CN112925122A - Silicon-based Mach-Zehnder modulator bias control device and system based on pilot frequency method - Google Patents
Silicon-based Mach-Zehnder modulator bias control device and system based on pilot frequency method Download PDFInfo
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
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- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
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- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/21—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour by interference
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Abstract
The invention discloses a silicon-based Mach-Zehnder modulator bias control device and system based on a pilot frequency method, belonging to the field of integrated photonic system control and comprising the following steps: the bias control circuit comprises a monitoring module and a bias control circuit; the input end of the monitoring module is connected with the output end of the silicon-based Mach-Zehnder modulator and is used for acquiring partial output optical signals and converting the partial output optical signals into electric signals representing optical power information; the bias control circuit includes: the output end of the pilot signal generation module is connected with a first thermal modulator of the silicon-based Mach-Zehnder modulator and used for generating a pilot signal and applying the pilot signal to the first thermal modulator; and the input end of the bias voltage adjusting module is connected to the output end of the monitoring module, the output end of the bias voltage adjusting module is connected with a second thermal regulator of the silicon-based Mach-Zehnder modulator, and the bias voltage adjusting module is used for determining the current bias point information according to the electric signals, generating corresponding bias voltage, applying the corresponding bias voltage to the second thermal regulator and compensating the drift of the bias point. The invention can improve the bias control precision of the silicon-based Mach-Zehnder modulator.
Description
Technical Field
The invention belongs to the field of integrated photonic system control, and particularly relates to a silicon-based Mach-Zehnder modulator bias control device and system based on a pilot frequency method.
Background
The traditional LiNbO3 Mach-Zehnder modulator is used as a high-performance electro-optical modulator with high bandwidth, low power consumption and low chirp, and has very wide application in the research fields of optical communication, microwave photon, photoelectric oscillator and the like. However, due to fluctuations in ambient temperature, charge accumulation, and uneven distribution, the bias point of the LiNbO3 mach-zehnder modulator often shifts to some extent, deteriorating the transmission characteristics and affecting the function of the entire modulation system. To solve this problem, a scheme of closed-loop feedback control is often adopted to track the offset of the bias point of the modulator in real time and compensate the drift amount accordingly, so as to stabilize the operating state of the modulator, which is also called bias control.
The pilot method is widely used for bias control of LiNbO3 mach-zehnder modulators as one of closed-loop feedback bias control schemes, and mainly utilizes that transmission characteristic curves of the mach-zehnder modulators have different linearity at different bias points. When a small sinusoidal disturbance signal with fixed frequency is applied to the current bias point and each subharmonic component of the disturbance signal is monitored at the output, the current bias point can be judged, and then the bias voltage applied to the bias end at present is changed to compensate the drift of the bias point. In this scheme, the pilot signal is often added to the bias voltage and then applied to the bias terminal. In the literature "Q.Jiang and M.Kavehrad," A subcarrier-multiplexed coherent FSK system using a Mach-Zehnder modulator with automatic bias control, "IEEE Photonics Technology Letters, vol.5, No.8, pp.941-943,1993. The scheme is characterized in that a pilot frequency method-based LiNbO3 Mach-Zehnder modulator bias control scheme is provided, a pilot frequency signal and a bias voltage are added and then are applied to a bias end, harmonic components of the pilot frequency signal in an output signal are monitored, the drift of a current bias point is tracked, the bias voltage is adjusted in real time, and therefore the performance of the Mach-Zehnder modulator is stabilized.
Compared with the traditional discrete LiNbO3 modulator, the silicon-based Mach-Zehnder modulator has the advantages of small volume, high integration level, low power consumption, easy large-scale manufacture and the like, and is widely applied to the fields of optical communication, microwave photon and photoelectric artificial intelligence. The problem of bias point drift also exists in the silicon-based mach-zehnder modulator, and in the prior art, bias control over the silicon-based mach-zehnder modulator is often realized by directly using a bias control method for the LiNbO3 mach-zehnder modulator based on a pilot frequency method. For example, in the document "H.Chen et al", "Study on auto bias control of a silicon optical modulator in a four-level pulse amplitude modulation format", "Applied Optics, vol.58, No.15, pp.3986-3994,2019/05/202019, doi: 10.1364/AO.58.003986", the bias control method for the LiNbO3 Mach-Zehnder modulator is adopted for the bias control of the silicon-based Mach-Zehnder modulator.
