Silicon Photonic Transmitter Research Articles

A 4×112 Gb/s PAM-4 Silicon-Photonic Transmitter and Receiver Chipsets for Linear-Drive Co-Packaged Optics

A 4×112 Gb/s PAM-4 Silicon-Photonic Transmitter and Receiver Chipsets for Linear-Drive Co-Packaged Optics

An approach for designing energy-efficient integrated silicon photonics transmitters

An approach for designing energy-efficient integrated silicon photonics transmitters

PAPR Reduction and Nonlinearity Mitigation of Optical Digital Subcarrier Multiplexing Systems With a Silicon Photonics Transmitter

PAPR Reduction and Nonlinearity Mitigation of Optical Digital Subcarrier Multiplexing Systems With a Silicon Photonics Transmitter

An integrated CMOS–silicon photonics transmitter with a 112 gigabaud transmission and picojoule per bit energy efficiency

The widening application of advanced digital infrastructure requires the development of communications technologies with increased data transmission rates. However, ensuring that this can be achieved in an energy-efficient way is challenging. Here we report an integrated complementary metal–oxide–semiconductor/silicon-photonics-based transmitter in which a switching current is applied to the passive-equalization-network-guided silicon Mach–Zehnder modulator, rather than driving a standard Mach–Zehnder modulator with a traditional voltage swing. This approach allows the total electrical energy to be selectively distributed to different frequency components by choosing an appropriate inductance and near-end termination impedance values. With the approach, we achieve 112 gigabaud—112 gigabits per second on–off keying and 224 gigabit per second pulse-amplitude modulation with four levels—transmission with energy efficiencies below picojoules per bit, and without the need for signal-shaping functions in the data source. We also investigate the bit error rate for different electrical and optical power conditions at 100 gigabaud, including the electrical power consumption of the driver amplifier.

300-Gb/s/λ IM/DD Transmission Using Integrated SiP OTDM Transmitter

We fabricate an integrated silicon-photonic (SiP) 2-channel optical-time-division-multiplexing (OTDM) transmitter, which is operable with a sinusoidally modulated input light source. This SiP transmitter consists of two Mach-Zehnder modulators (MZMs), two 1×2 multimode interferometer (MMI) couplers, a time-delay line (TDL), and a thermo-optic phase shifter (TOPS). The 3-dB bandwidth of these MZMs is measured to be as large as 60 GHz. However, due to the limited bandwidths of the various components used in our experiment, the overall bandwidth of each OTDM channel is reduced to ~35 GHz. Nevertheless, by using this SiP transmitter, we could demonstrate the transmission of a 300-Gb/s OTDM pulse-amplitude modulation 8-level (PAM8) signal over 500 m of the standard single-mode fiber (SSMF). We also confirm that the fabricated SiP OTDM transmitter can be utilized even with the fabrication fluctuations of the TDL.

Multi-dimensional data transmission using inverse-designed silicon photonics and microcombs

The use of optical interconnects has burgeoned as a promising technology that can address the limits of data transfer for future high-performance silicon chips. Recent pushes to enhance optical communication have focused on developing wavelength-division multiplexing technology, and new dimensions of data transfer will be paramount to fulfill the ever-growing need for speed. Here we demonstrate an integrated multi-dimensional communication scheme that combines wavelength- and mode- multiplexing on a silicon photonic circuit. Using foundry-compatible photonic inverse design and spectrally flattened microcombs, we demonstrate a 1.12-Tb/s natively error-free data transmission throughout a silicon nanophotonic waveguide. Furthermore, we implement inverse-designed surface-normal couplers to enable multimode optical transmission between separate silicon chips throughout a multimode-matched fibre. All the inverse-designed devices comply with the process design rules for standard silicon photonic foundries. Our approach is inherently scalable to a multiplicative enhancement over the state of the art silicon photonic transmitters.

53 GBd PAM-4 fully-integrated silicon photonics transmitter with a hybrid flip-chip bonded laser

We present a fully-integrated single-lane 53 GBd PAM-4 silicon photonics (SiPh) transmitter (Tx) with a flip-chip bonded laser diode (LD). The LD is butt-coupled to a Si edge coupler including a SiO2 suspended spot-size converter. The coupled power exceeds 10 dBm with a 1 dB allowable misalignment of 2.3 µm. The RF and eye performances of the Tx are evaluated. Extinction ratio >5 dB is obtained at 3.5 Vppd voltage swing. Aided by silicon capacitors, the Tx decouples parasitic inductances leading to remarkable improvements in the eye openings and transmitter dispersion eye closure quaternary by 1.16 dB. By implementing the fully-integrated Tx with driver packaging, we successfully demonstrate 106 Gb/s real-time operation satisfying KP4-FEC threshold at -5 dBm receiver sensitivity.

