Study On Applications Of Optoelectronic Oscillators And Radio Over Fiber Technologies

Microwave photonics has played an important role in optical communication and optical fiber sensing in recent years.It combines the advantages of both microwave technology and photonic technology,and provides new possibilities for high-quality optical communication and fast-interrogation,high-resolution sensing.Compared with traditional electronic technology,microwave photonics has merits such as immunity to electromagnetic interference,wide bandwidth and high flexiblility.Aiming at the research hotspots and needs of microwave photonics technology in recent years,this paper has carried out theoretical and experimental research on signal generation and processing,optical fiber sensing and other issues in conjunction with optoelectric oscillators(OEOs)and radio over fiber(RoF)technologies.The main research results obtained are as follows:1.A frequency-doubled OEO based on a polarization-sensitive phase modulator(PM)is proposed,which can perform multiple clock recovery and demultiplexing on optical time division multiplexing(OTDM)signals.Multiple clock singals,including tributary clock signal,group clock signal and doubled clock signal can be extracted from a 20 Gb/s pulsed OTDM signal by this frequency-doubled OEO.Two-fold demultiplexing has also been successfully implemented.The OEO can also perform clock recovery,format conversion and serial-to-parallel conversion for non-return-to-zero signals,which is verified by experiment and shows the feasibility of the scheme.This scheme can avoid the problem of bias drift,and has the characteristics of high flexibility and low price.2.A fast-interrogation and high-resolution dispersion measurement scheme based on an OEO is carried out.The oscillating frequency of the OEO is determined by the difference in the length of the two arms of the Mach-Zehnder Interferometer(MZI)and the dispersion value of the device under test.When the dispersion value of the device under test in the loop changes,the oscillating frequency of the OEO will change,and the dispersion value of the device under test can be obtained from the oscillating frequency of OEO.The dispersion values of optical fibers with lengths ranging from 20 km to 100km are measured by the OEO and a commercial dispersion measurement system.The measurement result difference between the two methods is less than 3.2%.The scheme has a simple structure,fast interrogation speed and high resolution,and has wide applications in optical communication systems.3.An OEO for fast-interrogation and high-resolution displacement sensing is proposed.A pair of collimating lens is implanted into one arm of the MZI.The displacement between the collimating lenses determines the FSR of the interference spectrum of the MZI,which is finally mapped into the oscillating frequency of the OEO.The implantation of the collimating lens effectively increases the range of displacement sensing.Displacement sensing in the range from 0 to 12 mm is realized.The sensitivity of displacement sensing is 0.285 MHz/?m and the resolution is 0.07?m.The scheme has high sensitivity,fast measurement speed and good linearity,which can be applied to future displacement sensing systems.4.A dual-frequency OEO based on cascaded Fiber Bragg Grating-Fabry-Perot(FBG-FP)cavities is proposed,which can be used for curvature and temperature sensing.The wavelength of the FBG-FP cavity engraved on the twin-core fiber is curvature and temperature sensitive,but the wavelength of the FBG-FP cavity engraved on the ordinary single-mode fiber is only temperature sensitive.By observing the oscillating frequency of OEO,curvature and temperature information can be abstracted.Experimental results show that the sensitivities of curvature and temperature are-1.19 GHz/m^-1 and 1.14GHz/^oC,respectively.This scheme has the advantages of fast detection speed,high sensitivity and high resolution.5.A scheme for frequency shift keying(FSK)signal generation based on carrier phase-shifted double sideband(CPS-DSB)modulation is designed.The core part of the scheme is a pair of cascaded polarization-sensitive Li Nb O3 Mach-Zehnder Modulator and PM,whose polarization directions of the principal axes are mutually orthogonal to each other.A proof-of-concept experiment is carried out,where a 0.5 Gb/s FSK signal with the carrier frequencies of 4/8 GHz and a 1 Gb/s FSK signal with the carrier frequencies of8/16 GHz are generated successfully.This method relieves the required bandwidths for the electrical and optical devices and supports high-speed and wideband operation.6.A large-capacity and long-distance fixed-wireless millimeter wave access is designed.Intensity modulation,direct detection,as well as orthogonal frequency-division multiplexing(OFDM)signal are adopted.By using bit-loading algorithm,different quadrature amplitude modulation signals are applied to subcarriers with different signal to noise ratio caused by the un-ideal channels to maximize data throughput.Experiment results show that the millimeter wave signal can still reach up to 9 Gb/s after 25 km of transmission in the fiber under the forward error correction requirement.The access network is a potential candidate for future multi-gigabit/s networking with ubiquitous connectivity.