TWI694685B - Bipolar optical code division multiple access system in wireless optical communication - Google Patents

Abstract

Disclosed is a bipolar optical code division multiple access system in wireless optical communication, comprising an encoding device, a light signal transmitting device, a light signal receiving device and a decoding device, wherein by applying the bipolar optical code and the optical code division multiple access to the wireless optical communication, an architecture of the bipolar optical code division multiple access system is realized at low cost, the problem of multiple access interference (MAI) is effectively eliminated and the bit error rate is reduced.

Description

Bipolar code division multiplexing system for wireless optical communication

The invention relates to a wireless optical communication system, in particular to a bipolar code division multiplexing system of wireless optical communication.

Wireless optical communication is a wireless communication technology that uses light to carry information. Different from the radio frequency (Radio frequency; RF) communication that may have electromagnetic wave interference, it is strictly controlled on some special occasions such as communication between airport towers and aircraft, precision instruments in large hospitals, and wireless optical communication has the opportunity It can provide a more stable communication service and has become a very popular research topic.

Optical Code Division Multiple Access (OCDMA) technology is a combination of CDMA technology and optical fiber communication technology. It can be divided into coherent OCDMA system and non-coherent OCDMA according to the form of light source and signal superposition The non-coherent OCDMA system is currently the mainstream due to its simple structure, loose hardware requirements, and low cost. The non-coherent OCDMA system uses the intensity of the optical field to represent the signal and encode it. The encoding method is mainly unipolar code division (0, 1), that is, all signals are represented by greater than zero or equal to zero, using the presence or absence of optical signals Get unipolar coded information.

However, the non-coherent OCDMA system is limited to the use of unipolar coding. The number of codes that can be provided is small, and the system capacity is insufficient. As the number of users increases and the transmission rate increases, there will be increased system costs and multiple acquisitions. Multiple interference (Multiple Access Interference; MAI) and other problems, so as the optical communication system still needs to be improved.

Therefore, the object of the present invention is to provide a bipolar code division multiplexing system for wireless optical communication to solve the problems of the conventional technology.

The technical means adopted by the present invention to solve the problems of the conventional technology is to provide a bipolar code division multiplexing system for wireless optical communication, including: an encoding end device, including a light source, an encoding end optical coupler, and two encodings An end optical circulator and an optical switch, two first ports of the encoding end optical circulator are respectively connected to the light source through the encoding end optical coupler, and one of the second ports of the encoding end optical circulator is connected There is a first encoding end fiber Bragg grating group forming a reflected light signal, and another second port optical path of the encoding end optical circulator is connected to a second encoding end fiber Bragg grating group forming a reflected light signal, the light The two input terminals of the switch are respectively optically connected to the third ports of the two optical circulators at the coding end, so that the light from the light source inputs data through the switching of the optical switch and outputs from the two output terminals of the optical switch Optical data signal; an optical transmission device, including two optical collimators at the transmitting end, a vertical polarizing plate, a horizontal polarizing plate and a beam splitter, the vertical polarizing plate and the horizontal polarizing plate are collimated by the individual transmitting end light Straightener and the optical path are respectively connected to the individual output ends of the optical switch, so that the optical data signals output from the encoding end device are sent by the vertical polarization of the vertical polarizer and the horizontal polarization of the horizontal polarizer, respectively To the beam splitter, it is integrated into an optical transmission signal and transmitted; an optical receiving device, including a polarized beam splitter and two receiving end optical collimators, the polarized beam splitter The optical path is connected to the beam splitter, the two optical collimator optical paths are connected to the polarized beam splitter, and the polarized beam splitter receives the optical transmission signal, and separates the optical transmission signal according to the polarization state Splitting into two optical collimators at the receiving end; and a decoding device including two optical circulators at the decoding end, two optical couplers at the decoding end and a balanced photodetector, and two optical circulators at the decoding end The first port is connected to the polarizing beam splitter through an optical path of each receiving end optical collimator, and one of the decoding end optical couplers respectively passes through a second decoding end fiber Bragg grating group forming a penetrating optical signal Group and an optical path connected to an individual second port of the decoding end optical circulator through a first decoding end fiber Bragg grating group forming a penetrating optical signal, and the other optical path of the decoding end optical coupler is connected to an individual The third port of the decode end optical circulator. The balanced optical detector optical path is connected to the two decode end optical couplers to decode the optical transmission signal. The first encoder end fiber Bragg grating group corresponds to the wavelength At the first decoding end fiber Bragg grating group, the second encoding end fiber Bragg grating group corresponds to a wavelength corresponding to the second decoding end fiber Bragg grating group.

