Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing

OP3: New Generation FTTH ONU and OLT Design for Upstream Transmission in WDM PON Including Optimized Combination of Electronics and Optics

Author Mireia Omella, Advisors: Josep Prat & Jose A. Lázaro

Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing

21st October 2010

Outline1.Introduction

2.Bidirectional transmission: RB Mitigation Wavelength Shifting

3.RSOA-based ONUs

10 Gb/s operation

4.Conclusions

Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 2

Ch. 1. Introduction – FTTH Motivation Current fixed access networks are mainly based on copper wires used for

analogue telephone transmission (low frequencies)

With the advent of data communication between computers, they were additionally utilized for digital signal transmission.

Capacity of copper cables limited the access part of the network has become a bottleneck

Fiber To the Home (FTTH) is a future-proof solution, but it has been delayed due to

• economics

• regulation

• interest from the main operators in the persistence of existing technologies

As a result, new services and applications are waiting for the adequate infrastructure


Ch. 1. Entertainement: 3D IPTV, Games

International Funkausstellung of Berlin (IFA 2010) presented commercial 3D IPTV in Sept.10

3D Ultra

3D Super

3D HDTV

2D Ultra

3D Standard-def. TV

2D Super

2D HDTV

2D Standard-def. TV

1 10 100 1000 10000Mb/s

3D Ultra

3D Super

3D HDTV

2D Ultra

3D Standard-def. TV

2D Super

2D HDTV

2D Standard-def. TV

1 10 100 1000 10000

3D Ultra

3D Super

3D HDTV

2D Ultra

3D Standard-def. TV

2D Super

2D HDTV

2D Standard-def. TV

1 10 100 1000 10000

3D Ultra

3D Super

3D HDTV

2D Ultra

3D Standard-def. TV

2D Super

2D HDTV

2D Standard-def. TV

1 10 100 1000 10000Mb/s

ADSL GPON (TDM)

(WDM)


Ch. 1. BUSINESS: Telepresence

Cost and time effective solution for business meetings Avoids the environmental impact resulting from the

combustion of aviation engines Requires reliable internet connection, symmetrical traffic,

good resolution and low time delays for voice and image

Telepresence is a set of technologies that allow video conferencing in such a way that the user feels as if they are actually at the remote site


Ch. 1. SOCIAL APPLICATIONS

Telehealth conference

Lunch together

Fiber to the School

FTTH


Ch. 1. Thesis structure-context

• FTTH success optimize infrastructure• Passive Optical Networks (PON)

Passive: don’t require electrical power supply in all the outside plant

AWG: Array waveguide grating

ONU: Optical Network Unit

OLT: Optical Line Terminal ONU

OLT AW

G

WDM

TDMsplitt

er


http://upload.wikimedia.org/wikipedia/commons/f/f2/Arrayed-Waveguide-Grating.svg

Ch. 1. Thesis structure-context• Bidirectional transmission reduces number of required

fibres but Rayleigh Backscattering (RB) can limit the performance Chapter 2: RB mitigation

• Identical ONUs helps at reducing cost – Reflective Semiconductor Optical Amplifier (RSOA) is an

interesting device as a ONU transmitter:– Colourless (independent of l) in a broad margin– Integrable– Can amplify and re-use the downstream l for the upstream (no specific

laser at the ONU)

– Although RSOA presents low bandwidth and chirp:– Chapter 3: 10Gb/s with RSOA


Ch. 1. SARDANA Network• DWM (Ring) / TDM(Trees)• Completely passive outside plant• Erbium doped fibre at the remote nodes (RN)• Remotely-pumped amplification from the CO

CO

RN1 RN2

RNi

RNj

RNN RNN-1

1:K

ONU ONU

1:K

ONU ONU

ONU ONU

1:K RSOA

ONU

D m+1,…, D

2N

WDM RING

TDM TREE

D1,…, D

m

Downstream Signals

Upstream Signals

U 1,…, U

2N

U1,…, U

2N

Bidirectional Transmission

PIN/APD

ONU ONU

ONU ONU

ONU ONU

CO

RN1 RN2

RNi

RNj

RNN RNN-1

1:K

ONU ONU

1:K

ONU ONU

ONU ONU

1:K RSOA

ONU

D m+1,…, D

2N

WDM RING

TDM TREE

D1,…, D

m

Downstream Signals

Upstream Signals

U 1,…, U

2N

U1,…, U

2N

Bidirectional Transmission

PIN/APD

ONU ONU

ONU ONU

ONU ONU

CH 3

CH 2

Scalable Advanced Ring-based passive Dense Access Network Architecture




3.RSOA-based ONUs

10 Gb/s operation:

4.Conclusions


Ch. 2. Rayleigh Backscattering (RB)Downstream SIGNAL

RB

RS is created by microscopic fluctuations of refractive index. It is related to the inhomogeneities in the material structure. RB is usually used for fibre link monitoring by OTDR equipment It can create impairment in bidirectional transmissions

