TW201539997A - A multiple-input-multiple-output visible light communication system based on VCSELS and spatial light modulators - Google Patents

A multiple-input-multiple-output visible light communication system based on VCSELS and spatial light modulators Download PDF

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TW201539997A
TW201539997A TW103112237A TW103112237A TW201539997A TW 201539997 A TW201539997 A TW 201539997A TW 103112237 A TW103112237 A TW 103112237A TW 103112237 A TW103112237 A TW 103112237A TW 201539997 A TW201539997 A TW 201539997A
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vertical cavity
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TWI506969B (en
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Hai-Han Lu
Sheng-Siang Ruan
Tai-Wei Jhang
Kuan-Hung Wu
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Hai-Han Lu
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Abstract

A multiple-input-multiple-output (MIMO) visible light communication (VLC) system employing vertical cavity surface emitting laser (VCSEL) and spatial light modulators (SLMs) with 16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) modulating signal is proposed and experimentally demonstrated. The transmission capacity of system is significantly increased by space division demultiplexing scheme. With the assistance of low noise amplifier (LNA) and data comparator, good bit error rate (BER) performance, clear constellation map, and clear eye diagram are achieved for each optical channel. Such a MIMO VLC system would be attractive for providing services including data and telecommunication services. Our proposed system is suitably applicable to the light wave communication system in wireless transmission.

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基於垂直共振腔面射型雷射與空間光調變器整合多重輸入多重輸出可見光通訊系統 Integrated multiple input multiple output visible light communication system based on vertical cavity surface-emitting laser and spatial light modulator

本發明為可見光通訊技術領域，而本發明是以新穎的的可見雷射光光通訊為主體，採用近年來備受矚目的垂直共振腔面射型雷射為頭端光源並整合空間光調變器處理光學設計的問題，接著載入新穎的正交分頻多工(OFDM)訊號進行資料調變再藉由電域的補償機制進行通道最佳化。 The invention is in the field of visible light communication technology, and the invention is mainly based on novel visible laser light-optical communication, adopting a high-profile vertical cavity surface-emitting laser in recent years as a head-end light source and integrating a spatial light modulator. Handling the problem of optical design, then loading a novel orthogonal frequency division multiplexing (OFDM) signal for data modulation and then optimizing the channel by the compensation mechanism of the electric domain.

利用可見雷射光光通信(VLLC)波長介於375-780nm間的雷射二極體(Laser Diode；LD)的可見光來作為通訊媒介來取代無線電波(Radio Frequency；RF)傳輸資料的無線網路，便可以達到在室內傳輸高速無線光通訊技術的新突破。而分波多工(WDM)傳輸系統可以充分地使用各段頻寬進而增加傳輸容量，而自由空間的分波多工(WDM)傳輸系統是利用不同的光波長來將訊號載入，而這項技術對資料傳輸或通訊系統有著相當大的幫助。 A wireless network that uses radio light (Radio Frequency; RF) to transmit data by using the visible light of a laser diode (LDLC) with a wavelength of between 375 and 780 nm (Laser Diode; LD) It can achieve a new breakthrough in the transmission of high-speed wireless optical communication technology indoors. The split-wave multiplexing (WDM) transmission system can fully use the bandwidth of each segment to increase the transmission capacity, while the free-space multiplexed-wave (WDM) transmission system uses different wavelengths of light to load the signal. Transmission or communication systems are quite helpful.