In an embodiment of the present invention, a bipolar code division multiplexing system for wireless optical communication is provided, wherein the bipolar code division multiplexing system includes a plurality of encoding end devices and a plurality of decoding end devices, and the optical transmission The device further includes two transmitting-end optical couplers, the vertical polarizer and the horizontal polarizer of the optical transmitting device are respectively optically connected to the individual optical switches of the encoding-end devices via the individual transmitting-end optical couplers. At the output end, the light receiving device further includes two receiving end optical couplers, and each of the decoding end optical circulators of each decoding end device is connected to the polarization splitting optical path via the individual receiving end optical coupler mirror.

In one embodiment of the present invention, a bipolar code division multiplexing system for wireless optical communication is provided, wherein the encoding end device further includes an erbium-doped fiber amplifier, and the optical path is connected between the light source and the encoding end optical coupler .

In an embodiment of the present invention, a bipolar code division multiplexing system for wireless optical communication is provided, wherein the decoding end device further includes an attenuator, and the optical path is connected to the decoding end optical coupler and the balanced photodetector between.

In an embodiment of the present invention, a bipolar code division multiplexing system for wireless optical communication is provided, wherein the light source is an ultra-high brightness light-emitting diode.

In an embodiment of the present invention, a bipolar code division multiplexing system for wireless optical communication is provided, wherein the first code-end fiber Bragg grating group includes a first wavelength fiber Bragg grating and a third wavelength fiber Bragg grating , The second encoding end fiber Bragg grating group includes a second wavelength fiber Bragg grating and a fourth wavelength fiber Bragg grating, the first decoding end fiber Bragg grating group includes the first wavelength fiber Bragg grating and the first For a three-wavelength fiber Bragg grating, the second decoding-end fiber Bragg grating group includes the second wavelength fiber Bragg grating and the fourth wavelength fiber Bragg grating.

In an embodiment of the invention, a bipolar code division multiplexing system for wireless optical communication is provided, wherein the first wavelength is 1543 nm, the second wavelength is 1546 nm, the third wavelength is 1549 nm, and the fourth wavelength It is 1552nm.

Through the technical means adopted by the present invention, in the bipolar code division multiplexing system of the wireless optical communication of the present invention, the bipolar code division (-1, 1), optical code division multiplexing extraction technology and wireless optical The combination of communication and the use of a simple and low-cost structure to achieve bipolar optical code division multiplexing architecture can effectively eliminate the problem of multiple acquisition interference and reduce the bit error rate (bit error rate; BER).

100: Bipolar code division multiplexing system for wireless optical communication

100a: Bipolar code division multiplexing system for wireless optical communication

100b: Bipolar code division multiplexing system for wireless optical communication

1: Coding device

11: Light source

12: Encoding end optical coupler

13: Code end optical circulator

131: First port

132: Second port

133: Third port

14: Code end optical circulator

141: First port

142: Second port

143: Third Port

15: Optical switch

151: input

152: input

153: output

154: output

16: Erbium-doped fiber amplifier

2: Optical transmission device

21: Transmitting optical collimator

22: Transmitting optical collimator

23: Vertical polarizer

24: horizontal polarizer

25: Beamsplitter

26: Transmitting optical coupler

27: Transmitting optical coupler

3: Optical receiving device

31: polarization beam splitter

32: Receiver optical collimator

33: Receiver optical collimator

34: Receiver optical coupler

35: Receiver optical coupler

4: Decoding device

41: Decoding end optical circulator

411: First port

412: Second port

413: Third port

42: Decoding end optical circulator

421: First port

422: Second port

423: Third port

43: Decoding end optical coupler

44: Decoding end optical coupler

45: Balanced photodetector

46: attenuator

FBG1: Fiber Bragg Grating Group at the first coding end

FBG2: Fiber Bragg Grating Group at the second encoding end

FBG3: The first decoding end fiber Bragg grating group

FBG4: Fiber Bragg Grating Group at the second decoding end

L0: light

L1: Optical data signal

L2: optical transmission signal

PD1: branch

PD2: branch

[Figure 1] is a schematic diagram showing a bipolar code division multiplexing system for wireless optical communication according to an embodiment of the present invention; [Figure 2] is a bipolar display for wireless optical communication according to an embodiment of the present invention A schematic diagram of a code division multiplexing system when there are multiple users; [Figure 3] is a schematic diagram showing a bipolar code division multiplexing system for wireless optical communication according to another embodiment of the present invention.

