal of the transistor (400).

4. The apparatus (100) of claim 3, wherein:

the M transistors (400) are field effect transistors or bipolar transistors.

5. The apparatus (100) according to claim 3 or 4, wherein:

the input terminal of each transistor (400) is directly connected to the control terminal of the transistor (400).

6. The apparatus (100) according to claim 3 or 4, wherein:

the input terminal of each transistor (400) is connected to the control terminal of the transistor (400) via a constant voltage source (500).

7. The apparatus (100) according to one of claims 1 to 6, characterized in that:

-said distributed amplifier (101) comprises at least a further DC input (301) for a supply voltage;

the DC input (103) of the distributed current source (102) is interconnected with the other DC input (301) of the distributed amplifier (102).

8. The apparatus according to one of claims 1 to 6, characterized in that:

-the distributed amplifier (101) comprises at least a further DC input (600) for a supply voltage;

the DC input (103) of the distributed current source (102) is not connected to the other DC input (600) of the distributed amplifier (101).

9. The apparatus (100) according to claim 7 or 8, wherein:

-the distributed amplifier (101) comprises N transistors (302) connected in parallel and an output transmission line (303) connected between the further DC input (301/600) and the RF output (106), where N is a natural number equal to or greater than M;

the output terminals of the N transistors (302) and the M DC outputs (104) of the distributed current source (102) are connected to the output transmission line (303), respectively.

10. The apparatus (100) of claim 9, wherein:

the distributed amplifier (101) comprises an input transmission line (304) connected between the RF input (105) and a reference voltage port (305);

the control terminals of the N transistors (302) are connected to the input transmission line (304).

11. The apparatus (100) according to claim 9 or 10, wherein:

the N transistors (302) are field effect transistors or bipolar transistors.

12. A system (200), comprising:

the device (100) according to one of claims 1 to 11; and

an electro-optical modulator (110) comprising an RF input (201) connected to an RF output (106) of the apparatus (100).

13. The system (200) of claim 12, wherein:

the electro-optical modulator (110) comprises a DC input (202) for a supply voltage, the DC input (202) of the electro-optical modulator (110) being connected to the DC input (103) of the distributed current source (102).

Technical Field

The present invention relates to an apparatus for driving an electro-optical modulator. The invention also relates to a system comprising said device and said electro-optical modulator. The system may be used in an optical transmitter. Accordingly, the invention also contemplates a transmitter employing the apparatus and system, respectively. In particular, the performance of the electro-optic modulator, and thus the transmitter, is improved by the apparatus and system of the present invention.

Background

A transmitter for high-speed optical communication is basically implemented by cascading three blocks as shown in fig. 7. The first block is a digital source, the second block is a driver amplifier for increasing the power level of the electrical signal provided by the source, and the third block is an electro-optical modulator for converting the electrical signal into an optical signal to be transmitted in the optical fiber.

In most conventional transmitters, the electro-optic modulator (implemented, for example, as an electro-absorption modulated laser (EM L)) requires a DC voltage, therefore, it is of particular interest to have a drive amplifier DC coupled to the output to avoid the use of a bias between the drive amplifier and the electro-optic modulator, because they consume significant area and limit integration capability.

Another challenge is that the driver amplifiers employed should exhibit matched output impedance, since the electro-optic modulator is then less susceptible to signal attenuation. This is because the matched output impedance of the driver amplifier absorbs reflections from the interconnections, such as bond wires and bond sites, between the driver amplifier and the electro-optic modulator. In fact, this is important to achieve high speed, high data rate optical communications.

In summary, the high performance driver amplifier that contributes to the realization of a very high speed, highly integrated transmitter for optical communications has the following features:

DC-coupled output.

2. A DC bias current independent of the DC coupled output.

Matching output impedance (with an electro-optic modulator).

In one conventional approach, a driver amplifier having the above highlighted features is implemented based on a distributed amplifier with separately biased segments. The block diagram is shown in fig. 8. The solution includes a distributed amplifier with a non-integrated RF coil. This makes the path of the DC bias current of the distributed amplifier different from that of the electro-optic modulator and the performance of the distributed amplifier is not affected due to the high impedance of the RF coil.

