CN112332926B - Balanced receiver and communication system - Google Patents
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- CN112332926B CN112332926B CN202011034836.5A CN202011034836A CN112332926B CN 112332926 B CN112332926 B CN 112332926B CN 202011034836 A CN202011034836 A CN 202011034836A CN 112332926 B CN112332926 B CN 112332926B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
Abstract
The disclosure provides a balanced receiver and a communication system, and belongs to the technical field of communication. The balanced receiver comprises: the two parallel waveguides are respectively used for transmitting signal light and local oscillator light, the signal light and the local oscillator light have the same wavelength, the same frequency, the same polarization state and the initial phase difference of pi/2, and the signal light and the local oscillator light are mutually coupled and coherent in the two waveguides; the detector is laid on the two waveguides along the length direction perpendicular to the waveguides, is positioned at the position where the signal light and the local oscillation light are strongest in coherence, and is used for respectively receiving the light coupled out by the two waveguides, converting the light coupled out by the waveguides into current and differentiating to obtain differential current; and the processing unit is connected with the detector and is used for amplifying and outputting the differential current.
Description
Technical Field
The present disclosure relates to the field of communications technologies, and in particular, to a balanced receiver and a communication system.
Background
Coherent optical communication has the advantages of high sensitivity, long relay distance, good wavelength selectivity, large communication capacity, adoption of various modulation modes and the like, and becomes a very potential choice for the development of future laser communication technology, so that a balanced receiver serving as a core device of a coherent optical communication system is widely researched in recent years.
Disclosure of Invention
The embodiment of the disclosure provides a balanced receiver and a communication system, wherein the balanced receiver has the characteristics of low noise, high sensitivity, small volume and low cost. The technical scheme is as follows:
in one aspect, a balanced receiver is provided, the balanced receiver comprising:
the two parallel waveguides are respectively used for transmitting signal light and local oscillator light, the signal light and the local oscillator light have the same wavelength, the same frequency, the same polarization state and the initial phase difference of pi/2, and the signal light and the local oscillator light are mutually coupled and coherent in the two waveguides;
the detector is laid on the two waveguides along the length direction perpendicular to the waveguides, is positioned at the position where the signal light and the local oscillation light are strongest in coherence, and is used for respectively receiving the light coupled out by the two waveguides, converting the light coupled out by the waveguides into current and differentiating to obtain differential current;
and the processing unit is connected with the detector and is used for amplifying and outputting the differential current.
Optionally, the detector comprises:
a block of photoelectric conversion material laid over the waveguide in a direction perpendicular to a length of the waveguide;
and the metal electrodes are arranged at two ends of the photoelectric conversion material block and are connected with the processing unit.
Optionally, the material of the photoelectric conversion material block is graphene or carbon nanotubes.
Optionally, the metal electrodes at two ends of the photoelectric conversion material block are the same kind of electrodes.
Optionally, the material of the metal electrode is palladium Pd or gold Au.
Optionally, a plurality of parallel detectors are arranged at intervals along the length of the waveguide.
Optionally, the positions of a plurality of parallel detectors are arranged according to the following formula:
x＝L/4+nL；
wherein x is a distance from an input end of the waveguide, L is a length period of power variation of signal light in the waveguide, and n is a positive integer.
Optionally, the block of photoelectric conversion material is rectangular;
the width of the photoelectric conversion material block in the direction perpendicular to the length direction of the waveguide is less than or equal to L/2, wherein L is the length period of power change of the signal light in the waveguide.
Optionally, the number of detectors is 50.
In another aspect, a communication system is provided, the communication system comprising a balanced receiver as described above.
The technical scheme provided by the embodiment of the disclosure has the following beneficial effects:
the embodiment of the disclosure belongs to the technical field of photoelectric communication, and provides a self-differential balanced coherent receiver, namely a balanced receiver for short. When the balanced receiver works, signal light and local oscillator light are respectively injected into the two parallel coupling waveguides, so that the signal light and the local oscillator light generate coherent mixing in the parallel coupling waveguides; the signal light and the local oscillator light with the initial phase difference of pi/2 form stable coherent light intensity distribution in the parallel coupling waveguide; laying a detector at the position where the coherence of the parallel coupling waveguide is strongest; the two ends of the detector respectively absorb coherent enhanced light and coherent attenuated light to generate photocurrent, the photocurrent generated at the two ends is subjected to composite offset in the detector to complete self-differentiation, and then the difference value of the photocurrent at the two ends is output, and then the processing unit is used for amplification processing, and finally self-balanced coherent reception is realized. The self-differential balanced coherent receiver realizes coherent demodulation through coupling coherence of the two waveguides, and realizes balanced output of coherent reception by utilizing self-differential characteristics through the detector.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a balanced receiver provided in an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of coherence in two waveguides provided by an embodiment of the present disclosure;
fig. 3 is a self-differentiating schematic provided by embodiments of the present disclosure.
