Optical Fiber Technology最新文献

This paper introduces a novel metric and approach for link quality measurement and a new algorithm for human-intervention-free optical link balancing, specifically designed for optical fiber transfer systems that require bidirectional amplification. Bidirectional amplification, essential for reciprocal optical paths to compensate fluctuations for new non-data applications like accurate time transfer and ultrastable coherent frequency transfer, introduces complexities such as feedback loops and phase inconsistencies. Our work ensures that amplified signals maintain precise time alignment, a critical aspect of any bidirectionally amplified system.

Amplification processes often introduce phase noise and frequency fluctuations, which are disruptive, especially for non-data applications, necessitating a delicate balance between amplification and signal integrity. Our approach aims to provide a comprehensive solution for these complexities.

Our algorithm’s effectiveness is demonstrated through rigorous testing on real-world infrastructure. It successfully balances several optical links, indicating robustness when handling bidirectional amplification complexities. Furthermore, an extended use case involving a cascade of four balanced optical amplifiers demonstrates the algorithm’s efficiency in more intricate scenarios.

This concept has been successfully deployed and tested on one fiber segment of the Czech national research and education network. We discuss the substantial benefits observed in the newly balanced links, highlighting significant advancements in mitigating the challenges of bidirectional amplification. Our findings represent a significant step forward in optical network technologies, addressing critical issues in modern open optical communication systems.

We propose a purification relay station for optical frequency dissemination over long-distance communication fiber links particularly in complex environments. This technique addresses the challenge of phase noise suppression limitation due to dissemination delay in laser traversing fiber links. Utilizing a cavity-stabilized hertz-linewidth laser, we synchronized the phase noise with that of the signal received from the previous link within a 10 Hz bandwidth. Beyond this range, the phase noise followed the hertz-linewidth laser, decreasing from 20 rad to 6 rad. Furthermore, to ensure continuous coherence and stability of the disseminated laser, the data processing based on FPGA was employed to eliminate phase cycle slips in the previously disseminated optical frequency. We applied this technique to the optical frequency disseminated along with a 106 km communication fiber link. After optical frequency purification, the fractional frequency instability at a 1 s averaging time is reduced by a factor of three. Additionally, with the elimination of the phase cycle slips, the fractional frequency instability of purified optical frequency scales as $\frac{1}{\tau }$ which matches with a signal dominated by phase-modulated white noise. At a 10,000 s averaging time, the purified optical frequency achieves a stability of 8.43 × 10⁻¹⁹, representing a reduction of two orders of magnitude compared to that of the previously disseminated optical frequency. This work establishes the foundation for the development of a nationwide optical frequency dissemination network involving long-distance fiber links in complex environments.

Immersive internet usage has increased due to spatial computing technologies like VR, AR, and MR. The phenomena have transformed gaming, entertainment, education, healthcare, and other industries. According to recent studies, emerging access network power utilization in immersive technologies is driving the need for energy-efficient solutions. We present a method of OLT utilizing Vanilla-RNN algorithms to efficiently handle ONU sleep cycles, resulting in reduced energy consumption, enhanced network performance, and increased user satisfaction. We present a mathematical formulation of the Vanilla-RNN model and its usage for forecasting optimal sleep durations for ONUs in the 25G-NGEPON. This study further explores the utilization of immersive technology to enhance user experiences and network efficiency by integrating AI and ML in access networks. A proposed novel dynamic bandwidth technique in spatial computing multimedia (SCM-RNN) ensures both QoS and energy efficiency. The assessment findings indicate that the proposed solution successfully achieves a high energy savings ratio of 28 % without compromising the QoS for spatial computing multi-media service environments.

We report that conventional saturable periodic structures, in sharp contrast to the conventional systems with different nonlinearities which exhibit the typical S- shaped optical bi- and multi-stable states, reveal some unusual and unique nonlinear dynamics. These include the onset of ramp-like optical bistability (OB) and optical multistability (OM) curves which further transit into mixed OM states combining both ramp-like states followed by the S-shaped multistable curves. We also extend this study to another domain of physics, namely parity-time ($\mathrm{PT}$)- symmetry, by including equal amount of gain and loss into the system which then establishes additional degree of freedom by enabling the investigation into additional two domains which are the unbroken and broken $\mathrm{PT}$- symmetric regimes. Although these bi- and multi-stable states are unusual and unique, when the frequency detuning is introduced, the revival of S-shaped stable states is possible but only in the presence of unbroken $\mathrm{PT}$- symmetry. Conversely, the broken $\mathrm{PT}$- symmetry which usually generates ramp-like multistable states, gives rise to the birth of novel multistable states with a vortex like envelope, (the curve that features simultaneous increase in the critical switch-up and switch-down powers with an increase in the input power) causing a novel structure which has not been reported in the existing literature of different physical systems manifesting multi-stable states.