The existing pilot frequency method-based Mach-Zehnder modulator bias control scheme mainly aims at a discrete LiNbO3 Mach-Zehnder modulator, the change of the bias point is mainly based on the linear electro-optical effect of LiNbO3 crystals, and the bias voltage is in direct proportion to the phase shift generated by the linear electro-optical effect. The silicon-based mach-zehnder modulator usually adopts a thermal phase shifter to set a bias point, and the bias point is adjusted by utilizing a nonlinear thermo-optical effect, so that the bias voltage and the phase shift generated by the bias voltage are nonlinear. Therefore, when the existing bias control scheme for the LiNbO3 mach-zehnder modulator based on the pilot method is applied to the silicon-based mach-zehnder modulator, the phase shift amount caused by the pilot signal generates extra nonlinear distortion, thereby affecting the accuracy of the whole control system.
Disclosure of Invention
Aiming at the defects and improvement requirements of the prior art, the invention provides a silicon-based Mach-Zehnder modulator bias control device and system based on a pilot frequency method, and aims to reduce the distortion of a pilot frequency signal caused by the nonlinear effect of a thermal phase shifter in the silicon-based Mach-Zehnder modulator and improve the bias control precision of the silicon-based Mach-Zehnder modulator.
To achieve the above object, according to one aspect of the present invention, there is provided a bias control apparatus for a silicon-based mach-zehnder modulator based on a pilot method, comprising: the bias control circuit comprises a monitoring module and a bias control circuit;
the monitoring module is used for acquiring partial output optical signals of the silicon-based Mach-Zehnder modulator and converting the partial output optical signals into electric signals representing optical power information;
the bias control circuit includes: the device comprises a pilot signal generation module and a bias voltage regulation module;
the pilot signal generating module is connected with the output end of the first thermal modulator of the silicon-based Mach-Zehnder modulator and used for generating a pilot signal and applying the pilot signal to the first thermal modulator;
the bias voltage adjusting module is used for extracting each subharmonic component of the pilot signal from the electric signal to determine the current bias point information, generating corresponding bias voltage and applying the corresponding bias voltage to the second thermal modulator so as to compensate the drift of the bias point;
the first thermal modulator and the second thermal modulator are two different thermal modulators in the silicon-based Mach-Zehnder modulator.
Further, the pilot signal is a square wave signal.
Further, the minimum value of the square wave signal is 0 level.
Further, the bias voltage adjustment module includes: the device comprises an analog front end unit, a digital control unit and an output driving unit;
the input end of the analog front-end unit is used as the input end of the bias voltage adjusting module and is used for extracting each subharmonic component of the pilot signal from the electric signal and converting the subharmonic component into a digital signal;
the input end of the digital control unit is connected to the output end of the analog front-end unit, and the digital control unit is used for judging the bias point of the silicon-based Mach-Zehnder modulator according to each harmonic component of the pilot signal and determining the magnitude of bias voltage for compensating the drift of the bias point;
and the input end of the output driving unit is connected to the digital control unit, and the output end of the output driving unit is used as the output end of the bias voltage adjusting module and is used for applying bias voltage with corresponding magnitude to the second thermal regulator according to the magnitude of the bias voltage.
Further, the bias control circuit is implemented by an integrated circuit on chip, or by a board-level circuit, or by a discrete device.
Further, the analog front end unit is a phase-locked amplifier.
Further, the output driving unit is a power digital-to-analog converter.
Further, the monitoring module is a photodiode or a contactless integrated photonic probe.
According to another aspect of the present invention, there is provided a silicon-based mach-zehnder modulator system comprising: the invention provides a silicon-based Mach-Zehnder modulator and a bias control device of the silicon-based Mach-Zehnder modulator based on a pilot frequency method.
