CN109412698B - Multi-input multi-output optical communication system and communication method based on diffraction effect - Google Patents
Multi-input multi-output optical communication system and communication method based on diffraction effect Download PDFInfo
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Abstract
The invention discloses a multi-input multi-output optical communication system based on diffraction effect, which comprises an optical signal transmitting end and an optical signal receiving end, wherein the optical signal transmitting end comprises a light intensity modulator and an optical signal transmitting array connected with the light intensity modulator, the optical signal receiving end comprises a first collimating device, a dispersion device, a second collimating device, a detector and a signal processing unit connected with the detector, the dispersion device can enable signal light emitted by each light source in a signal transmitting area to generate diffraction effect, and the light intensity angle distributions of diffracted light emitted by the signal light with the same frequency and the same intensity incident to different positions of the dispersion device are different. The invention uses light source to form light signal sending array to transmit multi-channel signal, and uses dispersion device and array detecting chip to solve matrix equation or linear equation to recover multi-channel signal. The illumination function can be realized, and simultaneously, the transmission of large-capacity signals can be realized, and the structure is simple and the cost is low.
Description
Technical Field
The invention relates to an optical communication system based on diffraction effect and a signal sending and decoding method thereof, belonging to the technical field of optical communication.
Background
Visible Light Communication (VLC) is a method in which an electric signal is converted into an optical signal by a driving circuit and emitted through a Light Emitting Diode (LED), and a receiving end receives the optical signal through a photo detection device and extracts useful signal components therein, thereby implementing Communication. The visible light communication technology can directly transmit optical signals in the air without transmission media of wired channels such as optical fibers and the like. The visible light communication technology is green and low-carbon, can realize nearly zero-energy-consumption communication, can effectively avoid the defects of leakage of radio communication electromagnetic signals and the like, and quickly constructs an anti-interference and anti-interception safety information space.
In order to further improve the signal transmission capacity of the visible light communication technology, many groups of problems have been tried to combine a Multiple-Input Multiple-Output (MIMO) radio transmission technology with the visible light communication technology. MIMO is an important technological breakthrough in the field of communications, and it can improve the capacity of wireless communication systems by a multiple without increasing bandwidth and power. MIMO technology, which transmits independent data streams at different transmission sources to achieve high-speed high-capacity data transmission, is one of the key technologies in the new generation of wireless communication systems.
The VLC-MIMO technology has great market application prospect, but has some problems. Such as: (1) in the traditional MIMO visible light communication technology, different signal light sources with different single frequencies are adopted in different channels, but the light sources are single in color, and a white light source used in traditional illumination cannot be adopted. (2) Some VLC-MIMO techniques may use white light sources, but require that the frequency spectrums of each white light source overlap but are not completely the same, so that how many channels require how many different light sources or filtering films, thereby increasing the cost of the system. (3) Some VLC-MIMO technologies adopt a two-dimensional code technology to perform signal coding, but the coding rule of the two-dimensional code is complex, so that special requirements are imposed on light source arrangement, and signal emission light sources can only adopt point light sources but cannot adopt surface light sources, so that the comfort level of human eyes is reduced. (4) In the technologies adopted by some groups of subjects, the light emitting end needs to precisely control the wavelength and polarization state of the optical carrier or the transmission mode of the incident optical fiber, and the light receiving end needs to adopt a detector with a large volume and place a specific angle, or adopt a complex demultiplexer to separate the wavelength, polarization state and transmission mode to recover the transmission data, so the system structure is complex and the cost is high. In order to overcome the above disadvantages, we propose a new type of mimo communication system based on diffraction effect and its communication method.
Disclosure of Invention
The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and to provide a multiple-input multiple-output optical communication system based on diffraction effect and a communication method thereof.
The invention specifically adopts the following technical scheme to solve the technical problems:
a multi-input multi-output optical communication system based on diffraction effect comprises an optical signal transmitting end and an optical signal receiving end:
the optical signal transmitting end comprises an optical intensity modulator and an optical signal transmitting array connected with the optical intensity modulator, the optical signal transmitting array comprises m × n light sources, wherein each n light sources are distributed in one signal transmitting area, the optical signal transmitting array has m signal transmitting areas, the spectrum frequency ranges of the n light sources in each signal transmitting area can be mutually overlapped but the spectrums are not completely the same, the spectrums of any two light sources belonging to different signal transmitting areas can be the same, the optical intensity modulator modulates m × n signals onto optical carriers transmitted by the m × n light sources respectively to generate corresponding optical modulation signals, and modulates different signals at different moments, wherein m and n are integers more than 1;
the optical signal receiving end comprises a first collimating device, a dispersion device, a second collimating device, a detector and a signal processing unit connected with the detector, wherein the first collimating device is positioned in front of the dispersion device, the first collimating device can enable light transmitted along the direction of a connecting line from an optical signal transmitting array to the dispersion device to pass through and filter light transmitted along other directions, and enable signal light emitted from different signal transmitting areas to pass through the first collimating device and then to be emitted to different parts of the dispersion device, the dispersion device can enable the signal light emitted by each light source of the signal transmitting areas to generate diffraction effects, the light intensity distribution of diffracted light emitted by the signal light with the same frequency and the same intensity and incident to different positions of the dispersion device is different, and the detector is an array type detection chip consisting of at least m multiplied by n optical detection pixel elements with the same spectral response, the array type detection chip is provided with at least m signal receiving areas, wherein any signal receiving area is provided with at least n optical detection pixel elements, the light detection pixel element is responsive to signal light incident on the photosensitive surface of the pixel element, the second collimating device is positioned between the dispersive device and the detector, the second collimating device can make light transmitted along the direction from the dispersive device to the detector pass through, and can filter light transmitted along other directions, and the signal lights emitted by different areas of the optical signal transmitting array can be projected on the optical detection pixel elements in different signal receiving areas of the detector respectively after passing through the dispersion device, the signal processing unit respectively analyzes and processes data detected by pixel elements in different signal receiving areas, and finally performs data analysis and processing through the signal processing unit, and the signals sent by the optical signal transmitting end are obtained through decoding.
