CN115225156A - Feedback circuit for optical transmitter and optical transmitter - Google Patents
Feedback circuit for optical transmitter and optical transmitter Download PDFInfo
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- CN115225156A CN115225156A CN202210859371.XA CN202210859371A CN115225156A CN 115225156 A CN115225156 A CN 115225156A CN 202210859371 A CN202210859371 A CN 202210859371A CN 115225156 A CN115225156 A CN 115225156A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- 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
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- 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
Abstract
A feedback circuit for an optical transmitter and an optical transmitter are provided. The light emitter includes: a driver for amplifying an input signal based on a gain control signal to generate a driving signal; and a modulator for generating an output optical signal by modulating the drive signal onto an input optical signal, the feedback circuit comprising: the optical splitter is used for splitting an optical signal with a certain proportion from the output optical signal to serve as a bypass optical signal; and a control circuit for generating the gain control signal based on a first comparison result between a peak value of the driving signal and a first reference value and a second comparison result between a peak value of the bypass optical signal and a second reference value.
Description
Technical Field
The present disclosure relates to a feedback circuit for an optical transmitter and an optical transmitter.
Background
Long-distance high-quality optical transmission requires that the optical transmitter be capable of providing an optical signal with a sufficiently high amplitude-to-Extinction Ratio (ER), and therefore requires that the driver be capable of providing a sufficiently large output swing to drive the optical modulator. However, increasing the swing of the driver inevitably consumes higher power consumption. Therefore, to achieve the best performance of the optical interconnection system, the output swing of the driver needs to be adjusted according to the actual application environment and system requirements.
If the adjustment of the output swing of the driver is realized by the joint debugging of the optical transmitter and the optical receiver, a long feedback adjustment loop is needed, and a complex system is needed to realize the adjustment. Thus, a more efficient feedback circuit for an optical transmitter is desired.
Disclosure of Invention
According to an aspect of the present disclosure, there is provided a feedback circuit for an optical transmitter, the optical transmitter including: a driver for amplifying an input signal based on a gain control signal to generate a drive signal; and a modulator for generating an output optical signal by modulating the drive signal onto an input optical signal, the feedback circuit comprising: the optical splitter is used for splitting an optical signal with a certain proportion from the output optical signal to serve as a bypass optical signal; and a control circuit for generating the gain control signal based on a first comparison result between a peak value of the driving signal and a first reference value and a second comparison result between a peak value of the bypass optical signal and a second reference value.
According to another aspect of the present disclosure, there is provided a light emitter including: a driver for amplifying an input signal based on a gain control signal to generate a driving signal; a modulator for generating an output optical signal by modulating the driving signal onto an input optical signal; and a feedback circuit according to embodiments of the present disclosure.
These and other aspects of the disclosure will be apparent from and elucidated with reference to the embodiments described hereinafter.
Drawings
Further details, features and advantages of the disclosure are disclosed in the following description of exemplary embodiments, taken in conjunction with the accompanying drawings, in which:
fig. 1 is a schematic circuit diagram of an optical transmitter and an optical receiver in the related art;
fig. 2 is a schematic block diagram illustrating an optical transmitter and a feedback circuit according to an exemplary embodiment of the present disclosure;
fig. 3 is a schematic block diagram illustrating an optical transmitter and a feedback circuit according to a variation of the exemplary embodiment of the present disclosure;
fig. 4 is a schematic block diagram illustrating an optical transmitter and a feedback circuit according to another variation of an exemplary embodiment of the present disclosure.
Detailed Description
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure.
Spatially relative terms such as "below …", "below …", "lower", "below …", "above …", "upper", and the like may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that these spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" or "under" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "below …" and "below …" may encompass both orientations above … and below …. Terms such as "before …" or "before …" and "after …" or "next to" may similarly be used, for example, to indicate the order in which light passes through the elements. The devices may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items, and the phrase "at least one of a and B" includes a alone, B alone, and both a and B.
It will be understood that when an element or layer is referred to as being "on," "connected to," "coupled to" or "adjacent to" another element or layer, it can be directly on, connected to, coupled to or adjacent to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly connected to," "directly coupled to," or "directly adjacent to" another element or layer, there are no intervening elements or layers present. However, neither "on …" nor "directly on …" should be construed as requiring one layer to completely cover an underlying layer in any case.
