Digital Signal Processing Reference
In-Depth Information
The important issue in design of WDM light wave systems is the interchannel
crosstalk. The system performance degrades whenever crosstalk leads to transfer
of power from one channel to another, such a transfer can occur because of non-
linear effects in optical fibers. The XPM and SPM both affect the performance of
WDM systems.
8.5 Wavelength Conversion by FWM in SOI Waveguides
8.5.1 Wavelength Conversion Schemes
A high-speed wavelength converter is an essential part within a high capacity all
optical WDM system and thus considerable interest in the development of a prac-
tical wavelength converter exists. All optical wavelength converter satisfies the
high-speed requirement of modern communication systems and can be used for
single channel wavelength conversion and wavelength conversion of a WDM sig-
nal (Figs.
8.4
and
8.5
).
Reports on optical wavelength conversion using various methods already
exist: XPM, super continuum generation and spectral slicing, FWM in a fiber and
interferometric SOA wavelength conversion, just to name a few. An ideal optical
wavelength converter is transparent to both data rate and modulation format. One
method to get such an optical wavelength converter is to use FWM in a nonlinear
waveguide.
Modern high-speed optical systems are likely to use an advanced modulation
formats such as differential phase shift keying (DPSK) and return to zero DPSK
(RZ-DPSK) due to their various advantages compared with conventional on-off
Fig. 8.4
Optoelectronic
regenerator (wavelength
conversion scheme)
λ
1
I(t)
λ
2
Receiver
Transmitter
Fig. 8.5
Regenerative
repeater (optical fiber LAN)
Optical-
electrical
conversion
Amplification
and
regeneration
Electrical-
optical
conversion
Search WWH ::
Custom Search