Search Results (58)

Terahertz (THz) frequencies, spanning from 0.1 to 1 THz, are poised to play a pivotal role in the development of future 6G wireless communication systems. These systems aim to utilize photonic technologies to enable ultra-high data rates—on the order of terabits per second—while maintaining low latency and high efficiency. In this work, we present a novel photonic method for generating sub-THz vector signals within the THz band, employing a semiconductor optical amplifier (SOA) and phase modulator (PM) to create an optical frequency comb, combined with in-phase and quadrature (IQ) modulation techniques. We demonstrate, both through simulation and experimental setup, the generation and successful transmission of a 0.1 THz vector. The process involves driving the PM with a 12.5 GHz radio frequency signal to produce the optical comb; then, heterodyne beating in a uni-traveling carrier photodiode (UTC-PD) generates the 0.1 THz radio frequency signal. This signal is transmitted over distances of up to 30 km using single-mode fiber. The resulting 0.1 THz electrical vector signal, modulated with quadrature phase shift keying (QPSK), achieves a bit error ratio (BER) below the hard-decision forward error correction (HD-FEC) threshold of ${3.8 \times 10}^{-3}$. To the best of our knowledge, this is the first experimental demonstration of a 0.1 THz photonic vector THz wave based on an SOA and a simple PM-driven optical frequency comb. Full article

Encryption and decryption are essential components in signal processing and optical communication systems, providing data confidentiality, integrity, and secure high-speed transmission. We present a novel design and simulation of an all-optical encryption and decryption system operating at 120 Gb/s using carrier reservoir semiconductor optical amplifiers (CR-SOAs) embedded in Mach–Zehnder interferometers (MZIs). The architecture relies on two consecutive exclusive-OR (XOR) logic gates, implemented through phase-sensitive interference in the CR-SOA-MZI structure. The first XOR gate performs encryption by combining the input data signal with a secure optical key, while the second gate decrypts the encoded signal using the same key. The fast gain recovery and efficient carrier dynamics of CR-SOAs enable a high-speed, low-latency operation suitable for modern photonic networks. The system is modeled and simulated using Mathematica Wolfram, and the output quality factors of the encrypted and decrypted signals are found to be 28.57 and 14.48, respectively, confirming excellent signal integrity and logic performance. The influence of key operating parameters, including the impact of amplified spontaneous emission noise, on system behavior is also examined. This work highlights the potential of CR-SOA-MZI-based designs for scalable, ultrafast, and energy-efficient all-optical security applications. Full article

In this paper, we present a directly modulated laser (DML) using a partially corrugated grating (PCG) and integrated with a semiconductor optical amplifier (SOA). The influence of the quasi-high-pass filter properties of the SOA on the bandwidth was explored, resulting in high optical power output at lower current levels, with a bandwidth surpassing 25 GHz and an output power above 25 mW. The PCG design boosts the lasing mode’s resistance to random phase fluctuations at the rear facet, hence boosting the mode stability of the laser with a side-mode suppression ratio (SMSR) of over 44 dB. Furthermore, we performed back-to-back (BTB) 26.5625 Gbps NRZ data transmission experiments at room temperature (25 °C) with a modulation current of 60 mA. The results reveal that the transmitter and dispersion eye closure (TDEC) of the fabricated DML is lower than that of a conventional laser when the SOA area current reaches a specific threshold, demonstrating the enhanced signal transmission capabilities of our design. This laser structure offers a fresh strategy for the development of high-power, high-speed DMLs. Full article

