L évolution des systèmes de transmission optique très haut débit et l impact de la photonique sur silicium G. Charlet 27-November-2017 1
Introduction Evolution of long distance transmission systems: from direct detection to coherent Modulation format and receiver description Toward high baudrate systems Silicon photonic integration 2
Evolution of transmission systems: from direct detection to coherent Direct detection was the conventional way to detect optical signal. = QUADRATIC detection of electric field Optical signal Electrical signal ~ A s (t) ² Limitations for higher bit rate because of - Chromatic dispersion - Polarization mode dispersion (PMD) Limited spectral efficiency 3
Evolution of transmission systems: from direct detection to coherent Coherent detection = LINEAR detection of the electric field, by beating with local oscillator (LO) 4 A e i( ω t+ϕ ( t)) s 0 (1)+(2) Electrical signal s Optical signal Signal + (1) π (1)-(2) - ~A s.ai LO 1( t) = PD 1 ( t) PD 2 ( t) Coherent i lot A Mixer loe ω π/2 (1)+j(2) (2) I 2 ( t ) = PD 3 ( t ) PD 4 ( t) Local oscillator (LO) (1)-j(2) + π/2 - Local oscillator I1( t) = 4 As Alo cos[( ω s ω lo ) t + ϕ ( t)] In phase I I ( t) = 4 A A sin[( ω ω ) t + ϕ ( )] Quadrature Q 2 s lo s lo t
Evolution of transmission systems: from direct detection to coherent Modulation and detection of 4 dimensions Laser Local oscillator I Ix mod Qx mod Iy mod Qy mod X Y signal Pol. splitter 3dB // Coherent mixer Coherent mixer Q I // Q // ADC ADC ADC ADC DSP 5
Modulation From QPSK to 16QAM and 64QAM @32Gbaud 25% FEC QPSK 100Gb/s 16QAM 200Gb/s 64QAM 300Gb/s Higher signal integrity required for 16/64QAM Shorter reach (reduction by factor of ~5 between each format) 6
Baudrate and bandwidth requirements From 32Gbaud to 64Gbaud First generation of coherent systems (2010-2013) designed around 30Gbaud Current highest speed systems operates at 44 to 56Gbaud 64Gbaud seen as the next step, to continue to reduce cost per bit. Bandwidth requirement ~ baudrate / 2 Bandwidth > 32GHz for all components (DAC, drivers, modulator, photodiode, TIA, ADC) 7
Silicon photonic for coherent system Receiver integration and ANR MICROS project Goal: integration of tunable laser with polarization diversity coherent receiver. Local oscillator (InP) Coherent mixer X Balanced PD (Ge) Pol splitter + rotator Functional device and packaging Coherent mixer Y - But too large loss (8 to 17dB excess loss depending on polarization) - Laser integration planned, but not integrated in the packaged device 8
Silicon photonic for coherent system Transmitter integration and ANR ULTIMATE project Tunable laser I/Q modulator I/Q modulator SO A SO A 20Gb/s PDM BPSK measurement PDM I/Q modulator 9
PDM I/Q Modulator and coherent receiver Courtesy of Po Dong 10 OFC2013 PDP 5C6, Po Dong
Expectations from WDM industry Large numbers of key parameters to be met simultaneously 11
Competition from InP integration Large variety of material used in WDM industry - LiNbO3 modulator - PLC (Silica) - Free space optics Coherent mixer - InP for modulator, receiver, laser 12
Conclusion Silicon photonic integration is a promising technology for future WDM systems. All key building block demonstrated. Acacia successful in producing PDM I/Q modulator and coherent receiver. Pure InP manufacturers have today mature technology and high performance products. InP integration with Silicon photonic is an attractive path. Reducing cycle duration (from design to chip to packaging) might be important. I am counting on you to build a strong and performing Silicon photonic industry in Europe 13