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Chaotic emission of a semiconductor laser is investigated through propagation over a fiber for achieving broadening of the bandwidth and suppression of the time-delay signature (TDS). Subject to delayed optical feedback, the laser first generates chaos with a limited bandwidth and an undesirable TDS. The laser emission is then delivered over a standard single-mode fiber for experiencing self-phase modulation, together with anomalous group-velocity dispersion, which leads to the broadening of the optical bandwidth and suppression of the TDS in the intensity signal. The effects are enhanced as the input power launched to the fiber increases. By experimentally launching up to 340 mW into a 20 km fiber, the TDS is suppressed by 10 times to below 0.04, while the bandwidth is broadened by six times to above 100 GHz. The improvement of the chaotic signal is potentially useful in random bit generation and range detection applications.
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http://dx.doi.org/10.1364/OL.43.004751 | DOI Listing |
Light Sci Appl
September 2025
John A. Paulson School of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, MA, 02138, USA.
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View Article and Find Full Text PDFIn this paper, we propose and numerically investigate a long-distance coherent secure communication network scheme based on a synchronized chaotic semiconductor laser. The central driving laser (CDL) with optical feedback can achieve chaotic signals with enhanced bandwidth and suppressed time delay signature through a dispersion component and a phase modulator, and high-quality chaos synchronization and communication between two arbitrary response lasers (RLs, legal receivers) can be guaranteed due to the identical injection from CDL. After adopting coherent detection and the modified constant modulus algorithm (MCMA) to compensate for the fiber transmission impairments, including chromatic dispersion and nonlinear effects, we demonstrate a bidirectional 64 Gb/s 16-quadrature amplitude modulation (16-QAM) message transmission over 800 km with a bit-error rate (BER) below the hard-decision forward-error-correction threshold of 3.
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