Showing papers on "Single-mode optical fiber published in 2020"

Hollow Core NANF with 0.28 dB/km Attenuation in the C and L Bands

Abstract: We report an effectively single-moded, 1.7km long hollow core Nested Antiresonant Nodeless Fiber (NANF) with record-low 0.28dB/km loss from 1510 to 1600nm, which further reduces the loss gap with standard all-glass single mode fibers.

Optical Fibre Capacity Optimisation via Continuous Bandwidth Amplification and Geometric Shaping

Abstract: The maximum data throughput in a single mode optical fibre is a function of both the signal bandwidth and the wavelength-dependent signal-to-noise ratio (SNR). In this paper, we investigate the use of hybrid discrete Raman & rare-earth doped fibre amplifiers to enable wide-band signal gain, without spectral gaps between amplification bands. We describe the widest continuous coherent transmission bandwidth experimentally demonstrated to date of 16.83 THz, achieved by simultaneously using the S-, C- and L-bands. The variation of fibre parameters over this bandwidth, together with the hybrid amplification method result in a significant SNR wavelength-dependence. To cope with this, the signal was optimised for each SNR, wavelength and transmission band. By using a system-tailored set of geometrically shaped constellations, we demonstrate the transmission of 660 $\times25$ GBd channels over 40 km, resulting in a record single mode fibre net throughput of 178.08 Tbit/s.

Continuous-wave 6-dB-squeezed light with 2.5-THz-bandwidth from single-mode PPLN waveguide

Abstract: Terahertz (THz)-bandwidth continuous-wave (CW) squeezed light is essential for integrating quantum processors with time-domain multiplexing (TDM) by using optical delay line interferometers. Here, we utilize a single-pass optical parametric amplifier (OPA) based on a single-spatial-mode periodically poled ZnO:LiNbO3 waveguide, which is directly bonded onto a LiTaO3 substrate. The single-pass OPA allows THz bandwidth, and the absence of higher-order spatial modes in the single-spatial-mode structure helps avoid degradation of squeezing. In addition, the directly bonded ZnO-doped waveguide has durability for high-power pump and shows small photorefractive damage. Using this waveguide, we observe CW 6.3-dB squeezing at 20-MHz sideband by balanced homodyne detection. This is the first realization of CW squeezing with a single-pass OPA at a level exceeding 4.5 dB, which is required for the generation of a two-dimensional cluster state. Furthermore, the squeezed light shows 2.5-THz spectral bandwidth. The squeezed light will lead to the development of a high-speed on-chip quantum processor using TDM with a centimeter-order optical delay line.

Multidimensional entanglement transport through single-mode fiber

Abstract: The global quantum network requires the distribution of entangled states over long distances, with substantial advances already demonstrated using polarization. While Hilbert spaces with higher dimensionality, e.g., spatial modes of light, allow higher information capacity per photon, such spatial mode entanglement transport requires custom multimode fiber and is limited by decoherence-induced mode coupling. Here, we circumvent this by transporting multidimensional entangled states down conventional single-mode fiber (SMF). By entangling the spin-orbit degrees of freedom of a biphoton pair, passing the polarization (spin) photon down the SMF while accessing multiple orbital angular momentum (orbital) subspaces with the other, we realize multidimensional entanglement transport. We show high-fidelity hybrid entanglement preservation down 250 m SMF across multiple 2 × 2 dimensions, confirmed by quantum state tomography, Bell violation measures, and a quantum eraser scheme. This work offers an alternative approach to spatial mode entanglement transport that facilitates deployment in legacy networks across conventional fiber.

Dirac-vortex topological photonic crystal fibre.

