We demonstrate a novel semi-deterministic SiP O-Band device, capable of compensating any ELS SOP from 1km distances, with an IL of 1.9-dB and PDL of 0.77-dB, enabling the ubiquitous use of ELS in CPO transceivers.

A frequency-comb laser is used as an external laser source (ELS) to enable a scalable co-packaged optics solution for radio access networks. A polarization-compensating device allows the remote operation of an O-band, 100-GHz spaced comb laser, where the impact of fiber nonlinearities and polarization-mode dispersion is studied via simulations and experiments. Finally, with the comb laser separated by 2 km of single-mode fiber (SMF) from a silicon photonic transmitter, we demonstrate the compensation of an arbitrary state of polarization, and emulate an 11-channel WDM transmission system achieving net aggregate rates of 751 Gbps (OOK) and 1.69 Tbps (PAM4) under the KP4-FEC and the SD-FEC 25% thresholds, respectively.

A frequency-comb laser is isolated by 2 km of SMF from a SiP transmitter that can compensate for any SOP, while demonstrating an 11-wavelength WDM transmission producing net rates of 825 Gbps (OOK) and 1.69 Tbps (PAM4) under HD-FEC and SD-FEC 25%, respectively. (c) 2025 The Author(s)

We demonstrate a SiP O-band transmitter, and autonomously compensating for any injected laser state of polarization (SOP), achieving net 105 and 154 Gbps PAM4 and PAM8 transmission below the Hard-Decision and Soft-Decision FEC thresholds, respectively, with the carrier laser remotely connected to the transmitter over 1 km of single-mode fiber. To enable autonomy, a feedback gradient descent algorithm is implemented, with the starting point determined by the polarimeter, to mitigate the polarization-dependent loss on the device. Additionally, the wavelength dependence and performance of the transmitter are experimentally determined to increase the effective net rate. An emulated WDM transmission was then performed at the 1304.58 nm and 1309.14 nm wavelengths, achieving net 224 and 307 Gbps OOK and PAM4 performance, below the Hard-Decision and Soft-Decision forward error correction thresholds, respectively.

We report the first O-band coherent transmission using a comb laser and a silicon photonics modulator. We achieved greater than 8.5 Tbps using 19 lines over 10km at 56 Gbaud DP-32QAM.

Co-packaged optics (CPO) is an emerging technology providing optical interconnections with a bandwidth density of the order of Terabit/s per square millimeter. All current development and standardization efforts focus on data centers, to connect very high-capacity switches while improving energy efficiency and footprint compared to designs based on front-panel pluggable optics. We think CPO will have an important role also in 6G networks, to meet the demand for high capacity at low energy consumption. This paper illustrates use cases and requirements for CPO natively designed for radio applications and outlines standardization and industrialization paths

There is a continuous need to scale optical communication networks' capacity to cope with the exponential growth of data traffic. Silicon photonics (SiP) retains significant potential as a platform for optical transceivers due to its CMOS compatibility, despite its limited electro-optic bandwidth and high driving voltage requirements. Here we present the design and characterization of two single-segment C-band SiP in-phase quadrature modulators (IQM) that differ in the phase shifter length, and we analyze the design tradeoffs based on their transmission performance. The large-signal transmission experiments indicate that the long IQM supports higher data transmission rates, which has 36 GHz 6-dB bandwidth and 10.5 V DC Vπ under 1 V reverse bias. With all-electronic equalization and on a single polarization, we transmit net 413 Gbps (95 Gbaud 32QAM) over 80 km of standard single-mode fiber (SSMF) under the 14.8% overhead concatenated forward error correction (C-FEC) BER threshold of 1.25 × 10 −2 . Using dual-polarization (DP) emulation and lookup table-based non-linear pre-distortion (NLPD), we demonstrate the transmission of 95 Gbaud DP-32QAM and 115 Gbaud DP-16QAM over 80 km of SSMF below the C-FEC BER threshold, corresponding to net rates of 827 Gbps and 800 Gbps, respectively. Moreover, we transmit 105 Gbaud DP-64QAM over 80 km below the 25% overhead soft-decision (SD) FEC BER threshold of 5 × 10 −2 ; featuring the first demonstration of net 1 Tbps transmission using an all-silicon IQM. Employing only electronic equalization and single-segment IQM preserves the conventional architecture of coherent networks and transceivers, and highlights the potential of SiP as a platform for next-generation 800G applications.

