Study On All-optical Format Conversion

All-optical network is to achieve transmission and exchange of the information in the optical domain, not in the traditional electric field. The entire process of transmitting the data from the transmitter to the receiver, only using optical signals, which means that each node in all-optical networks has no optical/electrical and electrical/optical conversion. Since the information transfer process does not require the electronic devices, the signal transmission speed will be greatly enhanced.As one of the key technology of all optical communication networks, all-optical format conversion is mainly used to connection between different optical networks. To achieve the ultra high speed and large capacity data communications, there are widely use the wavelength division multiplexing optical fiber communication system (OWDM) and optical time division multiplexing (OTDM) technology. Different modulation formats will be selected in different network. In order to achieve mutual communication between these networks, which makes the whole optical network unobstructed, it must implement format conversions between different these networks. This paper uses microring resonator to realizing an all-optical format conversion, and the result after the conversion is detailed studied.Firstly, the development history of format conversion and the research status are summarized; analysis the different format modulations in optical communications through eye-diagram and the spectrum by making the comparison of each other; the principles and the schemes of format conversion between all-optical RZ and NRZ signal are detailed summarized and then present the scheme that using the microring resonator to the format conversion.Secondly, an all-optical return-to-zero (RZ) to non-return-to-zero (NRZ) format conversion is realized by using a micro-ring resonator with the comb transmission spectrum and a narrow bandpass filter. Influences of devices’parameters, such as different narrow band pass filters, coupling conditions of micro-ring resonator and duty ratio of the RZ input signal, on eye-diagram quality of converted NRZ signal are investigated detailedly. In addition, by reducing the ring-resonator radius, the designed RZ-to-NRZ format converter is compatible with the higher optical networks.Finally, the transmission characteristic of serial microring resonator was analyzed, and the add/drop microring resonator is used to construct a narrow-band filters, improved format converter, and analysis the effect of different conditions on the conversion results. Then, use serial micro-ring resonator structure, design the high-order narrow-band filter. And the2-order Butterworth narrow-band filter is designed, as the format conversion filter, and the result showed that2-order Butterworth has better performance. Special structure of the micro-ring, making the format converter has a better integrated features, which has great significance for all optical networks.