Silicon Photonic Transceivers Research Articles

Advanced Packaging Technology for High Density Silicon Photonics Transceiver Engines

Next generation high-density/high-data rate silicon photonics solutions will require advanced packaging technologies. Those include 3D integration, smaller micro-bumps or even bump-less chip-to-chip/wafer bonding technologies, advanced heatsinking and compatibility with optical packaging technologies. We will discuss results on wafer level optical assembly, 3D silicon photonics and future options to support the optical interconnect roadmap.

System Development of Radiation-Tolerant Silicon Photonics Transceivers for High Energy Physics Applications

System Development of Radiation-Tolerant Silicon Photonics Transceivers for High Energy Physics Applications

Advances in silicon photonics for high-capacity optical interconnects - INVITED

We review our recent progress on advanced silicon photonic devices and photonic circuits, including advanced grating couplers, modulators, mode and polarization division multiplexing and integrated optical signal processors for use in high capacity data center interconnects. The use of shifted polysilicon overlay gratings on waveguide grating couplers to improve coupling efficiency and polarization independence will be described. We also present our recent results on silicon microring and silicon-germanium electroabsorption modulators for 100Gbaud data transmission and their use polarization and mode division multiplexed optical fiber interconnects. We present novel integrated optical signal processors which can unscramble the mixing of polarization and mode data lanes that will occur after fiber transmission and demonstrate 400Gb/s per wavelength intensity modulation direct-detection silicon photonic transceivers.

Two-Dimensional High-Efficiency Transceiver Integrated Optical Phased Array With Dual-Port Antenna

We propose a 1 × 32 silicon photonics transceiver integrated optical phased array (OPA) with a large scanning angle. It can process receive and transmit signals simultaneously, which effectively increases the on-chip signal transmission efficiency. The simulation shows that the phase-tuned 62.2° lateral beam steering without grating lobe and the wavelength-tuned 31.2° longitudinal beam steering can be achieved in the transmitting mode, and the overall optical loss is less than 9.1 dB. In the receiving mode, the combination of the two detection methods reduces the complexity of the system while ensuring the sensitivity of the system. According to statistics, an effective collection area of 43.3% per unit area can be achieved in the receiving mode, which provides a reliable guarantee for subsequent high-quality signal processing.

Silicon photonics for high-capacity data communications

In recent years, optical modulators, photodetectors, (de)multiplexers, and heterogeneously integrated lasers based on silicon optical platforms have been verified. The performance of some devices even surpasses the traditional III-V and photonic integrated circuit (PIC) platforms, laying the foundation for large-scale photonic integration. Silicon photonic technology can overcome the limitations of traditional transceiver technology in high-speed transmission networks to support faster interconnection between data centers. In this article, we will review recent progress for silicon PICs. The first part gives an overview of recent achievements in silicon PICs. The second part introduces the silicon photonic building blocks, including low-loss waveguides, passive devices, modulators, photodetectors, heterogeneously integrated lasers, and so on. In the third part, the recent progress on high-capacity silicon photonic transceivers is discussed. In the fourth part, we give a review of high-capacity silicon photonic networks on chip.

High Efficiency Multimode Waveguide Grating Coupler for Few-Mode Fibers

We describe a novel high coupling efficiency multimode waveguide grating coupler which uses a polysilicon overlay numerically optimized to improve both the directivity and mode-matching of the grating coupler with different modes. The device was realized experimentally and designed with a large minimum feature size of 181 nm for fabrication by deep ultraviolet photolithography in the commercial foundry. Simulations predicted the coupling efficiencies to be −1.1 dB for LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode and −1.56 dB for the LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode. The experimentally measured coupling efficiencies were −1.36 dB and −2.21 dB for LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode and LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes, respectively. These results demonstrate a significant advance over previous designs, and have the potential for use in silicon photonic transceivers for mode division multiplexed communications in multimode fibers.

