光(guang)(guang)(guang)纖(xian)傳輸基于(yu)可用光(guang)(guang)(guang)在兩種(zhong)介(jie)質界面(mian)發(fa)生(sheng)全反(fan)射(she)的原理。突變(bian)型光(guang)(guang)(guang)纖(xian),n1為纖(xian)芯(xin)介(jie)質的折射(she)率，n2為包層介(jie)質的折射(she)率,n1大于(yu)n2，進入纖(xian)芯(xin)的光(guang)(guang)(guang)到達纖(xian)芯(xin)與包層交界面(mian)（簡稱芯(xin)-包界面(mian)）時(shi)的入射(she)角大于(yu)全反(fan)射(she)臨(lin)界角c時(shi),就能發(fa)生(sheng)全反(fan)射(she)而(er)無光(guang)(guang)(guang)能量透出纖(xian)芯(xin)，入射(she)光(guang)(guang)(guang)就能在界面(mian)經無數次(ci)全反(fan)射(she)向前傳輸。原來
當光纖彎(wan)(wan)(wan)曲時，界面(mian)法線轉向，入(ru)射角(jiao)度小，因此一部(bu)分光線的入(ru)射角(jiao)度變得小于c而不(bu)能(neng)全(quan)反(fan)射。但(dan)原來入(ru)射角(jiao)較大的那些光線仍可(ke)全(quan)反(fan)射，所以光纖彎(wan)(wan)(wan)曲時光仍能(neng)傳輸，但(dan)將引起能(neng)量損耗(hao)。通常，彎(wan)(wan)(wan)曲半徑大于50～100毫米時,其(qi)損耗(hao)可(ke)忽(hu)略不(bu)計。微小的彎(wan)(wan)(wan)曲則將造成(cheng)嚴重的微彎(wan)(wan)(wan)損耗(hao)。
人們常用電磁(ci)波理論進一(yi)(yi)(yi)步研究光(guang)纖(xian)(xian)(xian)傳(chuan)(chuan)(chuan)輸的(de)(de)機制，由光(guang)纖(xian)(xian)(xian)介(jie)質波導的(de)(de)邊界條件來求解波動方程。在光(guang)纖(xian)(xian)(xian)中傳(chuan)(chuan)(chuan)播的(de)(de)光(guang)包(bao)含(han)有許多模(mo)式，每一(yi)(yi)(yi)個模(mo)式代表一(yi)(yi)(yi)種電磁(ci)場分布，并(bing)與幾何光(guang)學(xue)中描述(shu)的(de)(de)某一(yi)(yi)(yi)光(guang)線相對應(ying)。光(guang)纖(xian)(xian)(xian)中存(cun)在的(de)(de)傳(chuan)(chuan)(chuan)導模(mo)式取決于光(guang)纖(xian)(xian)(xian)的(de)(de)歸(gui)一(yi)(yi)(yi)化頻率值式中NA為(wei)(wei)數值孔徑，它與纖(xian)(xian)(xian)芯和包(bao)層介(jie)質的(de)(de)折射(she)率有關。ɑ為(wei)(wei)纖(xian)(xian)(xian)芯半徑，為(wei)(wei)傳(chuan)(chuan)(chuan)輸光(guang)的(de)(de)波長。光(guang)纖(xian)(xian)(xian)彎曲時，發生(sheng)模(mo)式耦(ou)合，一(yi)(yi)(yi)部分能量由傳(chuan)(chuan)(chuan)導模(mo)轉入輻射(she)模(mo)，傳(chuan)(chuan)(chuan)到纖(xian)(xian)(xian)芯外損耗掉。
性能：光纖的(de)主要參數有(you)衰減、帶寬等。
