A one-to-many point free-space optical communication system based on optical frequency comb

Abstract

The present invention discloses a one-to-many point free space optical communication system based on an optical frequency comb, wherein the optical signal modulation and transmission end comprises a high-gain multi-channel optical frequency comb source, an optical polarization controller, an optoelectronic modulation unit, a first optical amplifier, an optical signal transmitter, a wavelength separation module and an optical collimation unit connected in sequence, and the optical signal receiving and demodulation end comprises an optical signal receiver, a second optical amplifier and a photodetector connected in sequence. By using a high-gain optical frequency comb source, an optical signal channel with stable frequency spacing and coherence can be obtained; by using a wavelength separation unit, a single-point light source containing multiple wavelengths can be simply separated to obtain multiple single-wavelength optical signals, and each optical signal will carry the same modulation signal, thereby achieving point-to-multipoint free space optical signal synchronous transmission; if the optical frequency comb source used has a higher repetition frequency, that is, the interval between adjacent wavelengths is farther, then the single channel can have a higher-speed transmission capability.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a one-to-multipoint free space optical communication system based on an optical frequency comb. Background Art

[0002] Optical communication includes two methods: fiber optic communication and free space optical communication (FSO). Fiber optic communication uses optical fiber as a transmission channel for communication, and the overall technology development is relatively mature. Free space optical communication modulates electrical signals containing information onto light, and uses light as a carrier to transmit information in free space or the atmosphere. This technology uses lasers as information carriers and does not require any wired channels as transmission media.

[0003] In certain situations, free space optical communication combines the advantages of radio communication and fiber optic communication. This method does not require a spectrum license and has the special advantages of high bandwidth, transparent protocol, low cost, strong security, low power, small size, and low latency. It is regarded as a world-leading advanced communication technology with unique technical characteristics, and is also considered to be the most potential disruptive technology.

[0004] Free space optical communication enables point-to-point Or point to multipoint (P2MP) bidirectional communication technology, where point to multipoint refers to communication through a specific one-to-many connection type, that is, providing multiple channels from a single location to multiple locations. Driven by the demand for the Internet of Everything, point-to-multipoint optical communication technology will replace traditional point-to-point optical communication technology and play an important role in the future "optical connection of everything" scenario. At the same time, point-to-multipoint laser communication technology is also generally considered to be a key node in building an integrated sky-ground information network and a necessary prerequisite for realizing multi-satellite networking link communication. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a one-to-multipoint free-space optical communication system based on optical frequency comb.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] A one-to-multipoint free-space optical communication system based on an optical frequency comb comprises an optical signal modulation and transmission end and an optical signal receiving and demodulation end, wherein the optical signal modulation and transmission end comprises a high-gain multi-channel optical frequency comb source, an optical polarization controller, an optoelectronic modulation unit, a first optical amplifier, an optical signal transmitter, a wavelength separation module and an optical collimation unit connected in sequence, and the optical signal receiving and demodulation end comprises an optical signal receiver, a second optical amplifier and a photodetector connected in sequence;

[0008] A high-gain multi-channel optical frequency comb source is used to generate a series of discrete, equally spaced spectrum, phase-coherent stable light sources, wherein each optical frequency comb in the light source can be used as an independent optical path carrier for communication transmission, thereby realizing simultaneous multi-channel signal transmission of a single device; the multi-channel optical frequency comb source passes through an optical polarization controller to change the mode field form of the optical signal in the optical fiber; the optoelectronic modulation unit is used to load the preset sequence information on the polarized light after polarization control for information encoding; the modulated multi-channel optical signal will pass through the first optical amplifier, and the function of the second optical amplifier is to compensate the power loss of the optical signal through the optoelectronic modulation unit through high gain; the modulated and amplified The completed multi-channel optical signals are transmitted to the wavelength separation module in the form of a point light source via an optical signal transmitter; the wavelength separation module separates the incident multi-channel optical frequency comb point light sources into multiple independent single-channel optical frequency comb sources one by one; the separated multiple single-wavelength optical signals pass through the free space and then pass through the optical collimation unit to collimate and homogenize the incident multiple light beams into mutually parallel optical signals; the collimated multiple single-wavelength optical signals are then received one by one by a number of optical signal receivers after passing through the free space; the loss of optical power in free space transmission will be compensated by the second optical amplifier; the photodetector functions to convert the received amplified optical signal into an electrical signal.

[0009] Preferably, the optical signal modulation and transmission end also includes a third optical amplifier arranged between the high-gain multi-channel optical frequency comb source and the optical polarization controller, and the third optical amplifier is used to pre-amplify the optical power of the multi-channel optical frequency comb source and send the amplified multi-channel optical frequency comb source to the optical polarization controller.