Silicon photonic transceivers in the field of optical communication

Silicon photonics has developed rapidly in recent years, which has received widespread attention due to the fact that it can overcome the bandwidth bottleneck in optical communications. This paper mainly introduces the key applications of silicon photonics in the field of communication. Through a detailed description of optical transceiver modules in the coherent optical communication and data center, the advantages of silicon optical technology in the field of communication are introduced, such as high speed, low power consumption, high bandwidth and cost-effective. The problems of fabrication, packaging, light source integration and related devices in the current applications of silicon photonics are briefly analyzed. In the future, silicon photonics technology is expected to have better application prospects in long-distance transmission, big data communication and other communication applications.

Electronic‐photonic board as an integration platform for Tb/s multi‐chip optical communication

Chip-on-board silicon photonics O-band wavelength-division multiplexing transceivers have been developed that will eventually enable high-throughput on-board optical communication for multi-socket on-board communication. This direct, any-to-any configuration yields low-latency, low-power optical communication among multiple compute nodes on the board. Silicon photonic transceiver chips are flip-chipped on a polymer waveguide containing an electro-optical circuit board using adiabatic coupling and then completed with driver and amplifier electronic chips. A transceiver assembly based on wire-bond technology verifies 50 Gb/s operation per channel, and the flip-chip version demonstrates the chip on-board assembly techniques for compact on-board transceivers.

Design Considerations for Energy Efficient DWDM PAM4 Transceivers Employing Avalanche Photodiodes

AbstractAn effective approach to increase per‐fiber bandwidth is to combine per‐wavelength four‐level pulse amplitude modulation (PAM4) with dense wavelength division multiplexing (DWDM). Silicon photonic transceivers based on microring resonator modulators and drop filters can allow for an efficient realization of this. Utilizing avalanche photodiodes (APDs) in the receiver front‐ends of these transceivers can significantly improve sensitivity, allowing for reduced source laser power and overall improved power efficiency. This paper analyzes the optical‐modulation amplitude (OMA) sensitivity of these APD‐based PAM4 receivers in a silicon photonic DWDM link. A comprehensive link budget is considered that takes into account various system losses and relevant noise sources. Modeling with a developed APD that has a maximum 230 GHz gain‐bandwidth product predicts sensitivity improvements at 32 to 64 Gb s−1 PAM4 ranging from 9.8 to 12 dB relative to a conventional p‐i‐n photodiode. Scaling the APD gain‐bandwidth to 310 GHz allows support of 112 Gb s−1 with −13.2 dBm OMA sensitivity at a BER of with an APD gain of 10. Utilizing the presented architecture, link budget analysis predicts a 9.5x reduction in laser power with APDs and that 38 mW source laser optical power can support a four‐channel DWDM link operating at an aggregate 448 Gb s−1 data rate.

GeSi EAM-Based 160 Gb/s Nyquist Half-Cycle Subcarrier Modulation Transmission

We demonstrate the transmission of beyond-100 Gb/s Nyquist half-cycle 16-quadrature-amplitude modulation (16-QAM) subcarrier modulation (SCM) signals with a compact silicon-based GeSi electro-absorption modulator. In combination with nonlinear compensation, the measured bit-error rate (BER) after 2 km standard single-mode fiber (SSMF) transmission is below the 20% hard-decision forward error-correction (HD-FEC) threshold of $1.5\times 10^{\mathbf {-2}}$ for single-lane 160 Gb/s operation. The presented modulator shows great potential for high-capacity and low-power-consumption silicon-photonic transceivers for data-center interconnects.

4-channel 200 Gb/s WDM O-band silicon photonic transceiver sub-assembly.

We demonstrate a 200G capable WDM O-band optical transceiver comprising a 4-element array of Silicon Photonics ring modulators (RM) and Ge photodiodes (PD) co-packaged with a SiGe BiCMOS integrated driver and a SiGe transimpedance amplifier (TIA) chip. A 4×50 Gb/s data modulation experiment revealed an average extinction ratio (ER) of 3.17 dB, with the transmitter exhibiting a total energy efficiency of 2 pJ/bit. Data reception has been experimentally validated at 50 Gb/s per lane, achieving an interpolated 10E-12 bit error rate (BER) for an input optical modulation amplitude (OMA) of -9.5 dBm and a power efficiency of 2.2 pJ/bit, yielding a total power efficiency of 4.2 pJ/bit for the transceiver, including heater tuning requirements. This electro-optic subassembly provides the highest aggregate data-rate among O-band RM-based silicon photonic transceiver implementations, highlighting its potential for next generation WDM Ethernet transceivers.

