TWI638536B - A 100-Gbps MULTIPLE-INPUT-MULTIPLE-OUTPUT VISIBLE LASER LIGHT COMMUNICATION SYSTEM - Google Patents

Abstract

We propose and verify a 100-Gbps multiple-input multiple-output visible-light transmission system architecture that uses a vertical cavity surface-emitting laser and a 16-quadrature amplitude-modulated quadrature frequency division multiplexing signal. The use of free-space split-multiplexing significantly increases the amount of data transmitted by the system. And use low noise amplifiers and equalizers at the receiving end to achieve good error rate and clear constellation for each optical channel. An eight-channel 16-quadrature amplitude modulation orthogonal frequency division multiplexing system with a total data volume of 100 Gbps and a free space of more than 5 meters was successfully achieved. This multi-input multi-output visible light transmission system highlights its convenience in free-space optical communication transmission and demonstrates its potential for practical use.

Description

100-Gbps multiple input multiple output visible light transmission system

The invention relates to a visible light transmission system, in particular to an optical transmission system which uses a vertical cavity surface-emitting laser as a head end light source and is matched with an orthogonal frequency division multiplexing signal for data modulation.

Due to the widespread use of 3G/4G mobile communication, the rapid growth of smart phone users has also increased the data circulation of data centers, making the traditional data transmission system gradually unable to load such a large amount of data transmission. The upgrade of cloud technology in the data network environment has also expanded the data download.

Therefore, new types of transmission systems, such as active optical cables, have been used to replace the use of traditional cables in cloud servers in data centers. With the high capacity and low loss of fiber optics, the use of active fiber optic cable inside the optical transmitter can provide cloud communication with data transmission rate of 10Gbps or higher. With the gradual use of active fiber optic cable in the data center, the amount of data transmission has increased significantly and the distance of transmission has been extended. Through active fiber optic cable, the data center can meet the high data transmission needs of recent years.

However, the use of a large number of fiber optic cable lines in the data center makes the data center need to be considered on the building load, and in order to maintain the data center temperature constant, the data center has a percent Forty-six energy consumption is used in cooling equipment, which greatly increases operating costs.

Referring to Figure 1, it is an architectural diagram of a conventional optical transmission system.

When the traditional LED visible light transmission system transmits, the divergence angle is extremely large, so the energy is less concentrated, and multiple receivers will receive the same transmitter signal, so more compensation mechanisms are needed at the receiving end, and the number of compensation mechanisms is also increased. System cost and complexity.

In view of the prior art, it is an object of the present invention to provide a visible light transmission system.

To achieve the above object, the present invention provides a visible light transmission system including an arbitrary waveform generator; a vertical cavity surface-emitting laser, electrically connected to an arbitrary waveform generator; and a first lens located in a vertical cavity surface type In front of the laser, a laser beam generated by a vertical cavity surface-emitting laser is received, and the laser beam is converted into a parallel beam; a second lens receives the parallel beam and converges the parallel beam; The high frequency wide photodetector receives the laser beam passing through the second lens; and an orthogonal frequency division multiplexing analyzer electrically connects the high frequency wide photodetector. The first lens and the second lens are respectively plano-convex lenses.

In other embodiments of the present invention, the visible light transmission system may further include a low noise amplifier and an equalizer, the low noise amplifier is electrically connected to the high frequency wide photodetector, and the equalizer is electrically connected to the low noise amplifier and is positive Cross-frequency multiplex analyzer between.

The visible light transmission system may further comprise an encoding software electrically connected to the arbitrary waveform generator for controlling the waveform generated by the arbitrary waveform generator.

The visible light transmission system further comprises a decoding software electrically connected to the orthogonal frequency division multiplexing analyzer for processing the signal output by the orthogonal frequency division multiplexing analyzer.

In addition, the present invention further provides a 100-Gbps multiple input multiple output visible light transmission system, comprising two arbitrary waveform generators; two vertical cavity surface type laser groups, and vertical cavity surface type laser groups respectively electrically connected In the arbitrary waveform generator, the vertical cavity surface type laser group includes four vertical cavity surface type lasers; eight first lenses are located in front of the vertical cavity surface type laser to receive vertical resonance a laser beam generated by a cavity-type laser and converts the laser beam into a parallel beam; eight second lenses receive parallel beams and converge parallel beams; eight high-bandwidth photodetectors, receive through A laser beam of two lenses; and an orthogonal frequency division multiplexing analyzer electrically connected to the high frequency wide photodetector.

