CN110224759B - Light emitter - Google Patents
Light emitter Download PDFInfo
- Publication number
- CN110224759B CN110224759B CN201910591044.9A CN201910591044A CN110224759B CN 110224759 B CN110224759 B CN 110224759B CN 201910591044 A CN201910591044 A CN 201910591044A CN 110224759 B CN110224759 B CN 110224759B
- Authority
- CN
- China
- Prior art keywords
- optical
- signal
- termination
- speed differential
- module
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
- H04B10/505—Laser transmitters using external modulation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/54—Intensity modulation
Abstract
The invention discloses a light emitter, comprising: the circuit comprises a current mode logic driving module, a modulator and a termination module; connecting a current mode logic driving module with an input end of the modulator in a direct coupling mode, wherein the current mode logic driving module is used for generating and outputting a high-speed differential driving signal; connecting the output end of the modulator with the input end of the termination module in a direct coupling mode; the modulator is used for modulating the optical signal of the high-speed differential driving signal according to the received high-speed differential driving signal to obtain a modulated optical signal and outputting the modulated optical signal; the termination module is used for performing far-end impedance matching on the received high-speed differential driving signal. The invention has the advantages of saving hardware cost, reducing direct current power consumption, reducing circuit design complexity and being beneficial to high-density multi-channel integrated design.
Description
Technical Field
The invention relates to the technical field of photoelectric communication, in particular to a light emitter.
Background
With the increasing requirement of data communication on bandwidth, silicon-based optical interconnection has high bandwidth and low transmission loss, and the compatibility with an electrical chip becomes an effective way for replacing electrical interconnection as short-distance high-speed high-bandwidth data transmission. The optical transmission link may generally include an optical transmitter, an optical receiver, and an optical transmission medium. The optical transmitter converts an electrical signal into an optical signal, and the required devices mainly comprise an optical source, a driver and an electro-optical modulator.
The modulation method can be divided into direct modulation and external modulation. The Mach-Zehnder Modulator (MZM) is a widely used external Modulator, and has the characteristics of simple modulation mode, narrow output optical signal line, strong anti-interference capability and insensitivity to temperature change. A Mach-Zehnder Modulator has two longer optical phase shifters, each driven with a traveling Wave electrode (transmission line electrode), also known as a traveling Wave Mach-Zehnder Modulator (TW MZM). The driver amplifies the previous stage data electric signal to enough amplitude, inputs the signal to the traveling wave electrode of the Mach-Zehnder modulator, and modulates the optical signal.
The existing driver structure is connected with the traveling wave Mach-Zehnder modulator in an AC coupling Mode and mainly comprises a traditional Current Mode Logic (CML) driver, a direct Current Bias (Bias-Tee) module and a traveling wave Mach-Zehnder modulator connecting and terminating module; the AC coupling mode can independently adjust the bias voltage of the traveling wave Mach-Zehnder modulator, and the working bias states of the current mode logic driving module and the traveling wave Mach-Zehnder modulator do not interfere with each other. However, the inductance capacitance of the dc bias module is large, and usually additional components are required, which occupies a large area of the circuit structure design, and is not favorable for the circuit structure design of the high-density multi-channel photoelectric integration.
The existing optical transmitter design mainly includes an open-drain (open-drain) driver, a traveling wave mach-zehnder modulator and a far-end load. The open-drain driver is designed to have stronger optical signal reflection without a near-end termination resistor, so that the transmission integrity of the optical signal is influenced, and meanwhile, larger direct current exists on a transmission line electrode of the traveling wave Mach-Zehnder modulator, so that the direct current power consumption is increased, the device is heated, the operation stability of the device is reduced, and the service life of the device is prolonged.
Disclosure of Invention
The invention aims to provide a light emitter, which is used for solving the problems of high direct current power consumption and high circuit complexity of the light emitter in the prior art, and the problem that the light emitter occupies an increased area of a light emitter circuit and is not beneficial to high-density multi-channel integrated design.
In order to solve the problems, the invention is realized by the following technical scheme:
an optical transmitter, comprising: the circuit comprises a current mode logic driving module, a modulator and a termination module; connecting the current mode logic driving module with the input end of the modulator in a direct coupling mode, wherein the current mode logic driving module is used for generating and outputting a high-speed differential driving signal; connecting the output end of the modulator with the input end of the termination module in a direct coupling mode; the modulator is used for modulating the optical signal of the high-speed differential driving signal according to the received high-speed differential driving signal to obtain a modulated optical signal and outputting the modulated optical signal; the termination module is used for performing far-end impedance matching on the received high-speed differential driving signal.
Further, the current-mode logic driving module further includes: a load resistor, a cascode structure, an input pair and a tail current source,
the first end of the load resistor is connected to the working voltage VCC of the current mode logic driving module, and the second end of the load resistor is connected with the drain electrode of the cascode structure;
the source electrode of the cascode structure is connected with the collector electrode of the input geminate transistor;
the emitter of the input pair tube is grounded through the tail current source;
the load resistor is used for performing near-end impedance matching on the high-speed differential driving signal and converting a current signal generated by the input pair transistors into a high-speed differential voltage signal;
the cascode structure is used for isolating the drain output end of the input pair transistor and the output end of the current mode logic driving module so as to reduce the influence of the Miller effect;
the input pair transistors are used for converting the high-speed differential voltage signals into high-speed differential driving signals;
the tail current source is used for setting the output swing of the high-speed differential driving signal.
