- OPTIMIZING PARAMETERS TO ENHANCE OPTIC SIGNAL-TO-NOISE RATIO IN NATION-WIDE TERRESTRIAL DWDM CASCADED EDFAs FIBER. - Optimized results show that the OSNR at the end of transmission line can be increased by (2-5)dB in average comparing with that in cases where parameters are chosen by experience way.. - In Nation-wide terrestrial DWDM- cascaded EDFAs Fiber Optic Communication Systems, values of signal power launched fiber and EDFAs gain influence directly and considerably on OSNR at the end of transmission line. - This means that system can not be set up their optimized values to achieve a high OSNR at the end of transmission line.. - In this paper, we proposed calculating models of Nation-wide Terrestrial DWDM cascaded EDFAs FOCS where the losses due to OADM, GEQ, Connectors were considered. - ASE noise power and for optimizing OSNR at the end of line were built. - Typical calculating models of Nation- wide Terrestrial FOCS using DWDM and in- line EDFAs chains are given as in Fig.1.and Fig.2. - For example, N=M-1 in fig.1 and N=M in fig.2.. - ATT 1, ATT 2 , ..ATT M-1 losses due to OADM, Gain Equalizer (GEQ), Connectors…. - General Model of Nation-wide Terrestrial DWDM Cascaded EDFAs System using one-stage amplifier configuration. - General model of Nation-wide Terrestrial DWDM Cascaded EDFAs System using one and two-stage amplifier configurations. - Optical Signal-to-Noise Ratio (OSNR) at the end of transmission line. - As a result, OSNR at the end of line for m th channel (f m ) is shown as:. - Signal power at the end of line. - ch in N. - FWM noise at the end of line. - The expression of FWM noise power[1. - at the end of transmission line is extended by taking into account of ATT including losses of OADM, GEQ, Connectors, and is shown as (in c.g.s, units).. - Accumulated ASE noise at the end of transmission line. - EDFA-ATT. - EDFA-ATT-EDFA. - Main algorithm chart for optimizing OSNR at the end of Line. - Writing expressions for calculating: signal power P sig , accumulated ASE noise power P ASEtot , FWM noise power. - P FWMtot and OSNR of m th channel at the receiver’s input.. - N P in/ch :=-12. - P in/ch :=P in/ch 0 +1. - Algorithm chart for calculating FWM noise power P FWMtot (f m. - Algorithm chart for calculating Accumulated ASE noise power P ASEtot (f m. - P in/ch. - In order to illustrate the optimizing parameters in one concrete Nation-wide system where every span length between EDFAs is different, Vietnam Nation-wide DWDM Optical Communication System is chosen as a typical one. - Making algorithm and calculating optimal parameters, thus, can be carried out independently in five segments for achieving maximum of OSNR at the end of them. - We consider Vinh-Danang transmission line as one of the typical segments for applying algorithm charts mentioned in section 3. - P in (K) =P in/ch and. - P in/ch : (-12dBm ÷ 0dBm). - First, 16-channel transmission line is examined. - Algorithm charts in fig.5, and fig.6 basing on expressions are used for calculating FWM (P FWMtot ) and ASE (P ASEtot ) noise powers, respectively.. - Pfwm&Pase noise power[dBm. - Pfwm - Pin/ch=0dBm Pfwm - Pin/ch=-2dBm Pfwm - Pin/ch=-4dBm Pfwm - Pin/ch=-6dBm Pfwm - Pin/ch=-8dBm Pfwm - Pin/ch=-10dBm Pase. - P FWMtot and P ASEtot [dBm] versus wavelength for different values of P in/ch in. - 16-channel Transmission Line.. - Results in fig.8 and fig.9 show that P FWMtot and P ASEtot noise powers at the end of segment change versus wavelength for different values of P in/ch. - Fig.10 presents variation of OSNR versus wavelength for different P in/ch. - The optimized results are found as follows, P in/ch =-4dBm, G 1 =12, G 2 =29, G 3 =13, G 4 =11, G 5 =26, G 6 =21, G 7 =28dB. - Fig.11. - shows Gain of EDFAs in cases of optimized and not-optimized parameters in Vinh-Danang Transmission Line.. - In fig.12, OSNR values are shown as a function of wavelength with different values of PinFibertot. - When G 1 increases from 12dB to 15dBm, corresponding to rising of PinFibertot from 16dBm to 19dBm, OSNR at the end of line decreases because both P ASEtot. - Pin/ch=-1 Pin/ch=-8 Pin/ch=-6 Pin/ch=-4 0dBm Pase dBm Pin/ch=-2 dBm Pin/ch=0d dBm dBm Bm . - Pfwm &Pase noise power. - P FWMtot , P ASEtot versus wavelength for different values of P in/ch in 16-channel Line. - Optimized parameters Pin/ch=0dBm. - Pin/ch=-2dBm Pin/ch=-4dBm. - Pin/ch=-6dBm Pin/ch=-8dBm. - Fig.10. - OSNR [dB] versus wavelength for different P in/ch in 16-channel Line. - OSNR [dB] versus wavelength for different PinFibertots in 16-channel Line. - Results are presented in fig.13 and fig.14, respectively. - They are determined as follows P in/ch. - In this paper, typical calculating models of Nation-wide Terrestrial DWDM cascaded EDFAs FOCS were considered as extension of model proposed in [1] by taking into account of ATT including losses of OADM, GEQ, Connectors. - Fig.13. - OSNR [dB] versus wavelength for different P in/ch in 24-channel Line. - Optimized parameters Pin/ch=0dBm Pin/ch=-2dBm Pin/ch=-4dBm Pin/ch=-6dBm Pin/ch=-8dBm. - Fig.14. - OSNR [dB] versus wavelength for different P in/ch in 32-channel Line