Photonic integration enabling new multiplexing concepts in optical board-to-board and rack-to-rack interconnects

New broadband applications are causing the datacenters to proliferate, raising the bar for higher interconnection speeds. So far, optical board-to-board and rack-to-rack interconnects relied primarily on low-cost commodity optical components assembled in a single package. Although this concept proved successful in the first generations of opticalinterconnect modules, scalability is a daunting issue as signaling rates extend beyond 25 Gb/s. In this paper we present our work towards the development of two technology platforms for migration beyond Infiniband enhanced data rate (EDR), introducing new concepts in board-to-board and rack-to-rack interconnects. The first platform is developed in the framework of MIRAGE European project and relies on proven VCSEL technology, exploiting the inherent cost, yield, reliability and power consumption advantages of VCSELs. Wavelength multiplexing, PAM-4 modulation and multi-core fiber (MCF) multiplexing are introduced by combining VCSELs with integrated Si and glass photonics as well as BiCMOS electronics. An in-plane MCF-to-SOI interface is demonstrated, allowing coupling from the MCF cores to 340x400 nm Si waveguides. Development of a low-power VCSEL driver with integrated feed-forward equalizer is reported, allowing PAM-4 modulation of a bandwidth-limited VCSEL beyond 25 Gbaud. The second platform, developed within the frames of the European project PHOXTROT, considers the use of modulation formats of increased complexity in the context of optical interconnects. Powered by the evolution of DSP technology and towards an integration path between inter and intra datacenter traffic, this platform investigates optical interconnection system concepts capable to support 16QAM 40GBd data traffic, exploiting the advancements of silicon and polymer technologies.

[1]  J. E. Bowers,et al.  Integrated Hybrid Silicon Transmitters , 2012, Journal of Lightwave Technology.

[2]  Heinrich Kurz,et al.  Fabrication of high efficiency SOI taper structures , 2009 .

[3]  Bernhard Schmauss,et al.  10.7-Gb/s Discrete Multitone Transmission Over 25-m Bend-Insensitive Multicore Polymer Optical Fiber , 2010, IEEE Photonics Technology Letters.

[4]  P. Westbergh,et al.  32 Gb/s multilevel modulation of an 850 nm VCSEL for next-generation datacommunication standards , 2011, CLEO: 2011 - Laser Science to Photonic Applications.

[5]  Dennis W. Prather,et al.  Myths and rumours of silicon photonics , 2012, Nature Photonics.

[6]  Di Liang,et al.  Teardrop Reflector-Assisted Unidirectional Hybrid Silicon Microring Lasers , 2012, IEEE Photonics Technology Letters.

[7]  F Y Gardes,et al.  40 Gb/s silicon photonics modulator for TE and TM polarisations. , 2011, Optics express.

[8]  P. Andrekson,et al.  30 Gbps 4-PAM transmission over 200m of MMF using an 850 nm VCSEL , 2011, 2011 37th European Conference and Exhibition on Optical Communication.

[9]  R Orobtchouk,et al.  Silicon Photonic Circuits: On-CMOS Integration, Fiber Optical Coupling, and Packaging , 2011, IEEE Journal of Selected Topics in Quantum Electronics.

[10]  W. Hofmann,et al.  Monolithic 2D high-power arrays of long-wavelength VCSELs , 2008, SPIE OPTO.

[11]  Mike Ignatowski,et al.  Exploitation of optical interconnects in future server architectures , 2005, IBM J. Res. Dev..

[12]  M. Koshiba,et al.  Reduction of crosstalk by quasi-homogeneous solid multi-core fiber , 2010, 2010 Conference on Optical Fiber Communication (OFC/NFOEC), collocated National Fiber Optic Engineers Conference.

[13]  Alexei Sirbu,et al.  Long-wavelength VCSELs: Power-efficient answer , 2009 .

[14]  C. L. Schow,et al.  120-Gb/s 100-m transmission in a single multicore multimode fiber containing six cores interfaced with a matching VCSEL array , 2010, IEEE Photonics Society Summer Topicals 2010.

[15]  P. Crozat,et al.  42 GHz p.i.n Germanium photodetector integrated in a silicon-on-insulator waveguide. , 2009, Optics express.

[16]  K. J. Larsen,et al.  High-Speed 1550 nm VCSEL Data Transmission Link Employing 25 GBd 4-PAM Modulation and Hard Decision Forward Error Correction , 2013, Journal of Lightwave Technology.

[17]  Andrew Alduino,et al.  Demonstration of a high speed 4-channel integrated silicon photonics WDM link with hybrid silicon lasers , 2010, 2010 IEEE Hot Chips 22 Symposium (HCS).

[18]  Mikhail V. Maximov,et al.  Oxide-confined 850 nm VCSELs operating at bit rates up to 40 Gbit/s , 2009 .

[19]  Mitchell Fields,et al.  Optical interconnects for chip-to-chip communications , 2010, 36th European Conference and Exhibition on Optical Communication.

[20]  Hong Liu,et al.  Scaling Optical Interconnects in Datacenter Networks Opportunities and Challenges for WDM , 2010, 2010 18th IEEE Symposium on High Performance Interconnects.

[21]  Jan Vandewege,et al.  High-speed electronics for short-link communication , 2013 .

[22]  P. Wolf,et al.  1550-nm High-Speed Short-Cavity VCSELs , 2011, IEEE Journal of Selected Topics in Quantum Electronics.

[23]  D. Reid,et al.  Ultrafast laser inscription of a three dimensional fan-out device for multicore fiber coupling applications , 2008 .

[24]  Ashok V. Krishnamoorthy,et al.  PAM-4 Signaling over VCSELs with 0.13microm CMOS Chip Technology. , 2006, Optics express.

[25]  D Van Thourhout,et al.  Heterogeneously integrated III-V/silicon distributed feedback lasers. , 2013, Optics letters.

[26]  John E. Bowers,et al.  Forty Gb/s hybrid silicon Mach-Zehnder modulator with low chirp. , 2011, Optics express.

[27]  Hon Ki Tsang,et al.  Fabrication-Tolerant Waveguide Chirped Grating Coupler for Coupling to a Perfectly Vertical Optical Fiber , 2008, IEEE Photonics Technology Letters.

[28]  Guo-Qiang Lo,et al.  50-Gb/s silicon optical modulator with traveling-wave electrodes. , 2013, Optics express.

[29]  C. L. Schow,et al.  225 Gb/s bi-directional integrated optical PCB link , 2011, 2011 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference.

[30]  C. L. Schow,et al.  A 40-Gb/s, 850-nm, VCSEL-based full optical link , 2012, OFC/NFOEC.

[31]  M. Romagnoli,et al.  An electrically pumped germanium laser. , 2012, Optics express.

[32]  M. Amann,et al.  1.55-$\mu$m VCSEL Arrays for High-Bandwidth WDM-PONs , 2008, IEEE Photonics Technology Letters.

[33]  Andrew C. Alduino.  Demonstration of a high speed 4-channel integrated silicon photonics WDM link with hybrid silicon lasers , 2010 .