In this letter, we experimentally demonstrate multi-band linear frequency modulation (LFM) signal generation subjected to multi-input optical injection in an external cavity-based Fabry-Pérot laser diode (ECFP-LD). The ECFP-LD is a specially designed FP-LD with a self-injected single longitudinal mode tuned up to 10 nm. The non-linear dynamics in period-one oscillation in ECFP-LD subjected to multi-input

Radio-over-fiber (RoF)-based front haul architecture has attracted considerable attention for fifth-generation (5G) cellular systems because of its cost effectiveness, however, it is susceptible to harmonic frequency distortion and intermodulation products (IMs) arising from the nonlinearity of the laser diode. To overcome this limitation, an asymmetric electrical predistortion method, using a single

Iterative demodulation and decoding has been introduced in 2005 by Colavolpe, Barbieri, and Caire to cope with channels affected by phase noise. However, iterations between the channel decoder and the demodulator increase system’s complexity. In this letter, we propose an iterative carrier recovery scheme where the current iteration is based on the hard decisions taken after the previous iteration

An integrated in-fiber coupling configuration for simultaneously exciting whispering gallery mode (WGM) and Fabry-Perot (FP) resonances in one cavity is proposed and demonstrated experimentally. The WGMs traveling circularly in both clockwise and counter-clockwise directions are simultaneously excited by perpendicularly injecting the light from the single-mode-fiber (SMF) core into a polymeric microsphere

We propose and experimentally demonstrate a novel design approach for scalable 3-port and 4-port mode insensitive multimode switching matrices for the first two quasi-transverse electric (TE) modes. The mode insensitive phase shifter ensures less power consumption for simultaneous multimode signal transmission in a mode division multiplexing (MDM) network. At 1550 nm, the 3-port switch exhibits approximately

We propose a fast circuit scheduling algorithm capable of supporting optical switch with microsecond-scale switching delays. By simultaneously calculating the max-weighted matching for all optical switches, this scheduling algorithm releases the linear dependence of the time complexity upon the number of optical switches. Further by replacing the recursion and pointer operations with sorting and iteration

The whispering gallery modes (WGMs) are studied theoretically in a proposed magneto-optic (MO) silicon micro-ring resonator with a radial magnetic field. The dispersion relations between both the frequency and polarization of the resonant mode and the gyration coefficient are achieved through Finite-Element Method (FEM). Nonreciprocal polarization coupling is observed between the intrinsic quasi-TM

To support the emerging 5G applications and the 5G bearer networks, optical networks, as the critical infrastructure, are continuously evolving to be more dynamic and automatic. The vision of future autonomous networks with low link margins requires precise estimation/prediction of the quality of transmission (QoT) of optical links. Machine learning (ML) technologies provide promising solutions to

The high data rates enabled by free-space optical communication links and additional factors, such as the unregulated spectrum, make them an attractive solution in future geostationary feeder link applications with capacities beyond one Terabit per second. However, optical links through the atmosphere are heavily affected by atmospheric turbulence, leading to significant scintillation. Transmitter

Beam-steered infrared light can provide ultra-high wireless capacity to individual user devices for indoor communication systems. The optical beams used to obtain such high capacities are relatively narrow with the average beam divergence of less than 2.55°, hence an accurate localization system to pinpoint multiple user devices at the same time is required. In addition, an indoor communication should

A plasmon resonance sensor (SPR) based on D-shape photonic crystal fiber (PCF) is proposed to realize the simultaneous measurement of refractive index (RI) and temperature. The upper surface of the D-shape PCF is coated with gold film as a plasmon resonance excitation material for the detection of RI. An air hole near the fiber core is coated with gold film and filled with temperature-sensitive liquid

Orthogonal frequency-division multiplexing-based passive optical networks (OFDM-PON) can provide high spectral efficiency and flexible two-dimensional bandwidth allocation by assigning subcarriers (SCs) and time slots. The direct-modulation and direct-detection (DM-DD) OFDM with Hermitian symmetry constraint has simple hardware implementation, low cost, and low power consumption compared to coherent

Presents the table of contents for this issue of the publication.