Preferably, the first collimating device includes a first convex lens, a first aperture stop and a second convex lens, and the first aperture stop gap is disposed at a common focus between the first convex lens and the second convex lens.
Preferably, the optical signal receiving end further comprises an optical wavelength conversion component arranged before or after the dispersive device, the optical wavelength conversion component comprises a wavelength conversion layer, the wavelength conversion layer comprises at least one wavelength conversion optical material, part or all of the absorption spectrum of the wavelength conversion optical material exceeds the detection range of the array detection chip, and the emission spectrum of the wavelength conversion optical material is all in the detection range of the array detection chip; the wavelength conversion optical material is any material having the characteristics of absorbing light with one wavelength and emitting light with other different wavelengths, such as an up-conversion luminescent material or a down-conversion luminescent material, or the combination of the materials.
Preferably, the second collimating device includes a third convex lens, a second aperture stop and a fourth convex lens, and the second aperture stop is disposed at a common focus between the third convex lens and the fourth convex lens.
Preferably, the dispersive device comprises a series of diffraction holes or slits built into the opaque light-blocking layer on one of the surfaces of the transparent substrate, the series of diffraction holes or slits having different aperture size or different slit width and being randomly distributed in the light-blocking layer, the depth of each diffraction hole or slit being the same as the thickness of the light-blocking layer.
Preferably, each diffraction hole or diffraction slit in the dispersive device has an aperture size or slit width close to the signal light wavelength, ranging between 0.3 and 5 times the signal light wavelength.
Preferably, each signal transmitting area of the optical signal transmitting end includes n light sources with the same emission spectrum, and each light source is respectively attached with filter films with different transmission spectra.
Preferably, a visible band white light source is used when the light source is required for illumination purposes, and a mid-infrared band light source is used when the light source is not required for illumination purposes.
The method for sending and decoding the communication signal of the optical communication system according to any one of the above technical solutions includes the following steps:
step 1: suppose that at a time t, n light sources in m signal transmission regions are modulated by a light intensity modulator to transmit a signal S'1,S’2,…S’m×nThe emitted signals are distinguished by the intensity of light;
step 2: suppose n of these signal transmission regionsThe signal emitted by the light source modulated by the light intensity modulator is S'1,S’2,…S’n；
And step 3: the detector receives light emitted by the light signal emitting end, wherein the signal light emitted by the kth signal sending area passes through a signal transmission space, then sequentially passes through the first collimating device, the dispersion device, the light wavelength conversion component and the second collimating device or sequentially passes through the first collimating device, the dispersion device and the second collimating device at the light signal receiving end, finally irradiates on the light detection pixel elements in the signal receiving area corresponding to the signal sending area, and the light intensities received by at least n light detection pixel elements in the signal receiving area corresponding to the signal sending area in the step 2 at the moment t are set as I respectively1,I2,…In,…；
And 4, step 4: respectively removing noise from the light intensity received by each light detection pixel element in the signal receiving area corresponding to the signal sending area in the step 3, and then substituting the light intensity into each row unit of the amplification matrix of the matrix equation, and respectively substituting the ratio of the value detected by each light detection pixel element under the condition that each light source in the signal sending area is independently lighted to the emission intensity of the lighted light source, and the ratio of the value to the emission intensity of the lighted light source, after the noise is removed, into each row unit of the coefficient matrix of the matrix equation, because the data of each unit of the coefficient matrix can be measured in advance through experiments, the signal S can be obtained by solving the matrix equation1,S2,…Sn；
And 5: get S1,S2,…SnThe average value of the n values is used as a judgment threshold, and S is used1,S2,…SnComparing with the decision threshold, setting the value to be 1 when the value is larger than the decision threshold, and setting the value to be 0 when the value is smaller than the decision threshold, so that the actual signals S 'transmitted by n light sources in a certain signal transmitting area of the optical signal transmitting end at the moment t can be obtained at the optical signal receiving end'1,S’2,…S’n；
Step 6: respectively substituting the data measured by the optical detection pixel elements in each signal receiving area corresponding to each signal sending area in the step 1 into each matrix equation, and respectively repeating the steps2-5, namely, the signal S 'is received at the optical signal receiving end by solving m matrix equations'1,S’2,…S’m×n；
And 7: different signals are modulated at different moments through the light intensity modulator, and the signals sent by the light signal transmitting end at different moments can be received at the light signal receiving end.
Preferably, in the step 4, the matrix equation may be solved by one of a convex optimization algorithm, a Tikhonov regularization algorithm, an L1 norm regularization algorithm, a genetic algorithm, a cross direction multiplier method, and a simulated annealing algorithm, or other known or unknown mathematical optimization methods may be used to solve the matrix equation to reduce the error rate of the signal.