本發明整合了多重輸入多重輸出(MIMO)、垂直共振腔面射型雷射(VCSEL)、空間光調變器(SLM)、正交分頻多工技術(OFDM)、低雜訊放大器(LNA)及資料比較器(Data Comparator)技術，分別在光域上處理光學上的補償與電域上提升通道的抗擾能力。為了採用一空間光調變器應用在多重輸入多重輸出(MIMO)的可見光通訊(VLC)系統，光載波傳輸通道被劃分成獨立的子通道。這樣的多重輸入多重輸出(MIMO)的可見光通訊(VLC)系統比單一輸入單一輸出(SISO)具有更高的傳輸容量。空間光調變器被用來當作一動態菲涅爾透鏡的功能。通過空間光調變器後，光載波的的通道在空間上被分為獨立的子通道並將光束聚焦於空間上的一點用以增加自由空間的傳輸距離。正交分頻多工(OFDM)是一種具前瞻性的調變技術，不但具有非常高的頻譜效率且能夠有效的降低色散的影響，以改善系統的傳輸性能。 The invention integrates multiple input multiple output (MIMO), vertical cavity surface emitting laser (VCSEL), spatial light modulator (SLM), orthogonal frequency division multiplexing (OFDM), low noise amplifier (LNA) And the Data Comparator technology, which processes the optical compensation in the optical domain and the immunity of the boost channel in the electrical domain. In order to apply a spatial light modulator to a multiple input multiple output (MIMO) visible light communication (VLC) system, the optical carrier transmission channel is divided into independent subchannels. Such multiple input multiple output (MIMO) visible light communication (VLC) systems have higher transmission capacity than single input single output (SISO). A spatial light modulator is used as a function of a dynamic Fresnel lens. After passing through the spatial light modulator, the channel of the optical carrier is spatially divided into independent sub-channels and the beam is focused on a point in space to increase the transmission distance of the free space. Orthogonal Frequency Division Multiplexing (OFDM) is a forward-looking modulation technique that not only has very high spectral efficiency, but also effectively reduces the effects of dispersion to improve the transmission performance of the system.

101‧‧‧任意波形產生器(Arbitrary Wavelength Generator AWG) 101‧‧‧Arbitrary Wavelength Generator AWG

102‧‧‧垂直共振腔面射型雷射(Vertical Cavity Surface Emitting Laser VCSEL) 102‧‧‧Vertical Cavity Surface Emitting Laser VCSEL

103 104 105 106‧‧‧空間光調變器(Spatial Light Modulators SLM) 103 104 105 106‧‧‧Spatial Light Modulators SLM

107 108 109 110 111 112 113 114‧‧‧平-凸透鏡(Plane-Convex lens) 107 108 109 110 111 112 113 114‧‧‧Plane-Convex lens

115 116 117 118‧‧‧高頻寬光電檢測器(High Bandwidth Photodiode) 115 116 117 118‧‧‧High-bandwidth Photodiode

119 120 121 122‧‧‧低雜訊放大器(Low Noise Amplifier LNA) 119 120 121 122‧‧‧Low Noise Amplifier (LNA)

123 124 125 126‧‧‧資料比較器(Data Comparator) 123 124 125 126‧‧‧Data Comparator

127‧‧‧正交分頻多工分析儀(OFDM Analyzer) 127‧‧‧Orthogonal Frequency Division Multiplex Analyzer (OFDM Analyzer)

圖1：本發明所提出基於垂直共振腔面射型雷射與空間光調變器整合多重輸入多重輸出可見光通訊系統實驗架構圖；圖2：本發明所採用垂直共振腔面射型雷射(VCSEL)的發散角示意圖；圖3：本發明所採用垂直共振腔面射型雷射(VCSEL)的線性區光譜圖；圖4：本發明所採用資料比較器(Data Comparator)的函數流程圖圖5：此圖為本發明所提出基於垂直共振腔面射型雷射與空間光調變器整合多重輸入多重輸出可見光通訊系統所量測之誤碼率(BER)曲線圖與相對應的星座圖(constellation map)； 圖6：此圖為本發明所提出基於垂直共振腔面射型雷射與空間光調變器整合多重輸入多重輸出可見光通訊系統所量測訊號品質之眼圖(Eye Diagram)。 FIG. 1 is a schematic structural diagram of a multi-input multiple-output visible light communication system based on a vertical cavity surface-emitting laser and a spatial light modulator according to the present invention; FIG. 2 is a vertical cavity surface-emitting laser used in the present invention ( FIG. 2 ) Schematic diagram of the divergence angle of the VCSEL); FIG. 3 is a linear region spectrum diagram of the vertical cavity surface-emitting laser (VCSEL) used in the present invention; FIG. 4 is a flow chart of the function of the data comparator used in the present invention . 5 : This figure is a bit error rate (BER) curve and corresponding constellation diagram measured by the multi-input multiple-output visible light communication system based on vertical cavity surface-emitting laser and spatial light modulator. (constellation map); Figure 6 : This figure is an eye diagram of the quality of the measured signal quality of the multi-input multi-output visible light communication system based on vertical cavity surface-emitting laser and spatial light modulator. .