As a light wave propagates along an optical fibre, it continually loses energy due to Rayleigh scattering (RS)

Part of this energy comes back to the source: called Rayleigh Backscattering (RB)

OLT AW

G

WDM Upstream SIGNAL

Tunable laser is expensive for ONU

We want to re-use the light coming from the OLT


Ch. 2. Wavelength Shifting

lup = ldown ± lfs

ldown

ldown

lup

RB

To shift the lupstream with respect to the ldownstream Enough to avoid overlap Maintaining the new l inside the same AWG channel

We have obtained 5-7dB of improvement regarding crosstalk tolerance

AW

G

dataONU

MOD

ldown lup

fs

WS

RX

OLT




3.RSOA-based ONUs

10 Gb/s operation:

4.Conclusions


Ch. 3. RSOA-based ONUs• A Reflective Semiconductor Optical Amplifier (RSOA) is an

optoelectronic device that under suitable operating conditions can:– Amplify an input optical signal– Modulate it (E/O)– Reflect towards the input port

• This is very interesting because:– Avoids a different laser for each ONU

• A fixed laser limits the network flexibility• Tunable laser is very expensive

• RSOA limitations:– Low Bandwidth (best commercial devices1.5GHz)– Chirp (modulating I modulates also P ) penalty after fibre Tx

Data


Ch. 3. Offset Filtering

-35

-30

-25

-20

-15

-10

-5

0

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4

nm

dB

Due to the RSOA e/o chirp:• From 0 to 1 CW to shorter l• From 1 to 0 CW to longer l

Proper detuning: the slope of the filter can reshape the signalBW increases

System limited in BW: not fast enough to follow consecutive 1-0 transitions

A. B. B-B 10 Km

CWCW

RC filter+Bias-T

10Gb/s PPGPRBS: 231-1

TXOUT

RXIN

OSNR emulator

10Gb/s BER

PIN + TIA

OSAOSNR monitor

FFE

DFE

Ta

p

Co

ntr

olle

r

Equalizer

FFE

DFE

Ta

p

Co

ntr

olle

r

Equalizer

RF

RSOA

12

3

L Km

TEC

ONU OLT

SMF-28no DCF

BPFEDFA Attenuator CouplerCirculator

A. B. B-B 10 Km

CWCW

RC filter+Bias-T

10Gb/s PPGPRBS: 231-1

TXOUT

RXIN

OSNR emulator

10Gb/s BER

PIN + TIA

OSAOSNR monitor

FFE

DFE

Ta

p

Co

ntr

olle

r

Equalizer

FFE

DFE

Ta

p

Co

ntr

olle

r

Equalizer

RF

RSOA

12

3

L Km

TEC

ONU OLT

SMF-28no DCF

BPFEDFA Attenuator CouplerCirculator

CW

Electrical input data

Modulated optical output

Optical Filter

OLT ONU

OpticalFilter

LASER

scope

RSOA

data

Modulated


Ch. 3. Offset Filtering + Electronic equalization

• When offset filtering is applied together with electronic equalization:

• An 85km at 10Gb/s (BER=10-9) long upstream transmission has been demonstrated when the downstream wavelength was a CW signal (no RB).

• Full duplex (with downstream also modulated) bidirectional transmission at 10 Gb/s has been also reported for the first time (25-35km)




3.RSOA-based ONUs

10 Gb/s operation:

4.Conclusions


Conclusions

• FTTH is the solution to overcome BW limitation in access networks.

• A method to overcome the RB in bidirectional transmission has been presented, allowing 5-7 dB improvement of crosstalk tolerance

• First reported real time 10G operation with low BW RSOAs nowadays rated for 1.25 Gb/s operation with the techniques explained in the thesis up to 85 km

• The novel techniques analyzed and experimentally tested in this thesis provide a path to upgrade next-generation PONs to 10 Gb/s, as new standards (XG-PON, 10G-EPON) propose.


Thanks!!This work has been funded by the Spanish Ministry of Science and Education by the FPI grant BES-2006-13417 associated to the investigation project MEC TEC2005-05160.

Also supported by the European e-Photon/ONe, EuroFos and BONE NoE, the FP7 SARDANA project and the Spanish MEC project TEC2008-01887 (TEYDE).

Mireia [email protected]


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Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing