CN114236881B - Silicon-based photon receiving and transmitting chip and high signal-to-noise ratio analog optical link implementation method thereof - Google Patents
Silicon-based photon receiving and transmitting chip and high signal-to-noise ratio analog optical link implementation method thereof Download PDFInfo
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Abstract
A silicon-based photon receiving and transmitting chip and a high signal-to-noise ratio analog optical link realization method thereof belong to the technical field of microwave photons and solve the problems of large size, unfavorable integration, large analog optical link loss of serial and parallel multi-modulator architecture and high system complexity of the analog optical link realized based on discrete devices in the prior art; the technical scheme of the invention can realize the photoelectric-photoelectric conversion analog optical link by adopting only a single phase modulator and a balance light detector, realizes a silicon-based photon receiving and transmitting chip facing the analog optical link, and has the advantages of small chip size and high integration level; compared with an analog optical link based on serial, parallel and other complex-structure modulators, the analog optical link has a simple structure, and the problems of large loss and complex system of the analog optical link of a serial and parallel multi-modulator architecture are avoided.
Description
Technical Field
The invention belongs to the technical field of microwave photons, and relates to a silicon-based photon transceiver chip and a high signal-to-noise ratio analog optical link implementation method thereof.
Background
The analog optical link for analog radio frequency signal transmission and processing has wide application fields, and can be applied to optical-load wireless communication, cable television, intelligent traffic, phased array antennas, antenna remote radar systems and the like. Typical structures of analog optical links include electro-optic modulation devices (E/0 conversion) and photo-detection devices (0/E conversion), which are connected by fiber optic links. The radio frequency signals are loaded on the optical signals through the modulator, are transmitted through the optical fiber and then return to the photoelectric detector, and are converted into the form of radio frequency signals through photoelectric conversion.
For the above applications of analog optical links, the key components of the link include lasers, high-speed optical modulators, detectors, and the like. However, the current technical schemes are realized based on discrete devices, and the devices are large in size and high in system complexity, so that the research on the high-integration and high-stability analog optical link system has great research significance. Because the silicon-on-insulator (SOI) technology platform device library is relatively mature, passive devices, electro-optical modulators, detectors and the like can be integrated, the system integration level can be remarkably improved, and related silicon-based optoelectronic device research works are introduced according to the requirements of microwave photon links in the literature (Yang Jianyi, zhejiang university) of the publication (publication date 2019), wherein the related silicon-based optoelectronic device research works comprise a high-linearity modulator, a high-saturation detector, a large-range adjustable microwave true time delay line, a light beam forming network time delay module and the like. Therefore, the SOI platform is utilized to monolithically integrate a modulator, a detector and the like on a chip level and is applied to an analog optical link, so that microwave modulation and demodulation based on a photon technology are realized, and the advantages of miniaturization, high integration level and the like are achieved.
Link gain, signal-to-noise ratio, spurious-free dynamic range are important system performance indicators for analog optical links. At present, research on an analog optical link is widely focused on linearization of the link, but the linearization scheme of the link is mainly based on optical domain signal processing of a complex modulator structure, and based on serial or parallel of modulators, the analog optical link with high linearity is realized by optimizing the arrangement of a plurality of parameters such as an optical power distribution ratio, a bias working point, a radio frequency signal power ratio and the like, and a method which is adopted by a document (Linearity Characterization of a Dual-ParallelSilicon Mach-Zehnder Modulator) (yanylang Zhou, IEEE Photonics Journal) with the publication date of 2016 is a parallel modulator. However, the analog optical link of the complex modulator structure greatly increases link loss and has low link gain. Therefore, improving link gain and signal-to-noise ratio is an important research topic in analog optical links.
Disclosure of Invention
The invention aims to design a silicon-based photon transceiver chip and a high signal-to-noise ratio analog optical link implementation method thereof, so as to solve the problems of large size, inconvenience for integration, large analog optical link loss of a serial-parallel multi-modulator architecture and high system complexity of the analog optical link implemented based on discrete devices in the prior art.
