The routing decision functionality by all-optically interconnecting semiconductor-based all-optical logic gates and flip-flops is demonstrated in the frame of an all-optical packet switching network. We experimentally show that the output of the all-optical 2-bit correlator is capable of toggling the states of the integrated flip-flop every 2.5 ns via an adaptation stage. High extinction ratios are obtained at the output of the flip-flop, which can be used to feed a high-speed wavelength converter to complete the routing functionality of the AOLS node. The potential integration of these SOA-MZI based devices make the proposed approach a very interesting solution for future packet switched optical networks.
In this paper is proposed a novel high spectral efficiency modulation scheme using time-squared pulses forming an orthogonal wavelength division multiplexing. Experimental results show a significant reduction of the interchannel linear crosstalk-induced penalty compared with Gaussian RZ modulation. Simulation studies are in good agreement with experimental results and show the system performance dependence on several multiplexing impairments inherent to this technique. The proposed modulation technique allows a maximum spectral efficiency of 1 bit/s/Hz without any other spectral efficiency enhancement technique like polarisation division multiplexing.
In this paper a spectral crosstalk monitoring technique is proposed and demonstrated. The technique is based on optically perform a real-time continuous Fourier Transform (OFT) comprising the whole set of transmitted wavelengths. This approach does not require to stop the channel operation. Once the spectral information has been brought to time domain, the basic parameters as amplitude (channel power) or central wavelength can be evaluated. This technique is theoretically developed and demonstrated in a three channel DWDM system at 10 GBit/s channel bitrate in a proof-of-concept experiment.
Future multi-terabit/s optical core networks require optical technologies capable of managing ultra-high bit rate OTDM/DWDM (optical time division multiplexing/dense wavelength division multiplexing) channels at 160 Gbit/s or higher bit rates. The key functionalities in ultra-high speed network nodes are all-optical wavelength conversion, 3R-regeneration and demultiplexing of OTDM signals. Advanced optical networking techniques (optical add-drop multiplexing and optical routing) are studied in simulations and their performance evaluated considering 160 Gbit/s OTDM/DWDM channels. Performance comparison results for both OADM (optical add-drop multiplexer) and OXC (optical cross-connect) node networking functionalities are shown considering different technologies: semiconductor-optical-amplifier-based symmetric Mach-Zehnder interferometers (SOA-MZI) for wavelength conversion, signal regeneration and demultiplexing, electroabsorption-modulator-based demultiplexers, and wavelength converters based on four-wave mixing in dispersion-shifted fiber. The simulation results show that the SOA-MZI is a promising technology for all-optical signal processing in network nodes mainly due to its signal regeneration capability. At ultra-high bit rates, however, the relaxation time of SOAs considerably limits the operation. A solution to mitigate this problem is to use a differential scheme at the input of the device. Error-free wavelength conversion, signal regeneration and demultiplexing of 160 Gbit/s OTDM signals employing a SOA-MZI with a differential scheme is demonstrated by means of simulations. Furthermore, the parameters of this architecture are optimized to obtain the best performance for each optical networking functionality in OADM and OXC network nodes.
There is an increasing interest in performing many key networking functions in the optical domain to achieve bit rate transparency. Optical header processing is one such key function that may enable fast reading and forwarding of optical packets in the future all-optical packet-switched core network. Many of these optical header processing functions are enabled through the use of all-optical logic gates. The logic XOR gate is of key importance in decision and comparator circuits. A novel architecture of an N-bit logic XOR gate based on a Mach-Zehnder interferometer with feedback is proposed and its performance evaluated by means of simulations. Basically, this architecture consists of an integrated semiconductor-optical-amplifier-based Mach-Zehnder interferometer (SOA-MZI), an optical pulsed control signal, a differential transmission scheme for the input data sequences, and a feedback network. The simulation results show error-free operation at 40 Gbit/s for 16-bit-length words with extinction ratio values better than 16 dB. Furthermore, simulation results of the data power threshold needed for obtaining error-free operation as a function of the peak power of the control pulses are also presented, showing an optimum operating point at about 8 mW. An important application for the proposed SOA-MZI architecture is label processing directly at the optical domain in high-speed all-optical label swapping networks.