[0010] Preferably, the photoelectric modulation unit includes an electro-optical modulator and a programmable optical processor. The programmable optical processor is connected to the electro-optical modulator. The programmable optical processor carries preset sequence information and sends the preset sequence information to the electro-optical modulator. The electro-optical modulator loads the preset sequence information on the polarized light after polarization control to encode the information.

[0011] Preferably, the overall output light power of the high-gain multi-channel optical frequency comb source is at least +10dBm, and the spectral operating wavelength is 1310±10 nm; when the repetition frequencies of the optical frequency comb source are 25GHz, 50GHz, 100GHz and 200GHz, respectively, the spacing between adjacent optical combs is at least 0.14nm, 0.28nm, 0.56nm and 1.12nm, respectively.

[0012] Preferably, the wavelength separation module can be implemented by a diffraction grating, a prism or a multi-layer thin film filtering technology.

[0013] Preferably, the diffraction grating is a flat glass or metal sheet engraved with a large number of parallel, equal-width, periodic and equidistant slits. The number of slits in the grating is large, and the resolution is tens to thousands per millimeter. When the polychromatic light passes through the grating, it causes the amplitude and / or phase of the incident light to be periodically spatially modulated through a regular structure, and finally the incident light is divided into multiple beam paths by diffraction, so that light of different wavelengths is scattered at different angles in space and finally propagates in different directions, so that spectral lines of different wavelengths appear at different positions to form a spectrum.

[0014] Preferably, the two adjacent wavelengths output by the wavelength separation module and Angular spacing between , specifically:

[0015] ;

[0016] in, is the diffraction order, and are two adjacent wavelengths output by the wavelength separation module. is the grating constant, i.e. the distance between adjacent grating lines.

[0017] Preferably, the optical signal transmitter is formed by precisely positioning a pigtail and a lens, and is used to convert the transmission light in the optical fiber into a beam of collimated light.

[0018] Preferably, a single optical signal receiver is composed of a pigtail fiber and a single collimating lens, and the collimating lens is used to focus the received parallel optical signal and perform subsequent transmission via the pigtail fiber.

[0019] Preferably, it also includes an optical sampling oscilloscope and a real-time optical oscilloscope, the optical sampling oscilloscope is connected to the second optical amplifier, the real-time optical oscilloscope is connected to the photodetector, the optical sampling oscilloscope is used to collect the amplified received optical signal and generate an eye diagram for display, the photodetector is used to convert the received amplified received optical signal into an electrical signal, the real-time optical oscilloscope is used to display the received electrical signal and complete the calculation of the bit error rate.

[0020] The above-mentioned one-to-many point free-space optical communication system based on an optical frequency comb can obtain a coherent optical signal channel with stable frequency spacing by using a high-gain optical frequency comb source; by using a wavelength separation unit, a single-point light source containing multiple wavelengths can be simply separated to obtain multiple single-wavelength optical signals, and each optical signal will carry the same modulation signal, thereby achieving point-to-multipoint free-space optical signal synchronous transmission; if the optical frequency comb source used has a higher repetition frequency, that is, the interval between adjacent wavelengths is farther, then the single channel can have a higher-speed transmission capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic diagram of the structure of a one-to-multipoint free-space optical communication system based on an optical frequency comb in one embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0023] In one embodiment, Figure 1 As shown, a one-to-multipoint free-space optical communication system based on an optical frequency comb includes an optical signal modulation and transmission end and an optical signal receiving and demodulation end, wherein the optical signal modulation and transmission end includes a high-gain multi-channel optical frequency comb source 11, an optical polarization controller 13, an optoelectronic modulation unit, a first optical amplifier 16, an optical signal transmitter 17, a wavelength separation module 18 and an optical collimation unit 19 connected in sequence, and the optical signal receiving and demodulation end includes an optical signal receiver 21, a second optical amplifier 22 and a photodetector 24 connected in sequence;

