EECS 285A Final Project
Winter 2023
March 24, 2023
1
Table of contents
Components
3
Network Arcitecture
5
Dispersion Compensation
7
SNR Calculation
8
Nonlinearity Calculation
11
Appendix
12
2
Components
Transceiver
Cisco (C21 - C36) DWDM-SFPG-60.61 Compatible 10G DWDM SFP+ 80km DOM Duplex
LC SMF transceiver Module
https://www.fs.com/products/31238.html
Parameters:
Data rate support: 10Gbps
Transmitted power: 0-4dBm
BER: 1E-12
Receiver Sensitivity: -7dBm to -23dBm
Single Mode Fiber (SMF)
OFS AllWave Optical Fiber - Zero Water Peak
https://fiber-optic-catalog.ofsoptics.com/documents/pdf/AllWave-117-web.pdf
Parameters:
Attenuation: 0.21 dB/km
Typical dispersion slope: 0.087 ps/(nm2.km)
Zero dispersion wavelength: 1302- 1322 nm
Polarization Mode Dispersion @ 1550 nm: 0.1 ps/√km
Effective Area: 65 um2
Dispersion Compensation Fiber (DCF)
Thorlabs Polarization-Maintaining Dispersion-Compensating Optical Fiber
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=12542
Parameters:
Attenuation: 0.40 dB/km
Dispersion slope @ 1550 nm: -0.34 ps/(nm2.km)
Dispersion @ 1550 nm: -100 ps/(nm.km)
Splicing Loss: 1 dB
Effective Area @ 1550 nm: 20 um2
DWDM Mux Demux
FS 16 channels C21-C36, LC/UPC, Dual Fiber DWDM Mux Demux
16CH DWDM Mux Demux w/ Monitor, Expansion & 1310nm Port - FS.com
Parameters:
Allocated wavelengths: C21 - C36
Insertion Loss: 4.2dB Typical (with connectors and adapters)
OADM module
FS Customized dual Fiber DWDM OADM
https://www.fs.com/products/70427.html
Parameters:
Transmission Direction: West and East (16 channel)
Line Type: Dual Fiber
3
Channel Spacing: 100GHz
Channel Passband: ±0.11nm
Insertion Loss (Add/Drop): 4.75dB (16ch)
Insertion Loss (Pass-through): 10dB (16ch)
EDFA Amplifier
FS FMT17BA-EDFA, 17dBm output DWDM EDFA Booster Amplifier, 17dB Gain
https://www.fs.com/products/72283.html?attribute=54781&id=870804
Parameters:
Noise figure: 4.5 dB
Input Power: -23dBm~+12dBm
Saturated Output Power: ≤17dBm
Operation Wavelength: 1527.9nm-1565.6nm
Fiber Connector
FS Customized LSH Boot Size Singlemode Fiber Optic Connector
https://www.fs.com/products/168921.html
Parameters:
Connector insertion loss: 0.2dB
Optical Filter
Thorlabs FBH1550-12 - Premium Bandpass Filter, Ø25mm, CWL = 1550nm, FWHM = 12nm
https://www.thorlabs.com/thorproduct.cfm?partnumber=FBH1550-12
Parameters:
Δλ = 12 nm
Table 1: Approximated total cost
Component
Quantity
Per unit price
(USD)
Component total
price (USD)
Transceiver
64
319
20,416
SMF
450e3
0.28
126,000
DCF
92.1e3
377
34,700,000
DWDM Mux/Demux
4
1109
4,436
OADM
1
1109
1,109
EDFA Amplifier
18
1729
31,122
Fiber connector
48
4.1
Optical filter
18
161.44
197
34,903,285
4
Network Architecture
According to the problem statement, transmitter bit rate is limited to 10Gbps. Hence, each 10 Gbps data will need a
fixed wavelength until it is received. It will take around 26 channels to transmit and receive data. However,
commercial WDMs have channel limits. Hence, channel management can be an optimized alternative. To elaborate,
if one city is communicating on a specific wavelength/ channel with the central city, other two cities can use that
same wavelength to communicate through the central city. This management is visualized in Figure 1 with different
color codes.
However, intercity communication had variable required bandwidths. For example, My city to Her city requires 20
Gbps. On the other hand, Her city to My city requires 40 Gbps. In our proposed network, we allocated 4
wavelengths (40 Gbps) for each city to communicate with each other without and wavelength overlapping. This
takes around 12 channels. When a city needs lower than 40 Gbps, the extra channels will be unused it that case. In
some cases such as His city to Her city and His city to My city, 50 and 70 Gbps is needed. In the design we opted
for 16 channel DWDM Mux/ Demux. Hence, we have 4 unused channels (C12-C16). These channels can be
distributed for the high datarate cases as shown in the black colored fonts in Figure 1.
