Improving network scalability and data security of incoherent OCDMA systems by employing ultra fast all-optical signal processing techniques

(1)

Improving scalability and data security

of incoherent OCDMA systems by employing

ultrafast all-optical signal processing techniques

Prof Ivan Glesk

Department of Electronic and Electrical Engineering

3rd _{International Workshop on OPS and OCDMA, October 23-24, 2008, Shanghai, China} Lightwave Communications Research Laboratory

Princeton

University

(2)

Acknowledgement

Prof Paul R. Prucnal

Dr. Lei Xu

(3)

• Introduction

• Incoherent OCDMA

• Enhancing performance with all-optical signal processing

–

MAI suppression

–

Improving security

–

Improving system power budget

–

increasing number of simultaneous users

–

Increasing scalability and spectral efficiency with M-ary encoding

• Experimental results

• Conclusions

Outline

(4)

2D Wavelength-Hopping Time-Spreading Codes

Incoherent OCDMA based on 2D prime codes

• Codes generated by simple one-line algorithm:

w = weight: # of wavelengths

p = code length: # of chips

i = code number

for j = 0: w-1

code(i +1, j +1) = mod(j i, p)*

+

1 End

1 p

λ

₁

λ

_w

Bit Interval

Time [ps]

Example: (4,11) 2D-WHTS

• Analytical expression for upper bound on BER

•

• The code scheme uses picosecond pulses at multiple wavelength to generate codes

(5)

Experimental set up to study laser coherence

Multiwavelength ps laser

)

cos(

2

₁ ₂

2

1

I

δφ

I

_tot

=

+

Interferometric equation:

4I

₀

2I

₀

“same” pulse interaction

Pulse is coherent with “itself”

“pulse to pulse” separation

NO interference is observed

Experimental results:

- 1.6 ps near transform-limited pulses efficiently utilize bandwidth

- Turn-key operation (< 40 fs timing jitter)

- High output power (15 dBm per wavelength)

(6)

OCDMA Transmitter transmitting 2D

-

WHTS codes

MOD

RF Data In: 1 0 1

λ

De M U X

M U X

D

2D Tunable Encoder

Encoded bit “1”

λ

₁

λ

_p

ps multi -

λ

laser

(7)

Receiver diagram

2D Tunable Decoder

From Network

Electronic Data bit

“1” λ

De M U X

M U X

D

-1

D

-1

D

-1

D

-1

D = reconfigurable optical delay lines

PD

D-1 _{= indicates “inverse” delay in reference to the delays D in the Transmitter}

Decoded signal: Data bit “1”

Cross-correlation signal from multiple users

τ

chip

τ

_PD

2D-code

(8)

OC

-

48 OCDMA Princeton

’

s Testbed

• OC- 48 data rate

• 4 Transmitters

• 1 Tunable Receiver/Decoder

2D (4,101) WHTS codes

(9)

Control Interface

(10)

Performance

–

with 4 simultaneous users

_{with 4 simultaneous users}

-20 -18 -16 -14 -12 -10 -8 -6 -4

1E-12 1E-11 1E-10 1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3

Bit Error Rate (log)

Power (dBm)

Transmitter 3

Transmitters 1,3

Transmitters 1,2,3

Transmitters 1,2,3,4

PD: 15 GHz photodiode

(11)

Transmitter 1 Transmitter 2 Transmitter 3 _{Transmitter 4}

Performance of each user

(12)

Electronic Data Out λ

De M

U X

M U X

D

-1

D

-1

D

-1

D

-1

PD

PD ~

τ

PD

2D-code

Electronic Data Out

λ

De M U X

M U X

D

All-optical gating

2D-code

Eliminating MAI with 2ps time gating

PD

Novel OCDMA receiver design

Conventional OCDMA receiver

~

τ

_PD

<

τ

_chip

(13)

TOAD

-

Terahertz Optical Asymmetric Demultiplexer

Glesk et. al., "Demonstration of All-Optical Demultiplexing of TDM Data at 250 Gb/s," Electronics Letters 30, 339 (1994)

Switching Window

sw =

(2Δ

x)/c

t 0

Δ

n

ΔΦ

~

Δ

n

Data IN

Data OUT

Clock IN

Δ

x

50/50

LP

P

NLE

AD

1/9

Clock

C B A

B

I = 120 mA

0 10 20 30 40

12 13 14 15 16 17

Input

Output SW=f(Δx)

1.8 ps

• Picosecond all-optical gating

• Low control pulse energy ~500fJ

• High SNR (BER < 10

-9

₎

• Was integrated

• 6 dB gain

(14)

Switching Window is a Function of SOA Displacement

0 5 10 15 20 25 30 35 40 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Time [ps]

TOAD Switching Windows (SW)

Calculated Measured

0 5 10 15 20 25 30 35 40 100 110 120 130 140 150 160 170 180 190 Time [ps]

