Research On The Key Issues About Dual-Loop Optical Buffer

Buffering is an effective method to solve the packet contention in optical domain without the conversion of 'optical-electronic-optical (O/E/O)' and all-optical buffer becomes the key component in optical switching node. This dissertation focus on some key techniques of semiconductor optical amplifier (SOA) based dual-loop optical buffer. These conclusions can also be applicable for all the other SOA based re-circular all-optical buffers. What I have done during the PHD period are as follows:1. For the first time we drive the expression of output signal-to-noise ratio and noise figure in SOA based interferometer, present the concept of additive noise factor. The additive noise factor has relation with SOA's linewidth enhancement factor and it is always larger than one, which means that interferometer's output signal-to-noise is different under different working mode. Adopting feedback working mode we can obtain higher signal-to-noise ratio. The experimental results prove the correctness of theory analysis.2. Drive the relation between the requisite power of optical control pulse and input signal's power, SOA linewidth enhancement factor and small signal gain. The influence of fluctuation of optical control pulse's power on the nonlinear phase shift difference and output signal power is analyzed detailedly. The frame synchronization mode induced pulse chirp and distortion is discussed.3. For the first time a novel equalization method based on the optimization of an optical control pulse is proposed. By injecting a negative optical control pulse, the output power fluctuation of a packet pulse can be effectively reduced from 4.83dB to zero. By adopting this method the performance of DLOB is improved greatly and DLOB can be applied successfully to optical resilient packet ring.4. The erasable function of DLOB is accomplished by introducing another SOA to left fiber loop. Discuss the noise characteristic of dual-SOA based fiber ring. By introducing an assistant light to SOA the noise can be suppressed greatly. The 622Mb/s signal packet can be erased successfully after 13 circulations.5. Analyze the relation between packet width of signal packet that can be stored in DLOB and length of fiber loop. A novel MZ-DLOB configuration is presented for the first time which can enhance the buffer's memory depth from 50% to 100%. Drive the expression on the relation between leaking power and directional power gain. By adjusting SOA's principle state of polarization we can obtain the steady output state of polarization.6. For the first time we present a theoretical model to investigate the dual-wavelength signal storage in SOA based DLOB. When the overlapping area is less than half of pulse width, the pulse distortion is so little that it can be ignored. When the packet pulses of dual-wavelength overlap completely, the pulse distortion is the most severe so that the output peak power will be reduced by approximately 30%. The experimental results prove the correctness of this moded.