CN115015946A - Photoelectric hybrid frequency mixing device, coherent ranging system and method thereof - Google Patents
Photoelectric hybrid frequency mixing device, coherent ranging system and method thereof Download PDFInfo
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- CN115015946A CN115015946A CN202110237068.1A CN202110237068A CN115015946A CN 115015946 A CN115015946 A CN 115015946A CN 202110237068 A CN202110237068 A CN 202110237068A CN 115015946 A CN115015946 A CN 115015946A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
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- G—PHYSICS
- G02—OPTICS
- 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
- G02F1/00—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
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
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Abstract
The invention discloses a photoelectric mixed frequency mixing device, a coherent ranging system and a method thereof, wherein the device comprises: the phase modulation unit modulates the first optical signal to obtain a first modulated optical signal; the 2 × 2 power splitter mixes the second optical signal and the first modulated optical signal, and the two ports output a third optical signal and a fifth optical signal respectively at a low level and output a fourth optical signal and a sixth optical signal respectively at a high level, wherein a phase difference between two signal components included in each optical signal in the third optical signal and the fourth optical signal is-90 degrees, and a phase difference between two signal components included in each optical signal in the fifth optical signal and the sixth optical signal is 90 degrees. By implementing the invention, the phase modulation unit is introduced to modulate the optical signal, and the frequency mixing function of the existing 2 x 4 multimode interference coupler can be realized by subsequently adopting a 2 x 2 power beam splitter, thereby simplifying the structure of the frequency mixer.
Description
Technical Field
The invention relates to the technical field of coherent detection, in particular to a photoelectric hybrid frequency mixing device, a coherent ranging system and a coherent ranging method.
Background
In recent years, with the popularization of unmanned technology, laser ranging systems play an irreplaceable important role therein. Compared with a direct detection system, a coherent detection system has more excellent performances in the aspects of detection capability, conversion gain, signal-to-noise ratio, stability and the like, so that the coherent detection system is widely applied to laser detection devices.
Mixers, especially 90 ° mixing devices, are critical components in coherent detection systems, and their performance and size have a significant impact on the performance of coherent detection systems.
The conventional 90 ° mixer implementation scheme mainly includes a bulk optical scheme and an integrated chip scheme, wherein the integrated optical scheme is mostly based on a 2 × 4 Multimode interference coupler (MMI) design, which results in a complex structure, a large area and a complex signal analysis method for a single detection unit. The mixer is not beneficial to the application and the integration development of the mixer in a coherent system.
Disclosure of Invention
In view of this, embodiments of the present invention provide an optical-electrical hybrid mixer, a coherent ranging system, and a method thereof, so as to solve the technical problem of complex structure of the existing mixer design scheme.
In a first aspect of an embodiment of the present invention, an optical-electrical hybrid mixing apparatus includes: the phase modulation unit is used for receiving a first optical signal, and obtaining a first modulated optical signal after performing periodic phase modulation on the first optical signal; the 2 × 2 power splitter is configured to receive a second optical signal and the first modulated optical signal, mix the second optical signal with the first modulated optical signal, the first port of the 2 × 2 power splitter outputs a third optical signal and the second port of the 2 × 2 power splitter outputs a fifth optical signal for a low level duration, the first port of the 2 × 2 power splitter outputs a fourth optical signal and the second port of the 2 × 2 power splitter outputs a sixth optical signal for a high level duration, the third optical signal, the fourth optical signal, the fifth optical signal, and the sixth optical signal each include the mixed first modulated optical signal and the mixed second optical signal, a phase difference between the mixed first modulated optical signal and the mixed second optical signal is-90 degrees in the third optical signal and the mixed fourth optical signal, and the mixed first modulated optical signal and the mixed second optical signal are in the fifth optical signal and the mixed sixth optical signal, the phase difference between the mixed first modulated optical signal and the second optical signal is 90 degrees.
Optionally, the optoelectronic hybrid mixing apparatus further includes: the first detection unit is used for receiving the third optical signal and the fourth optical signal and respectively converting the third optical signal and the fourth optical signal into a third electric signal and a fourth electric signal; the second detection unit is configured to receive the fifth optical signal and the sixth optical signal, and convert the fifth optical signal and the sixth optical signal into a fifth electrical signal and a sixth electrical signal, respectively.
