Mitigation of Mode Partition Noise in Quantum-dash Fabry-Perot Mode-locked Lasers using Manchester Encoding Mohamed Chaibi*, Laurent Bramerie, Sébastien Lobo, Christophe Peucheret *chaibi@enssat.fr FOTON Laboratory, CNRS UMR 6082, University of Rennes 1, ENSSAT, 22300 Lannion, France European Conference on Optical Communication 2016 20/09/2016
Silicon photonics technology Motivation Compatibility with CMOS-based technologies Silicon-based modulators, filters and photo-detectors have been demonstrated Heterogeneous integration of III/V materials Integrated transceivers with reduced footprint and low power consumption Silicon based WDM transmitter Frequency comb generated by a Fabry-Perot mode-locked laser (FP-MLL) Array of silicon modulators Mode partition noise (MPN) limitation 2
Mode partition noise The optical power in one mode fluctuates much more than the total power Optical modes compete with each other for a common injected carrier population All modes detected Eye diagram 0 Optical Spectrum -100 Relative intensity noise All modes Power (dbm) -20-40 -60-80 1540 1550 1560 1570 W avelength (nm) RIN (dbc/hz) -110-120 -130-140 0 2 4 6 8 Frequency (GHz) 3
Mode partition noise The optical power in one mode fluctuates much more than the total power Optical modes compete with each other for a common injected carrier population Mode 1 detected Eye diagram 0-10 Optical Spectrum -100 Relative intensity noise All modes Mode 1 Power (dbm) -20-30 -40-50 RIN (dbc/hz) -110-120 -130-60 -70 1550 1552 1554 1556 1558 1560 Wavelength (nm) -140 0 2 4 6 8 Frequency (GHz) 3
Mode partition noise The optical power in one mode fluctuates much more than the total power Optical modes compete with each other for a common injected carrier population Mode 2 detected Eye diagram Power (dbm) 0-10 -20-30 -40-50 Optical Spectrum RIN (dbc/hz) -100-110 -120-130 Relative intensity noise All modes Mode 1 Mode 2-60 -70 1550 1552 1554 1556 1558 1560 Wavelength (nm) -140 0 2 4 6 8 Frequency (GHz) 3
Outline 1) Serial ring resonators based WDM transmitter 2) New approach to mitigate mode partition noise ٥ Balanced detection ٥ Manchester encoding 3) Experimental setup 4) Comparison between NRZ and Manchester 5) Performance using RIN-emulated source 6) Conclusions 4
WDM transmitters Common WDM architecture Bulky structure Need for line-by-line frequency control 5
WDM transmitters Quantum-dash MLL (QD-MLL) based transmitter 100 GHz channel spacing 0 Channel # 1 2 3 4 5 6 7 8 9 10-10 Power (dbm) -20-30 -40-50 -60-70 1545 1550 1555 1560 Wavelength (nm) 5
WDM transmitters Quantum-dash MLL (QD-MLL) based transmitter 100 GHz channel spacing 0 Channel # 1 2 3 4 5 6 7 8 9 10-10 Power (dbm) -20-30 -40-50 -60-70 1545 1550 1555 1560 Wavelength (nm) Use of saturated SOA to mitigate the MPN [M. Gay et al., Tu2H.5, OFC 2014] 5
WDM transmitters Quantum-dash MLL (QD-MLL) based transmitter 100 GHz channel spacing 0 Channel # 1 2 3 4 5 6 7 8 9 10-10 Power (dbm) -20-30 -40-50 -60-70 1545 1550 1555 1560 Wavelength (nm) Use of saturated SOA to mitigate the MPN Focus on serial ring resonators based transmitter Each MRR modifies the intensity of a single line [M. Gay et al., Tu2H.5, OFC 2014] [Q. Xu et al., 9431, Opt. Express 2015] 5
Balanced detection Mitigation of mode partition noise Reduction of MPN impact for analogue links Not compatible with non-return to zero (NRZ) modulation [A. Joshi et al., 5814, SPIE 2005] 6
Balanced detection Mitigation of mode partition noise Reduction of MPN impact for analogue links Not compatible with non-return to zero (NRZ) modulation Manchester encoding Compatible with balanced detection The spectral content is shifted towards high frequencies Doubled bandwidth with respect to NRZ Combining balanced detection and Manchester encoding to mitigate MPN [A. Joshi et al., 5814, SPIE 2005] Power (dbm) -30-40 -50-60 -70-80 10 Gb/s spectra NRZ Manchester -90 0 5 10 15 20 Frequency (GHz) 6