Glesk et. al., "Polarization Insensitive Terabit Optical Demultiplexers," Proc. SPIE 2481, p. 13 (1995). Invited paper

- 5 0 5 1 0 1 5 2 0 2 5 3 0

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

T D L S e ttin g s ( m m )

E x p e r im e n t a l M e a s u r e m e n t s

Δ

x

SOA Data In Midpoint Clock DeMux Out Stretching TOAD

{

( ) ( ) 2 ( ) ( ) cos( ( ) ( ))

}

4 G1 t + G2 t ± G1 t G2 t

φ

1 t −

φ

2 t

=

1

( )

t SW (t) I

t I

In

(15)

TOAD

-

based receiver demonstration

TOAD

–

based OCDMA Receiver

OCDMA Receiver

–

NO Time Gating

Achieved

(16)

Performance improvement with all

-

optical time gating

Number of simultaneous users

Probability of Error

(4,101) 2D-Wavelength-Hopping Time-Spreading prime codes

10-9

2ps time gating

0 10 20 30 40 50 60 70 80 90 100

No time gating

(17)

Special features:

• Multi-level Security for users

• Implemented

One-time Pad

in optical domain to secure data

In collaboration with Lockheed Martin

-

OCDMA based

- bus network architecture

Secure communication platform

for avionics applications

4 × 1 c o mb in er

RF Code swapping

EDFA Tx-A Opt Enc

Tx-B Opt Enc

Tx-Dc Opt Enc

RF In Data A

RF In Data B

RF In Data D

Server p s mult iw av e len g th laser 3 3

Tx-Dd Opt Enc

3 MOD MOD 2 x 2 2 x 2

λ1,λ2

,λ3

1% taps

optical bus

99:1 99:1

99:1 _{RF Out}

Data A

PD OptDec Da

Rx-A RF Out

Data B PD OptDec Db Rx-B RF Out Data C PD OptDec Dc Rx-C Eavesdrop

RF Code swapping

RF Out Data D OptDec Dc OptDec Dd 2 x 2 Rx-D PD

(18)

Concept of One

-

time Pad

Electronic XOR

Problems:

–

RF signature radiation which may be

vulnerable to side channel attacks

–

Electronic speed limited to a few GHz

Optical layer XOR

Advantages:

–

Encoded data never exists in electronic

form

–

No RF signature is generated

Data

Data KeyKey XOR OutXOR Out

0

1

0

1

0 Traditional electronic XOR

Traditional electronic XOR

Novel optical approach

(19)

Dual-code transmitter

OptEnc “D₁”

OptEnc “D₂”

Fast 2×2 Switch

RF Data In

Σ

OptDec “D₁”

OptDec “D₂”

d₁d₁d₁d₁

d₂d₂d₂d₂

RF Data Out

PD

Switch Control: “1” bar “0” cross

Decryption

Optical implementation of One

-

time Pad

Optical bus

Dual-code receiver

Fast 2×2 Switch Key

Encryption

Data modulation

Optical

(20)

Experimental demonstration

d₂: 1 3 5

Used codes

D D 1 × 4 D D 1 × 4 RF Key in λ₂ λ₀ λ₁ λ₂ λ₀ λ₁

OptEnc “d₁”

OptEnc “d₂”

Control:

“1” bar “0” cross

RF Data In

Fast 2×2 Switch D D D D Fast 2×2 Switch PLC PLC PLC PLC PLC PLC Optical Encoders

λ₁λ₀λ₂

λ₁ λ₀ λ₂

OptEnc “C₁” output

800 ps

OptEnc “C₂” output

800 ps

d₁: 1 2 3

Optical

(21)

Out

Rx-C

D D 1 × 4 1 × 4 TFF2 TFF0 TFF1 D D 1 × 4 1 × 4 TFF2 TFF0 TFF1 Fast 2×2 Switch

key = 27 _{-1 PRBS sequence}

PD 2x1

Optical Decoder “C₁”

PLC

λ1 λ0 λ2

Optical Decoder “C2 ”

D D 1 × 4 1 × 4 TFF2 TFF0 TFF1 PD

Optical Decoder “C1 ”

Rx-Eve

Out

RF

Code C

₂

Encrypted Encrypted Input Input

correlation:

Decoded

bit “1”

Switch Control:

“1” bar “0” cross

Operation of secure

channel

and eavesdropper

_{and eavesdropper}

Output of Rx-EVE

Output of Rx-D

With Key ON, an

(22)

When D does no code swap: One-time Pad OFF

–

EVE can eavesdrop with good performance (red diamonds)

When D does code swap: One-time Pad ON

–

EVE cannot eavesdrop, data cannot be received,

no BER can be obtained

With code swapping no BER

could be obtained on

eavesdropper channel

-26 -24 -22 -20 -18 -16 10-14

10-12 10-10 10-8 10-6 10-4 10-2

BER (log)