Co-packaged optics is an emerging technology with the potential to play a key role in 6G radio-access networks, due to its ability to enable high capacity at low energy consumption. Creating a version of the technology that is suitable for radio applications will, however, require some dedicated development to address network characteristics.

We propose two low-complexity digital signal processing (DSP) techniques to improve the system performance of digital subcarrier multiplexing (DSCM) optical transmission system with a silicon photonics transmitter. We first analyze the impacts of various transmitter parameters on the system performance of the single carrier system versus the DSCM system. We show quantitatively that the DSCM system suffers from a high peak-to-average power ratio (PAPR) and nonlinear transfer functions that cannot be easily compensated for. Furthermore, using a high-driving-voltage silicon photonics modulator exacerbates this penalty at the transmitter. To combat the performance degradation caused by nonideal transmitters, we propose and demonstrate the functionality of an encoding scheme based on the fast Fourier transform (FFT) to decrease the PAPR of the transmitted DSCM signals. Then a simple and effective pre-mapping technique is proposed to compensate for the nonlinearity from the transmitter. After developing the theory of our proposed approach, both DSP blocks are verified with coherent optical transmission simulations and experiments. Using a 64 GBd 4-bit/s/Hz DSCM signal containing 8 subcarriers transmitted over 43.2 km of standard single-mode fiber (SSMF), the FFT encoding achieves a gain of 3.458 dB in terms of link loss, and the pre-mapping achieves a gain of 0.486 dB when compared to the raw DSCM system, at the HD-FEC bit error rate (BER) threshold of 3.8e-3. We also tested the performance of the system when the two techniques are combined. We found that this led to a power budget increase of 4.159 dB at the HD-FEC threshold. Since the total gain is more than the addition of the two gains from each DSP block, there is a gain enhancement effect between the two proposed algorithms that generates extra gain when implemented together. The proposed transmitter algorithms and the overall schematic is favorable to the implementation of DSCM systems when using silicon-photonics-modulator-based transmitters specifically and coherent transmitters generally.

We achieve net 1 Tbps (line-rate 1.26 Tbps) transmission using a single-segment travelling-wave SiP IQ modulator at 105 Gbaud DP-64QAM below the 25% SD-FEC-threshold over 80 km of SSMF with all-electronic equalization and non-linear pre-distortion.

We demonstrate the transmission of 100 GBaud 64QAM achieving a BER below the 25% OH SD-FEC threshold using a single segment all-silicon IQ modulator; featuring a throughput of 600 (net 480) Gb/s.

We propose a 1310/1550 nm wavelength diplexer on a 220-nm silicon-on-insulator (SOI) platform. The device is based on a compact two-mode interference (TMI) coupler enabled by a subwavelength grating (SWG) slot. The ideal beat length ratio of 2:1 is achieved with the transverse magnetic (TM) mode by fine-tuning the SWG slot parameters, resulting in a TMI length of only 37 µm. We reveal that the key to high extinction ratio (ER) is the careful design of the tapers, and the device achieves high ERs of 28.05/42.54 dB at 1310/1550 nm with simulation. The measured bandwidths for ER $>$ 15 dB are 82 nm and 56 nm at O- and C-band. Moreover, the design guarantees large calculated 1-dB-insertion-loss (IL) bandwidths of 192/123 nm at 1310/1550 nm. To the best of our knowledge, this is the first experimental demonstration of a high-performance compact silicon 1310/1550 nm diplexer based on a TMI coupler.

We propose a constellation distortion approach that mitigates equalization-enhanced noise in coherent systems. Experimental data show a 0.5 dB OSNR improvement, allowing the transmission of net 843 Gbps 32QAM using an all-silicon modulator below HD-FEC.

The high thermal sensitivity of the Silicon Photonics (SiP) platform compromises the performance of variant devices and increases the power consumption to stabilize the temperature. To address this issue, we demonstrate a CMOS-compatible and temperature insensitive $1\times 4$ C-band wavelength division (de-)multiplexer on the 220-nm-thick silicon-on-insulator platform. The (de-)multiplexer design is based on cascading Mach-Zehnder interferometers (MZIs). The waveguide widths of the MZI delay lines are matched to decrease the overall thermo-optic coefficient (TOC). For comparison, an MZI-based (de-)multiplexer with uniform delay lines is also fabricated on the same chip. The transmission spectra of the proposed and reference devices are measured when the wavelength is swept from 1500 nm to 1600 nm and the temperature is varied from 293.15 K to 323.15 K. The measured results show that the TOCs of the proposed and reference device are 4.8 pm/K and 85 pm/K, respectively. This power-efficient multiplexer with high integration density is promising for data center applications.