The embodiments of the present invention will be described below based on FIGS. 1 to 3. This description is not intended to limit the embodiments of the present invention, but is one of the examples of the present invention.

As shown in FIG. 1, a bipolar code division multiplexing system 100 for wireless optical communication according to an embodiment of the present invention includes: an encoding end device 1, including a light source 11, an encoding end optical coupler 12, Two code-end optical circulators 13, 14 and an optical switch 15, two first ports 131, 141 of the code-end optical circulators 13, 14 are respectively connected to the light source 11 via the code-end optical coupler 12 and the light path , One of the optical ports of the second port 132 of the encoding end optical circulator 13 is connected to the first encoding end fiber Bragg grating group FBG1 forming the reflected optical signal, and the other of the second port 142 of the encoding end optical circulator 14 is optically connected There is a second encoding end fiber Bragg grating group FBG2 which forms one of the reflected optical signals. The two input ends 151 and 152 of the optical switch 15 are respectively optically connected to the third ports 133 of the two encoding end optical circulators 13 and 14 143, so that the light L0 from the light source 11 inputs data through the switching of the optical switch 15 and outputs the optical data signal L1 from the two output terminals 153, 154 of the optical switch 15; an optical transmission device 2, including two A transmitting end optical collimator 21, 22, a vertical polarizing plate 23, a horizontal polarizing plate 24 and a beam splitter 25, the vertical polarizing plate 23 and the horizontal polarizing plate 24 pass through the individual transmitting end optical collimator 21 , 22 and optical connection At the individual output terminals 153, 154 of the optical switch 15, the optical data signal L1 output from the encoding terminal device 1 passes the vertical polarization of the vertical polarizer 23 and the horizontal polarization of the horizontal polarizer 24, respectively It is sent to the beam splitter 25, and aggregated into an optical transmission signal L2 for transmission; an optical receiving device 3 includes a polarized beam splitter 31 and two receiving end optical collimators 32, 33, the polarization The optical path of the beam splitter 31 is connected to the beam splitter 25, the two optical paths of the receiving end optical collimators 32, 33 are connected to the polarized beam splitter 31, and the polarized beam splitter 31 receives the optical transmission signal L2, and The optical transmission signal L2 is split into two optical collimators 32, 33 of the receiving end according to the polarization state; and a decoding end device 4 includes two decoding end optical circulators 41, 42, two decoding end light The couplers 43, 44 and a balanced photodetector 45, the two first ports 411, 421 of the decoding end optical circulators 41, 42 are respectively optically connected to the receiving end optical collimators 32, 33 respectively In the polarization beam splitter 31, one of the decoding-end optical couplers 43 respectively passes through a second decoding-end fiber Bragg grating group FBG4 forming a through-optical signal and a first decoding-end fiber Bragg through forming a through-optical signal The grating group FBG3 and the optical path are connected to the second ports 412 and 422 of the individual decoding end optical circulators 41 and 42, and the other optical path of the decoding end optical coupler 44 is connected to the individual decoding end optical circulators 41 and 42 The third port 413, 423, the optical path of the balanced photodetector 45 is connected to two of the decoding end optical couplers 43, 44 to decode the optical transmission signal L2, wherein the first encoding end fiber Bragg grating group FBG1 respectively corresponds to the wavelength of the first decoding end fiber Bragg grating group FBG3, and the second encoding end of the fiber Bragg grating group FBG2 corresponds to the wavelength of the second decoding end fiber Bragg grating group FBG4.

Specifically, in the encoding end device 1, the light source 11 is a super high-luminance LED (Super Luminescent Diode; SLD), which is an edge-emitting diode light source based on amplified spontaneous emission, used to Provide stable broadband light. In addition, in this embodiment, the first encoding end fiber Bragg grating group FBG1 includes a fiber Bragg grating of a first wavelength λ1 and a third wavelength of λ3 Fiber Bragg Grating, the second coding end fiber Bragg Grating group FBG2 includes a fiber Bragg grating with a second wavelength λ2 and a fiber Bragg grating with a fourth wavelength λ4, and the four wavelengths λ1, λ2, λ3, λ4 are expressed as four Bit user code. Moreover, in this embodiment, the wavelengths represented by the respective bits are: the first wavelength λ1 is 1543 nm, the second wavelength λ2 is 1546 nm, the third wavelength λ3 is 1549 nm, and the fourth wavelength λ4 is 1552 nm . Similarly, in the decoding end device 4, the wavelength of the first encoding end fiber Bragg grating group FBG1 corresponds to the first decoding end fiber Bragg grating group FBG3, and the second encoding end fiber Bragg grating group FBG2 system The wavelength corresponds to the second decoding end fiber Bragg grating group FBG4, so the first decoding end fiber Bragg grating group FBG3 includes the fiber Bragg grating of the first wavelength λ1 and the fiber Bragg grating of the third wavelength λ3, the first The two decoding end fiber Bragg grating group FBG4 includes the fiber Bragg grating of the second wavelength λ2 and the fiber Bragg grating of the fourth wavelength λ4.