The invention solves the technical problems through the following technical scheme:
a silicon-based photonic transceiver chip comprising: a transmit channel and a receive channel integrated on an SOI platform compatible with CMOS processes;
the transmitting channel comprises a first grating coupler (10), a first polarization controller (11), a silicon-based phase modulator (12) and a second grating coupler (13) which are connected through a silicon waveguide (30) in sequence; the first grating coupler (10) couples an input optical signal into the silicon waveguide (30); the first polarization controller (11) controls the input optical signal into a single polarization state TE mode optical signal; the silicon-based phase modulator (12) modulates an input microwave signal onto an optical signal to form an optical-loaded microwave signal, so that the electro-optical conversion in an optical emission channel is realized; the second grating coupler (13) outputs the optical carrier microwave signal through coupling of a single mode fiber;
the receiving channel comprises: a third grating coupler (20), a fourth grating coupler (21), a second polarization controller (22), a thermo-optic phase shifter (23), a 2 x 2 optical coupler (24), and a GeSi balance photodetector (25); the input end of the third grating coupler (20) is connected with a single-mode fiber, an optical carrier microwave signal in the single-mode fiber is coupled and input into a receiving channel, the output end of the third grating coupler (20) is connected with the first input end of the 2X 2 optical coupler (24) through a silicon waveguide (30), the fourth grating coupler (21), the second polarization controller (22) and the thermo-optic phase shifter (23) are sequentially connected through the silicon waveguide (30), the output end of the thermo-optic phase shifter (23) is connected with the second input end of the 2X 2 optical coupler (24) through the silicon waveguide (30), and the first output end and the second output end of the 2X 2 optical coupler (24) are respectively connected corresponding to the first input end and the second input end of the GeSi balance optical detector (25) through the silicon waveguide (30); the fourth grating coupler (21) couples the coherent optical signal into the receiving channel, the second polarization controller (22) controls the input coherent optical signal into a single polarization state TE mode optical signal, the thermal optical phase shifter (23) is used for controlling the working point, the 2X 2 optical coupler (24) couples the optical carrier microwave signal input from the third grating coupler (20) and the coherent optical signal input from the second polarization controller (22), and the equal power is divided into 2 paths of signals and then is respectively transmitted to two input ends of the GeSi balance optical detector (25); the GeSi balance photodetector (25) is used for demodulating and recovering the optical carrier microwave signal into a microwave signal so as to complete photoelectric conversion in the optical receiving channel.
The invention utilizes the SOI platform compatible with the CMOS technology to integrate the silicon-based phase modulator, the thermo-optical phase shifter, the GeSi balance photodetector, the 4 grating couplers, the 2 polarization controllers, the 2X 2 optical coupler and the GeSi balance photodetector on the chip level in a monolithic way, realizes the silicon-based photon transceiver chip facing the analog optical link, has the advantages of small chip size, high integration level, miniaturization, high system stability and the like; in addition, because the SOI platform is compatible with the CMOS process, the silicon-based photon integrated chip can be monolithically integrated with the circuit chip, thereby being beneficial to further improving the integration level and reducing the cost.
The silicon-based phase modulator (12) is a carrier depletion type modulator.
The electrode structure of the silicon-based phase modulator (12) is a coplanar waveguide traveling wave electrode, the electrodes on two sides are ground electrodes G, the middle electrode is a signal electrode S, and a direct-current bias voltage DC and a microwave signal RF are loaded on the middle signal electrode S, wherein the loading of the direct-current reverse bias voltage DC ensures that a phase shifting arm of the silicon-based phase modulator (12) works in a carrier depletion state.
The 2 x 2 optical coupler (24) adopts a 3dB 2 x 2 multimode interference (MMI) coupler or a 2 x 2 directional coupler.
