基于偏振调制的最优接收灵敏度的ROF链路研究（英文）

Study on a radio over fibre link with improved receiver sensitivity based on polarization modulation

提出了一个基于偏振调制的最佳接收灵敏度ROF链路系统。其根本原理在于实现具有最佳光载波边带比(OCSR)的光单边带调制技术,为此,利用偏振调制和滤波技术,线偏光首先经由一个特定偏振角α进入偏振调制器,然后一个固定起偏角β的起偏器被用来合并偏振信息,最后利用一个光滤波器实现光双边带调制到光单边带调制的转换。研究发现所获得的OCSR只与两个偏振角(α和β)有关,通过仔细调节上述指标,可以将OCSR调谐至最佳值0 d B。利用仿真验证了上述结论,仿真发现通过将OCSR调谐至最佳值将大大提高ROF链路的接收灵敏度。

In this work, a radio over fibre link with improved receiver sensitivity was reported. The basical mechanism of this prototype was to realize optical single sideband modulation with an optimum optical carrier-to-sideband ratio （OCSR）. To do this, both polarization modulation and optical interleaving technology were employed. The linearly polarized incident light was firstly oriented at an angle of （α≠0°or 90°） relative to one principal axis of the polarization modulator （PolM）, which is biased by Vπ and driven by RF signals. Then a polarizer with its polarization direction β（β≠0°or 90°） relative to one principal axis of the PolM was used to linearize the polarization state. Finally, optical double sideband signal was converted to optical single sideband signal by using a standard optical interleaver. It is found the OCSR is only dependent on the values of two polarization angle, α and β. With careful adjustment, the OCSR can be reduced to 0 dB, which is the optimum value for a single RF tone modulation. The receiver sensitivity of the fibre link is analyzed by theory and then verified by simulation. It can be greatly improved by using this technique.