如圖1所示為我們所提出的多重輸入多重輸出(MIMO)的可見光通訊(VLC)系統的實驗配置採用垂直共振腔面射型雷射(VCSEL)與空間光調變器(SLM)調變16-正交振幅調變(QAM)正交分頻多工(OFDM)訊號在15公尺的自由空間鏈路傳送訊號，光束發散的可接受發散角和垂直共振腔面射型雷射(VCSEL)的光學光譜分別示於圖2和圖3，VCSEL的可調變頻寬/波長/顏色分別為3GHz/684-685.5nm/紅光範圍，而採用資料量為2.5Gbps中心頻率在2.5GHz的16-QAM OFDM訊號直接調變垂直共振腔面射型雷射。而16-QAM OFDM訊號由MATLAB軟體編碼產生，並載入至任意波形發生器(AWG)，16-QAM OFDM訊號由64個子載波、512的FFT Size以及2.5GHz的中頻(IF)模擬產生，垂直共振腔面射型雷射的發散光束透過4組空間光調變器分四路獨立傳輸。在空間光調變器中具有800×600的半透明液晶像素、像素間距為32μm和主動區域為26.6×20μm的半透明液晶。為了操作空間光調變器像動態凸透鏡，這菲涅爾透鏡的函數被加諸在空間光調變器裝置上，使得光束能被聚焦到空間上的一點，並延長自由空間傳輸的距離。 As shown in Figure 1, the experimental configuration of our proposed multiple input multiple output (MIMO) visible light communication (VLC) system uses vertical cavity surface-emitting laser (VCSEL) and spatial light modulator (SLM) modulation. 16-Quadrature Amplitude Modulation (QAM) Orthogonal Frequency Division Multiplexing (OFDM) signal transmits signals at a free-space link of 15 meters, acceptable divergence angle for beam divergence and vertical cavity surface-emitting laser (VCSEL) The optical spectra are shown in Figure 2 and Figure 3, respectively. The tunable inverter width/wavelength/color of the VCSEL is 3 GHz/684-685.5 nm/red light range, respectively, while the data volume is 2.5 Gbps center frequency at 2.5 GHz. The -QAM OFDM signal directly modulates the vertical cavity surface-emitting laser. The 16-QAM OFDM signal is generated by MATLAB software and loaded into an arbitrary waveform generator (AWG). The 16-QAM OFDM signal is generated by 64 subcarriers, 512 FFT Size and 2.5 GHz intermediate frequency (IF). The divergent beam of the vertical cavity surface-emitting laser is transmitted independently through four sets of spatial light modulators. In the spatial light modulator, there are 800×600 translucent liquid crystal pixels, a translucent liquid crystal having a pixel pitch of 32 μm and an active area of 26.6×20 μm. In order to operate the spatial light modulator like a dynamic convex lens, the function of this Fresnel lens is applied to the spatial light modulator device so that the light beam can be focused to a point in space and extend the distance traveled in free space.