In order to make the design with commercially available components, we had the option to choose between CWDM
(Coarse Wavelength Division Multiplexing) and DWDM (Dense Wavelength Division Multiplexing). According to
our calculation, CWDM is spreaded in a large wavelength and it will be difficult to compensate dispersion loss.
Hence, we opted for DWDM, which has closely paced wavelengths and available components in fs.com. In Figure
2, we used 4 16 Channel DWDM Mux/Demuc and one 16 Channel OADM to support our network structure.
Details of the insertion losses and other parameters of these parts are added in the components section. Selected
DWDM has a specific wavelengths as channels. A table of those with appropriate commercial notation is shared in
Table 2.
Figure 1: Proposed network diagram.
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Figure 2: Proposed network with commercially available components. The network requires 4 16 Channel DWDM
Mux/Demuc and one 16 Channel OADM
Table 2: 16 Channel (C21-C36) DWDM frequencies and wavelengths
Channel
Frequency
(THz)
Wavelength
(nm)
Channel
Frequency
(THz)
Wavelength
(nm)
C21
192.1
1,560.60
C29
192.9
1,554.13
C22
192.2
1,559.79
C30
193
1,553.32
C23
192.3
1,558.98
C31
193.1
1,552.52
C24
192.4
1,558.17
C32
193.2
1,551.72
C25
192.5
1,557.36
C33
193.3
1,550.91
C26
192.6
1,556.55
C34
193.4
1,550.11
C27
192.7
1,555.74
C35
193.5
1,549.31
C28
192.8
1,554.94
C36
193.6
1,548.51
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Dispersion Compensation
_____________________________________________________________________________________
Dispersion compensation is a must for long haul optical fiber communications. We chose to use Dispersion
compensating fiber (DCF) instead of Dispersion compensating modules (DCM). Dispersion equations of single
mode fiber (SMF) and DCF using available parameters from the available datasheets are given below.
D1(λ) = 0.087λ - 114.14
D2(λ) = -0.34λ - 427
D1 and D2 represents SMF and DCF dispersion with respect to λ, respectively. As our operating wavelength is from
1548 to 1560 nm, we wanted to select fiber combination in a way that dispersion is minimized at the central
wavelength of our system, which is around 1555 nm. D1 and D2 at 1555 nm is 21.145 ps/(nm.Km) and -101.7
ps/(nm.Km), respectively. In order to find optimum locations, we solved these two following equations.
21.145L1 - 101.7L2 = 0
L1 + L2 = Ltot
Here, Ltot is the total length of the fiber. According to our project requirements, Ltot will be 150, 170 and 215 Km
from Your city to Her city, My city, His city respectively. Table 3 shows the required lengths of both fibers to
compensate dispersion. We placed all the DCF fibers to the transmitting ends of His city, Her city and My city.
Table 3: Required lengths of SMF and DCF fibers to compensate dispersion
L1+L2
L1
L2
215
178
37
170
140.7
29.3
150
124.2
25.8
For signal to propagate without dispersion, it has to support dispersion minimization criterion which is |DL|ΔλB ≤ 1
or ¼. For DWDM systems Δλ is 1 nm. Figure 3 depicts the |DL|ΔλB value with DCF and without DCF. With the
compensation, 10 Gbps signal can be transmitted with the DCF. But without DCF, signals will overlap and it will be
undetectable.
Figure 3: |DL|ΔλB value with DCF and without DCF
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SNR Calculation
To calculate the SNR of a link, we considered (1) how the signal power is modified as it propagates to its
destination by attenuation, amplification, and insertion loss, (2) the accumulation of noise power as the signal
propagates to the destination, by beating terms, component noise figures, and detector noises, and (3) minimum
input power to the fiber components, i.e. amplifiers and the detector.
Where 𝐹𝐿 (Flat Loss) is the summation of connector loss, splice loss, and insertion loss of the components along
the link. This equation will require modifications for the first segment and last segment to correctly account. Since
laser noise was negligible, the 𝑃𝑖𝑛 of the first amplifier only had the attenuation due to the fiber on the laser output
2
power. As for the last segment, the addition of the detector introduced σ
𝑠ℎ𝑜𝑡
2
+σ
𝑡ℎ𝑒𝑟𝑚𝑎𝑙
into the noise summation.
Thus, the SNR equation of the final segment is
𝐸𝑆𝑁𝑅 =
𝑃𝑑𝑒𝑡 𝑖𝑛𝑒𝑥𝑝[−α𝐿]−𝐹𝐿
2
σ
2
𝑠𝑖𝑔−𝑠𝑝
+σ
2
Where the terms 𝑃𝑑𝑒𝑡 𝑖𝑛 ; σ
𝑠𝑖𝑔−𝑠𝑝
2
+σ
𝑠𝑝−𝑠𝑝
2
; σ
𝑠𝑝−𝑠𝑝
2
𝑠ℎ𝑜𝑡
+σ
𝑡ℎ𝑒𝑟𝑚𝑎𝑙
; 𝐹𝐿 are an
accumulation of the power losses and gains derived from the link.