Further, the load resistor comprises first load resistors R connected in parallel with each otherL1And a second load resistor RL2；
The first load resistor RL1And a second load resistor RL2The first ends of the current mode logic driving modules are respectively connected to the working voltage VCC of the current mode logic driving module;
the first load resistor RL1And a second load resistor RL2Respectively with the cascode junction
A drain connection of the structure;
the cascode structure comprises a first field effect transistor M with interconnected gatesc1And a secondField effect transistor Mc2；
The input pair transistors comprise a first bipolar junction transistor Q1And a second bipolar junction transistor Q2(ii) a Wherein the first bipolar junction transistor Q1The base of the transistor is inputted with a positive voltage signal VinpSaid second bipolar junction transistor Q2The base of the voltage signal V is input with negative polarityinn。
Further, the modulator is a traveling wave Mach-Zehnder modulator.
Further, the modulator includes: the optical phase shifter comprises a first optical phase shifter, a second optical phase shifter, an input optical splitter and an output optical combiner;
the first optical phase shifter comprises a first transmission line electrode and a second transmission line electrode;
the second optical phase shifter comprises a third transmission line electrode and a fourth transmission line electrode;
one end of the second transmission line electrode and the second load resistor RL2The other end of the second end connection is connected with the input end of the termination module;
one end of the fourth transmission line electrode is the first load resistor RL1The other end of the second end connection is connected with the input end of the termination module;
the first transmission line electrode and the third transmission line electrode are connected in parallel and switched in a bias voltage VBIAS；
The input optical splitter is used for equally dividing the optical signal into two branches of optical signals and outputting the optical signals;
the first optical phase shifter and the second optical phase shifter are used for modulating the two branch optical signals according to the high-speed differential driving signal respectively, and correspondingly loading digital information carried by the high-speed differential driving signal into the two branch optical signals to obtain and output two modulated branch optical signals;
and the output optical combiner is used for combining the received two paths of modulated branch optical signals into one path of modulated optical signal and outputting the modulated optical signal.
Further, the modulator further includes: an input optical interface and an output optical interface;
the input optical interface is connected with the input optical splitter and is used for inputting the optical signal to the input optical splitter;
the output optical interface is connected with the output optical combiner and used for outputting one path of the modulated optical signal.
Further, the input optical splitter is specifically a half optical splitter, and is configured to divide the optical signal into 1: 1 into two branch optical signals;
the output optical combiner is specifically a two-in-one optical combiner, and is configured to combine the two paths of modulated branch optical signals to obtain one path of modulated optical signal.
Furthermore, at least one PN junction optical waveguide is arranged between the first transmission line electrode and the second transmission line electrode at intervals;
at least one PN junction optical waveguide is arranged between the third transmission line electrode and the fourth transmission line electrode at intervals.
Further, the termination module includes: first terminating resistor R1And a second terminating resistor R2And a termination capacitor CT；
The first termination resistor R1And a second terminating resistor R2Are connected in parallel, the first termination resistor R1Is connected to the fourth transmission line electrode, and has a second end connected to the terminating capacitor CTIs connected with the first end of the first connecting pipe;
the second termination resistor R2Is connected to the second transmission line electrode, and has a second end connected to the terminating capacitor CTIs connected with the first end of the first connecting pipe;
the termination capacitor CTThe second end of the second terminal is connected to the working voltage VCC of the termination module.
Further, the first termination resistor R1And a second terminating resistor R2For performing far-end differential mode impedance matching on high-speed driving signals, the first termination resistor R1And a second endConnecting resistor R2Respectively, is consistent with the characteristic impedance of the first optical phase shifter and the second optical phase shifter.
Further, the method also comprises the following steps: applying the bias voltage VBIASAnd the bias voltage of the first optical phase shifter and the bias voltage of the second optical phase shifter are adjusted by adjusting the common-mode direct-current level of the high-speed differential driving signal output by the current mode logic driving module.
Further, the bias voltages of the first optical phase shifter and the second optical phase shifter are the bias voltage VBIASAnd the voltage difference is equal to the common-mode direct-current level of the high-speed differential driving signal output by the current-mode logic driving module.
Compared with the prior art, the invention has the following advantages:
the invention provides a light emitter, comprising: the circuit comprises a current mode logic driving module, a modulator and a termination module; connecting the current mode logic driving module with the input end of the modulator in a direct coupling mode, and outputting a high-speed differential driving signal; connecting the output end of the modulator with the input end of the termination module in a direct coupling mode; the modulator is used for modulating the optical signal of the high-speed differential driving signal according to the received high-speed differential driving signal to obtain a modulated optical signal and outputting the modulated optical signal; the termination module is used for performing far-end impedance matching on the received high-speed differential driving signal. On one hand, the direct coupling mode (direct coupling driving mode) is adopted, so that additional components such as a direct current bias module or a direct current voltage isolator are not required, the hardware cost required by the light emitter is saved, and the area of a light emitter circuit is reduced.
