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 21 st October 2010

Outline 1.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 Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 3

Ch. 1. Entertainement: 3D IPTV, Games  International Funkausstellung of Berlin (IFA 2010) presented commercial 3D IPTV in Sept.10 ADSLGPON (TDM) (WDM) Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 4

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 Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 5

Ch. 1. SOCIAL APPLICATIONS Telehealth conference Lunch together Fiber to the School FTTH Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 6

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 AWG WDM TDM splitter Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 7

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 ) in a broad margin –Integrable –Can amplify and re-use the downstream for the upstream (no specific laser at the ONU) – Although RSOA presents low bandwidth and chirp: –Chapter 3: 10Gb/s with RSOA Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 8

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 CH 3 CH 2 Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 9

Outline 1.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 10

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 AWG WDM Upstream SIGNAL  Tunable laser is expensive for ONU  We want to re-use the light coming from the OLT Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 11

Ch. 2. Wavelength Shifting up = down ± fs down down up RB  To shift the upstream with respect to the downstream  Enough to avoid overlap  Maintaining the new inside the same AWG channel  We have obtained 5-7dB of improvement regarding crosstalk tolerance AWG data ONU MOD down up f s WS RX OLT Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 12

Outline 1.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 13

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 devices  1.5GHz) –Chirp (modulating I modulates also P )  penalty after fibre Tx Data Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 14

Ch. 3. Offset Filtering Due to the RSOA e/o chirp: From 0 to 1  CW to shorter From 1 to 0  CW to longer Proper detuning: the slope of the filter can reshape the signal  BW increases System limited in BW: not fast enough to follow consecutive 1-0 transitions CW Electrical input data Modulated optical output Optical Filter OLT ONU Optical Filter LASER scope RSOA data Modulated Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 15

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) Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 16

Outline 1.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 17

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. Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 18

Thanks!! This work has been funded by the Spanish Ministry of Science and Education by the FPI grant BES associated to the investigation project MEC TEC Also supported by the European e-Photon/ONe, EuroFos and BONE NoE, the FP7 SARDANA project and the Spanish MEC project TEC (TEYDE). Mireia Omella Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing 19