Design and Realization of Multi-Channel and High-Bandwidth 2.5D Transmitter Integrated With Silicon Photonic MZM

Recently, the interconnection bandwidth of the data center is rapidly increasing. To satisfy the requirement for the high-performance data center, a 4-channel 2.5D silicon photonic transmitter is proposed and the packaging structure could increase the high-density scalability of the architecture for 1.6T/3.2T co-packaging optics (CPO) module. The electrical driver and silicon photonic Mach-Zehnder modulator (MZM) are mounted to the silicon interposer by the micro-bumps. Meanwhile, the silicon interposer is mounted to the low temperature co-fired ceramic by the solder balls. The 2.5D transmitter is assembled to the motherboard by the high-speed ball grid array (BGA) connector to make it convenient to be replaced. The electrical optimization is implemented to make the insertion loss of the whole passive link within −1.55 dB under 40 GHz, which ensures the transmitter with the socket transmit the clear simulated eye diagram at 64 Gbps PAM4 rate per channel. Moreover, the thermal evaluation is performed, which includes the heat- dissipation evaluation and the thermal-induced impact on the edge light coupling. Finally, the substrates in the 2.5D transmitter are fabricated and the transmitter is realized by the improved assembly method. By the verification of the measurement, the 2.5D transmitter we proposed could work at 64 Gbps PAM4 signal transmission rate per channel with the 6pJ/bit power consumption. Regardless of the bandwidth of the electronic integrated circuit (EIC)/MZM and the BGA connector, based on the simulation electrical bandwidth, it is potential for realizing 100 Gbps PAM4 signal transmission.

Silicon Photonic Integrated Circuits for Soliton Based Long Haul Optical Communication

We demonstrate a silicon photonic transmitter for soliton-based communications enabling the interleaving of QPSK and APSK modulated soliton pulses overlapping in both the time and frequency domains. The nonlinear Fourier transform is used to both determine adequate soliton launch conditions and facilitate nonlinear equalization at the receiver. A spectral efficiency of 0.5 b/s/Hz per polarization is reached over a 5400 km transmission distance and constitutes, to the best of our knowledge, a record for soliton transmission over such long distances. Linear and nonlinear minimum mean square error and artificial neural network-based equalizers are also experimentally benchmarked, with artificial neural networks resulting in particularly effective equalization in this system.

Dual-polarization multiplexing amorphous Si:H grating couplers for silicon photonic transmitters in the photonic BiCMOS backend of line

In this paper, we report on polarization combining two-dimensional grating couplers (2D GCs) on amorphous Si:H, fabricated in the backend of line of a photonic BiCMOS platform. The 2D GCs can be used as an interface of a hybrid silicon photonic coherent transmitter, which can be implemented on bulk Si wafers. The fabricated 2D GCs operate in the telecom C-band and show an experimental coupling efficiency of − 5 dB with a wafer variation of ± 1.2 dB. Possibilities for efficiency enhancement and improved performance stability in future design generations are outlined and extension toward O-band devices is also investigated.Graphical

Single-chip hybrid integrated silicon photonics transmitter based on passive alignment.

A single-chip hybrid integrated silicon photonics transmitter based on passive alignment flip-chip bonding technology has been demonstrated. The transmitter is developed by the hybrid integration of a C-band slotted laser with 1 mm cavity length and a Mach-Zehnder modulator with 2 mm long phase shifter. A 3 dB bandwidth of the small signal response is 16.35 GHz at 5.99 VPP superimposed with a reverse bias voltage of 2.43 V. A 25 Gbps data transmission experiment of the hybrid integrated transmitter is performed at 25°C.

A 50-Gb/s PAM-4 Silicon-Photonic Transmitter Incorporating Lumped-Segment MZM, Distributed CMOS Driver, and Integrated CDR

This article presents a 50-Gb/s optical transmitter (TX), consisting of a 40-nm distributed CMOS driver and a 180-nm silicon-photonic modulator. A lumped-segment Mach–Zehnder modulator (LS-MZM) is developed for high bandwidth (BW) four-level pulse amplitude (PAM-4) modulation. A multi-segment driver with limiting outputs is co-designed, which is distributed into each LS-MZM segment. By grouping these LS-MSM segments in a thermometer code, high-linearity modulation is realized without the need of power-hungry high-swing linear drivers. To improve the optical PAM-4 signal integrity, in-segment multiplexing along with clock phase interpolation is adopted to synchronize the electrical and optical signals across all segments. The hybrid coupling between the driver and modulator is devised to boost the BW of the high-speed data path, while a half-rate clock and data recovery (CDR) circuit is integrated to remove the accumulated jitter. Measurements show that the TX exhibits an extinction ratio (ER) of up to 9.8 dB and a 0.99 ratio of the level mismatch. A figure-of-merit (FoM) of 1.39 pJ/bit/dB corresponds to a 682-mW power, which can be further reduced by 40%, at the cost of a degraded ER of 4 dB. The PAM-4 CDR helps to achieve <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt; 10^{-12}$ </tex-math></inline-formula> BER and >0.1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{U}I_{\mathrm {pp}}$ </tex-math></inline-formula> jitter tolerance (JTOL) from 10 to 100 MHz.

