CN1866796B - A space division multiple access visible light wireless access system - Google Patents

Abstract

The invention discloses a space division multiple access visible light wireless access system, which comprises the following parts: access exchange (2), center side fiber optic array(1) which is composed of several center side fiber optics (4) and several user side fiber optics (3), wherein the access exchange (2) connects several center side fiber optics (4) through interface cable (16); the center side fiber optics (4) of center side fiber optic array(1) aim several user side fiber optic (3) by visible light laser beam which makes up communication chain circuit; the communication chain circuit can use upward and descending two parallel laser beams to makeup duplex communication relation with corresponding point and use descending laser beam to makeup simplex communication relation with corresponding point. The invention reduces the cost, which is convenience to fix.

Description

A space division multiple access visible light wireless access system

Technical field:

The invention is a space division multiple access visible light wireless access system, which belongs to the innovative technology of communication access network.

Background technique:

There are many structures of the existing communication access network. How to realize broadband access network while achieving low cost has always been a headache for the communication industry. Among them, optical fiber access can solve the bandwidth problem, but the cost of equipment is high, and it is difficult to lay and connect. Radio frequency wireless access solves the problem of laying costs, but factors such as limited bandwidth, scarce electromagnetic wave resources need to be paid for, and people are more and more concerned about electromagnetic pollution limit its promotion and use. Copper cable access utilizes existing copper cable resources, but users have limited bandwidth, and the exclusive right to copper cable resources restricts competition, making it impossible for consumers to freely choose their favorite service providers. The wireless optical communication technology that has received attention recently has the advantages of broadband, no occupation of paid electromagnetic spectrum resources, and zero laying costs, etc., and overcomes the shortcomings of the above-mentioned technologies. However, the existing wireless optical communication technology is accustomed to using the near-infrared band, which makes on-site installation and alignment difficult. Usually, it is necessary to use various devices such as the built-in aiming telescope and light intensity indicator to complete the alignment work. To this end, it is necessary to pre-calibrate the emitting optical axis, receiving optical axis, and aiming optical axis in the factory to achieve accurate three-axis integration, and it is necessary to design a precise and reliable optical-mechanical structure to ensure that this three-axis integration is not affected by temperature. , transportation vibration and other factors. These requirements greatly increase the equipment and labor costs of manufacturing and debugging. In addition, the manufacturing cost and purchase cost of the infrared optical system and the infrared optoelectronic device are higher than that of the visible light optical system and the optoelectronic device. All the factors mentioned above make the existing infrared wireless optical communication equipment expensive in the market, and cannot be popularized and used in the access equipment market which is sensitive to cost. In addition, for infrared-based wireless optical communication equipment, the orientation and size of the projected light spot cannot be directly observed and controlled, and it is difficult to implement space-division multiple access when users are densely populated, which also affects its competitiveness in the access network market. .

Invention content:

The purpose of the present invention is to overcome the above disadvantages and provide a space division multiple access visible light wireless access system with high speed broadband, low production cost, saving installation cost, convenient docking and debugging, and at the same time facilitating the realization of space division multiple access multiplexing. The special-purpose optical transceiver equipment of the invention is cheap and easy to use, making the optical communication broadband access equipment a daily consumer product affordable by thousands of households.

The structural representation of the present invention is as shown in Figure 1, 2, comprises access exchange (2), the central side optical transceiver array (1) that is made up of several central side optical transceivers (4) and several user side optical transceivers (3), The access switch (2) is respectively connected to several center-side optical transceivers (4) through interface cables (16), and the several center-side optical transceivers (4) forming the center-side optical transceiver array (1) respectively pass through the visible light laser that constitutes the communication link. The beam is connected to several user-side optical transceivers (3).

Each of the above-mentioned communication links can form a point-to-point duplex communication relationship between uplink and downlink laser beams that are parallel and opposite in direction, or a point-to-point simplex communication relationship that only consists of downlink laser beams.

The above-mentioned center-side optical transceiver (4) and user-side optical transceiver (3) include three parts: optical transmitter (6), optical receiver (7) and photoelectric interface protocol converter (8), or only one or two of them part. When sending information, the information is sent to the optical transceiver from the respective sources through the interface cable (16), and the Ethernet bit stream sent from the interface cable (16) is converted into an optical communication interface code in the photoelectric interface protocol converter (8). , sent to the optical transmitter (6) through the cable (18). When receiving information, the optical communication interface code stream output by the optical receiver (7) is sent to the photoelectric interface protocol converter (8), and the optical communication interface code stream is converted into a standard Ethernet communication in the photoelectric interface protocol converter (8). The protocol code stream is sent via the interface cable (16).

