Optical Communication Systems and Signal Processing

Optical communication systems form the backbone of modern high-capacity networks, leveraging light propagation in fibres to transmit data over vast distances with minimal loss. Central to their performance is signal processing, which encompasses modulation, detection and compensation algorithms to mitigate dispersion, nonlinear effects and noise. Coherent techniques enable the recovery of both amplitude and phase information, unlocking advanced modulation formats for greater spectral efficiency. Meanwhile, direct-detection schemes offer cost-effective solutions for short-reach links, balancing simplicity against performance. Digital signal processing (DSP) underpins impairment compensation, from chromatic dispersion equalisation to carrier phase recovery, and forms the basis of emerging paradigms such as learnable DSP frameworks. As demands on data throughput continue to escalate—driven by cloud computing, 5G and beyond—the integration of machine learning, digital twins and autonomous control promises to enhance network agility, reliability and energy efficiency on a global scale.

Research from Nature Portfolio

Recent studies have demonstrated a residual carrier modulation scheme that tackles laser phase noise in cost-sensitive coherent links. By continuously tracking phase fluctuations via a residual optical carrier rather than discrete pilots, researchers achieved a 41 % bitrate improvement when transmitting a probabilistic-shaped 256-QAM signal at 1 Tb/s using a 3 MHz DFB laser. This approach supports low-linewidth devices in short-reach coherent optical communications and sets a new benchmark for phase recovery in high-order modulation systems.

Research from all publishers

A learnable digital signal processing framework has been proposed to optimise linear compensation in fibre transmission. By treating the entire DSP chain as a deep learning model and tuning module parameters via backpropagation, this method achieved a 1.21 dB gain in Q-factor for 400 Gb/s signals over 1 600 km, while halving computational complexity compared to conventional designs.

A Bayesian digital twin approach has been developed for autonomous control of optical power evolution in networks. By constructing data-efficient models of optical amplifiers, the method reduces training data requirements by up to 80 % and allows rapid convergence to target gain profiles, paving the way for self-driving optical networks.

A coherent receiver based on the Kramers–Kronig relation has revived direct-detection schemes for inter-data-centre links. Transmitting a continuous-wave tone alongside the data signal enables digital compensation of linear impairments and enhances spectral and energy efficiency, offering a cost-effective alternative to full coherent receivers.

Optical Communication Systems and Signal Processing publication trend

The graph below shows the total number of articles in optical communication systems and signal processing across all publications each year (not limited to Nature Index journals).

Technical terms

Coherent detection: A method that recovers both the amplitude and phase of an optical signal by mixing it with a local oscillator, enabling advanced modulation formats.

Digital signal processing (DSP): Algorithms implemented in electronics to compensate transmission impairments such as dispersion, nonlinear phase noise and polarization effects.

Quadrature amplitude modulation (QAM): A modulation format that encodes data onto two orthogonal signal components, offering high spectral efficiency.

Chromatic dispersion: The spreading of optical pulses in a fibre due to wavelength-dependent speed, which must be equalised digitally or optically.

Carrier phase recovery: A signal processing technique to estimate and correct phase noise arising from laser linewidth and transmission impairments.

Digital twin: A virtual model of a physical system (such as an optical amplifier) that enables data-driven control and optimisation.

References

1. Learnable digital signal processing: a new benchmark of linearity compensation for optical fiber communications. Light: Science & Applications (2024).
2. Overcoming laser phase noise for low-cost coherent optical communication. Nature Communications (2024).
3. Digital twin modeling and controlling of optical power evolution enabling autonomous-driving optical networks: a Bayesian approach. Advanced Photonics (2024).
4. Kramers–Kronig coherent receiver. Optica (2016).