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Semiconductor Integrated Optics for Switching Light, Second Edition provides concise description of the physics and engineering of semiconductor optical waveguides for photonic and electronic switching with a focus on optical communication applications. It provides Python notebooks that illustrate the concepts discussed in the book.

With the rapid development of optoelectronic devices, photodetectors have triggered unprecedented promise in the field of optical communication, environmental monitoring, biological imaging, chemical sensing. At the same time, there is a higher requirement for photodetectors. It is still a huge challenge for photodetectors that possess excellent performance, low cost and broad range photoresponse from ultraviolet to infrared. In this work, a facile, low cost growth of Sb2Te3 thin film using magnetic sputtering was performed. After rapid annealing treatment, the crystallinity of the thin film was transformed from amorphous to polycrystalline. Ultraviolet-visible-infrared absorption study of the thin film revealed broad absorption range, which is ideal for use in broadband photodetectors. Such photodetectors can find many important applications in communication, data security, environmental monitoring and defense technology etc. A prototype photodetector, consisting of Sb2Te3/n-Si heterostructure, was produced and characterized. The device demonstrated a significant photoelectric response at a broad spectral range of between 250 and 2400 nm. The maximum responsivity and detectivity of the device were 270 A W-1 and 1.28 × 1013 Jones, respectively, under 2400 nm illumination. Therefore, the results showed the potential use of Sb2Te3 thin film in developing high performance broadband photodetectors.

The advent of silica-based low-cost standard single-mode fibers revolutionized the whole communication industry. The deployment of optical fibers in the networks induces a paradigm shift in the communication technologies used for long-haul information transfer. However, the communication using the optical fibers is affected by several linear and nonlinear effects. The most common linear effects are attenuation and chromatic dispersion, whereas the dominant nonlinear effect is the Kerr effect. The Kerr effect induces a power-dependent nonlinear distortion for the signal propagating in the optical fiber. The detrimental effects of the Kerr nonlinearity limit the capacity of long-haul optical communication systems. Fiber Kerr nonlinearity compensation using digital signal processing (DSP) techniques has been well investigated over several years. In this paper, we provide a comprehensive tutorial, including the fundamental mathematical analysis, on the characteristics of the optical fiber channel, the origin of the Kerr nonlinearity effect, the theory of the pulse propagation in the optical fiber, and the numerical and analytical tools for solving the pulse propagation equation. In addition, we provide a concise review of various DSP techniques for fiber nonlinearity compensation, such as digital back-propagation, Volterra series-based nonlinearity equalization, perturbation theory-based nonlinearity compensation, and phase conjugation. We also carry out numerical simulation and the complexity evaluation of the selected nonlinearity compensation techniques.

We report experimental observations performed using a net anomalous dispersion Er-doped fiber ring laser without polarization-selective elements, highlighting the domain-wall solitary pulses generated under the incoherent polarization coupling. By adjusting the pump power and the polarization state appropriately, bright and dark solitons can stably co-exist in the cavity, both centered at 1562.16 nm with a 3-dB spectral width of ∼ 0.15 nm and a repetition rate of 3.83 MHz. Moreover, the 0.8 mm long thulium-doped fiber (TDF) facilitated the mode-locking and self-starting of the laser. This is the first demonstration of a laser being used to generate bright and dark solitons synchronously while using TDF as the saturable absorber (SA). Except possessing the all-fiber structure, the laser exhibits good stability, which may have a significant influence on improvement of the pulse-laser design, and may broaden practical applications in optical sensing, optical communication, and soliton multiplexed systems.

Constant, real-time temperature monitoring of the supercapacitors for efficient energy usage is in high demand and seems to be crucial for further development of those elements. A fiber-optic sensor can be an effective optoelectronic device dedicated for in-situ temperature monitoring of supercapacitors. In this work, the application of the fiber-optic microstrucutre with thin zinc oxide (ZnO) coating fabricated in the atomic layer deposition process applied as a temperature sensor is reported. Such a structure was integrated with supercapacitors and used for the temperature measurements. Described sensors are built with the utility of the standard optical telecommunication fibers. The inner temperature of the supercapacitor was investigated in the range extending from 30 °C to 90 °C with a resolution equal to 5 °C. The sensitivity of temperature measurement is about 109.6 nW °C−1. The fitting of the sensor was achieved with a correlation coefficient R 2 = 0.97.