A high signal-to-noise ratio analog optical link implementation method based on the silicon-based photon receiving and transmitting chip comprises the following steps:
s11, inputting optical signals in a transmitting channel;
s12, inputting an electric signal in a transmitting channel;
s13, phase modulation in a transmitting channel;
s14, inputting an optical carrier microwave signal and a coherent optical signal in a receiving channel;
s15, coupling and balanced detection of the optical carrier microwave signal and the coherent optical signal in the receiving channel.
The method for inputting the optical signal in the transmitting channel in step S11 is as follows: the optical signals are coupled into the silicon waveguide (30) through the first grating coupler (10), and the first polarization controller (11) controls the input optical signals to be in a single polarization TE mode and then transmitted to the silicon-based phase modulator (12) for phase modulation; the optical field of the optical signal isWherein E is c For the amplitude of the light field, w c Is the frequency of the optical signal.
The method for inputting the electrical signal in the transmitting channel in step S12 is as follows: loading a microwave signal RF and a direct current reverse bias voltage DC on the silicon-based phase modulator (12), wherein the loading of the direct current reverse bias voltage DC enables the phase shifting arm of the silicon-based phase modulator (12) to work in a PN junction carrier depletion state, and the microwave signal RF is V rf (t)＝υ 0 (cosω 1 t+cosω 2 t), the middle v 0 For the amplitude, ω, of the microwave signal RF 1 ,ω 2 For its angular frequency.
The transmit channels described in step S13The method for medium phase modulation is as follows: the silicon-based phase modulator (12) modulates an input microwave signal onto an optical signal to form an optical carrier microwave signal, and the modulated optical carrier microwave signal is coupled and output to a single-mode fiber through the second grating coupler (13); the optical field expression of the optical carrier microwave signal is as follows:wherein a is A Representing the optical transmission loss coefficient of the modulation arm A For phase shifting caused by the microwave signal and the dc back bias voltage applied to the modulation arm.
The method for inputting the optical carrier microwave signal and the coherent optical signal in the receiving channel in step S14 includes: an optical carrier microwave signal in the single-mode fiber is coupled and input to the silicon waveguide through a third grating coupler (20); the coherent light signal is coupled into the optical waveguide by a fourth grating coupler (21), the second polarization controller (22) controls the input coherent light signal to be a single polarization TE mode, and then the single polarization TE mode is transmitted to the thermo-optic phase shifter (23), and the phase shift of the thermo-optic phase shifter (23) is regulated to phi by controlling the direct current voltage loaded on the thermo-optic phase shifter (23) 0 The expression of the coherent light signal at this time is
The method for coupling and balance detection of the optical carrier microwave signal and the coherent optical signal in the receiving channel in step S15 is as follows:
the 2X 2 optical coupler (24) inputs the optical microwave signal E 1 And coherent optical signal E 2 Coupled by a 2 x 2 optical coupler (24) and split into equal power to obtain two modulated optical signals E 3 ，E 4 The following formula:
modulated optical signal E 3 ，E 4 Respectively enter two input ends of a GeSi balance photodetector (25), and the GeSi balance photodetector (25) is arranged) The responsivity of the input signal is eta, and the noise currents of the two paths of input signals are respectively n 1 (t)，n 2 (t) after photoelectric conversion by the GeSi balance photodetector (25), the photocurrent signals output by the upper path and the lower path of the GeSi balance photodetector (25) are respectively:
when in balance detection, the balance detection photocurrent is the difference between the output current values of the two arms, namely:
according to the carrier dispersion effect of the silicon-based phase modulator (12), the carrier optical transmission loss coefficient a in the formula (3) A Phase modulator phase shift phi A Can be expressed as V rf The third-order polynomial of (t) is specifically as follows:
substituting equation (4) into equation (3) balances the detected photocurrent:
phi-shaped 0 =0, spreading the equation (5) Talor, and retaining only the fundamental frequency term, the second harmonic term, and the third-order intermodulation term, the balanced detection photocurrent can be converted into:
the invention has the advantages that:
