20120715 OCDM · Title: 20120715_OCDM Author: Nishikawa Created Date: 6/21/2012 7:10:36 PM
SAE/OCDM System
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Transcript of SAE/OCDM System
ICEIC Indonesia 2013
SAE/OCDM SYSTEMS USING APD RECEIVER OVER LINEAR DISPERSIVE CHANNEL
Nguyen Tat Thang & Anh T. PhamThe University of Aizu
Computer Communications Lab
Wednesday, April 12, 2023 SAE/OCDM Systems
ICEIC Indonesia 2013
Contents
• Introduction• Optical code-division multiplexing (OCDM) techniques• Dispersion in optical fiber• Motivation
• Theoretical Model and Analysis• Spectral amplitude encoding (SAE) OCDM System• Linear Dispersive Channel• Theoretical BER over Linear Dispersive Channel
• Simulation Model• Results & Discussions• Conclusions
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Overview• SAE/OCDM has been considered as a promising technique for
the next-generation optical access and local networks
• Impact of dispersion is one of critical factors to performance of SAE/OCDM system• This has been analyzed theoretically and experimentally [3][5]
• In this work, we implement a simulation model using OptiSystem® software suite for analyzing the performance of SAE/OCDM systems• We especially focus on modeling and analyzing the impact of dispersion
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• Time Domain Encoding:
• Spectral Amplitude Encoding (Freq. domain):
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OCDM (Optical Code Division Multiplexing)
1 0
t t
Tb
Tc = Tb / NTc01010101
t
f
01010101
01010101
Broadband source
t
f
Tc=Tb
Dispersionphenomena
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3
4
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Impact of Dispersion
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SAE/OCDM Systems
1
0
1
0
0
0
1
• Chromatic dispersion (group velocity dispersion, aka. GVD)• Peak reduction• Pulse Broadening• Time Skewing
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Motivation (1)• Experimental study on the impact of dispersion has been reported
• H. Tamai et al., “Experimental study on time-spread/wavelength-hop optical code division multiplexing with group delay compensating en/decoder,” IEEE Photon. Technol. Lett., 2004.
• It is the experimental study with real implementation• Limitation: expensive, not flexible, delayed, difficult to analyze when
scalability is required
• Theoretical study using the Linear dispersive channel model for analyzing the performance of SAE/OCDM systems• Ngoc T. Dang et al., “Performance Analysis of Spectral Amplitude Encoding
OCDM Systems over a Linear Dispersive Optical Channel”, IEEE/OSA J. Optical Comm. & Netw., 2009.
• Could easily analyze with different configuration, settings• Validation required, some assumption is still far from practical conditions
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Motivation (2)• Understanding the impact of dispersion is critical and needed to be
carefully considered in the system design• Our proposal
• A trade-off solution• Analyze the performance of SAE/OCDM system over dispersive channel
using optical simulation system• Advantages
• Closer to the real implementation• However, it is
• Cheaper• Flexible: Easy to modify system’s parameters, • More quickly faster R&D process• Scalable: easily analyze with a large number of users
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THEORETICAL ANALYSIS
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SAE/OCDM System: Principle
Transmitter - User #1Code C1
Transmitter - User #2Code C2
…
Transmitter - User #KCode CK
Receiver - User #1Code C1
Receiver - User #2Code C2
Receiver - User #KCode CK
…
Combiner K • 1
Splitter1 • K
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Dispersive optical channel
SAE/OCDM SystemsWednesday, April 12, 2023
APD2C1
C1 APD1
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Linear Dispersive Channel Model• The optical pulse propagation model with modified factors
was used for analytical modeling:
*Average received power of chip number i transmitting over L km of fiber
Gaussian pulse peak power
attenuation
*Ps: Transmitted power per bit K: Number of users N: Code length T0: half width of Gaussian Pulse
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System’s BER over Linear Dispersive Channels (APD Receiver)• Received desired signal power (after decoding):
• Received MAI signal power (after decoding):
• BER:
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SAE/OCDM Systems
*Additive branch
*Subtractive branch
*Additive branch
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CONSTRUCTION OF SIMULATION MODEL AND ANALYSIS
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Simulation Model for Transmitter
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Hadamard code – N=12 ω=6 λ=3
Optical Power Combiner
Ps
Other Users
γw
γ0
Ps
101010101010
Fiber Bragg Gratings
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Simulation Model with APD Receiver
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Cm
Cm
Optical Splitter
Optical Power Splitter
Other User:1010101010100101
bit 1
bit 1
bit 0
bit 0
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Results (Theoretical vs. Simulation)• The performances of system with two cases: considering
dispersive channel and non-dispersive (only attenuation) channel.
