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Amol Choudhary

Publications and source records attributed to Amol Choudhary.

4 recordsLinked to original sources
arXiv2023

Transformer-based Nonlinear Equalization for DP-16QAM Coherent Optical Communication Systems

Compensating for nonlinear effects using digital signal processing (DSP) is complex and computationally expensive in long-haul optical communication systems due to intractable interactions between Kerr nonlinearity, chromatic dispersion (CD), and amplified spontaneous emission (ASE) noise from inline amplifiers. The application of machine learning architectures has demonstrated promising advancements in enhancing transmission performance through the mitigation of fiber nonlinear effects. In this paper, we apply a Transformer-based model to dual-polarisation (DP)-16QAM coherent optical communication systems. We test the performance of the proposed model for different values of fiber lengths and launched optical powers and show improved performance compared to the state-of-the-art digital backpropagation (DBP) algorithm, fully connected neural network (FCNN) and bidirectional long short term memory (BiLSTM) architecture.

eess.SP↗
arXiv2019

Brillouin-based phase shifter in a silicon waveguide

Integrated silicon microwave photonics offers great potential in microwave phase shifter elements, and promises compact and scalable multi-element chips that are free from electromagnetic interference. Stimulated Brillouin scattering, which was recently demonstrated in silicon, is a particularly powerful approach to induce a phase shift due to its inherent flexibility, offering an optically controllable and selective phase shift. However, to date, only moderate amounts of Brillouin gain has been achieved and theoretically this would restrict the phase shift to a few tens of degrees, significantly less than the required 360 degrees. Here, we overcome this limitation with a phase enhancement method using RF interference, showing a 360 degrees broadband phase shifter based on Brillouin scattering in a suspended silicon waveguide. We achieve a full 360 degrees phase-shift over a bandwidth of 15 GHz using a phase enhancement factor of 25, thereby enabling practical broadband Brillouin phase shifter for beam forming and other applications.

physics.optics↗
arXiv2018

Chip-based Brillouin processing for carrier recovery in coherent optical communications

Modern fiber-optic coherent communications employ advanced spectrally-efficient modulation formats that require sophisticated narrow linewidth local oscillators (LOs) and complex digital signal processing (DSP). Here, we establish a novel approach to carrier recovery harnessing large-gain stimulated Brillouin scattering (SBS) on a photonic chip for up to 116.82 Gbit/sec self-coherent optical signals, eliminating the need for a separate LO. In contrast to SBS processing on-fiber, our solution provides phase and polarization stability while the narrow SBS linewidth allows for a record-breaking small guardband of ~265 MHz, resulting in higher spectral-efficiency than benchmark self-coherent schemes. This approach reveals comparable performance to state-of-the-art coherent optical receivers without requiring advanced DSP. Our demonstration develops a low-noise and frequency-preserving filter that synchronously regenerates a low-power narrowband optical tone that could relax the requirements on very-high-order modulation signaling and be useful in long-baseline interferometry for precision optical timing or reconstructing a reference tone for quantum-state measurements.

physics.app-ph↗