Coherent Optical Communication Systems Using Frequency Combs

Coherent optical communication systems employ stable phase and amplitude detection to transmit information over optical fibre with high spectral efficiency. Frequency combs—light sources emitting a series of discrete, equally spaced spectral lines—offer a compact substitute for multiple lasers in wavelength-division multiplexing. By harnessing nonlinear microresonator or parametric technologies, these comb generators deliver phase-locked carriers across broad bands, enabling parallel data channels and coherent superchannels with simplified transmitter and receiver architectures. Advances in soliton microcombs, electro-optic combs and parametric combs have driven improvements in line power uniformity, phase noise and integration on silicon platforms. Such systems promise to meet ever-growing demands in data-centre interconnects, long-haul backbone links and microwave photonics, while reducing cost, power consumption and digital signal processing overhead through shared carrier coherence and integrated dispersion compensation.

Research from Nature Portfolio

Recent studies have demonstrated the integration of microcomb sources with silicon photonic engines to form compact, chip-scale systems. One work combined an aluminium-gallium-arsenide-on-insulator microcomb with silicon photonic circuits to realise a two-terabit-per-second pulse-amplitude modulation link and a reconfigurable microwave photonic filter on a single chip, marking a key step towards fully integrated photonic systems. Another investigation introduced coherence-cloned dissipative Kerr soliton microcombs, where the receiver regenerates a microcomb matching the transmitter’s frequency and phase, yielding terabit-scale coherent interconnects with drastically simplified digital and optical compensation. Foundational research has also shown that soliton-crystal microcombs on chip can support ultra-dense transmission over standard fibre, achieving line rates exceeding 40 terabits per second across the C-band with high spectral efficiency and stable operation.

Coherent Optical Communication Systems Using Frequency Combs publication trend

The graph below shows the total number of articles in coherent optical communication systems using frequency combs across all publications each year (not limited to Nature Index journals).

Technical terms

Coherent optical communication: Transmission method using phase and amplitude detection to improve spectral efficiency.

Frequency comb: Light source emitting multiple, equally spaced, phase-locked spectral lines from a single oscillator.

Microresonator: Compact optical cavity that generates frequency combs through nonlinear effects in a small footprint.

Soliton microcomb: Stable pulse train produced in a microresonator via the balance of dispersion and Kerr nonlinearity.

Kerr effect: Nonlinear refractive index change in a medium induced by intense light, enabling comb generation.

Wavelength-division multiplexing (WDM): Technique that transmits multiple data channels on different wavelengths simultaneously.

Optical signal-to-noise ratio (OSNR): Measure of signal quality comparing signal power to noise power in an optical channel.

Forward error correction (FEC): Technique that adds redundancy to data to enable error detection and correction without retransmission.

Digital signal processing (DSP): Use of algorithms to compensate impairments and recover data in coherent receivers.

References

1. Microcomb-driven silicon photonic systems. Nature (2022).
2. Coherent optical communications using coherence-cloned Kerr soliton microcombs. Nature Communications (2022).
3. Ultra-dense optical data transmission over standard fibre with a single chip source. Nature Communications (2020).
4. High-speed data transmission over a microresonator frequency comb with dispersion compensation for augmented data rates and reach. Nanophotonics (2024).
5. On the design of low phase noise and flat spectrum optical parametric frequency comb. APL Photonics (2023).
6. Dissipative Kerr soliton microcombs for FEC-free optical communications over 100 channels.. Optics Express (2022).