Optionally, the third optical signal and the fourth optical signal are-90 ° and 180 ° in phase, respectively, and the fifth optical signal and the sixth optical signal are 90 ° and 0 ° in phase, respectively.
Optionally, the 2 × 2 power splitter includes any one of a 2 × 2 multimode interference coupler, a 2 × 2 directional coupler, a ring cavity coupler, a star coupler, a slab waveguide-based fresnel lens array, a slab waveguide-based superlens array, and a half-mirror.
Optionally, the modulation mechanism of the phase modulation unit includes: photoelectric effect, elasto-optical effect, magneto-optical effect, and phase change effect.
Optionally, the optoelectronic hybrid mixing apparatus further includes: and the attenuation unit is used for attenuating the optical signal output by the 2 × 2 power beam splitter, so that the power of the attenuated third optical signal is equal to that of the attenuated fifth optical signal, and the power of the attenuated fourth optical signal is equal to that of the attenuated sixth optical signal.
A second aspect of an embodiment of the present invention provides a coherent ranging system, including: the optical-electrical hybrid mixing apparatus includes a signal generation module, a data processing module, and the optical-electrical hybrid mixing apparatus according to any one of the first aspect and the first aspect of the embodiments of the present invention, where the signal generation module is configured to output a first optical signal and a first detection signal; the photoelectric hybrid frequency mixing device is used for receiving the first optical signal and a second optical signal which is reflected by a target to be detected and detected from the first detection signal, and modulating, mixing and detecting the first optical signal and the second optical signal to obtain a third electric signal, a fourth electric signal, a fifth electric signal and a sixth electric signal; and the data processing module is used for processing and calculating the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal to obtain the distance information of the target to be detected.
Optionally, the signal generating module includes: the laser device comprises a light-emitting unit, a beam splitting unit and a light receiving and transmitting unit, wherein the light-emitting unit is used for outputting laser signals; the beam splitting unit is used for splitting the laser signal to obtain a first optical signal and a second detection signal;
the optical transceiver unit is used for transmitting the first detection signal to a target to be detected in a collimation manner, and receiving and outputting a second optical signal reflected by the target to be detected.
Optionally, the data processing module includes: the differential amplification unit is used for carrying out differential amplification on the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal and then outputting the signals; the Fourier unit is used for calculating the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal after differential amplification to obtain the distance information of the target to be detected.
A third aspect of the embodiments of the present invention provides a coherent ranging method, including: dividing a laser signal output by a light-emitting unit into a first optical signal and a first detection signal, wherein the first detection signal is irradiated on a target to be detected and reflected to obtain a second optical signal; after the first optical signal or the second optical signal is subjected to phase modulation, mixing the first optical signal or the second optical signal with an optical signal which is not subjected to phase modulation to obtain a third optical signal and a fifth optical signal which have low level duration and a fourth optical signal and a sixth optical signal which have high level duration, wherein the third optical signal, the fourth optical signal, the fifth optical signal and the sixth optical signal all comprise the first modulated optical signal and the second optical signal which are subjected to frequency mixing, in the third optical signal and the fourth optical signal, the phase difference between the first modulated optical signal and the second optical signal which are subjected to frequency mixing is-90 degrees, and in the fifth optical signal and the sixth optical signal, the phase difference between the first modulated optical signal and the second optical signal which are subjected to frequency mixing is 90 degrees; respectively converting the third optical signal, the fourth optical signal, the fifth optical signal and the sixth optical signal through the first detection unit and the second detection unit to obtain a third electrical signal, a fourth electrical signal, a fifth electrical signal and a sixth electrical signal; and processing and calculating the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal to obtain the distance information of the target to be detected.
The technical scheme of the invention has the following advantages:
according to the photoelectric hybrid frequency mixing device provided by the embodiment of the invention, the phase modulation unit is introduced to perform periodic phase modulation on an optical signal, and a 2 × 2 power beam splitter is subsequently adopted, so that the frequency mixing device can realize the frequency mixing function of the existing 2 × 4 multimode interference coupler, thereby simplifying the structure of the frequency mixer and reducing the size of the frequency mixer.
