Tham khảo tài liệu 'advances in lasers and electro optics part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Optical DQPSK Modulation Performance Evaluation 435 t s E DP n bo _o EDP ỢJ c AT Ts 40 a Ideal RX 1 g u b Af BR 2 1 0 - - 1 - - 2 - 3 - 4 - 5 - . EDP ỢJ 0 0 1 T EDP n bp bp 3 -4 1 0 - - 1 - 2 - 5 .__ _ EDP Ợx d R1 A W R2 1 A W e 0Tmzdi Ts 20 f Au 20 GHz Fig. 6. Eye-diagram of electrical current and corresponding PDF of the EDP in presence of several different RX imperfections. Marks MC simulation lines GA estimated from the results of MC simulation. with nominal means of 3n 4 is performed by the GA. Fig. 6 d illustrates the amplitudeimbalance of detector. This RX imperfection leads to quite asymmetric eye-diagrams and to some inaccuracy in the GA for the PDF of the EDP. However the EDP at the area of interest is still approximately Gaussian-distributed. The illustration of delay errors of MZDI is shown in Fig. 6 e . This RX imperfection leads to some distortion of the eye-diagram. Nevertheless the EDP is still approximately Gaussian-distributed. The illustration of the optical filter detuning is shown in Fig. 6 f . The optical filter detuning leads to considerable degradation of the eye-diagram. The EDP at the area of interest is still approximately Gaussian-distributed. However the GA tends to slight underestimate the PDF of the EDP. 436 Advances in Lasers and Electro Optics Another RX imperfection is the finite extinction ratio of the MZDIs. This imperfection affects only the DQPSK system performance when combined with amplitude-imbalanced detectors Bosco Poggiolini 2006 . In such case the performance degradation is mainly imposed by the amplitude-imbalance unless much reduced extinction ratios are considered. Thus both the eye-diagram and PDF of the EDP in presence of finite extinction ratios of the MZDIs are usually similar to those shown in Fig. 6 d . Fig. 7 .