On the other hand, the bias voltage VBIASAnd the voltage difference between the common-mode direct current level of the high-speed differential driving signal output by the current-mode logic driving module and the common-mode direct current level of the high-speed differential driving signal output by the current-mode logic driving module is the bias voltage of the first optical phase shifter and the second optical phase shifter. By adjusting the bias voltage VBIASIs capable of adjusting the bias voltage of the first and second optical phase shiftersSize. In particular by applying said bias voltage VBIASAnd the working voltage VCC of the current mode logic driving module is in short circuit, and the aim of adjusting the bias voltage of the first optical phase shifter and the bias voltage of the second optical phase shifter can be realized only by adjusting the common-mode direct-current level of the high-speed differential driving signal output by the current mode logic driving module. Therefore, the invention does not need to provide additional components such as a direct current bias module or a direct current voltage isolator (DC Block) and the like which are needed for adjusting the bias voltage of the first optical phase shifter and the bias voltage of the second optical phase shifter, and achieves the aims of saving the hardware cost needed by the optical transmitter and reducing the circuit area of the optical transmitter.
On the other hand, the other ends of the two terminating resistors in the terminating module are connected with the terminating capacitor after being connected with each other (forming a node X), so that on one hand, the direct current component on a signal line is eliminated, on the other hand, the common-mode direct current level of the high-speed differential driving signal output by the current mode logic driving module is also reduced, the reverse bias voltage of the modulator is improved, and the modulation effect of the modulator is further improved. And compared with the termination module provided in the prior art, since the common-mode voltage of the node in the termination module in the prior art is determined by the amplifier in the current-mode logic driving module, the common-mode voltage of the node can be represented as VCC-0.5IbRLTherefore, although the termination module in the prior art can achieve the purpose of reducing the common mode voltage of the node, the termination module also has the problems that the common mode voltage is easy to drift and is easily influenced by noise. Therefore, in order to solve the above problem, in the termination module provided in the present invention, since the first termination resistor and the second termination resistor are connected to the termination capacitor respectively and then connected to the power supply, the termination module can still isolate the dc current (so that no dc current path flows through the transmission line electrode of the traveling wave mach-zehnder modulator, thereby achieving the purpose of reducing the dc power consumption), stabilize the common mode voltage of the node X, and to some extent, achieve the common mode impedance of the high-speed differential driving signalAnd (6) matching. For the termination module, the common-mode voltage of the node X can be obviously stabilized by adding the termination capacitor, so that the reflection of the high-speed differential driving signal at the far end is inhibited, the high-speed differential driving signal is not easily influenced by noise, and the transmission quality of the high-speed differential driving signal is improved. That is, according to the present invention, by using a design scheme in which the high-speed differential driving signal output by the modulator is input to the impedance matching resistor (termination resistor) in the termination module and is connected to the power supply via the matching capacitor (termination capacitor), on the basis of achieving the differential-mode impedance matching of the far-end signal (performing the differential-mode impedance matching on the high-speed differential driving signal), the disadvantage that the dc component cannot be eliminated in the conventional design scheme in which the power supply is directly connected in series with the resistor is eliminated, the output common-mode voltage of the current-mode logic driving module is reduced, the reverse bias of the modulator is increased, and the modulation effect of the modulator is improved; besides, common-mode impedance matching of the far-end signals (common-mode impedance matching of the high-speed differential driving signals) is achieved through the matching capacitors, the voltage of a static working point of the high-speed differential driving signal is stabilized, and common-mode noise is eliminated. In conclusion, the invention has the advantages of saving hardware cost, reducing direct current power consumption, increasing the stability of device operation, prolonging the service life, reducing the complexity of circuit design and being beneficial to the integrated design of high-density multi-channel.
Drawings
Fig. 1 is a schematic diagram of a simple structure of an optical transmitter using AC coupling in the prior art;
fig. 2 is a schematic diagram of a simple structure of a prior art optical transmitter using a direct coupling method;
fig. 3 is a schematic diagram of a main structure of a light emitter according to an embodiment of the present invention;
fig. 4 is a graph illustrating jitter amplitude of node X in an optical transmitter according to an embodiment of the present invention as a function of the size of the termination capacitor C;
fig. 5 is a transient simulation waveform of a node X under the condition of no termination of capacitors in an optical transmitter according to an embodiment of the present invention;
fig. 6 is a transient simulation waveform of a node X in a case where a 50pF termination capacitor is connected to an optical transmitter according to an embodiment of the present invention.
Detailed Description
As described in the background art, the high dc power consumption, high circuit complexity, and increased area occupied by the circuit of the optical transmitter in the prior art are not favorable for the integrated design of high-density multi-channel. It is found that, as shown in fig. 1, the optical transmitter using AC coupling includes: the current mode logic driving module 11 is connected with the mach-zehnder modulator 13 through the direct current bias module 12, that is, the current mode logic driving module 11 is connected with the mach-zehnder modulator in an AC coupling mode, the mach-zehnder modulator 13 is connected with the termination module 14, and the current mode logic driving module 11 is used for providing a high-speed differential driving signal; the dc bias module 12 is configured to provide a bias voltage to the mach-zehnder modulator 13; the mach-zehnder modulator 13 is configured to modulate an optical signal input by an external light source according to the high-speed differential driving signal to obtain a modulated optical signal, and output the modulated optical signal; the termination module 14 is used for impedance matching of the high-speed differential drive signal output by the mach-zehnder modulator 13, and the termination module 14 needs to be provided because the transmission line electrode of the mach-zehnder modulator 13 is generally long. The mach-zehnder modulator 13 may be a traveling wave mach-zehnder modulator. The AC coupling mode may independently adjust the bias voltage of the traveling wave mach-zehnder modulator 13, and may prevent the working bias states of the current mode logic driving module 11 and the traveling wave mach-zehnder modulator 13 from interfering with each other. However, since the capacitance of the inductor of the dc bias module 12 is large, additional components are usually required, which occupies a large area of the circuit structure design of the light emitter, and is not favorable for the circuit structure design of the high-density multi-channel optoelectronic integration.