Compared with the prior art, the invention has the following beneficial effects:
1. the transmission of large-capacity signals can be realized while lighting. The optical signal transmitting end adopts a series of light sources with a certain frequency range, the comfort level to human eyes is higher compared with a visible band light source with a single frequency, and the number of the light sources is not limited by the total bandwidth of the visible band light source and the infrared band light source because the spectrum frequency bands of the light sources can be overlapped.
2. The device structures of the signal transmitting end and the signal receiving end of the system are simple and easy to realize. The invention does not need a multiplexing and demultiplexing optical device with larger volume and complex structure, the light source and the array type detection chip are both provided with mature products, the optical signals are transmitted through a shared channel through reasonable design, and the matrix equation is solved to obtain the repeated emission signals through measuring the channel transmission matrix of the multi-input and multi-output optical communication system in advance.
3. The invention combines the frequency division multiplexing and space division multiplexing technologies, thereby reducing the system cost to the maximum extent and improving the channel capacity. The light sources with different spectrums in each signal sending area are used for transmitting signals loaded on different light sources, and the light detection pixel elements at different positions of the signal receiving end can measure different diffraction light intensity signals, so that an original emission signal can be obtained by solving a matrix equation, and meanwhile, the spectrums of any two light sources belonging to different signal sending areas can be the same, so that the system cost is low. And the multipath signal light is emitted simultaneously, so that the communication capacity is improved.
4. When the system is not needed to be used for illumination, an infrared band light source can be adopted for signal communication, the defect that the traditional visible light communication system needs to carry out illumination during communication is overcome, and particularly, the defect that an ordinary silicon-based CCD or CMOS array type detection chip cannot detect infrared band light can be overcome when an optical wavelength conversion part is adopted at a signal receiving end of the system. Therefore, the system can detect visible light signals and infrared band light signals by adopting the common silicon-based CCD, thereby improving the system performance and further reducing the cost for constructing the system.
Drawings
FIG. 1 is a schematic diagram of the optical communication system of the present invention;
FIG. 2 is a schematic cross-sectional view of a circular hole type dispersion device;
FIG. 3 is a schematic cross-sectional view of a slit-type dispersive device;
FIG. 4 is a graph of the spectra of 9 different light sources
The reference numerals in the figures have the following meanings:
1 is a first signal sending area in the optical signal sending array, 2 is a second signal sending area in the optical signal sending array, 3 is a third signal sending area in the optical signal sending array, 4 is a fourth signal sending area in the optical signal sending array, 5 is an mth signal sending area in the optical signal sending array, 6 is a first dispersion part in the dispersion device, 7 is a second dispersion part in the dispersion device, 8 is a third dispersion part in the dispersion device, 9 is a fourth dispersion part in the dispersion device, 10 is an mth dispersion part in the dispersion device, 11 is a first signal receiving area on the array detection chip, 12 is a second signal receiving area on the array detection chip, 13 is a third signal receiving area on the array detection chip, 14 is a fourth signal receiving area on the array detection chip, and 15 is an mth signal receiving area on the array detection chip, 16 is a light intensity modulator, 17 is a light signal transmitting array, 18 is signal light transmitted in a signal transmission space, 19 is a first convex lens, 20 is a second convex lens, 21 is a third convex lens, 22 is a fourth convex lens, 23 is a first aperture diaphragm, 24 is a second aperture diaphragm, 25 is a detector, 26 is a light wavelength conversion component, 27 is a certain signal transmitting area in the light signal transmitting array, 28 is a light signal transmitting end, 29 is a light signal receiving end, 30 is a first collimating device, 31 is a second collimating device, and 32 is a dispersive device.
Detailed Description
The invention can use the LED light source which is easy to obtain and low in cost to form the optical signal sending array 17 to carry out the parallel transmission of the multi-channel signals, and uses the method of combining the dispersion device 32 and the detector 25 (such as CCD, CMOS and the like) and solving the matrix equation or the linear equation set to recover the transmitted multi-channel signals. The light source adopted by the invention can be used for communication and illumination at the same time, and can only realize any function. The following is a description of preferred embodiments by way of illustration and explanation without limitation. The embodiments are merely exemplary for applying the technical solutions of the present invention, and any technical solution formed by replacing or converting the equivalent thereof falls within the scope of the present invention claimed.
