xviiContents
13.1.5
Ma
ch–Zehnder (MZ) Intensity Modulators Revisited ........................... 527
13.1.5.1
S
ingle-Drive MZIM ...................................................................... 527
13.1.5.2
D
ual-Drive MZIM ........................................................................528
13.2
T
ransmission Loss and Dispersion Revisited ....................................................... 529
13.2.1
N
onlinear Effects ......................................................................................... 529
13.2.2
S
ignal Propagation Model ..........................................................................530
13.2.2.1
N
onlinear Schrodinger Propagation Equation ........................530
13.2.2.2
L
ow-Pass Equivalent Model: Linear Operating Region .........530
13.3
M
odulation Formats ................................................................................................. 531
13.3.1
N
RZ or NRZ–ASK .......................................................................................532
13.3.2
R
Z (or RZ–ASK) ...........................................................................................533
13.3.3
R
eturn-to-Zero Optical Pulses ...................................................................534
13.3.3.1
G
eneration .....................................................................................534
13.3.3.2
P
hasor Representation .................................................................537
13.4
D
ifferential Phase Shift Keying (DPSK) ................................................................541
13.4.1
N
RZ–DPSK ...................................................................................................542
13.4.2
R
Z–DPSK ......................................................................................................542
13.4.3
R
eceiver .........................................................................................................543
13.4.4
S
imulink
®
Models ........................................................................................544
13.4.4.1
B
ernoulli Binary Generator ........................................................544
13.4.4.2
D
FB Laser ......................................................................................546
13.4.4.3
Ma
ch–Zehnder Interferometric Modulator ..............................547
13.4.4.4
P
ulse Carver ..................................................................................547
13.4.4.5
Data Modulator .............................................................................549
13.4.4.6
D
ifferential Data Encoder ...........................................................550
13.4.4.7
B
ack-to-Back Receiver ................................................................552
13.4.4.8
E
ye Diagram ................................................................................553
13.4.4.9
S
ignal Propagation .....................................................................556
13.4.4.10
Bit Error Rate (BER) ....................................................................556
13.5
D
QPSK Modulation Formats Transmission Models ............................................556
13.5.1
D
QPSK Optical System Components .......................................................559
13.5.1.1
D
QPSK Transmitter ....................................................................559
13.5.2
D
QPSK Receiver ...........................................................................................560
13.5.2.1
Mach–Zehnder Delay Interferometer (MZDI) .......................560
13.5.2.2
P
hotodiode ................................................................................... 561
13.5.2.3
N
oise Sources ..............................................................................562
13.5.2.4
D
igital Data Sampling ................................................................562
13.5.2.5
P
ulse Shapes ................................................................................562
13.5.2.6
MATLAB
®
Simulink
®
Simulator ...............................................563
13.6
P
DM-QAM .................................................................................................................565
13.6.1
P
DM-QPSK ...................................................................................................565
13.6.1.1
S
ystem Conguration.................................................................565
13.6.1.2
M
easurement Setup for LOFO ..................................................568
13.6.2
PDM-16 QAM Transmission Systems ....................................................... 574
13.7
M
SK Transmission Model ........................................................................................ 579
13.7.1
I
ntroductory Remarks .................................................................................579
13.7.2
G
eneration of Optical MSK-Modulated Signals ......................................582
13.7.2.1
O
ptical MSK Transmitter Using Two Cascaded EO
Phase Modulators .......................................................................582