In other embodiments of the present invention, the 100-Gbps multiple input multiple output visible light transmission system further includes eight low noise amplifiers electrically connected to the high frequency wide photodetector.

In other embodiments of the present invention, the 100-Gbps multiple input multiple output visible light transmission system further includes eight sets of equalizers electrically connected between the low noise amplifier and the orthogonal frequency division multiplexing analyzer.

In other embodiments of the present invention, the 100-Gbps multiple input multiple output visible light transmission system further includes an encoding software execution encoding program electrically connected to the arbitrary waveform generator for controlling the waveform generated by the arbitrary waveform generator.

In another embodiment of the present invention, the 100-Gbps multiple input multiple output visible light transmission system further includes a decoding software to perform a decoding process, and is electrically connected to the orthogonal frequency division multiplexing analyzer for processing orthogonal frequency division multiplexing. The signal output by the analyzer.

In other embodiments of the present invention, a 100-Gbps multiple input multiple output visible light transmission system, wherein the first lens and the second lens are respectively plano-convex lenses.

In order to meet the demand and reduce the cost, we proposed and experimentally demonstrated the 100Gbps free space optical communication transmission system. Free space optical communication transmission system in telecommunications and internet It has been developed to modulate data onto light waves and perform wireless transmission in free space. This system is very useful for special environments where general communication is not possible, such as moving subways, hospitals, and airplanes. Free-space optical communication transmission systems can also be used in indoor visible light communication systems, such as some areas where microwave wireless communication is prohibited. Moreover, the visible light communication system uses the light-emitting diode or the laser diode as a light source for indoor use, and has superior confidentiality and higher data transmission rate than the microwave radio frequency communication system. Although the main limitation of the visible light communication system is that the modulation bandwidth of the light source is limited, the performance of the visible light communication system is inferior to that of the active optical cable. However, we use a surface-emitting resonator with a wavelength of 680 nm and high modulation bandwidth to enhance the data transmission of the visible light system and overcome the shortcomings of visible light communication.

In order to comply with the data transmission of the free-space optical communication transmission system using the surface-emitting resonant cavity laser in the data center, we propose to use a surface-emitting resonant cavity laser, a low noise amplifier, an equalizer, and 100Gbps multi-input multi-output visible light transmission system with 16QAM orthogonal frequency division multiplexing modulation technology. Through our proposed free space transmission technology, the cloud servo in the data center can eliminate the need for fiber backbones. In addition, because this multiple input multiple output system is transmitted by visible light, system users can also directly detect and observe the transmission process. This feature allows users to directly find and fix errors. The multi-input multi-output visible light communication system using free space demultiplexing technology can individually transmit data in each optical channel, and has higher transmission capacity than the one-way input one-way output visible light communication system. Through orthogonal frequency division multiplexing modulation, signal transmission can have better spectrum utilization and dispersion tolerance. The multi-input multi-output visible light transmission system proposed by this experiment proves that it has good bit error rate and clear constellation diagram through our experiments, which can show its convenience in free space optical communication transmission and show its practical application. potential.

3, 4‧‧‧ arbitrary waveform generator

5,6,7,8,9,10,11,12‧‧‧Vertical cavity surface-emitting laser

13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28 ‧ ‧ plano-convex lenses

29, 30, 31, 32, 33, 34, 35, 36‧‧‧ high frequency wide photodetector

37, 38, 39, 40, 41, 42, 43, 44‧‧‧ low noise amplifier

45, 46, 47, 48, 49, 50, 51, 52‧‧‧ equalizer

53‧‧‧Orthogonal Frequency Division Multiplex Analyzer

55‧‧‧Coded Software

56‧‧‧Decoding software

Figure 1 is an architectural diagram of a conventional optical transmission system.

2 is a schematic diagram of a 100-Gbps multiple input multiple output visible light transmission system of the present invention.

Figure 3 is a block diagram of a 100-Gbps multiple input multiple output visible light transmission system in accordance with the present invention.

Figure 4 is a schematic diagram of one of the visible light transmission systems of the visible light transmission system.

Figure 5 is a schematic illustration of an equalizer in accordance with one of the present invention.

Figure 6 is a BER plot and corresponding constellation diagram in accordance with the present invention.