Bit-error rate (BER) performance of free-space optical communication (FSO) systems is compromised by pointing errors. Few-mode fiber (FMF) based receiver emerges as a promising solution for FSO, because FMF can obtain high coupling efficiency in the presence of pointing errors. The high coupling efficiency allows FMF based system to achieve improved BER performance. In this letter, based on a simplified

A novel long-period fiber grating (LPFG) with arc grid having chirped radius is proposed and fabricated by CO 2 -laser writing. The radius of arc grid in this LPFG is linearly chirped along the light transmission direction, which provides a gradually changed refractive index modulation (RIM) higher than that of conventional planar grid, and causes multiple spectral dips corresponding different coupling

In the InP/InGaAs/InP PIN photodetector material growth, zinc is a normal doping ion and it has a high diffusion coefficient in InP and InGaAs. The Zn diffusion depth at the p-InP and intrinsic InGaAs boundary is critical for PIN photodiode high frequency characteristics. We control the p-InP Zn doping diffusion into intrinsic InGaAs layer by reducing the growth temperature of the p-type InP, decreasing

New pulse dynamics, which generates time-stretched dissipative soliton, has been analyzed in theory and demonstrated in experiment. With introducing non-equilibrium saturable absorber (SA) into the laser cavity, the time-dependent loss of SA can balance the intracavity dispersion, while gain and nonlinearity assist to stabilize the pulse. The pulse envelop is in exact sech-shape and the duration can

We propose an active region structure for a mid-infrared quantum cascade laser (QCL) where each wave function in the lower (upper) laser sub-band has a definite even (odd)-parity to increase the optical dipole matrix element $\langle \text {z}\rangle $ . The enhanced $\langle \text {z}\rangle $ leads to improving the optical gain of the QCL. We have demonstrated a $\lambda {\sim 7.5~\mu \text {m}}$

We report a wavelength-tunable high-repetition-rate passively Q-switched fluoride fiber laser around $3~\mu \text{m}$ by using Ti 3 C 2 T x MXene as saturable absorber (SA). The Ti 3 C 2 T x MXene was synthesized by selectively etching aluminum layers in Ti 3 AlC 2 . The modulation depth, non-saturation loss and saturation fluence of the SA at 2866 nm were measured to be 43.10%, 25.16%, and 0.50 mJ

A compact and label-free biosensor based on coreless-fiber-coupled microcavity is proposed and experimentally demonstrated for bovine serum albumin (BSA) detection. The microcavity is fabricated in a coreless fiber by on-line fiber cutting-welding micromachining. Experimental results show that the BSA samples with different concentration and refractive index ranging from 1.3344 to 1.3349 are clearly

A relationship between irradiance and the current needed to maintain the bias voltage applied to a silicon photomultiplier (SiPM) is shown to agree with experimental data. In addition to showing the saturation of the SiPMs response this relationship can be used to determine the power consumed by an SiPM. In addition, results are presented which show that, because of its higher maximum photon count

Optoelectronic feedback on a laser diode is demonstrated to generate two distinct modes of periodic pulse-train formation depending on the injection current $J$ of the laser leading to microwave combs in two distinct regimes. For $J$ close to the threshold current $J_{th}$ , the pulse repetition rate $f_{\mathrm{ rep}}$ is the inverse of the loop delay. This behavior is attributed to feedback-induced

Phosphor-in-glass (PiG) based white light-emitting diodes (WLEDs) are considered as the efficient light source for high-power white lighting due to their highly thermal stability. However, the low color rendering and poor color uniformity limits their actual applications. In this work, a PiG coated with red phosphor lens (PiG-RPL) structure was proposed to enhance the color rendering and color uniformity

We develop a ‘perfect’ design for PAM4 Segmented Mach-Zehnder Modulators (SEMZM), featuring a fully linear (uniform) optical DAC (oDAC) staircase (i.e., having equi-spaced PAM4 levels) and no intrinsic modulation loss (the qualifier ‘perfect’ pertains to ideal conditions, barring optical excess losses and other impairments). This is achieved by leveraging our recently introduced maximin optimization

We propose and demonstrate a $1\times2$ power splitter enabling arbitrary power splitting ratios. The device is based on a directional coupler with subwavelength structure in the coupling region and a trapezoid-structure in one arm. The measurement shows that arbitrary power splitting ratios, equal to 50:50, 60:40, 70:30, 80:20 and 90:10, can be obtained over an >80 nm bandwidth with an excess loss