Above-mentioned optical transmitter (6) comprises semiconductor laser drive circuit (26), semiconductor laser light source (9), transmits optical antenna (10), and semiconductor laser drive circuit (26) converts the pulse voltage of optical communication interface code flow into pulse Current, the pulse current drives the semiconductor laser light source (9) to emit pulsed laser light containing sending information, and the transmitting optical antenna (10) collimates the pulsed laser light into a narrow laser beam, and transmits the information to the other party's optical receiver via free space ( 7).

The operating wavelength λ of the visible light of the semiconductor laser light source (9) is 380nm<λ<750nm.

Above-mentioned optical receiver (7) comprises receiving optical antenna (12), anti-stray light diaphragm (19), receiving light spot imaging screen (21), light detector (11), light receiving circuit (22), receiving light spot Observation hole (23) (24), observation reflector (25), projection spot observation screen (26), wherein receiving optical antenna (12) receives the laser beam that the other party's optical transmitter (6) sends in already side optical receiver ( 7) For the projected spot formed nearby, the intercepted part of the light power is filtered by the anti-stray light diaphragm (19), and the receiving spot is generated at the receiving spot imaging screen (21) and the photodetector (11), and is converted into For electrical signals, the photodetector (11) is connected to the light receiving circuit (22) for signal amplification and shaping and conditioning, the output end of the light receiving circuit (22) is connected to the input end of the photoelectric interface protocol converter (8), and the photoelectric interface The standard Ethernet communication protocol code stream of the protocol converter (8) is sent through the interface cable (16).

A band-pass filter (20) is also provided between the anti-stray light diaphragm (19) and the light detector (11).

Above-mentioned transmitting optical antenna (10) is the collimation optical system that is made of single-chip or multi-chip optical lens, and receiving optical antenna (12) is glass lens or coated curved surface reflector, and light source (9) shares with transmitting optical antenna (10). The same emission optical axis, the photodetector (11) and the receiving optical antenna (12) share the same receiving optical axis, the value range of the effective field angle θ of the receiving optical antenna (12) is 0°<θ≤20°, the light The detector (11) is a silicon PIN photodiode.

The above-mentioned optical transmitter (6) and optical receiver (7) are equipped with independent optical axis direction fine-tuning mechanisms (13) and (14) respectively.

The lateral distance between the optical receivers (7) of any two user-side optical transceivers (3) is not less than twice the diameter of the laser spot projected from the other side, and the optical receivers (7) of any two center-side optical transceivers (4) The included angle of the receiving optical axis is not less than twice the viewing angle of the receiving optical antenna (12).

Compared with the prior art, the present invention has the following advantages:

1) The present invention combines the advantages of broadband high-speed optical communication that does not occupy the paid electromagnetic spectrum and radio frequency wireless communication with zero laying costs, does not damage the building environment, and overcomes the shortcomings of both; because visible light lasers can easily pass through glass windows, Therefore, users living in high-rise buildings can even install the optical transceiver on the inner side of the upper corner of the window. It not only avoids the high-altitude exterior wall work, but also does not need the vertical wiring in the building to cause disputes among neighbors.

2) The present invention uses visible light as the working wavelength of the wireless optical access network, overcomes the shortcomings of existing wireless optical communication products such as large equipment, complex structure, expensive manufacturing cost, and cumbersome debugging work, and achieves high performance, low price, and easy installation. Advantages such as easy adjustment highlight the competitive advantage in the home broadband access equipment market.

3) The present invention utilizes the characteristics of visible light laser beams to create a space division multiple access access system. Compared with the time division multiple access, wavelength division multiple access or code division multiple access methods adopted by the existing optical fiber access network and radio frequency wireless access network, the user can exclusively enjoy the entire bandwidth of the communication link, and the overall circuit system optical The system has the advantages of simple structure, lower cost and fewer failures.

4) The space division multiple access method of the present invention can also simply repeatedly deploy several similar visible light wireless access networks in the same cell, which can break the monopoly of the access network by the telecommunications operator who first settled in the cell, It is beneficial for various telecom operators to carry out healthy competition and enable users to have more choices in broadband communication services.

The invention is a space division multiple access visible light wireless access system with high-speed broadband, low production cost, saving installation cost, convenient docking and debugging, and at the same time facilitating the realization of space division multiple access multiplexing. The special-purpose optical transceiver equipment of the invention is cheap and easy to use, making the optical communication broadband access equipment a daily consumer product affordable by thousands of households.

Description of drawings:

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a structural schematic diagram of the center-side optical transceiver (4) and the user-side optical transceiver (3) of the present invention.