Light propagating through periodic photonic lattice supporting Bloch modes are leaky in nature. Recently it has been established that such 1-D photonic lattices can provide robust loss-less guidance of light by appropriate structural modulation following special models. However, these special models compel the structure to be quasi-periodic, which makes their fabrication less feasible. Thus, we propose a fabrication feasible 1-D periodic lattice having topological features which are established by Zak phase analysis. We demonstrate the existence of an edge state in this specialty photonic lattice as well as its robustness against lattice dislocations. By numerical simulation, we have also illustrated that these states can be amplified without any distortion by introducing homogeneous gain to the lattice substrate. This is a strikingly different phenomenon from the conventionally known fact that with the introduction of gain to periodic lattices, the propagating state of light spreads in the transverse direction due to enhanced complex coupling. Therefore, we present a study of the interplay between topology and non-Hermiticity from the standpoint of device application in this report. The findings suffice to propose the utility of such systems as on-chip optical interconnects and have the potential for topological amplifiers within the regime of optical communication.

To meet the growing needs of internet data, optical communication systems have become the backbone of modern communications networks. At the present time, the dense wavelength division multiplexing (DWDM) technique has been used to increase the number of channels, but the nonlinear effects have a great impact that limits the performance of doubling the DWDM system. The four wave mixing (FWM) is the most harmful and dangerous as the effect of FWM increases on the system the greater the optical connection distances. The new approach of pairing groups of different optical signals was investigated to suppress the FWM effect. The simulation was conducted for an 8-channel system with a total data rate (80Gb/s). A comparative study was conducted on the suppression of FWM by the difference in the power inputs (-0.5 to 20) dBm. The robustness of the proposed technique was examined using two forms of modulation (Carrier Suppressed Return to Zero (CSRZ) and Duo Binary Modulation class -1(DBM-1)) techniques, with optical fiber system of (1,2,5) spans, each of length 60 Km, with spacing between the channels 50GHz. The power of FWM was significantly reduced with the CSRZ & DBM-1 techniques to less than (47.97%, 41.38 %) respectively, at an input power of 12.5 dBm. The performance of the proposed system with the polarization technique was improved by the rate of the quality factor (Q-factor of (91.59%, 78.67%) for the same sequence of modulation.

Thulium-doped optical Fiber enhancers (TDFA) are advanced to cover the optical media transmission Wavelength Division Multiplexing (WDM) information transmission in the envisioned the band (800-1800 nm) with up to 6.5dB increment and noise figure as low as 2.6 dB. We existing the first in-band diode-siphoned thulium-doped fiber amplifier (TDFAs) operational in the wavelength locale and test their appropriateness as high request enhancers in possible coming media transmission frameworks.

In the field of optics the tinier devices are the better; therefore, the diffraction limit of light seems like an essential limitation in the way of that field. In return, new methods have appeared to resolve this issue. One of these methods is the plasmonic technology which allows light pressure into nanostructures. The current study proposes all-optical logic gates based on metal insulator metal structures (mim) waveguide. This waveguide has an important characteristic which is restricting the applied light strongly far from the diffraction limit. The proposed structure is small compared to the applied wavelength. The optical plasmonic gates proposed are (OR, NOR, AND, NAND, NOT). The comsol multiphysics 5.5 software was used for simulation by the 2-D FDTD method. Hence, these five gates will be obtained by optical interference between the propagating signals through the input ports and the control ports, whose positions can be altered according to the gate needed. The implementation and simulation of the proposed gates were all in the same structure, with the same dimensions, the same wavelength and the same transmission threshold, with applicable wavelength of (1550 nm). The performance of the proposed plasmonic gates was tested by two criteria; the optical transmission ratio and the contrast ratio, which is the ratio between the ON and OFF states of the proposed gate..