According to still another aspect of the present invention, there is provided an optical IQ modulator system based on a silicon-based mach-zehnder modulator, comprising an optical IQ modulator based on a silicon-based mach-zehnder modulator, the optical IQ modulator comprising a first silicon-based mach-zehnder modulator, a second silicon-based mach-zehnder modulator, and a third thermal modulator; the fourth heat adjuster and the fifth heat adjuster are two different heat adjusters in the first silicon-based Mach-Zehnder modulator, and the sixth heat adjuster and the seventh heat adjuster are two different heat adjusters in the second silicon-based Mach-Zehnder modulator;
the optical IQ modulator system further comprises: a silicon-based Mach-Zehnder modulator bias control device based on a pilot frequency method;
the bias control device includes: the bias control circuit comprises a monitoring module and a bias control circuit;
the input end of the monitoring module is connected to the output end of the optical IQ modulator, and the monitoring module is used for acquiring part of output optical signals of the optical IQ modulator and converting the output optical signals into electric signals representing optical power information;
the bias control circuit includes: the device comprises a pilot signal generation module and a bias voltage regulation module;
a pilot signal generating module, the output end of which is connected with the fourth heat modulator and the sixth heat modulator respectively, and which is used for generating the pilot signal and applying the pilot signal to the fourth heat modulator and the sixth heat modulator;
and the input end of the bias voltage adjusting module is connected to the output end of the monitoring module, the output end of the bias voltage adjusting module is respectively connected with the third thermal modulator, the fifth thermal modulator and the seventh thermal modulator, and the bias voltage adjusting module is used for extracting each subharmonic component of the pilot signal from the electric signal to determine the current bias point information of the first silicon-based Mach-Zehnder modulator, the second silicon-based Mach-Zehnder modulator and the third thermal modulator, generating corresponding bias voltage and applying the corresponding bias voltage to the third thermal modulator, the fifth thermal modulator and the seventh thermal modulator so as to compensate the drift of the bias point.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) the invention relates to a silicon-based Mach-Zehnder modulator bias control device based on a pilot frequency method, which determines the current bias point information of a silicon-based Mach-Zehnder modulator based on the power information of an optical signal output by the silicon-based Mach-Zehnder modulator, determines a bias voltage for compensating the drift of the bias point, and then respectively applies the bias voltage and the pilot signal to two different heat modulators in the silicon-based Mach-Zehnder modulator, so that the phase shift quantity generated by the pilot signal is only related to the pilot signal per se and is not influenced by the current bias voltage.
(2) According to the silicon-based Mach-Zehnder modulator bias control device based on the pilot frequency method, on the basis that bias voltage and pilot frequency signals are respectively applied to different heat modulators, square wave signals are used as the pilot frequency signals, since phase shift generated by the heat modulators is in direct proportion to the square of the voltage applied to the heat modulators, and when the square wave signals are used as the pilot frequency signals, the phase shift waveforms generated by the pilot frequency signals can be maintained to a certain extent, the distortion of the pilot frequency signals caused by the nonlinear effect of the heat modulators can be reduced to the greatest extent, and the bias control accuracy of the silicon-based Mach-Zehnder modulator is further improved; in the preferred scheme, the minimum value of the square wave signal is 0 level, and the square wave signal is close to the digital signal, so that the generation is convenient, and the generation of the pilot signal is simplified on the basis of ensuring the bias control precision.
(3) The silicon-based Mach-Zehnder modulator bias control device based on the pilot frequency method can realize accurate bias control on any silicon-based Mach-Zehnder modulator comprising two or more heat modulators, and is high in applicability.
Drawings
FIG. 1 is a schematic structural diagram of a conventional silicon-based Mach-Zehnder modulator;
FIG. 2 is a schematic diagram of the nonlinear transfer characteristic of a conventional heat conditioner;
FIG. 3 is a diagram illustrating the non-linear distortion of a pilot signal caused by a conventional bias control method;
fig. 4 is a schematic diagram of a bias control device of a silicon-based mach-zehnder modulator based on a pilot frequency method according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating an undistorted pilot signal according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a specific implementation of the silicon-based Mach-Zehnder modulator bias control device based on the pilot frequency method shown in FIG. 4;
fig. 7 is a schematic diagram of an optical IQ modulator system based on a silicon-based mach-zehnder modulator according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
Before explaining the technical scheme of the invention in detail, the basic principle related to the existing silicon-based Mach-Zehnder modulator is briefly introduced as follows:
the basic structure of the silicon-based Mach-Zehnder modulator is shown in FIG. 1, and mainly comprises optical waveguides, an optical coupler, a high-speed phase modulator, a heat regulator and other modules; when the silicon-based Mach-Zehnder modulator works, an input optical signal is divided into two paths after being input from the input port of the first coupler, and the two paths are transmitted through the upper arm and the lower arm of the silicon-based Mach-Zehnder modulator respectively; the upper side output light of the first coupler is input to two input ends of the second coupler together with the lower side output light after passing through the heat modulator and the phase modulator to realize beam combination; one output of the second coupler is used as the output optical signal of the whole system, and the other output is used as the feedback signal to output the bias control device, so as to realize the bias control.
