Study On Optical Frequency Multiplication Technology Based On Intensity Modulater And Mach-Zehnder Interferometer

1. IntroductionWith the information-based society, wireless communication technologies has been the rapid development. Broadband Wireless Communication Systems promote the development of the correspondence business.Today,the first importmont question of Broadband Wireless Communication Systems is increasing the capacity of wireless communication systems.One natural way is to increase capacity of wireless communication systems to deploy smaller cells ,Another way is to increase the carrier frequencies. Useing the smaller cells need many the BSs and the RAPs , this may lead to increase costs,and using the higher carrier frequencies can offer greater modulation bandwidth, this way not only may lead to increased costs but also take the lower efficiency and the higer vastage. Radio-over-Fibre Technique is in demand came into being, is the fiber-optic communications and wireless broadband communications perfect combination.Radio-over-Fibre Technique uses the fiber transmiting the RF,it can reduce the vastage,and this technique can predigest the structure of the RAUs,it can decrease the cost. In recent years, the ROF technique has become optical domain one popular research, especially the technique of delivering the microwave in the system OFM technique is a method by which a lower frequency signal is up-converted to a much higher microwave frequency,through E/O and periodic filtering .Now, people most use the periodic filtering such as the Mach-Zehnder Interferometer or the Fabry-Perot Interferometer,and the E/O such as the Optical Phase Modulatorand or a tunable laser with the sweep signal.The optic signal can be achieved by driving a tunable laser or by an a CW laser diode. In this text ,I introduced two kinds of OFM techniques: the OFM technique based on the MZI and the OFM System based on the FPI.Both systems generate odd and even harmonic components.2. Optical Frequency Multiplication Systems Based On Intensity Modulater And Mach-Zehnder InterferometerBecause of the LiNbO₃ Modulater broadand is enough and chirp parameter is effectde smaller ,we use it in the Optical Frequency Multiplication systems based on modulater and Mach-Zehnder interferometer. The low cost advantages and the smaller volume is the LiNbO₃ Modulater's another advantage ,so it can be production large-scale. In this text,we study on the Optical Frequency Multiplication technology based on the modulater and Mach-Zehnder interferometer.In the headend of the Optical Frequency Multiplication systems based on modulater and Mach-Zehnder interferometer,the optical signal and lower scan singal throught into the modulater,and receive the harmonic components by the periodic filtering of the Mach-Zehnder interferometer . For example,if =10GHz, we can receive 10GHz,20GHz,…,70GHz,in the range of 70GHz.we can control the scan signal and wave range according the signal we need. fSWIn reseach of the Optical Frequency Multiplication systems based on modulater and Mach-Zehnder interferometer.We find that it isn't be influenced by the laser phase noise.so it can't need the PLL and OIL. Furthermore, the strength of the haromonic component is influnced by the phase of the scan signal, the strength of the haromonic component is restrained. The analyse about the chromatic dispersion effects on the Optical Frequency Multiplication systems based on modulater and Mach-Zehnder interferometer of SMF, discover about 20 kilometers signal strength is better, and almost have not change to the strength in 40 kilometers scope, but in 40-50 kilometers of the attenuation is 11.8 dB. So, in the SMF system, the factors of effcting base on OFM of ROF system are attenuation and oscillateor phase noise, but not the chromatic dispersion. The span length of the IM-DD RoF system would be limited to less than 5 km,but the OFM system generating the same 30 GHz microwave signal, through a 5 GHz sweep signal getting, would extend beyond 50 km.OFM can be used in MMF ,but the attenuation is constrained..3. Conclusion We implement simulation on the OFM systems based on LiNbO3 Modulator andMach-Zehnder Interferometer, successfully realized the system signal output on intensity by using two simulation platform when the scan signal is 10GHz.It will result in seven index harmonic range in 70GHz,we can constrain odd index harmonic to enhance the even index harmonic.but cann't constrain even index harmonic to enhance the odd index harmonic We construct Radio-over-Fiber detect system from the OFM technology based on Modulato and Mach-Zehnder interferometer, for better to detect the OFM technology based on Modulator and Mach-Zehnder Interferometer performance in the microwave fiber optical transmission system.We analyse the quality of the signal through detecteing the spectrum diagram of output signal .Set digital signal with frequency of 500MHz as an example, we analyzed eye diagram which produced by signal pass the fiber link 10km,20km,50km, 70km and 80km on the15GHz signal respectively through Radio-over-Fiber system . We can draw the conclusion that the quality of signal is the best in the fiber link 20km ,and then, the tensile degree of eye diagram will decrease gradually with the increase of distance, the quality of signal is the better in the fiber link 50km ,but the quality of signal is wores in the father ,it acnn't be transmit 80km. In addition, we also analyzed the eye diagram with the same transmission distance but difference frequencies. In this paper, when the sweep signal frequencies are 5GHz, we realized the system signal 10GHz and 20GHz respectively and the transmission distance of digital signal is 50 km. From the observation we can learn that the tensile degree of eye diagram will be effected on the harmonic intensity . According to the above analysis, OFM technology based on Modulator and Mach-Zehnder Interferometer are realizable.