coherent optical code division multiple access (ocdma) systems pedro bertarini

Coherent Optical Code Division Multiple Access (OCDMA)

Systems

Pedro Luiz Lima Bertarini

University of São PauloEngineering School of São Carlos

Department of Electrical Engineering

International Workshop on Trends in Future Communications:High Performance Network Infrastructure for Future Internet23-25 February 2014, CPqD Auditorium, Campinas, SP- Brazil



São Carlos~ 150 km to Campinas~ 240 km to São Paulo

Telecomunications GroupSupervisor: Prof. Ph.D. Ben-Hur Viana Borges



POSTDOCTORAL RESEARCHER: PH.D. PEDRO LUIZ LIMA BERTARINI

PH.D. CANDIDATES: ANDERSON L. SANCHESDANIEL B. MAZULQUIMLEONE M. VEIGA JOSÉ V. REIS JR. THIAGO R. RADDO THIAGO VASCONCELOS (UFPE)

MS.C. CANDIDATES: ACHILES F. MOTADANIEL MARCHESIHEINZ SUADICANILARISSA LIMA

COLLABORATORS: PH.D. FREDERICO D. NUNES (UFPE)COLLABORATORS: PH.D. LUIZ G. NETO (SEL/USP)

On-going Research Projects

› Metamaterials

› Chiral Metamaterials

› Cavity sensors

› Plasmonic lenses

› SOI/SPP based devices

› Supercontinuum generation

› Optical Code Division Multiple Access (OCDMA)

P. L. L. BERTARINI - Coherent Optical Code Division Multiple Access (OCDMA) Systems 4

Different Applications:

Antennas

Biosensors

Outline

OCDMA encoding technologies

SPECTS-OCDMA systems

Optimal code-set selection

Concluding remarks

P. L. L. BERTARINI - Coherent Optical Code Division Multiple Access (OCDMA) Systems 5


Multiple access technologies

WDMA TDMA CDMAf

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1

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t

B

f

B ...

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1 n 1 n

T

f

B

t

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6P. L. L. BERTARINI - Coherent Optical Code Division Multiple Access (OCDMA) Systems

Encoding -> to spread in one or more dimensions:

Time Frequency Space Polarization

Maximize › Cardinality (number of simultaneous users)› Orthogonality (differentiation between users)

7


P. L. L. BERTARINI - Coherent Optical Code Division Multiple Access (OCDMA) Systems


OCDMA technologies:

› Incoherent OCDMA systems Manipulates intensity of optical field

› Coherent OCDMA systems Manipulates phase and amplitude of optical

field It appears to be the most viable technology for

the implementation of OCDMA systems *


* Optical Access Seamless Evolution (OASE), “Survey of next-generation optical access system concepts,” FP7/2007–2013, deliv. D4.1; http://www.ict-oase.eu/.

Data

Light Sourc

e

Phase Mask – A(w)

Prism or grating

SLM

Star Couple

and Optical Chann

el

DataModulat

or


Spectral Phase-Coding Time Spreading

Encoder

Fourier Transfor

m

Inverse Fourier Transfor

mSpetral Phase Code

– user K

Gaussian Optical Pulse Encoder



10

Fourier Transfor

m

Inverse Fourier Transfor

mSpetral Phase Code

– user K

Gaussian Optical Pulse Encoder

Encoded Signal

Encoding / decoding process

› The pulse reconstruction, or decoding, requires a conjugate code to be used, otherwise it will remain spread out as multiple access interference (MAI)

› Other devices are necessary to distinguish between correctly and incorrectly decoded users Time gate devices – NOLM Nonlinear thresholder



System Performance

› Walsh-Hadamard and m-sequence codes› “1” and “-1” represent phase shifts of “0” and

“π”

› Synchronism between active users› Worst case scenario


Methodology

A bit “1” is encoded with a given user's code, and then is imposed to all other users' decoders.

We are able to get the energy (interference) level received by each user.

This process is carried out for all possible code combinations.



We showed for the first time in OCDMA literature that each user differently interferes in all other users in the system› Ideal scenario → orthogonality between

codes› Realistic scenario → the MAI produced by

incorrectly decoded users coincide with the correctly decoded user’s signal


SPECTS-OCDMA systems Interference level caused by users (a) #12 and (b) #15 on

other users when a bit "1“ is sent. The dashed lines indicate the average energy value, equal to

0.286 for W-H 32 (left) and 0.277 for m-sequence (rigth).


Optimal code-set

BER evaluation › based on the interference level between active

user› each user has a different performance depending

on the interference caused by others active users

Optimal code-set selection

› The goal is to select the code-set that represents the best scenario for all possible code combinations

› best scenario: code-set with lowest BER for all users


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Optimal code-set

W-H 32 optimal code-set 3 simultaneous users: 992 (20%) out of 4960 → BER<10-12

1120 (22.6%) out of 4960 → BER<10-9

4 simultaneous users: 416 (1.16%) out of 35690 → BER<10-12 656 (1.82%) out of 35690 → BER<10-9

The maximum number of active users allowed to W-H 32 with satisfactory BER levels is only 4

BERTARINI , P. L. L., et al. - "Optimal Code Set Selection and Security Issues in Spectral Phase-Encoded Time Spreading (SPECTS) OCDMA Systems," Journal of Lightwave Technology, vol. 30, no. 12, June, 2012.


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Optimal code-set

W-H 64 optimal code-set

6 simultaneous users : 409600 (0.543%) out of almost 75 million → BER<10-12

7 simultaneous users: 262144 (0.042%) out of almost more than 621 million → BER<10-12

8 simultaneous users:65536 (0.0015%) out of more than 4 billion → BER<10-12

A random choice of the code-set will compromise the overall system performanceBERTARINI , P. L. L., et al. - "Optimal Code Set Selection and Security Issues in Spectral Phase-Encoded Time Spreading (SPECTS) OCDMA Systems," Journal of Lightwave Technology, vol. 30, no. 12, June, 2012.


Concluding remarks The code-set selection is necessary in order to

implement optical networks based on OCDMA technology

Code-set selection algorithm can be applied to any CDMA system, regardless the technology used

Some efforts have to be made to seek a STANDARD for CDMA technology in optical domain, such as G-PON for TDMA systems

We are currently working on security, robustness and scalability issues of coherent OCDMA networks


Thank you!

Coherent Optical Code Division Multiple Access (OCDMA) Systems

Pedro Luiz Lima Bertarini



International Workshop on Trends in Future Communications:High Performance Network Infrastructure for Future Internet23-25 February 2014, CPqD Auditorium, Campinas, SP- Brazil

coherent optical code division multiple access (ocdma) systems pedro bertarini

Technology

given users code

conjugate code

incoherent ocdma systems

ocdma technologies

active users optimal

ocdma literature

spetral phase code user

amplitude of optical