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The influence of neutron and gamma radiation on single mode fiber cables is experimentally conducted. Attenuation due to incident radiation is measured. Attenuation is determined by laser source and power meter in Africa Teleco Company, besides attenuation recovery is attained. The Gamma experiment is carried out within Egypt Mega Gamma1 in National Center for Radiation Research and Technology of Egyptian Atomic Energy Authority (EAEA). In this experiment, the cable is degraded by gamma radiation of doses 5KGy, 10KGy, 15KGy and 25KGy and dose rate of 1KGy/26.4 min. However the attenuation based on neutron degradation is executed in the second Egyptian Training Research Reactor (ETRR-2), in front of neutron beam facility (NBF) in ETRR-2 which has a flux of 1.5x107(n/cm2.sec). For both experiments, the experimental measurements are done at two different spectral wavelengths of 1310 nm and 1550 nm. A comparison between obtained results is investigated.

This paper proposes a highly sensitive, compact, and low-cost optical fiber salinity sensor based on the Mach-Zehnder interferometer. The sensor is constructed using a single mode fiber (SMF) - no-core fiber - double-C fiber (DCF) - NCF-SMF structure, with the DCF prepared by etching the dual side-hole fiber with HF acid. The DCF's large-size exposed microfluidic channels solve the previous microstructured optical fiber's challenging liquid filling and replacement problems. Theoretical simulations and experiments demonstrate that the sensor is suitable for high-sensitivity salinity measurement. The sensor exhibits a high salinity sensitivity of -2.26 nm/‰ in the salinity range of 10‰-50‰, as demonstrated by the experimental results. Additionally, the sensor exhibits some fascinating characteristics, including high repeatability, hysteresis, reversibility, and stability.

Commercial coherent receivers utilize balanced photodetectors (PDs) with high single-port rejection ratio (SPRR) to mitigate the signal-signal beat interference (SSBI) due to the square-law detection process. As the symbol rates of coherent transponders are increased to 100 Gbaud and beyond, maintaining a high SPRR in a cost-effective manner becomes more and more challenging. One potential approach for solving this problem is to leverage the concept of single-ended coherent receiver (SER) where single-ended PDs are used instead of the balanced PDs. In this case, the resulting SSBI should be mitigated in the digital domain. In this paper, we show that SSBI can be effectively mitigated using various low-complexity techniques, such as the direct filed reconstruction (DFR), clipped iterative SSBI cancellation (CIC) and gradient decent (GD). In addition, we present a self-calibration technique for SERs which can be extended for characterizing the optical-to-electrical (O/E) response of a conventional balanced coherent receiver (BR). Using the developed techniques, we then experimentally demonstrate a 90 Gbaud probabilistically constellation shaped 64-QAM (PCS-64QAM) transmission using a SER, achieving a net data rate of 882 Gb/s over 100 km of standard single mode fiber (SSMF). The sensitivity penalty compared to the BR is below 0.5 dB. We expect that when the symbol rate is increased further, a SER can potentially outperform a BR, especially when applied to cost-sensitive commercial pluggable coherent transceivers

Thin film lithium niobate on insulator (LNOI), as an emerging photonic material, provides a promising platform to realize compact, high-speed, and high-efficient electro-optic (EO) modulators. However, due to the large coupling loss caused by the large mode field mismatch between standard single mode fibers and the LNOI waveguides, edge or grating couplers are indispensable to LNOI modulators. In this paper, we propose a novel edge coupler employing staircase structure. The proposed coupler is feasible with i-line lithography and avoids high precise alignment. Moreover, such coupler can be applied to wafer-scale manufacture with low cost. The simulation results show that a low input/output coupling loss of 1.14 dB/1.62 dB can be achieved at 1.55 m wavelength for transverse electric (TE) polarized light signals. Specifically, benefited from the novel staircase design, the proposed edge coupler shows a unique property of polarization extinction ratio larger than 10 dB, which will further improve the modulation efficiency and depth of the EO modulators based on X-cut LNOI.