Detailed Description
To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a balanced receiver according to an embodiment of the present disclosure. Referring to fig. 1, the balanced receiver includes: two parallel waveguides 101, a detector 102 and a processing unit 103.
The two parallel waveguides 101 are respectively used for transmitting signal light and local oscillator light, the signal light and the local oscillator light have the same wavelength, the same frequency, the same polarization state and the initial phase difference of pi/2, and the signal light and the local oscillator light are mutually coupled and coherent in the two waveguides; here, the signal light and the local oscillator light are coupled with each other, so that part of the signal light and the local oscillator light exist in one waveguide at the same time, and the signal light and the local oscillator light are coherent in the same waveguide.
The detector 102 is laid on the two waveguides 101 along a direction perpendicular to the length direction of the waveguides 101, the detector 102 is located at a position where the signal light and the local oscillation light are the strongest in coherence, and the detector 102 is used for receiving the light coupled out by the two waveguides 101, converting the light coupled out by the waveguides into current, and differentiating to obtain differential current;
and the processing unit 103 is connected with the detector 102 and is used for amplifying and outputting the differential current.
In the embodiment of the disclosure, the signal light and the local oscillator light are both laser signals with the same wavelength, the waveforms of the two laser signals are the same, but a phase difference of pi/2 exists in the initial phase, the signal light and the local oscillator light are both linearly polarized light, and the signal light and the local oscillator light are respectively injected into the two parallel coupling waveguides in the same polarization state, so that the signal light and the local oscillator light can be mutually coupled and coherent in the two waveguides.
Fig. 2 is a schematic diagram of coherence in two waveguides provided by an embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view of a waveguide 101. referring to fig. 2, when coherence occurs, coherence is enhanced in one of two parallel waveguides 101 and is reduced in the other waveguide 101. Therefore, the detector 102 is located at a position on one waveguide 101 where the signal light and the local oscillation light have the strongest coherence, that is, at a coherence enhancing region (reference sign a in fig. 2) of the coherent light field, and on the other waveguide 101, the detector 102 is located at a position where the signal light and the local oscillation light have the weakest coherence, that is, at a coherence weakening region (reference sign b in fig. 2) of the coherent light field.
In the two parallel waveguides 101, the signal light and the local oscillator light need to satisfy the condition that the initial phase difference is pi/2, so that the strongest and stable coherent optical field distribution can be formed between the two waveguides 101.
In the embodiment of the present disclosure, the detector 102 is laid over the two waveguides 101 at the same time, so that the detector 102 can receive the coherent light coupled out by the two waveguides 101 at the same time, and thus the two ends of the detector can generate photoelectric conversion at the same time to generate photocurrent. Through the difference process, the noise in the current can be eliminated, so that the signal precision is improved, and a foundation is provided for subsequent signal processing.
The embodiment of the disclosure belongs to the technical field of photoelectric communication, and provides a self-differential balanced coherent receiver, namely a balanced receiver, which can be used for replacing a balanced detector of a traditional coherent receiver. When the balanced receiver works, signal light and local oscillator light are respectively injected into the two parallel coupling waveguides, so that the signal light and the local oscillator light generate coherent mixing in the parallel coupling waveguides; the signal light and the local oscillator light with the initial phase difference of pi/2 form stable coherent light intensity distribution in the parallel coupling waveguide; laying a detector at the position where the coherence of the parallel coupling waveguide is strongest; the two ends of the detector respectively absorb coherent enhanced light and coherent attenuated light to generate photocurrent, the photocurrent generated at the two ends is subjected to composite offset in the detector to complete self-differentiation, and then the difference value of the photocurrent at the two ends is output, and then the processing unit is used for amplification processing, and finally self-balanced coherent reception is realized. The self-differential balanced coherent receiver realizes coherent demodulation through coupling coherence of the two waveguides, realizes balanced output of coherent reception by utilizing self-differential characteristics through the detector, realizes the differential process of the balanced receiver based on carrier compounding, internally offsets noise of a direct current component, and has the characteristics of low noise, high sensitivity, small volume and low cost.
