1,721,027 research outputs found
OCDM systems with PSK and QAM codes
No full textA multiport encoder/decoder can simultaneously generate multiple PSK optical codes, and it has been effectively used in asynchronous, spectrally efficient access networks. To increase the system flexibility, as well as the number of simultaneous IoT signals, we introduce novel multi-level QAM orthogonal optical codes that are generated by the multiport encoder/decoder using optical phase modulators. The QPSK modulator simultaneously operates for data modulation and orthogonal code generation. The code orthogonality is improved, compared to conventional PSK codes, and we analyze the performance of 16-code × 10 GSymbol/s, OOK-, DPSK- and DQPSK-modulated OCDM systems, using conventional PSK and the proposed QAM codes
Design and performances of logarithmic wavelength demultiplexers
No full textWe investigate the performance and furnish design guideline for a 1×N router realized as a tree of Mach-Zehnder interferometers, with free-spectral ranges that follow a logarithmic progression. We show that the crosstalk can be reduced and the channel passband flattened by inserting all-pass (AP) filters in the interferometers arms, with a suitable choice of the coupling ratios. The proposed device is inherently low loss and the chromatic dispersion introduced by the AP filters can be easily compensated. Two different realizations are investigated, and the power penalties induced by losses and dispersion are evaluated numerically
On the performance of all-optical OFDM based PM-QPSK and PM-16QAM
No full textA polarization multiplexed all-optical orthogonal frequency division multiplexing (AO-OFDM) system is investigated analytically and numerically, with 12.5 Gbaud symbol rate, that is compatible with the International Telecommunication Union flexible grid. We demonstrate that fast adaptive filtering is not require at the receiver and chromatic dispersion with polarization mode dispersion can be compensated without the cyclic prefix insertion, with the maximum spectral efficiency by using proper optical filter. System performance are numerically and analytically evaluated considering nonlinear effects and power consumption, evidencing a good agreement between the theoretical model and numerical results. We compare AO-OFDM performance with coherent OFDM scheme using the derived theoretical formula and numerical results. 21 subcarriers are investigated with quadrature phase shift keying modulation and 7 subcarriers in case of 16-quadrature amplitude modulation, with a total capacity of 976.5 Gb/s and 651 Gb/s, respectively, considering 7% forward error correction overhead
Diffractive variable beam splitter: optimal design
No full textThe analytical expression of the phase profile of the optimum diffractive beam splitter with an arbitrary power ratio between the two output beams is derived. The phase function is obtained by an analytical optimization procedure such that the diffraction efficiency of the resulting optical element is the highest for an actual device. Comparisons are presented with the efficiency of a diffractive beam splitter specified by a sawtooth phase function and with the pertinent theoretical upper bound for this type of element. (C) 2000 Optical Society of America [S0740-3232(00)00701-8]
Generalized self-Fourier functions
No full textBy generalizing the definition of self-Fourier functions recently introduced by Caola, we show that any Fourier transformable function is the linear combination of four self-Fourier functions whose explicit form can be found
Secure DPSK-based M-ary block-ciphered multicarrier optical communication
No full textTo improve the physical-layer data confidentiality in short-reach optical networks, we have proposed an M-ary blockciphered system using an optical code multiplexing approach. In a previous system, each optical code (OC), that corresponds to a frequency subcarrier, was mapped onto one of the log2M bits, and the computational security is related to the correspondence between the bit-block and the OC, and the number of possible combinations equates M!. However, this system presents two critical issues (1) Computational Security: the number M of OCs that can be generated by an optical arrayed waveguide grating (AWG) is limited, due to the port number and the subcarrier crosstalk. (2) Physical security: a careful differential analysis of the corresponding time waveform, optical power, and/or optical spectrum can be used to identify the symbol pattern. To mitigate the effects of interchannel interference, we propose a new differential phase-shift keying (DPSK)-based multi-dimensional M-ary block ciphering system, that assigns binary phase difference patterns to adjacent symbols and demonstrate a 16-dimensional 216-ary ciphered system. In addition, to increase the M-ary number, without increasing the number of OCs, we consider also a differential quadrature phase-shift keying (DQPSK)-based multi-dimensional M-ary block ciphered system and demonstrate a 16-dimensional 232-ary ciphered system
Diffractive variable beam splitter: optimal design
No full textThe analytical expression of the phase profile of the optimum diffractive beam splitter with an arbitrary power ratio between the two output beams is derived. The phase function is obtained by an analytical optimization procedure such that the diffraction efficiency of the resulting optical element is the highest for an actual device. Comparisons are presented with the efficiency of a diffractive beam splitter specified by a sawtooth phase function and with the pertinent theoretical upper bound for this type of element
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