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SAE/OCDM Systems
* 3 x 500 Mb/s active users in total 8 users, 10 km optical fiber with attenuation 0.2dB/km, D = 16.75 ps/nm/km
BER vs. APD gain,Ps=-17dBm
BER vs. Ps,APD gain = 7
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0.5 dB
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Conclusions & Summary• We have built the computer simulation model for
SAE/OCDM system using APD receiver with 3 activating users in 8 users total
• The well-matched simulation and theoretical results has validated the simulation model. The simulation model therefore could be used for OCDM system R&D
• Next step: we will build the simulations for more complete models, with more practical parameters and more practical devices such as EDFA, dispersion shifted fiber.
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SAE/OCDM SystemsWednesday, April 12, 2023
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Question time
Thank you!
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SAE/OCDM SystemsWednesday, April 12, 2023
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Some of recent experimental model for SAE/OCDM systems
• Julien Penon et al., “Spectral-Amplitude-Coded OCDMA Optimized for a Realistic FBG Frequency Response”, Journal of Lightwave Technology, 2007.
• Mohammad Reza Salehi et al., “Code Performance Comparison in SAC-OCDMA Systems under the Impact of Group Velocity Dispersion”, J. Opt. Commun., 2012
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Simulation of Linear Dispersive Channel
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SAE/OCDM Systems
Without GVD
With GVD
1549 nm 1554 nm
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Transmitter: Principle
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Laser Source
Spectral Encoder
Data (0,1)
channel (OF)
Transmitter
λ1 … λ5 … λ8 λ2 λ4 λ6 λ8
Ps
Ps
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Cm: 0 1 0 0 1 1 1 0 λ1λ2λ3λ4λ5λ6λ7λ8
Hadamard code – N=8 ω=4 λ=2
Hadamard code:• Code length: N – number of chips• Code weight: ω – number of chip 1s• In-phase cross correlation: λ – number
of similar chip 1s of two codes. •
•
SAE/OCDM Systems
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Motivation (2) (Obsoleted)
• Problem• Theoretical model required to be validated• The practical experiments: expensive, not scalable, not flexible and
delayed• Some proposed models have assumption is far from practical
implementation. The dispersive characteristic of OF has not been consider in experiment.
• Advantages• Scalable: large and flexible number of users• Easy to modify system’s parameters• Get the result quickly faster R&D process• Cheaper than the real implementation
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Multiplexing Techniques
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Time t
λ
Wav
elen
gth
Time t
Wav
elen
gth
λ
t
λ
Code
• Codes used for multiplexing
• Asynchronous access ability
• Flexible number of users
• Possibly cheaper
Time division multiplexing(TDM)
Wavelength division multiplexing(WDM)
Code division multiplexing (CDM)
• Time synchronization required
• Limited speed by electronic processing
• Wavelength management required
• Expensive
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Simulation Systems
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Other Users
λ1=1549 λ2=1549.5 λ3=1550 λ4=1550.5
User 1 code: 11110000
λ5, λ6, λ7, λ8,
Cm
Cm
Hadamard code – N=8 ω=4 λ=2
Optical Splitter
Optical Power Splitter
Optical Power Combiner
Gratings
Ps
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SAE/OCDM Receiver
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Coupler (3dB)
Decoder 1
Decoder 2
Threshold Detection
Data (0,1)
PD1
PD2I2
I = I2-I1
I1
channel (OF)
Receiver
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delay
APD1
APD2
Balanced detection
λ2
λ7
λ5
λ6
λ2
λ7
λ6
λ5
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• Received power at receiver #1 (designate for user #1):• Complement code branch - data:
• Direct code branch-data :
• Multiple Access Interfering:
• Balanced Detection:
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Theoretical Calculation
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Spreading Sequence (Code)
• m-sequence (N, (N+1)/2, (N+1)/4), Hadamard (N, N/2, N/4),
MQC (N=p2+p, ω=p+1, λ=1) (p is odd prime number).
• There are several construction of these code sets.
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