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wdm optical interfaces for future fiber radio systems phần 6

Tham khảo tài liệu 'wdm optical interfaces for future fiber radio systems phần 6', 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 Fig. 4.10 shows the transmission and reflection responses for the double-notch FBGs used in the demonstration. The characteristic curves at Fig. 4.10 a show that the nominal Bragg wavelengths for the notches are 1556.207 nm and 1556.509 nm with a separation of 0.302 nm between the notches. The Bragg wavelengths can be Wavelength nm a Fig. 4.10 Measured transmission and reflection spectra for the double-notch FBGs to be used in the experimental characterisation of single and cascaded WDM optical interfaces. tuned to the desired experimental wavelengths by employing suitable mechanical stretchers. The transmission spectrum shows that the notches have leakages of approximately -26 and -27 dB at the Bragg wavelengths from which the reflectivity can be calculated as 99.7 and 99.8 respectively. The characteristic curves at Fig. 135 Chapter 4 Characterisation and Enhancement of Links Performance Incorporating WDM Optical Interface 4.10 b show that the nominal Bragg wavelengths for the notches are 1556.157 nm and 1556.459 nm with a separation of 0.302 nm between the notches. The transmission spectrum shows that the notches have leakages of approximately -22 and -22.5 dB at the Bragg wavelengths from which the reflectivity can be calculated as 99.3 and 99.4 respectively. Also the reflection spectra demonstrate its sharp a Fig. 4.11 Measured transmission and reflection spectra for the 50 reflective FBGs to be used in the experimental characterisation of single and cascaded WDM optical interfaces. b roll-off profiles with minimum side-lobe ripples. The measured insertion losses of the gratings were approximately 0.3 dB each. The characteristic curves for 50 reflective FBGs with nominal Bragg wavelengths of 1556.109 nm and 1556.129 nm are shown in Fig. 4.11. Like before these Bragg wavelengths also can be tuned to the desired experimental wavelengths 136 Chapter 4 .