Pitfalls in fibre network design Ole Saunte-Boldt Independent Consultant [email protected]...
-
date post
21-Dec-2015 -
Category
Documents
-
view
217 -
download
0
Transcript of Pitfalls in fibre network design Ole Saunte-Boldt Independent Consultant [email protected]...
Pitfalls in fibre network design
Ole Saunte-BoldtIndependent [email protected]
Introductive guide towards a stronger DWDM network design
What is an Optical Network?
Bundling of many channels onto one optical fibre pair
over long distance
Traffic Pipeline
Hierarchy of Optical Networks
DWDM is the foundation of all other servicesA Reliable, Scaleable and Flexible solution is required !
Dark Fiber InfrastructureDark Fiber Infrastructure
Resilient Resilient Packet Packet
Ring (DPT)Ring (DPT)
IP/ IP/ Ethernet Ethernet
SwitchingSwitching
Dense Wavelength Division MultiplexingDense Wavelength Division Multiplexing (DWDM)(DWDM)
Next Gen Metro Next Gen Metro Optical Optical
TransportTransport(SONET/SDH)(SONET/SDH)
SERVICESSERVICESData (IP, FR, ATM, PL) Data (IP, FR, ATM, PL)
Storage (FC, ESCON, iSCSI, outsourcing)Storage (FC, ESCON, iSCSI, outsourcing)Legacy, IP voice. VideoLegacy, IP voice. Video
Grid applicationGrid application
Switching and AggregationSwitching and AggregationL
ease
d L
ines
Lea
sed
Lin
es
The Future ?The Future ?
Factors influencing theReliability, Scalability and Flexibility
Dark Fibre DWDM Equipment
Tech
no
log
y
Attenuation
Chromatic Dispersion
Polarisation Mode Dispersion
Type of fibre
Age of fibre installation
(Distance between POP’s)
Data rate
Filter size
Amplification bands
Transmission range
Forward Error Correction
Dispersion Compensation
Laser Tuneability
Filter Tuneability
Management System
(DWDM Road Map)
Services
Service Level Agreement
Managed Network Services
First Level Services
Next Business Day Service
Next Day Service
24x7 Service
Second Level Services
Third Level Service
Managed Spared part service
Pre-Design Considerations
Make a visionary decision with no regards to cost (initially)
Know you current network requirementsBest guess on future requirements
Consider router consolidation and other high bandwidth university applicationsDWDM investments are for 15-20 years !
Select Scalability through the 1-10-100 rule1: DWDM solutions supports current requirement, BOL10: DWDM system scales to 10 times the BOL capacity without extra basic investments100: The installed network can support 100 times the BOL traffic with extra investment.
Select Reliability through a Pure Optical NetworkAvoid O-E-O regeneration
Select Flexibility through a Tuneable Optical Network
Select the correct platform!CWDM – p2p city platform with limited capacityMetro DWDM – p2p/ring city platform with high capacityLong Haul DWDM – Intercity platform with high capacity
Fibre Pitfall #1: Attenuation
Fibre attenuation is basically defined by the fibre impuritiesA = 0,20 dB/km @ 1550nm
Excess losses that adds to the all over fibre attenuation are Bend loss, splicing and connector losses0,05 dB/km excess loss is not rare !
Losses at 0,20 dB/km signifies a newly installed fibre with limited excess loss
Losses at 0,25dB/km signifies an older installation with excess losses
Fibre Pitfall #2: Chromatic DispersionThere are mainly three fibre groups on the marked:
1. Non–dispersion-shifted fibre (NDSF), standard single-mode fibre (SMF)- zero dispersion point around 1550 nm
2. Dispersion-shifted fibre (DSF)- zero dispersion point around 1550 nm
3. Non–zero dispersion-shifted fibre (NZ-DSF)- zero point around other λ
FWM limits the channel capacity of a DWDM system. FWM cannot be filtered out FWM is significant for DSF (2) which is unsuitable for WDM applications.
Fibre Pitfall #3: PMD
PMD: Polarisation Mode Dispersion
Stochastic variation of the fibre dispersion with
time, temperature and pressure.
The new fibre types have less than 0,5 ps/km
10Gb/s signals tolerate 10ps of PMD which permits 400km fibre40Gb/s signals tolerate 2.5ps of PMD which permits 25 km fibre
Fibre Pitfall #4: SLA of fibre
Standard text in a Service Level Agreement for dark fibrecontains options for fibre replacement if the values exceed
0,25 dB/km attenuation and 0,5 ps/km of PMD
This could be very damaging to the quality of the networkadding high extra costs to the
DWDM system
Equipment Pitfall #1: Amplification bands
Ensure scalability to minimum the C and L bands
Understand the excess cost of scaling the amplifiers
Equipment Pitfall #2: Filters !
Smaller filters equal higher channel number but reduced data rate
Smaller filters puts constraint on the system tolerance
A good balance is achieved by using the 50 GHz filters
Equipment Pitfall #3: Span limitation of DWDM networks
sectionspan
Rule of thumb: Distance of spans are dependant on the number of spans in a section e.g.
1 span in the section: maximum loss in span is 40 dB (~182 km/span)3 spans in the section: maximum loss in span is 34 dB (~155 km/span)25 spans in the section: maximum loss in a span is 19 dB (~86 km/span)
Ensure that the SLA supports the BOL DWDM design !
Equipment Pitfall #4: Dispersive effects
Standard SMF fiber has 17 ps/nm/km of chromatic dispersion10-Gb/s receivers can tolerate about 800 ps/nm of dispersion
500-km systems generates 8500 ps/nm of dispersion
2.5Gb/s transmission is 16 times less sensitive than 10 Gb/s2.5Gb/s signals tolerate up to 12,200 ps/nm
40Gb/s transmission is 16 times more sensitive than 10 Gb/s40Gb/s signals tolerate up to 50 ps/nm
Equipment Pitfall #4: Channel Growth ModelCost pr channel upgrade
DWDM solutions are known to incorporate a build-as-you-grow strategy hiding costs related to upgrades of channels over time.The graph is an attempt to uncover hidden cost elements and major cost jumps as the system grow over time.
0
500.000
1.000.000
1.500.000
2.000.000
2.500.000
3.000.000
3.500.000
4.000.000
4.500.000
5.000.000
λ6 λ9 λ12
λ15
λ18
λ21
λ24
λ27
λ30
λ33
λ36
λ39
λ42
λ45
λ48
λ51
λ54
λ57
λ60
λ63
Channel number
Acc
umul
ated
Cos
t [U
S$]
0
1
2
3
4
5
6
7
8
9
ME
UR
CAPEX OPEX year 1 OPEX year 5 OPEX year 10 OPEX year 15
Cost Parameter
Fibre
Equipment
Service
Services Pitfall: The high OPEX
The NBD (next business day) service below will increase significantly if a more strict response policy is required.
Build a strong protection into the DWDM platform and avoid high service costs !
AMBITION: Build a DWDM network for the Future
FLEXIBILITY: Build a state of the art reconfigurable network
SCALABILITY: Scalable to minimum 64 channels in the C-band
RELIABILITY: Absolute min. of regeneration
ENABLED: 40 Gbit/s ready
Statements