Abstract: The success of photonic crystal fibres relies largely on the endless variety of two-dimensional photonic crystals in the cross-section. Here, we propose a topological bandgap fibre whose bandgaps along in-plane directions are opened by generalised Kekule modulation of a Dirac lattice with a vortex phase. Then, the existence of mid-gap defect modes is guaranteed to guide light at the core of this Dirac-vortex fibre, where the number of guiding modes equals the winding number of the spatial vortex. The single-vortex design provides a single-polarisation single-mode for a bandwidth as large as one octave. Numerical calculations reveal how optical fibers composed of topological photonic crystals could allow improved versatility and control over the modes and polarizations of the light they transmit. Photonic crystals have compositions that create “bandgaps” preventing the passage of light with waves of specific energies and momenta. Hao Lin and Ling Lu at the Institute of Physics of the Chinese Academy of Sciences, base their novel method to transmit pure “single mode” light, over a large frequency range, using a topological feature known as a “Dirac-vortex”. In principle, it could lead to applications that can transmit light signals more stably over long distances. At present, the work is theoretical, but the authors suggest that the fibers could be made from silica using existing stack-and-draw or 3-D printing technologies. Fabrication and testing are the next desirable steps.

Interband Short Reach Data Transmission in Ultrawide Bandwidth Hollow Core Fiber

Abstract: We report a Nested Antiresonant Nodeless hollow-core Fiber (NANF) operating in the first antiresonant passband. The fiber has an ultrawide operational bandwidth of 700 nm, spanning the 1240–1940 nm wavelength range that includes the O-, S-, C- and L- telecoms bands. It has a minimum loss of 6.6 dB/km at 1550 nm, a loss ≤7 dB/km between 1465–1655 nm and ≤10 dB/km between 1297–1860 nm. By splicing together two structurally matched fibers and by adding single mode fiber (SMF) pigtails at both ends we have produced a ∼1 km long span. The concatenated and connectorized fiber has an insertion loss of approximately 10 dB all the way from 1300 nm to 1550 nm, and an effectively single mode behavior across the whole spectral range. To test its data transmission performance, we demonstrate 50-Gb/s OOK data transmission across the O-to L-bands without the need for optical amplification, with bit-error-rates (BERs) lower than the 7% forward error correction (FEC) limit. With the help of optical amplification, 100-Gb/s PAM4 transmission with BER lower than the KP4 FEC limit was also achieved in the O/E and C/L bands, with relatively uniform performance for all wavelengths. Our results confirm the excellent modal purity of the fabricated fiber across a broad spectral range, and highlight its potential for wideband, low nonlinearity, low latency data transmission.

Single mode output by controlling the spatiotemporal nonlinearities in mode-locked femtosecond multimode fiber lasers

Abstract: The performance of fiber mode-locked lasers is limited due to the high nonlinearity induced by the spatial confinement of the single-mode fiber core. To massively increase the pulse energy of the femtosecond pulses, amplification is obtained outside the oscillator. Recently, spatiotemporal mode-locking has been proposed as a new path to fiber lasers. However, the beam quality was either highly multimode and/or with low pulse energy. Here we present an approach to reach high energy per pulse directly in the mode-locked multimode fiber oscillator with a near single-mode output beam. Our approach relies on spatial self-beam cleaning via the nonlinear Kerr effect and we demonstrate a multimode fiber oscillator with M2<1.13 beam profile, up to 24 nJ energy and sub-100 fs compressed duration. The reported approach is further power scalable with larger core sized fibers and could benefit applications that require high power ultrashort lasers with commercially available optical fibers.

Humidity sensor based on a graphene oxide-coated few-mode fiber Mach-Zehnder interferometer.

Abstract: A relative humidity sensor based on a graphene oxide-coated few-mode fiber Mach-Zehnder interferometer (MZI) is proposed in this paper. The MZI was made by splicing a segment of the few-mode fiber (FMF) between two segments of a no-core fiber (NCF) and two segments of a single mode fiber (SMF) located outside the two NCFs. The core and cladding of the FMF acted as interferometric arms, while the NCFs acted as couplers for splitting and recombining light due to mismatch of mode field diameter. The cladding of the FMF was corroded with hydrofluoric acid, and a layer of graphene oxide (GO) film was coated on the corroded cladding of FMF via the natural deposition method. The refractive index of GO varied upon absorption the water molecules. As a result, the phase difference of the MZI varied and the wavelength of the resonant dip shifted with a change in the ambient relative humidity (RH). High humidity sensitivity of 0.191 and 0.061 nm/%RH in the RH range of 30-55% and 55-95%, respectively, were achieved experimentally. The high sensitivity, compact size, and simple manufacturing of the proposed sensor could offer attractive applications in fields of chemical sensors and biochemical detection.