For the optical transmitter using direct coupling, as shown in fig. 2, it mainly includes an open-drain (open-drain) driver 21 and a traveling wave mach-zehnder modulator 22And a far-end load 23, wherein the structure combines a far-end termination module (such as termination module 14 shown in fig. 1) and a load resistor into a single unit to form the far-end load 23. The design of the light emitter is that the open-drain driver has no termination resistor (two resistors R of the current-mode logic driving module 11 shown in FIG. 1)L) The traveling wave Mach-Zehnder modulator has the advantages that strong optical signal reflection exists, the integrity of optical signal transmission is influenced, meanwhile, large direct current exists on a transmission line electrode of the traveling wave Mach-Zehnder modulator, direct current power consumption is increased, accordingly, heating of a device is caused, the operation stability of the device is reduced, and the service life of the device is prolonged.
Based on the above research, the present invention provides an optical transmitter, which mainly includes: a current mode logic driving module (current mode logic driver), a modulator and a termination module; connecting the current mode logic driving module with the input end of the modulator in a direct coupling mode, and outputting a high-speed differential driving signal; connecting the output end of the modulator with the input end of the termination module in a direct coupling mode; the modulator is used for modulating the optical signal of the high-speed differential driving signal according to the received high-speed differential driving signal to obtain a modulated optical signal and outputting the modulated optical signal; the termination module is used for carrying out impedance matching on the received high-speed differential driving signal.
According to the invention, a direct coupling mode (a direct coupling driving mode) is adopted, and additional components such as a direct current bias module or a direct current voltage isolator (DC Block) are not required to be arranged, so that the hardware cost required by the light emitter is saved, and the area occupied by the light emitter is reduced.
In addition, for the adjustment of the bias voltage of the optical phase shifter in the modulator, the output direct current voltage of the current mode logic driving module and the bias voltage V connected to the optical phase shifter can be adjustedBIASThe voltage difference between them. Can bias the voltage VBIASThe bias voltage of the phase shifter can be adjusted only by adjusting the common-mode direct-current level of the high-speed differential driving signal output by the current mode logic driving module.
By inputting the high-speed differential driving signal output by the modulator into an impedance matching resistor (terminating resistor) in the terminating module and connecting the high-speed differential driving signal with a power supply through a matching capacitor (terminating capacitor), on the basis of realizing remote signal differential mode impedance matching (performing differential mode impedance matching on the high-speed differential driving signal), the defect that a direct current component cannot be eliminated in the conventional design scheme of directly connecting a resistor in series with a power supply is eliminated, the output common mode voltage of the current mode logic driving module is reduced, the reverse bias voltage of the modulator is improved, and the modulation effect of the modulator is further improved; besides, common-mode impedance matching of the far-end signals (common-mode impedance matching of the high-speed differential driving signals) is achieved through the matching capacitors, the voltage of a static working point of the high-speed differential driving signal is stabilized, and common-mode noise is eliminated. In summary, the invention solves the problems of high dc power consumption, high circuit complexity, increased area occupied by the light emitter circuit, and unfavorable for high-density multi-channel integrated design in the prior art.
A light emitter according to the present invention will be described in further detail with reference to the accompanying drawings and the following detailed description. The advantages and features of the present invention will become more apparent from the following description. To make the objects, features and advantages of the present invention comprehensible, reference is made to the accompanying drawings. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the implementation conditions of the present invention, so that the present invention has no technical significance, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
As shown in fig. 3, the present embodiment provides an optical transmitter including: a current mode logic driving module 101, a modulator 102 and a termination module 103; connecting the current mode logic driving module 101 with an input end of the modulator 102 in a direct coupling manner, wherein the current mode logic driving module 101 is used for generating and outputting a high-speed differential driving signal; connecting the output end of the modulator 102 with the input end of the termination module 103 in a direct coupling manner; the modulator 102 is configured to modulate an optical signal thereof according to the received high-speed differential driving signal to obtain a modulated optical signal and output the modulated optical signal; the termination module 103 is configured to perform impedance matching on the received high-speed differential driving signal. In this embodiment, the input of the modulator 102 may be defined as the near end, and the output of the modulator 102 may be defined as the far end. The modulator 102 is an optical modulator, and may be a traveling wave mach-zehnder modulator.