Rx D (27-1 swap) TxD only

Rx D (27-1 swap), all Txs Rx EVE (no swap) TxD only

(23)

Path to miniaturization

(24)

Tx-D D D 1 × 4 D D 1 × 4 Swapping Pattern λ₂ λ₀ λ₁ λ₂ λ0 λ1 “Dc” OptEnc “Dd” OptEnc Control: “1” bar “0” cross Data Fast 2×2 Switch D D 1 × 4 D D 1 × 4 Fast 2×2 Switch PLC PLC PLC PLC PLC PLC Optical Encoder Tx-D Tx-D 99:1 FC/UPC FC/UPC FC/UPC Tap D Tx-D D D 1 × 4 D D 1 × 4 Swapping Pattern λ₂ λ₀ λ₁ λ₂ λ0 λ1 “Dc” OptEnc “Dd” OptEnc Control: “1” bar “0” cross Data Fast 2×2 Switch D D 1 × 4 D D 1 × 4 Fast 2×2 Switch PLC PLC PLC PLC PLC PLC PLC PLC PLC PLC PLC PLC Optical Encoder Tx-D Tx-D 99:1 FC/UPC FC/UPC FC/UPC Tap D Rx-D D D 1 × 4 1 × 4 TFF2 TFF0 TFF1 D D 1 × 4 1 × 4 TFF2 TFF0 TFF1 Fast

2×2 Switch Swapping Pattern PD 2x1 “Dc” OptDec “Dd” OptDec Control: “1” bar “0” cross PLC FC/UPC FC/UPC FC/UPC Tap Tap Rx-D D D 1 × 4 1 × 4 TFF2 TFF0 TFF1 D D 1 × 4 1 × 4 TFF2 TFF0 TFF1 Fast

2×2 Switch Swapping Pattern PD 2x1 “Dc” OptDec “Dd” OptDec Control: “1” bar “0” cross PLC PLC FC/UPC FC/UPC FC/UPC Tap Tap

Thin film filters (TFFs) in combination

with fiber delay lines

Holographic Bragg Reflectors

(HBRs)

Optical Decoder

Path to miniaturization through integration

(25)

Top View of Integrated Encoder

HBR

-

based Dual code Encoder/

Decoder

Single device can process two 2D codes simultaneously including wavelength selection

0

λ1 λ2 λ3

500 ps

code0 (1,2,3)

code1 (1,3,5)

(26)

(27)

Princeton

(28)

M

-

ary concept

• Motivation:

–

Higher spectral efficiency

M-ary sends multiple bits of information per one symbol transmitted

• How?

–

Uses pulse positioning (PPM)

–

Needs all-optical method for symbols decoding at high data rates

• We implemented M-ary with 4 levels

–

Hardware can operate at a lower rate

(29)

• We implemented M-ary modulation with 4 levels

– Increases number chips in code sequence by converting 10Gbps data to M-ary at 5G (each M-ary symbol contains 2 bits of information)

τ₀

τ₀+ 100ps _τ

1

τ₁+ 50ps

Switch 1 Switch 2 Electronic board From SC source 100ps 150ps 50ps 0ps delay (1 1) (1 0) (0 1) (0 0)

(C₁C₂)

11 10 01 00 Data 2D D S3 S2 S1 S0 symbol τ₀

τ₀+ 100ps _τ

1

τ₁+ 50ps

Switch 1 Switch 2 Electronic board From SC source 100ps 150ps 50ps 0ps delay (1 1) (1 0) (0 1) (0 0)

(C₁C₂)

11 10 01 00 Data 2D D S3 S2 S1 S0 symbol

PPM M-ary encoding architecture and symbol correspondence

C-S. Brès et al, “Novel M-ary Architecture for Optical CDMA using Pulse Position Modulation,” IEEE LEOS Sydney, Australia, 2005, paper ThBB1

2T ps (frame period) T ps

(bit period)

2 bits IN at x Gb/s 1 pulse OUT

Electrical domain Optical domain 0 0

0 1

1 0

1 1

00 01 10 11 2T ps (frame period) T ps (bit period)

1 pulse OUT at x/2 Gb/s

Electrical domain Optical domain 0 0

0 1

1 0

1 1

00

10

11

Concept of M

(30)

BERT

All

-

optical M

-

ary Decoder

TOAD 1 TOAD 2 TOAD 3 1 x 4 Control pulse

00

01

10

11

200ps _100ps 1 x 2 1 x 4 5 Gsym/s 10 Gb/s PD 1 x 4 1 x 2 1 x 2

TOAD receivers

Experimental illustration of parallel TOAD gating S0 S1 S3 S2

S1

S3

S2

0 1

1 0

1 1

50 ps

Split, delay, combine Delay and position In last half of frame

Delay and position In first half of frame

From TOAD 1 From TOAD 2 From TOAD 3 OUTPUT INPUT 100 ps Autocorrelation Peaks 11 10 01 00 S2 S3 S1 S0 S1 S3