A heat modulator in the silicon-based Mach-Zehnder modulator is used for adjusting the phase difference of the upper arm and the lower arm so as to adjust the current bias point, and the conversion from voltage to phase is realized by utilizing the nonlinear thermo-optical effect; in general, for a resistive type thermal phase shifter, the phase shift produced is proportional to the power of the applied voltage, i.e. to the square of the applied voltage, and the transfer characteristic curve is shown in fig. 2. In a conventional bias control scheme for LiNbO3 mach-zehnder modulator, a bias voltage and a pilot signal are added by a circuit means and then applied to a bias terminal, and when the bias control method is directly applied to a silicon-based mach-zehnder modulator, a certain degree of nonlinear distortion occurs in a phase shift amount generated by a pilot signal part, and the distortion is related to the magnitude of the bias voltage, as shown in fig. 3; the non-linear distortion affects the judgment of the bias control system based on the pilot method on the current bias point, thereby affecting the accuracy and precision of locking.
In order to solve the technical problem that when the existing bias control method aiming at the LiNbO3 Mach-Zehnder modulator is directly applied to the silicon-based Mach-Zehnder modulator, the phase shift amount caused by a pilot signal generates extra nonlinear distortion, so that the accuracy of the whole control system is influenced, the invention provides a bias control device and system of the silicon-based Mach-Zehnder modulator based on the pilot method, and the whole thought is as follows: bias voltage and pilot signals for compensating bias point drift are respectively applied to two different thermal modulators of the silicon-based Mach-Zehnder modulator so as to reduce distortion brought to the pilot signals by the nonlinear effect of the thermal modulators and improve bias control precision; on the basis, the square wave signal is used as the pilot signal, so that the distortion of the pilot signal caused by the nonlinear effect of the thermal modulator is reduced to the maximum extent.
The following are examples.
Example 1:
a silicon-based mach-zehnder modulator bias control device based on a pilot method, as shown in fig. 4, includes: the bias control circuit comprises a monitoring module and a bias control circuit;
the monitoring module is used for acquiring partial output optical signals of the silicon-based Mach-Zehnder modulator and converting the partial output optical signals into electric signals representing optical power information;
the bias control circuit includes: the device comprises a pilot signal generation module and a bias voltage regulation module;
the pilot signal generating module is connected with the output end of the first thermal modulator of the silicon-based Mach-Zehnder modulator and used for generating a pilot signal and applying the pilot signal to the first thermal modulator;
the bias voltage adjusting module is used for extracting each subharmonic component of the pilot signal from the electric signal to determine the current bias point information, generating corresponding bias voltage and applying the corresponding bias voltage to the second thermal modulator so as to compensate the drift of the bias point;
the first heat regulator and the second heat regulator are two different heat regulators in the silicon-based Mach-Zehnder modulator;
since the phase shift generated by the thermal phase shifter is proportional to the square of the voltage applied thereto, when the offset voltage and the pilot signal are added and then applied to the offset terminal, the magnitude of the pilot component in the generated phase shift amount is not only related to the pilot signal itself but also related to the current offset voltage value; in the present embodiment, the bias control device of the silicon-based mach-zehnder modulator based on the pilot frequency method determines the current bias point information of the silicon-based mach-zehnder modulator based on the power information of the optical signal output by the silicon-based mach-zehnder modulator, and after determining the bias voltage for compensating the drift of the bias point, the bias voltage and the pilot signal are respectively applied to two different thermal modulators in the silicon-based mach-zehnder modulator, so that the phase shift amount generated by the pilot signal is only related to the pilot signal itself and is not influenced by the current bias voltage.
