Analysis of TSMC's Optical Interconnect Technologies: Vertical Broadband Coupler and iOIS System

Terence S.-Y. Chen

Latitude Design Systems

Abstract

The vertical broadband coupler (BBC) is a type of optical coupler that can couple light vertically between an optical fiber and an optical waveguide. It is designed to have a broad bandwidth, which means it can couple light over a wide range of wavelengths. The BBC is part of TSMC’s Integrated Optical Interconnect System (iOIS), which is a platform for co-packaged optics (CPO) that combines a compact universal photonic engine (COUPE2.0) and a composite interposer (CI) for high-performance computing and communication systems.

The COUPE2.0 is a high-performance optical engine that uses a vertical broadband coupler to connect with fibers and a SoIC bond to connect with electrical ICs. It can support wavelength division multiplexing (WDM) and heterogeneous integration of various optical devices. The CI is a highly integrated dual electrical- and optical-interconnection (DEOI) network that provides low-loss, high-bandwidth, and flexible optical routing among different optical engines. It also provides high-density electrical interconnection between ASICs and optical engines.

Introduction

Optical interconnects have become increasingly important in high-performance computing and communication systems due to their high bandwidth, low power consumption, and low latency. However, the integration of optical components with electrical components has been challenging due to the differences in fabrication processes, materials, and packaging. Co-packaged optics (CPO) is an emerging technology that aims to address these challenges by integrating optical components with electrical components in the same package.

TSMC’s Integrated Optical Interconnect System (iOIS) is a platform for CPO that combines a compact universal photonic engine (COUPE2.0) and a composite interposer (CI). The COUPE2.0 is a high-performance optical engine that uses a vertical broadband coupler to connect with fibers and a SoIC bond to connect with electrical ICs. The CI is a highly integrated dual electrical- and optical-interconnection (DEOI) network that provides low-loss, high-bandwidth, and flexible optical routing among different optical engines.

Design of the Vertical Broadband Coupler

The vertical broadband coupler (BBC) is a type of optical coupler that can couple light vertically between an optical fiber and an optical waveguide . The BBC is designed to have a broad bandwidth, which means it can couple light over a wide range of wavelengths. The BBC achieves broadband coupling by using a vertical broad-band coupler (VBC) that can couple light over a wide range of wavelengths . The VBC uses a tapered waveguide structure to achieve low-loss coupling between the fiber and the waveguide. The VBC also uses a grating structure to couple light into the waveguide, which allows it to achieve broadband coupling over a wide range of wavelengths .

The BBC has several advantages over other types of couplers used in optical communication systems. For example, the BBC has a larger spot size (~10 μm) than the edge coupler (~1 μm), which means it has a higher alignment tolerance and a lower coupling loss. The BBC is also designed to have a broad bandwidth, which means it can couple light over a wide range of wavelengths. This is unlike the grating coupler, which is wavelength dependent and cannot be used as a broadband coupler. The BBC can also integrate a polarization beam splitter and rotator (PBSR) and an embedded microlens to further enhance the coupling performance and flexibility.

Table 1 Comparison between various fiber couplers

Performance of the Vertical Broadband Coupler

In COUPE2.0, a novel vertical broad-band coupler (BBC) which combines GC and EC’s merits, is designed to effectively implement WDM and further reduce OE’s size. Being a vertical coupler, it is compatible with multiple-row vertical FAU with insertion loss of -0.3dB and alignment tolerance of r10 μm. High performance polarization beam splitter and rotator (PBSR) can be integrated with this vertical BBC. FAU alignment tolerance can be extended to greater than ±20 μm with proper integrated micro-lens and FAU designs. By disabling the beam deflecting mechanism, this BBC can also be used as a high-performance horizontal fiber coupler.

Applications of iOIS

TSMC’s Integrated Optical Interconnect System (iOIS) has several advantages over other CPO structures. For example, iOIS has a higher bandwidth density than other CPO structures due to its use of wavelength division multiplexing (WDM). iOIS also has a lower power consumption than other CPO structures due to its use of low-loss optical interconnects. In addition, iOIS has a higher design flexibility than other CPO structures due to its use of a composite interposer (CI) that provides low-loss, high-bandwidth, and flexible optical routing among different optical engines.

Future Work

The vertical broadband coupler (BBC) and TSMC’s Integrated Optical Interconnect System (iOIS) have several potential applications in high-performance computing and communication systems. However, there are several challenges that need to be addressed before these technologies can be widely adopted. For example, the fabrication of the BBC and other optical components needs to be integrated with the fabrication of electrical components in the same package. In addition, the packaging of the BBC and other optical components needs to be optimized for high-volume manufacturing.

Conclusion

The vertical broadband coupler (BBC) is an important component of TSMC’s Integrated Optical Interconnect System (iOIS), which is a platform for co-packaged optics (CPO) that combines a compact universal photonic engine (COUPE2.0) and a composite interposer (CI) for high-performance computing and communication systems. The BBC is designed to have a broad bandwidth, which means it can couple light over a wide range of wavelengths.

TSMC’s Integrated Optical Interconnect System (iOIS) has several advantages over other CPO structures, such as improved performance, reduced power consumption, and increased design flexibility. However, there are several challenges that need to be addressed before these technologies can be widely adopted.