Low‑light enhancement method with dual branch feature fusion and learnable regularized attention

Restricted by the lighting conditions,the images captured at night tend to sufer from color aberration,noise,and other unfavorable factors,making it difcult for subsequent vision-based applications.To solve this problem,we propose a two-stage size-controllable low-light enhancement method,named Dual Fusion Enhancement Net(DFEN).The whole algorithm is built on a double U-Net structure,implementing brightness adjustment and detail revision respectively.A dual branch feature fusion module is adopted to enhance its ability of feature extraction and aggregation.We also design a learnable regularized attention module to balance the enhancement efect on diferent regions.Besides,we introduce a cosine training strategy to smooth the transition of the training target from the brightness adjustment stage to the detail revision stage during the training process.The proposed DFEN is tested on several low-light datasets,and the experimental results demonstrate that the algorithm achieves superior enhancement results with the similar parameters.It is worth noting that the lightest DFEN model reaches 11 FPS for image size of 1224×10^(24)in an RTX 3090 GPU.

Phase-tailored assembly and encoding of dissipative soliton molecules

Self-assembly of particle-like dissipative solitons,in the presence of mutual interactions,emphasizes the vibrant concept of soliton molecules in varieties of laser resonators.Controllable manipulation of the molecular patterns,held by the degrees of freedom of internal motions,still remains challenging to explore more efficient and subtle tailoring approaches for the increasing demands.Here,we report a new phase-tailored quaternary encoding format based on the controllable internal assembly of dissipative soliton molecules.Artificial manipulation of the energy exchange of soliton-molecular elements stimulates the deterministic harnessing of the assemblies of internal dynamics.Self-assembled soliton molecules are tailored into four phase-defined regimes,thus constituting the phase-tailored quaternary encoding format.Such phase-tailored streams are endowed with great robustness and are resistant to significant timing jitter.All these results experimentally demonstrate the programmable phase tailoring and exemplify the application of the phase-tailored quaternary encoding,prospectively promoting high-capacity all-optical storage.

300 km ultralong fiber optic DAS system based on optimally designed bidirectional EDFA relays

Optical fiber distributed acoustic sensing(DAS)based on phase-sensitive optical time domain reflectometry(φ-OTDR)is in great demand in many long-distance application fields,such as railway and pipeline safety monitoring.However,the DAS measurement distance is limited by the transmission loss of optical fiber and ultralow backscattering power.In this paper,a DAS system based on multispan relay amplification is proposed,where the bidirectional erbium-doped fiber amplifier(EDFA)is designed as a relay module to amplify both the probe light and the backscattering light.In the theoretical noise model,the parameters of our system are carefully analyzed and optimized for a longer sensing distance,including the extinction ratio(ER),span number,span length,and gain of erbium-doped fiber amplifiers.The numerical simulation shows that a bidirectional EDFA relay DAS system can detect signals over 2500 km,as long as the span number is set to be more than 100.To verify the effectiveness of the scheme,a six-span coherent-detection-based DAS system with an optimal design was established,where the cascaded acoustic-optic modulators(AOMs)were used for a high ER of 104 dB.The results demonstrate that the signal at the far end of 300.2 km can be detected and recovered,achieving a high signal-to-noise ratio of 59.6 dB and a high strain resolution of 51.8■at 50 Hz with a 20 m spatial resolution.This is,to the best of our knowledge,a superior DAS sensing distance with such a high strain resolution.

Ultrafast temporal-spectral analysis probes isomeric dynamics in a dissipative soliton resonator

Self-assembly of dissipative solitons arouses versatile configurations of molecular complexes,enriching intriguing dynamics in mode-locked lasers.The ongoing studies fuel the analogy between matter physics and optical solitons,and stimulate frontier developments of ultrafast optics.However,the behaviors of multiple constituents within soliton molecules still remain challenging to be precisely unveiled,regarding both the intramolecular and intermolecular motions.Here,we introduce the concept of“soliton isomer”to elucidate the molecular dynamics of multisoliton complexes.The time-lens and time-stretch techniques assisted temporal-spectral analysis reveals the diversity of assembly patterns,reminiscent of the“isomeric molecule”.Particularly,we study the fine energy exchange during the intramolecular motions,therefore gaining insights into the degrees of freedom of isomeric dynamics beyond temporal molecular patterns.All these findings further answer the question of how far the matter-soliton analogy reaches and pave an efficient route for assisting the artificial manipulation of multisoliton structures.