Since the phase shift generated by the thermal phase shifter is proportional to the square of the voltage applied to the thermal phase shifter, when the pilot signal is a sinusoidal signal, the waveform of the generated phase shift is significantly distorted, as shown in fig. 3; in order to reduce the distortion of the pilot signal caused by the nonlinear effect of the thermal modulator to the maximum, as a preferred embodiment, as shown in fig. 4, in this embodiment, the pilot signal is a square wave signal, and in order to facilitate the generation of the pilot signal, in this embodiment, the minimum value of the square wave signal is 0 level; the square wave signal is used as the pilot signal, the generated phase shift waveform can be maintained to a certain extent, the phase shift amount generated by the square wave signal is as shown in fig. 5, and as can be seen from fig. 5, the phase variable does not contain nonlinear distortion, so that the nonlinear distortion of the pilot signal can be reduced to the greatest extent, and the bias control precision can be effectively improved.
As an alternative implementation, as shown in fig. 4, in this embodiment, the bias voltage adjusting module includes: the device comprises an analog front end unit, a digital control unit and an output driving unit;
the input end of the analog front-end unit is used as the input end of the bias voltage adjusting module and is used for extracting each subharmonic component of the pilot signal from the electric signal and converting the subharmonic component into a digital signal; optionally, as shown in fig. 6, in the present embodiment, the analog front end unit is a lock-in amplifier, and it should be noted that, this is merely an exemplary description and should not be construed as the only limitation to the present invention;
the input end of the digital control unit is connected to the output end of the analog front-end unit, and the digital control unit is used for judging the bias point of the silicon-based Mach-Zehnder modulator according to each harmonic component of the pilot signal and determining the magnitude of bias voltage for compensating the drift of the bias point;
the input end of the output driving unit is connected to the digital control unit, and the output end of the output driving unit is used as the output end of the bias voltage adjusting module and is used for applying bias voltage with corresponding magnitude to the second heat regulator according to the magnitude of the bias voltage; alternatively, as shown in fig. 6, in the present embodiment, the output driving unit is a power digital-to-analog converter, and it should be noted that this is merely an exemplary illustration and should not be construed as the only limitation to the present invention;
in this embodiment, the bias control circuit is implemented by an integrated circuit on a chip, or by a board-level circuit, or by a discrete device;
in this embodiment, the monitoring module may be any one of a photodiode, a contactless integrated photonic probe (CLIPP), and the like, which can represent the magnitude of optical power, and optionally, as shown in fig. 6, in this embodiment, the monitoring module is specifically a photodiode.
It should be noted that any silicon-based mach-zehnder modulator including two or more thermal modulators may implement accurate bias control by using the bias control device of the silicon-based mach-zehnder modulator based on the pilot method provided in this embodiment. In practical application, two different heat modulators are selected from the silicon-based Mach-Zehnder modulator, and bias voltage and pilot signals are applied respectively; after the pilot signal is applied to the heat regulator, the monitoring module can acquire part of output optical signals, convert the output optical signals into electric signals and transmit the electric signals to the analog front end in the bias control circuit; through the processing and analysis of the analog front end and the digital control module, the magnitude of each harmonic component of a pilot signal in an output signal at the current moment can be obtained, so that the current bias point information is obtained, and the current bias voltage is adjusted in real time through output driving; with the continuous change of the bias voltage, the phase shift amount of the thermal modulator is changed, and finally the bias point of the modulator is stabilized at the required bias point, so that a stable feedback control loop is realized.
Example 2:
a silicon-based mach-zehnder modulator system, as shown in fig. 4 and 6, comprising: a silicon-based mach-zehnder modulator and the pilot method-based silicon-based mach-zehnder modulator bias control device provided in embodiment 1 above;
optionally, in this embodiment, the phase modulator of the silicon-based mach-zehnder modulator is made of a silicon-based material; in other embodiments of the present invention, the phase modulator of the silicon-based mach-zehnder modulator may also be made of materials such as LiNbO3, InP, etc. capable of performing heterogeneous integration with the silicon-based platform;
optionally, in this embodiment, the coupler for splitting and combining beams in the mach-zehnder modulator may be composed of a Y-type coupler and a 3dB coupler; in other embodiments of the present invention, the optical module may also be composed of any photonic module with light splitting and combining functions, such as a multi-mode interferometer;
in order to facilitate inputting part of the output optical signals into the bias control circuit as feedback signals, in the silicon-based Mach-Zehnder modulator, a light splitter can be connected behind the second coupler and is used for splitting the optical signals obtained by combining the upper arm and the lower arm into two paths, most of the light is output as the output optical signals, and a small part of the light is input into the monitoring module.
