Optik 125 (2014) 1864–1867 Contents lists available at ScienceDirect Optik j o ur nal hom epage: www.elsevier.de/ijleo Enhanced performance analysis of 10 Gbit/s optical OFDM-RoF transmission links Naresh Kumar a,∗ , Ajay K. Sharma b , Vinod Kapoor a a Electronics and Communication Engineering Department, National Institute of Technology, Hamirpur, H.P., India b Computer Science and Engineering Department, National Institute of Technology, Jalandhar, Punjab, India a r t i c l e i n f o Article history: Received 10 May 2013 Accepted 10 October 2013 Keywords: Orthogonal frequency division multiplexing (OFDM) Radio over fiber (RoF) Optical single side band Square root module Signal to noise ratio a b s t r a c t In this paper, we have presented analysis of 10 Gbit/s optical OFDM-RoF transmissions links with distance of 50 km and reported the improved performance by usage of a square root module (SQRT). © 2013 Elsevier GmbH. All rights reserved. 1. Introduction Radio over fiber (RoF) is a hybrid system having both fiber optic link and free-space radio path. In such RoF systems microwave data signals are modulated onto an optical carrier at a central station and then transported to remote sites or base station using optical fiber [1]. The base-stations then transmit the RF signals over small areas using microwave antennas. Such a system is important in number of applications including mobile, satellite communications, wire- less local area networks, mobile broadband service etc. [2]. OFDM is used extensively in broadband wired and wireless communication systems [3–5]. In OFDM, the received signal at any time depends on multiple transmitted symbols. In this case the equalization rises rapidly [6]. Combined RoF technology with optical OFDM system cannot only reduce multipath fading of wireless signals but also improves signal quality. Moreover, the systems have seamless cov- erage, increased channel capacity, transmission rate and simplify digital signal processing by means of adding more base stations [7]. Therefore, Optical OFDM system can be regarded as a specific deployment scheme of OFDM-RoF system. By this system, we can also improve the system flexibility and provide a very large cover- age area without increasing the cost and complexity of the system. Radio over fiber transmission performance of OFDM signals for dual-band of 2.4/5 GHz wireless LAN systems with very low-data ∗ Corresponding author. E-mail address: naresh.nitham@gmail.com (N. Kumar). rate have been evaluated [8,9]. An experimental demonstration of OFDM-RoF system for transmitting 1 Gbps OFDM signal on 40 GHz millimeter-wave carriers over 80 km SSM fiber is proposed and achieved less than 0.5 dB power penalty at BER of 10 -6 without dis- persion compensation [10]. We have proposed to use a square root transfer function module similar as reported in [11,12]. The square root module (SQRT) transfer function module has been placed after the photodiode which compensates its square law characteristic for improving the performance of linear equalizer [13]. In this paper we propose the simulative OFDM-RoF transmitter and receiver with optical fiber reported in Section 2. The simulation results have been discussed in Section 3. The conclusion of our simulative results is presented in Section 4. 2. System description In our proposed optical OFDM-RoF transmission links (Fig. 1), 10 Gbit/s QAM data is generated and then modulated into OFDM by means of OFDM modulator using 512 subcarriers and FFT size of 1024. These are then IQ modulated at an intermediate fre- quency of 7.5 GHz. Then OFDM analog signal is mixed with RF signal of 17.5 GHz through clock. This Intermediate signal mod- ulates directly the light of a continuous wave (CW) through Mach–Zehnder modulator (MZM). The light is then transmitted on single mode fiber. The attenuation of the fiber is 0.2 dB/km. After propagation the signal is converted optical to electrical through PIN photodiode. The electrical and optical sample spectra along the system are presented in Figs. 2 and 3. 0030-4026/$ – see front matter © 2013 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.ijleo.2013.10.037