1) The silicon-based photon transceiver chip facing the analog optical link is realized by utilizing the SOI platform compatible with the CMOS technology to integrate the silicon-based phase modulator, the thermo-optical phase shifter, the GeSi balance photodetector, the 4 grating couplers, the 2 polarization controllers, the 2X 2 optical coupler and the GeSi balance photodetector on the chip level in a monolithic way, and the chip has the advantages of small size, high integration level, miniaturization, high system stability and the like; in addition, because the SOI platform is compatible with the CMOS process, the silicon-based photon integrated chip can be monolithically integrated with the circuit chip, thereby being beneficial to further improving the integration level and reducing the cost;
2) Compared with an analog optical link based on modulators with complex structures such as serial and parallel, the analog optical link capable of realizing electro-optic-photoelectric conversion only by adopting a single phase modulator and a balanced light detector has the advantages of simple structure and avoiding the problems of large loss and complex system of the analog optical link of a serial and parallel multi-modulator architecture;
3) The invention adopts the balanced detection technology, two paths of photocurrent signals are subtracted, partial noise and direct current items are counteracted, and the input noise level in the system is reduced; in addition, compared with an intensity modulator, the phase modulation has lower optical loss, and the invention adopts the phase modulation with lower optical loss and the coherent balance detection technology, and the power of the fundamental frequency component can be improved by 12dB due to the introduction of coherent optical signals and the utilization of the balanced detection technology.
Drawings
FIG. 1 is a block diagram of a silicon-based photonic transceiver chip in accordance with an embodiment of the present invention;
FIG. 2 is a block diagram of a silicon-based phase modulator of a silicon-based photonic transceiver chip in accordance with an embodiment of the present invention;
fig. 3 is a flowchart of a method for implementing a high signal-to-noise ratio analog optical link of a silicon-based photonic transceiver chip according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The technical scheme of the invention is further described below with reference to the attached drawings and specific embodiments:
example 1
As shown in fig. 1, a silicon-based photonic transceiver chip includes: a first grating coupler 10, a first polarization controller 11, a silicon-based phase modulator 12, a second grating coupler 13, a third grating coupler 20, a fourth grating coupler 21, a second polarization controller 22, a thermo-optic phase shifter 23, a 2 x 2 optical coupler 24, a GeSi balanced photodetector 25, a silicon waveguide 30, a first off-chip laser 40, a second off-chip laser 41, a T-type bias 42;
the first grating coupler 10, the first polarization controller 11, the silicon-based phase modulator 12, the second grating coupler 13, the third grating coupler 20, the fourth grating coupler 21, the second polarization controller 22, the thermo-optic phase shifter 23, the 2×2 optical coupler 24 and the GeSi balance photodetector 25 are all integrated on an SOI platform compatible with the CMOS process, and the silicon waveguide 30 is integrated on the SOI platform.
The first grating coupler 10, the first polarization controller 11, the silicon-based phase modulator 12 and the second grating coupler 13 are sequentially connected through the silicon waveguide 30 to form a transmitting channel; the first grating coupler 10 couples the optical signal of the input of the first off-chip laser 40 into the silicon waveguide 30; the first polarization controller 11 controls the input optical signal to be a single polarization state TE mode optical signal; the silicon-based phase modulator 12 modulates an input microwave signal onto an optical signal to form an optical-loaded microwave signal, so as to realize electro-optical conversion in an optical emission channel; the second grating coupler 13 outputs the optical microwave signal through the coupling of the single mode fiber.
As shown in fig. 2, the silicon-based phase modulator 12 is a carrier depletion modulator based on SOI platform fabrication compatible with CMOS processes; the electrode structure of the silicon-based phase modulator 12 is a coplanar waveguide traveling wave electrode, the electrodes on two sides are ground electrodes G, the middle electrode is a signal electrode S, and a direct-current bias voltage DC and a microwave signal RF are loaded on the middle signal electrode S through a T-type bias 42, wherein the loading of the direct-current reverse bias voltage DC ensures that the phase shifting arm of the silicon-based phase modulator 12 works in a carrier depletion state.
