CN113452450A - Light polarization modulation method, light polarization modulation module and light chip - Google Patents
Light polarization modulation method, light polarization modulation module and light chip Download PDFInfo
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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
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Abstract
The embodiment of the disclosure provides a light polarization modulation method, a light polarization modulation module and a light chip. The optical polarization modulation method includes: splitting the optical signal into a first optical signal and a second optical signal by an optical splitter; according to the first electrical modulation signal, adjusting the phase of the first optical signal by using a first arm of a first phase shift arm to obtain a third optical signal, wherein a relative phase difference exists between the third optical signal and the second optical signal, and the first arm of the first phase shift arm is provided with a first phase modulator; processing the second optical signal and the third optical signal by using an optical beam combiner to generate a fourth optical signal and/or a fifth optical signal under the condition that the relative phase difference satisfies a phase threshold; adjusting the fourth optical signal by using a second support arm of a second phase shift arm according to the second electrical modulation signal to generate a sixth optical signal, wherein the upper arm of the second phase shift arm is provided with a second phase modulator; and combining the fifth optical signal and/or the sixth optical signal into a seventh optical signal through the polarization rotation beam combiner.
Description
Technical Field
The present disclosure relates to the field of optical communication technologies, and in particular, to a method for optical polarization modulation, an optical polarization modulation module, and an optical chip.
Background
Optical polarization modulation is the use of external electrical signals to change the polarization state of light so that it carries modulation information. High-speed modulators in existing optical communication systems implement modulation of optical intensity and phase mainly based on optical waveguide structures.
In implementing the disclosed concept, the inventors found that there are at least the following problems in the related art: the requirement on the electrical modulation signal is high, so that the polarization state contrast obtained by modulation is poor.
Disclosure of Invention
In view of this, the embodiments of the present disclosure provide an optical polarization modulation method, an optical polarization modulation module, and an optical chip.
An aspect of an embodiment of the present disclosure provides a method of modulating light polarization, including:
splitting the optical signal into a first optical signal and a second optical signal by an optical splitter;
adjusting the phase of the first optical signal by using a first arm of a first phase shift arm according to a first electrical modulation signal to obtain a third optical signal, wherein the third optical signal and the second optical signal have a relative phase difference, and the first arm of the first phase shift arm is provided with a first phase modulator;
processing the second optical signal and the third optical signal by an optical beam combiner to generate a fourth optical signal and/or a fifth optical signal when the relative phase difference satisfies a phase threshold;
adjusting the fourth optical signal by using a second arm of a second phase shift arm according to a second electrical modulation signal to generate a sixth optical signal, wherein a second phase modulator is arranged on an upper arm of the second phase shift arm; and
and combining the fifth optical signal and/or the sixth optical signal into a seventh optical signal by a polarization rotation beam combiner.
According to an embodiment of the present disclosure, the intensity of each of the first optical signal and the second optical signal is half of the intensity of the optical signal.
According to an embodiment of the present disclosure, the phase threshold includes a first phase threshold, a second phase threshold, and a third phase threshold;
wherein the processing the second optical signal and the third optical signal by the optical beam combiner to generate a fourth optical signal and/or a fifth optical signal when the relative phase difference satisfies a phase threshold comprises:
the optical beam combiner generates an eighth optical signal according to the second optical signal and the third optical signal;
processing the eighth optical signal with the optical beam combiner to generate the fourth optical signal when the relative phase difference satisfies the first phase threshold; or
Processing the eighth optical signal with the optical beam combiner to generate the fifth optical signal when the relative phase difference satisfies the second phase threshold; or
And processing the eighth optical signal by the optical beam combiner to generate the fourth optical signal and the fifth optical signal when the relative phase difference satisfies the third phase threshold.
According to an embodiment of the present disclosure, the intensity of the fourth optical signal is (cos (θ/2))2The intensity of the fifth optical signal is (sin (theta/2))2Multiple, θ characterizes the relative phase difference.
According to an embodiment of the present disclosure, a phase difference between the sixth optical signal and the fourth optical signal
Determined by formula (1);
wherein, V2Voltage, V, representing the second phase modulatorπ2Representing half waves of a second phase modulatorA voltage.