Further, the current-mode logic driving module 101 further includes: load resistor 1012
Source-common-gate structure 1011, input pair tube 1010 and tail current source Ib；
A first end of the load resistor 1012 is connected to the operating voltage VCC of the current mode logic driving module 101, and a second end thereof is connected to the drain of the cascode structure 1011;
the source of the cascode structure 1011 is connected to the collector of the input pair transistor 1010;
launch of the input pair of tubes 1010Stage through the tail current source IbGrounding;
the load resistor 1012 is configured to perform near-end impedance matching on the high-speed differential driving signal (i.e., perform impedance matching on the high-speed differential driving signal that has not yet passed through the output terminal of the current mode logic driving module 101) and convert the current signal generated by the input pair transistor 1010 into a high-speed differential voltage signal;
the cascode structure 1011 is used to isolate the collector output terminal of the input pair transistor 1010 from the output terminal of the current mode logic driving module 101, so as to reduce the influence of the miller effect;
the input pair transistors 1010 are used for converting the high-speed differential voltage signal into a high-speed differential current signal (i.e., a high-speed differential driving signal);
and the tail current source Ib is used for setting the output swing of the high-speed differential driving signal.
Optionally, the load resistor 1012 comprises a first load resistor RL1 and a second load resistor RL2 which are connected in parallel; the first ends of the first load resistor RL1 and the second load resistor RL2 are respectively connected to the working voltage VCC of the current mode logic driving module; second ends of the first load resistor RL1 and the second load resistor RL2 are respectively connected with the drain of the cascode structure. The cascode structure 1011 includes two first field effect transistors M with their gates connected to each otherc1And a second field effect transistor Mc2(ii) a The input pair transistor comprises a first bipolar junction transistor (or CMOS device) Q1And a second bipolar junction transistor (or CMOS device) Q2(ii) a Wherein the first bipolar junction transistor Q1The base of the transistor is inputted with a positive voltage signal VinpSaid second bipolar junction transistor Q2The base of the voltage signal V is input with negative polarityinn。
Optionally, the modulator 102 includes: a first optical phase shifter 1020, a second optical phase shifter 1021, an input optical splitter 1024A, and an output optical combiner 1024B.
The first optical phase shifter 1020 includes a first transmission line electrode 1120 and a second transmission line electrode 1121.
The second optical phase shifter 1021 includes a third transfer line electrode 1221 and a fourth transfer line electrode 1222.
One end of the second transmission line electrode 1121 and the second load resistor RL2And the other end of the second terminal is connected to the input terminal of the termination module 103.
One end of the fourth transmission line electrode 1222 is the first load resistor RL1And the other end of the second terminal is connected to the input terminal of the termination module 103.
The first transmission line electrode 1120 and the third transmission line electrode 1221 are connected in parallel and switched in a bias voltage VBIAS(ii) a In this embodiment, the first transmission line electrode 1120 and the third transmission line electrode 1221 are both RF ground signal transmission line electrodes.
The bias voltage VBIASThe voltage difference with the common mode dc level of the high-speed differential driving signal output by the current mode logic driving module 101 is the bias voltage of the first and second optical phase shifters. By adjusting the bias voltage VBIASThe magnitude of the bias voltage of the first and second optical phase shifters can be adjusted. Therefore, the invention does not need to arrange additional components such as a direct current bias module or a direct current voltage isolator (DC Block), and achieves the aims of saving the hardware cost required by the light emitter and reducing the occupied area of the light emitter.
Preferably, at least one PN junction optical waveguide 1025 is arranged between the first transmission line electrode 1120 and the second transmission line electrode 1121 at intervals; at least one PN junction optical waveguide 1025 is arranged between the third transmission line electrode 1221 and the fourth transmission line electrode 1222 at intervals, and each PN junction optical waveguide 1025 is used for modulating digital information carried in a high-speed differential driving signal on the fourth transmission line electrode 1222 and the second transmission line electrode 1121 electrode onto an optical signal respectively.
The input optical splitter 1024A is configured to divide an optical signal into two branch optical signals and output the two branch optical signals; the first optical phase shifter 1020 and the second optical phase shifter 1021 are configured to modulate the two branch optical signals according to the high-speed differential driving signal, and correspondingly load digital information carried by the high-speed differential driving signal into the two branch optical signals to obtain and output two modulated branch optical signals; the output optical combiner 1024B is configured to combine the received two paths of modulated branch optical signals into one path of modulated optical signal and output the modulated branch optical signal, where the modulated branch optical signal is an optical signal sent by the optical transmitter. In this embodiment, the input optical splitter 1024A is specifically a half optical splitter, and is configured to divide the optical signal into 1: 1 into two branch optical signals; the output optical combiner 1024B is specifically a two-in-one optical combiner, and is configured to combine the two paths of modulated branch optical signals to obtain one path of modulated optical signal.
Further, the modulator 102 further includes: input optical interface 1023A and output optical interface 1023B; the input optical interface 1023A is connected to the input optical splitter 1024A, and is used for inputting the optical signal to the input optical splitter; the output optical interface 1023B is connected to the output optical combiner 1024B, and is configured to output one path of the modulated optical signal. In this embodiment, the input optical interface 1023A is further connected to a light source for providing the optical signal.