The third grating coupler 20, the fourth grating coupler 21, the second polarization controller 22, the thermo-optic phase shifter 23, the 2 x 2 optical coupler 24 and the GeSi balance photodetector 25 form a receiving channel; the input end of the third grating coupler 20 is connected with a single-mode fiber, an optical carrier microwave signal in the single-mode fiber is coupled and input into a receiving channel, the output end of the third grating coupler 20 is connected with the first input end of the 2 x 2 optical coupler 24 through a silicon waveguide 30, the fourth grating coupler 21, the second polarization controller 22 and the thermo-optic phase shifter 23 are sequentially connected through the silicon waveguide 30, the output end of the thermo-optic phase shifter 23 is connected with the second input end of the 2 x 2 optical coupler 24 through the silicon waveguide 30, and the first output end and the second output end of the 2 x 2 optical coupler 24 are respectively correspondingly connected with the first input end and the second input end of the GeSi balance optical detector 25 through a silicon waveguide 30; the fourth grating coupler 21 couples the coherent optical signal output by the second off-chip laser 41 into the receiving channel, the second polarization controller 22 controls the input coherent optical signal into a single polarization state TE mode optical signal, the thermo-optic phase shifter 23 is used for controlling the working point, the 2×2 optical coupler 24 couples the optical carrier microwave signal input from the third grating coupler 20 and the coherent optical signal input from the second polarization controller 22, and the equal power is divided into 2 paths of signals and then transmitted to two input ends of the GeSi balance photodetector 25 respectively; the GeSi balanced photodetector 25 is configured to demodulate and restore the optical carrier microwave signal into a microwave signal, thereby completing the photoelectric conversion in the optical receiving channel.
The 2×2 optical coupler 24 is a 2×2 multimode interference MMI coupler or a 2×2 directional coupler using 3 dB; the GeSi balanced photodetector 25 is composed of 2 identical detectors on a slice, and in order to achieve two-path photocurrent subtraction, reverse bias voltages need to be applied to both ends of the cascaded detectors to cancel the dc components and only retain the modulated signals.
The invention utilizes the SOI platform compatible with the CMOS technology to integrate the silicon-based phase modulator, the thermo-optical phase shifter, the GeSi balance photodetector, the 4 grating couplers, the 2 polarization controllers, the 2X 2 optical coupler and the GeSi balance photodetector on the chip level in a monolithic way, realizes the silicon-based photon transceiver chip facing the analog optical link, has the advantages of small chip size, high integration level, miniaturization, high system stability and the like; in addition, because the SOI platform is compatible with the CMOS process, the silicon-based photon integrated chip can be monolithically integrated with the circuit chip, thereby being beneficial to further improving the integration level and reducing the cost.
As shown in fig. 3, this embodiment further provides a method for implementing a high signal-to-noise ratio analog optical link based on the above silicon-based photonic transceiver chip, which specifically includes the following steps:
a) Optical signal input in the transmit channel: the optical signal output by the first off-chip laser 40 is coupled to the silicon waveguide 30 through the first grating coupler 10, and the first polarization controller 11 controls the input optical signal to be in a single polarization state TE mode so as to reduce polarization loss, and then the optical signal is transmitted to the silicon-based phase modulator 12 for phase modulation; let the optical field of the optical signal output by the first off-chip laser 40 beWherein E is c For the amplitude of the light field, w c Is the frequency of the optical signal.
b) Electrical signal input in the transmit channel: the microwave signal RF and the direct current reverse bias voltage DC are loaded on the signal electrode of the silicon-based phase modulator through the T-type biaser 42, and the loading of the direct current reverse bias voltage DC enables the phase shifting arm of the silicon-based phase modulator 12 to work in a PN junction carrier depletion state; let the input microwave signal RF be V rf (t)＝υ 0 (cosω 1 t+cosω 2 t), the middle v 0 For the amplitude, ω, of the microwave signal RF 1 ,ω 2 For its angular frequency.
