Extinction Ratio Of Modulator Research Articles

Nested hollow-core anti-resonant fiber with elliptical cladding for 2 µm laser transmission

In this work, a nested hollow-core anti-resonant fiber (HC-ARF) with an elliptical cladding for high-power lasers for 2 µm laser transmission was proposed and theoretically investigated. The dual-layer elliptical tubes nested within the fiber enable the low-loss single-mode transmission. The finite element method (FEM) was employed to analyze and optimize the structure of fiber, with a total loss of less than 5 × 10−4 dB/m across the wavelength range of 1920nm to 2040nm. An extremely low loss of 1.22 × 10−5 dB/m at 1948nm was realized. A high-order mode extinction ratio (HOMER) exceeding 3 × 104 was maintained across a significant bandwidth and a size tolerance ratio under 15%. Furthermore, a low loss of 5 × 10−5 dB/m at 1948nm with a bending radius over 15 cm was obtained, indicating high bending resistance. It was demonstrated that the proposed fiber has exceptional transmission performance for 2 µm laser transmission.

Universal silicon ring resonator for error-free transmission links

We report the design, fabrication, and characterization of a universal silicon PN junction ring resonator for C band error-free communication links operated up to 50 Gb/s with co-designed optical modulation and detection performance. The universal p-n junction ring device shows co-designed detection responsivity up to 0.84 A/W, in conjunction with a modulation efficiency of ∼4 V·mm and >8 dB optical modulation extinction ratio, enabling C band 50 Gb/s NRZ communication link with a bit error rate ≤3×10−12. Individually, the speed of modulation and detection is measured up to 112 Gb/s and 80 Gb/s, respectively. The principle of co-designing the PN junction ring modulator and detector performance required for error-free communication links can significantly ease the fabrication yield challenges of ring structures by reducing the number of types of devices. The principle can also be applied to O band wavelengths. To the best of our knowledge, for the first time, a device of this type has achieved both error-free modulation and detection operation up to 50 Gb/s in the C band individually or in conjugation as an error-free communication link, which paves the way to realize a >1.6 Tb/s all-silicon WDM-based error-free optical transceiver link in the future and is essential for future programmable photonics circuits.

Design and investigation of filterless sixtuple RoF upconversion system with improved sideband to carrier suppression ratio using MZM extinction ratio variance

Abstract In this work, millimeter wave generation of sixtuple frequency scheme using dual parallel Mach–Zehnder modulator configuration has been investigated. The proposed scheme is mathematically analyzed and its performance is evaluated using software optisystem v.18. The vital parameters of both Mach–Zehnder modulator and phase of radio frequency local oscillator are properly adjusted for upconversion of 10 GHz radio frequency drive signal into 60 GHz mm wave. The impact of Mach–Zehnder modulator extinction ratio on radio frequency sideband suppression ratio, optical sideband suppression ratio and third sideband to carrier suppression ratio, is evaluated. An improved 63 dB third sideband to carrier suppression ratio is achieved at increased extinction ratio of Mach–Zehnder modulator. Impact of bias point drift and electrical phase shift on sideband suppression ratios are evaluated. Further, millimeter wave signal of 6–60 GHz tunability is realized by applying radio frequency local oscillator signal from 1 to 10 GHz.

Broadband Silver Ribbon-Embedded Graphene and h-BN Optical Modulator With High Modulation Depth and Extinction Ratio and Low Switching Voltage

Broadband Silver Ribbon-Embedded Graphene and h-BN Optical Modulator With High Modulation Depth and Extinction Ratio and Low Switching Voltage

Optical mode-controlled topological edge state in waveguide lattice

Abstract Topological edge state (TES) has emerged as a significant research focus in photonics due to its unique property of unidirectional transmission. This feature provides immunity to certain structural disorders or perturbations, greatly improving the robustness of photonic systems and enabling various applications such as optical isolation and topological lasers. Nevertheless, most of current researches focus on the fixed generated TES with no means to control, leaving untapped potential for manipulating the TES through specific methods. In this work, we propose a topological Su–Schriffer–Heeger (SSH) waveguides-lattice scheme that enables the controllable TES without changing the topological phase of the system. Light is selectively localized at the edges of the SSH waveguide lattice, which is determined by the special waveguide modes. Eventually, achieving an effective mode splitter. To validate our proposal, we further demonstrate such mode-controlled TES with a fabricated on-chip device in experiment. The experimentally tested results confirm a successful separation of the waveguide modes with the mode extinction ratio of approximately 10 dB in each channel near the wavelength of 1550 nm. This scheme presents a promising approach for manipulating the TES in photonic systems, thereby facilitating the design of optical controllable topological photonic devices.

