The method of complete polar decomposition for arbitrary Mueller matrixes is introduced to analyze the birefringence vector induced in a fiber, and then based on the Mueller matrix （MM） method, three kinds of computation methods including the absolute, the relative, and the differential rotation methods are proposed and investigated in detail. A computer-controlled measure system is employed to measure the Mueller matrix and birefringence vector for a 2.5-km fiber system with length 5 mm under lateral press in complicated environment with much perturbation. Experimental results show that the differential rotation （DR） method is the optimal approach to achieve fiber birefringence vectors in a large dynamic range of lateral press on fibers in perturbed situations, which reaches the highest linearity of 0.9998 and average deviation below 2.5%. Further analyses demonstrate that the DR method is also available for accurate orientation of lateral press direction and the average deviation is about 1.1°.
A compact in-line fiber-based polarization controller(FPC)made of a rotatable fiber squeezer is investigated in detail with the Mueller matrix model established based on the generalized principal state of polarization(PSP).The PSP caused by the fiber squeezing is in the equator plane,which turns around S3 axis on the Poincarésphere when rotating the squeezer.Subsequently,a programmable polarization control method is proposed to realize the polarization conversion between arbitrary polarization states,in which only two parameters of phase shift and rotation angle need to be controlled.This type of FPC,which has a highly compact structure,lower insertion loss,and can be directly embedded into any fiber devices without any extra delay,will be an ideal PC for high-speed optical communication and all-optical signal processing.
LI Zheng-YongWU Chong-QingWANG Zhi-HaoQIN TaoWANG Yi-Xu
An optical time-domain differentiation scheme is proposed and demonstrated based on the intensive differential group delay in a high birefringence fibre waveguide. Results show that the differentiation waveforms agree well with the mathematically calculated derivatives. Both error and efficiency will increase when the birefringence fibre becomes longer, and the error rises up more quickly while the efficiency approaches to a maximum of ~0.25. By using a 1-m birefringence fibre a lower error of ~0.26% is obtained with an efficiency of 1% for the first-order differentiation of 10-ps Gaussian optical pulses, and the high-order optical differentiation up to 4th order is achieved with an error less than 3%. Due to its compact structure being easy to integrate and cascade into photonic circuits, our scheme has great potential for ultrafast signal processing.