In this work, we designed and fabricated a dual-mode switch based on triple-waveguide couplers and two thermal phase shifters, and demonstrated the first silicon-integrated mode division multiplexing (MDM) switching network for $2-\mu \text{m}$ waveband. The proposed dual-mode switch shows < 2.6 dB insertion loss, <−20 dB inter-mode crosstalk at 1960 nm, with broadband operation over 100 nm. The experimental

In multi-chip integrated photonic micro-systems, it is important to protect the laser source from reflection because the semiconductor laser is sensitive to the back reflection induced by the roughness of the waveguide sidewall or other on-chip optical structures. In order to maintain the stable operation of the light source, an additional micro-ring resonator coupled with the laser source is design

In this letter, a novel acousto-optical (AO) Q-switch is designed by using $\alpha $ -BaTeMo $_{\mathbf {2}}~\text{O}_{\mathbf {9}}$ crystal grown by the flux method. The acousto-optical modulator (AOM) exhibits a high polarization extinction ratio of 65 dB with a rise time of 32.8 ns and insertion loss of 3.66 dB. An actively Q-switched ytterbium doped all fiber laser at 1035 nm is successfully realized

Results of an investigation into the performance of a wide field of view silicon photomultiplier (SiPM) receiver under ambient light are reported. During these investigations a new form of inter-symbol interference (ISI) was discovered, which can be attributed to saturation of the SiPM. This new form of ISI means that using decision feedback equalization (DFE) improves the receiver’s performance at

We experimentally demonstrate Kerr optical frequency combs (OFCs) with mode spacing of 1, 2, 3, 5, 6, and 8 free spectral ranges (FSRs) corresponding to 0.4, 0.8, 1.2, 2, 2.4, and 3.2 THz, respectively, in silica microspheres pumped by CW C-band lasers in the anomalous dispersion range. Experimental realizations are based on using standard telecom equipment and components such as SMF-28e fiber for

A photonics system for baseband-free arbitrary-phase-coded microwave waveform pulse (APCMWP) generation is proposed and demonstrated. The proposed system realizes the generation of APCMWP, and further solves the baseband components problem in the pulsed process. The system uses a polarization-multiplexing dual-drive Mach–Zehnder modulator (PM-DMZM) and an optical band pass filter (OBPF) to obtain a

The perturbation-based nonlinearity compensation (NLC) method is considered in conjunction with a forward error correction (FEC) code that is capable of detecting block errors. The FEC decoding is performed prior to the NLC, and NLC is then performed only for blocks, that could not be decoded correctly. The total NLC complexity is thus dramatically reduced to down to 1% in some cases w.r.t. the standard

Various neural network (NN)-based equalizers have been proposed as effective digital signal processing (DSP) tools for short-reach optical direct detection (DD) communication systems. However, they are mainly designed for solving nonlinear problems due to the intrinsic nonlinear activation function. In this letter, we propose novel DSP schemes to deal with both linear and nonlinear impairments in short-reach

High-performance long-wavelength InAs/GaSb superlattice infrared photodetectors grown by metal-organic chemical vapor deposition are reported. “Diffusion-limited” behavior has been achieved for three devices with different doping concentration of the absorbers. Increasing the absorber doping concentration from $ 5\times 10^{15}$ to $ 5\times 10^{16}\mathrm {cm}^{-3}$ causes reduction of the dark current

We report a novel photonic scheme to generate binary phase-coded microwave signals by using two cascaded phase modulators (PMs) based on a Fourier domain mode-locked (FDML) optoelectronic oscillator (OEO). The first PM is driven by a series of electrical coding signals to modulate the phase of the optical carrier. The second PM is a construction of the FDML OEO, which realizes phase-modulation to

Phase manipulation is crucial for radio frequency (RF) and optical signal processing. In this work, we introduce an interferometric phase-reduction scheme to flexibly suppress the phase change while simultaneously amplifying the signal. We develop a numerical model to evaluate the characteristics of this processing scheme. The concept is further demonstrated with a proof-of-principle experiment that