All-optical encoders and comparators are essential components for high-speed optical computing, enabling ultra-fast data processing with minimal latency and low power consumption. This paper presents a numerical analysis of an all-optical encoder and comparator architecture operating at 120 Gb/s, based on carrier reservoir semiconductor optical amplifier-assisted Mach–Zehnder interferometers (CR-SOA-MZIs). Building upon our previous work on all-optical arithmetic circuits, this study extends the application of CR-SOA-MZI structures to implement five key logic operations between two input signals (A and B): $\overline{\mathrm{A}}\mathrm{B}$, $\mathrm{A}\overline{\mathrm{B}}$, AB (AND), $\overline{\mathrm{A}}\hspace{0.17em}\overline{\mathrm{B}}$ (NOR), and AB + $\overline{\mathrm{A}}\hspace{0.17em}\overline{\mathrm{B}}$ (XNOR). The performance of these logic gates is evaluated using the quality factor (QF), yielding values of 17.56, 17.04, 19.05, 10.95, and 8.33, respectively. We investigate the impact of critical design parameters on the accuracy and stability of the logic outputs, confirming the feasibility of high-speed operation with robust signal integrity. These results support the viability of CR-SOA-MZI-based configurations for future all-optical logic circuits, offering promising potential for advanced optical computing and next-generation photonic information processing systems. Full article

In this study, we propose a novel design for a NAND gate using a single semiconductor optical amplifier (SOA) followed by a delay interferometer (DI). This streamlined configuration significantly reduces complexity and cost compared to conventional methods, which typically require cascading multiple SOA-Mach–Zehnder interferometers (SOA-MZIs) for NAND gate implementation. Our approach directly generates the NAND logic output with a single SOA and DI, simplifying the overall design. The gate’s performance is evaluated at 80 Gb/s, achieving a high-quality factor (QF) of 10.75. We also analyze the impact of key parameters to optimize the gate’s functionality. Furthermore, we assess the effect of amplified spontaneous emission on the QF, providing a more comprehensive evaluation of the system’s performance. This research paves the way for more efficient and cost-effective complex optical logic circuit solutions. Full article

An all-optical crosstalk suppression scheme is desirable for wavelength and space division multiplexing optical networks by improving the performance of the corresponding nodes. We put forward a scheme comprising double-stage semiconductor optical amplifiers (SOAs) for wavelength-preserving crosstalk suppression. The wavelength position of the degenerate pump in the optical phase conjugation (OPC) is optimized for signal-to-crosstalk ratio (SXR) improvement. The crosstalk suppression performance of the double-stage SOA scheme for 20 Gb/s quadrature phase shift keying (QPSK) signals is investigated by means of simulations, including the input SXR range and the crosstalk wavelength deviation. For the case with identical-frequency crosstalk, the double-stage SOA scheme can achieve equivalent SXR improvement of 1.5 dB for an input SXR of 10 dB. Thus, the double-stage SOA scheme proposed here is more suitable for few-mode fiber systems and networks. Full article

This paper introduces a semiconductor optical amplifier (SOA) with high power and narrow linewidth broadening achieved through active region mode control. By integrating mode control with broad-spectrum epitaxial material design, the device achieves high gain, high power, and wide band output. At a wavelength of 1550 nm and an ambient temperature of 20 °C, the output power reaches 757 mW when the input power is 25 mW, and the gain is 21.92 dB when the input power is 4 mW. The 3 dB gain bandwidth is 88 nm, and the linewidth expansion of the input laser after amplification through the SOA is only 1.031 times. The device strikes a balance between high gain and high power, offering a new amplifier option for long-range light detection and ranging (LiDAR). Full article

This paper demonstrates a five-layer InAs/InP quantum-dash semiconductor optical amplifier (QDash-SOA), which will be integrated into microwave-photonic on-chip devices for millimeter-wave (mmWave) over fibre wireless networking systems. A thorough investigation of the QDash-SOA is conducted regarding its communication performance at different temperatures, bias currents, and input powers. The investigation shows a fibre-to-fibre (FtF) small-signal gain of 18.79 dB and a noise figure of 6.3 dB. In a common application with a 300 mA bias current and 25 °C temperature, the peak FtF gain is located at 1507.8 nm, which is 17.68 dB, with 3 dB gain bandwidth of 56.6 nm. Furthermore, the QDash-SOA is verified in a mmWave radio-over-fibre link with QAM (32 Gb/s 64-QAM 4-GBaud) and OFDM (250 MHz 64-QAM) signals. The average error vector magnitude of the QAM and OFDM signals after a 2 m wireless link could be as low as 8.29% and 6.78%, respectively. These findings highlight the QDash-SOA’s potential as a key amplifying component in future integrated microwave-photonic on-chip devices. Full article

