0733-8724 (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/JLT.2016.2623759, Journal of Lightwave Technology > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract—Visible light communication (VLC) systems can achieve a higher data rate by increasing the number of channels using wavelength division multiplexing (WDM) technology. In this paper, we investigate the maximum number of channels and possible data rate in a WDM-VLC system based on light emitting diode (LED). Channel crosstalk from the spectral overlap of LEDs is analyzed by modeling LED spectra and the formula for crosstalk is derived from VLC link, including optical filter transmittance and detector spectral response. An experimental set-up with different wavelength of LEDs is used to confirm the validity of the crosstalk analysis. The number of channels and data rate are determined by the SNR including signal power, channel crosstalk and detector noise. The results indicate that for indoor illumination standard with on-off keying (OOK) modulation and 33 nm channel spacing to achieve a BER of 10 -6 , the maximum and optimal numbers of channels are 12 and 10, respectively. Additionally, the achievable data rate is 5.1Gbps which is about 9.3 times compared with the single channel system. Index Terms—Multichannel communication, channel crosstalk, LED spectrum model, number of channels I. INTRODUCTION ECENTLY, with the increasing demands on mobile network devices, the over-crowded radio frequency (RF) bandwidth, and the wide implementation of solid state lighting, visible light communication (VLC) has become an attractive research area and is seen as a potential solution to enhance conventional wireless communication systems [1,2]. Because of the high efficiency, low cost, large field of view and relatively high modulation bandwidth, light emitting diodes (LEDs) have been identified as the most suitable component for VLC, providing high quality illumination and high capacity communication simultaneously [3,4]. Fundamental research has shown the feasibility of VLC using LEDs [5, 6]. To increase the data rate of VLC system, multiplexing technology is widely used visible light communication system such as WDM and MIMO [7-13]. In 2014, A 4 × 4 non-imaging indoor MIMO system has been reported with 50Mbps [7]. And a 920Mbps data rate has been achieved using four parallel channels based on imaging-MIMO VLC system [8]. WDM-VLC systems, based on RGB LEDs and RGBY LEDs, have shown great improvement over single Yi Tang is with the Beijing Institute of Technology, Beijing, Zhongguancun South Street 5 China (phone: 8610-68912575; e-mail： tangyi4510@bit.edu.cn). channel VLC systems [9-13]. The off-line data rate of 4.5Gbps and 5.6Gbps using discrete multi-tone (DMT) modulation based on RGB WDM-VLC system at BER=3.8 ×10 -3 have been reported [11,12]. And an off-line 8Gbps data rate with high-order CAP modulation at BER=3.8 × 10 -3 has been achieved in 2015, which is based on RGBY WDM-VLC system [13]. It can be seen that the data rate of WDM system is much higher than MIMO system. Moreover, for the visible light band of 400 nm to 760 nm, there is available capacity to further increase the number of channels for higher data rate. In a WDM-VLC system, optical filters are used to differentiate among various channels at the receiver [13]. However, with the increase of the number of channels, channel crosstalk becomes a serious issue because the LEDs’ spectra will overlap and optical filters cannot distinguish the overlapping areas in spectra. Some previous analysis about crosstalk in WDM-VLC system have been reported based on CSK modulation [14]. In this paper, the optimum number of channels and possible data rate are investigated by investigating the channel crosstalk. A multichannel LED VLC-WDM system is proposed and the channel crosstalk is analyzed by modeling LED spectra. A crosstalk formula is derived for a VLC link, taking into account the optical filter transmittance and detector spectral response. An experiment with different peak wavelengths of LEDs verified the correctness of the crosstalk analysis. Finally, the number of channels and possible data rate are determined by the SNR, with consideration of signal power, crosstalk, ambient light and detector noises. The results indicate that conforming to indoor illumination standard, with on-off keying (OOK) modulation at a BER of 10 -6 , the system can accommodate up to 12 channels with a channel spacing of 33 nm. The highest data rate of 5.1 Gbps can be reached at an optimum number of channels of 10. II. MULTICHANNEL LED WDM-VLC SYSTEM The scenarios of proposed WDM-VLC system are depicted in Fig. 1. For transmitters, the visible light band is divided into many communication channels using different single-color LEDs. The light will be mixed into white, or other specific colors, in free space and received after propagating a certain distance. At the receiver side, the corresponding detectors for each channel are used to detect signals of defined wavelengths through narrow bandpass filters. III. CHANNEL CROSSTALK ANALYSIS For an intensity modulation and direct detection (IM/DD) Analysis of the Multichannel WDM -VLC Communication System Lu Cui, Yi Tang, Huiping Jia, Jiabin Luo and Bruce Gnade R