Another aspect of an embodiment of the present disclosure provides an optical polarization modulation module, including:
an optical splitter for splitting an optical signal into a first optical signal and a second optical signal;
a first phase shift arm, where the first phase shift arm includes a first support arm and a third support arm, the first support arm is provided with a first phase modulator, an input end of the first support arm and an input end of the third support arm are both connected to an output end of the optical splitter, the first support arm is configured to obtain a first electrical modulation signal, and adjust a phase of the first optical signal according to the first electrical modulation signal to obtain a third optical signal, and the third support arm is configured to transmit the second optical signal, where a relative phase difference exists between the third optical signal and the second optical signal;
an optical combiner, an output end of the first arm and an output end of the third arm are both connected to an input end of the optical combiner, and the optical combiner is configured to process the second optical signal and the third optical signal by using the optical combiner to generate a fourth optical signal and/or a fifth optical signal when the relative phase difference satisfies a phase threshold;
a second phase shift arm, where the second phase shift arm includes a second support arm and a fourth support arm, the second support arm is provided with a second phase modulator, an input end of the second support arm and an input end of the fourth support arm are both connected to an output end of the optical combiner, the second support arm is configured to obtain a second electrical modulation signal, and perform phase adjustment on the fourth optical signal according to the second electrical modulation signal to generate a sixth optical signal, and the fourth support arm is configured to transmit the fifth optical signal; and
and the output end of the second support arm and the output end of the fourth support arm are both connected with the input end of the polarization rotation beam combiner, and the polarization rotation beam combiner is used for combining the fifth optical signal and/or the sixth optical signal into a seventh optical signal.
According to an embodiment of the present disclosure, the optical polarization modulation module further comprises:
an input waveguide, an output end of which is connected to an input end of the optical splitter, the input waveguide being configured to obtain the optical signal; and/or
And an input end of the output waveguide is connected with an output end of the polarization rotation beam combiner, and the output waveguide is used for outputting the seventh optical signal.
According to an embodiment of the present disclosure, the optical splitter is one of a coupler, a Y-type beam splitter, a multimode interferometer type beam splitter, and a directional coupler type beam splitter; and/or
The optical beam combiner is one of a coupler, a multimode interferometer type beam combiner and a directional coupling type beam combiner.
According to an embodiment of the present disclosure, the number of the second phase shift arms is at least one.
Another aspect of the embodiments of the present disclosure provides an optical chip including the optical polarization modulation module described above.
According to the embodiment of the disclosure, a first electrical modulation signal is loaded on a first optical signal through a first phase shift arm to generate a third optical signal, a beam combiner is used for processing a second optical signal and the third optical signal to generate a fourth optical signal and/or a fifth optical signal, a second phase shift arm is used for loading a second electrical modulation signal on the fourth optical signal to generate a sixth optical signal, a polarization rotation beam combiner is used for combining the fifth optical signal and/or the sixth optical signal into a seventh optical signal, and the requirement for the electrical modulation signal is reduced through the technical means of loading the electrical modulation signal twice, so that the imperfect characteristic caused by the high voltage requirement of the electrical modulation signal can be reduced, the technical problem that the requirement for the electrical modulation signal is high, the polarization state contrast obtained by modulation is poor is at least partially overcome, and the voltage of the electrical modulation signal is reduced, thereby reducing the imperfect characteristics and further improving the technical effect of the contrast of the polarization state.
Drawings
The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:
fig. 1 schematically shows a flow diagram of a method of optical polarization modulation according to an embodiment of the present disclosure.
Fig. 2 schematically illustrates a flow diagram for generating a fourth optical signal and/or a fifth optical signal according to an embodiment of the disclosure; and
fig. 3 schematically illustrates a structural schematic diagram of an optical polarization modulation module according to an embodiment of the present disclosure.
In the above figures, the reference numerals have the following meanings:
310-an optical splitter;
320-a first phase shift arm;
321-a first support arm;
322-a first phase modulator;
323-third support arm;
330-second phase shift arm;
331-a second arm;
332-a second phase modulator;
333-fourth support arm;
340-polarization rotating beam combiner;
350-light beam combiner.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.
Where a convention analogous to "at least one of A, B and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B and C" would include but not be limited to systems that have a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.). Where a convention analogous to "A, B or at least one of C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B or C" would include but not be limited to systems that have a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.).
The Quantum Key Distribution (QKD) system has high information theory security. The security is based on the basic rule of quantum physics, is derived from the basic rule of quantum physics, and ensures that the key and the encrypted information still keep lower leakage possibility even after the rapid development of future technologies and algorithms, thereby having greater scientific significance and application value. The quantum key distribution system can ensure the safe communication of the two parties by combining the encryption mode of the one-time pad, so the technology can be applied to high-confidentiality mechanisms such as banks and the like.