Experimental setup 10 highest OSNR modes of the QD-MLL are considered Pseudo-random binary sequence length: 2 31-1 Bitrate per mode: 10 Gb/s External cavity laser (ECL) used as reference Manchester NRZ 7
NRZ with single ended-detection 10-2 10-4 BER 10-6 10-8 10-10 10-12 ECL Mode 2-45 -40-35 -30-25 -20 Received power (dbm) More than 2 db penalty for the best mode at a BER of 10-9 8
NRZ with single ended-detection 10-2 BER 10-4 10-6 10-8 10-10 10-12 ECL Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 Mode 6 Mode 7 Mode 8 Mode 9 Mode 10-45 -40-35 -30-25 -20 Received power (dbm) More than 2 db penalty for the best mode at a BER of 10-9 Large dispersion of the BER performance BER floors as high as 10-4 8
Manchester encoding with balanced detection BER 10-2 10-4 10-6 10-8 10-10 10-12 ECL Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 Mode 6 Mode 7 Mode 8 Mode 9 Mode 10 Improvement of the BER performance Less than 2 db penalty at a BER of 10-9 for the worst mode BER floors appear below 10-10 -45-40 -35-30 -25-20 Received power (dbm) At this stage, it is still not clear whether the balanced detection or the use of Manchester encoding is responsible of this improvement Need for an optical source with adjustable RIN behavior 9
How to emulate the RIN? An arbitrary waveform generator (AWG) generates the low-frequency part of the RIN An amplified spontaneous emission (ASE) source generates the constant level of the RIN -100-110 Experimental Output 1 1 2 3 RIN (dbc/hz) -120-130 -140-150 0 2 4 6 8 10 12 Frequency (GHz) 10
How to emulate the RIN? An arbitrary waveform generator (AWG) generates the low-frequency part of the RIN An amplified spontaneous emission (ASE) source generates the constant level of the RIN -100-110 Experimental Output 1 Output 2 1 2 3 RIN (dbc/hz) -120-130 -140-150 0 2 4 6 8 10 12 Frequency (GHz) 10
How to emulate the RIN? An arbitrary waveform generator (AWG) generates the low-frequency part of the RIN An amplified spontaneous emission (ASE) source generates the constant level of the RIN 1 2 3 RIN (dbc/hz) -100-110 -120-130 -140 Experimental Output 1 Output 2 Output 3-150 0 2 4 6 8 10 12 Frequency (GHz) 10
BER for different RIN levels: balanced detection RIN (dbc/hz) -100-105 -110-115 -120-125 -130 Integrated RIN over the occupied bandwidth -22 dbc -25.6 dbc -29.6 dbc Level 1 Level 2 Level 3 Level 4 BER 10-2 10-4 10-6 10-8 Level 1 Level 2 Level 3 Level 4-135 -140-34.5 dbc 10-10 -145 0 2 4 6 8 10 12 Frequency (GHz) 10-12 -45-40 -35-30 -25 Received Power (dbm) Increasing the RIN level slightly decreases the balanced detection sensitivity 11
BER for different RIN levels: single ended-detection RIN (dbc/hz) -90-100 -110-120 -130-140 Level 1 Level 2 Level 3-150 0 2 4 6 8 10 12 Frequency (GHz) BER BER performance with single ended-detection for NRZ and Manchester encoding 10-2 10-4 10-6 10-8 10-10 10-12 Level 1 Manchester Level 2 Manchester Level 3 Manchester Level 1 NRZ Level 2 NRZ Level 3 NRZ -22.1 dbc -45-40 -35-30 -25-20 -15 Received Power (dbm) -21.1 dbc -23.4 dbc -29.2 dbc -21.9 dbc -33.5 dbc Introducing Manchester encoding is not sufficient to provide better performance than NRZ 12
Conclusions WDM transmitters based on a QD-MLL and a serial array of of ring resonators Mitigation of MPN using Manchester encoding and balanced detection 10 modes modulated at 10 Gb/s are used to demonstrate the approach Effectiveness even at high RIN levels Manchester encoding alone is unable to provide better performance than NRZ benefit essentially stems from balanced detection 13
Acknowledgements Funded by the European Union Energy efficient silicon transmitter using heterogeneous integration of III-V quantum dot and quantum dash materials 14