The operation of the bipolar code division multiplexing system 100 of the wireless optical communication of this embodiment will be described below. As shown in FIG. 1, in the encoding end device 1, the light L0 emitted from the light source 11 is transmitted to the upper and lower two encoding end optical circulators 13 and 14 through the encoding end optical coupler 12. The first port 131,141. An optical circulator is an element with three ports. Among the optical signals input from the first port of the optical circulator, only the second port can receive it, but the third port does not. Only the third port can receive the optical signal input from the second port of the circulator, but the first port does not. In this way, the fiber Bragg gratings connected to the second ports 132, 142 of the two encoding end optical circulators 13, 14 respectively will reflect the specific wavelength to be encoded (ie, the first wavelength λ1, the second wavelength λ2, the third wavelength λ3 and the fourth wavelength λ4), and the reflected light is sent into the optical switch 15 by the third ports 133 and 143 of the two encoding-end optical circulators 13 and 14. The optical switch 15 selects and transmits the optical signal representing "Bit 1" or "Bit 0(-1)" by switching to input data. The optical switch 15 can be a mechanical optical switch In order to improve the system speed, you can also choose an optical switch with a higher switching frequency. In this embodiment, when the optical switch 15 is "OFF", the light reflected by the code end optical circulator 13 on the upper side in the figure is sent from the input end 151 to the output end 153, and the lower side in the figure The light reflected by the encoder-end optical circulator 14 is sent from the input end 152 to the output end 154. When the optical switch 15 is "ON", the light reflected by the encoder end optical circulator 13 on the upper side in the figure will be sent from the input end 151 to the output end 154, and the encoder end light circulation on the lower side in the figure The light reflected by the receiver 14 is sent from the input terminal 152 to the output terminal 153.

In the optical transmission device 2, the optical data signal L1 sent from the output end 153 of the optical switch 15 is sent to the vertical polarizer 23 through the optical collimator 21 at the transmission end and polarized to 90°, from The optical data signal L1 sent from the output end 154 of the optical switch 15 is sent to the horizontal polarizer 24 through the transmitting end optical collimator 22 and polarized to 0°. After that, two lights with different polarization states are coupled into a signal (ie, the light transmission signal L2) through the beam splitter 25 and transmitted in a free space (wireless optical communication) to the light receiving device 3 .

In the light receiving device 3, the received light transmission signal L2 is separated into 90° and 0° optical signals by the polarizing beam splitter 31, and respectively passed through the respective receiving end optical collimators 32, 33 It is sent to the two optical circulators 41 and 42 at the decoding end.

In the decoding device 4, the 90° optical signal passes from the polarization beam splitter 31 to the first port 411 of the decoding end optical circulator 41 on the upper side in the figure, and the 0° optical signal is split from the polarization The mirror 31 passes to the first port 421 of the decoding end optical circulator 42 on the lower side in the figure. In this way, the fiber Bragg grating decoded by the optical paths connected to the second ports 412, 422 of the two decoding end optical circulators 41, 42 respectively penetrates to the decoding end optical coupler 43 on the upper side in the figure, or by the The third ports 413 and 423 of the decode end optical circulators 41 and 42 reflect to the decode end optical coupler 44 on the lower side in the figure. The light meeting to the decode end optical couplers 43, 44 The two branches PD1 and PD2 of the balanced photodetector 45 are respectively sent, and the output of the balanced photodetector 45 is the characteristic that the two branches are subtracted to achieve correct decoding. For example, when the optical signal is "Bit 1", all optical signals will pass through the fiber Bragg grating and enter the branch PD1 on the upper side of the figure without reflection, so that the balanced light detector 45 transmits The two branches PD1 and PD2 are subtracted (1-0=1) to obtain the result of "Bit 1". When the optical signal is "Bit 0", all optical signals will be reflected by the fiber Bragg grating to the branch PD2 in the lower side of the figure, so that the balanced photodetector 45 is subtracted through the two branches PD1 and PD2 (0-1=-1) Get the result of "Bit 0(-1)". When the optical signal is incorrect, the light passing through the two decoding end optical circulators 41 and 42 will simultaneously penetrate and reflect, so that both branches PD1 and PD2 of the balanced light detector 45 will have The penetrating and reflecting signals will be eliminated after subtraction, so as to achieve the effect of eliminating multiple acquisition interference.

