CN216873206U - Difference mutual check demodulation device in free space optical communication - Google Patents
Difference mutual check demodulation device in free space optical communication Download PDFInfo
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- CN216873206U CN216873206U CN202123052474.5U CN202123052474U CN216873206U CN 216873206 U CN216873206 U CN 216873206U CN 202123052474 U CN202123052474 U CN 202123052474U CN 216873206 U CN216873206 U CN 216873206U
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Abstract
The utility model discloses a differential mutual check demodulation device in free space optical communication, which comprises a receiving end, a receiving end and a demodulation end, wherein the receiving end comprises an optical wavelength division module; the photoelectric detector is used for converting two paths of optical signals with different wavelengths into corresponding electric signals; the differential mutual check module is used for comparing the light intensity of the two paths of light with two wavelengths; the signal demodulation unit is used for carrying out differential mutual check demodulation according to the light intensity condition obtained by the comparator; a demodulated signal output; the optical wavelength division module, the photoelectric detector, the differential mutual verification module, the signal demodulation unit and the demodulation signal output end are sequentially connected. The utility model does not need to pay attention to the specific content of energy attenuation and emission of a single beam of light any more, only needs to pay attention to the relative size of the energy of two beams of light, eliminates the influence of interference and improves the communication quality; the transmission distance is longer; the light with the required color can be mixed through different chromaticity proportions according to the environment requirement, and the functions of communication and illumination can be achieved.
Description
The present application is a divisional application of the utility model patent application with application number 202120933139.7, application date 2021, 4-month 30, entitled "differential cross-check modem device in free space optical communication".
Technical Field
The utility model relates to the technical field of wireless optical communication, in particular to a differential mutual-check demodulation device for free space optical communication.
Background
Wireless optical communication is different from wired optical fiber communication, and uses light as a carrier to realize point-to-point, point-to-multipoint and multipoint-to-multipoint bidirectional transmission of data, voice, image, video and the like in free media such as the atmosphere. Because the transmission medium of the wireless optical communication is free space, a route does not need to be laid, and the communication mode is more flexible and convenient, so that the task which cannot be finished by the optical fiber communication can be finished, and the method has great application value for solving the communication of the last kilometer. In addition, the method has the characteristics of strong confidentiality, large communication capacity, low cost, easiness in maintenance and the like, and can be applied to the fields of emergency communication, local area network expansion, optical fiber communication backup and the like.
Meanwhile, free-space optical communication is easily subjected to various interferences in the working process due to the randomness generated by the influence of weather conditions, terrain conditions and foreign objects on a transmission channel and the complexity of the self system composition, so that the communication quality of the system is reduced, even communication interruption can be caused in severe cases, and all-weather over-the-horizon communication is difficult to realize. In addition, the contradiction between the transmission distance and bandwidth of free space optical communication and the error rate is also very prominent, and only the improvement of the transmission power is limited. Many researchers have solved this conflict by selecting a light beam with good transmittance and increasing the receiving aperture, but these methods are complicated to operate and the size, weight and cost of the system increase accordingly. In addition, it is necessary to select an appropriate modulation scheme, coding scheme, and demodulation scheme to avoid degradation of system performance. At present, most of free space optical communication systems adopt an IM-DD (intensity modulation, direct detection) mode, the most representative coding mode is OOK (on-off keying) coding, and in the face of serious external interference, the transmission distance is greatly shortened after optical signals are attenuated, and the error rate is increased.
SUMMERY OF THE UTILITY MODEL
The utility model provides a differential cross-check demodulation device in free space optical communication, which aims to improve the anti-jamming capability of a free space optical communication system, enable the free space optical communication system to be suitable for a variable environment while exerting the high-speed transmission characteristic of the free space optical communication system, and enhance the transmission stability and accuracy.
