Client Network

Client Network

Low-speed packet

Low-speed packet

High-speed packet

Core Network

Proposed core optical router

Source / target node

All-optical router

Buffer

Input

Output

Main modules Optional modules

Packet

Delay unit

Clock Extraction

Header Extraction

Header Recognition

Look-up Routing Table

Reconfiguration

Optical Switching Unit

Controlling Contention

Signal Processing (2R, 3R, equalization)

Splitter

Symetric Mach-Zehnder Interferometer(SMZI)

CP1

SOA1

SOA2 CP2

Input Output 1

Output 2

To design a bi-directional SMZ and implement it in the router to reduce components, time and cost.

To optimize the performance of the SOA to be adapted for bi-directional operation.To overcome the slow time recovery of the SOA gain.To propose a bi-directional model for the SOA.To design a bi-directional model for the SMZ and implement it in the proposed router.

Injection current (I)

L

Input facet of active region Input signals

Output signals

Output facet

H

w

Energy gap

E2 (conduction band)

E1 (valence band)

Stimulated absorption

Stimulated emission

Spontaneous emission

Hole Electron (carrier)

Photon Inducing photon

Stimulated photon

Input optical signal (photon)

Output amplified optical signal

segment1

segment2

………….. …………….

segment5

t=0 t=l/vgg

t=L/vg

input signal

output signal

Ni

N(1)

N(5)

0 1 2 3 4 5 6

x 10-9

0

0.2

0.4

0.6

0.8

1

Time (s)

Nor

mal

ized

gai

n • Normalised gain response of the SOA with no input signal.

• Normalised gain response of the SOA due to the injection of a short input pulse.

0 1 2 3 4 5 6

x 10-9

0

0.2

0.4

0.6

0.8

1

Time (s)

Nor

mal

ized

gai

n

Injection of the input pulse

• Normalised gain response of the SOA due to the injection of a continuous input signal.

0 1 2 3 4 5 6

x 10-9

0

0.2

0.4

0.6

0.8

1

Time (s)

Nor

mal

ized

gai

n

Injection of the continuous wave

Saturation gain

Condition: The signal should not be affected by the SOA

nonlinear effect (i.e: SOA gain depletion should not reach saturation value).

Note: The reference is the saturation value for a 1mW

continuous input signal.

• The output gain corresponding to the input power at different bias currents.

•Reference saturation gain:

• at I=150mA 66• at I=200mA 96• at I=250mA 1270 1 2 3 4 5 6 7 8 9 10

0

500

1000

1500

2000

2500

Input power (mW)

Out

put

gain

I=250mA

I= 200mA

I=150mA

• Condition:– The signal should be affected by the nonlinearity of

the SOA and achieve a 180o phase shift for the deconstructive interference. (i.e: SOA gain depletion of a control pulse (CP) should reach the gain saturation value).

• Note:– A control pulse (CP) is required to be launched to

the SOA, then the input signal should be injected in order to achieve the 180o phase shift.

• The saturation control pulse (CP) for the corresponding input power at different bias currents.

1 2 3 4 5 6 7 8 9 102

4

6

8

10

12

14

16

18

20

Input power (mW)

CP

inpu

t po

wer

(m

W)

I=150 mA

I=200mA

I=250 mA

• SOA gain dependence on the bias current.

0 50 100 150 200 25010

15

20

25

30

35

40

Bias current (mA)

SO

A g

ain

(dB

)

• Normalised gain response of the SOA due to the injection of a short input pulse.

0 1 2 3 4 5 6

x 10-9

0

0.2

0.4

0.6

0.8

1

Time (s)

Nor

mal

ised

gai

n

Recovery time

• Normalised gain response of the SOA due to partial increase of the bias current.

0 1 2 3 4 5 6

x 10-9

0

0.2

0.4

0.6

0.8

1

Time (s)

Nor

mal

ised

gai

n

segment1

segment2

………….. …………….

segment5

t=0 t=l/vgg

t=L/vg

Propagating input signal

Propagating output signal

Partial increase of bias current

• SOA gain recovery due to the additional of different bias currents.

0 10 20 30 40 50 60 70 80 900

100

200

300

400

500

600

700

800

900

Additional bias current (mA)

Rec

over

y tim

e of

the

SO

A g

ain

(ps)

100% recovery

99% recovery

95% recovery

Recovery time=37ps

Improvement of:86% for 95% recovery90% for 99% recovery84% for 100% recovery

• SOA bit rate due to the additional bias current.

0 10 20 30 40 50 60 70 80 900

5

10

15

20

25

30

Additional bias current (mA)

SO

A b

it ra

te (

Gb/

s)

100% recovery

99% recovery

95% recovery

SOA bit rate=27.027 Gbps

Improvement of:7.5 times at 95% recovery

• Time needed to apply additional bias current.

10 20 30 40 50 60 70 80 9020

40

60

80

100

120

140

160

Additional bias current (mA)

Tim

e ne

eded

to a

pply

add

ition

al b

ias

curre

nt (p

s)

Time needed :35ps for 90mA154ps for 10mA

segment1

segment2

………….. …………….

segment5

t=0 t=l/vgg

t=L/vg

Propagating input signal

Propagating output signal

Co-propagating input signal

Co-propagating output signal

Uni-directional SMZ

Bi-directional SMZ

Practical work on the SMZ.The replacement of active components in the router by passive components (FBGs) such as demultiplexing, add/drop devices, filtering, and switching .Solving the contention resolution problem using a novel multiplexing solution.

The SOA is modelled using a segmentation method.The effect of input parameters on the gain and carrier density response of an SOA is presented.Optimum performance conditions are investigated in which the SOA can be used as a standalone amplifier and in a SMZ switch.The dependence on of the SOA on the bias current is presented.

Results show an acceleration in the gain recovery time due to partially increasing the bias current applied to the SOA. SOA gain recovery time and bit rate corresponding to the additional bias current is investigated.

Optical Communication Research Group

Northumbria Communication Research Laboratory

School of Computing, Engineering, Information and Sciences

Ultra-fast all-optical WDM router based on bidirectional SMZs and FBGs.

Submitted Accepted/Completed Rejected/Delayed

Conference/ Journal Abstract Full Paper

STCEII (Msc) 2006 Published

ICC 2008 (co-author) Published

ICEE 2008 (co-author) Published

SENACITEL 2008(co-author) Accepted

PGNET 2008 Published

ICON-MW 2008 Accepted Submitted

ELECTRONICS LETTER Submitted to supervisor