Fig. 1 shows a basic structure of a MIMO optical communication system of the present invention. As shown in fig. 1, a multiple-input multiple-output optical communication system based on diffraction effect includes an optical signal transmitting end and an optical signal receiving end. The optical signal transmitting terminal 28 includes an optical intensity modulator 16 and an optical signal transmitting array 17 connected thereto. The optical signal transmitting array comprises m × n light sources, m and n are integers greater than 1, and the value ranges of m and n can be thousands of light sources. Each n light sources in the optical signaling array 17 are distributed within one signaling region 27, and the signaling region 27 may be a first signaling region 1 of the m signaling regions, or may be a second signaling region 2, a third signaling region 3, a fourth signaling region 4 …, or an m-th signaling region 5. The spectrum frequency bands of the n light sources in each signal transmission area can be mutually overlapped but the spectrums are not completely the same, and the spectrums of any two light sources belonging to different signal transmission areas can be the same. The light intensity modulator 16 modulates the mxn signals onto optical carriers emitted by the mxn light sources, respectively, to generate corresponding optical modulation signals. The m × n light sources respectively transmit m × n optical signals at a certain time, and each light source transmits one of the optical signals. And the light intensity modulator modulates different signals at different moments. The signal light 18 modulated by these signals is transmitted through the "signal transmission space" and finally received by the optical signal receiving end 29. The signal transmission space is air in this embodiment, and may also be water, silicon dioxide, or other medium capable of transmitting light. The optical signal receiving end 29 includes a first collimating device 30, a dispersing device 32, a second collimating device 31, a detector 25, and a signal processing unit (not shown in fig. 1) connected to the detector 25, the first collimating device 30 is located in front of the dispersing device 32, and is capable of passing light transmitted along a direction from the optical signal transmitting array 17 to the dispersing device 32, filtering light transmitted along other directions, and making the signal lights 18 emitted from different signal transmitting areas 27 pass through the first collimating device 30 and then reach different positions of the dispersing device 32, the dispersing device 32 is capable of making the signal lights emitted from the light sources in the signal transmitting areas generate a diffraction effect, and the light intensity angle distributions of the diffracted lights emitted from different positions where the signal lights with the same frequency and the same intensity enter the dispersing device 32 are different from each other. The detector 25 is an array-type detection chip composed of at least m × n light detection pixel elements with the same spectral response. In this embodiment, the detector is a silicon-based CCD, and each pixel element of the CCD has the same spectral response characteristic, that is, when light with the same wavelength and the same intensity is incident on the pixel element, the data output by each pixel element is the same. The photosensitive area of the CCD is divided into m signal receiving areas, i.e., a first signal receiving area 11, a second signal receiving area 12, a third signal receiving area 13, and a fourth signal receiving area 14 …, i.e., an mth signal receiving area 15, where at least p photodetecting pixel elements (p is not less than n, p is an integer, and the value range of p may be thousands of) are provided in any signal receiving area, and the photodetecting pixel elements respond to signal light incident on the photosensitive surface of the photodetecting pixel elements. The second collimating device 31 is located between the dispersing device 32 and the detector 25, and can pass light transmitted along the line from the dispersing device 32 to the detector 25, and filter out light transmitted along other directions, and can make signal lights emitted from different regions of the optical signal transmitting array 17 project onto optical detection pixel elements in different signal receiving regions of the detector 25 after passing through the dispersing device 32. The signal processing unit is connected to the detector 25 and analyzes and processes the data detected by the pixel elements in the different signal receiving areas of the detector 25. The pixel metadata in different signal receiving areas are substituted into different matrix equations, the matrix equations are solved, and finally the signals sent by the optical signal transmitting end are obtained through decoding.
In this technical solution, the preferable device structure of the first collimating device 30 includes a first convex lens 19, a first aperture stop 23, and a second convex lens 20, and the first aperture stop 23 is disposed at a common focus between the first convex lens 19 and the second convex lens 20 in a clearance manner. The first collimating device 30 may also have other structures, and in this technical solution, the specific structure of the first collimating device is not limited, as long as the light emitted from different signal transmitting regions can be emitted to different parts of the dispersive device. A
In this technical solution, the preferable device structure of the second collimating device 31 includes a third convex lens 21, a second aperture stop 24, and a fourth convex lens 22, where the second aperture stop 24 is disposed at a common focus between the third convex lens 21 and the fourth convex lens 22 in a gap manner. The second collimating device 31 may also have other structures, and in this technical solution, the specific structure of the second collimating device is not limited, as long as light along the direction from the dispersive device to the detector can pass through, and light transmitted along other directions is filtered out, and signal light emitted from different regions of the optical signal transmitting array can be projected onto optical detection pixel elements in different signal receiving regions of the detector after passing through the dispersive device.
The dispersion device 32 used in the present invention may adopt an existing or future structure, as long as the signal lights emitted by the light sources in the signal transmission area are caused to generate diffraction effect, and the light intensity angle distributions of the diffracted lights emitted from different positions where the signal lights with the same frequency and the same intensity enter the dispersion device 32 are different from each other. The dispersive device 32 generally adopts a simple and easy-to-manufacture structure, and fig. 2 and 3 are schematic structural diagrams of a circular hole type dispersive device and a slit type dispersive device, respectively. The dispersion device is formed by a series of diffraction holes or diffraction slits in an opaque light blocking layer constructed on one surface of a transparent substrate, wherein the series of diffraction holes or diffraction slits have different aperture sizes or different slit widths and are randomly distributed in the light blocking layer, and the depth of each diffraction hole or diffraction slit is the same as the thickness of the light blocking layer. According to the formula of circular hole diffraction or slit diffraction, the angular distribution of the diffracted light intensity is related to the wavelength of the incident light and the aperture size or slit width size, so that each pixel element in the array type detection chip CCD in the following array type detection chip CCD can detect different diffracted light intensity, the data measured by each pixel element in a certain signal receiving area (11 or 12 or 13 or 14 or … 15) of the array type detection chip CCD can be substituted into the amplification matrix of the matrix equation, the signal emitted by a certain signal transmitting area (1 or 2 or 3 or 4 or … 5) can be recovered by solving the matrix equation through the coefficient matrix (also called channel transmission matrix) data of the matrix equation measured in advance, then the data of the pixel elements in different areas (11, 12, 13, 14, … 15) of the CCD can be substituted into different matrix equations respectively, and the series of matrix equations can be solved, the signal transmitted by the entire optical signal transmitting terminal 28 is available at the optical signal receiving terminal 29.
