The creation and detection of spatial modes of light with transient orbital angular momentum (OAM) properties is of critical importance in a number of applications in sensing and light matter interactions. Most methods are limited in their frequency response as a result of their modulation techniques. In this paper, a new method is introduced for the coherent detection of transient properties of OAM using a single pixel detector system for the creation of an OAM spectrogram. This technique is based on the ideas utilized in acousto-optic based optical correlators with log-polar optical elements for the creation and detection of higher order bessel beams integrated in time (HOBBIT) at MHz data rates. Results are provided for beams with time varying OAM, coherent combinations, and transient scattering by phase objects.This paper proposes a probabilistic shaping orthogonal frequency division multiplexing passive optical network (PS-OFDM-PON) based on chaotic constant composition distribution matching (CCDM). With the implementation of a four-dimensional hyperchaotic Lv system, probabilistic shaping and chaotic encryption are realized with low complexity on the process of signal modulation, so as to enhance the system performance in the presence of bit error rate (BER) and security. An 8.9 Gb/s encrypted PS-16 quadrature amplitude modulation (QAM)-OFDM signal transmission over a 25 km standard single mode fiber (SSMF) is experimentally demonstrated. And experimental results indicate that compared with conventional uniform 16QAM-OFDM, the encrypted PS-16QAM-OFDM can obtain a 1.2 dB gain in receiver sensitivity at a BER of 10-3 under the same bit rate. Moreover, the key space of the proposed scheme is 1.98 × 1073, which is a large enough number to effectively guard against any malicious attacks from illegal optical network units (ONUs). The combined superiority of BER and security performance enables a promising prospect for the proposed PS chaotic encryption scheme in a future low-cost optical access network.Structural, Thermal, and Optical Performance (STOP) analysis is important for understanding the dynamics and for predicting the performance of a large number of optical systems whose proper functioning is negatively influenced by thermally induced aberrations. Furthermore, STOP models are being used to design and test passive and active methods for the compensation of thermally induced aberrations. However, in many cases and scenarios, the lack of precise knowledge of system parameters and equations governing the dynamics of thermally induced aberrations can significantly deteriorate the prediction accuracy of STOP models. In such cases, STOP models and underlying parameters need to be estimated from the data. To the best of our knowledge, the problem of estimating transient state-space STOP models from the experimental data has not received significant attention. Similarly, little attention has been dedicated to the related problem of obtaining low-dimensional state-space models of thermally induced aberrations that can be used for the design of high-performance model-based control and estimation algorithms. Motivated by this, in this manuscript, we present a numerical proof of principle for estimating low-dimensional state-space models of thermally induced aberrations and for characterizing the transient dynamics. Our approach is based on the COMSOL Multiphysics simulation framework for generating the test data and on a system identification approach. We numerically test our method on a lens system with a temperature-dependent refractive index that is used in high-power laser systems. The dynamics of such a system is complex and described by the coupling of thermal, structural, and ray-tracing models. The approach proposed in this paper can be generalized to other types of optical systems.In the second-harmonic generation processes involving Laguerre-Gaussian (LG) beams, the generated second-harmonic wave is generally composed of multiple modes with different radial quantum numbers. To generate single-mode second-harmonic LG beams, a type of improved quasi-phase-matching method is proposed. The Gouy phase shift has been considered in the optical superlattice designing and an adjustment phase item is introduced. By changing the structure parameters, each target mode can be phase-matched selectively, whose purity can reach up to 95%. The single LG mode generated from the optical superlattice can be modulated separately and used as the input signals in the mode division multiplexing system.Multimode based polarization independent (PI) wavelength division multiplexing (WDM) devices are proposed and experimentally demonstrated. The key concept is to utilize two different order modes for the orthogonal polarizations, ith-order mode for TE and jth-order mode for TM (i ≠ j) polarization respectively to extend the flexibility for designing devices. PI coupler composed of a multimode directional coupler and mode converters is introduced as a basic device. Then, we apply PI coupler to Mach Zehnder interferometer (MZI) and Bragg grating bandpass filters. PI MZI is achieved by optimizing the combination of two phase shifters in the interferometer arms. PI bandpass uses 3dB-PI coupler and polarization rotate Bragg gratings that induce mode coupling between the polarizations. Each device showed good matching in the spectrum between TE and TM polarizations in term of operation wavelength. The proposed concept can be a promising approach to realize PI WDM functions without introducing polarization diversity scheme in which a polarization beam splitter, two devices designed for each polarization and a polarization beam combiner are required.We experimentally demonstrate a free-space data transmission system in an indoor simulated smoke chamber with a laser carrier of an erbium-doped actively mode-locked fiber laser and a holmium-doped actively mode-locked fiber laser. Two additional semiconductor lasers operating at 0.85 and 1.06 µm are used to calibrate the visibility of a smoke channel using the Ijaz model and compare smoke attenuation with 1.55 and 2.04 µm lasers. https://www.selleckchem.com/products/ory-1001-rg-6016.html The eye patterns and bit error rates of 1.55 and 2.04 µm laser carriers with a data rate of 4.04 Gbps are investigated experimentally at 0.5, 0.05, and 0.005 km visibilities. The experimental results show that the smoke attenuation is wavelength dependent for V  less then  0.5 km. As the visibility decreases, the long wavelength laser is less affected by the attenuation and power fluctuation caused by Mie scattering. The measured optical signal-to-noise ratios of the 1.55 and 2.04 µm laser carriers for V = 0.005 km are 4.83 and 8.62 dB, respectively. The corresponding link sensitivities are -14.