Silicon Photonic 2.5D Multi-Chip Module Transceiver for High-Performance Data Centers

Widespread adoption of silicon photonics into datacenters requires that the integration of the driving electronics with the photonics be an essential component of transceiver development. In this article, we describe our silicon photonic transceiver design: a 2.5D integrated multi-chip module (MCM) for 4-channel wavelength division multiplexed (WDM) microdisk modulation targeting 10 Gbps per channel. A silicon interposer is used to provide connectivity between the photonic integrated circuit (PIC) and the commercial transimpedance amplifiers (TIAs). Error free modulation is demonstrated at 10 Gbps with −16 dBm received power for the photonic bare die and at 6 Gbps with −15 dBm received power for the first iteration of the MCM transceiver. In this context, we outline the different integration approaches currently being employed to interface between electronics and photonics—monolithic, 2D, 3D, and 2.5D—and discuss their tradeoffs. Notable demonstrations of the various integration architectures are highlighted. Finally, we address the scalability of the architecture and highlight a subsequent prototype employing custom electronic integrated circuits (EICs).

Stable quantum key distribution using a silicon photonic transceiver.

The wider deployment of commercial quantum key distribution (QKD) may benefit from an integrated system with reduced cost, small form-of-factor and high robutness. Silicon photonic circuits are good candidates while their performance stability in some contexts remains a challenge. We demonstrate a silicon photonic QKD transceiver based on time-bin protocol. The stability of the transceiver is investigated and a feedback function is proposed to improve the temperature-dependent performance of the transceiver. With the help of a faster data-processing ability, such scheme can facilitate more application scenarios, therefore achieving wider implementation of QKD in the future.

Foundry-Enabled Scalable All-to-All Optical Interconnects Using Silicon Nitride Arrayed Waveguide Router Interposers and Silicon Photonic Transceivers

This paper summarizes our latest results of integrated all-to-all optical interconnect systems using compact, low-loss silicon nitride (SiN) arrayed waveguide grating router (AWGR) through AIM photonics’ multiple-project-wafer services. In particular, we have designed, taped out, and initially characterized a chip-scale silicon photonic low-latency interconnect optical network switch (Si-LIONS) system with an 8 × 8 200 GHz spacing cyclic SiN AWGR, 64 microdisk modulators, and 64 on -chip germanium photodector (PD). The 8 × 8 SiN AWGR in design has a measured insertion loss of 1.8 dB and a crosstalk of –13 dB, with a footprint of 1.3 mm × 0.9 mm. We measured an error-free performance of the microdisk modulator at 10 Gb/s upon 1Vpp voltage swing. We demonstrated wavelength routing with error-free data transmission using the on -chip modulator, SiN AWGR, and an external PD. We have designed and taped out the optical interposer version of the all-to-all system using SiN waveguides and low-loss chip-to-interposer couplers. Finally, we illustrate our preliminary designs and results of 16 × 16 and 32 × 32 SiN AWGRs, and discuss the possibility of scaling beyond 1024 × 1024 all-to-all interconnections with reduced number of wavelengths (e.g., 64) using the Thin-CLOS architecture.

Recent Progress in the Development of Large-Capacity Integrated Silicon Photonics Transceivers

Recent Progress in the Development of Large-Capacity Integrated Silicon Photonics Transceivers

Experimental evaluation of silicon photonics transceiver operating at 120°C for 5G antenna array systems

The use of optical transceivers in antenna array system applications requires reliable operation at high temperature. The experimental characterisation of a silicon photonics transceiver operating in a harsh environment with temperatures up to 120°C is presented and discussed. The transceiver was placed inside a climatic chamber and it was fed by an external depolarised light source. The bit error rate was measured, and the impacts on transmission performances were analysed and discussed, including reliability aspects. The authors believe that silicon photonics transceivers with an optimised design and with improvements in the optical connector and fibre adhesive technology are suitable for this kind of applications.

8-channel WDM silicon photonics transceiver with SOA and semiconductor mode-locked laser.