[0024] The high-gain multi-channel optical frequency comb source 11 is used to generate a series of discrete, equally spaced spectrum, phase-coherent stable light sources, wherein each optical frequency comb in the light source can be used as an independent optical path carrier for communication transmission, thereby realizing simultaneous multi-channel signal transmission of a single device; the multi-channel optical frequency comb source 11 changes the mode field form of the optical signal in the optical fiber through an optical polarization controller; the optoelectronic modulation unit is used to load the preset sequence information on the polarized light after polarization control for information encoding; the modulated multi-channel optical signal will pass through the first optical amplifier 16, and the function of the second optical amplifier 2222 is to compensate the power loss of the optical signal through the optoelectronic modulation unit through high gain; the modulated and amplified Multi-channel optical signals are transmitted to the wavelength separation module 18 in the form of a point light source via the optical signal transmitter 17; the wavelength separation module 18 separates the incident multi-channel optical frequency comb point light sources into multiple independent single-channel optical frequency comb sources 11 one by one; the separated multiple single-wavelength optical signals pass through the free space and then pass through the optical collimation unit 19 to collimate and homogenize the incident multiple light beams into mutually parallel optical signals; the collimated multiple single-wavelength optical signals are then received one by one by a number of optical signal receivers 21 after passing through the free space; the loss of optical power in free space transmission will be compensated by the second optical amplifier 22; the photodetector 24 functions to convert the received amplified optical signal into an electrical signal.

[0025] Specifically, the high-gain multi-channel optical frequency comb source 11 generates a series of discrete, equally spaced spectrum, phase-coherent stable light sources through mode-locking, Kerr effect or electro-optic modulation (EO modulation).

[0026] Furthermore, the present invention preferably uses a multi-channel optical frequency comb source 11 with a larger optical output power and a wider spectrum. At the same time, in order to make the propagation rate of a single channel as large as possible, the spacing between adjacent optical combs needs to be as wide as possible.

[0027] In one embodiment, the overall optical output power of the high-gain multi-channel optical frequency comb source 11 is at least +10dBm, and the spectral operating wavelength is 1310±10 nm; when the repetition frequencies of the optical frequency comb source are 25GHz, 50GHz, 100GHz and 200GHz, respectively, the spacing between adjacent optical combs is at least 0.14nm, 0.28nm, 0.56nm and 1.12nm, respectively.

[0028] In one embodiment, the optical signal modulation and transmission end also includes a third optical amplifier 12 arranged between the high-gain multi-channel optical frequency comb source 11 and the optical polarization controller 13. The third optical amplifier 12 is used to pre-amplify the optical power of the multi-channel optical frequency comb source 11 and send the amplified multi-channel optical frequency comb source 11 to the optical polarization controller 13.

[0029] Specifically, the optical amplifier acts as a booster amplifier to pre-amplify the optical power of the multi-channel optical frequency comb source 11. The amplified multi-channel optical frequency comb source 11 changes the mode field form of the optical signal in the optical fiber through the optical polarization controller to achieve the highest coupling efficiency between it and the electro-optic modulator 15 (MZM).

[0030] In one embodiment, the optoelectronic modulation unit includes an electro-optical modulator 15 and a programmable optical processor 14. The programmable optical processor 14 is connected to the electro-optical modulator 15. The programmable optical processor 14 carries preset sequence information and sends the preset sequence information to the electro-optical modulator 15. The electro-optical modulator 15 loads the preset sequence information on the polarized light after polarization control to encode the information.

[0031] Specifically, the information encoding here refers to the pre-processed sequence information, such as the NRZ or PAM4 format, which will then be added to the optical channel for transmission. After the transmission is completed, the bit error rate of the transmission process is estimated by demodulating and restoring the received signal.

[0032] Furthermore, the second optical amplifier 22 is used to compensate the power loss of the optical signal passing through the MZM through high gain (for example, in the O band, the insertion loss of the optical signal passing through the MZM is >10 dB, which will seriously affect the subsequent transmission performance of the optical signal).

[0033] The modulated and amplified multi-channel optical signals are transmitted to the wavelength separation module 18 in the form of a point light source via the optical signal transmitter 17. The optical signal transmitter 17 can be completed by using a fiber collimator, which is formed by accurately positioning a pigtail and a lens to convert the transmission light in the optical fiber into a beam of collimated light (parallel light).

[0034] The wavelength separation module 18 separates the incident multi-channel optical frequency comb point light sources into multiple independent single-channel optical frequency comb sources 11. In one embodiment, the wavelength separation module 18 can be implemented by a diffraction grating, a prism or a multi-layer thin film filtering technology.

[0035] In one embodiment, the diffraction grating is a flat glass or metal sheet engraved with a large number of parallel, equal-width, periodic and equidistant slits. The number of slits in the grating is large, and the resolution is tens to thousands per millimeter. When the polychromatic light passes through the grating, it causes the amplitude and / or phase of the incident light to be periodically spatially modulated through a regular structure, and finally the incident light is divided into multiple beam paths by diffraction, so that light of different wavelengths is scattered at different angles in space and finally propagates in different directions, so that spectral lines of different wavelengths appear at different positions to form a spectrum.

