Longer Wavelength GaAs-Based VCSELs for Extended-Reach Optical Interconnects
Doktorsavhandling, 2020

Data centers of today are increasing in size and are built to accommodate strong traffic demands while providing sustainably by having clients sharing resources under one roof. Their massive scale puts pressure on the server network topology and has incited a need for data transmission links that are energy efficient and capable of operation at high bit rates with reach up to a few kilometers. Optical interconnects (OIs) offer large bandwidth and low attenuation at long distances, and are therefore suitable for this task. The most commonly used OIs, with 850 nm GaAs-based vertical-cavity surface-emitting lasers (VCSELs) and multi-mode fiber (MMF), have a 25 Gb/s reach that is limited to a few hundred meters. However, the fiber chromatic dispersion and attenuation that limit the OI reach can be reduced significantly by increasing the wavelength of this very same technology. The upper limit of the GaAs-based VCSEL technology, with strained InGaAs quantum wells (QWs), is about 1100 nm.

With further improved OI performance, new hyperscale data center topologies can be realized and explored. This will lead to a larger number of possible solutions in traffic engineering as well as for power management. 1060 nm VCSELs could soon open up for lane rates of 100+ Gb/s over distances up to 2 km and help reach the Tb/s link speed aim of data center OI standards, in which capacity is built up mainly by employing multiple parallel lanes, increasing symbol rate by going from binary to four-level pulse amplitude modulation (PAM-4), and optimizing with electrical mitigation techniques such as digital signal processing.

In this work we show that 1060 nm GaAs VCSELs are suitable light sources for long-reach OIs by first demonstrating their overall stable performance and capability of error-free data transmission up to 50 Gb/s back-to-back and 25 Gb/s over 1 km of MMF. With PAM-4, we show 100 Gb/s error-free capability over 100 m of MMF, suitable for wavelength division multiplexed OIs that can transmit data at several wavelengths from 850 to 1060 nm over the same fiber channel. We also assemble single-mode 1060 nm VCSEL and single-mode fiber links and demonstrate 50 Gb/s error-free transmission over 1 km using pre-emphasis and 40 Gb/s over 2 km without the use of any electrical mitigation techniques. These results stem from careful VCSEL design, including strained InGaAs QWs with GaAsP barriers, doped AlGaAs distributed Bragg reflectors, a short optical cavity and multiple oxide layers. In addition, we show that the fabrication of such a device poses no increase in complexity and can be realized using standard processing techniques.

reach

high-speed modulation

multi-mode

single-mode

vertical-cavity surface-emitting laser

attenuation

chromatic dispersion

optical interconnect

A423 (Kollektorn), MC2, Kemivägen 9. Online: https://youtu.be/4F3dcIa4WP8
Opponent: Dr. Nicolae Chitica, Finisar Sweden AB

Författare

Ewa Simpanen

Chalmers, Mikroteknologi och nanovetenskap (MC2), Fotonik

1060 nm single-mode vertical-cavity surface-emitting laser operating at 50 Gbit/s data rate

Electronics Letters,; Vol. 53(2017)p. 869-870

Artikel i vetenskaplig tidskrift

1060 nm VCSELs for long-reach optical interconnects

Optical Fiber Technology,; Vol. 44(2018)p. 36-42

Artikel i vetenskaplig tidskrift

1060 nm Single-Mode VCSEL and Single-Mode Fiber Links for Long-Reach Optical Interconnects

Journal of Lightwave Technology,; Vol. 37(2019)p. 2963-2969

Artikel i vetenskaplig tidskrift

Simpanen, E., Gustavsson, J. S., Debernardi, P., Sorin, W. V., Mathai, S., Tan, M. R., Larsson, A., Noise properties of single-mode VCSELs: Dependence on current confinement and optical loss

Pre-emphasis enabled 50 Gbit/s transmission over 1000 m SMF using a 1060 nm single-mode VCSEL

Electronics Letters,; Vol. 54(2018)p. 1186-1187

Artikel i vetenskaplig tidskrift

Error-Free 100Gbps PAM-4 Transmission over 100m OM5 MMF using 1060nm VCSELs

Optics InfoBase Conference Papers,; Vol. Part F160-OFC 2019(2019)

Paper i proceeding

Optiska datakablar med multi-Tbit/s kapacitet

Stiftelsen för Strategisk forskning (SSF), 2014-03-01 -- 2019-06-30.

Drivkrafter

Hållbar utveckling

Styrkeområden

Nanovetenskap och nanoteknik (SO 2010-2017, EI 2018-)

Ämneskategorier

Atom- och molekylfysik och optik

Kommunikationssystem

Infrastruktur

Nanotekniklaboratoriet

Lärande och undervisning

Pedagogiskt arbete

ISBN

978-91-7905-242-3

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4709

Utgivare

Chalmers tekniska högskola

A423 (Kollektorn), MC2, Kemivägen 9. Online: https://youtu.be/4F3dcIa4WP8

Online

Opponent: Dr. Nicolae Chitica, Finisar Sweden AB

Mer information

Senast uppdaterat

2020-03-20