A Study Of All-optical Threshold Technique For 40Gb/s × 4 OCDM System

The OCDM+WDM hybrid-multiplexing technique promises a variety of attractive features for the Tb/s ultra-high capacity optical fiber transmission systems. All-optical pattern regeneration and recognition of the demultiplexed signal are key techniques in the hybrid-multiplexing optical networks. This paper presents the theoretical and experimental researches on all-optical hard threshold technique of the 6.4-Tb/s OCDM/WDM (40Gb/s×4 OCDM×40 WDM) transmission system. This configuration can be used for the OCDM demultiplexed signal recognition and noise reduction. Considering of cost and performance, an all-optical threshold technique constructed by a nonlinear optical loop mirror based on high nonlinear fiber is studied. The main contents are as follows: (1) The development trend of future optical communication network is introduced; the signification and the latest research progresses of all-optical hard threshold technique are addressed; Present the scheme of using the NOLM based on HNLF to realize all-optical hard threshold. (2) The 6.4-Tb/s OCDM/WDM transmission system and its key technologies are presented: Supercontinuum technique, 40Gb/s OCDM system and the all-optical hard threshold technique. The issues of all-optical hard threshold for the ultra-fast fiber communication networks are analyzed. (3) The evolution of the shape for the pulse transmitted in the HNLF is simulated numerically. The effects of the dispersion and nonlinearity of the fiber are analyzed. The measurement of the nonlinear ratio in optical fibers is demonstrated. (4) The principle and numerical model of all-optical hard threshold based on NOLM is presented. The intensity-dependent filtering of the NOLM is analyzed numerically, considering the parameters of the elements of NOLM, the shape of the signal, the nonlinearity and dispersion of the fiber, etc. (5) All-optical hard threshold based on NOLM is experimentally demonstrated. The transmission character of the hard threshold is tested respectively under the case of the continuum wave signal, the 2.5Gb/s small power signal and the 40Gb/s×4 OCDM decoded signal. The experimental results are in accordance with the theoretical simulation.