在空間光調變器和焦點之間的距離為菲涅耳透鏡所設定的函數焦距。聚焦成一光點後，光束再度發散並射入第一階段的凸透鏡使得光束產 生平行光並在自由空間中傳輸，接著再送入第二階段凸透鏡進行光束的匯聚並且集中在高頻寬(BW)的光電檢測器(PD)。由此，調變的光載波傳送15公尺(0.5公尺+1.5公尺+13公尺)，然後達到高頻寬的光電檢測器。高頻寬的光電檢測器有一個檢測波長範圍320-1000nm、半功率點的頻寬為3.2GHz、主動偵測區域的直徑為0.4mm以及一響應係數為0.46mA/mW(在波長為685nm時)。所偵測到的電訊號經由低雜訊放大器(LNA)放大(雜訊係數約為4.5dB)並藉由資料比較器比對傳輸通道的失真並加以校正補償。最後16-QAM OFDM訊號由OFDM分析儀(通信信號分析儀)擷取資料，再將擷取到的資料匯入MATLAB軟體執行解碼的程序並且計算傳輸後資料誤碼率和對應的星座圖。 The distance between the spatial light modulator and the focus is the function focal length set by the Fresnel lens. After focusing on a spot, the beam is again diverged and injected into the first stage of the convex lens to make the beam The parallel light is transmitted and transmitted in free space, and then sent to the second stage convex lens to concentrate the light beam and concentrated on a high frequency wide (BW) photodetector (PD). Thus, the modulated optical carrier transmits 15 meters (0.5 meters + 1.5 meters + 13 meters) and then reaches a high frequency wide photodetector. The high-frequency wide photodetector has a detection wavelength range of 320-1000 nm, a half-power point bandwidth of 3.2 GHz, an active detection area diameter of 0.4 mm, and a response coefficient of 0.46 mA/mW (at a wavelength of 685 nm). The detected electrical signal is amplified by a low noise amplifier (LNA) (the noise coefficient is about 4.5 dB) and compared by the data comparator to correct the distortion of the transmission channel. The last 16-QAM OFDM signal is extracted by the OFDM analyzer (communication signal analyzer), and the extracted data is imported into the MATLAB software to perform the decoding process and the data error rate and the corresponding constellation map are calculated.

101‧‧‧任意波形產生器(Arbitrary Wavelength Generator AWG) 101‧‧‧Arbitrary Wavelength Generator AWG

102‧‧‧垂直共振腔面射型雷射(Vertical Cavity Surface Emitting Laser VCSEL) 102‧‧‧Vertical Cavity Surface Emitting Laser VCSEL

103 104 105 106‧‧‧空間光調變器(Spatial Light Modulators SLM) 103 104 105 106‧‧‧Spatial Light Modulators SLM

107 108 109 110 111 112 113 114‧‧‧平-凸透鏡(Plane-Convex lens) 107 108 109 110 111 112 113 114‧‧‧Plane-Convex lens

115 116 117 118‧‧‧高頻寬光電檢測器(High Bandwidth Photodiode) 115 116 117 118‧‧‧High-bandwidth Photodiode

119 120 121 122‧‧‧低雜訊放大器(Low Noise Amplifier LNA) 119 120 121 122‧‧‧Low Noise Amplifier (LNA)

123 124 125 126‧‧‧資料比較器(Data Comparator) 123 124 125 126‧‧‧Data Comparator

127‧‧‧正交分頻多工分析儀(OFDM Analyzer) 127‧‧‧Orthogonal Frequency Division Multiplex Analyzer (OFDM Analyzer)

Claims (5)