Type-II ‘W’-lasers have made an important contribution to the development of mid-infrared laser diodes. In this paper, we show that a similar approach can yield high performance lasers in the optical communications wavelength range. (GaIn)As/Ga(AsSb) type-II ‘W’ structures emitting at 1255 nm have been realised on a GaAs substrate and exhibit low room temperature threshold current densities of 200–300 A cm−2, pulsed output powers exceeding 1 W for 100 µm wide stripes, and a characteristic temperature T 0 ≈ 90 K around room temperature. Optical gain studies indicate a high modal gain around 15–23 cm−1 at 200–300 A cm−2 and low optical losses of 8 ± 3 cm−1. Analysis of the spontaneous emission indicates that at room temperature, up to 24% of the threshold current is due to radiative recombination, with the remaining current due to other thermally activated non-radiative processes. The observed decrease in differential quantum efficiency with increasing temperature suggests that this is primarily due to a carrier leakage process. The impact of these processes is discussed in terms of the potential for further device optimisation. Our results present strong figures of merit for near-infrared type-II laser diodes and indicate significant potential for their applications in optical communications.

Thin films play an important role in modern science and technology. With the development of optical fibre communication technology and laser technology, thin films are used more and more widely in this field. The application of optical film in optical communication and laser technology is introduced systematically. The application of optical films in optical communications basically covers a variety of conventional optical films. Based on this research background, the paper mainly analyses the optical and physical properties of zinc oxide nano-films and discusses its application in optical communication.

With the development and progress of space technology, more and more scholars begin to study FSO communication. The free-space optical communication takes the atmosphere as the medium, and the signals are susceptible to atmospheric turbulence. As an important channel code, LDPC code is applicable to almost all channels. In order to obtain better communication performance, we propose dynamically adjusted log-likelihood ratio (LLR) as the input of LDPC decoder in this paper. Compared with the traditional LLR input, the simulation results show that the LDPC code based on dynamically adjusted LLR has stronger anti-turbulence ability and better error performance under different atmospheric turbulence conditions. Coherent communication system with PM-QPSK modulation format under FSO turbulence channel is utilized in our work.

Narrow linewidth light source is a prerequisite for high-performance coherent optical communication and sensing. Waveguide-based external cavity narrow linewidth semiconductor lasers (WEC-NLSLs) have become a competitive and attractive candidate for many coherent applications due to their small size, volume, low energy consumption, low cost and the ability to integrate with other optical components. In this paper, we present an overview of WEC-NLSLs from their required technologies to the state-of-the-art progress. Moreover, we highlight the common problems occurring to current WEC-NLSLs and show the possible approaches to resolving the issues. Finally, we present the possible development directions for the next phase and hope this review will be beneficial to the advancements of WEC-NLSLs.

Optical frequency combs have emerged as an important tool enabling diverse applications from test-and-measurement, including spectroscopy, metrology, precision distance measurement, sensing, as well as optical and microwave waveform synthesis, signal processing, and communications. Several techniques exist to generate optical frequency combs, such as mode-locked lasers, Kerr micro-resonators, and electro-optic modulation. Important characteristics of optical frequency combs include the number of comb lines, their spacing, spectral shape and/or flatness, and intensity noise. While mode-locked lasers and Kerr micro-resonators can be used to obtain a large number of comb lines compared to electro-optic modulation, the latter provides increased flexibility in tuning the comb spacing. For some applications in optical communications and microwave photonics, a high degree of integration may be more desirable over a very large number of comb lines. In this paper, we review recent progress on integrated electro-optic frequency comb generators, including those based on indium phosphide, lithium niobate, and silicon photonics.

To stabilize an optical link, in this study, we propose to control the focus of the received laser beam in free-space optical (FSO) communications between mini-unmanned aerial vehicles (UAVs) and ground stations. Numerical calculations confirm that the coupling efficiency of the received laser beam to an optical fiber (OF) at the ground station is improved by compensating for the shift in the received beam’s focal position caused by the movement of the mini-UAV. Additionally, we conduct an outdoor experiment in which a laser beam is transmitted between two ground positions under the influence of atmospheric turbulence. This experiment indicates the feasibility of controlling the focus of the received beam in realistic environments. These results are expected to significantly contribute to the stabilization of optical links in mini-UAV-to-ground FSO communications.