This paper presents a remote beamforming scheme with fixed wavelength allocation for radio-over-fiber (RoF) systems employing single-mode fiber (SMF). In the proposed scheme, wavelengths with equal narrow spacing are fixedly assigned to each antenna element to equalize the time delay differences between adjacent wavelengths caused by chromatic dispersion. The beam direction of base station (BS) is controlled only by phase control at central station (CS). This offers efficient wavelength utilization and completely remote beam control without information of optical fiber length, and supports systems employing high carrier frequency and long optical fiber. The beamforming performance of the scheme is evaluated theoretically and experimentally. It is shown that the beam pattern depends on optical intensity modulation frequency instead of radiated frequency. Simulations indicate that the required wavelength spacing to obtain a desired beam pattern becomes narrower as more wavelengths are used or intensity modulation frequency becomes higher. Finally, to evaluate the feasibility of the scheme, experiments are conducted under the condition of intensity modulation frequency of 10 GHz, 10 km SMF, and four element array antenna. The results substantially agree with the simulation results, and the main lobe level decrease is within 0.04 dB at wavelength spacing of 50-400 GHz (0.39-3.13 nm on average in C band). The results confirm that the scheme can achieve almost ideal beam patterns and realize beamforming and beamscanning.

Optical frequency domain reflectometry measurements in internally clad single crystal sapphire fiber have received attention in recent years due to their high temperature distributed sensing potential. As work with these fibers has proceeded, there have been some inconsistencies in the results. Deeper investigation and testing has identified two critical considerations for the proper functioning of these fibers. First, users must address the propagation of multimode light along the outer surface of the fiber. By observing the far-field image of an internally clad sapphire fiber when adding index matching fluid to the outer fiber surface, we demonstrate the effects of removing the higher order modes from these fibers. The addition of index matching fluid resulted in nearly single mode performance where multimode performance was previously observed. Second, users must address the effect that coupling the fiber to the interrogator via silica based fiber has on the internally clad sapphire fibers performance. Direct fusion splicing of silica to sapphire, as has been used in the recent work with these fibers, has a mode filtering effect which can be beneficial towards the modal behavior of the fibers. However, in this paper we demonstrate that the splicing can cause a sensing failure due to little or no low order mode light, that is useful for sensing, returning to the detector. The positive results from recent years have demonstrated that optical frequency domain reflectometry sensing performance will be successful in clad sapphire fiber; but only when the considerations described herein are addressed properly.

We propose a frequency modulation (FM) non-coherent detection (NCD) scheme, attempting to suppress the mode partition noise (MPN) in fiber-optic communication systems with the Fabry-Perot (FP) semiconductor laser as the light source. The system comprises a FM transmitter with a directly modulated FP laser and a semiconductor optical amplifier, standard single mode fiber, and a NCD receiver with an optical slope filter as the FM to intensity modulation (IM) signal convertor placed in front of a conventional photodetector. In this configuration, the MPN is converted into a random frequency deviation by the transmitter and is reduced by the slope filter after fiber transmission. The FM signal is therefore less noisy after being converted back into the IM signal. With optimized parameter selections, our simulation result shows that the FM-NCD system allows a direct transmission span of 40 km for the 10 Gbps signal at 1577 nm, and 120 km for the 25 Gbps signal at 1310 nm, respectively, as opposed to a span of only 3 km and 10 km achievable by a conventional FP laser driven IM direct detection (DD) system for the corresponding signals at the corresponding wavelengths. Remarkably, our simulation result also shows that the performance of the FM-NCD system even surpasses that of a directly modulated distributed feedback laser driven IM-DD system, in which the maximum span is around 15 km and 60 km for 10 Gbps and 25 Gbps signals at 1577 nm and 1310 nm, respectively.

We report on the development of a two-channel digital coherent optics (DCO) module, based on a monolithic InP photonic integrated circuit (PIC) transceiver and SiGe application-specific integrated circuit (ASIC), paired with a real-time 7 nm digital signal processing (DSP) ASIC. The high-performance coherent optical engine, which utilizes digital Nyquist subcarriers and probabilistic constellation shaping (PCS) techniques, enables long-haul and ultra-long-haul transmission distances over mixed fiber and amplifier types. This work discusses the performance of a DCO unit operating at multiple data rates over three practical real-world-like network distances. 800 Gb/s data transmission over a 1,000 km standard single mode fiber link was achieved using a 96 GBd, PCS-64QAM modulation format. Results of extended reaches of over 2,400 km and 5,000 km are also presented with data rates of 600 Gb/s and 400 Gb/s, respectively.