The present invention may also provide a light wavelength conversion member 26 before or after the dispersion device 32, the light wavelength conversion member 26 including a wavelength conversion layer containing at least one wavelength conversion optical material therein; the wavelength converting optical material has a partial or full absorption spectrum outside the detection range of the detector 25 (e.g. CCD) and an emission spectrum all within the detection range of the detector 25. In order to ensure that the light-detecting pixel elements in detector 25 respond to the signal light incident on the photosensitive surface of the pixel elements, the frequency range of the spectrum of the light emitted by each light source in light signal emitting end 28 must be within the detection range of light signal receiving end 29. The detection range of the optical signal receiving end 29 is defined as follows: the maximum and minimum frequency values are selected from the absorption spectra of all the wavelength conversion optical materials included in the optical wavelength conversion member 26 and the frequency range detectable by the detector 25, and the frequency range between the maximum and minimum frequency values is the detection range of the optical signal receiving end. The wavelength converting material is any material having the property of absorbing light at one wavelength and emitting light at another wavelength, or a combination of these materials. For example, the wavelength conversion material may be an up-conversion luminescent material or a down-conversion luminescent material. The up-converting luminescent material and the down-converting luminescent material are explained below: stokes law states that some materials can be excited by high-energy light to emit light with low energy, in other words, light with high excitation wavelength and low excitation wavelength and with short wavelength, such as ultraviolet light, can emit visible light, and such materials are down-conversion luminescent materials. In contrast, some materials can achieve a luminescence effect exactly opposite to the above-mentioned law, and we call it anti-stokes luminescence, also called up-conversion luminescence, such materials are called up-conversion luminescent materials.
The optical wavelength conversion component 26 adopted by the invention can be arranged before or after the dispersion device, so that the communication method disclosed by the invention can be used for optical communication in a non-visible light frequency range, and the defect that the traditional visible light communication needs to adopt visible light for illumination is overcome. However, considering that the emission spectrum of most existing wavelength conversion luminescent materials is narrow, in order to make the difference of the light intensity distribution of the light with different frequencies on the surface of the array type detection chip (such as a CCD) more obvious after the light passes through the dispersion device 32, thereby being beneficial to recovering the emitted signal at the signal receiving end by a method of solving a matrix equation, the invention preferably arranges the light wavelength conversion component 26 behind the dispersion device 32, namely, between the dispersion device 32 and the array type detection chip. Each diffracted light beam transmitted from the dispersion device 32 passes through one optical wavelength conversion component and then passes through the second optical collimating device 31 to respectively reach the mth pixel area 15 of the first pixel area 11, the second pixel area 12, the third pixel area 13 and the fourth pixel area 14 … of the subsequent array type detection chip.
The wavelength conversion optical material can adopt various existing up-conversion or down-conversion materials, and the wavelength detection range of a signal receiving end of an optical communication system can be effectively expanded as long as the partial or all absorption spectra of the up-conversion or down-conversion materials exceed the detection range of the array type detection chip and the emission spectra are all in the detection range of the array type detection chip. For example, the type HCP-IR-1201 mid-infrared display card produced by the Longcai technology (HCP) is made of an up-conversion luminescent material, visible light can be excited by 0.3mW infrared light irradiation, the effective light excitation wave band is mainly 700 nm-10600 nm, and the luminous intensity and the excitation power are in a direct increase relationship. If the array type detection chip adopts a CCD chip with the model number of SONY-ICX285AL, the detection wave band is about 400 nm-1000 nm, so the intermediate infrared display card is adopted as the optical wavelength conversion component, the wavelength detection range of the signal receiving end of the optical communication system can be expanded to about 400 nm-10600 nm, and is wider than the wavelength detection range of the silicon-based CCD.
A down-conversion optical Material (MOF) Eu3(MFDA)4(NO3) (DMF)3(H2MFDA ═ 9,9-dimethylfluorene-2, 7-dicarboxydic acid) [ Xinhui Zhou et al, a microporus luminescence emission spectrum metal-organic frame for nitro-amplified sensitive, Dalton trans, 2013,42, 5718-bellmouth 5723] with an absorption spectrum range of about 250nm to 450nm and an emission spectrum range of about 590nm to 640nm may also be used, and if the array detection chip is a CCD chip of type SONY-ICX285AL with a detection band of about 400nm to 1000nm, the wavelength conversion component made of the down-conversion optical material may be used to extend the wavelength range of the signal receiving end of the optical communication system to about 250nm, which is larger than the silicon-based detection wavelength range of about 1000 nm.
The optical wavelength conversion component is not a necessary device, and when the optical signal receiving end of the optical communication system does not adopt the optical wavelength conversion device, the wavelength detection range of the optical signal receiving end of the optical communication system is the wavelength response range of the adopted array detection chip. The purpose of using the optical wavelength conversion member is only to expand the wavelength detection range of the detector at the signal receiving end of the optical communication system, but signal communication can also be performed by selecting a suitable light source and detector without the optical wavelength conversion member. The purpose of using the optical wavelength conversion member is: firstly, the existing and common light source and the array type detection chip can be adopted by the light signal transmitting end and the detector, so that the cost for purchasing the special light source and the array type detection chip can be saved, and the wavelength detection range of the array type detection chip does not need to contain the transmitting wavelength of the light source; secondly, the same array type detection chip can be used for detecting visible light and can also be used for detecting light in a non-visible light wave band, so that the communication system can be used for communication by using the visible light as a carrier and can also be used for communication by using the non-visible light as a carrier, and the same set of signal receiving end can be used for communication by using the two communication carriers, so that the communication can be carried out under the condition that the visible light is not required for illumination.