Preferably, the termination module 103 comprises: first terminating resistor R1And a second terminating resistor R2And a termination capacitor CT(ii) a The first termination resistor R1And a second terminating resistor R2Are connected in parallel, the first termination resistor R1Is connected to the fourth transmission line electrode, and has a second end connected to the terminating capacitor CTIs connected with the first end of the first connecting pipe; the second termination resistor R2Is connected to the second transmission line electrode, and has a second end connected to the terminating capacitor CTIs connected with the first end of the first connecting pipe; the termination capacitor CTThe second end of the second terminal is connected to the working voltage VCC of the termination module. The first termination resistor R1And a second terminating resistor R2For differential mode impedance matching of high speed drive signal, the first termination resistor R1And a second terminating resistorR2Respectively, is consistent with the characteristic impedance of the first optical phase shifter 1020 and the second optical phase shifter 1021.
The load resistor 1012 of the current mode logic driving module 101 of the present invention plays a role of impedance matching of the high-speed differential driving signal at the near end, and the resistance value of the load resistor 1012 is consistent with the characteristic impedance of the transmission line electrodes of the first and second optical phase shifters of the modulator, and preferably, may be 30 Ω (the first load resistor R is equal to R)L1Has a resistance value of 30 omega, and a second load resistance RL2The resistance value of (2) is 30 Ω). The first termination resistor R1And a second terminating resistor R2For matching the differential mode impedance of the high-speed differential drive signal at the far end, the first termination resistor R1And a second terminating resistor R2Respectively, of the modulator, preferably both 30 omega (first termination resistance R), corresponds to the characteristic impedance of the transmission line electrodes of the first and second optical phase shifters of said modulator, respectively1Has a resistance value of 30 omega and a second terminating resistance R2The resistance value of (2) is 30 Ω). Unlike other schemes that directly connect the other end of the remote termination resistor to the power source (such as the termination module mentioned in the background section), in the embodiment of the present invention, the other ends of the two termination resistors are connected to each other (forming node X) and then connected to the termination capacitor CTAnd on one hand, the direct current component on the signal line is eliminated, on the other hand, the common-mode direct current level of the high-speed differential driving signal output by the current mode logic driving module 101 is also reduced, the reverse bias voltage of the modulator 102 is improved, and the modulation effect of the modulator is further improved.
In addition, since the common mode voltage of the node X is determined by an amplifier (not shown in the figure) in the current mode logic driving module 101, the common mode voltage of the node X in this embodiment can be represented as VCC-0.5IbRL, and although the common mode voltage of the node X is reduced, there is a problem that the common mode voltage is easy to drift and is easily affected by noise. Therefore, in order to solve the above problem, the termination module 103 provided in the present embodiment has the first termination resistor R2 and the second termination resistor R1 and the termination capacitor C respectivelyTAfter connectionAnd the high-speed differential driving signal is connected with a power supply VCC, on one hand, the isolation of direct current can still be realized, on the other hand, the purpose of stabilizing the common-mode voltage of the node X is realized, and the common-mode impedance matching of the high-speed differential driving signal is realized to a certain extent. In this embodiment, for termination capacitors with different sizes under the condition of a transmission rate of 25Gbps NRZ digital signals, the variation of the jitter swing of the node X is as shown in fig. 4, 5, and 6, it can be seen that the common-mode voltage of the node X can be obviously stabilized by adding the termination capacitor, and further the reflection of the high-speed differential driving signal at the far end is suppressed, so that the high-speed differential driving signal is not easily affected by noise, and the quality of the high-speed differential driving signal is improved.
In the light emitter in this embodiment, a circuit connection design of a traveling wave mach-zehnder modulator and a current mode logic driving module (current mode logic driver) that are directly coupled is adopted, and by means of a design scheme of connection with the circuit, a large inductance and capacitance device required by a direct current BIAS (BIAS TEE) module or a direct current voltage isolator (DC Block) in the conventional circuit design can be omitted, so that the area of the light emitter is saved. The termination module not only meets the matching of differential mode termination and common mode termination, but also does not have AC coupling to a power supply VCC through a capacitor, so that no direct current path flows through a transmission line electrode of the traveling wave Mach-Zehnder modulator, thereby realizing the purpose of reducing direct current power consumption.
In summary, the direct coupling mode (direct coupling driving mode) is adopted in the invention, and no additional component such as a direct current bias module or a direct current voltage isolator (DC Block) is required, so that the hardware cost required by the light emitter is saved, and the area occupied by the light emitter is reduced.
In addition, for the adjustment of the bias voltage of the optical phase shifter in the modulator, the output direct current voltage of the current mode logic driving module and the bias voltage V connected to the optical phase shifter can be adjustedBIASThe voltage difference between them. In particular, the bias voltage V can be adjustedBIASThe working voltage VCC of the current mode logic driving module is in short circuit, and the current mode logic is adjusted onlyThe purpose of adjusting the bias voltage of the first optical phase shifter and the bias voltage of the second optical phase shifter can be achieved by the common-mode direct-current level of the high-speed differential driving signal output by the driving module.