In the disclosed embodiment, the waveguide 101 may be an integrated optical waveguide, including a planar dielectric optical waveguide and a strip dielectric optical waveguide, such as a silicon waveguide. The waveguide 101 may also be a cylindrical optical waveguide, such as an optical fiber. It should be noted that, since in the present disclosure, the probe needs to be laid over the waveguide 101 to receive the coupled coherent light, no matter what material is used for the waveguide 101, the portion of the waveguide 101 in contact with the probe 102 must be transparent, so as to ensure that the probe 102 can realize photoelectric conversion.
In this disclosed embodiment, signal light and local oscillator light are laser, and the wavelength of signal light and local oscillator light can be in 1550nm effect.
In the embodiment of the present disclosure, the signal light and the local oscillator light may be transmitted to the receiving end simultaneously by using the transmission line, and coherent reception is performed by the balanced receiver, or only the signal light may be transmitted in the transmission line, and the local device provides the local oscillator light, thereby completing coherent reception.
For example, a local oscillator light source may be locally provided to provide the local oscillator light, and the local oscillator light provided by the local oscillator light source and the signal light may satisfy the foregoing relationship.
As shown in fig. 1, in the embodiment of the present disclosure, the detector 102 may include:
a block of photoelectric conversion material 121, the block of photoelectric conversion material 121 laid on the waveguide 101 in a direction perpendicular to a length direction of the waveguide 101;
and metal electrodes 122 disposed at both ends of the photoelectric conversion material 121, wherein the metal electrodes 122 are connected to the processing unit 103.
The direction a in fig. 1 is the longitudinal direction of the waveguide 101, and the direction B in fig. 1 is the direction perpendicular to the longitudinal direction of the waveguide 101.
Fig. 3 is a schematic self-differencing provided by an embodiment of the disclosure, and a process for self-differencing the detector 102 will be briefly described below with reference to fig. 3. Referring to fig. 3, reception of coherent light is performed by the photoelectric conversion material block 121; metal electrodes 122 made of the same material are arranged at two ends of the photoelectric conversion material block 121, a potential barrier (labeled as c in fig. 3) is formed between the photoelectric conversion material block 121 and the metal electrodes 122, coherent light irradiates on the photoelectric conversion material block 121 to separate electrons and holes, due to the existence of the potential barrier, electrons at the left end move to the right end, electrons at the right end move to the left end, the electrons at the right end and the holes at the left end are recombined (heated) and cancelled, and the electrons at the left end and the holes at the right end are recombined and cancelled, and due to the difference of coherent light intensities received at the two ends, the numbers of the holes and the electrons at the left end and the right end are different, so that the electrons at one end are not completely cancelled, the holes at the other end are not completely cancelled, the electrons and the holes overflow, and a differential current is formed on a loop formed by the detector 102 and the processing unit 103. It should be noted that the dotted line in fig. 3 is only for representing the barrier height and the electron movement, and is not the structure of the detector 102.
Referring to fig. 3, the detector may change the magnitude and even direction of the output current due to different positions of light spots under the condition of light incidence, and when the coherent light irradiates the two ends of the detector respectively, the output current is a differential current obtained by combining two paths of photocurrents generated near the electrodes at the two ends of the detector at the center:
Iout＝I1-I2 (1)
wherein, IoutTo output photocurrent, I1And I2Two paths of light currents generated near the electrodes at two ends are respectively generated.
Referring to fig. 2 again, in combination with the coherent mixing technology, the photocurrent at the two ends of the detector respectively corresponds to the coherent enhancement region and the coherent subtraction region, and homodyne detection is performed (that is, the frequencies of the signal light and the local oscillator light are the same), so that the maximum differential current output item can be directly obtained:
wherein R is the absorption conversion efficiency of the detector, PsIs the power of the signal light, PLOThe power of the local oscillator light, the power of the signal light and the power of the local oscillator light are periodically changed.
In the formulae (2) and (3), 0.5R (P)s+PLO) The dc component is the dc component, and the rest is the ac component, and it can be seen from equation (4) that the dc component in the two signals is eliminated in the form of carrier recombination inside the device, so the intensity noise related to dc is eliminated (much larger than the ac component noise).
Illustratively, the material of the photoelectric conversion material block 121 is graphene. When the material of the photoelectric conversion material block 121 is graphene, the photoelectric conversion material block 121 may be a graphene nanoribbon.