c) Phase modulation in the transmit channel: according to the transmission principle of light in the silicon-based phase modulator 12, the light field expression of the modulated light signal is obtained as:in the formula, the silicon-based phase modulator 12 modulates the arm due to the carrier absorption effectDifferent light loss coefficients, a, are introduced under different driving voltages A Representing the optical transmission loss coefficient of the modulation arm; phi (phi) A Phase shifting caused by the radio frequency signal and the direct current signal loaded on the modulation arm; the modulated microwave signal is then coupled out to a single mode fiber by a second grating coupler 13.
d) Input of optical carrier microwave signals and coherent optical signals in a receiving channel: optical carrier microwave signal in single mode optical fiberCoupling in to the silicon waveguide through a third grating coupler 20; in order to realize demodulation of the radio frequency signal after phase modulation, a coherent optical signal needs to be introduced into a receiving channel, the coherent optical signal is input by a second off-chip laser 41 and is coupled into an optical waveguide by a fourth grating coupler 21, the second polarization controller 22 controls the input coherent optical signal to be in a single polarization state TE mode so as to reduce polarization loss, and then the coherent optical signal is transmitted to the thermo-optic phase shifter 23, and the phase shift of the thermo-optic phase shifter 23 is regulated to phi by controlling the direct current voltage loaded on the thermo-optic phase shifter 23 0 The expression of the coherent light signal is +.>
e) Coupling the optical carrier microwave signal and the coherent optical signal in the receiving channel: since the phase difference between the output ports of the 2×2 optical coupler 24 is always pi/2, the optical carrier microwave signal E is input from the two input ends of the 2×2 optical coupler 24 1 And coherent optical signal E 2 After coupling and equal power beam splitting through a 3dB 2X 2 optical coupler 24, two modulated optical signals E are obtained 3 ，E 4 The following formula:
f) Balanced detection in the receive channel: modulated optical signal E 3 ，E 4 Respectively enter two input ends of the GeSi balance photodetector 25, and are provided with GeSi balance photodetectorThe responsivity of the device 25 is eta, and the noise currents of the two paths of input signals are respectively n 1 (t)，n 2 (t) after photoelectric conversion by the GeSi balance photodetector 25, the photocurrent signals output by the GeSi balance photodetector 25 in the upper and lower paths are respectively:
when in balance detection, the balance detection photocurrent is the difference between the output current values of the two arms, namely:
carrier optical transmission loss coefficient a in equation (3) based on carrier dispersion effect of silicon-based phase modulator 12 A Phase modulator phase shift phi A Can be expressed as V rf The third-order polynomial of (t) is specifically as follows:
substituting equation (4) into equation (3) balances the detected photocurrent:
phi-shaped 0 =0, spreading the equation (5) Talor, and retaining only the fundamental frequency term, the second harmonic term, and the third-order intermodulation term, the balanced detection photocurrent can be converted into:
in the prior art, when a silicon-based intensity modulation combined direct single-tube detection method adopting a single-end push-pull driving mode is adopted, photocurrent can be expressed as:
and (3) developing the equation (7) to only reserve a fundamental frequency term, a second harmonic term and a third-order intermodulation term, and converting photocurrent into:
compared with the intensity modulation combined single-tube detection scheme in the prior art, the method provided by the invention has the advantages that the amplitude of the output fundamental frequency signal is 4 times that of the intensity modulation combined single-tube detection, namely, the power of the fundamental frequency component is improved by 12dB.