This paper comprehensively investigated noise characteristics of superluminal propagation based on low-noise single-frequency Brillouin lasing oscillation with the aid of a population inversion dynamic grating. Thanks to high-degree polarization alignment between the Brillouin pump and the lased Stokes lightwaves in polarization maintaining fibers, efficient Brillouin lasing resonance with over 10-dB relative intensity noise suppression has been demonstrated to activate Brillouin loss-induced anomalous dispersion in the vicinity of pump signals, benefiting a noise-insensitive superluminal propagation along kilometer-long optical fibers with robust resistance to ambient disturbance. Consequently, sinusoidally modulated pump signals experienced the time advancement of 4634.0 ns at the group velocity of 10.63c. Results show that the variance of the fractional advancement with polarization maintaining fibers is 2.54 × 10−4 which is two orders of magnitude lower than that of conventional single mode fibers. Furthermore, the dependence of the group velocity on the modulation frequency was experimentally investigated, showing good agreement with the theoretical analysis.

We design and fabricate the suspended silicon microring with racetrack and spiral structure to exploit the resonantly enhanced stimulated Brillouin scattering (SBS). The designed photonic-phononic waveguide can provide the independent control on the optical and acoustic modes by introducing the silicon ridge waveguide into the phononic crystal slab as a line defect. We demonstrate efficient forward SBS in the two kinds of microrings and extract the characteristic Brillouin parameters through the heterodyne four-wave mixing measurement. The stronger inhomogeneous broadening effect in the spiral microring due to the structural variations is also observed. In addition, our microrings show the single mode transmission spectrum and high quality factor, which is beneficial to the enhanced intramodal forward SBS. This design can readily extend to other silicon-based platforms and paves the way toward on-chip photonic-phononic signal processing and Brillouin amplifier technologies.

Miniaturized lasers with multicolor output and high spectral purity are indispensable for various ultracompact photonic devices. Here, we propose an optically reconfigurable Forster resonance energ...

The transmission of the high data rate and information over the optical fiber is restricted by various dispersion phenomenon which further results into inter-symbol interference (ISI). There are numerous alternatives present to resolve this hurdle of dispersion. Unlike other dispersion compensating procedures, electronic dispersion compensators (EDC) which makes use of non-linear and linear equalization approach is an effectual, cost effective and compact dispersion compensating method. This paper is approaching EDC technique for compensation of chromatic dispersion at four distinct bit rates of 25, 30, 40 and 40 Gbps over 120Km of single mode fiber. To Achieve this, a single channel optical system with the help of simulation software i.e., Optisystem is being used for the above-mentioned technique. After exploring their outcomes, another operation of comparing these two-bit rates using pin photodiode and avalanche photodiode has been applied. The simulations showed the optimum photodiode for efficacious dispersion compensation at such a long transmission distance.

Spatial division multiplexing using conventional orbital angular momentum (OAM) has become a well-known physical layer transmission method over the past decade. The mode-group (MG) superposed by specific single mode plane spiral OAM (PSOAM) waves has been proved to be a flexible beamforming method to achieve the azimuthal pattern diversity, which inherits the spiral phase distribution of conventional OAM wave. Thus, it possesses both the beam directionality and vorticity. In this paper, it’s the first time to show and verify a novel PSOAM MG based multiple-in-multiple-out (MIMO) communication link (MG-MIMO) experimentally in a line-of-sight (LoS) scenario. A compact multi-mode PSOAM antenna is demonstrated experimentally to generate multiple independent controllable PSOAM waves, which can be used for constructing MGs. After several proof-of-principle tests, it has been verified that the beam directionality gain of MG can improve the receiving signal-to-noise (SNR) level in an actual system. Meanwhile, the vorticity can provide another degree of freedom (DoF) to reduce the spatial correlation of MIMO system. Furthermore, a tentative long-distance transmission experiment operated at 10.2 GHz has been performed successfully at a distance of 50 m with a single-way spectrum efficiency of 3.7 bits/s/Hz/stream. The proposed MG-MIMO may have potential in the long-distance LoS back-haul scenario.