Temperature-Independent Curvature Sensor Based on In-Fiber Mach–Zehnder Interferometer Using Hollow-Core Fiber

Abstract: An in-fiber Mach–Zehnder Interferometer (MZI), based on hollow core fiber (HCF), for measuring curvature is fabricated and experimentally demonstrated. The sensing part was fabricated by splicing a section of HCF between two sections of multimode fiber (MMF), and different HCF lengths were investigated in order to achieve the highest curvature sensitivity. These devices were tested in a transmission configuration using lead-in and lead-out single mode fibers (SMF). The sensor was attached to a steel sheet by using the polymer Polydimethylsiloxane (PDMS) for accurate control of the applied curvature. The modal analysis was carried out using a commercial software based on finite element method (FEM) and by incorporating some of the experimental data, it was feasible to determine the two dominant modes that interfere in this sensor. The devices were characterized by measuring the fringe contrast variations due to the curvature changes. The interferometer fabricated with a HCF 2.5 mm in length HCF showed the highest curvature sensitivity, −17.28 ± 2.30 dB/m−1, in a range from 1.84 m−1 to 2.94 m−1. Moreover, the sensor that exhibited a better performance was fabricated with a HCF length of 1 mm, combining the most extensive curvature range (from 0.95 m−1 to 2.68 m−1) and an adequate sensitivity (−11.80 ±1.30 dB/m−1). The analysis of the interferometric signal of this device in Fourier domain, allows us to establish a one to one relationship between the contrast and the curvature in a broader range (from 0 m−1 to 2.94 m−1). Moreover, the fringe contrast showed a very low dependency on temperature (from 30 °C to 90 °C), depicting that this device was not affected by temperate fluctuation.

16kW single mode CW laser with dynamic beam for material processing

Abstract: The principles of coherent beam combining for multiple fiber laser amplifiers is presented and discussed, with a focus on the optical phased array (OPA) beam combining technique. Several unique properties of OPA beam combining such as real time control over beam scanning, beam shape, focal plane position and intensity modulation with a MHz bandwidth open up several important new degrees of freedom for materials processing applications, enabling higher throughput, more efficient operation and advanced processing techniques. A 16kW dynamic laser beam at 1064nm based on coherent combination of 32 parallel ytterbium doped fiber amplifiers is presented, together with some example beam profiles.

Ultra-High-Speed 2:1 Digital Selector and Plasmonic Modulator IM/DD Transmitter Operating at 222 GBaud for Intra-Datacenter Applications

Abstract: We demonstrate a 222 GBd on-off-keying transmitter in a short-reach intra-datacenter scenario with direct detection after 120 m of standard single mode fiber. The system operates at net-data rates of >200 Gb/s OOK for transmission distances of a few meters, and >177 Gb/s over 120 m, limited by chromatic dispersion in the standard single mode fiber. The high symbol rate transmitter is enabled by a high-bandwidth plasmonic-organic hybrid Mach–Zehnder modulator on the silicon photonic platform that is ribbon-bonded to an InP DHBT 2:1 digital multiplexing selector. Requiring no driving RF amplifiers, the selector directly drives the modulator with a differential output voltage of 622 mVpp measured across a 50 Ω resistor. The transmitter assembly occupies a footprint of less than 1.5 mm × 2.1 mm.

Metal-organic framework functionalized polymer coating for fiber optical methane sensors