In this paper a novel optical vector network analyzer (OVNA) utilizing a distributed feedback semiconductor optical amplifier (DFB-SOA) is introduced. The proposed OVNA is implemented by converting the transmission response of the optical device under test (ODUT) into the electrical domain. The main principle of the OVNA is predicated on the optical carrier restoration facilitated by the wavelength-selective amplification attribute of the DFB-SOA. The implemented OVNA effectively determined the transmission spectrum of an optical filter possessing a passband of 9-GHz bandwidth, achieving a commendable resolution of 25 MHz in the measurement process. The dynamic range of the OVNA can be broadened by adjust the driven current under the DFB-SOA. Additionally, the detection range of our system can be expanded through the utilization of broadband optoelectronic devices. Furthermore, the OVNA possesses considerable potential for integration onto a single chip. Full article

Leveraging the rapid carrier recovery times and minimal polarization sensitivity of carrier-reservoir semiconductor optical amplifiers (CR-SOAs), this study embeds them in a Mach–Zehnder interferometer (MZI) setup to emulate a 2x1 multiplexer (MUX) operating at 120 Gb/s. The focus is on incorporating AND logic gate functionalities into the CR-SOAs-based MZI structure to facilitate high-quality multiplexing. The proposed methodology utilizes the intrinsic gain and phase modulation capabilities of CR-SOAs-based MZI to effectively manipulate data streams. This innovative approach capitalizes on the unique properties of CR-SOAs, such as fast response times and low polarization sensitivity, to achieve optimal signal transmission quality and efficient multiplexing. To assess MUX performance, a quality factor metric is introduced as a comprehensive measure of signal integrity. Through exhaustive simulations and meticulous analysis, the study demonstrates the feasibility of achieving the desired data rate while maintaining superior signal transmission quality. The results underscore the efficacy of CR-SOAs-based MZI as versatile modules for high-speed multiplexing applications, offering unparalleled performance and efficiency. This research represents a significant advancement in understanding optical communication systems and provides valuable insights for optimizing signal quality and mitigating interference in practical real-world scenarios. Full article

This research explores the forefront of all-optical data processing systems through the utilization of carrier reservoir semiconductor optical amplifiers (CR-SOAs). Recent advancements have showcased the successful design and implementation of CR-SOA-based combinational systems, incorporating pivotal elements like half adders, half subtractors, digital-to-analog converters, latches, header recognition, and header processors. These breakthroughs signify a significant stride towards the realization of faster and more efficient optical logic systems. This study delves into the distinctive characteristics of CR-SOA-based Mach–Zehnder interferometer (MZI) functioning as an XOR gate, emphasizing their transformative potential in information processing. By integrating them into the architecture of an all-optical 4-bit parity generator and checker, the research underscores the practicality of CR-SOA technology in all-optical processing, offering unprecedented speeds and facilitating enhanced data processing capabilities at a remarkable speed of 120 Gb/s return-to-zero pulses. In evaluating the performance of the proposed scheme, the research employs the quality factor metric. This assessment not only yields quantitative insights into the efficacy of CR-SOA-based logic systems but also establishes a critical benchmark for their practical implementation. The study further explores the impact of key data signals and CR-SOA parameters on this metric. The outcomes demonstrate the ability of the CR-SOA-based MZI to cascade and form more intricate logic circuits, thereby highlighting the versatility and potential of this innovative approach in advancing the landscape of all-optical data processing. Full article

Polarization-insensitive semiconductor optical amplifiers (SOAs) in all-optical networks can improve the signal-light quality and transmission rate. Herein, to reduce the gain sensitivity to polarization, a multi-quantum-well SOA in the 1550 nm band is designed, simulated, and developed. The active region mainly comprises the quaternary compound InGaAlAs, as differences in the potential barriers and wells of the components cause lattice mismatch. Consequently, a strained quantum well is generated, providing the SOA with gain insensitivity to the polarization state of light. In simulations, the SOA with ridge widths of 4 µm, 5 µm, and 6 µm is investigated. A 3 dB gain bandwidth of >140 nm is achieved with a 4 µm ridge width, whereas a 6 µm ridge width provides more output power and gain. The saturated output power is 150 mW (21.76 dB gain) at an input power of 0 dBm but increases to 233 mW (13.67 dB gain) at an input power of 10 dBm. The polarization sensitivity is <3 dBm at −20 dBm. This design, which achieves low polarization sensitivity, a wide gain bandwidth, and high gain, will be applicable in a wide range of fields following further optimization. Full article