Laying graphene at the strongest coherent position in the parallel coupling waveguide 101, wherein the distance between two ends of the graphene is not large, performing coherent coupling on signal light and local oscillator light through the parallel coupling waveguide to form stable coherent light field distribution, and absorbing the coherent light by the graphene by utilizing an evanescent wave coupling principle; laying the same kind of metal electrodes at two ends to form the graphene detector, completing differential offset of a photocurrent direct current part in the graphene by utilizing the photoresponse current self-differential characteristic of the same kind of graphene electrodes, completing self-differential, and outputting a coherent mixing signal (coherent mixing refers to signal components formed by mixing signal light and local oscillator light together
). Due to the fact that the carrier mobility of the graphene is high, ultra-high-speed and high-sensitivity coherent signal output can be achieved, and therefore the bandwidth of the whole balanced receiver can be improved.
According to the balanced receiver provided by the embodiment of the disclosure, by adopting a combination mode of the graphene detector and the parallel coupling waveguide, two ends of the graphene detector are respectively located at positions corresponding to a coherent enhancement region and a coherent attenuation region of signal light and local oscillator light on the parallel coupling waveguide, and a balanced detection function of coherent reception is completed by utilizing self-differential characteristics of the graphene and the same kind of electrodes. The high-speed characteristic of the graphene is utilized to realize high bandwidth, the structure of the receiver is simplified, the noise of the receiver is reduced, and the sensitivity is improved. The method has the advantages that the mobility advantage of the high-speed current carrier of the graphene is exerted, and meanwhile, the generation of local oscillation photocurrent is restrained, so that the photocurrent shot noise is further reduced, and the signal-to-noise ratio of an output signal is effectively improved.
Further, the material of the photoelectric conversion material block 121 in the detector 102 may also be carbon nanotubes or other materials, which is not limited in this disclosure.
In the embodiment of the present disclosure, the metal electrodes at the two ends of the photoelectric conversion material block 121 are the same kind of electrodes, and the same kind of electrodes refer to the same material of the metal electrodes at the two ends of the photoelectric conversion material block 121.
In one possible implementation, the material of the metal electrode 122 is palladium Pd or gold Au.
The metal electrodes made of the materials can ensure the formation of the potential barrier on one hand, and have high conductivity on the other hand, so that the bandwidth of the whole balanced receiver can be improved.
In other possible implementations, other materials, such as gold, silver, etc., may be used for the metal electrodes 122, but whichever material is used, it is necessary to ensure that the materials of the metal electrodes 122 at both ends of the detector 102 are the same.
In the embodiment of the present disclosure, a plurality of parallel detectors 102 are arranged at intervals along the length direction of the waveguide 101.
In the embodiment of the disclosure, through multi-stage absorption in a parallel connection mode, the photoelectric responsivity of the whole receiver is improved, and the magnitude of current output to the processing unit is improved, so that the accuracy of the whole balanced receiver is improved.
In the disclosed embodiment, the positions of a plurality of parallel detectors 102 are arranged according to the following formula:
x＝L/4+nL (5)
wherein x is a distance from an input end of the waveguide 101, L is a length period of power variation of signal light in the waveguide 101, and n is a positive integer.
In the parallel coupling waveguide, the optical power in the two waveguides changes continuously along with the change of the length of the waveguides, and the change rule has periodicity, so that the detectors need to be placed at proper positions, and each detector is ensured to be positioned in a coherent enhancement area and a coherent attenuation area of signal light and local oscillator light on the parallel coupling waveguide.
The position distribution of the detector 102 is briefly described below with reference to the formula:
setting the period of the optical power change along the waveguide length in the parallel coupling waveguide as L, wherein the L is related to the coupling coefficient of the waveguide, such as 2 pi-KcL，KcIs the waveguide coupling coefficient, KcRelated to waveguide materials, structural parameters, incident wavelength, etc. Taking a parallel strip waveguide as an example, the height and width of two parallel waveguides are both set to be a, the distance between the waveguides is c, and the refractive index of the waveguide material is n1Refractive index of the outer space of the waveguide being n2The wavelength of the incident light is lambda and the wave number of the incident light is k0(i.e., 2 π/λ), the transverse mode propagation, the coupling coefficient is specifically shown in equation (6):
where β is the propagation constant of light within the waveguide, kxIs the transverse component of the propagation constant in the waveguide, pxIs the transverse component of the propagation constant outside the waveguide (cladding).