Abstract: Functional polymer coating integrated with optical fiber is an intriguing approach to develop low-cost point and distributed fiber sensors for large-scale applications. This paper presents the development of gas-sensitive coatings for both single-mode and multi-mode optical fibers through the application of polymer/nanocrystalline metal-organic frameworks (MOFs) composites as methane sensors for monitoring natural gas infrastructure. Silicone polymers based on PDMS with optimized optical and mechanical properties were developed as host materials for the well-known metal organic framework ZIF-8. Integration of ZIF-8 nanocrystals within the PDMS polymer modified the physical properties of the material and led to an enhancement of the CH4 solubility and permeability of the resulting film. The refractive indices, viscosities, and mechanical properties of the ZIF-8 functionalized polymers were optimized by adjusting the ZIF-8/polymer weight ratio and subsequently used as the fiber coating. Both multi-mode and single-mode optical fibers coated with the MOF-functionalized polymers showed scaled changes in transmitted power upon exposure to various concentration of CH4 in a N2 carrier gas. The variations in transmitted power through the fiber were the result of changes in evanescent wave interactions with the sensor coating due to shifts in the polymer cladding refractive index upon CH4 sorption. A methane detection limit of 1 % in nitrogen was achieved using both multimode fiber and D-shaped single mode fibers. Overall, our paper presents a low-cost approach to perform point and distributed sensing for CH4 through an innovative method of functional polymer material integration on optical fiber sensor platforms.

Distributed multicore fiber sensors

Abstract: Multicore fiber (MCF) which contains more than one core in a single fiber cladding has attracted ever increasing attention for application in optical sensing systems owing to its unique capability of independent light transmission in multiple spatial channels. Different from the situation in standard single mode fiber (SMF), the fiber bending gives rise to tangential strain in off-center cores, and this unique feature has been employed for directional bending and shape sensing, where strain measurement is achieved by using either fiber Bragg gratings (FBGs), optical frequency-domain reflectometry (OFDR) or Brillouin distributed sensing technique. On the other hand, the parallel spatial cores enable space-division multiplexed (SDM) system configuration that allows for the multiplexing of multiple distributed sensing techniques. As a result, multi-parameter sensing or performance enhanced sensing can be achieved by using MCF. In this paper, we review the research progress in MCF based distributed fiber sensors. Brief introductions of MCF and the multiplexing/de-multiplexing methods are presented. The bending sensitivity of off-center cores is analyzed. Curvature and shape sensing, as well as various SDM distributed sensing using MCF are summarized, and the working principles of diverse MCF sensors are discussed. Finally, we present the challenges and prospects of MCF for distributed sensing applications.

An enhanced WDM optical communication system using a cascaded fiber Bragg grating

Abstract: In this paper, a cascaded fiber Bragg grating (FBG) system is proposed to reduce the dispersion in the optical signal in single mode optical fibers. This consequently enhances the system performance, which is evaluated by the bit error rate (BER) and quality factor (Q-factor). The proposed model consists of four uniform cascaded FBGs connected at the transmitter to get narrow linewidth, Δλ, of the optical signal, which is a major cause of the delay. The Optisystem7 is used to simulate the proposed model in a WDM system with and without the model for distance 200 km. The system parameters are investigated showing an enhanced performance with 12%, including eye diagram, Q-factor and BER. A 10−6–10−10 BER is achieved with a quality factor in the range 7–14, including the effects of fiber length, input power and FBG length.

Tuneable red, green, and blue single-mode lasing in heterogeneously coupled organic spherical microcavities.

Abstract: Tuneable microlasers that span the full visible spectrum, particularly red, green, and blue (RGB) colors, are of crucial importance for various optical devices. However, RGB microlasers usually operate in multimode because the mode selection strategy cannot be applied to the entire visible spectrum simultaneously, which has severely restricted their applications in on-chip optical processing and communication. Here, an approach for the generation of tuneable multicolor single-mode lasers in heterogeneously coupled microresonators composed of distinct spherical microcavities is proposed. With each microcavity serving as both a whispering-gallery-mode (WGM) resonator and a modulator for the other microcavities, a single-mode laser has been achieved. The colors of the single-mode lasers can be freely designed by changing the optical gain in coupled cavities owing to the flexibility of the organic materials. Benefiting from the excellent compatibility, distinct color-emissive microspheres can be integrated to form a heterogeneously coupled system, where tuneable RGB single-mode lasing is realized owing to the capability for optical coupling between multiple resonators. Our findings provide a comprehensive understanding of the lasing modulation that might lead to innovation in structure designs for photonic integration.