一基於垂直共振腔面射型雷射與空間光調變器整合多重輸入多重輸出可見光通訊系統，包含：一任意波行產生器、一垂直共振腔面射型雷射、四組空間光調變器、八組平-凸透鏡、四組高頻寬光電檢測器、四組低雜訊放大器、四組資料比較器、一OFDM分析儀；其中，由一任意波行產生器產生一16-正交振幅調變(QAM)正交分頻多工(OFDM)並直接調變一垂直共振腔面射型雷射並以線性度最佳之電流值驅動，因該垂直共振腔面射型雷射發射出的光源為發散，所以分別將發散光源入射四組空間光調變器使之達到分割空間的多工方式(Space Division Demultiplexing)，該四組空間光調變器模擬成動態凸透鏡將光束傳輸1.5公尺後透過第一階段四組平-凸透鏡將光束轉換成四道平行光，該四道平行光傳送若干公尺再藉由第二階段四組平-凸透鏡分別將四道平行光束聚焦於四組高頻寬光電檢測器，藉由該高頻寬光電檢測器將光訊號轉換成電訊號後藉由四組低雜訊放大器分別將四組電訊號放大與抑制雜訊，再經由四組資料比較器將四組訊號比對與濾除雜訊再將該四組資料輸出至一OFDM分析儀進行資料的品質測試與分析。 A multi-input multiple-output visible light communication system based on a vertical cavity surface-emitting laser and a spatial light modulator, comprising: an arbitrary wave line generator, a vertical cavity surface-emitting laser, and four sets of spatial light modulation , eight sets of plano-convex lenses, four sets of high frequency wide photodetectors, four sets of low noise amplifiers, four sets of data comparators, an OFDM analyzer; wherein a 16-quadrature amplitude modulation is generated by an arbitrary line generator Variable (QAM) Orthogonal Frequency Division Multiplexing (OFDM) and directly modulate a vertical cavity surface-emitting laser and is driven by the linearity optimum current value due to the vertical cavity surface-emitting laser emission The light source is divergent, so the divergent light source is incident on the four sets of spatial light modulators to achieve the space division multiplex mode (Space Division Demultiplexing), and the four sets of spatial light modulators are simulated into dynamic convex lenses to transmit the beam by 1.5 meters. Then, through the first stage four sets of plano-convex lenses, the beam is converted into four parallel lights, the four parallel lights are transmitted by several meters, and then the four parallel beams are respectively focused by the second stage four sets of plano-convex lenses to four sets of high frequency widths. Light The electric detector converts the optical signal into a telecommunication signal by the high-frequency wide photodetector, and then amplifies and suppresses the four sets of electric signals by four sets of low noise amplifiers, and then four sets of signals through four sets of data comparators. Compare and filter the noise and then output the four sets of data to an OFDM analyzer for quality testing and analysis of the data. 如申請專利範圍第1項所述一基於垂直共振腔面射型雷射與空間光調變器整合多重輸入多重輸出可見光通訊系統，其中該垂直共振腔面射型雷射產生發散之光束，並由四組空間光調變器接收，以達到多重輸入的效果。 A multi-input multiple-output visible light communication system based on a vertical cavity surface-emitting laser and a spatial light modulator according to the first aspect of the patent application, wherein the vertical cavity surface-emitting laser generates a divergent beam, and Received by four sets of spatial light modulators to achieve multiple input effects. 如申請專利範圍第1項所述一基於垂直共振腔面射型雷射與空間光調變 器整合多重輸入多重輸出可見光通訊系統，其中該四組低雜訊放大器與四組資料比較器的阻抗匹配與特性相容，以達到傳輸通道的最佳化。 As described in the first paragraph of the patent application, a vertical cavity-based laser and spatial light modulation The device integrates multiple input multiple output visible light communication systems, wherein the four sets of low noise amplifiers are compatible with the impedance matching and characteristics of the four sets of data comparators to optimize the transmission channel. 如申請專利範圍第1項所述一基於垂直共振腔面射型雷射與空間光調變器整合多重輸入多重輸出可見光通訊系統，其中該任意波行產生器產生一訊號然後藉由直接調變的方式將訊號調製至該垂直共振腔面射型雷射，而調變的訊號並不侷限數位訊號或者類比訊號。 A multi-input multiple-output visible light communication system based on a vertical cavity surface-emitting laser and a spatial light modulator according to the first aspect of the patent application, wherein the arbitrary wave line generator generates a signal and then directly modulates The way to modulate the signal to the vertical cavity surface-emitting laser, and the modulated signal is not limited to a digital signal or analog signal. 如申請專利範圍第1項所述一基於垂直共振腔面射型雷射與空間光調變器整合多重輸入多重輸出可見光通訊系統，其中該垂直共振腔面射型雷射的光束發散角為16±2°而輸出光功率為1.7mW~2.7mW。 A multi-input multiple-output visible light communication system based on a vertical cavity surface-emitting laser and a spatial light modulator according to the first aspect of the patent application, wherein the vertical cavity surface-emitting laser has a beam divergence angle of 16 ±2° and output optical power is 1.7mW to 2.7mW.
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