According to the coherent ranging system provided by the embodiment of the invention, the photoelectric mixed type mixing device is adopted to realize mixing, and compared with the existing mixer for mixing, the structure of the mixer is simplified, and the size of the mixer is reduced. In addition, the system is provided with a signal generating module and a data processing module, and the detection of the distance of the target to be detected is realized by processing and calculating the reflected signal of the target to be detected.
In the coherent ranging method provided in the embodiment of the present invention, when mixing the first optical signal and the second optical signal, the first optical signal or the second optical signal is subjected to periodic phase modulation, and then the modulated optical signal is mixed with the unmodulated optical signal, so that the size of the mixer used can be reduced. Meanwhile, the coherent ranging method can obtain the distance information of the target to be detected by processing and calculating the electrical signal after detection and conversion by adopting a Fourier method.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a block diagram of an opto-electric hybrid mixer according to an embodiment of the present invention;
FIG. 2 is a block diagram of an optoelectronic hybrid mixer according to another embodiment of the present invention;
FIG. 3 is a block diagram of an optoelectronic hybrid mixer according to another embodiment of the present invention;
FIG. 4 is a block diagram of a coherent detection system according to an embodiment of the present invention;
FIG. 5 is a block diagram of a coherent detection system in accordance with another embodiment of the present invention;
FIG. 6 is a flowchart illustrating a coherent ranging method according to an embodiment of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be connected through the inside of the two elements, or may be connected wirelessly or through a wire. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
An embodiment of the present invention provides an optical-electrical hybrid mixing apparatus, as shown in fig. 1, the apparatus includes: the optical fiber signal processing device comprises a phase modulation unit 101 and a 2 x 2 power beam splitter 102, wherein the phase modulation unit 101 is used for receiving a first optical signal and performing periodic phase modulation on the first optical signal to obtain a first modulated optical signal; the 2 x 2 power splitter is configured to receive the second optical signal and the first modulated optical signal, mix the second optical signal and the first modulated optical signal, during the low level duration, the first port of the 2 x 2 power splitter outputs a third optical signal, the second port of the 2 x 2 power splitter outputs a fifth optical signal, during the high level duration, the first port of the 2 × 2 power splitter outputs a fourth optical signal, the second port of the 2 × 2 power splitter outputs a sixth optical signal, the third optical signal, the fourth optical signal, the fifth optical signal and the sixth optical signal all include the first modulated optical signal and the second optical signal after frequency mixing, in the third optical signal and the fourth optical signal, the phase difference between the mixed first modulated optical signal and the second optical signal is-90 degrees, in the fifth optical signal and the sixth optical signal, a phase difference between the mixed first modulated optical signal and the second optical signal is 90 degrees.
According to the photoelectric hybrid frequency mixing device provided by the embodiment of the invention, the phase modulation unit 101 is introduced to perform periodic phase modulation on an optical signal, and a 2 × 2 power beam splitter 102 is subsequently adopted, so that the frequency mixing device can realize the frequency mixing function of the existing 2 × 4 multimode interference coupler, thereby simplifying the structure of the frequency mixer and reducing the size of the frequency mixer.
It should be noted that, when the existing 2 × 4 multimode interference coupler is used in a coherent detection system, four output signals after mixing by the 2 × 4 multimode interference coupler are subjected to differential amplification and orthogonal synthesis respectively. The 2 × 2 power splitter in the opto-electric hybrid mixing device can realize the same function as the 2 × 4 multimode interference coupler, and specifically, the 2 × 2 power splitter performs quadrature synthesis after differential amplification on four optical signals within the high and low level durations respectively, so that the opto-electric hybrid mixing device provided by the embodiment of the invention simplifies the mixing structure, reduces the size of the mixer, and ensures the consistency of the mixing function with the 2 × 4 multimode interference coupler in the mixing function.
