Microresonator solitons for massively parallel coherent optical communications (1610.01484v4)

Abstract: Optical solitons are waveforms that preserve their shape while propagating, relying on a balance of dispersion and nonlinearity. Soliton-based data transmission schemes were investigated in the 1980s, promising to overcome the limitations imposed by dispersion of optical fibers. These approaches, however, were eventually abandoned in favor of wavelength-division multiplexing (WDM) schemes that are easier to implement and offer improved scalability to higher data rates. Here, we show that solitons may experience a comeback in optical communications, this time not as a competitor, but as a key element of massively parallel WDM. Instead of encoding data on the soliton itself, we exploit continuously circulating dissipative Kerr solitons (DKS) in a microresonator. DKS are generated in an integrated silicon nitride microresonator by four-photon interactions mediated by Kerr nonlinearity, leading to low-noise, spectrally smooth and broadband optical frequency combs. In our experiments, we use two interleaved soliton Kerr combs to transmit a data stream of more than 50Tbit/s on a total of 179 individual optical carriers that span the entire telecommunication C and L bands. Equally important, we demonstrate coherent detection of a WDM data stream by using a pair of microresonator Kerr soliton combs - one as a multi-wavelength light source at the transmitter, and another one as a corresponding local oscillator (LO) at the receiver. This approach exploits the scalability advantages of microresonator soliton comb sources for massively parallel optical communications both at the transmitter and receiver side. Taken together, the results prove the significant potential of these sources to replace arrays of continuous-wave lasers in high-speed communications.

• The paper demonstrates the use of dissipative Kerr solitons in microresonators to generate stable, broadband frequency combs that enable terabit-scale data transmission.
• The research utilizes integrated silicon nitride microresonators to produce over 179 optical carriers, achieving an aggregated line rate exceeding 55.0 Tbit/s using coherent WDM.
• The study shows that DKS combs can function as multi-wavelength local oscillators with minimal OSNR penalties, paving the way for energy-efficient, high-capacity optical networks.

Microresonator Solitons for Massively Parallel Coherent Optical Communications

This paper presents a compelling exploration into the utilization of dissipative Kerr solitons (DKS) in microresonators for optical communications, aiming to harness the inherent capabilities of these structures to advance coherent wavelength-division multiplexing (WDM). Through in-depth experimentation, the research elucidates how microresonator-based Kerr combs can be transformative for high-speed optical transmission systems, emphasizing operations at terabit rates across telecommunication bands.

The researchers delve into the generation of DKS in integrated silicon nitride microresonators, showcasing their capacity to produce stable, broadband optical frequency combs. These combs feature over 179 optical carriers that can transmit data streams surpassing 50 Tbit/s across the full spectrum of telecommunication C and L bands, and their applicability as both light sources and local oscillators (LO) in transmission and reception processes further accentuates their efficiency. Strong numerical results are evident in this paper: achieving an aggregated line rate exceeding 55.0 Tbit/s with interleaved soliton Kerr combs. This stands as a significant benchmark in optical coherent communication, comparable to transmission capacities traditionally reliant on more than 200 discrete DFB lasers.

Two critical experiments highlight the potential of DKS combs. In the first, a demonstrator system transmits data using 94 individual carriers within the telecommunications C and L bands, achieving a line rate of 30.1 Tbit/s through 16QAM modulation. In the second experiment, interleaving two soliton comb generators not only expands the carrier field to 179 but also amplifies the line rate to 55.0 Tbit/s over 75 km of standard single-mode optical fiber, representing a significant step forward for chip-scale frequency comb applications.

The paper further investigates the application of DKS frequency combs as multi-wavelength LOs at the receiving end. Conducting a series of controlled experiments, the paper records nearly symmetrical transmission performance for DKS combs when juxtaposed with high-quality benchtop external-cavity lasers (ECLs), saw negligible additional OSNR penalties due to the comb sources, indicating their strong potential in minimizing energy consumption while maintaining high signal fidelity.

From the perspective of fabrication, the authors discuss the reproducibility challenges and potential enhancements in Q-factors using contemporary large-scale fabrication methods to ensure high-yield and performance consistency across multiple devices. The achieved improvements have implications not only theoretically for understanding optical soliton dynamics in micro-scales but also practically in suggesting an optimized path towards integrated photonics solutions suitable for high-capacity data centers.

Finally, the implications of these findings suggest that DKS frequency combs could significantly impact the scalability of data center interconnects and other high-performance optical networks. Their potential integration with advanced spatial multiplexing platforms and other silicon photonics technologies offers a glimpse into the next generation of optical communications moving towards petabit-scale transceivers.

In summary, this research highlights the transformative role DKS microresonators could play in high-bandwidth optical communications. Theoretical insights, combined with empirical data, underscore the feasibility of leveraging chip-scale soliton combs for developing robust and ultra-efficient communication infrastructures, with promising prospects in both data-intensive environments and future optical networking paradigms.