The Generation Scheme Of Ultra-wideband Signal Based On Semiconductor Optical Amplifier And Its Application Research

Ultra wideband(UWB)technology has been attracting great interest in broadband wireless communications and short-range sensor network because of its inherent features such as wide spectrum,high speed,low power consumption,high safety,immunity to multipath fading and accurate positioning.Due to the low power spectral density regulated by the Federal Communications Commission(FCC),the typical communication distance of a UWB wireless system is limited to only a few meters to tens of meters.In this way,UWB-over-fiber system combines the high speed and wide spectrum features of UWB with the low loss and long transmission distance of optical access technology.And it can increase the area of coverage and offer the availability different service co-existence.In this paper,the optical generation,flexible modulation and transmission performance of UWB signals over fiber system are studied.The innovative work can be described as follows:1.The approach to generate UWB doublet pulse in optical domain based on the gain saturation of a semiconductor amplifier(SOA)and the delay of optical delay line is proposed.The approach is simple and cost-effective.Because the generated UWB doublet signals operate at a single wavelength,so the dispersion management is relatively simple and effective when distributing the UWB signals over fiber.In addition,the central frequency of power spectral is within the low frequency range,which is resistant to multipath fading.At the same time,the simulation and experiment results show that the generated UWB doublet pulses have narrow spectral width which can comply with the FCC spectral requirements.2.Flexible modulations such as pulse amplitude modulation(PAM),on-off keying(OOK)and binary phase shift keying(BPSK)of UWB doublet signal using precoding techniques of digital signal processing(DSP)are demonstrated.The simulation results show that UWB doublet signals with BPSK modulation format have best resistance to the dispersion after 50km fiber transmission and UWB doublet signals with PAM modulation format is worst.After 50km single-mode fiber transmission,the power penalty of UWB doublet signals with BPSK modulation format is less than 0.6dB,the power penalty of UWB doublet signals with OOK modulation format is less about 1.1dB,and the power penalty of UWB doublet signals with PAM modulation format is about 2dB.3.The performance of the generated UWB doublet signals is studied in wavelength division multiplexing passive optical network(WDM-PON).The channel interactions of each channel are analyzed through the optical spectra and channel parameters.The simulation results show that UWB doublet signals with different modulation formats in WDM-PON have different channel characteristic.