Power P of signal lightSPower P of local oscillator lightLOThen, the signal optical power and the local oscillator optical power in the upper and lower waveguides vary with the waveguide length x as follows (superscript 1 indicates the waveguide on which the signal light enters, and superscript 2 indicates the waveguide on which the local oscillator light enters):
considering the initial phase difference of the signal light and the local oscillator light and the phase change in the waveguide coupling process, when the phase difference of the signal light and the local oscillator light in the two waveguides is 0 and pi respectively, coherence enhancement and coherence weakening can occur respectively, the coherent light intensity distribution also presents a periodic variation trend related to L, and the light power distribution in the two waveguides is as follows:
from the optical field distribution in the two parallel waveguides, it can be seen that the best coherent detection output can be obtained only when 2 pi x/L pi/2 +2n pi, i.e. x L/4+ nL, the coherent mixing part is the largest and the dc parts are equal and completely cancelled out, so the detector should be placed at x L/4+ nL.
In the embodiment of the present disclosure, the cross section of the block of photoelectric conversion material 121 is rectangular;
the width of the block of photoelectric conversion material 121 in the direction perpendicular to the length of the waveguide 101 is less than or equal to L/2, where L is the length period of the power change of the signal light in the waveguide 101.
Since the photoelectric conversion material block 121 has a certain width, and the absorption conversion efficiency R of the photoelectric conversion material block 121 to light is low, the output photocurrent of the photoelectric conversion material block 121 with the width d should be:
as can be seen from equation (9), the width of the block of photoelectric conversion material 121 can only be up to L/2 at the maximum, and exceeding this width will reduce the total output current instead. Meanwhile, since the overall response of a single photoelectric conversion material block 121 is low, it is difficult to form an effective differential output, and thus, a plurality of detectors are connected in parallel to ensure the overall output.
The sum of the widths of the photoelectric conversion material blocks 121 in the plurality of detectors is LSFor example. The width of each block 121 of photoelectric conversion material is the same, and the total output photocurrent can be simply expressed as:
according to the analysis of the above formula, the function of the total output photocurrent with respect to d is a monotone decreasing function, which means that when multiple detectors are connected in parallel to realize full absorption of optical signals, the smaller the width d of the photoelectric conversion material block 121, the better, so that the maximum response output current can be obtained.
However, the width of the photoelectric conversion material blocks 121 cannot approach zero completely, and the number of the photoelectric conversion material blocks 121 cannot be manufactured too much, so that it is finally required to select an appropriate width of the photoelectric conversion material blocks 121 and an appropriate number of the photoelectric conversion material blocks 121 according to process conditions to construct an appropriate self-differential balanced coherent receiver.
Illustratively, the width of the block of photoelectric conversion material 121 in the direction perpendicular to the length of the waveguide 101 is smaller than the period L of the optical power variation with the waveguide length in the parallel-coupled waveguide, so as to avoid that a whole block of photoelectric conversion material 121 covers several periods at the same time, which causes photocurrent cancellation during different periods to affect the output.
For example, the width of the block of photoelectric conversion material 121 may range in the um order, e.g., 1 to 10 um.
Illustratively, the length of the photoelectric conversion material block 121 is related to the waveguide coupling coefficient and the barrier width, and the length of the photoelectric conversion material block 121 is in the um order, for example, 1-10 um. The width of the photoelectric conversion material block 121 defines the space between the waveguides, and the space between the waveguides is defined in the above range, so that the signal light and the local oscillator light in the two waveguides can be coupled.
Illustratively, the number of the photoelectric conversion material blocks 121 may be 50, that is, the number of the detectors is 50, each detector has an absorption rate of about 2% for light, and the absorption of the light signal is performed by 50 detectors.
In the embodiment of the present disclosure, assuming that the absorptivity of the detector for the local oscillation light and the signal light is required to reach a certain percentage, for example, 50%, then the number of the photoelectric conversion material blocks 121 is determined based on the ratio that each of the photoelectric conversion material blocks 121 can absorb.
In addition, after the number of the photoelectric conversion material blocks 121 is determined, the length of the waveguide 101 can be determined based on the position where the aforementioned photoelectric conversion material blocks 121 are arranged (i.e., the arrangement position of the detectors), and the size of the period length L. In order to avoid the waveguide 101 having a too long length and thus a too large volume of the whole balanced receiver, the number of the aforementioned blocks 121 of photoelectric conversion material is not suitable.