Since the bias control device for the silicon-based mach-zehnder modulator based on the pilot frequency method provided in embodiment 1 can realize accurate bias control of the silicon-based mach-zehnder modulator, in the silicon-based mach-zehnder modulator system provided in this embodiment, the bias point drift of the silicon-based mach-zehnder modulator can be effectively compensated, and the silicon-based mach-zehnder modulator system has good transmission performance.
Example 3:
an optical IQ modulator system based on a silicon-based mach-zehnder modulator, as shown in fig. 7, comprising: an optical IQ modulator based on a silicon-based Mach-Zehnder modulator and a silicon-based Mach-Zehnder modulator bias control device based on a pilot frequency method.
As shown in fig. 7, the optical IQ modulator based on the silicon-based mach-zehnder modulator is composed of two silicon-based mach-zehnder modulators, an additional thermal modulator (i.e., the thermal modulator 1 in fig. 7) and a coupler; one of the silicon-based mach-zehnder modulators includes two different thermostats, namely, the thermostat 2 and the thermostat 3 in fig. 7; another silicon-based mach-zehnder modulator also includes two different thermostats, namely, the thermostat 4 and the thermostat 5 in fig. 7;
similarly to embodiment 1 described above, in the present embodiment, the bias control device includes: the bias control circuit comprises a monitoring module and a bias control circuit;
the input end of the monitoring module is connected to the output end of the optical IQ modulator, and the monitoring module is used for acquiring part of output optical signals of the optical IQ modulator and converting the output optical signals into electric signals representing optical power information;
the bias control circuit includes: the device comprises a pilot signal generation module and a bias voltage regulation module;
a pilot signal generating module, the output end of which is connected with the thermal modulator 2 and the thermal modulator 4 respectively, and which is used for generating the pilot signal and applying the pilot signal to the two thermal modulators;
the bias voltage adjusting module is connected with the input end of the monitoring module, the output end of the bias voltage adjusting module is connected with the thermal regulator 1, the thermal regulator 3 and the thermal regulator 5, and the bias voltage adjusting module is used for extracting each subharmonic component of the pilot signal from the electric signal so as to determine the current bias point information of the two silicon-based Mach-Zehnder modulators and the thermal regulator 1, generate corresponding bias voltages and apply the corresponding bias voltages to the thermal regulator 1, the thermal regulator 3 and the thermal regulator 5, so that the drift of the bias points is compensated;
optionally, as shown in fig. 7, in this embodiment, the pilot signal is also a square wave signal;
in this embodiment, the detailed implementation of each module in the bias control device can refer to the description of embodiment 1.
The embodiment can complete the precise bias control of the optical IQ modulator, the bias point can be effectively compensated, and the transmission performance is good.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A silicon-based Mach-Zehnder modulator bias control device based on a pilot frequency method is characterized by comprising the following components: the bias control circuit comprises a monitoring module and a bias control circuit;
the input end of the monitoring module is connected to the output end of the silicon-based Mach-Zehnder modulator, and the monitoring module is used for acquiring partial output optical signals of the silicon-based Mach-Zehnder modulator and converting the partial output optical signals into electric signals representing optical power information;
the bias control circuit includes: the device comprises a pilot signal generation module and a bias voltage regulation module;
the output end of the pilot signal generation module is connected to a first thermal modulator of the silicon-based Mach-Zehnder modulator, and the pilot signal generation module is used for generating a pilot signal and applying the pilot signal to the first thermal modulator;
the input end of the bias voltage adjusting module is connected to the output end of the monitoring module, the output end of the bias voltage adjusting module is connected to a second thermal modulator of the silicon-based Mach-Zehnder modulator, and the bias voltage adjusting module is used for extracting each subharmonic component of the pilot signal from the electric signal to determine current bias point information, generating corresponding bias voltage and applying the corresponding bias voltage to the second thermal modulator so as to compensate the drift of the bias point;
wherein the first and second thermostats are two different thermostats of the silica-based Mach-Zehnder modulator.