In classical optical communication, most of active and passive devices and the like can be integrated into an optical chip, and the devices also need to be used in a quantum key distribution system. Meanwhile, the optical chip has the characteristics of miniaturization and low cost, and is favorable for promoting the wide application of the quantum key distribution technology in the future, so that the optical chip is very suitable for a quantum key distribution system.
In a polarization-encoded quantum key distribution protocol, an optical chip is required to perform polarization modulation on an input optical signal to obtain polarization states required by a plurality of protocols. A number of different on-chip polarization modulation methods have been developed. For example, two polarization modulation methods using a single or two Mach-Zehnder Interferometer (MZI) structures. However, these two modulation methods can only obtain two mutually orthogonal fixed polarization modes, and thus are generally suitable for optical polarization modulation in classical communication.
Meanwhile, the optical polarization modulation scheme of the single MZI structure combined with the single phase modulation module has the characteristic of simple structure, however, the single MZI structure needs 3 pi/2 phase modulation and corresponding electrical modulation signals, the phase modulation of the general phase modulator for optical signals is in positive correlation with the input electrical modulation signals, and the larger phase modulation needs higher electrical modulation signal voltage.
Furthermore, a phase modulator may exist: the speed of the phase modulation amplitude increasing with the input modulation voltage gradually becomes slower after the modulation voltage becomes larger (the modulation module saturates with the voltage increase), and the phase modulation amplitude becomes larger, which brings extra attenuation to the optical signal and other various imperfect characteristics. Thus, the use of a lower electrical modulation signal voltage results in less imperfect characteristics, and the resulting polarization state contrast can be improved. The polarization modulation scheme with a single MZI structure requires high electrical modulation signal requirements, which may cause saturation and high imperfect characteristics of the phase modulation module, and thus it is difficult to obtain a polarization state with high contrast.
The dual MZI structure is combined with the four phase modulation modules to perform optical polarization modulation, and has the characteristics of good polarization contrast and low requirement on electrical modulation signals, however, the optical polarization modulation structure requires that at least one phase modulation module is arranged on an interference arm of each MZI structure, and the design and manufacturing difficulty of an optical chip is greatly increased.
Therefore, the optical polarization modulation method in the related art has high requirements for electrical modulation signals, and the problems of poor contrast of the polarization state of the modulated optical signals, high design and manufacturing difficulty and the like limit the further development of the optical chip using the quantum key distribution technology.
In view of this, embodiments of the present disclosure provide an optical polarization modulation method, an optical polarization modulation module, and an optical chip. The optical polarization modulation method includes splitting an optical signal into a first optical signal and a second optical signal by an optical beam splitter; adjusting the phase of the first optical signal by using a first arm of the first phase shift arm according to the first electrical modulation signal to obtain a third optical signal; processing the second optical signal and the third optical signal by using an optical beam combiner to generate a fourth optical signal and/or a fifth optical signal under the condition that the relative phase difference satisfies a phase threshold; adjusting the fourth optical signal by using a second support arm of the second phase shift arm according to the second electrical modulation signal to generate a sixth optical signal; and combining the fifth optical signal and/or the sixth optical signal into a sixth optical signal through the polarization rotation beam combiner.
Fig. 1 schematically shows a flow diagram of a method of optical polarization modulation according to an embodiment of the present disclosure.
As shown in fig. 1, the optical polarization modulation method may include operations S101 to S105.
In operation S101, an optical signal is split into a first optical signal and a second optical signal by an optical splitter.
In operation S102, a phase of the first optical signal is adjusted by using a first arm of a first phase shift arm according to the first electrical modulation signal, so as to obtain a third optical signal, where the third optical signal and the second optical signal have a relative phase difference therebetween, and the first arm of the first phase shift arm is provided with a first phase modulator.
In operation S103, the second optical signal and the third optical signal are processed by the optical beam combiner to generate a fourth optical signal and/or a fifth optical signal in case that the relative phase difference satisfies a phase threshold.
In operation S104, the fourth optical signal is adjusted by the second arm of the second phase shift arm according to the second electrical modulation signal to generate a sixth optical signal, wherein the upper arm of the second phase shift arm is provided with a second phase modulator.
In operation S105, the fifth optical signal and/or the sixth optical signal are combined into a seventh optical signal by the polarization rotating beam combiner.