Multi-wavelength fiber lasers have emerged as a promising source for the application in wavelength division multiplexing communication and terahertz wave generation due to their high efficiency and robustness. This paper introduces a section of bent long single-mode fiber (SMF) into the semiconductor saturable absorption mirror and nonlinear polarization rotation hybrid mode-locked Er-doped fiber laser to enhance intra-cavity birefringence to realize wavelength interval tunable dual-wavelength mode-locking and stationary tri-wavelength mode-locking. Dual-wavelength mode-locking has variable wavelength intervals within 11.502 nm–29.541 nm. Tri-wavelength mode-locking can be switched pair-to-pair by adjusting the intra-cavity polarization state. The bent-SMF-induced optimized birefringence comb filter effect is responsible for multi-wavelength mode-locking. Such compact multi-wavelength mode-locked fiber lasers with flexible outputs can meet many applications.

We report the improved performance of the power conversion efficiency of Stokes lines generated in an optical fiber (Corning LEAF or Corning MetroCor) by splicing a fiber segment with a lower MFD (Nufern 1060-XP or Nufern 980- HP). The experimental configuration 4-Km LEAF+1-m 1060-XP has better performance in the 1st Stokes of ∼(1–0.39/0.67) 4.17 %, and in the 2nd Stokes of ∼(1–0.55/0.64) 14 % compared to the configuration that uses 4-Km LEAF fiber without 1060-XP fiber segment. On the other side, the experimental configuration 4-Km MetroCor + 0.5-m 980-HP, had an improved performance in the 1st Stokes of ∼(1–0.64/0.5) 28 %, and in the second Stokes of ∼(1–0.69/0.5) 38 % compared to MetroCor optical fiber without 980-HP fiber segment.

In the production process of petrochemical enterprises, the corrosion monitoring and abnormal warning of petroleum volatilization pipeline in atmospheric pressure equipment of petrochemical industry are of great significance for safe operation. Fiber optic sensing technology with distributed measurement, simple structure and high measurement accuracy has been used in various engineering industries. This paper takes the distributed pipeline corrosion monitoring system based on wFBG sensor as the experimental object, and designs a fusion denoising algorithm based on CEEMDAN, BVD and BWT to denoise the collected vibration signals. On this basis, preliminary experimental verification of the measured data was carried out. The test results show that this system can monitor the large-scale corrosion of atmospheric pressure transmission and distribution pipelines in real time.

This paper reports an experimental demonstration of a stable single-longitudinal-mode (SLM) thulium-doped fiber laser (TDFL) using a quad-coupler triple-ring cavity (QC-TRC) filter based on a passive quad coupler and a uniform fiber Bragg grating (UFBG). The TDFL adopts a ring cavity structure and utilizes a QC-TRC filter with four couplers to select a single longitudinal mode from a dense mode spectrum. The design and fabrication thinking on the QC-TRC filter are explained, and the selection principles for SLM are analyzed in detail. Experimental results show the filter features excellent performance, with the laser at 2048.40 nm exhibiting high stability with an optical signal-to-noise ratio (OSNR) of 69 dB. No significant wavelength drift is observed during the repeating measurement, the maximum wavelength drift and power fluctuation being 0.02 nm and 0.45 dB, respectively. The linewidth of the laser is approximately 7 kHz, measured using the β-separation linewidth method with an imbalanced Michelson interferometer linewidth measurement device.

The pulse energy in mode-locking fiber lasers is fundamentally limited by non-linear phase accumulation. However, the exploitation of this accumulated phase to regenerate the spectrum was successful of increasing the energy per pulse in Mamyshev oscillator. In such a configuration, whether experimentally or numerically, it is almost impossible to find the exact cavity parameters that maximize the energy. In that context, we propose here for the first time a very efficient method based on the genetic algorithm for selecting the tunable filter parameters giving the high pulse energy in the single pulse regime. To this end, five key parameters of the laser system are optimized: the bandwidths of two filters, their separation, and the orders of the two super-Gaussian filters. The genetic algorithm is meticulously tailored to explore the complex parameter space, with the fitness function designed to maximize the single pulse energy while maintaining stability in the laser operation. It is demonstrated that, for a given small signal gain and fixed cavity parameters a specific relationship between filter bandwidths and filter separation must be achieved to obtain high pulse-energy performance. Numerical simulations have demonstrated the generation of stable pulses with a duration of 760 fs, energy of 1.49 nJ, and a peak power reaching 1.5 kW.

We developed a simulation model for the gain modulation Raman fiber laser (RFL) employing the Generalized Nonlinear Schrödinger Equation and integrating the transmission functions of fiber Bragg gratings. Through the pulse tracking technique, we examined the emission characteristics and stable operation range of gain modulated RFL. By manipulating the parameters of the pump pulse source and Raman fiber, we were able to elicit different operational states for output pulses and ascertain the operation range for single-pulse output. Our investigations underscored the pivotal roles played by both the peak power and width of the pump pulse in determining the operational state of the output pulse. Additionally, we found that the dispersion conditions, fiber nonlinear coefficient, and fiber length collectively shape the range over which stable single-pulse output can be sustained. These findings offer valuable insights for optimizing the performance of gain modulation RFLs in practical applications.