As shown in FIG. 2, according to an embodiment of the present invention, in the case of multiple users, the bipolar code division multiplexing system 100a for wireless optical communication includes a plurality of the encoding end devices 1 and a plurality of the decoding end devices 4 The optical transmitting device 2 further includes two transmitting-end optical couplers 26 and 27. The vertical polarizing plate 23 and the horizontal polarizing plate 24 of the optical transmitting device 2 are respectively separated by the transmitting-end optical couplers 26 and 27. The optical path is connected to the individual output terminals 153 and 154 of the optical switch 15 of each encoding-end device 1, the optical receiving device 3 further includes two receiving-end optical couplers 34 and 35, and each of the decoding-end device 4 has an individual The decoding-end optical circulators 41 and 42 are optically connected to the polarization beam splitter 31 via individual receiving-end optical couplers 34 and 35, respectively. The difference between the bipolar code division multiplexing system 100a of the wireless optical communication of this embodiment and the foregoing embodiments is that in the case of multiple users, each of the encoding end devices 1 will pass all the parts that belong to the vertically polarized state through The transmitting-end optical coupler 26 is assembled to the vertical polarizer 23, and all parts that belong to the vertically polarized state are integrated to the horizontal-polarizing plate 24 via the transmitting-end optical coupler 27, and the multi-user code is encoded by the beam splitter 25 The signal is coupled and sent into free space, and then the polarization beam splitter 31 will drop The straight and horizontal signals are separated and transmitted to the respective decoding-end devices 4 through the individual receiving-end optical couplers 34 and 35, respectively, so as to realize wireless optical communication for multiple users.

As shown in FIG. 3, according to an embodiment of the present invention, a bipolar code division multiplexing system 100b for wireless optical communication, the encoding end device 1 further includes an erbium-doped fiber amplifier 16, an optical path connected between the light source 11 and the Between the optical couplers 12 at the encoding end, the input power from the light source 11 is increased to improve the problem that the overall system power consumption is too large and the resulting power is too small. In addition, in this embodiment, the decoding-end device 4 further includes an attenuator 46, and the optical path is connected between the decoding-end optical coupler 43 and the balanced photodetector 45 to effectively eliminate additional signal penetration The excess power caused.

With the above structure, in the bipolar code division multiplexing system 100, 100a, 100b of the wireless optical communication of the present invention, the bipolar code division (-1, 1), optical code division multiplexing extraction technology and wireless The combination of optical communication and the use of a simple and low-cost structure to achieve bipolar optical code division multiplexing architecture can effectively eliminate the problem of multiple acquisition interference and reduce the bit error rate.

The above description and description are only for the description of the preferred embodiments of the present invention. Those with ordinary knowledge of this technology can make other modifications based on the scope of the patent application defined below and the above description, but these modifications should still be It is within the scope of the rights of the invention for the spirit of the invention.

100: Bipolar code division multiplexing system for wireless optical communication

1: Coding device

11: Light source

12: Encoding end optical coupler

13: Code end optical circulator

131: First port

132: Second port

133: Third port

14: Code end optical circulator

141: First port

142: Second port

143: Third Port

15: Optical switch

151: input

152: input

153: output

154: output

2: Optical transmission device

21: Transmitting optical collimator

22: Transmitting optical collimator

23: Vertical polarizer

24: horizontal polarizer

25: Beamsplitter

3: Optical receiving device

31: polarization beam splitter

32: Receiver optical collimator

33: Receiver optical collimator

4: Decoding device

41: Decoding end optical circulator

411: First port

412: Second port

413: Third port

42: Decoding end optical circulator

421: First port

422: Second port

423: Third port

43: Decoding end optical coupler

44: Decoding end optical coupler

45: Balanced photodetector

FBG1: Fiber Bragg Grating Group at the first coding end

FBG2: Fiber Bragg Grating Group at the second encoding end

FBG3: The first decoding end fiber Bragg grating group

FBG4: Fiber Bragg Grating Group at the second decoding end

L0: light

L1: Optical data signal

L2: optical transmission signal

PD1: branch

PD2: branch

Claims (7)