In an embodiment, the modulation mechanism of the phase modulation unit 101 includes: photoelectric effect, elasto-optical effect, magneto-optical effect, and phase change effect. In a specific embodiment, the modulation principle of the phase modulation unit 101 is described by taking the photoelectric effect as an example. Specifically, the phase modulation unit 101 may employ a phase shifter, and when the frequency mixing device works, a voltage of a first preset value is applied to the phase shifter, so that an optical signal passing through the phase shifter is shifted; meanwhile, a voltage with a second preset value can be added to the phase shifter, so that the optical signal passing through the phase shifter does not generate phase shift. Thus, when the phase shifter is used in the frequency mixing apparatus, as shown in fig. 2, a voltage of the first preset value and a voltage of the second preset value may be applied to the phase shifter in the form of a square wave, so that the optical signal modulated by the phase shifter generates a 90 ° phase-shifted or non-phase-shifted signal having the same period as the applied square wave.
In an embodiment, after the first modulated optical signal and the second optical signal enter the 2 × 2 power splitter 102, the light beams are combined and then split at the output end to obtain two optical signals. Specifically, since the first modulated optical signal is periodic, the two optical signals output by the 2 × 2 power splitter 102 are also two sets of signals arranged according to the periodicity, i.e., the third optical signal and the fifth optical signal respectively output by the two output ports of the 2 x 2 power splitter 102 during the low level duration, during the high level duration, the fourth optical signal and the sixth optical signal respectively output by the two output ports of the 2 × 2 power splitter 102, wherein the third optical signal, the fourth optical signal, the fifth optical signal and the sixth optical signal all comprise the first modulated optical signal and the second optical signal after frequency mixing, in the third optical signal and the fourth optical signal, the phase difference between the mixed first modulated optical signal and the second optical signal is-90 degrees, in the fifth optical signal and the sixth optical signal, a phase difference between the mixed first modulated optical signal and the second optical signal is 90 degrees.
Specifically, as shown in fig. 2, the second optical signal is represented by Sig, the first optical signal is represented by Lo, the first modulated optical signal and the second optical signal are mixed by the 2 × 2 power splitter, and the third optical signal and the fourth optical signal output from the first port of the 2 × 2 power splitter are represented by Sig exp (i0) + Lo exp (i90) and Sig exp (i0) + Lo exp (i180), respectively, wherein, during the high-level duration time, the first modulated optical signal is obtained by generating a phase shift of 90 degrees by passing the first optical signal through the phase modulation unit, that is, Lo in the signal component Lo exp (i180) included in the fourth optical signal has a phase of 90 degrees, so that the phase difference between the first modulated optical signal and the second optical signal, that are mixed, between the two signal components included in the third optical signal and the fourth optical signal is equal to the phase difference between the first modulated optical signal and the second optical signal, and the third optical signal itself may have the phase difference of 90 degrees, and the third optical signal itself may have the phase difference between the two signal components included in the third optical signal and the fourth optical signal itself The phases of the third optical signal and the fourth optical signal are found to be-90 ° and 180 °, respectively.
Meanwhile, after the first modulated optical signal and the second optical signal are mixed by the 2 × 2 power splitter, the fifth optical signal and the sixth optical signal output from the second port of the 2 × 2 power splitter are represented as Sig × exp (i90) + Lo × exp (i0) and Sig × exp (i90) + Lo × exp (i90), respectively. Similarly, in the high level duration, since the first optical signal is shifted by 90 degrees by the phase modulation unit, the first modulated optical signal is obtained, that is, Lo in the signal component Lo × exp (i180) included in the sixth optical signal has a phase of 90 degrees, and thus, the phase difference between the two signal components included in the fifth optical signal and the sixth optical signal, that is, between the first modulated optical signal and the second optical signal after mixing is 90 degrees, and meanwhile, since the two signal components included in the fifth optical signal and the sixth optical signal have their own phases, the phases of the fifth optical signal and the sixth optical signal are 90 ° and 0 °, respectively.
In one embodiment, the 2 × 2 power splitter 102 may select any one of a 2 × 2 multimode interference coupler, a 2 × 2 directional coupler, a ring cavity coupler, a star coupler, a slab waveguide-based fresnel lens array, a slab waveguide-based superlens array, and a half mirror.
