{"ID":2827237,"CreatedAt":"2026-06-01T04:54:23.091178241Z","UpdatedAt":"2026-06-01T04:54:23.091178241Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2512.17890","arxiv_id":"2512.17890","title":"Spectro-temporal unitary transformations for coherent modulation: design trade-offs and practical considerations","abstract":"This paper analyzes the performance of spectro-temporal unitary transforms for coherent optical modulation. Unlike conventional IQ modulation, such transforms are based on a cascade of phase modulators and dispersive elements, so are theoretically lossless and not limited by the bandwidth of the constituent modulators. We analyse the performance limits and design trade-offs of this scheme: estimating how the number of stages, amount of dispersion, modulator bandwidth, symbol block length and electrical signal power impacts the achievable signal-to-distortion ratio (SDR). Importantly, we show that high (\u003e30 dB) SDRs suitable for modern \u003e200 GBd class coherent optical communications are achievable with a low (\u003c6) number of stages and reasonable parameters for driver power, modulator bandwidth and on-chip dispersion. Finally we address the SDR penalties associated with potential phase, amplitude, or dispersion errors, and limited DAC resolution.","short_abstract":"This paper analyzes the performance of spectro-temporal unitary transforms for coherent optical modulation. Unlike conventional IQ modulation, such transforms are based on a cascade of phase modulators and dispersive elements, so are theoretically lossless and not limited by the bandwidth of the constituent modulators....","url_abs":"https://arxiv.org/abs/2512.17890","url_pdf":"https://arxiv.org/pdf/2512.17890v2","authors":"[\"Callum Deakin\",\"Xi Chen\"]","published":"2025-12-19T18:46:24Z","proceeding":"physics.optics","tasks":"[\"physics.optics\",\"eess.SP\"]","methods":"[]","has_code":false}