A miniature ultra long period fiber grating for simultaneous measurement of axial strain and temperature

Abstract: A SMF-MMF-SMF-ultra long period fiber grating (SMS-ULPFG) sensor is proposed for the simultaneous measurement of axial strain and temperature. The all-optical fiber sensor was fabricated by periodically splicing a multimode fiber (MMF) and a single mode fiber (SMF). Due to the strong refractive index (RI) modulation ability of the MMF, the sensor forms two resonant dips with smaller dimensions (the period of 1000 µm and total length of 5 mm). The transmission spectra were obtained by experiments and simulations. The results of the performance tests indicate that the uncertainty values of the SMS-ULPFG structure are 3.26 μe and 0.23 °C over the ranges of 0–1000 μe and 26–118 °C.

Switchable and tunable multi-wavelength fiber laser based on a core-offset aluminum coated Mach-Zehnder interferometer

Abstract: In this work, a switchable and tunable multi-wavelength erbium-doped fiber laser based on a core-offset aluminum coated Mach-Zehnder interferometer (ACMZI) is presented. The ACMZI is fabricated by core-offset fusion splicing a single-mode fiber segment between two lengths of single mode fiber and then by coating it with aluminum using the thermal evaporation technique. The ACMZI is used as a wavelength selective filter in the proposed ring cavity design. Experimental results show that the laser emission can be switched among a single, double, and triple emission lines by carefully adjusting a polarization controller. Furthermore, the laser lines can be tuned by changing the temperature of the ACMZI. The laser can emit in a single-longitudinal mode and has a single-mode suppression ratio of about 55 dB, a linewidth of 0.05 nm and an efficiency slope of 0.29%. Finally, the laser arrangement is compact, robust, and requires a relatively simple fabrication procedure.

Temperature-Compensated Refractive Index Measurement Using a Dual Fabry–Perot Interferometer Based on C-Fiber Cavity

Abstract: We demonstrate a simple-to-fabricate, temperature-compensated refractive index sensor using a dual Fabry-Perot optical fiber interferometer using C-fiber. The sensor device is formed by combining two types of in-fiber interferometers, including a C-fiber Fabry-Perot interferometer and a single mode fiber (SMF) Fabry-Perot (FP) interferometer. The C-fiber is a silica capillary with an open side, which allows external liquid to directly enter the internal hole. The C-fiber interferometer is sensitive to external refractive index (1704 nm/RIU) as well as temperature (-0.196 nm/°C) due to the thermo-optic effect and thermal expansion of the C-fiber cavity, while the SMF interferometer is only sensitive to ambient temperature (0.0118 nm/°C). Thus, temperature-compensated refractive index measurement can be achieved by examining the phase shift responses of the two FP interference peaks with transfer matrix approach, solving the problem of temperature sensitivity of RI sensors due to the relatively large thermo-optic coefficient of colloidal materials and aqueous samples.

Efficient generation of multi-gigawatt power by an X-band dual-mode relativistic backward wave oscillator operating at low magnetic field

Abstract: An X-band dual-mode relativistic backward wave oscillator (RBWO) operating at low magnetic field is presented in this paper. Three new design principles are introduced in the device. First, the electron beam interacts with TM01 mode and TM02 mode simultaneously, rather than with a fixed single mode. Second, the device outputs with mixed modes, rather than with a pure mode. Third, an internal reflector inserted into the annular cathode, rather than a long resonant reflector before the slow-wave structure, is adopted to reflect part of the backward wave. Accordingly, the beam–wave interaction efficiency is increased significantly and the whole device is very compact. The particle in cell simulation results reveal that at a magnetic field of 0.64 T, the output microwave power is 4.8 GW and the conversion efficiency is up to 44%. In the experiment, at a guiding magnetic field of 0.66 T, a microwave pulse with power of 4.6 GW, frequency of 9.96 GHz, pulse duration of 42 ns, and efficiency of 42% was generated when the diode voltage was 880 kV and beam current was 12.5 kA, which agree well with the simulation results. Furthermore, as the diode voltage was 1.17 MV, a highest microwave power of 7.6 GW was achieved. This is a record of high efficiency and high power of microwave generation in an X-band RBWO operating at low magnetic field.