According to an embodiment of the present disclosure, the intensity of the first optical signal and the intensity of the second optical signal are both half of the intensity of the optical signal. According to the embodiment of the disclosure, the optical polarization modulation method can be applied to the field of quantum key distribution.
According to an embodiment of the present disclosure, the first phase shifting arm may further include a third arm, and the second phase shifting arm may further include a fourth arm. The first support arm, the second support arm, the third support arm and the fourth support arm all comprise waveguide structures, wherein the first phase modulator and the second phase modulator are respectively arranged on the waveguide structures of the first support arm and the second support arm.
According to the embodiments of the present disclosure, the phase amplitudes of the first electrical modulation signal and the second electrical modulation signal are required to satisfy the working ranges of the corresponding phase modulators.
According to the embodiment of the present disclosure, an optical signal is transmitted to an optical splitter through an input waveguide, the optical splitter splits the input optical signal into a first optical signal and a second optical signal having half the intensity of the optical signal and the same other properties, and transmits the first optical signal and the second optical signal to a first phase shift arm, wherein the first optical signal is transmitted to a first arm of the first phase shift arm, and the second optical signal is transmitted through a third arm of the first phase shift arm. The first phase modulator on the first arm adjusts the phase of the first optical signal according to the received first electrical modulation signal, so as to generate a third optical signal, wherein the relative phase difference between the third optical signal and the second optical signal is determined by the phase of the first electrical modulation signal.
According to the embodiment of the disclosure, the first phase shift arm transmits the second optical signal and the third optical signal to the optical combiner, the optical combiner performs interference and beam combination processing on the second optical signal and the third optical signal, and the optical combiner generates the fourth optical signal and/or the fifth optical signal according to the relative phase difference.
According to an embodiment of the disclosure, the optical combiner sends the fourth optical signal to the second arm of the second phase shift arm, so that the second phase modulator loads an additional phase to the fourth optical signal according to the received second electrical modulation signal, generates a sixth optical signal, and/or the optical combiner transmits the fifth optical signal to the fourth arm of the second phase shift arm.
According to the embodiment of the disclosure, the polarization rotation beam combiner performs first angle rotation on the polarization state of the sixth optical signal transmitted by the second phase shift arm, and combines the sixth optical signal and/or the fifth optical signal after the angle rotation is performed on the polarization state to generate a seventh optical signal, where the seventh optical signal is an optical signal whose polarization state is adjusted. The first angle may comprise 90 degrees.
According to an embodiment of the present disclosure, the seventh optical signal is output through the output waveguide.
According to the embodiment of the disclosure, the relative strength and the relative phase of the fifth optical signal and the sixth optical signal in the second phase shift arm can be controlled by regulating and controlling the first modulation electric signal and the second modulation electric signal which drive the first phase modulator and the second phase modulator, so that the fifth optical signal and the sixth optical signal can obtain any polarization state on the bungar sphere through the processing of the polarization rotation beam combiner.
According to the embodiment of the disclosure, a first electrical modulation signal is loaded on a first optical signal through a first phase shift arm to generate a third optical signal, a beam combiner is used for processing a second optical signal and the third optical signal to generate a fourth optical signal and/or a fifth optical signal, a second phase shift arm is used for loading a second electrical modulation signal on the fourth optical signal to generate a sixth optical signal, a polarization rotation beam combiner is used for combining the fifth optical signal and/or the sixth optical signal into a seventh optical signal, and the requirement for the electrical modulation signal is reduced through the technical means of loading the electrical modulation signal twice, so that the imperfect characteristic caused by the high voltage requirement of the electrical modulation signal can be reduced, the technical problem that the requirement for the electrical modulation signal is high, the polarization state contrast obtained by modulation is poor is at least partially overcome, and the voltage of the electrical modulation signal is reduced, thereby reducing the imperfect characteristics and further improving the technical effect of the contrast of the polarization state.
Fig. 2 schematically illustrates a flow diagram for generating a fourth optical signal and/or a fifth optical signal according to an embodiment of the disclosure.
According to an embodiment of the present disclosure, the phase threshold includes a first phase threshold, a second phase threshold, and a third phase threshold.
Wherein, in case that the relative phase difference satisfies the phase threshold, processing the second optical signal and the third optical signal by using the optical beam combiner to generate a fourth optical signal and/or a fifth optical signal, may include operations S201 to S204.
In operation S201, the optical combiner generates an eighth optical signal according to the second optical signal and the third optical signal.