A supercontinuum (SC) based chalcogenide As38Se62 PCF for broadband mid-infrared light source is numerically reported. For the computational studies, the design of the proposed structure is made up of three rings of air holes with circular and elliptical shapes. The proposed structure provides excellent nonlinear coefficient and dispersion optimization. For the analysis, the finite difference frequency domain (FDFD) method is employed. Due to the high nonlinear refractive index and optimizing design of As38Se62 chalcogenide glass, an effective mode area of 40.5972 μm2 is obtained. The dispersion characteristic of the proposed structure has a zero-dispersion wavelength at 3.89 μm. The nonlinear coefficient is 761 W-1km-1 at the wavelength of 4 μm. Dispersion is almost flat from 2 μm up to 10 μm. The supercontinuum spectrum calculated ranges from 2 μm to 9 μm. The presented structure is appropriate for medical imaging, optical coherence tomography and optical communications.

This paper presents a low noise 28 Gbaud/s linear receiver front-end for fourth-order pulse amplitude modulation (PAM4) signal applied in the field of optical communication. The designed receiver front-end includes a transimpedance amplifier(TIA), an automatic gain control (AGC) and a DC offset cancellation (DCOC) circuit. The pseudo-differential structure of the TIA is designed to achieve low noise. The resistance and capacitance degradation technology are introduced in the variable gain amplifier(VGA) and the equalizer(EQ) to improve linearity and optimize the bandwidth. In the AGC mode, the feedback loop controls the output amplitude to be a desired value within a large range of input current. The PAM4 optical receiver front-end achieves a maximum differential transimpedance gain of 76 dBΩ and -3dB bandwidth of 27 GHz. The equivalent input noise current density with the front-end circuit is 11.2 pA / Hz . In 0.13µm BiCMOS technology, the PAM4 front-end chip consumes 200 mW with a 3.3V voltage supply.

With the rapid development of optical communication network and related technology, the frequency resource of light wave is becoming more and more insufficient, which requires new light sources to support the communication system.With the continuous development of fiber laser technology, Tm-doped fiber laser appears, which brings new vitality to the optical communication network with insufficient frequency resources. Because Tm -doped fiber laser can provide multiple frequencies of optical wavelength resources, it has attracted more and more attention. The development of rare earth doping technology and double cladding pumping technology has laid a solid foundation for the design of Tm-doped fiber laser with excellent performance. In this paper, the Tm-doped fiber laser is studied. The effect of each element in the Tm-doped fiber laser on the laser is analyzed. The influence of the reflectivity of the mirror on the performance of the whole laser is discussed. The simulation results show that the reflectivity of the mirror will seriously affect the output power of the laser, which is of great significance for the design of fiber lasers.

Dense wavelength division multiplexing system is processing at a superfying due to very high transmission capacity in optical communication. In this research article, we analysis 64 channels DWDM system at 10 Gbps data rate is used to rectify the system quality at different power levels and different frequency spacing an 50 km Single Mode Fiber (SMF). For the batter gain we used EDFA (Erbium Doped Amplifiers), system efficiency and system capacity enhancing using DCF in this work. Also simulation at different power levels and frequency spacing analyze BER, Q-factor and Eye height is the terms of results using Optisystem software.