Filterless Frequency Octupling Microwave Photonic Phase Shifter Based on Cascaded Mach–Zehnder Modulators

ABSTRACT In this paper, we propose a microwave photonic phase shifter (MPPS) without optical filtering to generate a frequency octupling microwave photonic (MWP) signal with 360º phase-shifting based on two cascaded Mach–Zehnder modulators (MZMs). Theoretical analysis is given to realize the high-quality frequency octupling MPPS by eliminating the undesired optical carrier and sidebands using an optical coupler (OC). Simulations show that the generated MMW signal has an electrical spurious suppression ratio (ESSR) higher than 33 dB. The impact of the non-ideal modulation index, extinction ratio, and phase drift is discussed and analyzed. Furthermore, the influence of different center frequencies, power, and linewidths of the laser is also analyzed.

Multi-layered cladding based ultra-low loss, single mode antiresonant hollow core fibers

In reality, an efficient platform for high-power laser delivery is highly important, which can be justified by readily available fiber lasers, and hollow-core fiber can be the best platform for guiding high optical power over long distances. The constraints include designing new cladding geometry, which may lead to a higher laser induced damage threshold in the fiber’s structure, having low losses along with a single mode nature. This article reports a new antiresonant fiber that has a hollow core and a triple-layered cladding configuration with only circular tube elements. The effects of multiple layers corresponding to the number of tube rings in the cladding geometry are well explored, which leads to understanding the physical insight of inter-layers. In comparison to double-layered cladding elements fiber, the proposed fiber significantly reduces loss by an order of two and reveals a minimum leakage loss of 5.82 × 10−5 dB/km at the chosen wavelength of 1.06 µm through the proper arrangement of cladding elements. We achieved a maximal higher order mode extinction ratio of about 104 (indicates the excellent single mode properties) and comparatively a little bending-induced loss of 9.00 × 10−4 dB/km, when the radius of bending is 14 cm. As a result, our studies on new multilayer fiber designs are not only useful for delivering high laser power but also serve as guidelines for the experimental realization of future multilayered cladding fibers.

Double nested dual-core negative curvature fiber polarization beam splitter

In this paper, a polarization beam splitter（PBS） based on double nested dual-core negative-curvature fiber (DNHC-NCF) is designed. Two hollow cores are constructed by eight double nested cladding tubes arranged at certain angles. The influences of structural parameters on the performances of the DNHC-NCF PBS have been studied by using the finite element method (FEM). According to the simulation results, the structure of the proposed DNHC-NCF PBS is optimized. The final results indicate that the length of the proposed DNHC-NCF PBS is 1.38 cm and the extinction ratio (ER) is less than −20 dB in the wavelength range of 1.48–1.80 µm (320 nm, covers S + C + L + U bands). Besides, the higher order mode extinction ratio (HOMER) in the wavelength range of 1.3–1.71 µm is greater than 100, showing good single-mode characteristic as well. It is believed that the proposed double nested dual-core negative curvature fiber polarization beam splitter will have important applications in the fields of optical communication system.

Single-polarization single-mode broadband ultra-low loss hollow-core anti-resonant fiber with nested double C-type cladding tubes

A novel five-tube nested double C-type single-polarization hollow-core anti-resonant fiber (HC-ARF) is proposed for single-polarization single-mode, ultra-low loss, and broadband characteristics. Different tube thicknesses are introduced along the orthogonal direction to couple the x-polarized fundamental mode (FM) to the silica modes (SMs). At the same time, the y-polarized FM is tightly bound in the core, achieving a high polarization extinction ratio (PER). In order to achieve large bandwidth, a layer of high-refractive-index silicon material is coated on the inner surface of the cladding tube. To the best of our knowledge, the proposed single-polarization HC-ARF has the highest PER at 1.55μm with a remarkable value of 162486 so far, while the y-polarized FM loss is only 1.4 × 10-3 dB/km. However, the single-polarization bandwidth remains limited. By optimizing the structural parameters on single-polarization bandwidth, the HC-ARF at 1.55μm for single-polarization single-mode transmission is obtained with a high-order mode extinction ratio (HOMER) and PER of 2891, 9531, respectively. In addition, a remarkably high single-polarization bandwidth of up to 150 nm is achieved with ultra-low confinement loss (CL) as low as 2.8 × 10-3 dB/km. Furthermore, the proposed fiber exhibits good bending characteristics, with a bending loss of 6.7 dB/km at the bending radius of 5 cm in the x-direction.