Multifunctional metasurfaces are attracting growing attentions due to the compactness and the flexibility in beam manipulation. A bi-functional metagrating capable of anomalous refraction and beam splitting via asymmetric diffraction is designed, 3D-printed and experimentally verified at 0.14 THz. The asymmetric diffraction behavior is well explained by the excitation-direction-dependent mode amplitude

Recently, neural network (NN) nonlinear equalizers which are expected to reduce computational complexity have attracted attention as fiber nonlinear compensation methods for coherent optical transmission systems. However, these fiber nonlinear compensation methods have problems that training of NN is not easy for long-distance transmission systems because of accumulated phase noise. In this letter

A face-pumped Nd:YAG slab laser with high-power output and temperature fluctuation adaptability is proposed and demonstrated for the first time. A two-dimensional (2D) vertical-cavity surface-emitting laser (VCSEL) array at 808 nm with a low wavelength shift coefficient is used as the pump source with a total pump power of 1.38 kW. The array is cooled by a double-layer vascularized macro-channel heat

A novel sensitivity enhanced strain sensor based on two-arm Vernier Effect is proposed and demonstrated. This sensor is prepared by pasting two in-line Fabry Perot interferometers(FPIs) in cross configuration to a diamond metal frame. Because of the contribution of the FPI in vertical axis, it has a greater magnification factor M’ compared to traditional sensors based on Vernier Effect. The structure

A broadband vibration sensor using reflected excessively tilted fiber grating (ExTFG) with clamped beam was proposed. The two ends of reflected ExTFG were fixed, and the fiber grating part was suspended, thus forming a clamped beam structure. The resonance frequency and vibration mode of the proposed sensor were calculated and analyzed by numerical calculation and software simulation. Axial strain

In this letter, a novel physical layer encryption method based on digital chaos is proposed for the security in high-speed intensity modulation and direct detection (IM/DD) discrete multi-tone (DMT) transmission system. In the proposed encryption scheme, a random interleaving method is used, which further enhances the ability to encrypt the quadrature amplitude modulation (QAM) constellation and improves

We propose and experimentally demonstrate a centralized PON monitoring scheme using the reflection spectrum of a single fiber Bragg grating. Each fiber Bragg grating used in the scheme adopts different central reflection wavelength or 3-dB reflection bandwidth. The unique reflection spectrum is generated after each fiber Bragg grating used is interrogated by a broadband probe source. These generated

This letter demonstrates a tunable multi-band linear frequency modulation (LFM) signal with improved and unidentical bandwidths subjected to optical injection in a distributed-feedback (DFB) laser. In the proposed scheme, an optical beam is divided into two paths, one modulating with a baseband LFM signal and another with a power-varying signal. The basic principle of the proposed scheme is the optical

The challenge of asymmetric bidirectional optical wireless communication is majority resulted from the power shortage of uplink transmission, since it is double the downlink transmission distance. In this research, a wavelength tunable self-injection locking (SIL) system based on free-space configuration for uplink transmission in a modulated retroreflector based asymmetric bidirectional optical wireless

Bending the axis of an optical directional coupler can result in phase mismatch between the evanescently coupled waveguides. Using a quadratic bending profile, we realize the phase mismatch with a sign flip scheme for robust light coupling between the waveguides. We derive an analytical solution for the coupling scheme and show its robustness against parameter variations. Beam propagation method solution

This work reports a Mg (130 nm)/Al (50 nm) bilayer to realize high-reflectivity ohmic contact for n-GaN. The contact resistivity of $3.75\times 10 ^{ {-4}} \Omega \cdot $ cm $^{ {2}}$ with Mg/Al contact was achieved after annealing at 250 °C in ambient Ar for 1 min. The specific contact resistivity was found to change moderately when the annealing temperature was below 400 °C, but the ohmic characteristics

With the aim of using a single laser per transceiver in single fiber splitter-based passive optical networks (PON) with coherent homodyne receivers, we apply wavelength shifting in an ultra-dense wavelength division multiplexing (UD-WDM) scheme. The studied architecture is based on a dual-parallel Mach-Zehnder Modulator (DP-MZM) operating in carrier-suppressed single-sideband (CS-SSB). In this configuration