0 1

1 0

50 ps 100 ps S1 11 10 01 00 S1 S0

• Pulse

is present in one and

only one PPM slot:

– Position pulse back within the 100ps bit according to the M- ary code received

– “00” symbol can be used for clock recovery

(31)

Experimental Results

• Encoded M-ary data:

– 1 pulse per symbol ( 00, 01, 10 or 11) within 200ps

• Decoded M-ary data:

– Original 10Gb/s data recovered

– Pulses equally spaced every 100ps

Decoded M-ary data

200ps [01] [11] [11] [10][11] [00] [00] [00]

200ps

0 1 1 1 1 1 1 0 1 1 0 0 0 0 0 0 Encoded M-ary data

• Eye patterns:

–

Random superposition of the 4 PPM slots:

4 eyes within 200ps, 50ps apart

–

Recovered pattern: 10Gb/s eye

Eye before decoding Eye after decoding

Symbol interval

100ps

Bit interval

[01] [00] [10] [11] 50ps

(32)

Additional All

-

optical signal processing is added

Before OCDMA decoder After OCDMA decoder After TOAD time gating

Experimental BER for Tx3 for 1 to 8 user case Comparison of theory and experiment

Autocorrelation

Cross-correlation

Autocorrelation

Total Received Power (dBm)

1E-11 1E-10 1E-09 1E-08 1E-07 1E-06 1E-05 1E-04 1E-03

-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0

BER (log)

1 users 4 users 6 users 8 users

10-20 10-15 10-10 10-5

Number of simultaneous users K

Probability of error (log)

0 20 40 60 80 100

(33)

50 70 90 110 130 150 10-13 10-12 10-11 10-10 10-9 10-8 10-7

Number of Simultaneous Users K

P ro b a b ility o f e rro r ( lo g )

Scaling using M

-

ary 8 levels

110 Users at 10-9

M-ary 8 levels

%

8 .

112

75

13

10

110 =

×

=

SE

GHz

users

SE

1369

=

φ

y

cardinalit

Number of

simultaneous users

@ 10

-9

_{BER = 110}

(34)

(35)

Add/Drop Code Multiplexers for OCDMA Ring Network

1. Ring with code add/drop, code

lives only between add / drop

points

• Avoids interception of data by downstream nodes

• Code can be reused in separate parts of ring

• Enables scaling size of ring by code re-use

2. Full interconnection possible without switching

Drop Add Add Drop Add Drop

Drop

Add

Drop Drop

Add

Drop

Drop Add

Code 1 Code 1

(36)

Topology of Self-Healing OCDMA Node with Distributed Processing

SW1

Data link in

Data link out Backup link

out

Backup link in

OCDMA Add/Drop

Module SW2

Received Data

Transmitted Data

Monitor/ protection

circuit

Each node monitors the integrity of fiber optic link in both directions.

Protection switches SW1 & SW2 reroute the data if a node/link failure is detected.

Improving network scalability and data security of incoherent OCDMA systems by employing ultra fast all-optical signal processing techniques

Improving scalability and data security

of incoherent OCDMA systems by employing

ultrafast all-optical signal processing techniques

Prof Ivan Glesk

Prof Ivan Glesk

Princeton

University

Acknowledgement

Prof Paul R. Prucnal

Dr. Lei Xu

•

Introduction

•

Incoherent OCDMA

•

Enhancing performance with all-optical signal processing

–

MAI suppression

–

Improving security

–

Improving system power budget

–

increasing number of simultaneous users

–

Increasing scalability and spectral efficiency with M-ary encoding

•

Experimental results

•

Conclusions

Outline

Incoherent OCDMA based on 2D prime codes

Incoherent OCDMA based on 2D prime codes

•

Codes generated by simple one-line algorithm:

w = weight: # of wavelengths

p = code length: # of chips

i = code number

for j = 0: w-1

code(i +1, j +1) = mod(j * i, p)

+

1

End

1

p

λ

λ

Example: (4,11) 2D-WHTS

•

Analytical expression for upper bound on BER

•

•

The code scheme uses picosecond pulses at multiple wavelength to generate codes

Experimental set up to study laser coherence

Multiwavelength ps laser

Multiwavelength ps laser

)

cos(

2

I

I

I

δφ

I

I

=

+

+

Interferometric equation:

4I

2I

Experimental results:

OCDMA Transmitter transmitting 2D

OCDMA Transmitter transmitting 2D

-

-

WHTS codes

WHTS codes

RF Data In: 1 0 1

code(i +1, j +1) = mod(j i, p)*

_{with 4 simultaneous users}