The following summarizes the communication process of the communication system of this embodiment: under the action of the optical intensity modulator 16, the optical signal transmitting array 17 emits signal beams from the signal transmitting regions (the first signal transmitting region 1, the second signal transmitting region 2, the third signal transmitting region 3, the fourth signal transmitting region 4, and the m-th signal transmitting region 5 …), these beams pass through the first optical collimating device 30 and are projected to the positions on the surface of the dispersive device 32, the dispersive device 32 can cause diffraction effect between the incident lights, and the diffracted beams transmitted from the dispersive device 32 pass through the optical wavelength conversion component 26 and then pass through the second optical collimating device 31 to the first signal receiving region 11, the second signal receiving region 12, the third signal receiving region 13, and the m-th signal receiving region 15 of the fourth signal receiving region 14 …, and are detected by the pixels in the signal receiving regions, and finally, the signal processing unit analyzes and processes the data measured by each pixel element.
The above method for transmitting and decoding signals of an optical communication system based on diffraction effect is described in detail as follows:
step 1: suppose that at a time t, n light sources in m signal transmission regions are modulated by a light intensity modulator to transmit a signal S'1,S’2,…S’m×nWhere m and n are integers, the emitted signals are distinguished by the intensity of the light, such as: "the signal" 1 "is represented by" the light source emits light or the light intensity is greater than a certain threshold "," the signal "0" is represented by "the light source does not emit light or the light intensity is less than a certain threshold";
step 2: suppose that the signals emitted by the n light sources in the k-th signal transmission region and modulated by the light intensity modulator are S'1,S’2,…S’nAbove k is an integer between 1 and m;
and step 3: the detector receives light emitted by the light signal emitting end, wherein the signal light emitted by the kth signal sending area passes through a signal transmission space, then sequentially passes through the first collimating device, the dispersion device, the optical wavelength conversion component (which can be omitted) and the second collimating device at the signal receiving end, finally reaches the optical detection pixel elements in the signal receiving area corresponding to the signal sending area, and the light intensities received by the p optical detection pixel elements in the signal receiving area corresponding to the kth signal sending area at the moment t are respectively set as I1,I2,…IpWherein p is more than or equal to n, p is an integer, and the value range of p can be thousands of;
for explaining the signal receiving area corresponding to the signal transmitting area in detail, as shown in fig. 1, the signal light emitted from the first signal transmitting area 1 passes through the first dispersion part 6 of the dispersion device and finally reaches the first signal receiving area 11 of the array type detection chip, so that the first signal transmitting area 1 corresponds to the first signal receiving area 11; the signal light emitted by the second signal sending area 2 finally reaches the second signal receiving area 12 of the array type detection chip after passing through the second dispersion part 7 of the dispersion device, so that the second signal sending area 2 corresponds to the second signal receiving area 12; the signal light emitted by the third signal sending area 3 finally reaches a third signal receiving area 13 of the array type detection chip after passing through a third dispersion part 8 of the dispersion device, so that the third signal sending area 3 corresponds to the third signal receiving area 13; the signal light emitted by the fourth signal sending area 4 finally reaches the fourth signal receiving area 14 of the array type detection chip after passing through the fourth dispersion part 9 of the dispersion device, so that the fourth signal sending area 4 corresponds to the fourth signal receiving area 14; by analogy, the signal light emitted by the mth signal sending area 5 passes through the mth dispersion part 10 of the dispersion device and finally reaches the mth signal receiving area 15 of the array type detection chip, so that the mth signal sending area 5 corresponds to the mth signal receiving area 15. By adopting the optical signal transmitting end and the optical signal receiving end, light in any signal transmitting area of the optical signal transmitting array can only be projected into one signal receiving area of the corresponding detector, and can not be projected into other signal receiving areas.
And 4, step 4: the method comprises the steps of removing noise from light intensity received by each light detection pixel element in a signal receiving area corresponding to a kth signal sending area, substituting the light intensity into each row unit of an amplification matrix of a matrix equation, substituting the ratio of the value detected by each light detection pixel element under the condition that each light source in the signal sending area is independently lighted to the emission intensity of the lighted light source, after the noise is removed, into each unit of each row of a coefficient matrix of the matrix equation, wherein the data of each unit of the coefficient matrix can be measured in advance through experiments, and therefore the signal S can be obtained by solving the matrix equation1,S2,…Sn；
For the purpose of detailed description, it is assumed that p light detection pixel elements (p) are located in the signal receiving region corresponding to the kth signal transmission region at time t>n, where p is an integer) are respectively I1,I2,…IpSolving the following matrix equation to obtain S through one of mathematical optimization algorithms such as a convex optimization algorithm, a Tikhonov regularization algorithm, an L1 norm regularization algorithm, a genetic algorithm, a cross direction multiplier method, a simulated annealing algorithm and the like or improvement methods thereof1,S2,…Sn。
In the formula, one element H in the channel transmission matrix Hij(i-1, 2 … p) (j-1, 2 … n) represents the transmission coefficient of the optical signal emitted by the jth light source in the kth signal transmission area through the transmission space of the MIMO optical communication system and received by the ith pixel element in the CCD, i.e. the ratio of the intensity of the optical signal emitted by the jth light source in the kth signal transmission area through the MIMO optical communication system and detected by the ith pixel element in the CCD to the intensity of the light source emission minus the background noise. For a specific MIMO optical communication system, the channel transmission matrix H is uniquely determined, and each element in the channel transmission matrix, i.e., the transmission coefficient, can be obtained in advance through experiments and can be substituted into the matrix equation.
