Crosstalk and contrast ratio studies of a four stage Mach–Zehnder optical fiber demultiplexer

In this paper, we report numerical studies of the propagation of ultrashort optical soliton pulses in a four-stage Mach–Zehnder interferometer (4SMZI), which is constructed with ordinary telecommunication fiber (OTF) and dispersion decreasing fibers (DDF), considering a linear profile. The performance of the 4SMZI was studied numerically considering the nonlinear soliton regime of operation. Results showed that the soliton transmission regime of the device is strongly dependent of the pump power. The crosstalk (X talk) level is dependent of the pump power and the dispersion of the fibers. For high pump power the X talk is lower for the 4SMZI operating with the DDF. For this configuration the minimum of the X talk level (−22.8 dB) is obtained for 2.7P0 of pump power. The extinction ratio (X ratio) is also very dependent on the pump power. It also degenerates with the increase of the pump power. For low pump powers the 4SMZI operating with ordinary fiber and DDF fibers presents better X ratio compared to high pump powers. One can say that the operation of the device as an optical switch is not improving with the use of the DDF fibers. However, for the multiplexing/demultiplexing operation, the proposed 4SMZI which is constructed with DDF, operating with optical solitons, is showing improvements in the X talk levels of operation of the device, results that may find applications in WDM systems and networks.