Embodiments of the present disclosure are described herein with reference to schematic illustrations (and intermediate structures) of idealized embodiments of the present disclosure. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the present disclosure should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the present disclosure.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and/or the present specification and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Long-distance high-quality optical transmission requires that the optical transmitter be capable of providing an optical signal with a sufficiently high amplitude-to-Extinction Ratio (ER), and therefore requires that the driver be capable of providing a sufficiently large output swing to drive the optical modulator. However, increasing the swing of the driver inevitably consumes higher power consumption. Therefore, to achieve the best performance of the optical interconnection system, the output swing of the driver needs to be adjusted according to the actual application environment and system requirements.
According to the related art, adjustment of the driver output swing is often achieved by joint debugging of the optical transmitter and the optical receiver. Fig. 1 is a schematic circuit diagram of a system 100 composed of an optical transmitter 110 and an optical receiver 120 in the related art. As shown in fig. 1, optical transmitter 110 may include a driver 111, a modulator 112, and an analog-to-digital converter (DAC) 113. The optical receiver 120 may include an optical-to-electrical converter 121, an analog-to-digital converter (ADC) 122, and a Digital Signal Processor (DSP) 123. The photoelectric converter 121 may include a Photodetector (PD) and a transimpedance amplifier (TIA).
As shown in FIG. 1, at the light emitter 110 side, the driver 111 amplifiesInput signal D in Generating a driving signal D out To drive the modulator 112. The modulator 112 may be a Mach-Zehnder (MZ) modulator. Modulator 112 will drive signal D out Modulating to an optical input signal OPT in Thereafter outputting the modulated optical signal OPT out . Optical signal OPT out The optical signal is transmitted through the optical fiber 130 to the optical receiver 120, and then converted into an electrical signal through the optical-to-electrical converter 121, for example, through a photodetector and a transimpedance amplifier. The analog electrical signal received at the optical receiver 120 is converted into a digital signal by the ADC 122, and then calculated by the Digital Signal Processor (DSP) 123 to obtain an optical signal-to-noise ratio (OSNR). To achieve driver output swing adjustment, the calculated OSNR is compared to the system requirements. And if the OSNR of the optical receiving end is lower than the target requirement, regulating and controlling the output swing amplitude control DAC of the transmitting end to determine to increase the output swing amplitude of the driver so as to realize the optimal OSNR.
However, according to the related art, joint debugging of the transmitter and the receiver is required, the feedback regulation loop is long, the required system implementation is complex, and the effect of timely response is difficult to achieve. Furthermore, such a scheme only considers adjusting the output swing of the driver to reach the best point of performance.
Exemplary embodiments of the present disclosure will be described in detail below, which may be used to advantage for a number of reasons, such as to mitigate or alleviate these undesirable side effects.
Fig. 2 is a schematic circuit diagram illustrating a system 200 of optical transmitters and feedback circuits according to an exemplary embodiment of the present disclosure.
Referring to fig. 2, the optical transmitter may include a driver 210 and a modulator 220. The driver 210 may be used to couple the input signal D based on the gain control signal in Amplifying to generate a drive signal D out . The modulator 220 may be arranged to modulate the drive signal D by applying a pulse width modulation signal out Modulation to an input optical signal OPT in Generating an output optical signal OPT out . In one example, the modulator may be an MZ modulator. The modulator may also be other modulators as will be appreciated by those skilled in the artA modulator, a modulation circuit, or an optical output circuit that generates a modulated optical signal, and the disclosure is not limited thereto.
It will be appreciated that the optical transmitter and feedback circuit shown herein may be referred to collectively as a feedback regulation system, and that the feedback circuit may be produced, arranged, and separated from the optical transmitter. In addition, although it is stated above that the optical transmitter may include the driver 210 and the modulator 220, the whole integration of the driver, the modulator, and the feedback circuit may be referred to as an optical transmitter. It is to be understood that the present disclosure is not limited in this respect.