In an embodiment, to facilitate the signal analysis, as shown in fig. 3, the optical-electrical hybrid mixing apparatus further includes: the first detection unit 103 is used for receiving the third optical signal and the fourth optical signal, and converting the third optical signal and the fourth optical signal into a third electrical signal and a fourth electrical signal, respectively; the second detection unit 104 is configured to receive the fifth optical signal and the sixth optical signal, and convert the fifth optical signal and the sixth optical signal into a fifth electrical signal and a sixth electrical signal, respectively. In a specific embodiment, the first detection unit 103 and the second detection unit 104 can be respectively selected from photodetectors, such as any one of a single photon avalanche diode, an avalanche photodiode, a silicon photomultiplier, or a PIN photodiode. In an embodiment, the maximum detectable bandwidth of the first detecting unit 103 and the second detecting unit 104 may be smaller than the signal frequency of the square wave loaded on the phase modulating unit 101, so as to prevent two detecting units from being unable to detect four optical signals.
In an embodiment, in order to make the subsequent processing of the signal simpler, the hybrid optical/electrical mixing apparatus further includes: and the attenuation unit is used for attenuating the optical signal output by the 2 x 2 power beam splitter, so that the power of the attenuated third optical signal is equal to that of the fifth optical signal, and the power of the fourth optical signal is equal to that of the sixth optical signal. In a specific embodiment, the attenuation unit includes an optical attenuator, and specifically, the optical signal with higher power may be input to the optical attenuator according to the power of the third optical signal and the power of the fifth optical signal; for example, if the power of the third optical signal is greater than that of the fifth optical signal, an optical attenuator is disposed on the optical path where the third optical signal is located, so that the power of the attenuated third optical signal is equal to that of the unattenuated fifth optical signal. In addition, optical attenuators may be disposed on optical paths of the two output ports of the 2 × 2 power splitter, so that the attenuated optical signal powers are equal.
An embodiment of the present invention further provides a relative distance measuring system, as shown in fig. 4, the system includes: a signal generating module 201, a data processing module 203, and the hybrid optical/electrical mixing apparatus 202 according to the above embodiment, where the signal generating module 201 is configured to output a first optical signal and a first detection signal; the photoelectric hybrid frequency mixing device 202 is configured to receive a first optical signal and a second optical signal of a first detection signal reflected by a target to be detected, and modulate, frequency mix and detect the first optical signal and the second optical signal to obtain a third electrical signal, a fourth electrical signal, a fifth electrical signal and a sixth electrical signal; the data processing module 203 is configured to process and calculate the third electrical signal, the fourth electrical signal, the fifth electrical signal, and the sixth electrical signal to obtain distance information of the target to be detected.
In the coherent ranging system provided by the embodiment of the present invention, the above-mentioned optical-electrical hybrid mixer 202 is used to realize frequency mixing, which simplifies the structure of the mixer and reduces the size of the mixer compared with the existing mixer. In addition, the system is provided with a signal generating module 201 and a data processing module 203, and the detection of the distance to the target to be detected is realized through the processing and calculation of the reflected signal of the target to be detected.
In an embodiment, when the optical-electrical hybrid mixing apparatus 202 modulates, mixes and detects the first optical signal and the second optical signal, the first optical signal, i.e. the local oscillator light or the reference light, may be input to the phase modulation unit 101 for modulation, and then the modulated first optical signal and the second optical signal that is not modulated are input to the 2 × 2 power splitter 102 for mixing. In an embodiment, the second optical signal, i.e. the signal light, may also be input to the phase modulation unit 101 for modulation, and then the modulated second optical signal and the unmodulated first optical signal are input to the 2 × 2 power splitter 102 for mixing.
In one embodiment, as shown in fig. 5, the signal generating module 201 includes: a light emitting unit 21, a beam splitting unit 22 and a light transceiving unit 23, wherein the light emitting unit 21 is used for outputting laser signals; the beam splitting unit 22 is configured to split the laser signal to obtain a first optical signal and a first detection signal; the optical transceiver unit 23 is configured to collimate and transmit the first detection signal to the target to be detected, and receive and output a second optical signal reflected by the target to be detected. In a specific embodiment, the light emitting unit 21 may select a laser, and the light emitted from the light emitting unit 21 may be modulated by frequency modulation or amplitude chirp modulation before being input to the beam splitting unit 22. The beam splitting unit 22 may be a beam splitter, and the optical transceiving unit 23 may be an optical element such as a lens to perform a corresponding function.