Please refer to FIG. 2 , which is a schematic diagram of a 100-Gbps multiple input multiple output visible light transmission system according to the present invention, and FIG. 2 is a visible light transmission system using a laser as a transmission source. The LED is used as a transmission source due to the high collimation of the laser. Defects.

Referring to FIG. 3, FIG. 3 is a structural diagram of a 100-Gbps multiple input multiple output visible light transmission system according to the present invention. The 100-Gbps multiple-input multiple-output visible light transmission system uses 12.5Gbps/5GHz eight-channel and free-space transmission of more than 5km from visible light. It consists of two arbitrary waveform generators (AWG) 3 and 4, and eight vertical cavity projections. Vertical cavity surface emitting lase (VCSEL) 5, 6, 7, 8, 9, 10, 11 and 12, sixteen Plane-Convex lenses 13, 14, 15, 16, 17, 18 , 19, 20, 21, 22, 23, 24, 25, 26, 27 and 28, eight high-bandwidth photodiodes 29, 30, 31, 32, 33, 34, 35 and 36, eight low noise amplifiers (LNA) 37, 38, 39, 40, 41, 42, 43, and 44, eight equalizers 45, 46, 47, 48, 49, 50, 51, and 52, and an orthogonal frequency division multiplexing analyzer (OFDM) Analyzer)53.

Referring to FIG. 4, a visible light transmission system of one of the channels of the 100-Gbps multiple input multiple output visible light transmission system of FIG. 3 is illustrated. The 12.5 Gbps/5 GHz Orthogonal Frequency Division Modulation (OFDM) signal for each channel is encoded by an encoding software 55 and loaded into an arbitrary waveform generator (AWG) 3,16-QAM orthogonal frequency division multiplexing The modulation (OFDM) signal is generated by 128 subcarriers, 512 FFT Size, sampling rate of 10 GS/s, and center frequency (IF) of 5 GHz, and this 16-QAM orthogonal frequency division multiplexing (OFDM) The signal is directly modulated to a red-light vertical cavity surface-emitting laser with a 3-dB bandwidth of 5.2 GHz and a wavelength of 678.5-680.5 nm. The vertical cavity surface-emitting laser 5 has a diverging characteristic, so that a plano-convex lens 13 is required to convert the beam into parallel light transmission before the transmission in the free space, and the beam has a diameter of about 2.2 mm when performing parallel light transmission. After being transmitted through the 5 m free space, it is focused by another plano-convex lens 21 and then enters a high-frequency wide photodetector 29. After the high frequency wide photodetector 29 converts the optical signal into an electrical signal, the received signal is amplified by a low noise amplifier 37. After the signal is optimized by using the equalizer 45, the received 16-QAM orthogonal frequency division multiplexing signal is extracted by the orthogonal frequency division multiplexing analyzer 53, and the extracted data is imported. A decoding software 56 performs the decoding process and calculates the transmitted data error rate and corresponding constellation map.

Claims (6)

A 100-Gbps multiple input multiple output visible light transmission system comprises: two arbitrary waveform generators; two vertical cavity surface type laser groups, each of which is electrically connected to each of the vertical cavity An arbitrary waveform generator, each of the vertical cavity surface-emitting laser groups includes four vertical cavity surface-emitting lasers; eight first lenses are located in front of each of the vertical cavity surface-emitting lasers for Receiving a laser beam set generated by each of the vertical cavity surface-emitting lasers, and converting the laser beam group into a parallel beam group; eight second lenses receiving the parallel beams and converging the parallel beams Eight high-frequency wide photodetectors that receive laser beams that pass through the second lens; and an orthogonal frequency division multiplexing analyzer that electrically connects the high-frequency wide photodetectors. The 100-Gbps multiple input multiple output visible light transmission system of claim 1, the two vertical cavity surface type laser group further comprises eight vertical cavity surface type lasers connected to the two arbitrary waveform generators. The 100-Gbps multiple input multiple output visible light transmission system of claim 1, the parallel beam set further comprising eight parallel beams. The 100-Gbps multiple input multiple output visible light transmission system as claimed in claim 1 further comprises eight low noise amplifiers electrically connected to the high frequency wide photodetectors. The 100-Gbps multiple input multiple output visible light transmission system as claimed in claim 4 further includes eight sets of equalizers electrically connected between the low noise amplifiers and the orthogonal frequency division multiplexing analyzer. The 100-Gbps multiple input multiple output visible light transmission system of claim 1, wherein each of the first lens and each of the second lenses are plano-convex lenses.