[0036] In one embodiment, two adjacent wavelengths output by the wavelength separation module 18 are and Angular spacing between , specifically:

[0037] ;

[0038] in, is the diffraction order, and are two adjacent wavelengths output by the wavelength separation module. is the grating constant, i.e. the distance between adjacent grating lines.

[0039] Specifically, the angle at which a point light source is dispersed after passing through a diffraction grating is related to the wavelength range, grating period, incident angle, etc. In order to more conveniently and accurately detect each separated single-wavelength light source, the wavelength separation module 18 should separate the wavelengths as much as possible, that is, the angle or spacing between two adjacent wavelengths should be as large as possible. Considering the bottleneck of the grating groove process, the present invention can also increase the splitting angle by stacking multiple gratings into a grating array.

[0040] Furthermore, according to the formula of diffraction grating:

[0041] ;

[0042] in, It is The exit angle of the order diffraction, is the diffraction order, is the wavelength of the incident light, is the grating constant, i.e. the distance between adjacent grating lines.

[0043] For two adjacent wavelengths and Angular spacing between , can be written as:

[0044] ;

[0045] From this formula, we can see that the angle difference is proportional to the wavelength difference. The bigger, The larger the angle difference is, the inversely proportional to the grating constant. The smaller the angular spacing between adjacent wavelengths The larger the diffraction order, The higher, The bigger.

[0046] Taking the Ibsen brand O-band commercial grating PING-Sample-106 as an example, when the accuracy of the diffraction grating is 1144 lines per millimeter, the divergence angle of the wavelength range of 1274nm-1346nm is: 1274nm, 43.9 degrees, 1346 nm, 50.9 degrees when the incident angle is 49.9 degrees. That is, the diffraction angle corresponding to each 10nm wavelength range is about 1 degree. If two gratings are superimposed, the diffraction angle is 2 degrees, and so on.

[0047] In addition, when a multi-path optical frequency comb source 11 is projected onto the diffraction grating through the optical signal transmitter 17, the grating should be at least as large as the incident light cone or beam, otherwise the light from the edge will be lost.

[0048] Furthermore, the separated multiple single-wavelength optical signals pass through the free space and then through the optical collimation unit 19. The collimation unit is an optical device based on a plurality of stacked collimating lenses, which is used to collimate and homogenize the incident multiple light beams into mutually parallel optical signals, and ensure that the adjacent optical signals can be collimated and emitted with a precisely fixed spacing.

[0049] The collimated multiple single-wavelength optical signals are then received one by one by a plurality of optical signal receivers 21 after passing through free space. In one embodiment, a single optical signal receiver 21 is composed of a pigtail and a single collimating lens, and the collimating lens is used to focus the received parallel optical signals and transmit them through the pigtail.

[0050] Furthermore, the loss of optical power in free space transmission will be compensated by the second optical amplifier 22. The optical power needs to be amplified to at least +5dBm to be detected by the photodetector 24, and then the optical signal can be tested and demodulated.

[0051] In one embodiment, the system also includes an optical sampling oscilloscope 23 and a real-time optical oscilloscope 25. The optical sampling oscilloscope 23 is connected to the second optical amplifier 22, and the real-time optical oscilloscope 25 is connected to the photodetector 24. The optical sampling oscilloscope 23 is used to collect the amplified received optical signal and generate an eye diagram for display. The photodetector 24 is used to convert the received amplified received optical signal into an electrical signal. The real-time optical oscilloscope 25 is used to display the received electrical signal and complete the calculation of the bit error rate.

[0052] Furthermore, the light amplified in the previous step is tested and verified, which includes using an optical sampling oscilloscope 23 to collect eye diagrams, and using a photodetector 24 and a real-time optical oscilloscope 25 to calculate the bit error rate. The bit error rate is calculated through later programming and algorithms.

[0053] The above-mentioned one-to-many point free-space optical communication system based on an optical frequency comb can obtain a coherent optical signal channel with stable frequency spacing by using a high-gain optical frequency comb source; by using a wavelength separation unit, a single-point light source containing multiple wavelengths can be simply separated to obtain multiple single-wavelength optical signals, and each optical signal will carry the same modulation signal, thereby achieving point-to-multipoint free-space optical signal synchronous transmission; if the optical frequency comb source used has a higher repetition frequency, that is, the interval between adjacent wavelengths is farther, then the single channel can have a higher-speed transmission capability.