Detailed ways:

Example:

The structural representation of the present invention is as shown in Figure 1, 2, comprises access exchange (2), the central side optical transceiver array (1) that is made up of several central side optical transceivers (4) and several user side optical transceivers (3), The access switch (2) is respectively connected to several center-side optical transceivers (4) through interface cables (16), and several center-side optical transceivers (4) of the central-side optical transceiver array (1) pass through the visible light laser beams that constitute the communication link. Connect to several user-side optical transceivers (3).

Each of the above-mentioned communication links can form a point-to-point duplex communication relationship between uplink and downlink laser beams that are parallel and opposite in direction, or a point-to-point simplex communication relationship that only consists of downlink laser beams.

In the present embodiment, include 24 user-side optical transceivers (3), 24 user computers (15) and interface cables (16), the access switch (2) has 1 external 100/1000M Ethernet interface and 24 The internal 10/100M adaptive Ethernet interface (RJ45), the external interface is interconnected with the backbone network through the access electric/optical cable (17), and this interconnection can also be realized by using the visible light wireless access system provided by the present invention . At the same time, the access switch (2) completes the following functions according to the standard switch protocol: ① distribute signals to each user in the access network; ② collect the signals of each user and upload them to the backbone network; 15) Packet exchange for internal communication.

In this embodiment, 24 center-side optical transceivers (4) are installed in the center-side optical transceiver array (1), and these central-side optical transceivers (4) are respectively paired with 24 user-side optical transceivers (3) to form 24 by means of visible light laser beams. Each communication link is composed of uplink and downlink two parallel and opposite visible light beams to form a point-to-point full-duplex communication mode. By controlling the divergence angle of the laser beam and the optical receiver (7) optical antenna (12) Carry out the optical design of narrow field of view, the present invention is easy to accomplish only relying on the difference of the position of projected light spot and the incident angle of laser beam to distinguish the spatial orientation (address) of different users, so the present invention constitutes a typical space division In the multiple access network system, in the space division multiple access mode adopted by the present invention, the distinction of each user address only depends on the difference in the end position of each laser beam, or the difference in the angle of incidence. In the present invention, each communication link Each channel can use its own wavelength, rate and time slot arbitrarily, and each communication link has no influence or restraint on each other, realizing multi-user simultaneous full-bandwidth parallel work, and also avoiding the problems of mutual crosstalk and leakage of user signals . The above-mentioned space division multiple access method completely follows the existing Ethernet working mode in terms of signal distribution and switching, and the mature Ethernet communication switching chip can be fully utilized in the circuit, which reduces system cost while enhancing system reliability. Enhanced product competitiveness.

In the present invention, by adding a new access switch (2), a center-side optical transceiver array (1) and a corresponding group of user-side optical transceivers (3) in the same area, the parallel operation of several similar access networks can be realized, and mutual Independent, without interfering with each other.

When the present invention is in the duplex communication mode, the structure of the above-mentioned central side optical transceiver (4) and user side optical transceiver (3) can be completely the same, including optical transmitter (6), optical receiver (7), photoelectric interface protocol conversion device (8). When there is extra space inside the optical receiver (7), the photoelectric interface protocol converter (8) can be packed into one body. The optical transmitter (6) is connected with the photoelectric interface protocol converter (8) through a cable (18). In addition, the optical transceiver (5) also includes functional components such as electromagnetic interference protection facilities and power supplies necessary for communication electronic equipment.

Above-mentioned optical receiver (7) comprises receiving optical antenna (12), anti-stray light diaphragm (19), band-pass filter (20), receiving spot imaging screen (21), light detector (11), Light receiving circuit (22), receiving light spot observation hole (23) (24), observation reflector (25), receiving optical axis universal adjustment bracket (13), projecting light spot observation screen (27). The antenna diameter of the receiving optical antenna (12) is related to the access communication distance. When the communication distance is 1000m, the diameter of the receiving optical antenna can be φ110mm; and when the communication distance is within 30m, the receiving optical antenna (12) can even be omitted. , the window of the chip in the photodetector (11) acts as a receiving optical antenna (12). The bandwidth of the band-pass filter (20) can be flexibly selected according to the background light interference intensity, and can be omitted when the interference is not large, so as to reduce the cost. In this embodiment, the photodetector (11) selects the BPX-65 silicon PIN diode of OSRAM for use. The laser beam that the other party's optical transmitter (6) sends forms the projection light spot near the optical receiver (7) of the party's side, wherein the part of the optical power intercepted by the receiving optical antenna (12) passes through the anti-stray light diaphragm (19), belt After being filtered by the optical filter (20), the receiving light spot is generated at the receiving light spot imaging screen (21) and the light detector (11). By accurately adjusting the optical receiver (7), most of the optical power of the received light spot will enter the optical detector (11) and be converted into an electrical signal. Through the amplification and shaping conditioning of the light receiving circuit (22), the electrical signal is restored to the standard optical communication interface 4B5B code stream and sent to the photoelectric interface protocol converter (8). In the photoelectric interface protocol converter (8), the optical communication The interface code stream is further converted into a standard Ethernet communication protocol code stream and sent out via the interface cable (16).

