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Optical Network Curriculum
Development Section
Optical Network Curriculum
Development Section
ISSUEISSUE
WDM Network TechnologyWDM Network Technology
1.01.0
ObjectivesObjectives
Understand the basic concept of WDM
network ,
Grasp the budgeting method in WDM
network design ,
Know channel coding technology in WDM
network ,
On completion of this course ,you will be able to :
ContentsContents
Chapter 1 WDM network description
Chapter 2 Factors to be considered in
WDM networking budget
Chapter 3 Coding Technology
Chapter 1 WDM network descriptionChapter 1 WDM network description
1.1 WDM NE Types
1.2 WDM Network Topology1.2 WDM Network Topology
OTM
OTM
1.OTM
OADM2.OADM
3.OLA
4.REG
REG
REG
WDM NE TypesWDM NE Types
OTMOTM
OTU DeMUX
OTUMUX
Optical Amplifier
Optical Amplifier
OSC
OLAOLA
Optical amplifier
OSC
Optical amplifier
OADMOADM
OTU
OADM
OSC
OA
OA
TMUX
OA
OA
REGREG
DeMUXMUX
Optical amplifier
OSC
OTU
DeMUX MUXOptical amplifier
OTU
Chapter 1 WDM network descriptionChapter 1 WDM network description
1.1 WDM NE Types1.1 WDM NE Types
1.2 WDM network topology
Point to Point NetworkPoint to Point Network
SDHOTM OLA OLA OTM SDH
It consists of OTM and OLA ,and OADM is
not included .
Chain networkChain network
STM-1616个
OTM
STM-1616个
STM-168个
OTM OADM
Ring NetworkRing Network
OADM
OADM OADM
OADM
Note: OADM is including static OADM and back-to-back OTM (OTM-OTM)
Chapter 1 WDM network descriptionChapter 1 WDM network description
1.1 WDM NE Types1.1 WDM NE Types
1.2 WDM network Topology1.2 WDM network Topology
ContentsContents
Chapter 1 WDM network description
Chapter 2 Factors to be considered in
WDM networking budget
Chapter 3 Coding Technology
Chapter 2 Factors to be considered in WDM networking budget
Chapter 2 Factors to be considered in WDM networking budget
2.1 Attenuation
2.2 Dispersion
2.3 OSNR
2.4 Nonlinearity
AttenuationAttenuationAttenuationAttenuation
Under worst condition :L=(Ps-Pr)/a
Ps :Launched optical power (with single channel) at transmitter side Pr :Receiving optical power (with single channel) at receiver side .a :Attenuation coefficient . it is recommended as 0.275dB/km (for G.652) from ITU-T when taking optical splicing and redundancy into consideration ,
A BS R
LPs Pr
AttenuationAttenuationAttenuationAttenuation
Example :
Ps=5dBm, Pr= -17dBm, L=
Ps=5dBm, Pr= -28dBm, L=
80km
120km
Chapter 2 Factors to be considered in WDM networking budget
Chapter 2 Factors to be considered in WDM networking budget
2.1 Attenuation
2.2 Dispersion
2.3 OSNR
2.4 Nonlinearity
DispersionDispersion
Dispersion limited distance=
(Dispersion tolerance/dispersion coefficient)- (10~ 30)
(Normally , Redundancy is considered as 10~30 km
)
Dispersion tolerance : it depends on the spectrum perfo
rmance of light source .
Dispersion performance with STM-16 level Dispersion performance with STM-16 level
Dispersion tolerance of light source is 7200ps/nm ,
12800ps/nm etc,.
Dispersion coefficient is about 17ps/nm.km in G.652
fiber (20ps/nm is used in project when redundancy is
considered),
Typically ,dispersion coefficient is about 1~6ps/nm.km
in G.655 fiber .
Dispersion performance with STM-64 level Dispersion performance with STM-64 level
Dispersion tolerance of light source is 700ps/nm , 1200p
s/nm etc,.
Dispersion coefficient is the same as above .
Max. transmission distance without compensation :
In G.652 L=700/17-(10~ 30)
In G.655 L=700/6-(10~ 30)
10G10GLA LABA PA
100km100km 100km
DCF:60km DCF:80km DCF:80km DCF:60km
Distributing compensation is recommended to obtain good effect .Distributing compensation is recommended to obtain good effect .
Dispersion compensationDispersion compensationDispersion compensationDispersion compensation
It is necessary to make dispersion compensation in STM-64 system .
Chapter 2 Factors to be considered in WDM networking budget
Chapter 2 Factors to be considered in WDM networking budget
2.1 Attenuation
2.2 Dispersion
2.3 OSNR
2.4 Nonlinearity
NoiseNoise (( ASEASE))
Signal Signal
ASE NoiseASE Noise
OSNR
Span
OSNR is used to measure accumulation degree of ASE noise .defined as :
The ratio of signal power to the noise power inside a specific band nearby signal:
OSNROSNR
ASE
sP
POSNR
Adopt Optical Amplifiers with low noi
se :
•Application of Preamplifiers with low no
ise
•Raman technology
How To Reduce Noise AccumulationHow To Reduce Noise Accumulation
System Design With Raman AmplifiersSystem Design With Raman AmplifiersSystem Design With Raman AmplifiersSystem Design With Raman Amplifiers
Chapter 2 Factors to be considered in WDM networking budget
Chapter 2 Factors to be considered in WDM networking budget
2.1 Attenuation
2.2 Dispersion
2.3 OSNR
2.4 Nonlinearity
Nonlinearity LimitationNonlinearity Limitation
Nonlinearity Limitation :
Limit optical power of single channel
Limit optical power coupled into fiber
Refer to G.663
Take FWM into account ,channel spacing is
strictly required in G.653 .
Refer to G.692
Nonlinearity :
SBS, SRS, FWM, SPM, XPM etc,.
ContentsContents
Chapter 1 WDM network description
Chapter 2 Factors to be considered in
WDM networking budget
Chapter 3 Coding Technology
How to increase OSNR tolerance in WDM system?How to increase OSNR tolerance in WDM system?
Adopt Forward Error Correction Technology: FE
C/EFEC
Adopt special coding technology : RZ format etc,.
Chapter 3 Coding TechnologyChapter 3 Coding Technology
Chapter 3 Coding TechnologyChapter 3 Coding Technology
3.1 FEC coding
3.2 RZ coding3.2 RZ coding
FEC TechnologyFEC Technology
FEC( Forward Error correction) At transmitter end, some additional overheads bits or by
tes are inserted into the transmitting data, at receiver en
d, wrong data (error) will be corrected through addition
al bits or bytes.
With FEC function, It can improve BER performance wit
hout increasing OSNR requirement.
FEC TechnologyFEC Technology
•Digital encapsulation
•RS Coding ( 255 , 239 )
FEC is used to correct code, it doesn’t increase optical power or improve OSNR, but data error ratio is reduced under the same condition. In case of BER<10-12
Without FEC :OSNR is required to be more than 20dB
With FEC, OSNR is required to be more than 16dB
In practical application, when FEC function is available, it means long distance transmission with multiple sections can be achieved.
OSNR and FECOSNR and FEC
Chapter 3 Coding TechnologyChapter 3 Coding Technology
3.1 FEC coding
3.2 RZ coding3.2 RZ coding
R ZR Z
RZ - Return to Zero Code
NRZ
RZ
1 1 11 11 1 00
CLOCK
T
T
T
RZ CodingRZ Coding
I1-I0
I1-I0
• Small duty cycle and power density;
• Higher ability to resist dispersion and nonlinearity,
• Higher ability to resist eye pattern degradation resulted by PMD.
Super WDMSuper WDM