Digital Signal Processing for High Spectral Efficiency Optical Transmission.pdf

Digital Signal Processing for High Spectral Efficiency Optical Transmission 1 Xiang Zhou ATT Labs-Research, Middletown, NJ, USA Jianjun Yu ZTE USA Inc, NJ (NEC Labs America, USA) 2Outline Motivation:??why?DSP Pre‐transmission?DSP ? Digital?pulse?shaping ? Digital?pre‐equalization Post‐transmission?DSP?for?high‐order?modulation?formats ? Polarization?tracking?and?compensation?algorithms ? Phase?tracking?algorithms 64Tb/s,?8b/s/Hz?demonstration?with?PM‐36QAM Conclusions 3? Ever growing network traffic drives the need for higher capacity in the core network ? Historically it has been shown that increasing bit rate per channel and spectral efficiency (SE) is more cost effective than lighting more fiber pairs Data rate per channel (Gb/s) 0 1 2 3 4 5 6 7 8 0 100 200 300 400 S E ( b / s / H z ) Deployed To be deployed Projected demand Growing Capacity demands higher SE 4Multi-dimension and multi-level coding ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??? ? ? ?? ? ? ? ? ? y y x x yy xx Q I Q I jQI jQI E Optical field of an optical carrier Information can be encoded/modulated on each one of the four dimensions 1) Higher spectral efficiency (SE) 2) Lower electrical processing speed Increase mod. dimension and mod. level at each dimension ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? y y x x j y j x a a ea ea y x ? ? ? ? E 5DSP-enabled digital modulator ?/2 MZM1 MZM2 D/A converter D/A converter DSP DSP Arbitrary I-Q modulation Additional advantages: 1) Raised-cosine pulse shaping for better SE 2) Digital pre-equalization for better signal quality 3) Software reconfigurable modulation formats 6DSP-enabled coherent detection X0? Pol. phase diverse hybrid O/E O/E O/E O/E X90? Y0? Y90? EX EL Signal LO A/D IX Qx j hxx Iy Qy j Clock Recovery hxy hyx hyy EQ1 hx hy EQ2 x y A/D A/D A/D DSP Carrier recovery Carrier recovery Decision Decision Fast polarization tracking PMD compensation Fast Phase tracking DSP algorithms not only allow the realization of coherent detection,