The satellite communications networks have certainly been innovated recently by Inter-satellite optical wireless communication (IsOWC) networks. The prerequisite for next generation mobile satellite communication is superior multimedia facility for consumers at anytime and anywhere. The proposed optical communication system is designed and analysed to improve data transmission quality over the distance between two geostationary (GEO) satellites greater than 36000 km. This trend is to achieve high speed transmission with minimizing the presence possibility of free space loss in transmission that can occur in satellite communication via the longest range. Numerous transceivers IsOWC is a hopeful way to deal with be utilized related to different earth stations as a system utilized between the geosynchronous satellites. The wireless transmission creates the opportunity at high optical power without free space loss. The results of the simulated system showed that with 32 transmitters/receivers IsOWC, the Q-factor values of 36.526, 12.176 and 4.015 are obtained at 38000 km range at laser power of (19, 14 and 9) dBm, respectively. The proposed system is operated at 19 dBm optical power and different values of aperture size and the best values of Q-factor and BER are 41 and 10−250, respectively, for highest diameter value of 20 cm. The operation of the system with various values of bit rate is verified as well. It is seen that the best system performance is at 0.032 Gb/s bit rate and will be of lower as the bit rate increases until it roughly fixes at 32 Gb/s. This research offers the treatment for the transmission problem for ultra-speed application in mobile satellite systems.

Circularly polarized light (CPL) has been given great attention because of its extensive application. While several devices for CPL detection have been studied, their performance is affected by the magnitude of photocurrent. In this paper, a self-powered photodetector based on hot electrons in chiral metamaterials is proposed and optimized. CPL can be distinguished by the direction of photocurrent without external bias owing to the interdigital electrodes with asymmetric chiral metamaterials. Distinguished by the direction of photocurrent, the device can easily detect the rotation direction of the CPL electric field, even if it only has a very weak responsivity. The responsivity of the proposed detector is near 1.9 mA/W at the wavelength of 1322 nm, which is enough to distinguish CPL. The detector we proposed has the potential for application in optical communication.

This study has revealed that the dominant nonlinear of four-wave mixing (FWM), shown a significant impact of performance limitation of the wavelength division multiplexing systems (WDM). The interaction and accumulation of the chromatic dispersion and the effect of the fiber nonlinear along the optical link length, are shown a limited performance of the long distance of optical communication system. Also, we investigated the relationships of FWM power with the fiber length of several values of the inter channel spacing, input power, the effective core area, number of channels in the system. The results are shown that the dominant influence of FWM at the dispersion of zero-wavelength in comparison to the end wavelength, where ultimately, it reaches the maximum value of fiber length≈ 22 km. Furthermore, it is also shown that the FWM noise power is, consequently, increased, after assembly of other factors, including, (1) the increase of the input power, (2) the number of channels in the system, (3) the decrease of the frequency spacing, effective core area.

Global data traffic is growing rapidly, and the demand for optoelectronic transceivers applied in data centers (DCs) is also increasing correspondingly. In this review, we first briefly introduce the development of optoelectronics transceivers in DCs, as well as the advantages of silicon photonic chips fabricated by complementary metal oxide semiconductor process. We also summarize the research on the main components in silicon photonic transceivers. In particular, quantum dot lasers have shown great potential as light sources for silicon photonic integration—whether to adopt bonding method or monolithic integration—thanks to their unique advantages over the conventional quantum-well counterparts. Some of the solutions for high-speed optical interconnection in DCs are then discussed. Among them, wavelength division multiplexing and four-level pulse-amplitude modulation have been widely studied and applied. At present, the application of coherent optical communication technology has moved from the backbone network, to the metro network, and then to DCs.

The similarity between in-plane directions of spatial optics and overlapped time ranges of temporal optics is introduced as a new rule of the space–time duality. Applying this rule, an optical dual random phase encoding (DRPE) cryptosystem in the temporal anamorphic fractional Fourier transform (TAFrFT) domain is proposed for physical-level protection of time-varying signals. The structure of a TAFrFT system is an anamorphic time lens (ATL) sandwiched by two identical dispersion elements. The additional key provided by a TAFrFT system is only related to phase profile of the involved ATL, leading to a dispersion-independent manner of key updating as well as an enlarged key space (KS) in comparison with the conventional temporal FrFT and Fresnel transform system. This manner of key updating has potential as a one-time key strategy to evade the intrinsic linearity and symmetry weakness of DRPE-like temporal cryptosystems, due to the updating speed being comparable to the frame rate of plaintext signals. As the temporal counterpart of a spatial optical device composed of cylindrical lenses along different directions, an ATL is designed as an equal-spaced array of time lenses with unipolar phase, constant extension, and varying phase height. Implemented by an arbitrary waveform generator (AWG)-driven electro-optic phase modulator (EOPM), the time interval of adjacent time lenses, extension of each time lens, and the standard phase height are optimally designed as functions of the AWG bandwidth B M and the EOPM damage phase threshold Γ 0 . By numerical simulations, a 16-slot input optical Gaussian pulse sequence with half pulse width of 10 ps and frame length of 2000 ps is encrypted with a KS near 2 698 provided by ATLs at parameters B M = 100 GHz and Γ 0 = 5 π radians under the state of the art, enough for resistance to brute-force attacks.

