Star L quadrature amplitude modulation (SLQAM, L representing the number of constellation points) modulated orthogonal frequency division multiplexing (OFDM) is applied to the optical domain for the first time. Numerical simulations are conducted between an S16QAM and a square 16QAM modulated optical OFDM system to compare the tolerance toward various transmission penalties in a 30.2-Gbit/s coherent optical OFDM (CO-OFDM) system over 640, 720, and 800 km. After 640-km transmission, the optimal launch power and corresponding Q2 factor of an S16QAM modulated optical OFDM signal are 2 and 0.6 dB higher, respectively, than the square 16QAM modulated OFDM signal in a 30.2-Gbit/s single-channel single-polarization CO-OFDM system, while in a 5×30.2-Gbit/s wavelength-division multiplexing single-polarization CO-OFDM system, the optimal launch power and corresponding Q2 factor of an S16QAM modulated optical OFDM signal are 1 and 0.7 dB higher than with a square 16QAM modulated OFDM signal, showing increased tolerance toward nonlinearity such as SPM and XPM.
In this paper, we present a simple marker pulse extraction scheme using a modified terahertz optical asymmetric demultiplexer and experimentally demonstrate marker pulse extraction from 20Gbit/s all "1" packet. Particular attention is given to eliminate the effects of polarization rotation in semiconductor optical amplifier.
This paper analysis the spectral characteristics of optical pulse amplifications in semiconductor optical amplifiers under transparent assist light injection, comparison with the gain region light injection is also been given. It is shown that gain region light can decrease the spectral broadening and shifting, while transparent light can’t improve the spectral distortion though it can accelerate the carrier recovery. The effect of the assist light’s power, shape and initial frequency chirp of the input pulses on the shape and the spectrum of the amplified pulse are discussed in detail. The relationship of the maximum spectral shifting with the amplifier’s length, bias current is also been given, particular attention is paid to the difference in co- and counter-propagating assist light injection.
In this paper, we present a technique, using packet compressor, to perform both compression and decompression of optical time division multiplexed (OTDM) packets. The compressor is based on optical fiber delay line, and we design a mathematical model for the compressor. With this model, we discuss several questions associated with the compressor, such as Link Budget, Differentia Budget, and Effects of Time-out. At last, compression of 2.5Gbit/s 16bit packet to 100Gbit/s is experimentally demonstrated.