2. The pilot-based silicon-based mach-zehnder modulator bias control device of claim 1, wherein the pilot signal is a square wave signal.
3. The pilot-based silicon-based mach-zehnder modulator bias control device of claim 2, wherein a minimum value of the square wave signal is 0 level.
4. The pilot-method-based silicon-based mach-zehnder modulator bias control device of any of claims 1-3, wherein the bias voltage adjusting module comprises: the device comprises an analog front end unit, a digital control unit and an output driving unit;
the input end of the analog front-end unit is used as the input end of the bias voltage adjusting module, and the analog front-end unit is used for extracting each subharmonic component of the pilot signal from the electric signal and converting the subharmonic component into a digital signal;
the input end of the digital control unit is connected to the output end of the analog front-end unit, and the digital control unit is used for judging a bias point where the silicon-based Mach-Zehnder modulator is located according to each harmonic component of the pilot signal and determining the magnitude of bias voltage for compensating drift of the bias point;
and the input end of the output driving unit is connected to the digital control unit, the output end of the output driving unit is used as the output end of the bias voltage adjusting module, and the output driving unit is used for applying bias voltage with corresponding magnitude to the second heat regulator according to the magnitude of the bias voltage.
5. The pilot-based silicon-based mach-zehnder modulator bias control device of claim 4, wherein the bias control circuit is implemented by an integrated circuit on chip, or by a board-level circuit, or by a discrete device.
6. The pilot-based silicon-based mach-zehnder modulator bias control device of claim 4 wherein the analog front-end unit is a lock-in amplifier.
7. The pilot-method-based silicon-based mach-zehnder modulator bias control device of claim 4, wherein the output driving unit is a power digital-to-analog converter.
8. The pilot-method-based silicon-based mach-zehnder modulator bias control device of any of claims 1-3, wherein the monitoring module is a photodiode or a contactless integrated photonic probe.
9. A silicon-based mach-zehnder modulator system comprising: silicon-based mach-zehnder modulator and a pilot-based silicon-based mach-zehnder modulator bias control apparatus according to any of claims 1-8.
10. An optical IQ modulator system based on a silicon-based Mach-Zehnder modulator comprises an optical IQ modulator based on the silicon-based Mach-Zehnder modulator, wherein the optical IQ modulator comprises a first silicon-based Mach-Zehnder modulator, a second silicon-based Mach-Zehnder modulator and a third heat modulator; the fourth heat adjuster and the fifth heat adjuster are two different heat adjusters in the first silicon-based Mach-Zehnder modulator, and the sixth heat adjuster and the seventh heat adjuster are two different heat adjusters in the second silicon-based Mach-Zehnder modulator;
characterized in that the optical IQ modulator system further comprises: a silicon-based Mach-Zehnder modulator bias control device based on a pilot frequency method;
the bias control device includes: the bias control circuit comprises a monitoring module and a bias control circuit;
the input end of the monitoring module is connected to the output end of the optical IQ modulator, and the monitoring module is used for acquiring a part of output optical signals of the optical IQ modulator and converting the part of output optical signals into electric signals representing optical power information;
the bias control circuit includes: the device comprises a pilot signal generation module and a bias voltage regulation module;
the output end of the pilot signal generation module is connected with the fourth heat modulator and the sixth heat modulator respectively, and the pilot signal generation module is used for generating a pilot signal and applying the pilot signal to the fourth heat modulator and the sixth heat modulator;
the input end of the bias voltage adjusting module is connected to the output end of the monitoring module, the output end of the bias voltage adjusting module is respectively connected with the third thermal modulator, the fifth thermal modulator and the seventh thermal modulator, and the bias voltage adjusting module is used for extracting each subharmonic component of the pilot signal from the electrical signal to determine the current bias point information of the first silicon-based mach-zehnder modulator, the second silicon-based mach-zehnder modulator and the third thermal modulator, generating corresponding bias voltages, and applying the bias voltages to the third thermal modulator, the fifth thermal modulator and the seventh thermal modulator so as to compensate the drift of the bias point.
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