As photonic integration continues to evolve, compact and low loss Mach–Zehnder interferometers (MZI) have been an area of significant research in recent years. Here, we propose a valley-Hall effect based topologically protected Mach–Zehnder interferometer (TPMZI). Our simulations show that the TPMZI is efficient and stable even in complex situations. Sharp waveguide bending and defects such as obstructions and epitaxial disorders, do not affect the propagation of photons along the interface, which guarantees the TPMZI high output power. In addition, the TPMZI yields excellent sensitivity, extinction ratio and modulation depths, making it advantageous over existing systems when applied to optical communication, biochemical sensing, spectrometer analysis and measurement systems, etc.

In order to improve the performance of a communication system, a novel concept of low-crosstalk demodulating vortex beams by a combination of partial-receiving apertures (PRAs) is proposed. The corresponding theory analysis and simulations are performed for certifying the valid of the proposed concept in theory. A proof-of-concept experiment is also proposed and established to verity the feasibility of the proposed concept in practice. Based on the captured intensity-array profiles in experiments, the total crosstalk, which is induced by partial receiving apertures, can be evenly distributed among the parasitic orbital angular momentum (OAM) modes, then the maximum ratio of intensity between the induced parasitic OAM modes and the propagated OAM modes can be notably decreased when two unsymmetrical PRAs are utilized. The measured bit error rate curves (with respect to the differently-placed PRAs) also show that the performance of system can be improved in sequence when three ways of one PRA, two symmetric PRAs and two asymmetric PRAs are orderly utilized for demodulating OAM beams, respectively. Besides, the measured results also demonstrate that the proposed system performances are declined with the increases of data rates or propagation distances. Consequently, our proposed concept in this paper is valid and reliable in both theory and practice, and then can be used to demodulate the vortex beams with low crosstalk for free-space optical communication in future.

Uncertainty in discriminating between different received coherent signals is integral to the operation of many free-space optical communications protocols, and is often difficult when the receiver measures a weak signal. Here we design an optical communications scheme that uses balanced homodyne detection in combination with an unsupervised generative machine learning and convolutional neural network (CNN) system, and demonstrate its efficacy in a realistic simulated coherent quadrature phase shift keyed (QPSK) communications system. Additionally, we program the neural network system at the transmitter such that it autonomously learns to correct for the noise associated with a weak QPSK signal, which is shared with the network state of the receiver prior to the implementation of the communications. We find that the scheme significantly reduces the overall error probability of the communications system, achieving the classical optimal limit. This communications design is straightforward to build, implement, and scale. We anticipate that these results will allow for a significant enhancement of current classical and quantum coherent optical communications technologies., Comment: 9 pages, 4 figures

The essence of optical fiber communication transmission technology is to use light as the carrier of information, and to achieve the purpose of information transmission through the optical fiber network. The communication mode based on optical fiber communication technology has been widely recognized in the field of industrial production and telecommunication transmission due to its good information transmission performance. However, with the expansion of the construction scale of optical fiber communication network and the improvement of user coverage, the disadvantages of the management and maintenance of the traditional optical fiber communication network are becoming more and more obvious. Therefore, this paper describes the characteristics of the optical fiber communication technology, and analyses the existing problems in the optical communication system and their causes. On this basis, this paper analyses the automatic operation and maintenance technology of optical fiber communication system. The analysis results in this paper provide some technical support for the deep integration of computer control technology and optical fiber communication automatic maintenance system.

