All-optical digital logic elementary circuits are the building blocks of many important computational operations in future high-speed all-optical networks and computing systems. Multifunetional and reconfigurable logic units are essential in this respect. Employing the demodulation properties of delay interferometers for input differential phase shift keying signals and the gain saturation effect in two parallel semiconductor optical amplifiers, a novel design of 40 Cbit/s reconfigurable all-optical dual-directional half-subtractor is proposed and demonstrated. All output logic results show that the scheme achieves over 11=dB extinction ratio, clear and wide open eye diagram, as well as low polarization dependence (〈 1 dB), without using any additional input light beam. The scheme may provide a promising candidate for future ultrafast all-optical signal processing applications.
Carrier recovery time is a key parameter that determines the performance of a semiconductor optical amplifier (SOA). A measurement method of carrier recovery time in SOA based on a nearly degenerate four-wave mixing of narrowband amplified spontaneous emission (ASE) spectra is presented. The results show the carrier times are 50.2, 44.6, and 23.6 ps when the injected currents are 120, 180, and 240 mA, respectively, which are in agreement with the nominal values of the sample.
Format conversion is enabling function at the interface of different networks with different optimal modulation formats.Meanwhile,multi-channel signal processing function has its special significance for dense wavelength division multiplexing networks.In this paper,we designed and fabricated a delay interferometer cascaded with an arrayed-waveguide grating based on silicon on insulator.The 4-channel return-to-zero on-off keying(RZ-OOK) to non-return-to-zero on-off keying(NRZ-OOK) and return-to-zero differential phase shift keying(RZ-DPSK) to non-return-to-zero differential phase shift keying(NRZ-DPSK) format conversions at 40 Gbit/s were realized with this integrated device,the output eye diagrams showed a good conversion performance.Thanks to the mature fabrication technology,this device shows great potential for its small size,low power consumption and possibility of monolithic integration.
High-speed all-optical logic circuits have attracted much attention because of their important roles in signal processing in next-generation optical networks.The digital encoder is widely used in binary calculation,multiplexing,demultiplexing,address recognition and data encryption.A priority encoder allows the existence of multiple valid inputs simultaneously,identifies the priority of the request signals and encodes the priority.We propose and experimentally demonstrate an all-optical 4-bit priority encoder for return-to-zero signals at 40 Gbit/s based on cross-gain modulation in semiconductor optical amplifiers.Detuning fil-ters after semiconductor optical amplifiers are employed to improve the output performance.Correct logic bit sequences and clear open eye patterns with extinction ratios exceeding 10 dB are achieved.
LEI Lei DONG JianJi ZHANG Yin YU Yu ZHANG XinLiang