With continued reference to fig. 2, the feedback circuit may include an optical splitter 230 and a control circuit 240. The optical splitter 230 may be configured to split a proportion of the optical signal from the output optical signal as a bypass optical signal. The control circuit 240 may be configured to generate the gain control signal based on a first comparison result between a peak value of the drive signal and a first reference value and a second comparison result between a peak value of the bypass optical signal and a second reference value. For example, the gain control signal may be a gain control voltage signal V SW . Alternatively, as can be appreciated by those skilled in the art, the gain control signal may be other signals suitable for controlling the gain of the driver 210, including but not limited to analog signals (e.g., current signals), digital signals, and the like.
It will be appreciated by those skilled in the art that the control circuit 240 may be implemented in any known or future technology. The control circuit may be implemented in a logic circuit, an analog circuit, or a combination thereof, and the present disclosure is not limited thereto. Examples of control circuitry 240 include, but are not limited to, a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof.
According to one or more embodiments of the present disclosure, a feedback circuit, a circuit system and a control method integrated at a transmitting end and capable of automatically adjusting output swing of a driver are provided. Specifically, according to the driver output swing feedback adjusting circuit or method disclosed by the present disclosure, the gain of the driver can be feedback-controlled by detecting the output swing of the driver and the amplitude of the output optical signal of the MZ modulator, so as to achieve the purpose of adjusting the output swing of the driver.
The first reference value may be based on a transistor withstand voltage value of the driver. For example, according to some embodiments, the first reference value may be positively correlated with a transistor withstand voltage value of the driver. According to some alternative embodiments, in the case where the first reference value is a voltage value, the first reference value may be equal to or slightly higher than a transistor withstand voltage value of the driver. According to other embodiments, the first reference value may depend at least in part on the withstand voltage or other withstand values of other elements of the drive and may optionally vary depending on the type, operating duration, life cycle of the drive or elements thereof.
The second reference value may be based on an optical output signal amplitude requirement of an optical link in which the optical transmitter is located. For example, according to some embodiments, the second reference value is positively correlated to a minimum optical output signal amplitude required by an optical link in which the optical transmitter is located. As a specific, non-limiting example, where the second reference value is an optical signal amplitude, the second reference value may be approximately equal to the minimum optical output signal amplitude. As another specific, non-limiting example, where the second reference value is a voltage value, it may be positively correlated to the minimum optical output signal amplitude. In other embodiments, the second reference value may also be based on an average optical output signal amplitude, a maximum optical output signal amplitude, an optical output signal amplitude range, etc. required by the optical link, and the disclosure is not limited thereto.
In a scenario where a first reference value is based on a transistor withstand voltage value of the driver and a second reference value is based on an optical output signal amplitude requirement of an optical link in which the optical transmitter is located, according to some embodiments, the control circuit is configured to adjust the gain control signal such that a peak value of the drive signal is lower (or, not higher) than the first reference value and a peak value of the bypass optical signal is higher than or equal to (or, higher) than the second reference value. According to the embodiment, the output swing of the driver can be adjusted on the premise of ensuring the voltage endurance reliability of the driver transistor, so that the requirements of long-distance transmission and long-term working reliability of the optical transmitter can be met.
According to other embodiments, the control circuit may assume different logic. For example, where the second reference value indicates a maximum optical output signal amplitude required by the optical link, the logic of the control circuit may be such that the peak value of the bypass optical signal is lower than (or, lower than or equal to) the second reference value, and the disclosure is not limited thereto.
A schematic block diagram of an optical transmitter and feedback circuit of a variation of the exemplary embodiment of the present disclosure is described below with respect to fig. 3. As shown in fig. 3, the feedback regulation system may include a driver, a modulator, and a driver swing feedback circuit. As previously described, the driver swing feedback circuit and the optical transmitter may be considered as separate circuits, respectively, or the whole integration of the driver, the modulator and the feedback circuit may be referred to as an optical transmitter, and the present disclosure is not limited thereto.