FPGA-based pulsed laser with high modulation depth from Mach-Zehnder electro-optic modulator and its application

Mach-Zehnder electro-optic modulator as the essential component of high-speed modulation in the optical fiber communication and sensing system, its stability control of operating bias-point plays a key role in determining the transmission signal quality. Based on the output characteristic principle of Mach-Zehnder electro-optic modulator, researches on its bias-point drifting for causing the reduction mechanism of modulation depth and extinction ratio are analyzed. Switching its internal state machine from FPGA is proposed to automatically adjust the bias voltage in real time realizing the operating bias-point control of Mach-Zehnder electro-optic modulator, which is studied through the theoretical investigation. A pulsed laser with the temperature sensing system of fiber Bragg grating ring-down cavity based on FPGA is established experimentally to demonstrate its effectiveness. The experimental results show the modulation depth and the extinction ratio of pulsed laser are improved by 40.45% and 32.85 dB, respectively. Output characteristic curve of the sensing system is optimized, which includes the phenomenon of initial curve rise of ring-down signals and the distortion of ring-down waveform are eliminated. The good linearity, repeatability, stability and accuracy of sensing system are investigated at the continuous variation temperature from −30℃ to 30℃.

Optimization of hollow-core fibers with elliptical tubes for improved single-mode guidance

Hollow core fibers with elliptical tubes offer more design flexibility and can achieve better performance compared to their circular counterparts. We optimize the elliptical tubes of a hollow-core fiber to achieve a higher order mode extinction ratio (HOMER) exceeding 5500 along with a confinement loss of 0.012 dB/m in the telecommunication band; 4.7×10−4 dB/m with HOMER > 4300 in the visible band. We also derive an empirical relation between the structural parameters to obtain avoided crossings between the core higher order modes and the cladding modes to achieve the best single-mode guidance, besides achieving minimum confinement loss for the fundamental mode. We investigate the effect of bends on not just the confinement loss, but also on the HOMER. We have also included the dispersion and fabrication tolerances. These fibers find applications in quantum communication, sensing, and high-power laser delivery.

Experimental demonstration of SNSPD-based free space optical communication with a high extinction ratio modulator

With the development of space technology, the amount of information transmission required by satellites and various spacecraft has increased exponentially. The use of optical communications is a means for future high-speed communications. Adopting superconducting nanowire single photon detectors (SNSPDs) as a receive detector can be capable of detecting signals on the photon scale, which has great application prospects in the field of deep-space optical communication for faint signal detection. However, the use of SNSPDs and high-peak-power optical pulse signals also place higher demands on the extinction ratio of modulators. Therefore, in this paper, we designed a high extinction ratio optical modulator, which adopts cascaded Mach-Zehnder modulators structure, and the static extinction ratio can be reached 77.5 dB. In addition, an SNSPD-based 3.4 km free space optical communication experiment is successfully carried out by using the modulator and a diffuse reflector plate.

Hollow-core pear-shaped conjoined-tube fiber with low loss in the ultraviolet band

PCTF (pear-shaped conjoined-tube fiber) is presented as a new ultraviolet (UV) guiding fiber with low loss. Results indicate that two PCTFs have better properties than that of previous studies in the UV band. The total loss of two PCTFs is less than 1 dB/km, and its bandwidth exceeds 150 nm between 0.2 and 0.4 μm. Furthermore, PCTF's single-mode performance is very promising, as evidenced by the higher-order mode extinction ratio (HOMER) over 103. The fabrication tolerance is discussed in this paper and results show that the tolerance is good enough to fabricate by normal fiber drawing process. This fiber is promising in applications for nonlinear optics, ultrafast optics, high power laser, and quantum optics.

Antiresonant fiber structures based on swarm intelligence design.

In this work, we obtained a new, to the best of our knowledge, structure of anti-resonant fiber (ARF) by an adaptive particle swarm optimization (PSO) algorithm. Different from the prior method of stacking elemental parts and optimizing parameters through experience or algorithm, we decompose some classic structures into points and optimize the positions of these points through swarm intelligence. The fiber structure is reconstructed by interpolation, and some new structures with low confinement loss (CL) and high higher order mode extinction ratio (HOMER) are obtained. These novel ARFs exhibit similar structural characteristics, and are named as "the bulb-shaped ARFs". Among these structures, the minimum achieved CL is 2.21 × 10-5dB/m at 1300 nm and the maximum achieved HOMER exceeds 14,000. This work provides a method with high degree of freedom in the design of non-uniform cross-section waveguides and helps to discover new fiber structures.

Mode-selective switch on silica-based PLC platform

Optical mode switch is a crucial component for the mode-division multiplexing (MDM) system. In this paper, we demonstrate a thermo-optical (TO) mode-selective switch on silica-based planar lightwave circuit (PLC) platform. The 2 × 1 thermo-optical (TO) mode-selective switch based on Mach–Zehnder interferometer consists of an adiabatic coupler and a symmetric Y-branch. The input optical mode E00 (E10) is converted to E10 (E00) mode while the light is coupled from different input ports by changing the working state of heater. With 2% index-contrast, a compact mode switch on silica-based PLC platform is fabricated. According to experimental results, the fabricated mode-selective switch shows an insertion loss lower than 5 dB and a mode extinction ratio higher than 24 dB for two modes at 1550 nm. The crosstalk is lower than −10.54 dB from 1500 nm to 1600 nm. The power consumption for two modes are 433.24 mW and 440.15 mW, respectively. The rise time and fall time of the switch are 560.9μs and 794.8μs.

