Page 374 - Fiber Optic Communications Fund

Performance Analysis 355

ASE = 1.5 × 6.626 × 10 −34 × 193.54 ×(1000 − 1)
= 1.921 × 10 −16 W/Hz. (8.154)

The PSD of effective shot noise is given by Eq. (7.50),

shot,eff = qI LO
= qRA 2 . (8.155)
LO
From Eq. (8.85), we have
shot,eff
N homo = +
0 ASE 2 2
2R A
LO
q
= + . (8.156)
ASE
2R
Electron charge q = 1.602 × 10 −19 C,
R = 0.9 A/W, (8.157)
1.602 × 10 −19
−16
homo
N = 1.921 × 10 + W/Hz
0
2 × 0.9
= 1.922 × 10 −16 W/Hz, (8.158)
From Eq. (8.122), we have
ASE shot,eff
N het = +
0 2 2
2 2R A
LO
= 9.617 × 10 −17 W/Hz, (8.159)
Error Probability
(a) For a balanced homodyne receiver with PSK signal, the error probability is given by Eq. (8.96),
(√ ) (√ )
1 E av 1 3.16 × 10 −15
PSK
P = erfc = erfc
b homo −16
2 N 2 1.922 × 10
0
−9
= 4.86 × 10 . (8.160)
If the signal is OOK, from Eq. (8.113) we have
(√ )
1 E av
OOK
P = erfc , (8.161)
b 2 2N homo
0
E 1 −15
E = = 1.58 × 10 J, (8.162)
av
2
(√ )
1 1.58 × 10 −15
OOK
P = erfc
b 2 2 × 1.922 × 10 −16
−3
= 2.06 × 10 . (8.163)