Next, for convenience of description, the light emitter part and the feedback circuit part will be separately described, but it will be understood that this will not constitute a limitation of the present disclosure. In such an example, the feedback circuit may include driver 310 and modulator 320, and the feedback circuit portion may include splitter 330 and control circuit 340. The driver 310 will input the signal D in Amplifying output drive signal D out For driving the modulator 320. The output swing of driver 310 is represented by signal V SW Control, change V SW The output swing of driver 310 may be varied. The modulator 320 is used for receiving an input optical signal OPT in And will drive signal D out Modulation to an input optical signal OPT in And then generates an output optical signal OPT out . The feedback circuit is used for detecting the driving signal D out And MZ modulator outputs an optical signal OPT out Amplitude of (V), output driver swing control voltage V SW And further adjust the driving signal D out The swing of (c).
The same reference numerals as in fig. 2 denote similar elements, and a repetitive description of the structure or function thereof will be omitted herein.
As shown in fig. 3, according to such an embodiment, the control circuit 340 may include a first detection circuit 341, a second detection circuit 342, a first comparator 343, a second comparator 344, and a feedback controller 345. The first detection circuit 341 may be configured to detect a peak value of the driving signal. A second detection circuit 342 may be used to detect the peak of the bypass optical signal. The first comparator 343 may be configured to compare a peak value of the driving signal with the first reference value and output a first output voltage indicating the first comparison result. A second comparator 344 may be used to compare the peak value of the bypass optical signal with the second reference value and output a second output voltage indicative of the second comparison result. The feedback controller 345 may be configured to generate the gain control signal (e.g., gain control voltage signal V) based on the first output voltage and the second output voltage SW )。
According to some embodiments, the first detection circuit 341 may include a peak detector, which may be referred to herein as a first peak detector. The first peak detector can detect the driver output signal D out To output a corresponding peak voltage V PK1 . In such embodiments, the first comparator 343 may also be referred to as a first reference voltage comparator, and the present disclosure is not limited thereto. In such an embodiment, the first comparator 343 may compare V PK1 With a preset or received reference voltage V REF1 And comparing and outputting a comparison result. Reference voltage V REF1 The reference signal (or other form of reference signal) may be predetermined (e.g., pre-stored), may be dynamically generated (e.g., generated by the first comparator) or dynamically received (e.g., generated by other circuit portions or even by other circuits or devices), for example, according to a trigger condition or periodically, and the disclosure is not limited thereto. As an example, the control circuit 340 or the feedback controller 345 may be configured to adjust the first reference voltage V of the first comparator 343 according to the voltage withstanding protection requirement of the output tube of the driver REF1 Is arranged asDrive signal D out The magnitude of the limit.
In other embodiments, the first detection circuit 341 may also include other detection circuits known to those skilled in the art capable of detecting the magnitude or amplitude of the driving signal, and may take various forms (e.g., an optical signal, a current signal, a digital signal, etc.) to output the peak value of the driving signal, and the disclosure is not limited thereto.
According to some embodiments, the second detection circuit 342 may include a photoelectric converter (O/E) 3421 and a second peak detector 3422. The photoelectric converter can convert the output optical signal of the modulator into an electric signal V in a certain proportion MON . In such an embodiment, the optical-to-electrical converter 3421 may be used to convert the bypass optical signal to a voltage signal V MON . A second peak detector 3422 may be used to detect the voltage signal V MON Peak value of (V) PK2 As the peak value of the bypass optical signal, and the peak value V of the voltage signal PK2 Output to the second comparator 344 for comparison.
It will be appreciated that in such embodiments, the second comparator 344 may also be referred to as a second reference voltage comparator. In such embodiments, the second comparator 344 may compare V PK2 With a preset or received reference voltage V REF2 And comparing and outputting a comparison result. Reference voltage V REF1 The (or other form of reference signal) may be predetermined (e.g., pre-stored), may be dynamically generated (e.g., by the second comparator) or dynamically received (e.g., by other circuit portions or even by other circuits or devices), e.g., according to a trigger condition or periodically, and the disclosure is not limited thereto. For example, in other embodiments, the second detection circuit may output a peak value of the optical signal in other forms (e.g., an optical signal, a current signal, a digital signal, etc.), and the second comparator 344 may compare such output peak value with a corresponding second reference value (which may also take various forms such as an analog signal or a digital signal). Alternatively, instead of the second detection circuit 342 including the photoelectric converter 3421, a second comparatorMay include a photoelectric converter or other conversion circuitry, etc. It is to be understood that the present disclosure is not limited thereto.
