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wdm optical interfaces for future fiber radio systems phần 7

Tham khảo tài liệu 'wdm optical interfaces for future fiber radio systems phần 7', kỹ thuật - công nghệ, kĩ thuật viễn thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 4 Characterisation and Enhancement of Links Performance Incorporating WDM Optical Interface FBG2 with reflectivity 54 70 85 and 93 reduces the CSRs of the downlink spectra from 12.2 dB to 9.1 7.1 5 and 1.7 dB respectively. Therefore by replacing the 54 50 reflective FBG in the interface with an FBG of 93 reflectivity a reduction in CSR by as much as 7.4 dB can be achieved. The 3rd column of the Table 4.5 shows the sidebands of the downlink signals vary by 1.3 dB this is due to the presence of fluctuations in the recovered spectra caused by the imperfect filtering characteristics of the FBGs used in the experiment. E -6 co o ra o Q. o -10 1556.3 1556.4 1556.5 Wavelength nm Fig. 4.30 Measured optical spectra of the uplink reuse carriers with various reflectivity of FBG2 recovered at X-Re-Use port of the modified WDM optical interface. The optical spectra of the respective reuse carriers while inserted 54 70 85 and 93 reflective FBG2 in the interface are recovered via X-Re-Use port and shown in Fig. 4.30.The characteristic parameters of these curves are also illustrated in Table 4.5. Fig. 4.30 and Table 4.5 show that the insertion of FBG2 with reflectivity 54 70 85 and 93 provides optical carriers in the uplink path which gradually increases from -7.6 dB to -7.3 -6.7 and -5.8 dB respectively. Therefore the replacement of the 54 50 reflective FBG in the interface with a 93 reflective FBG enables an increase of uplink reuse carrier by as much as 1.8 dB. 165 Chapter 4 Characterisation and Enhancement of Links Performance Incorporating WDM Optical Interface Received Optical Power dBm Fig. 4.31 Measured BER curves as a function of received optical power at DL Drop port of modified WDM optical interface for downlink k2 S2 with FBG2 reflectivity of i 54 ii 70 iii 85 and iv 93 respectively. In compare with the respective downlink carriers at DL Drop port uplink carriers are reduced by approximately 1.2 dB. This can be attributed to the insertion loss of the OC between