Studies On All-optical Signal Processing Technologies Suitable For Elastic Optical Networks

With its ultra high processing speed, all optical signal processing could overcome the bottleneck of electrical signal processing, it is enabling technology to implement future next generation elastic and flexible all optical communication network. Presently, the newly emerged elastic optical network broked the limition of the traditional fix-grid WDM network, improved the network transmittability, spectrum resource efficiency and network flexibility, it is becoming a very promising architecture for next generation optical network. All optical signal processing technologies that suitable for elastic optical network, such as flexible optical signal multicasting, modulation transparent format conversion, optical logic gates, all optical wavelength exchange and optical regeneration could offer an indispensable physical layer technological support and gurantee for solving the key problems in elastic optical network like spectrum defragmentation, route and spectrum resource allocation, traffic grooming, survivability strategy, rate and bandwidth flexible signal transmitter and elastic bandwidth switching in intermediate nodes, etc. With the wide use of high-order modulation formats in elastic optical network, the capability of processing these kinds of formats will have more significance in practical network environment,they are also hot topics and difficultis in academic area.In combination with the characteristics of the elastic optical networks, this dissertation focuses on the research of all optical signal-processing technologies that suitable for elastic optical network.The innovations and achievements are as following:Firstly, we propose and exprimently demonsrate a single channel QPSK wavelength multicasting scheme. Using semiconductor optical amplifier (SOA) as the nonlinear medium we achieved 1-to-6 QPSK signal wavelength multicasting. At the same time, we proposed the concept of multichannel wavelength multicasting and exprimently implemented a two channels wavelength multicasting scheme, achieved 1-2 and 1-5 multicast output for the two input QPSK signals, respectively.Wavelength flexible multicasting technology will be helpful to support and solve the traffic grooming, spectrum defragmentation, routing and spectrum allocation problems in elastic optical networks from the physical layer, the whole network throughput and efficiency can be improved.Secondly, starting from the Maxwell equations, we derived the transmission equations and established the degenerate four-wave mixing process model in SOA, fully considered the influence of each light. Based on this model, we simulated a 8QAM and 16QAM signal generation scheme using one QPSK signal and one phase-offset ASK signal. Also,we proposed and exprimently implemented a two channel DQPSK-DPSK format conversion scheme. Format conversion technology can solve the interconnection and interworking problem between two networks that employing different modulation format, and effectively support the bandwidth and modulation self-adaption strategy in elastic optical network.Thirdly, a scheme of simultaneous multichannel wavelength multicasting (MWM) and exclusive-OR logic gate multicasting(XOR-LGM) for three lOGbps non-return-to-zero differential phase-shift-keying (NRZ-DPSK) signals in Quantum Dot semiconductor optical amplifier (QD-SOA) by exploiting the four-wave mixing (FWM)process is proposed and experimental demonstraed. No additional pump is needed in the scheme. Through the interaction of the input three lOGbps DPSK signal lights in QD-SOA, each channel is successfully multicasted to three wavelengths (1-to-3 for each), totally 3-to-9 multichannel wavelength multicasting (MWM), and at the same time,three-output XOR logic gate multicasting (XOR-LGM) is obtained at three different wavelengths. To further prove expansibility of the scheme,we then proposed and exprimentaly demonstrated a scheme of multi-channel XOR gate for four input DPSK signals, in this scheme we achieved two-channel XOR gate ouput for arbitrary three channels of the four input signals. Optical logic gate is useful in addressing, switching,data encryption or decryption, and network coding in elastic optical network, with logic gate technology the network survivability can be effectively improved.Fourthly, a proposed polarization insensitive wavelength exchange scheme in highly nonlinear fibre using polarization insensitive fiber loop is demonstrated by experiments. We successfully achieved the wavelength exchange of QPSK and 16QAM signals. By employing wavelength exchange technology, the efficiency of wavelength conversion can be improved resulting in an improved wavelength and routing selection efficiency and finally leading to a promoted flexibility in elastic optical network.Fifthly, we propose a scheme of polarization insensitivity optical signal regeneration scheme using one-mode phase sensitive amplifier(PSA) in highly nonlinear fiber (HNLF). When using a 100MHz radio source to drive the phase modulator to add phase noise to the original input QPSK signal, we also can obtain a clear output BPSK constellation.On the other hand, when using phase insensitive amplifier (PIA) scheme the phase noise in the output BPSK signal is obvious. System polarization insensitivity was achieved by using the polarization insensitive fiber loop architecture. With signal regeneration, the signal quality can be improved and the transmission distance can be extended, it has a great significance for elastic optical network.