Abstract:We demonstrate a 40 Gb/s self-synchronizing, all-optical packet clock recovery circuit designed for efficient packet-mode traffic. The circuit locks instantaneously and enables sub-nanosecond packet spacing due to the low clock persistence time. A low-Q Fabry-Perot filter is used as a passive resonator tuned to the line-rate that generates a retimed clock-resembling signal. As a reshaping element, an optical power-limiting gate is incorporated to perform bitwise pulse equalization. Using two preamble bits, the clock is captured instantly and persists for the duration of the data packet increased by 16 bits. The performance of the circuit suggests its suitability for future all-optical packet-switched networks with reduced transmission overhead and fine network granularity.
We discuss how all-optical signal processing might play a role in future all-optical packet switched networks. We introduce a concept of optical packet switches that employ entirely all-optical signal processing technology. The optical packet switch is made out of three functional blocks: the optical header processing block, the optical memory block and the wavelength conversion block. The operation principle of the optical packet switch is explained. We show that these three functional blocks can be realized by using the nonlinearities of semiconductor optical amplifiers. Some technologies in these three functional blocks are described. The header processor is realized using a Terahertz Optical Asymmetric Demultiplexer. We also describe a header pre-processor to improve the extinction ratio of the header processor output. In the optical memory block, we show that an all-optical memory can be obtained by using twocoupled lasers that form a master-slave configuration. The state of the optical memory is distinguished by the wavelength of the master laser. We extend the concept to an optical memory can have multiple states. In the wavelength conversion block, we demonstrate a 160 Gbit/s wavelength conversion using a single semiconductor optical amplifier in combination with a well-designed optical bandpass filter. The semiconductor optical amplifier has a gain recovery time greater than 90 ps, which corresponds to a less than 20 GHz bandwidth for conventional wavelength conversion. We show that by properly using the optical bandpass filter, ultrafast dynamics in the semiconductor optical amplifier can be employed for wavelength conversion at ultrahigh bit-rates.
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