تجزیه و تحلیل عملکرد پیشرفته از لینک های انتقال OFDM-ROF نوری 10 Gbit / s

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).

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, wireless local area networks, mobile broadband service etc. [2]. OFDM is used extensively in broadband wired and wireless communication systems [3], [4] and [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 coverage, 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 coverage 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 rate have been evaluated [8] and [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 dispersion compensation [10]. We have proposed to use a square root transfer function module similar as reported in [11] and [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.

We have analyzed a 10 Gbit/s OFDM-RoF transmission system using 4QAM modulation with and without SQRT module. It is concluded that the introduction of a SQRT module has greatly improved the performance of the system as compare to without SQRT system. Further, due to the increase of SNR the distance coverage will also be increased.