On the other hand, the information that needs to be sent is also sent to the optical transceiver (5) from the corresponding signal source through the interface cable (16), and the Ethernet code stream sent from the interface cable (16) is in the optical interface protocol converter (8) Be converted into optical communication interface code (4B5B code), send to optical transmitter (6) by cable (18).

The optical transmitter (6) includes a semiconductor laser drive circuit (26), a semiconductor laser light source (9), a transmitting optical antenna (10), and a universal adjustment bracket (14) for adjusting the direction of the transmitting optical axis. The laser power emitted by the semiconductor laser light source (9) through the transmitting optical antenna (10) is related to the communication distance. When the communication distance is 1000m, it is about 5mW (conforming to the international standard for human eye safety of IEC60825ClassIIIA), and the communication distance can be ≤1mW within 100m (conforming to IEC60825ClassII International standards for eye safety). Semiconductor lasers use laser diodes with a wavelength of 650nm or 635nm series, and are subjected to high temperature aging screening. The semiconductor laser drive circuit (26) converts the pulse voltage of the optical communication interface code (4B5B code) into a pulse current, and the pulse current drives the semiconductor laser light source (9) to emit pulsed laser light containing information, and the optical antenna (10) emits the above pulsed laser light The collimated narrow laser beam transmits information to the other party's optical receiver (7) via free space, thus completing the whole process of information sending and receiving in the present invention.

The above-mentioned alignment of the emitting optical axis and the receiving optical axis can be determined and adjusted by directly observing the positions of the laser projection spot and the receiving imaging spot with human eyes, without additional optical or electronic auxiliary alignment means.

The above-mentioned access switch (2) has the functions of completing signal upload and download, collection and distribution, internal switching, etc., and the access switch (2) should have at least one optical port or electrical port facing the backbone network, and n arrays of optical terminals facing the center The communication rate of these optical ports or electrical ports is ≤10Gb/s, and conforms to the corresponding network interface protocol. When there is no need to exchange information with the external backbone network, it relies on the internal exchange of the access switch (2) function, the present invention can also constitute an internal local area network with n user nodes, and the access switch (2) can also be replaced by a network hub when the internal switching function is not used.

Corresponding to the working mode of the above-mentioned space division multiple access visible light wireless access system, the present invention also includes a set of technical methods for using visible light laser beams to project light spots to quickly align the optical transceivers of both parties. The specific implementation steps are as follows:

①By adjusting the divergence angle of the transmitting optical antenna (10) of one's own side, a complete projection spot appears on the observation screen (27) of the other side's projection spot, and at the same time, the diameter of the projection spot at the other side's optical receiver (7) is slightly larger than that of the light The housing dimensions of the receiver (7). Carefully fine-tune the universal adjustment bracket (14) of the optical transmitter (6), so that the shadow formed by the shape of the optical receiver (7) in the light spot is centered, so that the center of the projected light spot and the center of the receiving optical antenna (12) basically coincide. In this way, the adjustment of the optical axis direction of the optical transmitter (6) is completed. Projection spot observation screen (27) also available perforated translucent thin plate is made and is placed on the front portion of optical receiver (7), and effect is the same as before. The projected spot observation screen (27) is only an adjustment tool, which can be removed after adjustment, and can also be replaced by similar objects, such as light-colored walls;

② After completing the adjustment of the optical axis direction of the other optical transmitter (6), observe the position and moving direction of the receiving light spot through the receiving light spot observation hole (23) (24) and the observation mirror (25), and at the same time fine-tune the light Universally adjust the bracket (13) of the receiver (7) until the center of the receiving light spot coincides with the center of the photosensitive chip of the photodetector (11), and the status indicator light provided on the photoelectric interface protocol converter shows that the communication link is connected normally. All adjustments are now complete.

When designing and installing the above-mentioned space division multiple access visible light wireless access system, the laser beam path should meet the following requirements:

(1) Not blocked by obstacles such as buildings and cars;

(2) Put an end to all possibilities of direct laser light entering the eyes.