In operation S202, the eighth optical signal is processed with the optical beam combiner to generate a fourth optical signal if the relative phase difference satisfies the first phase threshold.
In operation S203, or in case the relative phase difference satisfies the second phase threshold, the eighth optical signal is processed with the optical beam combiner to generate a fifth optical signal.
In operation S204, or in case the relative phase difference satisfies the third phase threshold, the eighth optical signal is processed by the optical beam combiner to generate a fourth optical signal and a fifth optical signal.
According to an embodiment of the present disclosure, the first phase threshold may include 0. The second phase threshold may comprise pi. The third phase threshold may include (0, π) and (π, 2 π), where π may be 180 degrees.
According to the embodiment of the present disclosure, the optical combiner performs interference and beam combining processing on the second optical signal and the third optical signal to generate an eighth optical signal.
According to an embodiment of the present disclosure, in a case where the relative phase difference satisfies the first phase threshold, the optical combiner outputs (cos (θ/2))2Multiple fourth optical signal. Or, when the relative phase difference theta satisfies the second phase threshold, the fourth arm of the second phase shift arm is output (sin (theta/2))2Multiple fifth optical signal. Alternatively, the optical combiner generates the fourth optical signal and the fifth optical signal when the relative phase difference satisfies a third phase thresholdAnd transmitting the fourth optical signal and the fifth optical signal to the second supporting arm and the fourth supporting arm respectively through the first port and the second port of the optical beam combiner.
According to an embodiment of the present disclosure, a phase difference of the sixth optical signal and the fourth optical signal
Determined by formula (1);
wherein, V2Voltage, V, representing the second phase modulatorπ2Representing the half-wave voltage of the second phase modulator.
According to an embodiment of the present disclosure, the intensity of the fourth optical signal is (cos (θ/2))2The intensity of the fifth light signal is (sin (theta/2))2Multiple, θ characterizes the relative phase difference.
According to an embodiment of the present disclosure, the relative phase difference θ may be determined by a voltage V driving the first phase modulator1The decision is as shown in equation (2).
Wherein, Vπ1Representing the half-wave voltage of the first phase modulator.
According to embodiments of the present disclosure, the pattern of the optical signal may include TE0、TM0Or TM0nMode(s). Embodiments of the present disclosure relate to TE0For example.
According to the embodiment of the disclosure, the first optical signal and the second optical signal output by the optical beam splitter are TE with half intensity of the optical signal0Mode light. The first optical signal of the first arm in the first phase shift arm obtains an extra phase theta after passing through the first phase modulator, and the phase of the second optical signal of the third arm in the first phase shift arm is unchanged, so that the extra phase theta is obtained after passing through the third armAfter the first support arm and the third support arm are excessively equal in length, the relative phase difference between the second optical signal and the third optical signal in the first phase shift arm is theta, and the polarization modes are both TE0Mode(s).
The first phase modulator and the second phase modulator can select thermo-optic phase modulation, carrier injection modulation, carrier dissipation modulation, carrier accumulation modulation and the like to perform phase modulation and driving according to modulation requirements, and sources of the first electrical modulation signal and the second electrical modulation signal of the first phase modulator and the second phase modulator can comprise A Waveform Generator (AWG) or a Field Programmable Gate Array (FPGA) and the like.
The second optical signal and the third optical signal are coupled into the second phase shift arm through an optical combiner, wherein the optical combiner may be a four-port 50: 50 coupler, and complex amplitudes of the fourth optical signal and the fifth optical signal, which are subjected to interference and beam combination processing by the optical combiner and output, are sum and difference of complex amplitudes of the input second optical signal and the third optical signal, respectively.
When the relative phase difference theta satisfies a first phase threshold, the optical combiner outputs (cos (theta/2))2Multiple fourth optical signal. Or, when the relative phase difference theta satisfies the second phase threshold, the fourth arm of the second phase shift arm is output (sin (theta/2))2Multiple fifth optical signal. Or, in the case that the relative phase difference satisfies the third phase threshold, the optical combiner generates a fourth optical signal and a fifth optical signal, and transmits the fourth optical signal and the fifth optical signal to the second arm and the fourth arm through the first port and the second port of the optical combiner, respectively, where the polarization modes of the fourth optical signal and the fifth optical signal are both TE0And the phase difference between the fourth optical signal and the fifth optical signal is 0.