Disclosure of Invention

In view of the above challenges and shortcomings, the present invention is directed to improving conventional driver amplifiers. It is therefore an object of the present invention to provide an apparatus for driving an electro-optical modulator with improved performance. In particular, the device should allow a high integration and an unlimited low frequency cut-off. Furthermore, the device should not show voltage peaks and should be able to operate with only a single DC power supply. For this reason, the device should not include any inductance in the bias network.

The object of the invention is achieved by the solution presented in the appended independent claims. Advantageous implementations of the invention are further defined in the dependent claims.

The main idea of the invention is a distributed current source added to a distributed amplifier. The invention thus enables a DC-coupled output distributed amplifier with a DC bias current that is independent of the DC bias current of the electro-optical modulator.

A first aspect of the invention provides an apparatus for driving an electro-optic modulator. The apparatus includes a distributed amplifier and a distributed current source. The distributed current source includes a DC input for a supply voltage and M DC outputs connected to the distributed amplifier, where M is a natural number greater than or equal to 1. The distributed amplifier includes a Radio Frequency (RF) input, an RF output for connection to the electro-optic modulator, and at least M DC inputs connected to the M DC outputs of the distributed current source.

A distributed amplifier is an amplifier having several amplifier stages connected together to form a transmission line with gain. The input of each stage (except the first stage) is the output of the previous stage. The gain on the transmission line is thus the sum of the gains of each stage. The bandwidth of the distributed amplifier is the bandwidth of each stage. The main difference with a cascode amplifier is that the input to each stage in the cascode amplifier is the original signal supplied to the amplifier.

In the apparatus of the first aspect, the M DC inputs of the distributed amplifier may be one-to-one connected with the M DC outputs. That is, each of the M DC inputs may be connected to a corresponding one of the M DC outputs of the distributed current source.

The device of the first aspect may be an integrated circuit, for example a Monolithic Microwave Integrated Circuit (MMIC).

The device of the first aspect combines a (dc-coupled output) distributed amplifier and a distributed current source. By this combination, the DC bias current of the distributed amplifier is independent of the DC bias current of the electro-optic modulator. Furthermore, due to the distributed nature of the distributed current sources, the inherent parasitic capacitance of the distributed current sources is minimized, so that the high frequency response of the distributed amplifier is not affected. Thus, by the apparatus, the performance of the electro-optical modulator to which it is connected is maximized, thereby improving the performance of a transmitter for optical communication that includes the apparatus and the electro-optical modulator.

In particular, the device of the first aspect has the following advantages compared to conventional driver amplifiers:

1. high integration level: for example, the device of the first aspect may be easily implemented in MMIC technology.

2. Unlimited low frequency cut-off: the device of the first aspect does not have a low frequency cut-off, as it does not include any inductance in the bias network.

3. No voltage peak: the device of the first aspect does not generate any voltage peaks even when the distributed amplifier is suddenly pinched off. This is because the distributed current source does not store any energy like an RF coil or the like (or a conventional driver amplifier as shown in fig. 8).

4. Single DC power supply: the apparatus of the first aspect may be implemented using a single DC voltage source.

In one implementation of the first aspect, the distributed current source comprises M DC current sources connected in parallel, each DC current source being connected to one of the DC input and the M DC outputs.

The M DC current sources provide a distributed nature of the current sources and allow for a DC bias current for the distributed amplifiers that is independent of a DC bias current of an electro-optic modulator connected to the device.

In another implementation form of the first aspect, the M DC current sources are M transistors, an output terminal of each transistor is connected to the DC input, and an input terminal of the transistor is connected to one of the M DC outputs and a control terminal of the transistor.

The M transistors provide a solution that is easy to integrate, for example, in MMIC technology.

In another implementation form of the first aspect, the M transistors are field effect transistors or bipolar transistors.

In another implementation form of the first aspect, the input terminal of each transistor is directly connected to the control terminal of the transistor.

This direct connection makes the device particularly easy to implement.

In another implementation form of the first aspect, the input terminal of each transistor is connected to the control terminal of the transistor by a constant voltage source.

Thus, the input terminal and the control terminal of the transistor may advantageously be kept at well-defined (and controllable) constant voltages.

In another implementation form of the first aspect, the distributed amplifier comprises at least a further DC input for a supply voltage, the DC input of the distributed current source being interconnected with the further DC input of the distributed amplifier.

Thus, the DC inputs of the distributed current source and the amplifier may each be adapted to be connected to the same supply voltage source. Thus, only one DC voltage source is required to operate the device. This may even be shared with the electro-optic modulator.

In another implementation form of the first aspect, the distributed amplifier comprises at least one further DC input for a supply voltage, the DC input of the distributed current source being unconnected to the further DC input of the distributed amplifier.

That is, the DC inputs of the distributed current source and the amplifier are separate from each other. In other words, they are separate DC inputs, not related to each other in any way. Thus, the DC inputs of the distributed current source and the amplifier may be used for connection to separate supply voltage sources. Thus, different DC voltage sources may be used to operate the device. They may be different from the DC voltage source of the electro-optic modulator.

In another implementation form of the first aspect, the distributed amplifier comprises N transistors connected in parallel and an output transmission line connected between the further DC input and the RF output, where N is a natural number equal to or greater than M; the output terminals of the N transistors and the M DC outputs of the distributed current source are connected to the output transmission line, respectively.

The N transistors provide different amplifier stages than the distributed amplifier, producing gain on the output transmission line.

In another implementation form of the first aspect, the distributed amplifier comprises an input transmission line connected between the RF input and a reference voltage port, and the control terminals of the N transistors are connected to the input transmission line.

In another implementation form of the first aspect, the N transistors are field effect transistors or bipolar transistors.

A second aspect of the invention provides a system comprising an apparatus as described in any of the first aspect and its implementations, and an electro-optical modulator comprising an RF input connected to an RF output of the apparatus.

In one implementation of the second aspect, the electro-optical modulator comprises a DC input for a supply voltage, the DC input of the electro-optical modulator being connected to the DC input of the distributed current source.

Accordingly, all the advantages and effects of the device of the first aspect can be achieved by the system of the second aspect.

It should be noted that all devices, elements, units and means described in the present application may be implemented in software or hardware elements or any combination thereof. All steps performed by the various entities described in the present application and the functions described to be performed by the various entities are intended to indicate that the respective entities are adapted or arranged to perform the respective steps and functions. Although in the following description of specific embodiments specific functions or steps performed by an external entity are not reflected in the description of specific elements of the entity performing the specific steps or functions, it should be clear to a skilled person that these methods and functions may be implemented in respective hardware or software elements or any combination thereof.

Drawings

The foregoing aspects and many of the attendant aspects of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates an apparatus provided by an embodiment of the present invention;

FIG. 2 illustrates a system provided by an embodiment of the invention;

FIG. 3 illustrates an apparatus provided by an embodiment of the invention;

FIG. 4 illustrates an apparatus provided by an embodiment of the present invention;

FIG. 5 illustrates an apparatus provided by an embodiment of the invention;

FIG. 6 illustrates an apparatus provided by an embodiment of the invention;

FIG. 7 illustrates one implementation of a conventional transmitter;

fig. 8 shows a conventional driver amplifier.

Detailed Description

Fig. 1 illustrates an apparatus 100 provided by an embodiment of the present invention. The device 100 is used to drive an electro-optical modulator 110 that does not belong to the device 100. The device 100 comprises a distributed current source 102 and a distributed amplifier 101 and is thus configured as a drive amplifier for an electro-optical modulator 110.

The distributed current source 102 comprises a DC input 103 for connection to a supply voltage, here denoted VDD. The supply voltage VDD may also be connected to the electro-optic modulator 110. Furthermore, the distributed current source 102 comprises M DC outputs 104 connected to the distributed amplifier 101. M is a natural number of 1 or more.

Accordingly, the distributed amplifier 101 comprises at least M DC inputs 107 connected to the M DC outputs 104 of the distributed current source 102. In fig. 1, the connections between the M DC outputs 104 and the M DC inputs 107 are labeled i1, i2, … …, iM. The distributed amplifier 101 also includes a Radio Frequency (RF) input 105, which RF input 105 may be connected to and used to receive electrical signals from a digital source. Further, the distributed amplifier 101 comprises an RF output 106 for connection to an electro-optical modulator 110.

Fig. 2 illustrates a system 200 provided by an embodiment of the invention. The system 200 includes the apparatus 100 and the electro-optic modulator 110. The device 100 of fig. 2 is therefore based on the device 100 of fig. 1, wherein like elements have like reference numerals and functions. The apparatus 100 of fig. 2 may also be provided separately (i.e., without the electro-optic modulator 110). Conveniently, the device 100 of fig. 2 is an integrated circuit such as an MMIC. That is, the distributed current source 102 and the distributed amplifier 101 are integrated with each other, for example, in MMIC technology.

The RF input 105 of the distributed amplifier receives an input voltage (labeled Vin), which may be a signal from a source, and the RF output 106 outputs a voltage (labeled Vout), which is an amplified input voltage, to the RF input 201 of the electro-optic modulator 110. the electro-optic modulator 110 also includes a DC input 202 for connection to a supply voltage conveniently, in order to use only one supply voltage, here VDD, the DC input 202 of the electro-optic modulator 110 is connected to the DC input 103 of the device 100, in particular at least to the DC input 103 of the distributed current source 102. the electro-optic modulator 110 may be an EM L.

Fig. 3 illustrates an apparatus 100 provided by an embodiment of the present invention. The device 100 is based on the device 100 shown in fig. 1 and 2, respectively. Like elements have like reference numerals and functions.

The distributed amplifier 101 in the device 100 shown in fig. 3 comprises N transistors 302 connected in parallel. N is a natural number greater than or equal to M. The N transistors 302 are labeled Q1, Q2, … …, QN, and are denoted herein as field-effect transistors (FETs). However, a Bipolar Junction Transistor (BJT) may be used.

Further, the distributed amplifier 101 includes an output transmission line 303. This output transmission line 303 is connected between a further DC input 301 of the distributed amplifier 101, which further DC input 301 is intended to be connected to a supply voltage (here VDD), and the RF output 106 for providing Vout to the electro-optical modulator 110. The output terminals D of the N transistors 302 (the "drain" of the FET and the "collector" of the BJT) and the M DC outputs 104 of the distributed current source 102 are connected to an output transmission line 303, respectively.

The distributed amplifier 101 further comprises an input transmission line 304, the input transmission line 304 being connected between the RF input 105 for receiving Vin and a reference voltage port 305 for connecting a reference voltage (here labeled VGG). The reference voltage may also be grounded. The control terminals G (the "gates" of the FETs and the "bases" of the BJTs) of the N transistors 302 are connected to an input transmission line 304. The input terminals S of the N transistors 302 (the "source" of the FET and the "emitter" of the BJT) may be grounded.

Further, distributed amplifier 101 includes two resistors, labeled RG and RD, with resistor RD connected between DC input 301 and output transmission line 303, and resistor RG connected between input transmission line 304 and reference voltage port 305. Therefore, voltage drops occur on the resistor RG and the resistor RD, respectively. It is noted that the device 100 may even comprise two DC voltage sources VGG and VDD. These voltage sources may be separate from the device 100.

Further, the distributed amplifier 101 in the device 100 shown in fig. 3 comprises N +2 inductances, which are labeled L G1, L G2, … …, L0 GN +1 and L1D 1, L D2, … …, L DN +1, the inductances L D1, L D2, … …, L DN +1 may be connected in series on the output transmission line 303, the output terminal D of each transistor 302 may be connected with the output transmission line 303 between the two inductances, the inductances L G1, L G2, … …, L GN +1 are connected in series on the input transmission line 304, the control terminal G of each transistor 302 is connected with the input transmission line 304 between the two inductances.

In order to improve the performance of the distributed amplifier itself, conventional distributed amplifiers are also suitable for use in the solution of the invention. The transistors constituting the distributed amplifier may be of FET type or BJT type.

Further, in fig. 3, the distributed current source 102 consists of M DC current sources 300, here the M DC current sources 300 are labeled I1, I2, … …, IM. That is, the distributed current source 102 includes M DC current sources 300 connected in parallel. Thus, each DC current source 300 may be connected to the DC input 103 (and thus VDD as the distributed amplifier 101 and electro-optic modulator 110) and also to one of the M DC outputs 104 of the distributed current source 102. The M DC outputs 104 of the distributed current source 102 may be connected to M output terminals D of the N transistors 302 that make up the distributed amplifier 101.

It can be noted from fig. 3 that the DC bias current of the distributed amplifier 101 is the sum of the currents through the electro-optical modulator 110 and the distributed current source 102, thereby optimizing the bias currents of the electro-optical modulator 110 and the distributed amplifier 101 at the same time, even if they differ in level. Furthermore, the matched output impedance of the distributed amplifier 101 is not affected by the high impedance shown by the DC current source 300 that makes up the distributed current source 102.

