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Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Optik - International Journal for Light and Electron Optics, Volume 124, Issue 17, September 2013, Pages 2758–2763
In this paper, a highly spectrally efficient scheme orthogonal wavelength division multiplexing with coherent detection (Co-OWDM) is analyzed. We study the effect of channel spacing on inter-channel crosstalk induced power penalty and on decision threshold Q-factor; effect of number of channels on Q-factor is also discussed. Results obtained with coherent detection are compared with direct detection technique. We also analyzed Co-OWDM with quadrature phase shift keying (QPSK) technique, passive micro-optics based 90° optic is used for coherent detection in this technique. QPSK based Co-OWDM system performance is analyzed in terms of bit error rate (BER) and quality factor.
The revolution in high bandwidth applications and the explosive growth of the internet have created capacity demands that exceed traditional TDM limits. Technologies such as wavelength division multiplexing (WDM) and dense wavelength division multiplexing (DWDM) have been developed to meet exponentially growing bandwidth demands. In addition, high spectral efficiency (SE) can effectively increase the aggregate capacity without resorting to expanding the bandwidth of optical amplifiers. There are two ways to increase SE in optical transmission for which coherent detection is ideally suited. One way is to use advanced modulation formats so that each symbol transmits multiple bits of information. The other way is to pack WDM channels closer together . The price paid in the latter option is increased crosstalk. In dense DWDM networks, optical orthogonal techniques are required to enhance the receiver performance. Orthogonal wavelength division multiplexing (OWDM) is another high spectral efficient DWDM scheme in which channels are allowed to overlap without interfering each other . This condition can be achieved only when channel spacing is precisely set equal to the symbol rate; in this case linear crosstalk induced from adjacent channel presents a deep power notch at the central frequency of the channel under study. Inter-channel crosstalk can be completely eliminated if square pulses are used as transmission signals and samples are taken at center of the pulses at the receiver. Coherent detection can further improve the receiver sensitivity compared with the direct detection with an advantage of ultra narrow optical filtering .
نتیجه گیری انگلیسی
We analyze the feasibility of a spectrally efficient scheme named orthogonal wavelength division multiplexing with coherent detection (Co-OWDM). Effect of channel spacing on interchannel crosstalk induced power penalty and on decision threshold Q-factor is discussed. Theoretical result shows that the noise increases as we increase the number of channels. Quadrature phase shift keying (QPSK) Co-OWDM system is also analyzed. QPSK based Co-OWDM system increases the throughput and enhances the spectral efficiency. With advantages of higher receiver sensitivity, greater tolerance to transmission impairment, more channel capacity, and secured data transfer, Co-OWDM has the potential to fulfill the future communication needs.