As one non-limiting example, the control circuit 340 or feedback controller 345 may be configured to adjust the optical output signal OPT based on the optical interconnect link requirements out Amplitude setting the second reference voltage V REF2 。
The feedback controller 345 may also be referred to as a driver swing feedback controller, and generating the gain control signal may include outputting a driver swing control voltage V based on a comparison output result of two comparators (e.g., a first reference voltage comparator and a second reference voltage comparator) SW To adjust the output swing of the driver. As a specific, non-limiting example, the step of generating or adjusting the gain control signal may comprise an iterative adjustment step of the gain control signal, for example. For example, the feedback controller 345 may be configured (e.g., pre-stored or may be generated by default as per a predetermined setting) with an initial V SW The value is obtained. The feedback controller 345 detects the amplitude of the optical signal output by the modulator through the second detection circuit, and compares the detected peak value with a second reference value (e.g., a reference voltage V) REF2 E.g. preset reference voltage V REF2 ) Make a comparison and if the peak is found to be below V REF2 Then increase V SW Value above V REF2 Then V is decreased SW The value is obtained. And the amplitude of the output optical signal reaches a preset value through multiple iterations of the driver swing feedback controller. In the iterative process, the first detection circuit can detect the output swing of the driver in real time if the output peak voltage V is output PK1 Above a preset value V REF1 This indicates that the driver output amplitude has reached a maximum value, thereby avoiding further increases.
According to some embodiments, the optical-to-electrical converter may include a photodetector to convert the bypass optical signal to a current signal; and a transimpedance amplifier for converting the current signal to the voltage signal.
A schematic block diagram 400 of an optical transmitter and feedback circuit of a variation of the exemplary embodiment of the present disclosure is described below with respect to fig. 4.
As shown in fig. 4, the feedback regulation system of the optical transmitter and the feedback circuit may include a driver 410, a modulator 420, a beam splitter 430, and a control circuit 440.
The modulator 420 converts the driving signal D output by the driver 410 out Modulation to an input optical signal OPT in Up, and then outputs the modulated optical signal to the optical splitter 430. The optical splitter 430 may include an input, a first output, and a second output. The input of the optical splitter 430 may be configured to receive the output optical signal and the first output may be configured to output the bypass optical signal, e.g., coupled to the control circuit 440, for detecting the optical signal amplitude. The second output terminal may be adapted to be optically coupled to an external optical transmission medium, such as an optical fiber or an optical waveguide, for outputting an optical signal OPT out . The splitting ratio of the splitter may be adjusted according to actual needs, for example, distributing 10% power of light to the control circuit, and the disclosure is not limited thereto.
The control circuit 440 may include a first detection circuit 441, a second detection circuit 442, a first comparator 443, a second comparator 444, and a feedback controller 445.
The second detection circuit 442 may include a Photodetector (PD) 4421, a transimpedance amplifier (TIA) 4422, and a peak detector 4423.
According to such embodiments, the feedback controller 445 may comprise a swing controller 4451 and a first digital-to-analog converter DAC1. The swing controller 4451 may be configured to generate a gain control digital signal SW based on the first output voltage and the second output voltage. The first digital-to-analog converter DAC1 may be configured to generate the gain control signal based on the gain control digital signal.
As shown in fig. 4, the feedback controller 445 may include a first reference voltage comparator (U1), a second reference voltage comparator (U2), a first analog-to-digital converter (DAC 1), a second analog-to-digital converter (DAC 2), and a swing controller 4451.
