WDM

WDM : /

, : ( ) ( )

/

: (SMF): (MMF): .

c (c): > c

2 2 2 1/ 2 c = (n1 n2 ) V c

:

n1,n2: , V= 2.405 step-index

(step-index) (a) (graded-index) (b) - (matched-cladding) ( c ) (depressed-cladding) (d), (e) 1.3m

- (dispersion-shifted fibers) (f),(g),(h) 1550 nm

(multicladding dispersion-flatted) (I),(j)

(CCITT)

E

20dB 20 0.2 dB 0.85 m 1.3 m 1.55 m

- - SiO2

(Rayleigh ) R=CR(1/4) dB/Km CR: / Rayleigh

CR =f(n1-n2, 2, . ) ( ) n1-n2 R crit = sin-1(n2/n1)

1> crit vz = (c/n1)sin 1 . graded-index : 1 n 1 n

=( /d 2) (n12- n22)=()2 =(n12- n22) (numerical aperture)

(Dispersion) - (Modal dispersion )

( ) ()

(Chromatic dispersion )

(Polarization - mode dispersion )

- Dmaterial , . .2 1 ( n1 ) D material c 2

Dwaveguide (. ).n = 1g ( z ) D waveguide c 1

(Chromatic dispersion) (D) ps/(nmKm) : ps 1nm 1Km L 1.31m D0 : DFB laser

DintraD intra =D material +D waveguide

Dmodal=g,max-g,min : Dmodal= (n1g)/c =(n1-n2)/n1

:

Dmodal= (n1g2)/(8c)

D2total= D2intra2 +D2modal nm

L Dtotal L fiber=1/(Dtotal L)

~ L Dmodal L>Lc Dtotal ~L ( L>Lc )

0 ( ) >0 0 1 BER =-0 BER :

= = D L 0 = 1 total 0 4 4B

2 = 2t + 2r + ( D L )2 ( 1 )2 total 4B

t , r

Dtotal bit rate - 1: bit rate, 2: bit rate, SMF 3: bit rate, DSF

Dtotal bit rate - 1: bit rate : Lmax 1/ 2 1 Bmax = L < Lmax = 1 1 1 1/ 2 4Dmax B2 B 2 2 2 max 4 t + r 2: bit rate

L

1 c 4k 2 Dint ra b

1 1 1 B B2 B 2 max

1/ 2

kb = 2

: = DPMD L 1dB = DPMD L < 0.1 : it rate DPMD (/ )

- : Brillouin (SBS) Raman (SRS) (Four-Wave mixing, FWM) - (Self-phase modulation, SPM) - (Cross-phase modulation, CPM) :

- e (b) Ae

: : , z:, L: Le:

L l Km M Le : , l

PLe : l Le, P (b) PLe (a)

: () ( ) () : Stokes : ( ) : g :

Brillouin (SBS) -

Stokesh f h (f - f )

hf

(Stokes) f

f = f f = f f

c

f 11GHz

: 1