光(guang)纖(xian)(xian)傳(chuan)輸(shu)基于可用(yong)光(guang)在兩(liang)種(zhong)介質(zhi)界(jie)面發生全(quan)反(fan)(fan)射(she)(she)的(de)原理。突變(bian)型光(guang)纖(xian)(xian),n1為纖(xian)(xian)芯介質(zhi)的(de)折射(she)(she)率，n2為包(bao)層介質(zhi)的(de)折射(she)(she)率,n1大于n2，進入(ru)纖(xian)(xian)芯的(de)光(guang)到達纖(xian)(xian)芯與包(bao)層交界(jie)面（簡(jian)稱芯-包(bao)界(jie)面）時的(de)入(ru)射(she)(she)角(jiao)大于全(quan)反(fan)(fan)射(she)(she)臨界(jie)角(jiao)c時,就(jiu)能(neng)發生全(quan)反(fan)(fan)射(she)(she)而無光(guang)能(neng)量透出纖(xian)(xian)芯，入(ru)射(she)(she)光(guang)就(jiu)能(neng)在界(jie)面經無數次全(quan)反(fan)(fan)射(she)(she)向前(qian)傳(chuan)輸(shu)。原來(lai)
當光(guang)纖彎(wan)曲(qu)時，界(jie)面法線(xian)轉向(xiang)，入射(she)角(jiao)度小(xiao)，因此(ci)一部(bu)分(fen)光(guang)線(xian)的(de)入射(she)角(jiao)度變得(de)小(xiao)于c而不能(neng)全反(fan)射(she)。但(dan)原來入射(she)角(jiao)較大的(de)那些(xie)光(guang)線(xian)仍(reng)(reng)可全反(fan)射(she)，所以光(guang)纖彎(wan)曲(qu)時光(guang)仍(reng)(reng)能(neng)傳(chuan)輸，但(dan)將(jiang)(jiang)引起能(neng)量損耗(hao)。通常，彎(wan)曲(qu)半(ban)徑(jing)大于50～100毫(hao)米時,其損耗(hao)可忽略不計(ji)。微(wei)小(xiao)的(de)彎(wan)曲(qu)則將(jiang)(jiang)造成嚴(yan)重(zhong)的(de)微(wei)彎(wan)損耗(hao)。
人們常(chang)用(yong)電(dian)磁(ci)(ci)波理論(lun)進一(yi)步研究光(guang)(guang)纖(xian)(xian)(xian)(xian)(xian)傳輸的(de)(de)機制，由光(guang)(guang)纖(xian)(xian)(xian)(xian)(xian)介質波導(dao)的(de)(de)邊界條件來求解波動方(fang)程。在(zai)光(guang)(guang)纖(xian)(xian)(xian)(xian)(xian)中傳播(bo)的(de)(de)光(guang)(guang)包含有許多模式(shi)，每一(yi)個模式(shi)代(dai)表一(yi)種電(dian)磁(ci)(ci)場(chang)分布，并與(yu)幾何光(guang)(guang)學中描述(shu)的(de)(de)某一(yi)光(guang)(guang)線相對應。光(guang)(guang)纖(xian)(xian)(xian)(xian)(xian)中存在(zai)的(de)(de)傳導(dao)模式(shi)取決于光(guang)(guang)纖(xian)(xian)(xian)(xian)(xian)的(de)(de)歸一(yi)化頻率(lv)值式(shi)中NA為數值孔(kong)徑，它與(yu)纖(xian)(xian)(xian)(xian)(xian)芯(xin)和包層介質的(de)(de)折射率(lv)有關。ɑ為纖(xian)(xian)(xian)(xian)(xian)芯(xin)半徑，為傳輸光(guang)(guang)的(de)(de)波長。光(guang)(guang)纖(xian)(xian)(xian)(xian)(xian)彎曲時，發(fa)生模式(shi)耦合，一(yi)部(bu)分能(neng)量由傳導(dao)模轉入輻射模，傳到纖(xian)(xian)(xian)(xian)(xian)芯(xin)外損耗掉。
性能：光纖(xian)的主(zhu)要參數有衰減、帶寬等。