The photodetector 4421 and the transimpedance amplifier 4422 may also be an example of the photoelectric converter 3421 in fig. 3. The input of the photodetector 4421 is connected to the output of one end of the optical splitter, and the output of the photodetector 4421 is connected to the input of the transimpedance amplifier. One implementation of photodetector 4421 is a photodiode employing a PIN structure. Other implementations of photodetector 4421 known to those skilled in the art may also be employed, and the disclosure is not limited thereto. The photodetector 4421 is configured to convert the detected light signal into a current signal. The output of the transimpedance amplifier is connected to a second reference voltage comparator. The transimpedance amplifier 4422 can be implemented by an amplifier parallel resistor, the gain of which can be adjusted by adjusting the parallel resistor. The transimpedance amplifier 4422 may be used to convert the current signal output by the photodetector 4421 into a voltage signal and amplify it to a suitable amplitude, thereby outputting a voltage V MON 。
An input of the first detection circuit 441 may be connected to an output of the driver 410 for detecting the driving signal D out Of the output of the corresponding peak voltage V PK1 . The input terminal of the second detection circuit is connected to the output terminal of the transimpedance amplifier 4422 for detecting V MON Amplitude of (optical signal), output peak voltage V PK2 。
As a specific example, the first reference voltage comparator U1 may compare V PK1 With a preset reference voltage V REF1 The comparison results CMP1.V PK1 To the positive terminal, V, of a reference voltage comparator U1 REF1 To the negative terminal of the reference voltage comparator U1. When the output signal CMP1 of the reference voltage comparator U1 is logic high, it represents V PK1 Greater than V REF1 If the amplitude of the driving signal is larger than the preset value, judging that the amplitude of the driving signal is larger than the preset value; conversely, if the output signal CMP1 is logic low, it represents V PK1 Less than V REF1 Then the driving signal amplitude is less than the preset value. Similarly, the second parameterThe reference voltage comparator U2 can compare V PK2 With a preset reference voltage V REF2 The comparison results CMP2. If the output signal CMP2 is logic high, it represents V PK2 Greater than V REF2 If the amplitude of the optical signal is larger than the preset value, judging that the amplitude of the optical signal is larger than the preset value; if the output signal CMP2 is logic low, it represents V PK2 Less than V REF2 And the amplitude of the driving signal is smaller than the preset value. It is to be understood that the above is merely an example, and the present disclosure is not limited thereto, and other logic configurations or circuit configurations are also possible.
The first analog-to-digital converter DAC1, which may also be referred to as a reference voltage DAC, is used for generating a reference voltage V based on the digital signal REF output by the swing controller 4451 REF1 And V REF2 . As mentioned above, V REF1 Can indicate the driving signal D out Maximum amplitude, V REF2 An optical signal amplitude minimum may be indicated, but the disclosure is not limited thereto.
The second DAC 2 is also called swing DAC, and is used for generating a swing control voltage V from the digital signal SW outputted from the swing controller 4451 SW Thereby controlling the output swing of driver 410.
The swing controller 4451 may generate the swing control digital signal SW according to the received logic signals CMP1 and CMP2. If CMP1=0, it represents that the driving signal swing is lower than the preset value, and the components (e.g., transistors) of the driver 410 are in a normal operating range and the withstand voltage is in an acceptable range. If CMP1=1, it represents that the swing amplitude of the driving signal is higher than or equal to the predetermined value, and the transistor of the driver 410 is out of the tolerable withstand voltage range, so that the swing amplitude of the driving signal needs to be reduced. For the CMP2 signal, if CMP2=0, it represents that the optical signal swing is lower than the preset value, and it is necessary to increase the driver 410 swing to increase the optical output signal amplitude. If CMP2=1, it represents that the swing amplitude of the optical signal is higher than or equal to the preset value, and the amplitude of the output optical signal meets the requirement of the optical link. Thus, the swing controller may adjust the swing control digital signal SW such that the drive signal swing satisfies CMP1=0 and CMP2=1 simultaneously. It is to be understood that the above is merely an example, and the present disclosure is not limited thereto, and other logic configurations or circuit configurations are also possible.
In accordance with one or more embodiments of the present disclosure, a light emitter is also disclosed. The optical transmitter may comprise a driver, a modulator. The driver may be to amplify the input signal based on the gain control signal to generate the drive signal. The modulator may be configured to generate the output optical signal by modulating the drive signal onto the input optical signal. The optical transmitter may further comprise a feedback circuit according to one or more embodiments of the present disclosure.
According to one or more embodiments of the present disclosure, the amplitude of the driver output driving signal and the amplitude of the output optical signal of the modulator can be detected by the control circuit at the optical transmitter end, so as to control the output swing of the driver. Therefore, the problem that the output swing of the driver cannot be adjusted on the premise of ensuring the voltage endurance reliability of the driver transistor in the related art is solved.