In the embodiment of the present disclosure, the closer the distance between the two waveguides 101 is, the better the coupling effect is, but too close the distance between the two ends of the photoelectric conversion material 121 in contact with the two waveguides 101 is too close, and the ideal differential effect may not be achieved. Therefore, in the embodiment of the present disclosure, the length of the block of photoelectric conversion material 121 is in the order of um, for example, 1 to 10 um.
In the embodiment of the present disclosure, the processing unit 103 may include an amplifier, and since the differential current output by the detector 102 is small, in order to ensure the magnitude of the output signal, the differential current output by the detector 102 may be amplified, so that the whole balanced receiver finally obtains an electrical signal with low noise.
Further, the processing unit 103 may perform signal filtering or other processing procedures besides amplifying the signal, which is not limited in this disclosure.
Accordingly, the processing unit 103 may further comprise a filter, by which noise in the signal is removed.
For another example, the processing unit may further include a shaping circuit for shaping the signal.
The embodiment of the disclosure also provides a communication system, which includes a sending end and a receiving end, and the sending end and the receiving end communicate with each other.
The receiving end of the communication system comprises a balanced receiver as shown in fig. 1.
The embodiment of the disclosure belongs to the technical field of photoelectric communication, and provides a self-differential balanced coherent receiver, namely a balanced receiver, which can be used for replacing a balanced detector of a traditional coherent receiver. When the balanced receiver works, signal light and local oscillator light are respectively injected into the two parallel coupling waveguides, so that the signal light and the local oscillator light generate coherent mixing in the parallel coupling waveguides; the signal light and the local oscillator light with the initial phase difference of pi/2 form stable coherent light intensity distribution in the parallel coupling waveguide; laying a detector at the position where the coherence of the parallel coupling waveguide is strongest; the two ends of the detector respectively absorb coherent enhanced light and coherent attenuated light to generate photocurrent, the photocurrent generated at the two ends is subjected to composite offset in the detector to complete self-differentiation, and then the difference value of the photocurrent at the two ends is output, and then the processing unit is used for amplification processing, and finally self-balanced coherent reception is realized. The self-differential balanced coherent receiver realizes coherent demodulation through coupling coherence of the two waveguides, and realizes balanced output of coherent reception by utilizing self-differential characteristics through the detector.
The above description is intended to be exemplary only and not to limit the present disclosure, and any modification, equivalent replacement, or improvement made without departing from the spirit and scope of the present disclosure is to be considered as the same as the present disclosure.
Claims (8)
1. A balanced receiver, characterized in that the balanced receiver comprises:
the two parallel waveguides are respectively used for transmitting signal light and local oscillator light, the signal light and the local oscillator light have the same wavelength, the same frequency, the same polarization state and the initial phase difference of pi/2, and the signal light and the local oscillator light are mutually coupled and coherent in the two waveguides;
the detector is laid on the two waveguides along the length direction perpendicular to the waveguides, is positioned at the position where the signal light and the local oscillation light are strongest in coherence, and is used for respectively receiving the light coupled out by the two waveguides, converting the light coupled out by the waveguides into current and differentiating to obtain differential current;
the processing unit is connected with the detector and used for amplifying the differential current and outputting the amplified differential current;
the probe, comprising:
a block of photoelectric conversion material laid over the waveguide in a direction perpendicular to a length of the waveguide;
the metal electrodes are arranged at two ends of the photoelectric conversion material block and are connected with the processing unit;
the material of the photoelectric conversion material block is graphene or carbon nano tubes.
2. The balanced receiver according to claim 1, characterized in that the metal electrodes at both ends of the block of photoelectric conversion material are homogeneous electrodes.
3. The balanced receiver according to claim 1, characterized in that the material of the metal electrodes is palladium Pd or gold Au.
4. A balanced receiver according to any one of claims 1 to 3, wherein a plurality of the detectors are arranged in parallel at intervals along the length of the waveguide.
5. The balanced receiver according to claim 4, characterized in that the positions of a plurality of parallel detectors are arranged according to the formula:
x＝L/4+nL；
wherein x is a distance from an input end of the waveguide, L is a length period of power variation of signal light in the waveguide, and n is a positive integer.
6. The balanced receiver of claim 4, characterized in that the block of photoelectric conversion material is rectangular;
the width of the photoelectric conversion material block in the direction perpendicular to the length direction of the waveguide is less than or equal to L/2, wherein L is the length period of power change of the signal light in the waveguide.
7. The balanced receiver of claim 4, characterized in that the number of detectors is 50.
8. A communication system, characterized in that it comprises a balanced receiver according to any of claims 1 to 7.
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