By inputting the high-speed differential driving signal output by the modulator into an impedance matching resistor (terminating resistor) in the terminating module and connecting the high-speed differential driving signal with a power supply through a matching capacitor (terminating capacitor), on the basis of realizing remote signal differential mode impedance matching (performing differential mode impedance matching on the high-speed differential driving signal), the defect that a direct current component cannot be eliminated in the conventional design scheme of directly connecting a resistor in series with a power supply is eliminated, the output common mode voltage of the current mode logic driving module is reduced, the reverse bias voltage of the modulator is improved, and the modulation effect of the modulator is further improved; besides, common-mode impedance matching of the far-end signals (common-mode impedance matching of the high-speed differential driving signals) is achieved through the matching capacitors, the voltage of a static working point of the high-speed differential driving signal is stabilized, and common-mode noise is eliminated. In summary, the invention solves the problems of high dc power consumption, high circuit complexity, increased area occupied by the light emitter circuit, and unfavorable for high-density multi-channel integrated design in the prior art.
The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (12)
1. An optical transmitter, comprising:
the circuit comprises a current mode logic driving module, a modulator and a termination module;
connecting the current mode logic driving module with the input end of the modulator in a direct coupling mode, wherein the current mode logic driving module is used for generating and outputting high-speed differential driveA signal; the current mode logic driving module comprises a load resistor, a cascode structure and an input pair transistor, wherein the load resistor comprises a first load resistor R connected in parallelL1And a second load resistor RL2(ii) a The first load resistor RL1And a second load resistor RL2The first ends of the current mode logic driving modules are respectively connected to the working voltage VCC of the current mode logic driving module; the first load resistor RL1And a second load resistor RL2Is connected to the drain of the cascode structure, respectively, and the first load resistor RL1And a second load resistor RL2The second ends of the first and second switches are respectively connected with the input end of the modulator; the source electrode of the cascode structure is connected with the collector electrode of the input geminate transistor; the load resistor is used for performing near-end impedance matching on the high-speed differential driving signal and converting a current signal generated by the input pair transistors into a high-speed differential voltage signal; the cascode structure is used for isolating the collector of the input pair transistor from the output end of the current mode logic driving module so as to reduce the influence of the Miller effect; the input pair transistors are used for converting the high-speed differential voltage signals into high-speed differential driving signals;
connecting the output end of the modulator with the input end of the termination module in a direct coupling mode; the modulator is used for modulating the optical signal of the high-speed differential driving signal according to the received high-speed differential driving signal to obtain a modulated optical signal and outputting the modulated optical signal;
the termination module is used for performing far-end impedance matching on the received high-speed differential driving signal; the termination module includes: first terminating resistor R1And a second terminating resistor R2And a termination capacitor CT(ii) a The first termination resistor R1And a second terminating resistor R2Are connected in parallel, the first termination resistor R1And the first terminal and the second terminal resistor R2The first ends of the first and second switches are respectively connected with the output end of the modulator; the first termination resistor R1And the second terminal of (2) and the second termination resistor R2Respectively with said terminating capacitor CTIs connected with the first end of the first connecting pipe; the termination capacitorCTThe second end of the second terminal is connected to the working voltage VCC of the termination module; the first termination resistor R1And said second terminating resistor R2The circuit is used for carrying out far-end differential mode impedance matching on the high-speed driving signal; the termination capacitor is used for inhibiting the reflection of the high-speed differential driving signal at the far end.
2. The optical transmitter of claim 1, wherein the current-mode logic driver module further comprises: a tail current source;
the emitter of the input pair tube is grounded through the tail current source;
the tail current source is used for setting the output swing of the high-speed differential driving signal.
3. The optical transmitter of claim 2,
the cascode structure comprises a first field effect transistor M with interconnected gatesc1And a second field effect transistor Mc2；
The input pair transistors comprise a first bipolar junction transistor Q1And a second bipolar junction transistor Q2(ii) a Wherein the first bipolar junction transistor Q1The base of the transistor is inputted with a positive voltage signal VinpSaid second bipolar junction transistor Q2The base of the voltage signal V is input with negative polarityinn。
4. The optical transmitter of claim 3, wherein the modulator is a traveling wave Mach-Zehnder modulator.
5. The optical transmitter of claim 4, wherein the modulator comprises: the optical phase shifter comprises a first optical phase shifter, a second optical phase shifter, an input optical splitter and an output optical combiner;
the first optical phase shifter comprises a first transmission line electrode and a second transmission line electrode;
the second optical phase shifter comprises a third transmission line electrode and a fourth transmission line electrode;
one end of the second transmission line electrode and the second load resistor RL2The other end of the second end connection is connected with the input end of the termination module;
one end of the fourth transmission line electrode is the first load resistor RL1The other end of the second end connection is connected with the input end of the termination module;
the first transmission line electrode and the third transmission line electrode are connected in parallel and switched in a bias voltage VBIAS；
The input optical splitter is used for equally dividing the optical signal into two branches of optical signals and outputting the optical signals;
the first optical phase shifter and the second optical phase shifter are used for modulating the two branch optical signals according to the high-speed differential driving signal respectively, and correspondingly loading digital information carried by the high-speed differential driving signal into the two branch optical signals to obtain and output two modulated branch optical signals;
and the output optical combiner is used for combining the received two paths of modulated branch optical signals into one path of modulated optical signal and outputting the modulated optical signal.
6. The optical transmitter of claim 5, wherein the modulator further comprises: an input optical interface and an output optical interface;
the input optical interface is connected with the input optical splitter and is used for inputting the optical signal to the input optical splitter;
the output optical interface is connected with the output optical combiner and used for outputting one path of the modulated optical signal.