Fig. 4 shows an apparatus 100 provided by an embodiment of the present invention. The device 100 is based on the device 100 shown in fig. 3. Like elements have like reference numerals and functions. The device 100 shown in fig. 4 is the simplest way to achieve full integration, for example in MMIC technology.

The device 100 of fig. 4 also comprises at least a distributed amplifier 101 and a distributed current source 102. The distributed current source 102 also includes M DC current sources, each implemented by a transistor 400. The M transistors 400 are labeled T1, T2, … …, TM. In fig. 4, the M transistors 400 are implemented by FETs, however, they may be BJTs.

Each of the M transistors 400 includes an output terminal D (the "drain" of the FET and the "collector" of the BJT) that is connected to the DC input 103 of the distributed current source 102. Further, each transistor 400 comprises an input terminal S (the "source" of the FET and the "emitter" of the BJT) connected to one of the M DC outputs 104 and to a control terminal G (the "gate" of the FET and the "base" of the BJT) of the same transistor 400. That is, the control terminal and the input terminals G and S of each of the M transistors 400 are connected to each other.

The size of each of the M transistors 400 of the distributed current source 102 may be selected to obtain the desired current labeled I1, 12, … …, IM in fig. 3. Each of these currents flows from a DC output 104 of the distributed current source 102 into a DC input 107 of the distributed amplifier 101.

Fig. 5 illustrates an apparatus 100 provided by an embodiment of the present invention. The apparatus 100 is based on fig. 3. Like elements have like reference numerals and functions.

In fig. 5, each of the M transistors 400 of the distributed current source 102 includes a control terminal G and an input terminal S connected by a constant voltage source 500. That is, the control terminal G and the input terminal S of the transistor 400 are not directly connected as shown in fig. 4, but are maintained at a constant voltage value by the constant voltage source 500 labeled VGS1, VGS2, … …, VGSM. Obviously, the direct connection in fig. 4 can be regarded as a special implementation of the indirect connection in fig. 5, where VGS1 ═ VGS2 ═ VGS … … ═ VGSM ═ 0V.

Fig. 6 shows an apparatus 100 provided by an embodiment of the present invention. The apparatus 100 is based on fig. 3. Like elements have like reference numerals and functions.

In fig. 6, the DC voltage source for the distributed current source 102 is labeled VDD2, as opposed to the DC voltage source for the distributed amplifier 101 (labeled VDD3) and/or the DC voltage source for the electro-optic modulator 110 (labeled VDD 1). That is, in fig. 4, the DC input 103 of the distributed current source 102 and the further DC input 301 of the distributed amplifier 102 are connected to each other and to the universal voltage source VDD. In contrast to fig. 4, in fig. 6 the DC input 103 of the distributed current source 102 and the further DC input 600 of the distributed amplifier 101 are not connected to each other. That is, they are independent DC inputs and are connected to different voltage sources. It is noted that the single voltage source in fig. 4 can be regarded as a special implementation of the voltage source in fig. 6, where VDD 1-VDD 2-VDD 3-VDD.

The features of the apparatus 100 shown in fig. 5 and 6, respectively, may also be combined. That is, the device 100 according to an embodiment of the present invention may include a constant voltage source 500 for connecting the control terminal and the input terminals G and S of the transistor 400, and may include different voltage sources for supplying to the distributed current source 102, the distributed amplifier 101, and the electro-optical modulator 110, respectively.

The apparatus 100 and system 200 shown in the above figures may be used in optical transmitters for high-speed optical communications, respectively. That is, the invention also relates to a transmitter comprising the device 100 or the device 100 and the electro-optical modulator 110. Such a transmitter according to an embodiment of the invention is in principle implemented as a conventional transmitter as shown in fig. 7, i.e. the transmitter of the invention may also comprise a digital source. The device 100 may be connected to the source to receive electrical signals from the source through its RF input 105. The apparatus 100 is used to increase the power level of the received electrical signal and output an amplifier signal. The electro-optic modulator 110 may be connected to the apparatus 100 via an RF output 106 and an RF input 201. The electro-optic modulator 110 may be used to convert electrical signals received from the device 100 into optical signals. The optical signal may also be transmitted to an optical fiber or the like.

The invention has been described in connection with various embodiments and implementations as examples. Other variations will be understood and effected by those skilled in the art in practicing the invention, studying the drawings, the disclosure, and the independent claims. In the claims and the description the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

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