The technical scheme adopted by the utility model for solving the technical problems is as follows:
a differential cross check modulation method in free space optical communication comprises a differential cross check modulation and demodulation device in free space optical communication, wherein the device comprises a sending end, and the modulation method comprises the following steps:
the transmitting end processes the binary bit stream to be transmitted, if '1' is to be transmitted, the wavelength is lambda transmitted in a modulation time slot1Has an emission power of P1Corresponding to an amplitude of the electrical signal of U1With a transmission wavelength of λ2Has an emission power of P2Corresponding to an amplitude of the electrical signal of U2And P is1>P2（U1>U2) (ii) a If "0" is to be transmitted, the transmission power P of the two optical signals is transmitted1<P2（U1<U2）；
Or if "0" is to be sent, P1>P2（U1>U2) (ii) a If a "1" is to be sent, P1<P2（U1<U2）。
A differential cross-calibration demodulation method in free space optical communication comprises a differential cross-calibration modulation and demodulation device in free space optical communication, wherein the device comprises a receiving end, and the demodulation method comprises the following steps:
the receiving end separates the optical signal transmitted from the transmitting end to obtain two beams of optical signals with different wavelengths from the transmitting end, and the two beams of optical signals are converted into electric signals through two photoelectric detectors respectively, and then the corresponding voltage amplitudes of the two beams of optical signals are subjected to difference mutual verification: amplitude U of the transmitted signal1And U2Is U after channel attenuation1And U2' if U1´>U2Then, it is demodulated to "1"; if U is1´<U2' is demodulated to ' 0 ', or if U is present1´>U2Then, it is demodulated to "0"; if U is1´<U2Then, it is demodulated to "1".
A differential cross check modulation and demodulation device in free space optical communication comprises a sending end, wherein the sending end comprises
An electrical signal input end to be modulated for inputting an electrical signal to be modulated;
the signal modulation unit is used for carrying out differential cross-check modulation on the electric signal to be transmitted so that the light source transmits an optical signal according to the coded requirement;
the light source is used for generating two paths of optical signals with different wavelengths;
the optical wave combining module is used for combining two paths of optical signals with different wavelengths into one path and transmitting the path of the optical signals through the same channel;
the electric signal input end to be modulated, the signal modulation unit, the light source and the optical multiplexer module are sequentially connected.
A differential cross check modulation and demodulation device in free space optical communication comprises a receiving end, wherein the receiving end comprises
The optical wavelength division module is used for separating light with two wavelengths;
the photoelectric detector is used for converting the two paths of optical signals with different wavelengths into corresponding electric signals;
the difference mutual check module is used for comparing the light intensity of the two paths of light with two wavelengths;
the signal demodulation unit is used for carrying out differential mutual check demodulation according to the light intensity condition obtained by the comparator;
a demodulated signal output terminal for outputting the demodulated transmission signal;
the optical wavelength division module, the photoelectric detector, the differential mutual verification module, the signal demodulation unit and the demodulation signal output end are sequentially connected.
A difference cross check modulation-demodulation method in free space optical communication is different from the prior art in that n beams of light with different wavelengths and different energies are selected at a transmitting end, the size of the n beams is compared two by two at a receiving end, and n | can be obtained by n elements! In case of this, choose 2mIn one case, the demodulation is 2mM bit binary numbers of which 2m< n！。
The utility model has the advantages that:
(1) the demodulation of the utility model is to carry out difference mutual check processing on the energy of the two beams of light, and because the attenuation of the two beams of light is basically the same under the same channel and the two beams of light do not carry information, the specific content of energy attenuation and emission of a single beam of light does not need to be concerned, and only the relative size of the energy of the two beams of light needs to be concerned, thus eliminating the influence of interference and improving the communication quality;
(2) the utility model adopts the difference mutual check and has the other advantages that two beams of light can be sent out by using very high energy, and only the relative size of the two beams of light is required to be ensured, which means that the transmitted light beam has stronger penetrating power and longer transmission distance;
(3) the utility model is used as a communication system, and records the flicker frequency 1/T of two light-transmitting beamss，TsThe flicker frequency F, which is perceived by the human eye as a symbol period, is typically less than 200Hz, typically 1/Ts>>And F, the human eyes can not feel flickering, and the light with the required color can be mixed through different chromaticity proportions according to the environmental requirements, so that the communication and illumination functions can be realized.