Due to the powerful error tolerance and error correction function of the computer Ethernet, the occasional interruption of the laser beam by small objects such as birds will not affect the normal operation of the Ethernet.

Claims (6)

1. A visible light wireless access system for space division multiple access, characterized in that it includes an access switch (2), a center-side optical transceiver array (1) composed of several central-side optical transceivers (4), and several user-side optical transceivers (3), the access switch (2) is respectively connected to several central side optical transceivers (4) through interface cables (16), and several central side optical transceivers (4) of the central side optical transceiver array (1) form communication links respectively The visible light laser beam is aimed at several user-side optical transceivers (3); each of the above-mentioned communication links can be composed of two parallel and opposite directions of uplink and downlink laser beams to form a point-to-point duplex communication relationship, or only a downlink laser beam can be used to form a point-to-point The simplex communication relationship; the above-mentioned central side optical transceiver (4) and user side optical transceiver (3) include three parts: optical transmitter (6), optical receiver (7) and optical-electrical interface protocol converter (8). The information is sent to the optical transceiver from the respective sources through the interface cable (16), and the Ethernet code stream sent from the interface cable is converted into an optical communication interface code in the photoelectric interface protocol converter (8), and sent through the cable (18) To the optical transmitter (6), the optical communication interface code stream output by the optical receiver (7) is sent into the photoelectric interface protocol converter (8), and in the photoelectric interface protocol converter (8), the optical communication interface code stream is converted into Standard Ethernet communication protocol code stream is sent via interface cable (16); above-mentioned optical transmitter (6) includes semiconductor laser driver circuit (26), semiconductor laser light source (9), transmitting optical antenna (10), semiconductor laser driver The circuit (26) converts the pulse voltage of the code stream of the optical communication interface into a pulse current, and the pulse current drives the semiconductor laser light source (9) to emit pulse laser light containing transmission information, and the transmitting optical antenna (10) collimates the pulse laser light into a narrow The laser beam transmits information to the optical receiver (7) of the other party via free space, and forms a projection spot that can be directly observed by human eyes near the optical receiver (7) of the other party; the above-mentioned optical receiver (7) includes a receiver Optical antenna (12), anti-stray light diaphragm (19), receiving light spot imaging screen (21), light detector (11), light receiving circuit (22), receiving light spot observation hole (23) (24), observation Reflector (25), projection spot observation screen (26), wherein receiving optical antenna (12) intercepts part of the optical power in the projection spot formed by the other party's laser beam after filtering through the anti-stray light diaphragm (19), and receiving the light spot The imaging screen (21) and the photodetector (11) generate a receiving light spot that can be directly observed by the human eye, and is converted into an electrical signal by the photodetector (11), and the photodetector (11) and the photodetector (11) realize signal amplification and shaping The optical receiving circuit (22) of conditioning is connected, the output end of the optical receiving circuit (22) is connected with the input end of the photoelectric interface protocol converter (8), and the standard Ethernet communication protocol code stream of the photoelectric interface protocol converter (8) passes through The interface cable (16) is sent out. 2. The space division multiple access visible light wireless access system according to claim 1, characterized in that the visible light operating wavelength λ of the semiconductor laser light source (9) is 380nm<λ<750nm. 3. The space division multiple access visible light wireless access system according to claim 1, characterized in that a bandpass filter (20) is also provided between the anti-stray light diaphragm (19) and the photodetector (11) . 4. The space division multiple access visible light wireless access system according to any one of claims 1 to 3, characterized in that the above-mentioned transmitting optical antenna (10) is a collimating optical system composed of a single or multiple optical lenses, The receiving optical antenna (12) is a glass lens or a coated curved surface reflector, the light source (9) shares the same emitting optical axis with the emitting optical antenna (10), and the light detector (11) shares the same receiving optical axis with the receiving optical antenna (12) , the value range of the effective viewing angle θ of the receiving optical antenna (12) is 0°<θ≤20°, and the light detector (11) is a silicon PIN photodiode. 5. The space division multiple access visible light wireless access system according to claim 4, characterized in that said optical transmitter (6) and optical receiver (7) are equipped with independent optical axis direction fine-tuning mechanism (13) and (14). 6. The space division multiple access visible light wireless access system according to claim 5, characterized in that the lateral distance between the optical receivers (7) of any two user-side optical transceivers (3) is not less than the laser beam projected by the other party Twice the diameter of the light spot, and the angle between the receiving optical axes of the optical receivers (7) of any two center-side optical transceivers (4) is not less than twice the field of view angle of the receiving optical antenna (12).

Images