And 5: get S1,S2,…SnThe average value of the n values is used as a judgment threshold, and S is used1,S2,…SnComparing the actual signals S 'transmitted by the n light sources in the kth signal sending area of the optical signal transmitting end at the time t with the judgment threshold, setting the actual signals S' to be greater than the judgment threshold to be 1, and setting the actual signals S 'to be less than the judgment threshold to be 0'1,S’2,…S’n；
Step 6: k is taken from 1 to m, namely, the data measured by the optical detection pixel elements in each signal receiving area are respectively substituted into each matrix equation, and the steps 2-5 are respectively repeated, so that the signal S 'can be received at the optical signal receiving end by solving m matrix equations'1,S’2,…S’m×n；
And 7: different signals are modulated at different moments through the light intensity modulator, and the signals sent by the light signal transmitting end at different moments can be received at the light signal receiving end.
From the above principle and steps, the maximum signal transmission rate of the communication system is limited by the frame rate of the array type detection chip, the response rate of the light source, the modulation rate of the light intensity modulator, the total number of light sources at the light signal emitting end, and the like. Generally, although the signal transmission rate can be increased to increase the amount of signal transmission per unit time, the error rate is also increased.
The optical communication system does not need to use complex and expensive multiplexing and demultiplexing optical devices, wherein the light source can adopt the most common LED light source, and if light sources with different emission spectra are needed, different filter films or filter covers are only needed to be attached to the rear parts of the same LED light sources; the dispersion device has simple structure and various forms, and can be prepared by adopting the existing simple and mature process; the light detector array can directly adopt a mature CCD or CMOS device. Therefore, the MIMO optical communication system has lower realization cost.
Different from the traditional wavelength division multiplexing or frequency division multiplexing optical communication system, the light source in the invention can adopt a broadband light source, the spectrums of the light sources belonging to different signal sending areas in the signal sending end are not required to be different from each other, and the spectrum frequency bands of the light sources in the same signal sending area can be overlapped with each other. For example, a signal sending end needs to transmit 72 paths of signals at the same time, m may be 8, and n may be 9, at this time, 8 signal sending areas are total, 9 LEDs are provided in each signal sending area, and the 72 paths of signals are loaded onto 72 LED light sources respectively through a light intensity modulator. The spectra of the 72 LED light sources are not required to be completely different, and only 9 light sources with different spectral curves (the spectral curves are shown in fig. 4) may be used to form one signal transmission region, while the other signal transmission regions use the same 9 light sources. And, 9 light sources with different spectral curves in the same signal sending region can also be obtained by adopting 9 LEDs with the same type and attaching different filter films or filter covers behind the LEDs, so that 9 different emission spectra can be obtained.
Take the example of using 9 different types of LED light sources. In fig. 4, the abscissa is wavelength and the ordinate is normalized spectral power, and the curves in the graph represent spectral curves of different LED light sources. The 9 LED light sources are in the same signal sending area, the other signal sending areas adopt the same 9 LED light sources, the total number of the signal sending areas is 8, therefore, the 9 LED light sources are divided into 8 groups, and the 72 LED light sources form an LED light source array to send 72 signals at the same time. The CCD array of the signal receiving end is provided with millions of pixel elements, and the pixel elements are divided into 8 signal detection areas, so that data measured by the pixel elements in the 8 signal detection areas can be received to simultaneously decode and obtain the data sent by the signal transmitting end at the moment.
The invention has various embodiments, and all technical solutions formed by adopting equivalent transformation or equivalent transformation are within the protection scope of the invention.
Claims (9)
1. A multi-input multi-output optical communication system based on diffraction effect comprises an optical signal transmitting end and an optical signal receiving end, and is characterized in that:
the optical signal transmitting end comprises an optical intensity modulator and an optical signal transmitting array connected with the optical intensity modulator, the optical signal transmitting array comprises m × n light sources, wherein each n light sources are distributed in one signal transmitting area, the optical signal transmitting array has m signal transmitting areas, the spectrum frequency ranges of the n light sources in each signal transmitting area can be mutually overlapped but the spectrums are not completely the same, the spectrums of any two light sources belonging to different signal transmitting areas can be the same, the optical intensity modulator modulates m × n signals onto optical carriers transmitted by the m × n light sources respectively to generate corresponding optical modulation signals, and modulates different signals at different moments, wherein m and n are integers more than 1;
the optical signal receiving end comprises a first collimating device, a dispersion device, a second collimating device, a detector and a signal processing unit connected with the detector, wherein the first collimating device is positioned in front of the dispersion device, the first collimating device can enable light transmitted along the direction of a connecting line from an optical signal transmitting array to the dispersion device to pass through and filter light transmitted along other directions, and enable signal light emitted from different signal transmitting areas to pass through the first collimating device and then to be emitted to different parts of the dispersion device, the dispersion device can enable the signal light emitted by each light source of the signal transmitting areas to generate diffraction effects, the light intensity distribution of diffracted light emitted by the signal light with the same frequency and the same intensity and incident to different positions of the dispersion device is different, and the detector is an array type detection chip consisting of at least m multiplied by n optical detection pixel elements with the same spectral response, the array type detection chip is provided with at least m signal receiving areas, wherein any signal receiving area is provided with at least n optical detection pixel elements, the light detection pixel element is responsive to signal light incident on the photosensitive surface of the pixel element, the second collimating device is positioned between the dispersive device and the detector, the second collimating device can make light transmitted along the direction from the dispersive device to the detector pass through, and can filter light transmitted along other directions, and the signal lights emitted by different areas of the optical signal transmitting array can be projected on the optical detection pixel elements in different signal receiving areas of the detector respectively after passing through the dispersion device, the signal processing unit respectively analyzes and processes data detected by pixel elements in different signal receiving areas, and finally performs data analysis and processing through the signal processing unit, and the signals sent by the optical signal transmitting end are obtained through decoding;
the dispersion device comprises a series of diffraction holes or diffraction slits in an opaque light-blocking layer constructed on one surface of a transparent substrate, the series of diffraction holes or diffraction slits have different aperture sizes or different slit widths and are randomly distributed in the light-blocking layer, and the depth of each diffraction hole or diffraction slit is the same as the thickness of the light-blocking layer.