Recent Advances in 100+nm Ultra-Wideband Fiber-Optic Transmission Systems Using Semiconductor Optical Amplifiers

Abstract: We report on the use of semiconductor optical amplifiers (SOAs) to extend the optical bandwidth of next generation optical systems to 100 nm and beyond. After discussing the technological progress and the motivation for rekindling the interest in SOAs for line amplification, we describe the innovative approach developed for the realization of ultra-wideband (UWB) SOAs. Leveraging custom design of singly polarized SOAs to provide gain over 100+ nm bandwidth, we developed a polarization diversity architecture to realize UWB-SOA modules. Embedded in a compact package, the UWB amplifier modules have been successfully used to demonstrate 100+ Tb/s transmissions. We subsequently review recent experimental transmission results based on such novel 100+ nm wide semiconductor optical amplifiers, including our first demonstration of 100+Tb/s transmission over 100 km distance, our field trial using real-time traffic, and finally the transmission of 107 Tb/s throughput over three spans of standard single mode fiber (SSMF) using hybrid UWB Raman/SOA amplification technique.

Passively mode-locked quantum dash laser with an aggregate 5.376 Tbit/s PAM-4 transmission capacity.

Abstract: This paper presents an InAs/InP quantum dash (QD) C-band passively mode-locked laser (MLL) with a channel spacing of 34.224 GHz. By using this QD-MLL we demonstrate an aggregate 5.376 Tbit/s PAM-4 data transmission capacity both for back-to-back (B2B) and over 25-km of standard single mode fiber (SSMF). This represents the first demonstration of QD-MLL acting as error-free operation at an aggregate data transmission capacity of 5.376 Tbit/s for some filtered individual channels. This finding highlights the viability for InAs/InP QD lasers to be used as a low-cost optical source for data center networks.

High-Sensitivity Fabry–Perot Interferometer High-Temperature Fiber Sensor Based on Vernier Effect

Abstract: A novel sensitivity-enhanced intrinsic fiber Fabry-Perot interferometer (IFFPI) high temperature sensor based on a hollow-core photonic crystal fiber (HC-PCF) and modified Vernier effect is proposed and experimentally demonstrated. The compact all fiber IFFPIs are easily constructed by splicing one end of the HC-PCF to a leading single mode fiber (SMF) and applying an arc at the other end of the HC-PCF to form a pure silica tip. The Vernier effect is formed by three beams of lights reflected from the SMF-PCF splicing joint, and the two air/glass interfaces on the ends of the collapsed HC-PCF tip, respectively. This Vernier effect based fiber sensor can stand with high temperature up to 1200°C, in this work, and experimental results exhibit good linearity, stability and repeatability. The temperature sensitivity can be further enhanced by reducing length of pure silica tip—that is, simply optimizing the discharge time and intensity. The fabrication of the sensitivity-enhanced IFFPI is straightforward, reproducible and low cost, which shows a potential for practical applications in various industrial processes.

Low-loss single-mode hybrid-lattice hollow-core photonic crystal fiber

Abstract: The remarkable recent demonstrations in ultralow loss Inhibited-Coupling (IC) hollow-core photonic crystal fibers (HCPCFs) place them as serious candidates for the next-generation of long-haul fiber optics systems. A hindrance to this prospect, but also to short-haul applications such as micromachining, where stable and high-quality beam delivery is needed, is the challenge to design and fabricate an IC-guiding fiber that combines ultra-low loss, truly and robust single-modeness, and polarization-maintaining operation. Design solutions proposed up to now require a trade-off between low loss and truly single modeness. Here, we propose a novel concept of IC HCPCF for obtaining low-loss and effective single-mode operation. The fiber is endowed with a hybrid cladding composed of a Kagome-tubular lattice (HKT). This new concept of microstructured cladding allows to significantly reduce confinement loss and, at the same time, preserving a truly and robust single-mode operation. Experimental results show a HKT-IC-HCPCF with a minimum loss figure of 1.6 dB/km at 1050 nm and a higher-order modes extinction ratio as high as 47.0 dB for a 10 m long fiber. The robustness of the fiber single-modeness was tested by moving the fiber and varying the coupling conditions. The design proposed herein opens a new route for the accomplishment of HCPCFs that combine robust ultralow loss transmission and single-mode beam delivery and provides new insight into the understanding of IC guidance.