We demonstrate an integrated 8 by 14 Gbps dense wavelength division multiplexed silicon photonics transceiver that makes use of an external mode-locked laser as a light source and a single semiconductor optical amplifier for post-modulation signal amplification. Remaining components necessary for modulation, filtering and (de‑)multiplexing are monolithically integrated in a single chip. In all system experiments, all eight channels are jointly operated with independent data streams in order to include impairments arising out of nonlinear effects inside the SOA while benchmarking the system performance. The transmitter, measured with a commercial reference receiver, supports on-off keying data transmission with an uncorrected BER ranging between 1e-5 and 5e-7 for all channels in back-to-back configuration and between 8e-4 and 1e-5 after 10 km transmission (both PRBS 231-1). The three best channels of the full link consisting in the silicon photonics transmitter operated with the silicon photonics receiver in back-to-back configuration maintain a BER better than the targeted 5e-5. Based on link budget modeling, we expect this target to be reached for all 8 channels pending improvement of the receiver offset compensation loop.

1.3 μm InAs/GaAs quantum dot DFB laser integrated on a Si waveguide circuit by means of adhesive die-to-wafer bonding.

In this paper we report a single mode InAs/GaAs quantum dot distributed feedback laser at 1.3 μm wavelength heterogeneously integrated on a Si photonics waveguide circuit. Single mode lasing around 1300 nm with a side-mode suppression ratio higher than 40 dB is demonstrated. High temperature operation with continuous wave lasing up to 100°C is obtained. Threshold current densities as low as 205 A/cm2 were measured. These devices are attractive candidates to use in uncooled silicon photonic transceivers in data centers.

Silicon traveling-wave Mach-Zehnder modulator under distributed-bias driving.

The silicon traveling-wave (TW) Mach-Zehnder modulator (MZM) is one of the most important devices in silicon photonic transceivers for high-speed optical interconnects. Its phase shifter utilizes carrier depletion of pn diodes for high speed, but suffers low modulation efficiency. Extensive efforts have been made on pre-fabrication optimizations, including waveguides, doping, and electrodes to enhance high-frequency modulation efficiency. Instead, we here propose an adaptive post-fabrication distributed-bias driving method that enables 20%∼30% high-frequency efficiency enhancement at both 10 and 25 Gbps without doing any optimizations for a silicon TW-MZM. This method explores the bias nonlinearity of index modulation which, to the best of our knowledge, is utilized for the first time in driving silicon modulators to improve the efficiency. We demonstrated the viability of this adaptive driving concept to achieve better performance, and this Letter could open new avenues for silicon traveling-wave modulator design and performance trade-off.

Radiation Damage in Silicon Photonic Mach–Zehnder Modulators and Photodiodes

Radiation-hard optical links are the backbone of read-out systems in high-energy physics (HEP) experiments at CERN. The optical components must withstand large doses of radiation and strong magnetic fields and provide high data rates. Radiation hardness is one of the requirements that become more demanding with every new generation of HEP experiment. Previous studies have shown that vertical cavity surface emitting lasers, on which the current optical links are based, will not be able to withstand the expected radiation levels in the innermost regions of future HEP experiments. Silicon photonics (SiPh) is currently being investigated as a promising alternative technology to address this challenge. We irradiated SiPh Mach-Zehnder modulators (MZMs) with different design parameters to evaluate their resistance against ionizing radiation. We confirm that SiPh MZMs with a conventional design do not show a phase shift degradation when exposed to a 20-MeV neutron fluence of $3\cdot 10^{16}~{\rm n/cm^{2}}$ . We further demonstrate that custom-designed MZMs with shallow etch optical waveguides and high doping concentrations in their p-n junctions exhibit a strongly improved radiation hardness over devices with a conventional design when irradiated with X-rays. We also found that MZMs withstood higher radiation levels when they were irradiated at a low temperature. In contrast, larger reverse biases during irradiation led to a faster device degradation. Simulations indicate that a pinch-off of holes is responsible for the device degradation. Photodiodes (PDs) were also tested for their radiation hardness as they are needed in silicon photonic transceivers. X-ray irradiation of building-block germanium-silicon PDs showed that they were not significantly affected.