In one embodiment, as shown in fig. 5, the data processing module 203 includes: the differential amplifying unit 24 is configured to differentially amplify the third electrical signal, the fourth electrical signal, the fifth electrical signal and the sixth electrical signal and output the amplified signals; the fourier unit 25 is configured to calculate the third electrical signal, the fourth electrical signal, the fifth electrical signal, and the sixth electrical signal after differential amplification, so as to obtain distance information of the target to be detected.
In one embodiment, as shown in fig. 5, the coherent ranging system may operate according to the following process: the light emitting unit 21 emits a laser signal to the beam splitting unit 22, the beam splitting unit 22 splits the laser signal into a first optical signal and a first detection signal, the optical transceiver unit 23 collimates the first detection signal and then emits the first detection signal to a target to be detected, and receives a second optical signal reflected by the target to be detected and outputs the second optical signal to the 2 × 2 power beam splitter 102, the phase modulation unit 101 performs phase modulation on the first optical signal to obtain a first modulated optical signal and outputs the first modulated optical signal to the 2 × 2 power beam splitter 102, the 2 × 2 power beam splitter 102 performs frequency mixing on the first modulated optical signal and the second optical signal and then outputs a third optical signal and a fourth optical signal at a first port and outputs a fifth optical signal and a sixth optical signal at a second port, the first detection unit 103 and the second detection unit 104 perform detection conversion on the third optical signal and the fourth optical signal, and the fifth optical signal and the sixth optical signal respectively to obtain a third electrical signal, a fourth electrical signal, a fifth electrical signal and a sixth electrical signal, the differential amplification unit 24 performs differential amplification on the third electrical signal and the fourth electrical signal, and the fifth electrical signal and the sixth electrical signal, and then inputs the signals to the fourier unit 25 for calculation to obtain distance information of the target to be detected.
An embodiment of the present invention further provides a coherent ranging method, as shown in fig. 6, the coherent ranging method includes the following steps:
step S101: dividing a laser signal output by a light-emitting unit into a first optical signal and a first detection signal, wherein the first detection signal is irradiated on a target to be detected and reflected to obtain a second optical signal; optionally, the light emitting unit comprises a laser; a beam splitter may be employed to split the laser signal output by the light emitting unit into a first optical signal and a first detection signal; the optical transceiver unit is used for collimating the first detection signal and then transmitting the first detection signal to a target to be detected, and meanwhile, the optical transceiver unit can also receive and output a second optical signal reflected by the target to be detected.
Step S102: after the first optical signal or the second optical signal is subjected to phase modulation, the first optical signal or the second optical signal is mixed with an optical signal which is not subjected to phase modulation to obtain a third optical signal and a fifth optical signal with low level duration and a fourth optical signal and a sixth optical signal with high level duration.
In an embodiment, the first optical signal, i.e., the local oscillator light or the reference light, may be input to the phase modulation unit for modulation, and then the modulated first optical signal and the unmodulated second optical signal may be input to the 2 × 2 power splitter for mixing. In this case, the third optical signal, the fourth optical signal, the fifth optical signal, and the sixth optical signal each include the mixed first modulated optical signal and the mixed second optical signal, and the phase difference between the mixed first modulated optical signal and the mixed second optical signal is-90 degrees in the third optical signal and the fourth optical signal, and the phase difference between the mixed first modulated optical signal and the mixed second optical signal is 90 degrees in the fifth optical signal and the sixth optical signal. In an embodiment, the second optical signal, i.e. the signal light, may also be input to the phase modulation unit for modulation, and then the modulated second optical signal and the unmodulated first optical signal are input to the 2 × 2 power splitter for mixing.
In one embodiment, the square wave signal may be loaded on the phase modulation unit, so that the optical signal modulated by the phase modulation unit has a 90 ° phase shift or no phase shift. Thus, the phases of the third optical signal and the fourth optical signal output by the 2 × 2 power splitter are also periodically changed, that is, the third optical signal and the fifth optical signal output by the two output ports of the 2 × 2 power splitter 102 are respectively output during the low level duration, and the fourth optical signal and the sixth optical signal output by the two output ports of the 2 × 2 power splitter 102 are respectively output during the high level duration, wherein the phases of the third optical signal and the fourth optical signal are respectively-90 ° and 180 °, and the phases of the fifth optical signal and the sixth optical signal are respectively 90 ° and 0 °.