2. A diffraction effect based multiple input multiple output optical communication system according to claim 1, wherein: the first collimation device comprises a first convex lens, a first small aperture diaphragm and a second convex lens, and the gap of the first small aperture diaphragm is arranged at the common focus between the first convex lens and the second convex lens.
3. A diffraction effect based multiple input multiple output optical communication system according to claim 1, wherein: the optical signal receiving end further comprises an optical wavelength conversion component arranged in front of or behind the dispersion device, the optical wavelength conversion component comprises a wavelength conversion layer, the wavelength conversion layer comprises at least one wavelength conversion optical material, a part or all of an absorption spectrum of the wavelength conversion optical material exceeds a detection range of the array detection chip, and an emission spectrum of the wavelength conversion optical material is entirely in the detection range of the array detection chip; the wavelength conversion optical material is any material having the property of absorbing light of one wavelength and emitting light of another different wavelength, or a combination of these materials.
4. A diffraction effect based multiple input multiple output optical communication system according to claim 1, wherein: the second collimating device comprises a third convex lens, a second small aperture diaphragm and a fourth convex lens, and the gap of the second small aperture diaphragm is arranged at the common focus between the third convex lens and the fourth convex lens.
5. A diffraction effect based multiple input multiple output optical communication system according to claim 1, wherein: the aperture size or the slit width of each diffraction hole or diffraction slit in the dispersion device is close to the wavelength of the signal light and ranges from 0.3 to 5 times of the wavelength of the signal light.
6. A diffraction effect based multiple input multiple output optical communication system according to claim 1, wherein: each signal sending area of the optical signal sending end comprises n light sources with the same emission spectrum, and each light source is respectively attached with filter films with different transmission spectrums.
7. A diffraction effect based multiple input multiple output optical communication system according to claim 1, wherein: when the light source is required for illumination, a visible light band white light source is adopted, and when the light source is not required for illumination, a mid-infrared band light source is adopted.
8. The method for transmitting and decoding communication signals in an optical communication system according to any of the preceding claims, wherein: the method comprises the following steps:
step 1: suppose that at a time t, n light sources in m signal transmission regions are modulated by a light intensity modulator to transmit a signal S'1,S’2,…S’m×nThe emitted signals are distinguished by the intensity of light;
step 2: suppose that the signals emitted by the n light sources in a certain signal transmission region and modulated by the light intensity modulator are S'1,S’2,…S’n；
And step 3: the detector receives light emitted by the light signal emitting end, wherein the signal light emitted by the kth signal sending area passes through a signal transmission space, then sequentially passes through the first collimating device, the dispersion device, the light wavelength conversion component and the second collimating device or sequentially passes through the first collimating device, the dispersion device and the second collimating device at the light signal receiving end, finally irradiates on the light detection pixel elements in the signal receiving area corresponding to the signal sending area, and the light intensities received by at least n light detection pixel elements in the signal receiving area corresponding to the signal sending area in the step 2 at the moment t are set as I respectively1,I2,…In,…；
And 4, step 4: respectively removing noise from the light intensity received by each light detection pixel element in the signal receiving area corresponding to the signal sending area in the step 3, and then substituting the light intensity into each row unit of the amplification matrix of the matrix equation, and respectively substituting the ratio of the value detected by each light detection pixel element under the condition that each light source in the signal sending area is independently lighted to the emission intensity of the lighted light source, and the ratio of the value to the emission intensity of the lighted light source, after the noise is removed, into each row unit of the coefficient matrix of the matrix equation, because the data of each unit of the coefficient matrix can be measured in advance through experiments, the signal S can be obtained by solving the matrix equation1,S2,…Sn；
And 5: get S1,S2,…SnThe average value of the n values is used as a judgment threshold, and S is used1,S2,…SnAnd judgeComparing the signal values with the threshold, setting the signal value to be 1 when the signal value is larger than the threshold, and setting the signal value to be 0 when the signal value is smaller than the threshold, so that the actual signals S 'transmitted by n light sources in a certain signal transmitting area of the optical signal transmitting end at the moment t can be obtained at the optical signal receiving end'1,S’2,…S’n；
Step 6: respectively substituting the data measured by the optical detection pixel elements in each signal receiving area corresponding to each signal sending area in the step 1 into each matrix equation, and respectively repeating the steps 2-5, namely, the signals S 'are received at the optical signal receiving end by solving m matrix equations'1,S’2,…S’m×n；
And 7: different signals are modulated at different moments through the light intensity modulator, and the signals sent by the light signal transmitting end at different moments can be received at the light signal receiving end.
9. The method of claim 8, wherein the method comprises: the matrix equation in the step 4 can be solved through one of a convex optimization algorithm, a Tikhonov regularization algorithm, an L1 norm regularization algorithm, a genetic algorithm, a cross direction multiplier method and a simulated annealing algorithm, and other known or unknown mathematical optimization methods can be adopted to solve the matrix equation so as to reduce the error rate of the signal.
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