Low power optical 1µm-range optical interconnection system at OFC/NFOEC2009
- The lowest power record of 7mW/Gbps in optical link -

Furukawa Electric Co. Ltd. intends to introduce a very low power optical interconnection systems of 10-Gbps xx 12-channel by using a 1µm-wavelength-range high efficient VCSEL array at OFC/NFOEC2009 held at San Diego, CA, USA from March 23 to March 26 2009.

Back ground of development

Optical interconnects have been a promising solution in high capacity data communication in the next generation because it overcomes the bottleneck of transmission distance and data rate realized in electrical interconnects. Another driving force to realize reducing link power has been growing to meet the motivation to reduce total power in data center. Conventional short reach systems have employed 850nm-range based on GaAs semiconductor devices. We have proposed to use InGaAs devices having a high differential gain at 1µm-range in the next generation 10-Gbps x 12-channels optical interconnect systems. The 1µm-range optical kink has the following benefits:

1. Low driving current and voltage of VCSEL
   Employing InGaAs strained layer quantum well, the VCSEL has high modulation efficiency and temperature-insensitive characteristic. This feature enables the high speed modulation at 10Gbps with a low driving current and a high temperature. A low driving power of VCSEL contributes to low power performance of optical module.
2. 1-µm wavelength signal transmission in fiber
   The chromatic dispersion in a silica fiber in 1-µm wavelength is three times smaller than that of 850-nm. This contributes to cost reduction derived from spec relaxation of spectral width of VCSEL and a bandwidth of fiber. On the other hand, the usage of InGaAs material in PD array contributes to the responsivity increase of 25%. This high efficient O-E conversion is also a benefit to realize low power consumption.

Achievements

We minimized the mechanical size of parallel-optical modules to meet the requirement of high-density mounting on electronics boards for board-to-board applications in high-end servers and routers. For the system maintenance purpose, the capability of replacing optical modules is required. Therefore, we have also proposed a solution of electrical-pluggable socket.

In a technical session in OFC2009, we intend to present the followings:

1. We fabricated 10-Gbps x 12-channel parallel-optical modules to target a low power optical link by using a 1-µm high efficient VCSEL. We achieved a low power of <0.84W at the case temperature ranging from 15°C to 80°C and 120-Gbps error free transmission in a MMF of 300m, simultaneously. To our knowledge, the power consumption per bandwidth of 7mW/Gbps is the lowest record for the optical links using such optical modules. This result will be introduced at the Furukawa/OFS booth.
2. We achieved successful 1,000-m signal transmission on the 10-Gbps x 12-channel optical link consisting of optical modules and a customized MMF for 1-µm wavelength. This result is going to be presented at the oral presentation of OTuK1.

Features of optical modules

• High link capacity: 10Gbps x 12channel (i.e., 120Gbps)
• Low power consumption: Link power per bandwidth = 7mW (Tc: 15°C to 80°C)
• Wavelength: 1060nm
• Small mechanical size 13mm x 13mm x 3.4mm, 21.7mm x 21mm x 13.7mm with the electrical-pluggable socket
• Product release: 2010

Appendix

Figure 1 Photograph
Upper: Equipped in socket and heat sink
Lower: Parallel-optical module

Figure 2 Introduction of optical interconnection

Figure 3 Optical interconnection in board-to-board

Figure 4 Structure of optical link

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