The above deduction can be obtained, based on the silicon-based photon receiving and transmitting chip provided by the invention, based on the on-chip silicon-based phase modulator 12 and the GeSi balanced photodetector 25, the electro-optic and photoelectric conversion of microwave signals is realized by utilizing the phase modulation and coherent balance detection technology; based on the coherent balance detection technology, partial noise of the output photocurrent and direct current term are counteracted, so that input noise generated by a laser in the system can be reduced. Compared with an analog optical link based on modulators with complex structures such as serial and parallel, the analog optical link can realize electro-optic-photoelectric conversion by adopting only a single phase modulator and a balanced light detector, has a simple structure, and avoids the problems of large loss and complex system of the analog optical link of a serial and parallel multi-modulator architecture.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A silicon-based photonic transceiver chip, comprising: a transmit channel and a receive channel integrated on an SOI platform compatible with CMOS processes;
the transmitting channel comprises a first grating coupler (10), a first polarization controller (11), a silicon-based phase modulator (12) and a second grating coupler (13) which are connected through a silicon waveguide (30) in sequence; the first grating coupler (10) couples an input optical signal into the silicon waveguide (30); the first polarization controller (11) controls the input optical signal into a single polarization state TE mode optical signal; the silicon-based phase modulator (12) modulates an input microwave signal onto an optical signal to form an optical-loaded microwave signal, so that the electro-optical conversion in an optical emission channel is realized; the second grating coupler (13) outputs the optical carrier microwave signal through coupling of a single mode fiber;
the receiving channel comprises: a third grating coupler (20), a fourth grating coupler (21), a second polarization controller (22), a thermo-optic phase shifter (23), a 2 x 2 optical coupler (24), and a GeSi balance photodetector (25); the input end of the third grating coupler (20) is connected with a single-mode fiber, an optical carrier microwave signal in the single-mode fiber is coupled and input into a receiving channel, the output end of the third grating coupler (20) is connected with the first input end of the 2X 2 optical coupler (24) through a silicon waveguide (30), the fourth grating coupler (21), the second polarization controller (22) and the thermo-optic phase shifter (23) are sequentially connected through the silicon waveguide (30), the output end of the thermo-optic phase shifter (23) is connected with the second input end of the 2X 2 optical coupler (24) through the silicon waveguide (30), and the first output end and the second output end of the 2X 2 optical coupler (24) are respectively correspondingly connected with the first input end and the second input end of the GeSi balance optical detector (25) through the silicon waveguide (30); the fourth grating coupler (21) couples the coherent light signal into the receiving channel, the second polarization controller (22) controls the input coherent light signal into a single polarization state TE mode light signal, the thermal optical phase shifter (23) is used for controlling the working point, the 2X 2 optical coupler (24) couples the light-carried microwave signal input from the third grating coupler (20) and the coherent light signal input from the second polarization controller (22), and the coherent light signal is divided into 2 paths of signals with equal power and then is respectively transmitted to two input ends of the GeSi balance optical detector (25); the GeSi balance photodetector (25) is used for demodulating and recovering the optical carrier microwave signal into a microwave signal so as to complete photoelectric conversion in the optical receiving channel.
2. The silicon-based photonic transceiver chip of claim 1, wherein the silicon-based phase modulator (12) is a carrier-depleted modulator.
3. The silicon-based photon transceiver chip according to claim 2, wherein the electrode structure of the silicon-based phase modulator (12) is a coplanar waveguide traveling wave electrode, the two electrodes are ground electrodes G, the middle electrode is a signal electrode S, and the direct-current bias voltage DC and the microwave signal RF are loaded on the middle signal electrode S, wherein the loading of the direct-current reverse bias voltage DC ensures that the phase-shifting arm of the silicon-based phase modulator (12) works in a carrier depletion state.
4. A silicon-based photonic transceiver chip as claimed in claim 1, wherein the 2 x 2 optical coupler (24) is a 3dB 2 x 2 multimode interference (MMI) coupler or a 2 x 2 directional coupler.
5. A method for implementing a high signal-to-noise ratio analog optical link based on a silicon-based photonic transceiver chip as defined in any one of claims 1 to 4, comprising the steps of:
s11, inputting optical signals in a transmitting channel;
s12, inputting an electric signal in a transmitting channel;
s13, phase modulation in a transmitting channel;
s14, inputting an optical carrier microwave signal and a coherent optical signal in a receiving channel;
s15, coupling and balanced detection of the optical carrier microwave signal and the coherent optical signal in the receiving channel.