Low-Loss Nodeless Conjoined-Tube Anti-Resonant Hollow-Core Fiber

We propose a novel nodeless conjoined-tube hollow-core fiber (CT-HCF) with elliptical arcs as negative curvature boundaries to limit the leakage of transmitted light. The cladding nodes are effectively eliminated by the attachment of arcs to the outermost dielectric tube. Numerical simulations performed using the full-vector finite element method show that a significant reduction in fiber loss over a wide bandwidth can be obtained. The confinement losses for the proposed fiber are two orders of magnitude lower than those obtained for a typical CT-HCF. The total loss, including confinement loss and surface scattering loss, is also investigated. The proposed fiber shows a loss of less than 0.1 dB/km for a bandwidth of 450 nm, with a minimum loss of 6.58·10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> dB/m at 1.45 μm. Moreover, the proposed fiber exhibits good single-mode performance, with the higher-order mode extinction ratio reaching a maximum value of 39341 at 1.7 μm.

Design of 2 μm Low-Loss Hollow-Core Anti-Resonant Fibers.

We systematically studied several of the most traditional hollow-core anti-resonant fiber (HC-ARF) structures, with the aim of achieving low confinement loss, single-mode performance, and high insensitivity to bending in the 2 µm band. Moreover, the propagation loss of fundamental mode (FM), higher-order mode (HOMs), and the higher-order mode extinction ratio (HOMER) under different geometric parameters were studied. Analysis showed that the confinement loss of the six-tube nodeless hollow-core anti-resonant fiber at 2 µm was 0.042 dB/km, and its higher-order mode extinction ratio was higher than 9000. At the same time, a confinement loss of 0.040 dB/km at 2 µm was achieved in the five-tube nodeless hollow-core anti-resonant fiber, and its higher-order mode extinction ratio was higher than 2700.

Thirty‐two‐tupling frequency millimeter‐wave generation based on eight Mach–Zehnder modulators connected in parallel

AbstractA new method is proposed to generate a 32‐tupling frequency millimeter wave (MMW) with eight Mach–Zehnder modulators (MZMs) connected in parallel. Theoretical analyses and simulation experiments are conducted. The optical sideband suppression ratio (OSSR) of the obtained ±16th order optical sidebands are 61.54 dB and 61.42 dB, and the radio frequency spurious suppression ratios (RFSSRs) of the generated 32‐tupling frequency MMW are 55.52 dB and 55.27 dB based on the theoretical analysis and simulation experiments, respectively; these outcomes verified the feasibility of the new method. The main parameters used to affect the stability of the generated signal are the modulation index and extinction ratio of MZM. Their effects on the OSSR and RFSSR of the generated signals are investigated when they deviate from their designed values. Compared with the other proposed methods for the generation of 32‐tupling frequency MMW by MZM, our method has the best spectral purity and stability, and it is expected to have important MMW over fiber applications.

Multi-nested antiresonant hollow-core fiber with ultralow loss and single-mode guidance.

We propose an antiresonant hollow-core fiber design that exhibits ultralow loss and exceptional single modedness at 1.55 µm. In this design, the confinement loss of less than 10-6 dB m-1 can be obtained with excellent bending performance even at a tight bending radius of 3 cm. At the same time, a record-high higher-order mode extinction ratio of 8 × 105 can be achieved in the geometry by inducing strong coupling between the higher-order core modes and cladding hole modes. These guiding properties make it an excellent candidate for applications in hollow-core fiber-enabled low-latency telecommunication systems.

All‐Optical Nonlinear Neuron Based on Metallic Quantum Wells

AbstractOptical nonlinear neuron, as an essential implementation method for optical interconnection, could greatly promote the development of optical neuron networks, which appears to be a promising alternative to electronic neural networks that are limited by computing speed and the end of Moore's law. However, restricted by weak nonlinearities, the modulation performance of optical nonlinear neuron networks is much lower compared to their electronic counterparts. Therefore, an effectual all‐optical nonlinear neuron is proposed by combining a double‐ring resonator with field‐enhancement and metallic quantum wells (MQWs) with a large Kerr nonlinear response. Based on the large and ultrafast Kerr nonlinearity provided by MQWs, the device can achieve a modulation extinction ratio of 18.78 dB and a transition rate of 13 GW cm−2 per 3 dB. The work may provide a new route for integrated, ultrafast, and high‐efficient optical nonlinear neurons for on‐chip neuron networks.