Drawings
FIG. 1 is a block diagram of an embodiment of a differential cross-check modem;
fig. 2 is a schematic diagram of a specific modulation process of a transmitting end in the embodiment;
fig. 3a and fig. 3b are schematic diagrams of a specific demodulation process at a receiving end in the embodiments.
Detailed Description
The present disclosure is described in detail below with reference to the drawings, in which examples of the embodiments are shown, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the utility model and are not to be construed as limiting the utility model.
Example (b):
a differential cross check modulation method in free space optical communication comprises a differential cross check modulation and demodulation device in free space optical communication, wherein the device comprises a sending end, and the modulation method comprises the following steps:
the transmitting end processes the binary bit stream to be transmitted, if '1' is to be transmitted, the wavelength is lambda transmitted in a modulation time slot1Has an emission power of P1Corresponding to an amplitude of the electrical signal of U1With a transmission wavelength of λ2Has an emission power of P2Corresponding to an amplitude of the electrical signal of U2And P is1>P2（U1>U2) (ii) a If "0" is to be transmitted, the transmission power P of the two optical signals is transmitted1<P2（U1<U2）；
Or if "0" is to be sent, P1>P2（U1>U2) (ii) a If a "1" is to be sent, P1<P2（U1<U2）。
A differential cross-calibration demodulation method in free space optical communication comprises a differential cross-calibration modulation and demodulation device in free space optical communication, wherein the device comprises a receiving end, and the demodulation method comprises the following steps:
the receiving end separates the optical signal transmitted from the transmitting end to obtain two beams of optical signals with different wavelengths from the transmitting end, and the two beams of optical signals are converted into electric signals through two photoelectric detectors respectively, and then the corresponding voltage amplitudes of the two beams of optical signals are subjected to difference mutual verification: amplitude U of the transmitted signal1And U2Is U after channel attenuation1And U2' if U1´>U2Then, it is demodulated to "1"; if U is1´<U2' is demodulated to ' 0 ', or if U is present1´>U2Then, it is demodulated to "0"; if U is1´<U2Then, it is demodulated to "1".
As shown in fig. 1, the differential cross-calibration modem apparatus for free-space optical communication implementing the method includes a transmitting end, where the transmitting end includes
An electrical signal input end to be modulated for inputting an electrical signal to be modulated;
the signal modulation unit is used for carrying out differential cross-check modulation on the electric signal to be transmitted so that the light source transmits an optical signal according to the coded requirement;
the light source is used for generating two paths of optical signals with different wavelengths;
the optical wave combining module is used for combining two paths of optical signals with different wavelengths into one path and transmitting the path of the optical signals through the same channel;
the electric signal input end to be modulated, the signal modulation unit, the light source and the optical multiplexer module are sequentially connected.
As shown in FIG. 1, the differential cross-calibration modem apparatus for free-space optical communication implementing the above method includes a receiving end, where the receiving end includes
The optical wavelength division module is used for separating light with two wavelengths;
the photoelectric detector is used for converting the two paths of optical signals with different wavelengths into corresponding electric signals;
the difference mutual check module is used for comparing the light intensity of the two paths of light with two wavelengths;
the signal demodulation unit is used for carrying out differential mutual check demodulation according to the light intensity condition obtained by the comparator;
a demodulated signal output terminal for outputting the demodulated transmission signal;
the optical wavelength division module, the photoelectric detector, the differential mutual verification module, the signal demodulation unit and the demodulation signal output end are sequentially connected.
The basic operation process of the differential cross-calibration modem system in free-space optical communication proposed by the present invention is described below with reference to the accompanying drawings.
The differential cross-check modulation method comprises the following steps:
in order to send binary '0' or '1', the sending end selects two beams of light with different wavelengths and different energies, and then sends the two beams of light after the two beams of light are combined. After the receiving end separates the received light, the two light energy levels are compared to obtain two conditions, one is demodulated into '0', the other is demodulated into '1', and then the information sent by the sending end is restored.