Numerical Demonstration of 800 Gbps WDM Silicon Photonic Transmitter with Sub-Decibel Surface-Normal Optical Interfaces.

We propose and numerically demonstrate an 800 Gbps silicon photonic transmitter with sub-decibel surface-normal optical interfaces. The silicon photonic transmitter is composed of eight silicon Mach–Zehnder optical modulators and an interleaved AMMI WDM device. This WDM device comprises two 1 × 4 angled MMI and a Mach–Zehnder interferometer (MZI) optical interleaver with an apodized bidirectional grating which has about −0.5 dB coupling loss. Both the Mach–Zehnder electro-optical modulators and MZI optical interleaver regard the bidirectional grating coupler as vertical optical coupler and 3-dB power splitter/combiner. By importing the S-parameter matrices of all the components which have been carefully designed in simulation software, the circuit-level model of the optical transmitter can be built up. On this basis, the static and dynamic performance characterization were carried out numerically. For NRZ modulation, the optical transmitter exhibits the overall optical loss of 4.86–6.72 dB for eight wavelength channels. For PAM4 modulation, the optical loss is about 0.5 dB larger than that of NRZ modulation, which varies between 5.38–7.27 dB. From the eye diagram test results, the WDM silicon photonic transmitter can achieve single channel data transmission at 100 Gb/s NRZ data or 50 GBaud/s PAM4 symbol rate with acceptable bit error rate.

Hybrid WDM-MDM transmitter with an integrated Si modulator array and a micro-resonator comb source.

We demonstrate a multi-channel silicon photonic transmitter based on wavelength division multiplexing (WDM) and mode division multiplexing (MDM). The light source is realized by a silicon nitride (Si3N4) Kerr frequency comb and optical modulation is realized by silicon electro-optic modulators. Three wavelengths and two modes are employed to increase the optical transmission capacity. The accumulated data rate reaches 150 Gb/s. The dense integration of WDM and MDM components with a compact optical comb source opens new avenues for the future high-capacity multi-dimensional optical transmission.

Electronic–photonic convergence for silicon photonics transmitters beyond 100 Gbps on–off keying

We present design concepts for optical modulators without using any equalization or bespoke fabrication techniques. The demonstrated silicon photonics transmitter can operate at 100 Gbps OOK, while the power efficiency of the driver is 2.03 pJ/bit.

800 Gbit/s transmission over 1 km single-mode fiber using a four-channel silicon photonic transmitter

We demonstrate the optical transmission of an 800 Gbit/s ( 4 × 200 Gbit / s ) pulse amplitude modulation-4 (PAM-4) signal and a 480 Gbit/s ( 4 × 120 Gbit / s ) on–off-keying (OOK) signal by using a high-bandwidth (BW) silicon photonic (SiP) transmitter with the aid of digital signal processing (DSP). In this transmitter, a four-channel SiP modulator chip is co-packaged with a four-channel driver chip, with a measured 3 dB BW of 40 GHz. DSP is applied in both the transmitter and receiver sides for pre-/post-compensation and bit error rate (BER) calculation. Back-to-back (B2B) BERs of the PAM-4 signal and OOK signal are first measured for each channel of the transmitter with respect to a variety of data rates. Similar BER performance of four channels shows good uniformity of the transmitter between different channels. The BER penalty of the PAM-4 and OOK signals for 500 m and 1 km standard single-mode fiber (SSMF) transmission is then experimentally tested by using one channel of the transmitter. For a 200 Gbit/s PAM-4 signal, the BER is below the hard-decision forward error correction (HD-FEC) threshold for B2B and below the soft-decision FEC (SD-FEC) threshold after 1 km transmission. For a 120 Gbit/s OOK signal, the BER is below SD-FEC threshold for B2B. After 500 m and 1 km transmission, the data rate of the OOK signal shrinks to 119 Gbit/s and 118 Gbit/s with the SD-FEC threshold, respectively. Finally, the 800 Gbit/s PAM-4 signal with 1 km transmission is achieved with the BER of all four channels below the SD-FEC threshold.

1.12-Tbit/s PAM-4 Enabled by a Silicon Photonic Transmitter Bridged With a 7-Channel MCF

We demonstrate a high-capacity and ultra-compact silicon photonic transmitter directly coupled to a 7-channel multicore fiber (MCF). The integrated transmitter contains seven GeSi electro-absorption modulators (EAMs) connected with the perfectly vertical grating coupler (PVGC) array. A high port density for spatial-division multiplexing (SDM) is thus enabled by the out-of-plane coupling while not requiring angled polishing of the MCF. Relying on four-level pulse amplitude modulation (PAM-4) and digital signal processing (DSP), each of the EAMs can support a data rate of 160 Gbit/s in the back-to-back system. The obtained bit-error-rate (BER) is below the low-latency 7% hard-decision forward-error-correct (HD-FEC) coding limit. The integrated transmitter has a total data-rate-capacity of 1.12 Tbit/s over the seven spatial channels and a compact footprint of 1.8 mm $\times0.45$ mm. BER performance of the optimum spatial channel is evaluated at different wavelengths, revealing its potential for possible wavelength-division multiplexing (WDM) by the on-chip wavelength (de)multiplexers in the future.

Design and Performance Evaluation of Multi-Gb/s Silicon Photonics Transmitters for High Energy Physics

Optical links are rapidly becoming pervasive in the readout chains of particle physics detector systems. Silicon photonics (SiPh) stands as an attractive candidate to sustain the radiation levels foreseen in the next-generation experiments, while guaranteeing, at the same time, multi-Gb/s and energy-efficient data transmission. Integrated electronic drivers are needed to enable SiPh modulators’ deployment in compact on-detector front-end modules. A current-mode logic-based driver harnessing a pseudo-differential output stage is proposed in this work to drive different types of SiPh devices by means of the same circuit topology. The proposed driver, realized in a 65 nm bulk technology and already tested to behave properly up to an 8 MGy total ionizing dose, is hybridly integrated in this work with a lumped-element Mach–Zehnder modulator (MZM) and a ring modulator (RM), both fabricated in a 130 nm silicon-on-insulator (SOI) process. Bit-error-rate (BER) performances confirm the applicability of the selected architecture to either differential and single-ended loads. A 5 Gb/s data rate, in line with the current high energy physics requirements, is achieved in the RM case, while a packaging-related performance degradation is captured in the MZM-based system, confirming the importance of interconnection modeling.

A 50-Gb/s PAM4 Si-Photonic Transmitter With Digital-Assisted Distributed Driver and Integrated CDR in 40-nm CMOS

A 50-Gb/s four-level pulse-amplitude modulation (PAM4) silicon photonic transmitter is presented, which is composed of a 40-nm bulk CMOS driver hybrid integrated with a 180-nm silicon-on-insulator (SOI) CMOS Mach–Zehnder modulator (MZM). To recover and demodulate 50-Gb/s PAM4 data into dual-25-Gb/s nonreturn to zero (NRZ) streams for the co-designed MZM digital-analog converter (DAC), a reference-less clock and data recovery (CDR) is integrated, and to achieve high swing and high speed, the driver is made in a distributed amplifier (DA), employing push–pull cells that are grouped in three segments. A digital-assisted distributed driver (DADD) that replaces the input T-line by segmented 2:1 multiplexers and buffers is, thus, proposed. Precise time gating in each segment allows for velocity match in both the DA and optical DAC, as well as the in-segment pre-emphasis without power-hungry analog delay stages. Measurement results show that the driver and CDR achieve 4-VPP differential swing, 1.19-ps rms jitter, and 1.34-W power consumption at 50 Gb/s. An optical transmitter is demonstrated by wire-bonding the driver to the MZM DAC, achieving 50-Gb/s PAM4 output with 6.35-ps rms jitter and improved linearity.

Hybrid multi-chip assembly of optical communication engines by in situ 3D nano-lithography

Three-dimensional (3D) nano-printing of freeform optical waveguides, also referred to as photonic wire bonding, allows for efficient coupling between photonic chips and can greatly simplify optical system assembly. As a key advantage, the shape and the trajectory of photonic wire bonds can be adapted to the mode-field profiles and the positions of the chips, thereby offering an attractive alternative to conventional optical assembly techniques that rely on technically complex and costly high-precision alignment. However, while the fundamental advantages of the photonic wire bonding concept have been shown in proof-of-concept experiments, it has so far been unclear whether the technique can also be leveraged for practically relevant use cases with stringent reproducibility and reliability requirements. In this paper, we demonstrate optical communication engines that rely on photonic wire bonding for connecting arrays of silicon photonic modulators to InP lasers and single-mode fibres. In a first experiment, we show an eight-channel transmitter offering an aggregate line rate of 448 Gbit/s by low-complexity intensity modulation. A second experiment is dedicated to a four-channel coherent transmitter, operating at a net data rate of 732.7 Gbit/s – a record for coherent silicon photonic transmitters with co-packaged lasers. Using dedicated test chips, we further demonstrate automated mass production of photonic wire bonds with insertion losses of (0.7 ± 0.15) dB, and we show their resilience in environmental-stability tests and at high optical power. These results might form the basis for simplified assembly of advanced photonic multi-chip systems that combine the distinct advantages of different integration platforms.