Ultra-Sensitive Fiber-Optic Temperature Sensor Consisting of Cascaded Liquid-Air Cavities Based on Vernier Effect

Abstract: A temperature sensor consisting of cascaded liquid-air cavities based on Vernier effect was proposed. The cascaded liquid-air cavities were fabricated simply by partially filling a section of silica capillary tube (SCT) with dimethyl silicone oil (DSO). One opening of the SCT was spliced to the single mode fiber, and the other opening was sealed by the UV glue. The Vernier effect could be generated when the optical paths of liquid-air cavities are close to each other. More importantly, as the lengths of the two cavities change synchronously and complementarily along with the thermal shift of the liquid-air interface, the sensitivity of the sensor can be further improved by about 1.7 times on the basis of ordinary Vernier effect. The actual temperature sensitivity of the proposed sensor around 35 °C reaches as high as 39.21 nm/ °C, which makes the sensor more competitive in medical and pharmaceutical fields.

Continuous-wave 6-dB-squeezed light with 2.5-THz-bandwidth from single-mode PPLN waveguide

Abstract: Terahertz (THz)-bandwidth continuous-wave (CW) squeezed light is essential for integrating quantum processors with time-domain multiplexing (TDM) by using optical delay line interferometers. Here, we utilize a single-pass optical parametric amplifier (OPA) based on a single-spatial-mode periodically poled ZnO:LiNbO3 waveguide, which is directly bonded onto a LiTaO3 substrate. The single-pass OPA allows THz bandwidth, and the absence of higher-order spatial modes in the single-spatial-mode structure helps to avoid degradation of squeezing. In addition, the directly bonded ZnO-doped waveguide has durability for high-power pump and shows small photorefractive damage. Using this waveguide, we observe CW 6.3-dB squeezing at 20-MHz sideband by balanced homodyne detection. This is the first realization of CW squeezing with a single-pass OPA at a level exceeding 4.5 dB, which is required for the generation of a two-dimensional cluster state. Furthermore, the squeezed light shows 2.5-THz spectral bandwidth. The squeezed light will lead to the development of a high-speed on-chip quantum processor using TDM with a centimeter-order optical delay line.

An Optical Fiber Sensor Based on Lateral-Offset Spliced Seven-Core Fiber for Bending and Stretching Strain Measurement

Abstract: We demonstrate a fiber-optic strain sensor based on a seven-core fiber (7-CF) for accurate extrusion bending and tensile strain sensing. The sensor structure we designed is the 7-CF spliced to a piece of multimode fiber on each side with a lateral core-offset and then conventionally fused to single mode optical fiber as the input and output ports. The experimental results indicate that the optimal curvature sensitivity of the sensor is achieved 25.96 nm/m−1, and the sensitivity of the tensile strain is 0.094 nm/ $\mu \varepsilon $ , which allows us to monitor bending and stretching strain respectively with high precision by the simple, low-cost, and effective sensor.

Investigation of gas sensor based on differential optical absorption spectroscopy using photonic crystal fiber

Abstract: This study presented a novel shape photonic crystal fiber based gas sensor for the first time. Perfectly circular shape air hole are arranged to form core and cladding region. Based on full vector finite element method (FV-FEM) and circular shape perfectly matched layer (PML) the designed sensor has been investigated. The model field, effective mode index, sensitivity, confinement loss, effective mode area, nonlinearity, V parameter of the sensor fiber fundamental mode are investigated through FEM based commercial software package COMSOL Multiphysics. Numerical simulations evidences that the sensor shows the sensitivity responses of 64.69% and confinement loss of 4.38 × 10-06 dB/cm at the transmission wavelength λ = 1.55 µm. Besides, the sensor achieves single mode operation over the whole operating wavelength. Based on these excellent optical behaviors of the designed sensor it can be undoubtedly expect that, this sensor will play an influential role detecting gas molecules as well as PCF based optical sensing areas.