Further, the method is popularized to more than two elements, for example, three beams of light with different wavelengths and different energies are selected at a transmitting end, the sizes of the three beams of light can be compared pairwise at a receiving end, and 6 conditions can be obtained: p1、P2And P3The energy of the three beams of light is respectively represented, and the three beams of light are ordered from large to small from left to right: p1 P2 P3；P1 P3 P2；P2 P1 P3；P2 P3 P1；P3 P1 P2；P3 P2 P1Four cases can be chosen, demodulation "00", "01", "10" and "11", whereby n elements can be used to obtain n! In this case, 2 can be selectedmIn one case, demodulation is 2mSeed m bit binary number, 2m< n！。
Fig. 1 shows a general block diagram of a differential cross-check modem system, and specifically, a PC is connected to a minimum system board with an FPGA chip as a core through a serial port to form a transmitting end and a receiving end of the present invention, wherein,
the light source in the transmitting end is two light emitting diode modules of an LED1 and an LED 2; the light wave combining module is a light wave combiner in several types such as diffraction grating type, prism type or waveguide type; the signal modulation unit is a minimum system board with an FPGA as a core, and the minimum system board comprises: the power module is used for generating 3.3V, 2.5V and 1.2V voltages respectively to supply power to the chip; the crystal oscillator module adopts a 50MHz active crystal oscillator; the serial port module consists of a single power level conversion chip MAX232 designed by an RS-232 standard serial port; the FLASH module consists of a 4Mbit serial configuration device EPCS4SI 8N; finally, JTAG and AS download ports and I/O ports led out through the pin header are arranged; the optical wavelength division module in the receiving end is an optical wavelength divider in several types such as diffraction grating type, prism type or waveguide type; the photoelectric detector is a PIN or APD photodiode; the differential mutual check module is a comparator or a subtracter circuit, and the signal demodulation unit is the same as the signal modulation unit of the transmitting end.
The differential cross check modulation and demodulation method in the free space optical communication comprises the following processes:
a sending end:
the PC sends information to the minimum system board taking the FPGA chip as a core through a serial port to carry out the differential cross-check modulation provided by the utility model. If the transmitted data is '1', the amplitude value U is used in one modulation time slot1The electrical signal of =5V illuminates LED1, LED2 at amplitude U2An electric signal of =3V is turned on; if the data "0" is sent, the U corresponding to the LED11=3V, U corresponding to LED22And = 5V. Fig. 2 shows a specific modulation process of a transmitting end, for example, an original binary bit stream transmitted is 101001, two modulated IO ports are respectively transmitted to two groups of LEDs with different wavelengths according to level signals shown in the figure, and finally two beams of light are emitted to be synthesized into one light signal by an optical combiner and transmitted.
Receiving end:
firstly, the transmitted light is separated into optical signals with two original wavelengths through an optical splitter, the optical signals are converted into two groups of electric signals through two photodiodes of PIN1 and PIN2, the two groups of electric signals are subjected to differential mutual verification processing provided by the utility model through a differential mutual verification module and a signal demodulation module, and the transmitted data is supposed to be 101001:
a. referring to fig. 3a, after two groups of electrical signals are connected to the comparator, the output signal is high level, and then demodulated to "1", and the signal is low level, and then demodulated to "0";
b. referring to fig. 3b, after two groups of electric signals are connected to the subtractor, if the output signal is positive, the demodulation is "1", and if the signal is negative, the demodulation is "0".
Finally, the FPGA system board sends the demodulated data to a PC through a serial port.
The preferred embodiments of the present invention have been disclosed for illustrative purposes only and are not intended to limit the utility model to the specific embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the utility model and the practical application, to thereby enable others skilled in the art to best utilize the utility model.
Claims (1)
1. The differential mutual check demodulation device in free space optical communication is characterized by comprising a receiving end, wherein the receiving end comprises
The optical wavelength division module is used for separating light with two wavelengths;
the photoelectric detector is used for converting the two paths of optical signals with different wavelengths into corresponding electric signals;
the difference mutual check module is used for comparing the light intensity of the two paths of light with two wavelengths;
the signal demodulation unit is used for carrying out differential mutual check demodulation according to the light intensity condition obtained by the comparator;
a demodulated signal output terminal for outputting the demodulated transmission signal;
the optical wavelength division module, the photoelectric detector, the differential mutual verification module, the signal demodulation unit and the demodulation signal output end are sequentially connected.
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