6. The method for implementing a high signal-to-noise ratio analog optical link as defined in claim 5, wherein in step S11The method for inputting the optical signals in the transmitting channel comprises the following steps: the optical signals are coupled into the silicon waveguide (30) through the first grating coupler (10), and the first polarization controller (11) controls the input optical signals to be in a single polarization TE mode and then transmitted to the silicon-based phase modulator (12) for phase modulation; the optical field of the optical signal isWherein E is c For the amplitude of the light field, w c Is the frequency of the optical signal.
7. The method for implementing a high signal-to-noise ratio analog optical link according to claim 6, wherein the method for inputting an electrical signal in the transmission channel in step S12 is as follows: loading a microwave signal RF and a direct current reverse bias voltage DC on the silicon-based phase modulator (12), wherein the loading of the direct current reverse bias voltage DC enables the phase shifting arm of the silicon-based phase modulator (12) to work in a PN junction carrier depletion state, and the microwave signal RF is V rf (t)＝υ 0 (cosω 1 t+cosω 2 t), the middle v 0 For the amplitude, ω, of the microwave signal RF 1 ,ω 2 For its angular frequency.
8. The method for implementing high signal-to-noise ratio analog optical link according to claim 7, wherein the method for phase modulation in the transmission channel in step S13 is as follows: the silicon-based phase modulator (12) modulates an input microwave signal onto an optical signal to form an optical carrier microwave signal, and the modulated optical carrier microwave signal is coupled and output to a single-mode fiber through the second grating coupler (13); the optical field expression of the optical carrier microwave signal is as follows:wherein a is A Representing the optical transmission loss coefficient of the modulation arm A For phase shifting caused by the microwave signal and the dc back bias voltage applied to the modulation arm.
9. The high signal-to-noise ratio analog optical link implementation of claim 8The method is characterized in that the method for inputting the optical carrier microwave signal and the coherent optical signal in the receiving channel in the step S14 comprises the following steps: an optical carrier microwave signal in the single-mode fiber is coupled and input to the silicon waveguide through a third grating coupler (20); the coherent light signal is coupled into the optical waveguide by a fourth grating coupler (21), the second polarization controller (22) controls the input coherent light signal to be a single polarization TE mode, and then the single polarization TE mode is transmitted to the thermo-optic phase shifter (23), and the phase shift of the thermo-optic phase shifter (23) is regulated to phi by controlling the direct current voltage loaded on the thermo-optic phase shifter (23) 0 The expression of the coherent light signal at this time is
10. The method for implementing a high signal-to-noise ratio analog optical link according to claim 9, wherein the method for coupling and balancing detection of the optical carrier microwave signal and the coherent optical signal in the receiving channel in step S15 is as follows:
the 2X 2 optical coupler (24) inputs the optical microwave signal E 1 And coherent optical signal E 2 Coupled by a 2 x 2 optical coupler (24) and split into equal power to obtain two modulated optical signals E 3 ，E 4 The following formula:
modulated optical signal E 3 ，E 4 Two input ends respectively entering the GeSi balance photodetector (25), setting the responsivity of the GeSi balance photodetector (25) as eta, and the noise currents respectively input in two paths as n 1 (t)，n 2 (t) after photoelectric conversion by the GeSi balance photodetector (25), the photocurrent signals output by the upper path and the lower path of the GeSi balance photodetector (25) are respectively:
when in balance detection, the balance detection photocurrent is the difference between the output current values of the two arms, namely:
according to the carrier dispersion effect of the silicon-based phase modulator (12), the carrier optical transmission loss coefficient a in the formula (3) A Phase modulator phase shift phi A Can be expressed as V rf The third-order polynomial of (t) is specifically as follows:
substituting equation (4) into equation (3) balances the detected photocurrent:
phi-shaped 0 =0, spreading the equation (5) Talor, and retaining only the fundamental frequency term, the second harmonic term, and the third-order intermodulation term, the balanced detection photocurrent can be converted into:
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