When signal is transmitted from Your city to other cities, signals
can be transmitted from Your city with 3 dBm input power or from
an opposite city which has already lost some signal power after
travelling to Your city. Moreover, that signal has additional
amplifier noises from it’s previous path. Therefore, we divided our
probable solution into two steps.
Step 1:
During first step, we will only calculate signals transmitted from
His, Her and My city to Your city. In these cases, transmitted signal
will always be 3 dBm. Flowing figure shows a block diagram of
our calculation steps when only one amplifier is present in the
system. All of our designs are optimized to support amplifier and
receiver sensitivity limitations, which were collected from the
datasheet. Calculated powers and SNRs are illustrated at Figure 5.
Gains and amplifier locations were set in a way to achieve around
-8 to -7 dBm output power. As these signals might need to move to
another city from Your city, we tuned the output to be near the
receiver’s upper threshold.
Figure 4: Flow chart of ESNR and received power
calculation with amplifier and receiver sensitivity
limitations.
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Figure 5: Calculated powers, accumulated noise beating terms, and SNR from Her, His and My city to Your city
while considering possible losses due to attenuation and insertion.
Step 2:
For communication from Your city to other cities, initial input power will not be 3 dBm everytime. According to
our previous calculations, input will be around -8 dBm when the signal has already travelled one intercity distance.
2
This signal will also contain σ
2
, σ
𝑠𝑖𝑔−𝑠𝑝
𝑠𝑝−𝑠𝑝
terms. Hence, the amplifier locations and gains need to be set up in a
way so that low and high input signals both can travel without causing any undetectable situations at amplifiers and
2
receiver. For calculation simplicity, we considered the maximum value of these σ
2
, σ
𝑠𝑖𝑔−𝑠𝑝
𝑠𝑝−𝑠𝑝
noise related
terms during H→Y→S and M→Y→S transmission cases. The calculated received powers and SNRs for Your city
to other cities are showed in Figure 6.
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Figure 6: Calculated powers, accumulated noise beating terms, and SNR from Your city to Her, His and My city
while considering possible losses due to attenuation and insertion.
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Nonlinearity
_____________________________________________________________________________________
Optical Kerr effect is an intensity dependent change in the refractive index of a medium. This effect results in Self
Phase Modulation (SPM) in the wave signal, potentially corrupting the data during decode.
Large phase shift produces chirp, which contributes to spectral broadening, degrading the signal when processing.
To cover longer distances, more amplifiers are required to maintain the signal integrity using amplifiers. However,
This increase in optical power will directly induce SPM via the Kerr effect. Nonlinear phase shift is calculated
using the following equations:
ϕ𝑁𝐿 = γ𝑃𝑖𝑛𝐿𝑒𝑓𝑓
γ=
𝐿𝑒𝑓𝑓 =
2π𝑛2
𝐴𝑒𝑓𝑓λ
1−𝑒𝑥𝑝[−α𝐿]
α
Since the Kerr Effect is mainly produced in the fibers, solving for an entire link would be the summation of all the
phase shifts accumulated in the fibers segments of a particular link. Using (1) the component datasheets, (2) the
calculated 𝑃𝑖𝑛 into each fiber, and (3) the calculated amplifier distances, we can solve for the phase shift in each
direct link. The results are shown in Table 4.
Table 4: Nonlinear phase shift from one city to another
Links
# of Amplifiers
ϕ𝑁𝐿 (degrees)
His to Your
3
13.6648
My to Your
3
9.2828
Her to Your
2
15.129
Your to His
4
73.2387
Your to My
3
22.9314
Your to Her
3
26.3538
To compute the routes that pass through Your City, phase shifts are summed together, e.g. the phase shift from His
City to My City would be:
𝐻 𝑡𝑜 𝑀 = ϕ𝑁𝐿(𝐻 𝑡𝑜 𝑌) + ϕ𝑁𝐿(𝑌 𝑡𝑜 𝑀)
𝐻 𝑡𝑜 𝑀 = 13. 6648 + 22. 9314
𝐻 𝑡𝑜 𝑀 = 36. 5962 𝑑𝑒𝑔𝑟𝑒𝑒𝑠
Thus, all phase shifts through every route in the network are less than 90 degrees, satisfying the limitation.
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Appendix
_____________________________________________________________________________________
All calculations mentioned in this report were determined through MatLab. Link of the scripts of each calculation
are attached here.
1.
2.
3.
4.
5.
6.
7.
8.
Dispersion calculations
Her city to Your city calculations
His city to Your city calculations
My city to Your city calculations
Your city to Her city calculations
Your city to His city calculations
Your city to My city calculations
Project presentation slide
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