A cost-effective ROF system employing FBG and DML to generate optical mm-wave

Abstract

Abstract-We have investigated and experimentally demonstrated aROF system employing FBG and low-cost DML to generate an optical mm-wave. We employ FBG because the bandwidth of the optical modulator is largely reduced and the architecture of the ROF system is simpler. Because no expensive broadband external modulator is used, the overall system is considered as a cost-effective solution. This novel scheme employs low-cost DML to generate an mm-wave signal which is a practical scheme to be applied for future broadband access networks.Recently ROF techniques have become attractive solutions in realizing future broadband wireless networks to provide large capacity and high flexibility [1][2][3][4][5] because they can be used for the distribution of wireless signals which grow very fast. To reduce the total cost and make simpler configuration of the ROF system sand connect as many users as possible, novel schemes of wavelength reuse or centralized light-waves in the CO have been proposed and experimentally demonstrated in [6][7][8][9]. To realize optical millimeter-wave generation, many techniques have been reported, such as the frequency up-conversions using four-wave mixing [10], cross-gain modulation in a semiconductor amplifier [11][12][13], and frequency doubling using optical carrier suppression modulation [14][15]. When compared with an optical external modulator, the DML is cost-efficient and has a higher output power. For 40GHz optical mm-wave signal generation, only 20GHz optical and electrical components are required, because the generated optical mm-wave signal will be up to 40GHz after it is separated from the optical carrier by using FBG [16]. We employ FBG because the bandwidth of the optical modulator is largely reduced and the architecture of the ROF system is simpler. The ROF system which based on DML to generate an optical mm-wave carrying OOK signal has been introduced [17]. In this letter, we have investigated and experimentally demonstrated an ROF system employing FBG and low-cost DML to generate an optical mm-wave. A theoretical demonstration analysis of the proposed system is also presented. It can be considered as a very simple and cost-effective solution because a low RF oscillator is employed to generate an optical mmwave signal with frequency duplication. * E-mail: viet02342000@yahoo.com Table 1 shows the ROF system parameters. In this system, the expensive broadband external modulator is removed. We employ a high-frequency electrical mixer to generate RF signals which are employed to drive the DML to generate a DSB optical mm-wave.In the real system, there are some higher harmonics because of the nonlinearity of the DML, but they are too small to be considered. The 2.5Gb/s baseband signal is mixed with a 20GHz sinusoidal wave to realize sub-carrier modulation (SCM) and then the mixed signals are employed to drive DML to generate DSB optical signals. The waveform output of the DML which is driven by a mixing RF signal f(t)cosω l t can be approximately represented by G(t) which has an optic...