7. The optical transmitter of claim 6 wherein the input splitter is a half splitter for transmitting the optical signal in a 1: 1 into two branch optical signals;
the output light combiner is a two-in-one light combiner, and is configured to combine the two paths of modulated branch optical signals to obtain one path of modulated optical signal.
8. The optical transmitter of claim 7,
at least one PN junction optical waveguide is arranged between the first transmission line electrode and the second transmission line electrode at intervals;
at least one PN junction optical waveguide is arranged between the third transmission line electrode and the fourth transmission line electrode at intervals.
9. The optical transmitter of claim 8,
the first termination resistor R of the termination module1Is connected with the fourth transmission line electrode;
the second terminating resistor R of the terminating module2Is connected to the second transmission line electrode.
10. The optical transmitter of claim 9, wherein the first termination resistor R1And a second terminating resistor R2Respectively, is consistent with the characteristic impedance of the first optical phase shifter and the second optical phase shifter.
11. The optical transmitter of claim 10, further comprising: applying the bias voltage VBIASAnd the bias voltage of the first optical phase shifter and the bias voltage of the second optical phase shifter are adjusted by adjusting the common-mode direct-current level of the high-speed differential driving signal output by the current mode logic driving module.
12. The optical transmitter of claim 11 wherein the bias voltages of the first and second optical phase shifters are the bias voltages VBIASAnd the voltage difference is equal to the common-mode direct-current level of the high-speed differential driving signal output by the current-mode logic driving module.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910591044.9A CN110224759B (en) | 2019-07-02 | 2019-07-02 | Light emitter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910591044.9A CN110224759B (en) | 2019-07-02 | 2019-07-02 | Light emitter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN110224759A CN110224759A (en) | 2019-09-10 |
| CN110224759B true CN110224759B (en) | 2021-03-26 |
Family
ID=67815564
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910591044.9A Active CN110224759B (en) | 2019-07-02 | 2019-07-02 | Light emitter |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110224759B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP7453585B2 (en) | 2020-07-29 | 2024-03-21 | 日本電信電話株式会社 | semiconductor optical modulator |
| CN112600623B (en) * | 2020-12-09 | 2022-04-05 | 武汉光谷信息光电子创新中心有限公司 | Differential drive modulator and control method thereof |
| CN113922886B (en) * | 2021-09-01 | 2022-12-13 | 烽火通信科技股份有限公司 | Chirp compensation method and driver for optical modulator |
| CN114063321B (en) * | 2022-01-06 | 2022-04-22 | 成都明夷电子科技有限公司 | Silicon photon push-pull microphone Jeda modulator with double differential electrodes |
| US20230229026A1 (en) * | 2022-01-14 | 2023-07-20 | Huawei Technologies Co., Ltd. | Method, apparatus and system for limited-range impedance tuning for silicon photonics devices |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8948608B1 (en) * | 2012-09-27 | 2015-02-03 | Inphi Corporation | Direct-coupled driver for mach-zehnder optical modulators |
| CN103532503A (en) * | 2013-09-18 | 2014-01-22 | 清华大学 | Power amplifier |
| JP6981041B2 (en) * | 2017-05-17 | 2021-12-15 | 富士通株式会社 | Drive circuit, optical transmission module and optical transmission device using this |
-
2019
- 2019-07-02 CN CN201910591044.9A patent/CN110224759B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN110224759A (en) | 2019-09-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110224759B (en) | Light emitter | |
| US11086188B2 (en) | Optical waveguide modulator | |
| US6836185B1 (en) | High-speed electro-optical modulator drivers and method | |
| US10048519B1 (en) | Mach-zehnder modulator driver | |
| CN103378845A (en) | Communication interface for galvanic isolation | |
| US8150270B2 (en) | Compact high-speed modulator driver method and apparatus | |
| CN109638642B (en) | High-speed large-current laser driving circuit and current modulation method thereof | |
| US9825709B2 (en) | Traveling wave amplifier for driving optical modulator | |
| JP6701115B2 (en) | Optical transmitter | |
| US20180356654A1 (en) | Drive circuit | |
| CN102545884A (en) | Voltage type data transmitter with high-efficiency pre-emphasis balance | |
| US7816987B2 (en) | Driver circuit and driver IC | |
| US20090243718A1 (en) | High-speed modulator driver circuit with enhanced drive capability | |
| US20200241331A1 (en) | Driving circuit for optical modulator | |
| US7869388B2 (en) | Class-B transmitter and replica transmitter for gigabit ethernet applications | |
| CN111162740B (en) | Radio frequency general communication interface difference and common mode decoupling device | |
| CN113078954A (en) | Driving circuit based on phase shift pre-emphasis | |
| JP5234776B2 (en) | Laser drive circuit | |
| CN105027430A (en) | Emphasis circuit | |
| CN114200991A (en) | Distributed current drive circuit | |
| US20160036422A1 (en) | Cross-point shifting techniques | |
| US6619866B1 (en) | Dynamic range extended for optical transmitters | |
| US10564450B1 (en) | Electrical amplifier and electro-optical device comprising an electrical amplifier | |
| JP2014163971A (en) | Optical modulator, optical transmitter, optical transmission/reception system and optical modulator control method | |
| US20140218073A1 (en) | Driver for high speed electrical-optical modulator interface |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |