Ultrafast All-optical Wavelength Conversion Based On Semiconductor Optical Amplifiers

The invention of laser and a low-loss optical fiber triggered emergence and rapiddevelopment of optical fiber communications, but the bandwidth ’electronic bottleneck’ ofoptical-electrical-optical signal processing devices and systems employed in the currentoptical fiber communication network imposes serious restriction on the further expansionof the network. Future optical fiber communication networks will require the bandwidthof network nodes to match the transmission capacity of optical fibers, and transparent tothe modulation format, thus promoting the emergence and development of all-opticalsignal processing, in which, all-optical wavelength conversion is an important part of thereconfigurable, non-blocking wavelength division multiplexing (WDM) optical network.Among many nonlinear devices often used for all-optical wavelength conversion,semiconductor optical amplifiers (SOAs) demonstrate various advantages, like largenonlinear coefficient, small size, high potential for integration, and all-optical wavelengthconversion based on SOAs capable of high-speed processing with simple structure, lowpower consumption and transparency to modulation format, and has become one of themost popular research focuses in the field of all-optical signal processing.In this thesis, the development history and trends of optical fiber communications,recent advances and trends in all-optical wavelength conversion technology based onSOAs and the basic theory of SOA are presented. All-optical wavelength conversiontechnology based on SOAs is investigated and discussed in detail. Main content of thethesis is as below:1. Carrier rate equation and the optical field propagation equations of SOA arestudied; numerical model based on the finite-difference beam propagation method(FD-BPM) is developed, and all-optical wavelength conversion based on nonlineareffects of cross-gain modulation (XGM) and cross-phase modulation (XPM) in SOA issimulated with the different bitrates of non-return to zero (NRZ) and return to zero (RZ)signals. All-optical wavelength conversions10Gbit/s NRZ signal and high bitrates up to80Gbit/s of RZ signal based on SOAs are experimentally demonstrated.2. Causes and solutions for the slow part of gain recovery rate in all-optical wavelength conversion based on SOAs are analyzed, and up to4times of gain recoveryacceleration is experimentally achieved using cascaded SOAs structure (Turbo-switch).All-optical wavelength conversion of different bitrates of NRZ and RZ signals isdemonstrated, and wavelength conversion signal with an extinction ratio as high as11.5dB is obtained.3. An effective solution for the problem of overshoot in all-optical wavelengthconversion based on cascaded SOAs structure is proposed. Dividing the pump signal intotwo paths, and inputting one of them into the second SOA in the cascade SOAs structure,overshoot in the rising edge of the wavelength converted signal is completely eliminated,and all-optical wavelength conversion power penalty is reduced to0.3dB.4. A practical approach for monolithically integration of the cascaded SOAsstructure, and feasibility of the approach is experimentally verified with discrete devices.