The usage of data transmission through Optical Fiber is highly preferred in every area where transferring of data is needed from one end to another. Moreover, nowadays the infrastructure of telecommunications is in good shape and size to handle data transmission through its optical fibers which have low attenuation and higher bandwidth. The seeking of data rate higher than 100Gbit/second and above has been increased to build it in urban and rural areas, and for long and short hauls. Consequently, the current goal is to propel this transmission system into the next appropriated level to avoid any decline of the optical infrastructure than its current capacity. To fulfill increased demand for bandwidth in Broadband services one of the most trusted technology is the Orthogonal Frequency Division Multiplexing (OFDM). The Orthogonal Frequency Division Multiplexing has been placed on-demand in optical communication, it is used in Long haul transmission Format in Direct and Coherent detection. OFDM has many features and abilities can boost the optical fiber performance by eliminating several limits of conventional Optical Fiber communication. OFDMA has polarization mode dispersion (PMD) and chromatic dispersion (CD) which are considered a big addition to the current systems. In addition to that, the easy correlation of the coherent optical OFDM with Wavelength Division Multiplexing (WDM) systems can further advantages in the transmission system such as super bandwidth, high spectral efficiency, and extra data rates. Furthermore, the WDM systems can improve data rate and capacity by using multiple wavelengths over a single fiber. This work aims to bring implementation and to perform a deep-dive study of higher data rates using Direct and Coherent Optical OFDM for long path transmissions. This research starts with a unique user and then extends to the add the OFDM - WDM system to get a data rate of 100 Gbps. Regarding the software portion, the Optisystem simulation tool was used for the design and implementation of the system. Moreover, the modulation type used is QAM for the OFDM signal, and I/Q modulation is deployed, while Coherent and Direct detection is used at the receiving portion. Q Factor, the bit error rate and eye diagram were discussed to study the System’s Performance and Quality. This work found CD-OOFDM is the best system for next generation of optical. The work compared WDM CD-OOFDM with SMF-DCF to DD and CD-OOFDM. In addition to that, it compared WDM CD-OOFDM with SMF-DCF to CD-OODFM with SMF. Therefore, the results showed that WDM CD-OOFDM with SMF-DCF achieved 25 Gbps for four channels of the WDM system at 120km channel, where the carrier frequencies were from 193.05THz to 193.2THz.

The crosstalk of orbital angular momentum（OAM）modes is one of the most important issues for free-space optical (FSO) communication. We theoretically derive a crosstalk model for Laguerre-Gaussian (LG) vortex beams propagating in turbulent atmosphere. The calculated crosstalk of different OAM modes in different turbulence by analytical expression is consistent with experimental measurements. Both theoretical and experimental results reveal that the crosstalk of high order LG vortex beams is more obvious in atmospheric turbulence. Different from the numerical calculation of the integral expression of the previous studies, this analytical expression can directly and quantitatively characterize the crosstalk and the law of different topological charges in vortex beams. Based on this analytical expression, the crosstalk widths of vortex beams with different topological charges can be calculated accurately, so that the optimal sets of OAM modes can be found more easily under each atmospheric turbulence condition.

A T-shaped reflective grating device under the second Bragg angle is proposed for polarizer. This grating device is mainly made of fused silica with T-shaped ridges, which can diffract the energy of the TE-polarized light and the TM-polarized light to the -2nd order and the 0th order with the reflective efficiency of each order more than 95%. Normalized field magnitude distribution and overlap integral are analyzed to explain the physical mechanism and energy exchange. Based on the optimized results, the beam splitter exhibits high efficiency, good extinction ratio and optical properties of the incident bandwidth. Moreover, grating can have longer period for easy fabrication under second Bragg incidence compared to reported Bragg incidence. Therefore, the T-shaped reflective grating device should be useful for the future optical communication industry.