[0054] The above is a detailed introduction to a one-to-multipoint free-space optical communication system based on an optical frequency comb provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A one-to-multipoint free-space optical communication system based on optical frequency comb, characterized in that: It includes an optical signal modulation and transmission end and an optical signal receiving and demodulation end, wherein the optical signal modulation and transmission end includes a high-gain multi-channel optical frequency comb source, an optical polarization controller, an optoelectronic modulation unit, a first optical amplifier, an optical signal transmitter, a wavelength separation module and an optical collimation unit connected in sequence, and the optical signal receiving and demodulation end includes an optical signal receiver, a second optical amplifier and a photodetector connected in sequence; A high-gain multi-channel optical frequency comb source is used to generate a series of discrete, equally spaced spectrum, phase-coherent stable light sources, wherein each optical frequency comb in the light source can be used as an independent optical path carrier for communication transmission, thereby realizing simultaneous multi-channel signal transmission of a single device; the multi-channel optical frequency comb source passes through an optical polarization controller to change the mode field form of the optical signal in the optical fiber; the optoelectronic modulation unit is used to load the preset sequence information on the polarized light after polarization control for information encoding; the modulated multi-channel optical signal will pass through the first optical amplifier, and the function of the second optical amplifier is to compensate the power loss of the optical signal through the optoelectronic modulation unit through high gain; the modulated and amplified The completed multi-channel optical signals are transmitted to the wavelength separation module in the form of a point light source via an optical signal transmitter; the wavelength separation module separates the incident multi-channel optical frequency comb point light sources into multiple independent single-channel optical frequency comb sources one by one; the separated multiple single-wavelength optical signals pass through the free space and then pass through the optical collimation unit to collimate and homogenize the incident multiple light beams into mutually parallel optical signals; the collimated multiple single-wavelength optical signals are then received one by one by a number of optical signal receivers after passing through the free space; the loss of optical power in free space transmission will be compensated by the second optical amplifier; the photodetector functions to convert the received amplified optical signal into an electrical signal.

2. The system according to claim 1, characterized in that The optical signal modulation and transmission end also includes a third optical amplifier arranged between the high-gain multi-channel optical frequency comb source and the optical polarization controller. The third optical amplifier is used to pre-amplify the optical power of the multi-channel optical frequency comb source and send the amplified multi-channel optical frequency comb source to the optical polarization controller.

3. The system according to claim 2, characterized in that The optoelectronic modulation unit includes an electro-optical modulator and a programmable optical processor. The programmable optical processor is connected to the electro-optical modulator. The programmable optical processor carries preset sequence information and sends the preset sequence information to the electro-optical modulator. The electro-optical modulator loads the preset sequence information on the polarized light after polarization control to encode the information.

4. The system according to claim 3, characterized in that The overall optical output power of the high-gain multi-channel optical frequency comb source is at least +10dBm, and the spectral operating wavelength is 1310±10 nm; when the repetition frequencies of the optical frequency comb source are 25GHz, 50GHz, 100GHz and 200GHz, respectively, the spacings between adjacent optical combs are at least 0.14nm, 0.28nm, 0.56nm and 1.12nm, respectively.

5. The system according to claim 4, characterized in that The wavelength separation module can be realized by diffraction grating, prism or multi-layer thin film filtering technology.

6. The system according to claim 5, characterized in that A diffraction grating is a flat glass or metal sheet engraved with a large number of parallel, equal-width, periodic and equidistant slits. The number of slits in the grating is very large, and the resolution is from tens to thousands per millimeter. When the complex light passes through the grating, it passes through the regular structure, causing the amplitude and / or phase of the incident light to be periodically spatially modulated, and finally the incident light is divided into multiple beam paths by diffraction, so that light of different wavelengths is scattered at different angles in space and finally propagates in different directions. Therefore, spectral lines of different wavelengths will appear at different positions to form a spectrum.

7. The system according to claim 6, characterized in that The two adjacent wavelengths output by the wavelength separation module and Angular spacing between , specifically: ； in, is the diffraction order, and are two adjacent wavelengths output by the wavelength separation module. is the grating constant, i.e. the distance between adjacent grating lines.

8. The system according to claim 7, characterized in that The optical signal transmitter is composed of a pigtail and a lens precisely positioned to convert the transmission light in the optical fiber into a beam of collimated light.

9. The system according to claim 8, characterized in that A single optical signal receiver is composed of a pigtail fiber and a single collimating lens, and the collimating lens is used to focus the received parallel optical signal and transmit it via the pigtail fiber.

10. The system according to claim 9, characterized in that It also includes an optical sampling oscilloscope and a real-time optical oscilloscope. The optical sampling oscilloscope is connected to the second optical amplifier, and the real-time optical oscilloscope is connected to the photodetector. The optical sampling oscilloscope is used to collect the amplified received optical signal and generate an eye diagram for display. The photodetector is used to convert the received amplified received optical signal into an electrical signal. The real-time optical oscilloscope is used to display the received electrical signal and complete the calculation of the bit error rate.

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