Step S103: respectively converting the third optical signal, the fourth optical signal, the fifth optical signal and the sixth optical signal through the first detection unit and the second detection unit to obtain a third electrical signal, a fourth electrical signal, a fifth electrical signal and a sixth electrical signal; in an embodiment, for four optical signals generated by the 2 × 2 power beam splitter, the four optical signals may be detected and converted by the first detection unit and the second detection unit, respectively, to obtain a third electrical signal, the fourth electrical signal, a fifth electrical signal, and a sixth electrical signal.
In an embodiment, before performing the detection conversion on the four optical signals, an attenuation unit may be further disposed on the optical path to attenuate the four optical signals, and make the power of the attenuated third optical signal equal to that of the fifth optical signal, and the power of the fourth optical signal equal to that of the sixth optical signal. In a specific embodiment, the attenuation unit includes an optical attenuator, and specifically, the optical signal with a larger power may be input to the optical attenuator according to the power of the third optical signal and the power of the fifth optical signal; for example, if the power of the third optical signal is greater than that of the fifth optical signal, an optical attenuator is disposed on the optical path where the third optical signal is located, so that the power of the attenuated third optical signal is equal to that of the unattenuated fifth optical signal. In addition, optical attenuators may be disposed on optical paths of the two output ports of the 2 × 2 power splitter, so that the attenuated optical signal powers are equal.
Step S104: and processing and calculating the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal to obtain the distance information of the target to be detected. In an embodiment, after the third electrical signal, the fourth electrical signal, the fifth electrical signal, and the sixth electrical signal are obtained through detection, the third electrical signal, the fourth electrical signal, the fifth electrical signal, and the sixth electrical signal may be differentially amplified by using a differential amplification unit, and then the differentially amplified electrical signals are input to a fourier unit for fourier calculation processing, so as to obtain distance information of the target to be detected.
In the coherent ranging method provided in the embodiments of the present invention, when mixing the first optical signal and the second optical signal, the first optical signal or the second optical signal is subjected to periodic phase modulation, and then the modulated optical signal is mixed with an unmodulated optical signal, so that a size of an adopted mixer can be reduced. Meanwhile, the coherent ranging method can obtain the distance information of the target to be detected by processing and calculating the electrical signal after detection conversion by adopting a Fourier method.
Although the present invention has been described in detail with respect to the exemplary embodiments and the advantages thereof, those skilled in the art will appreciate that various changes, substitutions and alterations can be made to the embodiments without departing from the spirit and scope of the invention as defined by the appended claims. For other examples, one of ordinary skill in the art will readily appreciate that the order of the process steps may be varied while maintaining the scope of the present invention.
Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
Claims (10)
1. An opto-electric hybrid mixer apparatus, comprising: a phase modulation unit and a 2 x 2 power splitter,
the phase modulation unit is used for receiving a first optical signal, and performing periodic phase modulation on the first optical signal to obtain a first modulated optical signal;
the 2 × 2 power splitter is configured to receive a second optical signal and the first modulated optical signal, mix the second optical signal and the first modulated optical signal, the first port of the 2 × 2 power splitter outputs a third optical signal and the second port of the 2 × 2 power splitter outputs a fifth optical signal for a low level duration, the first port of the 2 × 2 power splitter outputs a fourth optical signal and the second port of the 2 × 2 power splitter outputs a sixth optical signal for a high level duration, the third optical signal, the fourth optical signal, the fifth optical signal, and the sixth optical signal each include the mixed first modulated optical signal and the mixed second optical signal, a phase difference between the mixed first modulated optical signal and the mixed second optical signal in the third optical signal and the mixed fourth optical signal is-90 degrees, and in the fifth optical signal and the mixed sixth optical signal, the phase difference between the mixed first modulated optical signal and the second optical signal is 90 degrees.