In this paper, we are going to exhibit the system performance using the single, double and three-electrode quantum-dot semiconductor optical amplifier as an intensity modulator (3E-QD-SOA-IM) of the adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM) signals in the intensity-modulation direct-detection passive optical network (IMDD-PON) systems. Moreover, to compare the bit-rate versus transmission distance of the proposed fiber link model when using both configurations multi-electrode semiconductor optical amplifier intensity-modulator (ME-SOA-IM) and multi-electrode quantum-dot semiconductor optical amplifier intensity-modulator (ME-QD-SOA-IM), to study the improvement of the transmission capacity, distance reach and power efficiency when applying the proposed configurations for optical access networks for distances ranging from 20 km up to 120 km. The three-electrode configuration solved the nonlinearity of the two-electrode configuration and offered a considerably wider range of optimum operating conditions to achieve up to 35 Gbps. Furthermore, the 3E-QD-SOA-IM showed a better performance over the 3E-SOA-IM over all the 120 km, and a 5 Gbps enhancement in the bitrate with a 20 dB less optical input power at 20 km.

One of the major challenges for free-space optical communication through atmosphere is the turbulence caused by the random variations in temperature and convective motion of air. It induces fluctuation in intensity and phase of the propagating optical signal and impairs the transmission quality. The free-space optical communication using beams carrying orbital angular momentum would be vulnerable to such fluctuation since they have a unique spatial phase profile of the helical phase front. In order to overcome the issue, we propose a pilot beam-assisted adaptive compensation method for the turbulence-induced phase fluctuation by using spatial light modulators and a wavefront sensor. The proposed method is a potential candidate for real-time compensation due to its fast operation without algorithmic converging process. The propagation of Laguerre-Gaussian beam through atmospheric turbulence is numerically analyzed based on the modified von Karman model and split-step beam propagation method. The simulation results reveal that the compensation performances are considerably improved by using the pilot beam which has the same azimuthal index as that of the data beam.

The high-speed dynamics of a hybrid distributed feedback semiconductor laser heterogeneously integrated onto silicon is experimentally investigated in the presence of external optical feedback. The laser fabrication relies on a proper modal engineering in which light is generated in the III–V material and stored in the low-loss silicon region in order to substantially enhance the quality factor of the cavity resonator. In this work, the hybrid laser is found to be insensitive to parasitic reflections leading to a 10 Gbps floor-free transmission with a power penalty no greater than 1.5 dB at room temperature. As a conclusion, owing to the large quality factor, a high coherence collapse level is unveiled in such laser indicating its vast potential to serve as an alternative solution for the development of isolator-free applications in future photonics integrated circuits. A qualitative interpretation is also provided by linking the standard feedback equations to the quality factor of the resonator.

Dynamically regulated the coherent light emission offers a significant impact on improving white light generation, optical communication, on-chip photonic integration, and sensing. Here, we have demonstrated two mechanisms of strain-induced dynamic regulation of ZnO lasing modes through an individual ZnO microbelt and microrod prepared by vapor-phase transport method. And systematically explained the dependence on externally applied strain and crystal orientation. Compared with the reduced size of resonant cavity played a major role in the microbelt, the resonant wavelength variation of the microrod under tensile stress is affected by the change in both the cavity size and the refractive index, which tend to antagonize in the direction of movement. It shows that the refractive index can be effectively regulated only when the stress is in the same direction along the c-axis. The results on the linear relationship between the resonance wavelength variation and applied strain imply the capacity of the devices to detect tiny stresses due to the ultra-narrow line width of the cavity mode with a high-quality factor of ~ 104. It not only has a positive influence in the field of the modulated coherent light source, but also provides a feasible strategy for implementing color-resolved non-contact strain sensors.

This paper first introduces the advancement and importance of laser communication technology for drones., then introduced Deep Neural Network (DNN) to develop wireless end-to-end communication systems. Accurate channel state parameters (CSI) are necessary for computing DNN, but in laser communication systems, channel information is difficult to gain in advance or changes quickly with time and environment. This paper will use conditional generation network (GAN) to represent channels. The coded signal of the transmitter and the pilot data are used as condition information. By simulating the simulation results of the lognormal channel, the method can achieve high-quality transmission without clear CSI.