空间激光通信技术

yf

<span style="COLOR: #d6181e; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman';"><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span><strong>空间激光通信技术<p></p></strong></span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">概述</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">空间激光通信是指用激光束作为信息载体进行空间？包括大气空间、低轨道、中轨道、同步轨道、星际间、太空间？通信。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">激光空间通信与微波空间通信相比，波长比微波波长明显短，具有高度的相干性和空间定向性，这决定了空间激光通信具有通信容量大、重量轻、功耗和体积小、保密性高、建造和维护经费低等优点。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　１、大通信容量：激光的频率比微波高３－４个数量级（其相应光频率在１０１３－１０１７</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">Ｈｚ）？作为通信的载波有更大的利用频带。光纤通信技术可以移植到空间通信中来，目前光纤通信每束波束光波的数据率可达２０Ｇｂ／ｓ以上，并且可采用波分复用技术使通信容量上升几十倍。因此在通信容量上，光通信比微波通信有巨大的优势。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　２、低功耗：激光的发散角很小，能量高度集中，落在接收机望远镜天线上的功率密度高，发射机的发射功率可降低，功耗相对较低。这对应于能源成本高昂的空间通信来说，是十分适用的。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　３、体积小、重量轻：由于空间激光通信的能量利用率高，使得发射机及其供电系统的重量减轻；由于激光的波长短，在同样的发散角和接收视场角要求下，发射和接收望远镜的口径都可以减小。摆脱了微波系统巨大的碟形天线，重量减轻，体积减小。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　４、高度的保密性？激光具有高度的定向性，发射波束纤细，激光的发散角通常在毫弧度，这使激光通信具有高度的保密性，可有效地提高抗干扰、防窃听的能力。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　５、激光空间通信具有较低的建造经费和维护经费。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">技术难点</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　空间技术的发展和建立全球信息社会的需要，推动着空间光通信技术的进步。空间光通信避开了大气光信道不稳定性的影响，需要解决的关键问题是相对运动光学收、发天线之间的瞄准、接收和跟踪问题等。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　１、空间激光通信链路的快速、精确的捕获、跟踪和瞄准（ＡＴＰ）技术，是保证空间远距离光通信的核心技术。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　（１）、捕获（粗跟踪）系统：激光信标发射的光束很窄，在相距极远的两卫星之间，必须保证信标的发射波束覆盖接收机的接收天线，接收端能够捕捉跟踪发射端的窄光束。由于姿态监测控制系统误差、参照系计算误差、卫星的腾空浮动和振动以及其它系统误差的存在，在收发双方互相对准之后总有一个不确定角。空间捕获目标的范围在</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">±</font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">１</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">°</font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">？</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">±</font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">２０</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">°</font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">或更大，通常采用ＣＣＤ来实现。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">为了缓解对空间瞄准、捕获和跟踪系统苛刻的要求，同时加快通信链路建立速度，接收机的视场角一定要宽，为几个毫弧度，灵敏度为－１１０ｄｂＷ，跟踪精度为几十个毫弧度，可这样接收的背景辐射功率就会迅速上升，掩埋其中的信标信号。解决这一问题的关键在于接收机中使用超窄带宽、高透射率的光学滤波器。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　（２）、跟踪、瞄准（精跟踪）系统：系统完成目标捕获后，对目标进行瞄准和实时跟踪。通常采用四象限红外探测器ＱＤ或Ｑ－ＡＰＤ高灵敏度位置传感器来实现，并配以相应的电子学伺服控制系统，精跟踪要求视场角为几百微弧度，跟踪灵敏度为－９０ｄｂＷ，跟踪精度为几微弧度。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　２、发射机激光器的超高速率调制技术</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　目前各国空间激光通信实验的码率都在１Ｇｂ／ｓ以上，而且不断提高，为了增大通信容量，在一些方案中采用同一波长的两路旋向相反的圆偏振光同时传送，从而使通信容量加倍。在超高速调制的同时又要产生足够的功率用于广阔的空间距离传输，因此除研究大功率半导体激光器以外，国外还在研究采用激光二极管阵列的方案。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　３、高灵敏度抗干扰的接收机技术</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">卫星之间的距离可长达４００００ｋｍ？</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">而激光波束的强度是按距离的平方递减，也就是说衰减可能达到－１５２ｄＢ。接收机要有超高的灵敏度才行，否则背景辐射等噪声会使误码率达到不可接收的程度。目前除提高检测器本身灵敏度外，还在探讨外差接收、纠错编码等途径。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　４、精密、可靠、高增益的收发天线技术</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　为完成系统的双向互逆跟踪，光通信系统采用收发合一天线，隔离度近１００％的精密光机组件（又称万向支架）。由于半导体激光器光束质量一般较差，要求天线增益要高，另外，为适应空间系统，天线（包括主副镜，合束、分束滤光片等光学元件总体结构紧凑、轻巧、稳定可靠。国际上现有系统的天线口径一般为几厘米至２５厘米。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　５、卫星与地面之间的传输</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　空间数据通信网最终还是要与地面连接？</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">若卫星与地面之间不能采用激光通信和卫星之间的高码率匹配？</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">卫星－－地面链路将成为全球通信中的制约环节。在大气传输中激光会受到散射、折射、背景辐射等多种因素的影响，除衰减增强之外，波前畸变、强度抖动、多径、云层遮断等现象均可发生，这些不利因素使通信距离急剧下降，使光信号受到严重的干扰，甚至脱靶。如何保证随机信道条件下系统正常工作是十分重要的。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　目前除选择气候合适的地区之外，还采用光波与毫米波组成联合通信网络，经数据处理与压缩后用微波与地面通信，光波与毫米波信息间的交换是链路的关键问题之一。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　　６、网络控制技术</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">空间激光通信的协议和控制包括从低层的调制激光束的编码和同步、失效链路检测、设计合适的数据链路协议以及到高层的链路建立、信息的包传送、拥塞防护、全球兼容等各种问题。</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">影响</span><span lang="EN-US" style="FONT-SIZE: 9pt; COLOR: black;"><br/><br/></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">　</span><span style="FONT-SIZE: 9pt; COLOR: black;"><font face="Times New Roman">
                                </font></span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;;">卫星激光通信的出现是现代信息社会对大容量、长距离、低成本通信的需求的必然结果，而它的优点也表明了卫星激光通信能够承担此重任。</span></p><p></p></span>