2. The optoelectronic hybrid mixing apparatus of claim 1, further comprising: a first detection unit and a second detection unit,
the first detection unit is used for receiving the third optical signal and the fourth optical signal and respectively converting the third optical signal and the fourth optical signal into a third electric signal and a fourth electric signal;
the second detection unit is configured to receive the fifth optical signal and the sixth optical signal, and convert the fifth optical signal and the sixth optical signal into a fifth electrical signal and a sixth electrical signal, respectively.
3. The opto-electric hybrid mixing arrangement according to claim 1, wherein the third optical signal and the fourth optical signal have a phase of-90 ° and 180 °, respectively, and the fifth optical signal and the sixth optical signal have a phase of 90 ° and 0 °, respectively.
4. The optoelectronic hybrid mixing apparatus as set forth in claim 1, wherein the 2 x 2 power splitter comprises any one of a 2 x 2 multimode interference coupler, a 2 x 2 directional coupler, a ring cavity coupler, a star coupler, a slab waveguide based fresnel lens array, a slab waveguide based superlens array, and a half mirror.
5. The optoelectronic hybrid mixing apparatus of claim 1, wherein the modulation mechanism of the phase modulation unit comprises: photoelectric effect, elasto-optical effect, magneto-optical effect, and phase change effect.
6. The opto-electric hybrid mixing apparatus of claim 1, further comprising: and the attenuation unit is used for attenuating the optical signal output by the 2 × 2 power beam splitter, so that the power of the attenuated third optical signal is equal to that of the attenuated fifth optical signal, and the power of the attenuated fourth optical signal is equal to that of the attenuated sixth optical signal.
7. A coherent ranging system, comprising: signal generation module, data processing module and the opto-electric hybrid mixing apparatus according to any of claims 2 to 6,
the signal generation module is used for outputting a first optical signal and a first detection signal;
the photoelectric hybrid frequency mixing device is used for receiving the first optical signal and a second optical signal which is reflected by a target to be detected and detected from the first detection signal, and modulating, mixing and detecting the first optical signal and the second optical signal to obtain a third electric signal, a fourth electric signal, a fifth electric signal and a sixth electric signal;
and the data processing module is used for processing and calculating the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal to obtain the distance information of the target to be detected.
8. The coherent ranging system of claim 7, wherein the signal generation module comprises: a light emitting unit, a beam splitting unit and a light transceiving unit,
the light-emitting unit is used for outputting a laser signal;
the beam splitting unit is used for splitting the laser signal to obtain a first optical signal and a second detection signal;
the optical transceiver unit is used for transmitting the first detection signal to a target to be detected in a collimation manner, and receiving and outputting a second optical signal reflected by the target to be detected.
9. The coherent ranging system of claim 7, wherein the data processing module comprises: a differential amplification unit and a Fourier unit,
the differential amplification unit is used for performing differential amplification on the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal and then outputting the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal;
the Fourier unit is used for calculating the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal after differential amplification to obtain the distance information of the target to be detected.
10. A method of coherent ranging, comprising:
dividing a laser signal output by a light-emitting unit into a first optical signal and a first detection signal, wherein the first detection signal is irradiated on a target to be detected and reflected to obtain a second optical signal;
after the first optical signal or the second optical signal is subjected to phase modulation, mixing the first optical signal or the second optical signal with an optical signal which is not subjected to phase modulation to obtain a third optical signal and a fifth optical signal which have low level duration and a fourth optical signal and a sixth optical signal which have high level duration, wherein the third optical signal, the fourth optical signal, the fifth optical signal and the sixth optical signal all comprise the first modulated optical signal and the second optical signal which are subjected to frequency mixing, in the third optical signal and the fourth optical signal, the phase difference between the first modulated optical signal and the second optical signal which are subjected to frequency mixing is-90 degrees, and in the fifth optical signal and the sixth optical signal, the phase difference between the first modulated optical signal and the second optical signal which are subjected to frequency mixing is 90 degrees;
respectively converting the third optical signal, the fourth optical signal, the fifth optical signal and the sixth optical signal through the first detection unit and the second detection unit to obtain a third electrical signal, a fourth electrical signal, a fifth electrical signal and a sixth electrical signal;
and processing and calculating the third electric signal, the fourth electric signal, the fifth electric signal and the sixth electric signal to obtain the distance information of the target to be detected.
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