According to one or more embodiments of the present disclosure, reliability of long-term operation of the driver can be ensured by the driver transistor withstand voltage protection circuit configured by the first detection circuit and the first reference voltage comparator.
According to one or more embodiments of the present disclosure, the control circuit can be integrated at the optical transmitter end, so as to achieve automatic adjustment of the output swing of the driver, thereby reducing the complexity of joint modulation of the transmitter and the receiver.
According to one or more embodiments of the present disclosure, the output swing of the driver can be adjusted to achieve the best performance on the premise of ensuring the voltage endurance reliability of the driver transistor, the maximum optical signal amplitude output can be realized, and the requirements of long-distance transmission and long-term operation reliability are both considered.
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative and exemplary and not restrictive; the present disclosure is not limited to the disclosed embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps not listed, the indefinite article "a" or "an" does not exclude a plurality, the term "a" or "an" means two or more, and the term "based on" should be construed as "based at least in part on". 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.
Claims (12)
1. A feedback circuit for an optical transmitter, the optical transmitter comprising: a driver for amplifying an input signal based on a gain control signal to generate a driving signal; and a modulator for generating an output optical signal by modulating the drive signal onto an input optical signal, the feedback circuit comprising:
the optical splitter is used for splitting an optical signal with a certain proportion from the output optical signal to serve as a bypass optical signal; and
a control circuit to generate the gain control signal based on a first comparison result between a peak value of the drive signal and a first reference value and a second comparison result between a peak value of the bypass optical signal and a second reference value.
2. The feedback circuit of claim 1, wherein the control circuit comprises:
a first detection circuit for detecting a peak value of the drive signal;
a second detection circuit for detecting a peak value of the bypass optical signal;
a first comparator for comparing a peak value of the driving signal with the first reference value and outputting a first output voltage indicating the first comparison result;
a second comparator for comparing a peak value of the bypass optical signal with the second reference value and outputting a second output voltage indicating the second comparison result; and
a feedback controller to generate the gain control signal based on the first output voltage and the second output voltage.
3. The feedback circuit of claim 2, wherein the first detection circuit comprises a first peak detector.
4. The feedback circuit of claim 2, wherein the second detection circuit comprises:
the photoelectric converter is used for converting the bypass optical signal into a voltage signal; and
a second peak detector for detecting a peak of the voltage signal as a peak of the bypass optical signal.
5. The feedback circuit of claim 4, wherein the optical-to-electrical converter comprises:
a photodetector to convert the bypass optical signal to a current signal; and
a transimpedance amplifier for converting the current signal to the voltage signal.
6. The feedback circuit of claim 2, wherein the feedback controller comprises:
a swing controller to generate a gain control digital signal based on the first output voltage and the second output voltage; and
a first digital-to-analog converter to generate the gain control signal based on the gain control digital signal.
7. The feedback circuit of claim 6, wherein the swing controller is further configured to generate at least one reference value setting signal configured to set the first reference value and the second reference value; and is
Wherein the feedback controller further comprises a second digital-to-analog converter for generating the first reference value and the second reference value based on the at least one reference value setting signal.
8. The feedback circuit of any of claims 1-7, wherein the control circuit is configured to adjust the gain control signal such that a peak value of the drive signal is below the first reference value and a peak value of the bypass light signal is above or equal to the second reference value.
9. The feedback circuit according to claim 8, wherein the first reference value is positively correlated with a transistor withstand voltage value of the driver.
10. The feedback circuit of claim 8, wherein the second reference value positively correlates with a minimum optical output signal amplitude required by an optical link in which the optical transmitter is located.
11. The feedback circuit of any of claims 1-7, wherein the optical splitter comprises:
an input for receiving the output optical signal;
a first output for outputting the bypass optical signal; and
a second output for optically coupling to an external optical transmission medium.
12. An optical transmitter, comprising:
a driver for amplifying an input signal based on a gain control signal to generate a driving signal;
a modulator for generating an output optical signal by modulating the drive signal onto an input optical signal; and
the feedback circuit of any of claims 1-11.
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