Based on several centimeters long heavily Tm 3+ -doped germanate fibers (TGFs) and in-band-pumped technique, a short-wavelength distribute Bragg reflector (DBR) single-frequency fiber laser (SFFL) emitting at $1.7~\mu \text{m}$ is investigated experimentally. A stable single-longitudinal-mode laser output with a signal-to-noise ratio of greater than 60 dB and an operation wavelength of 1727 nm is realized

We propose and demonstrate an optical fiber vector curvature sensor based on a long-period fiber grating (LPFG) inscribed in Panda type polarization-maintaining fiber (PMF) using CO 2 -laser heating and tapering system. The uniform heating approach removes the necessity of CO 2 -laser exposure alignment along the axis of PMFs during grating fabrication. A serial of PMF-LPFGs with grating period from

In this letter, high-order mode dispersion of a novel spoof surface plasmon polariton (SSPP) unit cell is reported, which has excellent bandpass propagation feature. Its asymptotic frequency and intersection frequency with light line can be independently manipulated by changing the geometric parameters of the slot in proposed SSPP unit cell. In order to validate the feasibility of high-order mode of

A technique for multi-band generation is investigated to simultaneously achieve phase-matching in multiple second-order nonlinear processes. By coupling a near-infrared excitation pulse into a LiNbO 3 planar waveguiding platform, modal phase-matched second harmonic radiation is generated at wavelengths of 403 ± 0.6 nm and Cherenkov-emitted terahertz radiation is generated at frequencies up to ~3.5

In this letter, we proposed an innovative laser self-mixing interferometer (SMI) with a reflection-type two-dimensional (2D) grating for three-dimensional (3D) dynamic displacement sensing. When the beams emitted by three lasers are incident on a reflective 2D grating with auto-collimation diffraction angles, the diffracted beams will return into the lasers along the original path, thus generating

Two new dynamic-state switching phenomena are experimentally observed in a vertical-cavity surface-emitting laser with polarization-preserved external-cavity optical feedback. One is switching between a steady state and a quasi-periodic state, and the other is switching between two different steady states. Both switching phenomena occur in the same polarization and the switching period is equal to

This paper proposes a novel approach and apparatus along with its calibration method to use the digital predistortion (DPD) technique in radio-over fiber (RoF) cloud RAN (C-RAN) transmitters that encompass physically spaced central baseband unit (C-BBU) and remote radio head (RRH). The proposed approach requires a calibrated observation path (COP) connecting the RRH to the BBU to mitigate any hardware

This research investigates and demonstrates a unique configuration of a multiwavelength fiber ring laser covering far L and U bands by employing a booster optical amplifier (BOA), a stabilizer beam, and a Mach-Zehnder interferometer (MZI) in a dual cavity arrangement. By reducing the loss in the central cavity from 10 to 0 dB, the number of generated lasing wavelengths can be increased from 15 to 30

Post-processing is an essential step towards the practical deployment of physical-layer secure key distribution (SKD) in classical fiber channels. However, the comparison and combination of different post-processing methods are not explored yet. Here, we fully evaluate the post-processing protocol and analyze various combinations of quantization and information reconciliation (IR), and present the

The performances of enhanced micro-ring resonators on a silicon on insulator platform are reported. The ring resonators are composed using four low-loss advanced bends with $1\mu \text{m}$ -straight waveguides between the bends. The losses of advanced bends are nearly ten and fifteen times lower than those of normal bends when radii of bends are 2 and $3\mu \text{m}$ , respectively. The effective radii

We demonstrated a novel silicon photonic platform constituting a D-shaped silicon cored fiber (SCF) for Schottky photodetector (PD). By using a handheld polishing machine, D-shaped SCFs can be fabricated in a fast and simple way. D-shaped SCFs offer stable platforms for traditional semiconductor processing and we show that Schottky PDs could be easily made on the fibers. Experiment results confirm

We propose and numerically investigate the use of birefringent vertical-cavity surface-emitting lasers (VCSELs) under the injection and modulation of spin polarized electrons for application to analog radio over fiber (RoF) systems. Injection current and electron spin polarization in a birefringent VCSEL are individually modulated for generating data signals and a millimeter-wave carrier and a polarizer