Collisional broadening of some 2~1Δ_g←B^1Π_u lines in Na_2 molecules by optical-optical double resonance spectroscopy

Using the optical-optical double resonance （OODR） technique, we have studied the collisional broadening of some 21△g←B1πu lines in Na2 molecules. A single line Ar＋ laser is used to pump the sodium dimers from thermally populated ground state X^1∑^＋g level to the intermediate B1πu state. Then, a single-mode diode laser is used to probe the doubly excited 21△g state. The broadening rate coefficient is determined from the slope of the total linewidth versus Ne density curve. We obtain the average value kbr = （1.1 ± 0.5）×10^-8 cm^3 8^-1. The collisional excitation transfer between rotational levels of the B1πu state （i.e.,B1πu（2,83/84） ←B1Ⅱu （2,82）） is also investigated. The rates can be determined from the relative intensities of the main peak and satellite lines, combined with a rate equation model. The rates of 1.25 × 106 and 1.07 × 106 s^-1 are obtained, respectively.

光纤通信窃听及其检测技术探讨

由于光纤通信的容量越来越大,并且许多业务流量涉及敏感和机密信息,这必然吸引一些攻击者进行窃听、假冒甚至实施中断服务攻击;又由于信道故障和严重的信号损耗导致的业务中断都将引起网络拥塞和大量业务流量的丢失。因此,建立快速检测和恢复策略,实现对网络态势的实时监控,并对恶意入侵和光学参数的内在衰减事件进行快速响应,对未来光纤网络的正常运行将起到十分重要的作用。文中主要对光纤窃听方法、光纤窃听检测技术、防范光纤窃听的新技术等进行了介绍和分析。