Self Coherent Detection & Reflective Modulation for Optical Access Networks (FTTH) Amos Agmon, Moshe Nazarathy Technion, Israel Institute of Technology Talk given at Optical Engineering 2014 Netanya, Israel

Outline Motivation and system design guidelines Introduction: Optical Detection and Motivation to Self-coherent detection Reflective Modulation Combining Down-Stream(DS) & Up-stream (US) OTONES Network design Conclusions 2

Power dissipation of Information and Communication Equipment* 3 Shared Network Equipment ~ 1 W/user Access Network and Home Gateway: ~ 10 W/user Home Devices: ~ 100 W/user Customer Premises * Interview with P. Vetter, Bell Labs, Sep-2010,

Motivation & Design Guidelines Access Networks required to increase data throughputs while reducing power dissipation Designing an access-network (FTTH) allowing for low-complexity, power-efficient Optical Network Units (ONU=Customer Premises Equipment) – Laserless, colorless low complexity ONUs – Low rate signal processing – ≥ 1 Gbps ONU peak Down-Stream (DS) throughput – FSAN Class B+ ODN (29 dB loss budget per Optical Distribution Network (ODN)) – Split ratio ≥ 1:64 4

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Intro. : Optical Transmission 6 doubling data throughput by means of simultaneous transmission of I & Q

Intro. : Optical Detection 7

8 PD

Intro. : Optical Detection 9

Intro. : Limits of Direct Detection 10 Undetectable I-Q Mixture PD

Solution: Coherent (heterodyne) Det. 11 PD LO

Coherent Det. drawbacks Complex and expensive: Tunable laser required Prone to frequency drifts and Phase noise, highly stable lasers required for large constellations Phase noise is enhanced by Equalization Currently, Coherent Det. is prohibitive for mass deployed communication links 12

Self Coherent Tx 13 LO mixed at Tx output: Tx

Self Coherent Advantages Reduced Rx complexity: Single Photo-Diode, Laserless, colorless Tx Remains simple: Generating a locked pair is not hard Phase noise immunity: Both for Laser PN & Non-linear Self Phase Modulation (SPM)! 14 PN canceled out!

Self Coherent - Summary Spectral efficiency of Coherent Detection Allows for Linear equalization (CD, PMD mitigation) Laser coherency (Linewidth) does not effect Rx performance→ Low quality laser may be used Simple Tx & Rx 15

Up-Stream: Reflective Modulation for Laserless Optical Network Unit (ONU) 16 ONU US Carrier source 3 dB coupler

Uni-directional Reflective Modulation 17 Reflective Tx

Bi-directional Reflective Modulation 18 Reflective Tx

Bi-directional Reflective Modulation 19 Optical SSB Reflective Tx PUDG pattern

OTONES network A new bi-directional access network designed from the ground up at the system, sub-system and component levels – low-cost – power-efficient – long-reach – spectral-efficiency Applying Self-coherent det. & reflective modulation 1 Gbps (peak) per user, low rate ADC (<500 MSamp/s) Total Throughput: – Class I: 10G/10G over 12.5 GHz – 40 dB reach - lowest-cost – Class II: 20G/20G over 25 GHz – 38.5 dB reach - mid-cost – Class III: 40G/40G over 50 GHz – 35 dB reach - highest cost 20

Plant architecture of OTONES long-reach PON: 11 dB feeder fiber optical filtering +OA Class B+ ODNs: 29 dB Loss budget 11 dB feeder + 29 dB ODN =40 dB loss budget (Class I) Backward-compatible w/ existing ODN PON Plant and may even co-exist with (X)GPON, TWDM, etc. 21

OTONES OTONES ONU A patent app was filed early in 2010 X-POL REMOD Y-POL REMOD 22 MIXED-SIGNAL ASIC thin-film optical filter identical for all ONUs “colorless” ONU ! (no tunable or variable parameters filter in ONU) Laserless reflective ONU ! US re-mod of DS light by coherent 16-QAM identical on both X,Y polarizations

23 ADC/DAC: 156 MHz 417MS/s narrowband filter and detect just one stream ENERGY EFFICIENT MIXED-SIGNAL ONU ASIC Spectral Design DS DET

OTONES simulation results OLT output Hub output, RHS slice filtered down ONU PD output, electrical OLT input ONU DS 16-QAM constellation after max-ratio polarization-diversity combining SNR=18.5 dB OLT US16-QAM constellation after max-ratio polarization-diversity combining SNR=18.5 dB 24 Ideal 16-QAM SNR=16.5 dB at BER= dB margin

Bi-directional Network simulation using a Matlab- Simulink Model were performed at the Technion ONU Photonic Integrated Circuit (PIC) – Developed at Karlsruhe Institute of Technology (KIT), Germany, Expected May-’14 ONU Digital Rx implemented at Technion-IIT, on a Xilinx Virtex-6 chip OLT Digital Rx, Optical SSB modulator – Implemented at Technion-IIT, expected during Apr-’14 Proof of concept experiments – planned during Q2 ‘14 OTONES Network Prototype is currently under implementation 25 PIC mask – courtesy of Philipp Schindler, KIT, Germany

Conclusions Self Coherent Detection – Cost effective scheme for spectral efficient low cost optical links Reflective Modulation – Cost effective scheme for bi-directional transmission in access networks Both techniques may be applied in future optical access networks (FTTH) 26

that’s it 27

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