We propose an all-silicon design of a multi-band transverse-magnetic-pass (TM-pass) polarizer. The device is based on one-dimensional gratings that work under different regimes that depend on the polarization. With a tapered structure, it is revealed that the operation bandwidth can be extended by multiplexing the diffraction in O-band and the reflection in S-, C-, and L-bands for the transverse-electric (TE) mode. By simulation, we achieve a 343 nm device bandwidth with insertion loss (IL) < 0.4 dB and polarization extinction ratio (PER) > 20 dB. The operation wavelength range covers commonly-used optical telecommunication bands including the O-, S-, C-, and L- bands. Experimental results also show IL < 1.6 dB and PER > 20 dB from 1265 nm to 1360 nm corresponding to the O-band, and from 1500 nm to 1617 nm that corresponds to the C-band. The device is a single-etched design on the standard 220 nm silicon-on-insulator (SOI) with silicon oxide cladding. Such a simple and compatible design paves the way for developing practical multi-band silicon photonic integrated circuits.

We present a systematic comparison of PAM-2 (NRZ), Duobinary-PAM-2, PAM-4, and Duobinary-PAM-4 (duo-quaternary) signaling in the context of short-reach photonic communications systems using a Mach–Zehnder modulator as transmitter. The effect on system performance with a relaxed and constrained system’s opto-electronic bandwidth is analyzed for bit rates ranging from 20 to 116 Gb/s. In contrast to previous analyses, our approach employs the same experimental and simulation conditions for all modulation formats. Consequently, we were able to confidently determine the performance limits of each format for particular values of bit rate, system bandwidth, transmitter chirp, and fiber dispersion. We demonstrate that Duobinary-PAM-4 is a good signaling choice only for bandwidth-limited systems operating at relatively high speed. Otherwise, PAM-4 represents a more sensible choice. Moreover, our analysis put forward the existence of transition points: specific bit rate values where the BER versus bit rate curves for two different formats cross each other. They indicate the bit rate values where, for specific system conditions, switching from one modulation to another guarantees optimum performance. Their existence naturally led to the proposal of a format-selective transceiver, a component that, according to network conditions, operates with the most adequate modulation format. Since all analyzed modulations share similar implementation details, signaling switching is achieved by simply changing the sampling point and threshold count at the receiver, bringing flexibility to IM/DD-based optical networks.

We report 108 Gb/s Duo-Binary PAM-8 (DB-PAM-8) transmission using direct-detection aided by Volterra equalizer. The bit-error-rate (BER) performance of the DB-PAM-8 signal has been evaluated through error counting by varying the bit rate, received optical power, and reach. The experimental results suggest that up to 108, 102, and 84 Gb/s signals can be propagated in back-to-back (B2B), and over 10, and 20 km of standard single-mode fiber (SMF), respectively, below the low-density parity-check forward error correction (LDPC-FEC) threshold. Furthermore, we derive a probabilistic model of the BER for multilevel DB-PAM-M signaling that is verified using our measurements. The model of this important performance metric turned out to be accurate enough, especially at low BER values, where its use is more convenient.

We demonstrate 224 Gb/s net rate dual-polarization PAM4 signal transmission over 10 km of SMF in the C-band below the HD-FEC threshold of 3.8×10-3, using Stokes vector receiver and an integrated ring resonator based optical dispersion compensator.

We propose an optimization scheme for the distribution of probabilistically shaped signals in practical non-AWGN channels based on a neural network and genetic algorithm. The optimized input distribution enables 23.5% higher throughput than the Maxwell-Boltzmann distribution in a short reach channel with a SiP transmitter.

We report a broadband 2×2 adiabatic 3-dB coupler with an inversely-tapered mode-evolution region for the silicon-on-insulator platform. Measured imbalance better than ± 0.23 dB is achieved over a 100 nm bandwidth centered at 1550 nm.