The fourth optical signal of the second support arm in the second phase shift arm obtains an extra phase after passing through the second phase modulator
Phase position
By a voltage V driving the second phase modulator2It is determined that the phase difference between the fifth optical signal and the sixth optical signal in the second phase shift arm after passing through the second arm and the fourth arm having equal length is
All polarization modes are TE0Mode(s).
The polarization rotation beam combiner keeps the original polarization state TE of the sixth optical signal output by the second support arm in the second phase shift arm0The polarization state of the fifth optical signal output by the fourth support arm in the second phase shift arm is changed from TE0Conversion to TM0And combining the processed fifth optical signal and the sixth optical signal into a seventh optical signal, and finally outputting the seventh optical signal through the output waveguide, wherein the polarization mode of the seventh optical signal can be represented by formula (3).
According to the embodiment of the disclosure, the first modulation electric signal and the second modulation electric signal for driving the first phase modulator and the second phase modulator can be regulated and controlled according to the polarization mode which is required to be obtained, so that [0, 2 pi ] can be obtained]Arbitrary relative phase difference theta, phase difference
Further, any polarization state on the Ponga spherical surface can be obtained.
According to the embodiment of the disclosure, in the application of the quantum key distribution field, taking the polarization-encoded BB84 protocol as an example, a transmitting end needs to modulate two pairs of mutually orthogonal polarization states that are unbiased as Z and X basis vectors, where a basis vector refers to a group of basic quantum states that can form a polarization-state hilbert space in quantum mechanics.
When the light polarization is adjustedWhen the method is used for polarization coding of a quantum key transmitting end, the first electrical modulation signal and the second electrical modulation signal are required to respectively correspond to voltages (0, 0) and (V)π1，0)、(Vπ1[ 2, 0 ] and (V)π1/2，Vπ2) At this time, the corresponding polarization states of the correspondingly output eighth optical signal are respectively:
wherein TE0And TM0The two polarization modes are orthogonal to each other and can be used as a Z basis vector of polarization encoding;
and
the two polarization modes are orthogonal to each other and can be used as X basis vector of polarization coding.
The Z-basis vector and the X-basis vector obtained by the optical polarization modulation method have the characteristic of being unbiased mutually, so that the obtained four polarization states can be used as four BB84 quantum states of a polarization encoding BB84 protocol.
Meanwhile, in the optical polarization modulation process, four high-contrast BB84 quantum states can be obtained only by phase modulation with the highest pi and using the first electric modulation signal and the second electric modulation signal which are not higher than half-wave voltages of the first phase modulator and the second phase modulator respectively. Therefore, the optical polarization modulation method reduces the requirement on the electric modulation signal, avoids imperfect characteristics such as saturation and the like of the modulation module along with the increase of the voltage, and can improve the polarization state contrast ratio finally obtained.
Fig. 3 schematically illustrates a structural schematic diagram of an optical polarization modulation module according to an embodiment of the present disclosure.
As shown in fig. 3, another aspect of the embodiments of the present disclosure provides an optical polarization modulation module, which may include an optical beam splitter 310, a first phase shift arm 320, a second phase shift arm 330, a polarization rotation beam combiner 340, and an optical beam combiner 350.
The optical splitter 310 is configured to split the optical signal into a first optical signal and a second optical signal.
The first phase shift arm 320, the first phase shift arm 320 includes a first arm 321 and a third arm 323, the first arm 321 is provided with a first phase modulator 322, an input end of the first arm 321 and an input end of the third arm 323 are both connected to an output end of the optical splitter 310, the first arm 321 is configured to obtain a first electrical modulation signal and adjust a phase of the first optical signal according to the first electrical modulation signal to obtain a third optical signal, and the third arm 323 is configured to transmit a second optical signal, where a relative phase difference exists between the third optical signal and the second optical signal.
And the optical combiner 350, where an output end of the first arm 321 and an output end of the third arm 323 are both connected to an input end of the optical combiner 350, and the optical combiner 350 is configured to process the second optical signal and the third optical signal by using the optical combiner 350 to generate a fourth optical signal and/or a fifth optical signal when the relative phase difference satisfies a phase threshold.
The second phase shift arm 330, the second phase shift arm 330 includes a second support arm 331 and a fourth support arm 333, the second support arm 331 is provided with a second phase modulator 332, an input end of the second support arm 331 and an input end of the fourth support arm 333 are both connected to an output end of the optical combiner 350, the second support arm 331 is configured to obtain a second electrical modulation signal, and perform phase adjustment on the fourth optical signal according to the second electrical modulation signal to generate a sixth optical signal, and the fourth support arm 333 is configured to transmit a fifth optical signal.