The paper presents a wide-bandwidth, low-polarization semiconductor optical amplifier (SOA) based on strained quantum wells. By enhancing the material gain of quantum wells for TM modes, we have extended the gain bandwidth of the SOA while reducing its polarization sensitivity. Through a combination of tilted waveguide design and cavity surface optical thin film design, we have effectively reduced the cavity surface reflectance of the SOA, thus decreasing device transmission losses and noise figure. At a wavelength of 1550 nm and a drive current of 1.4 A, the output power can reach 188 mW, with a small signal gain of 36.4 dB and a 3 dB gain bandwidth of 128 nm. The linewidth broadening is only 1.032 times. The polarization-dependent gain of the SOA is below 1.4 dB, and the noise figure is below 5.5 dB. The device employs only I-line lithography technology, offering simple fabrication processes and low costs yet delivering outstanding and stable performance. The designed SOA achieves wide gain bandwidth, high gain, low polarization sensitivity, low linewidth broadening, and low noise, promising significant applications in the wide-bandwidth optical communication field across the S + C + L bands. Full article

We designed a narrow-linewidth external-cavity hybrid laser leveraging a silicon-on-insulator triple Euler gradient resonant ring. The laser’s outer cavity incorporates a compact, high-Q resonant ring with low loss. The straight waveguide part of the resonant ring adopts a width of 1.6 μm to ensure low loss transmission. The curved section is designed as an Euler gradient curved waveguide, which is beneficial for low loss and stable single-mode transmission. The design features an effective bending radius of only 26.35 μm, which significantly improves the compactness of the resonant ring and, in turn, reduces the overall footprint of the outer cavity chip. To bolster the laser power and cater to the varying shapes of semiconductor optical amplifier (SOA) spots, we designed a multi-tip edge coupler. Theoretical analysis indicates that this edge coupler can achieve an optical coupling efficiency of 85%. It also reveals that the edge coupler provides 3 dB vertical and horizontal alignment tolerances of 0.76 μm and 2.4 μm, respectively, for a spot with a beam waist radius of 1.98 μm × 0.99 μm. The outer cavity, designed with an Euler gradient micro-ring, can achieve a side-mode suppression ratio (SMSR) of 30 dB within a tuning range of 100 nm, with a round-trip loss of the entire cavity at 1.12 dB, and an expected theoretical laser linewidth of 300 Hz. Full article

A time-differential (TD) Brillouin optical correlation domain analysis (BOCDA) sensor system was applied to measure the Brillouin gain spectrum of a 1 km long sensing optical fiber. The optical delay line used in all BOCDA measurement systems was eliminated in the TD-BOCDA system by using a bit-delayed modulation relationship between the probe and pump lightwaves. These lightwaves were phase modulated using 2¹⁶-1 pseudo-random binary sequence codes at 5 Gbps. A 2 cm dispersion-shifted fiber placed at the end of the 1 km optical fiber was distinctly identified by the Brillouin frequency extracted from the Brillouin gain spectrum measurement. To investigate the measurement stability of the TD-BOCDA system, experiments were conducted under two different pumping conditions. A semiconductor optical amplifier (SOA) and an intensity modulator (MOD) were compared for the pump chopper used in the TD-BOCDA system to detect the extinction ratio of the pump and the resulting noise in the Brillouin gain measurement. The stability of the Brillouin frequency measurement from the Brillouin gain spectrum in the TD-BOCDA system was investigated by increasing the average value of the measurement using either the SOA or MOD. The repeated-measurement deviation of the system with the SOA was only half of the deviation observed in the system with the MOD. The performance of TD-BOCDA is equivalent to or better than that of conventional BOCDAs in terms of measurement reliability. Moreover, TD-BOCDA is free from the drawbacks of traditional BOCDA, which uses time-delayed fibers and varies the bit rates. Full article