tailieunhanh - Frontiers in Guided Wave Optics and Optoelectronics Part 16

Tham khảo tài liệu 'frontiers in guided wave optics and optoelectronics part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Novel Enabling Technologies for Convergence of Optical and Wireless Access Networks 585 wave will occupy over 80-GHz bandwidth because it has two sidebands. Since the two sidebands have different velocities in SMF the RF power at 40 GHz will disappear after transmitting over a certain length of SMF. As an example the eye diagram after transmission over 2 km is inserted in . It is seen that RF power at 40 GHz is almost faded which leads to a large power penalty. The measured BER curves in show the power penalty is 17 dB at a BER of 10-10 after 2km transmission. These results indicate that DSB modulation based scheme is not suitable to a large area access network. A dual-arm M-Z modulator is employed to achieve SSB modulation. The two electrical RF signals to drive the dual-arm M-Z modulator has a phase shift of nil and the DC bias is at . The generated optical mm-wave will only occupy 40-GHz bandwidth but the optical CSR is generally larger than 15 dB which means it is full of DC components at the peak of center wavelength hence it results in low receiver sensitivity. Fig. 9 shows the receiver sensitivity of back-to-back for SSB modulation is around 10 dB lower than that of DSB modulation. Although there is no power penalty after 20-km transmission it is more than 5 dB after 40km transmission due to fiber dispersion and large CSR. When the phase of the two electrical RF signals to drive the dual arm M-Z modulator is set to n difference and the DC bias is at the minimal intensity-output point or Vn OCS modulation is realized. In this scheme only 20-GHz RF signal is needed and the bandwidth for the M-Z modulator is also only 20 GHz moreover the generated optical spectrum just occupies 40-GHz bandwidth. At BER of 10-10 the receiver sensitivity of B-T-B mm-wave signal is dBm which is similar to that of the millimeter signal generation based on DSB modulation. There is no power penalty after transmission over 20 km and the power penalty is less .