The short-reach optical interconnects used in datacenters and high-performance computing systems are dominated by VCSEL and multimode fiber (MMF) links1. The VCSEL-MMF technology is the most cost and power efficient and offers the smallest footprint. VCSELs operating at 25–28 Gbit/s are in production2 while research has extended the VCSEL modulation bandwidth to 30 GHz3 (Fig.1) and enabled OOK-NRZ data transmission up to 57 Gbit/s at 25°C4 and 50 Gbit/s at 85°C5, without equalization or forward-error-correction (FEC). A VCSEL energy dissipation below 100 fJ/bit has been demonstrated at 25–50 Gbit/s3 (Fig.1). The need for higher interconnect capacity raises the question whether the speed and dynamics of VCSELs can be further improved or whether physical limits preventing this have been reached. Higher speed VCSELs would enable higher lane rates and therefore reduced number of lanes and increased bandwidth density for a given aggregate interconnect capacity.
[1]
Johan S. Gustavsson,et al.
High-speed 850 nm VCSELs operating error free up to 57 Gbit/s
,
2013
.
[2]
Alex Mutig,et al.
Electro-optical resonance modulation of vertical-cavity surface-emitting lasers.
,
2012,
Optics express.
[3]
Johan S. Gustavsson,et al.
30 GHz bandwidth 850 nm VCSEL with sub-100 fJ/bit energy dissipation at 25–50 Gbit/s
,
2015
.
[4]
Kent D. Choquette,et al.
37-GHz Modulation via Resonance Tuning in Single-Mode Coherent Vertical-Cavity Laser Arrays
,
2015,
IEEE Photonics Technology Letters.
[5]
C. Schow,et al.
A 71-Gb/s NRZ Modulated 850-nm VCSEL-Based Optical Link
,
2015,
IEEE Photonics Technology Letters.