The output end of the second arm 331 and the output end of the fourth arm 333 of the polarization rotation beam combiner 340 are both connected to the input end of the polarization rotation beam combiner 340, and the polarization rotation beam combiner 340 is configured to combine the fifth optical signal and/or the sixth optical signal into a seventh optical signal.
According to the embodiment of the present disclosure, a first electrical modulation signal is loaded on a first optical signal by a first phase shift arm 320 to generate a third optical signal, a beam combiner is used to process a second optical signal and the third optical signal to generate a fourth optical signal and/or a fifth optical signal, a second phase shift arm 330 is used to load a second electrical modulation signal on the fourth optical signal to generate a sixth optical signal, a polarization rotation beam combiner 340 is used to combine the fifth optical signal and/or the sixth optical signal into a seventh optical signal, and by means of a technical means of loading an electrical modulation signal twice, requirements on the electrical modulation signal are reduced, so that an imperfect characteristic caused by a high voltage requirement on the electrical modulation signal can be reduced, so that a technical problem that the requirement on the electrical modulation signal is high and a polarization state contrast obtained by modulation is poor is at least partially overcome, and a voltage of the electrical modulation signal is reduced, thereby reducing the imperfect characteristics and further improving the technical effect of the contrast of the polarization state. Meanwhile, the structure of the light polarization modulation module is simpler, the number of required integrated devices is less, and the design and production difficulty of the light polarization modulation module can be effectively reduced.
According to embodiments of the present disclosure, the optical polarization modulation module may further include an input waveguide and/or an output waveguide.
And an output end of the input waveguide is connected with an input end of the optical splitter 310, and the input waveguide is used for acquiring an optical signal.
And an input end of the output waveguide is connected with an output end of the polarization rotation beam combiner 340, and the output waveguide is used for outputting the sixth optical signal.
According to an embodiment of the present disclosure, the optical splitter 310 may be one of a coupler, a Y-type beam splitter, a multimode interferometer type beam splitter, and a directional coupler type beam splitter.
The beam combiner 350 may be one of a coupler, a multimode interferometer type beam combiner, and a directional coupling type beam combiner.
According to an embodiment of the present disclosure, the number of the second phase shifting arms 330 is at least one.
Another aspect of the embodiments of the present disclosure provides an optical chip, which may include the optical polarization modulation module as described above.
According to the embodiment of the present disclosure, a first electrical modulation signal is loaded on a first optical signal by a first phase shift arm 320 to generate a third optical signal, a beam combiner is used to process a second optical signal and the third optical signal to generate a fourth optical signal and/or a fifth optical signal, a second phase shift arm 330 is used to load a second electrical modulation signal on the fourth optical signal to generate a sixth optical signal, a polarization rotation beam combiner 340 is used to combine the fifth optical signal and/or the sixth optical signal into a seventh optical signal, and by means of a technical means of loading an electrical modulation signal twice, requirements on the electrical modulation signal are reduced, so that an imperfect characteristic caused by a high voltage requirement on the electrical modulation signal can be reduced, so that a technical problem that the requirement on the electrical modulation signal is high and a polarization state contrast obtained by modulation is poor is at least partially overcome, and a voltage of the electrical modulation signal is reduced, thereby reducing the imperfect characteristics and further improving the technical effect of the contrast of the polarization state. Meanwhile, the used light polarization modulation module has a simple structure and fewer integrated devices, so that the optical chip has the characteristic of miniaturization, the cost of the optical chip is reduced, and the light polarization modulation module is suitable for miniaturization and large-scale production of the optical chip.
The embodiments of the present disclosure have been described above. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although the embodiments are described separately above, this does not mean that the measures in the embodiments cannot be used in advantageous combination. The scope of the disclosure is defined by the appended claims and equivalents thereof. Various alternatives and modifications can be devised by those skilled in the art without departing from the scope of the present disclosure, and such alternatives and modifications are intended to be within the scope of the present disclosure.