A bipolar code division multiplexing system for wireless optical communication, comprising: an encoding end device, including a light source, an encoding end optical coupler, two encoding end optical circulators and an optical switch, and two encoding end optical cycles The first port of the device is connected to the light source through the encoding end optical coupler, and the second port of the encoding end optical circulator is connected to the first encoding end fiber Bragg grating group forming the reflected light signal In addition, the second port optical path of the encoding end optical circulator is connected to a second encoding end fiber Bragg grating group forming a reflected light signal, and the two input ends of the optical switch are respectively connected to the two encoding end optical paths The third port of the circulator, allowing light from the light source to input data through the switching of the optical switch and output optical data signals from the two output ends of the optical switch; an optical sending device, including two sending end optical standards Straightener, a vertical polarizer, a horizontal polarizer and a beam splitter, the vertical polarizer and the horizontal polarizer are respectively optically connected to the individual output ends of the optical switch through the individual optical collimators at the transmitting end , So that the optical data signals output from the encoding end device are sent to the beam splitter through the vertical polarization of the vertical polarizer and the horizontal polarization of the horizontal polarizer, and are aggregated into an optical transmission signal for transmission An optical receiving device, including a polarizing beam splitter and two receiving end optical collimators, the polarizing beam splitter optical path is connected to the beam splitter, the two receiving end optical collimator optical paths are connected to the polarizing beam splitter Mirror, and the polarization beam splitter receives the optical transmission signal, and splits the optical transmission signal into two optical collimators at the receiving end according to the polarization state; and a decoding end device including two decoding ends An optical circulator, two decoding-end optical couplers, and a balanced photodetector, and the first ports of the two decoding-end optical circulators are respectively connected to the polarized beam splitter via individual optical collimators at the receiving end Mirror, one of the decoding end optical couplers is respectively formed through the penetrating light One of the second decoding end fiber Bragg grating group of the signal and the first decoding end fiber Bragg grating group forming the penetrating optical signal are optically connected to the second port of the individual decoding end optical circulator, and the other one of the The optical path of the decode end optical coupler is connected to the third port of the individual decode end optical circulator. The balanced optical detector optical path is connected to two of the decode end optical couplers to decode the optical transmission signal. An encoding-end fiber Bragg grating group corresponds to a wavelength corresponding to the first decoding-end fiber Bragg grating group, and a second encoding-end fiber Bragg grating group corresponds to a wavelength corresponding to the second decoding-end fiber Bragg grating group. The bipolar code division multiplexing system of wireless optical communication according to claim 1, wherein the bipolar code division multiplexing system includes a plurality of the encoding end devices and a plurality of the decoding end devices, and the optical transmission device further includes two A transmitting end optical coupler, the vertical polarizing plate and the horizontal polarizing plate of the optical transmitting device are respectively optically connected to the individual output ends of the optical switches of the encoding end devices through the individual transmitting end optical couplers, The optical receiving device further includes two receiving-end optical couplers, and each of the decoding-end optical circulators of each decoding-end device is optically connected to the polarizing beam splitter through an individual receiving-end optical coupler. The bipolar code division multiplexing system of wireless optical communication according to claim 1, wherein the encoding end device further includes an erbium-doped fiber amplifier, and the optical path is connected between the light source and the encoding end optical coupler. The bipolar code division multiplexing system of wireless optical communication according to claim 1 or 3, wherein the decoding end device further includes an attenuator, and the optical path is connected between the decoding end optical coupler and the balanced photodetector . The bipolar code division multiplexing system of wireless optical communication according to claim 1, wherein the light source is an ultra-high brightness light emitting diode. The bipolar code division multiplexing system of wireless optical communication according to claim 1, wherein the first coded end fiber Bragg grating group includes a first wavelength fiber Bragg grating and a third wavelength fiber Bragg grating, the second The encoding end fiber Bragg grating group includes a second wavelength fiber Bragg grating and a fourth wavelength fiber Bragg grating, and the first decoding end fiber Bragg grating group includes the first wavelength fiber Bragg grating and the third wavelength fiber A Bragg grating, the second decoding end fiber Bragg grating group includes the second wavelength fiber Bragg grating and the fourth wavelength fiber Bragg grating. The bipolar code division multiplexing system of wireless optical communication according to claim 6, wherein the first wavelength is 1543 nm, the second wavelength is 1546 nm, the third wavelength is 1549 nm, and the fourth wavelength is 1552 nm.

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