| In modern communication systems,radio frequency is widely used.However,as wireless network traffic increases,RF spectrum is no longer able to meet the growing demand for greater bandwidth.Therefore,visible light communication has gained wide attention as an alternative to radio frequency communication.Visible light communica-tion has the following advantages,such as free spectrum licensing,antielectromagnetic interference and high directivity,which can also be used for secure communication and precise positioning.Meanwhile,it is possible to joint lighting and communication.Most of the receiving ends of visible light communication use photodetectors,and the use of light-emitting diodes as photodetectors has gradually attracted much attention because of its unique response characteristics.This paper mainly studies the response characteristics and communication perfor-mance of LEDs as visible light detectors.As a device with both luminescence charac-teristics and spectrally selective reception characteristics,the light-emitting diode has a photoelectric responsive principle similar to that of a photodiode.We explore the photoelectric and electro-optic effects of LEDs,including the operating principle in op-toelectronic mode,noise and impedance characteristics,spectrally selective response,and frequency responsive nonlinearity.Based on the response characteristics of LEDs,this paper proposes a cascaded RGB LED series detector.Based on experiments and analysis,the detector exhibits similar characteristics to multi-pole phototransistors and can control its response char-acteristics by varying the color components of the input optical signal.The response to the red and green AC signals can be effectively suppressed by the DC input of the green and red light,respectively,while the blue AC signal response can be enhanced by the red and green DC input light.It is therefore suitable for the detection of blue light signals in white LED-based VLC communication systems,as well as future programmable opti-cal interconnections between integrated chips or VLC-based IoT applications and chips.The theoretical results are self-consistent with the experimental results,which verifies the accuracy of the current source model with the optical power dependent impedance.It provides us a theoretical basis for the detection characteristics of RGB series LEDs in more complex interference situations.After experimental analysis and testing of the white LED as the photovoltaic cell,a self-powered low-light LED-LED communication scheme for future light-based IoT links is proposed,in which the power of the driving system can be extracted from the white LED module.By constructing weak light LED-LED VLC link,we achieved a bit rate of up to 10 Mbps with a low-light condition of no more than 100μW,and the modulation method uses 16-PPM.In the scenario where the communication rate exceeds 10 Mbps,the LED-LED link can achieve a bit rate of 40 Mbps by using OOK modulation,and the corresponding received optical power only needs to be higher than 9.72μW.Our LED-LED links can select different modulation modes depending on the communication scenario.PPM modulation can be selected for weak light scenes.OOK modulation can be considered when the data rate requirements are prioritized over the illumination limits. |