Claims (10)
1. A method of modulating light polarization, comprising:
splitting the optical signal into a first optical signal and a second optical signal by an optical splitter;
according to a first electrical modulation signal, adjusting the phase of the first optical signal by using a first arm of a first phase shift arm to obtain a third optical signal, wherein a relative phase difference exists between the third optical signal and the second optical signal, and the first arm of the first phase shift arm is provided with a first phase modulator;
processing the second optical signal and the third optical signal with an optical beam combiner to generate a fourth optical signal and/or a fifth optical signal if the relative phase difference satisfies a phase threshold;
adjusting the fourth optical signal with a second arm of a second phase shift arm to generate a sixth optical signal according to a second electrical modulation signal, wherein an upper arm of the second phase shift arm is provided with a second phase modulator; and
and combining the fifth optical signal and/or the sixth optical signal into a seventh optical signal by a polarization rotating beam combiner.
2. The method of claim 1, wherein the intensity of the first and second optical signals is each half of the intensity of the optical signal.
3. The method of claim 1, the phase threshold comprising a first phase threshold, a second phase threshold, and a third phase threshold;
wherein the processing, with the optical beam combiner, the second optical signal and the third optical signal to generate a fourth optical signal and/or a fifth optical signal if the relative phase difference satisfies a phase threshold comprises:
the optical beam combiner generates an eighth optical signal according to the second optical signal and the third optical signal;
processing, with the optical beam combiner, the eighth optical signal to generate the fourth optical signal if the relative phase difference satisfies the first phase threshold; or
Processing the eighth optical signal with the optical beam combiner to generate the fifth optical signal if the relative phase difference satisfies the second phase threshold; or
Processing, by the optical beam combiner, the eighth optical signal to generate the fourth optical signal and the fifth optical signal when the relative phase difference satisfies the third phase threshold.
4. The method of claim 3, wherein the fourth optical signal has an intensity of the eighth optical signalOf intensity (cos (theta/2))2A fifth optical signal having an intensity (sin (θ/2))2Multiple, θ characterizes the relative phase difference.
5. The method of claim 1, wherein the sixth optical signal is out of phase with the fourth optical signal
Determined by formula (1);
wherein, V2Voltage, V, representing the second phase modulatorπ2Representing the half-wave voltage of the second phase modulator.
6. An optical polarization modulation module comprising:
an optical splitter for splitting an optical signal into a first optical signal and a second optical signal;
the optical fiber coupler comprises a first phase shift arm, a second phase shift arm and a third phase shift arm, wherein the first phase shift arm comprises a first support arm and a third support arm, a first phase modulator is arranged on the first support arm, the input end of the first support arm and the input end of the third support arm are both connected with the output end of an optical splitter, the first support arm is used for acquiring a first electrical modulation signal and adjusting the phase of the first optical signal according to the first electrical modulation signal to acquire a third optical signal, the third support arm is used for transmitting the second optical signal, and a relative phase difference exists between the third optical signal and the second optical signal;
the output end of the first support arm and the output end of the third support arm are both connected with the input end of the optical combiner, and the optical combiner is used for processing the second optical signal and the third optical signal by using the optical combiner to generate a fourth optical signal and/or a fifth optical signal under the condition that the relative phase difference meets a phase threshold;
the second phase shift arm comprises a second support arm and a fourth support arm, a second phase modulator is arranged on the second support arm, the input end of the second support arm and the input end of the fourth support arm are both connected with the output end of the optical beam combiner, the second support arm is used for acquiring a second electrical modulation signal and carrying out phase adjustment on the fourth optical signal according to the second electrical modulation signal so as to generate a sixth optical signal, and the fourth support arm is used for transmitting the fifth optical signal; and
and the output end of the second support arm and the output end of the fourth support arm are both connected with the input end of the polarization rotation beam combiner, and the polarization rotation beam combiner is used for combining the fifth optical signal and/or the sixth optical signal into a seventh optical signal.
7. The light polarization modulation module of claim 6, further comprising:
an output end of the input waveguide is connected with an input end of the optical splitter, and the input waveguide is used for acquiring the optical signal; and/or
And the input end of the output waveguide is connected with the output end of the polarization rotation beam combiner, and the output waveguide is used for outputting the seventh optical signal.
8. A light polarization modulation module according to any one of claims 6 to 7,
the optical beam splitter is one of a coupler, a Y-shaped beam splitter, a multimode interferometer type beam splitter and a directional coupler type beam splitter; and/or
The optical beam combiner is one of a coupler, a multimode interferometer type beam combiner and a directional coupling type beam combiner.
9. The light polarization modulation module of claim 6, wherein the second phase shifting arm is at least one in number.
10. An optical chip, comprising: a light polarization modulation module according to any one of claims 6 to 9.
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