A study on input power dynamic range enhancement of a cross phase modulation wavelength converter

Abstract

This thesis presents two novel and simple methods to reduce the power penalty of the Mach-Zhender interferometer (MZI) cross phase modulation (XPM) wavelength converter. Power penalty is an important parameter because it is directly related to input power dynamic range of wavelength converter and input power dynamic range of wavelength converter is a crucial parameter to determine the operating performance for diverse system applications. Input power dynamic range of the interferometric wavelength converter is only 3-4 dB at 10 Gbit/s. [1] In method I, the relation of the injected optical powers of input signal and CW light for a conventional MZI XPM wavelength converter is simulated using VPI simulation tool. The purpose is to obtain the optimal input signal and CW light power pairs in terms of the power penalty based on the bit error rate. The wavelengths of the input signal and the CW light used in this simulation were 1552.5 nm and 1548.5 nm, respectively, and the wavelength conversion range is 4 nm downward direction. The input signal is intensity-modulated at a bit rate of 2.5 Gbit/s with nonreturn-to-zero (NRZ) pseudorandom binary sequences (PRBS) of length $2^{23-1}$. Power penalty is greatly reduced when optimal CW power is used. From -10 dBm to 50 dBm of input power, power penalty is within 2 dB. Simulated input power dynamic of the XPM MZI wavelength converter is 8dB at 2.5 Gbit/s. If the CW light power can be controlled according to the simulated best pairs, the input power dynamic range is over 30 dB at 2 dB power penalty. (Input signal power : -10~20 dBm) In method II, simulation conditions are almost same as those of the first method except that SOA2 current is variable and CW light power is fixed. That is, CW light power is variable in the first method whereas SOA2 current is variable in the second method. The purpose is to obtain the optimal input signal power and SOA2 current pairs in terms of the power penalty based on the bit error rate....