Current Issue : January-March Volume : 2025 Issue Number : 1 Articles : 4 Articles
In long-haul WDM (wavelength division multiplexing) optical communication systems utilizing the DP-16QAM modulation scheme, traditional methods for removing chaos have exhibited poor performance, resulting in a high bit error rate of 10−2 between the original signal and the removed chaos signal. To address this issue, we propose DeepChaos+, a machine learning-based approach for chaos removal in WDM transmission systems. Our framework comprises two key points: (1) DeepChaos+ automatically generates a dataset that accurately reflects the features of the original signals in the communication system, which eliminates the need for time-consuming data simulation, streamlining the process significantly; (2) it allows for the training of a lightweight model that provides fast prediction times while maintaining high accuracy. This allows for both efficient and reliable signal reconstruction. Through extensive experiments, we demonstrate that DeepChaos+ achieves accurate reconstruction of the original signal with a significantly reduced bit error rate of approximately 10−5. Additionally, DeepChaos+ exhibits high efficiency in terms of processing time, facilitating fast and reliable signal reconstruction. Our results underscore the effectiveness of DeepChaos+ in removing chaos from WDM transmission systems. By enhancing the reliability and efficiency of chaotic secure channels in optical fiber communication systems, DeepChaos+ holds the potential to improve data transmission in high-speed networks....
This article proposes and experimentally validates a distributed temperature alarm system based on carbon dioxide (CO2)-filled 18 m side air-holes fiber (SAHF), interrogated through a conventional (incoherent) optical time-domain reflectometer (OTDR). Customizable alarm threshold temperatures can be designed and set by adjusting the pressure of the CO2 filling the air-hole region, which in turn determines a threshold temperature under which CO2 liquefies. The observed slopes of the backscattered Rayleigh intensity trace as a function of the position along the fiber serve as indicators of the CO2 states, allowing the identification of both gaseous and liquid phases through variations in the optical attenuation. Utilizing a comparative analysis of curve slopes, the proposed method enables the distributed identification and localization for both cold and hot spots along the fiber. The spatial resolution and the required loss accuracy are subject to the classical tradeoff inherent to OTDR interrogation. In this study, two interrogation wavelengths (namely, 1310 nm and 1550 nm) are exploited. Results point out that the selection of the operating wavelength gives rise to optical attenuation factors with distinct contrasts along the OTDR traces, allowing the optimization of the system to meet specific measurement objectives. In particular, the use of an optical source at 1550nmdemonstrates superior measurement accuracy within short fiber lengths, revealing a higher loss contrast between gas and liquid phases. Conversely, a 1310nmlight source is deemed more suitable for long-distance monitoring due to the lower optical loss in cold spots (CO2 in liquid phase), providing relevant measurements over extended cooled fiber sections. Based on our experimental results using a spatial resolution of 30 cm, the maximum detection length is limited to 36.0mor 16.0mat 1310 nm or 1550 nm, respectively, which take place when all CO2 liquefies inside the fiber....
Optical fiber Raman and surface-enhanced Raman scattering (SERS) probes hold great promise for in vivo biosensing and in situ monitoring of hostile environments. However, the silica Raman scattering background generated within the optical fiber increases in proportion to the length of the fiber, and it can swamp the signal from the target analyte. While filtering can be applied at the distal end of the fiber, the use of bulk optical elements has limited probe miniaturization to a diameter of 600 μm, which in turn limits the potential applications. To overcome this limitation, femtosecond laser micromachining was used to fabricate a prototype micro-optical filter, which was directly integrated on the tip of a 125 μm diameter double-clad fiber (DCF) probe. The outer surface of the microfilter was further modified with a nanostructured, SERS-active, plasmonic film that was used to demonstrate proof-of-concept performance with thiophenol as a test analyte. With further optimization of the associated spectroscopic system, this ultra-compact microprobe shows great promise for Raman and SERS optical fiber sensing....
This paper demonstrates a five-layer InAs/InP quantum-dash semiconductor optical amplifier (QDash-SOA), which will be integrated into microwave-photonic on-chip devices for millimeter-wave (mmWave) over fibre wireless networking systems. A thorough investigation of the QDash-SOA is conducted regarding its communication performance at different temperatures, bias currents, and input powers. The investigation shows a fibre-to-fibre (FtF) small-signal gain of 18.79 dB and a noise figure of 6.3 dB. In a common application with a 300 mA bias current and 25 ◦C temperature, the peak FtF gain is located at 1507.8 nm, which is 17.68 dB, with 3 dB gain bandwidth of 56.6 nm. Furthermore, the QDash-SOA is verified in a mmWave radio-over-fibre link with QAM (32 Gb/s 64-QAM 4-GBaud) and OFDM (250 MHz 64-QAM) signals. The average error vector magnitude of the QAM and OFDM signals after a 2 m wireless link could be as low as 8.29% and 6.78%, respectively. These findings highlight the QDash-SOA’s potential as a key amplifying component in future integrated microwave-photonic on-chip devices....
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