A sensitivity-improved fiber-optic ultrasonic sensor is proposed and employed for ultrasonic imaging of seismic physical models (SPMs). The sensor consists of a single mode fiber (SMF) embedded into the hollow-core-fiber (HCF) bubble. Using gas pressure assisted arc discharge, the diameter of the bubble can be larger than 430 um with a wall thickness of approximately 0.48 um. Besides, by using the coating technique, the optical reflectivity and extinction ratio of the ultra-thin bubble are further improved. Fiber tails of SMF and the HCF are partly bonded to form an open-cavity sensor. When applied with ultrasonic waves (UWs), the compact bubble can balance the difference of air pressure between inside and outside. Eventually, a side-band filter technique is used for UWs interrogation. Compared with enclosed uncoating fiber bubble, the sensor shows an enhanced response to pulsed ultrasound. The SPMs of rugged topography and reservoir type are both designed and the proposed sensor is used for ultrasonic imaging of the two specific models.

In this paper, a high-speed switchable dual-passband microwave photonic filter (MPF) using a single mode Fabry-Perot laser diode (SMFP-LD) is proposed and experimentally demonstrated. Benefiting from the wavelength selective amplification in the SMFP-LD, the +1st sideband of two external beams injected after phase modulation can be amplified in the gain spectrum of the SMFP-LD. Hence, an MPF with two tunable passbands is generated. The switching of the generated passbands is obtained through the switching signal of 1 Gbps applied to the modulator, which controls the power of one of the external beams. By properly setting the external beams injection parameters, the passbands of MPF can switch from single passband to no passband, single passband to dual passband, and one passband to another passband. In this experiment, the maximum center frequency and tuning range of the passbands is 45.0 GHz and 35.0 GHz, respectively. The out-of-band rejection ratio and 3 dB bandwidth of the proposed filter are 29.62 dB and 83 MHz, respectively.

We report novel designs to excite Whispering Gallery Mode (WGM) of spherical microresonator in an integrated single mode optical fiber tip probe, namely, Deep Seated Negative Axicon (DSNA). The empty DSNA and partially filled polymer DSNA are explored to host the Barium Titanate/Silica microresonator as WGM resonators. An SLD source with a central wavelength of 840 nm and bandwidth of 50 nm is used to excite the microresonator. Reflected spectra are recorded in a spectrometer through an optical circulator for different resonators at various locations. Experimentally the quality factor Q as high as ~7×103 is achieved from the design. It is observed that spectral characteristics and Q value are affected by the resonator’s position, size and the material. The Finite Element Method (FEM) simulation results have also been included in support of the design.

We experimentally and theoretically demonstrate a new method to obtain a single-mode operation in long cavity lasers. The method is based on suppressing non-lasing modes in the time domain by attenuating their intensity beating with the lasing mode. This suppression is implemented in our experiments by adding into the cavity an intensity modulator, which is controlled by the photo-detected beating signal. We have demonstrated the method in a long Erbium-doped fiber ring laser with a ring cavity length of about 13 m. Single-mode operation without mode-hopping was obtained for a long time duration of about 100 minutes. Although Erbium-doped fiber amplifiers are homogeneously broadened at room temperature, a single-mode operation was achieved in several cavity modes, which do not have the highest small-signal gain. A theoretical model, based on a small-signal stability analysis, is given. The model indicates that the control delay should be accurately chosen.

Based on a dual-loop optoelectronic oscillator (OEO) with Vernier effect, a scheme of fiber Bragg grating (FBG) interrogation system with an improved scale factor has been proposed and experimentally demonstrated. Functioning as the optical carrier of the OEO, the reflection signal of two cascaded FBGs is divided into two optical beams by using a wavelength division multiplexer (WDM). The two optical beams at different wavelengths travel along single mode fibers with different lengths. After combined together by another WDM, the two optical beams go through a section of dispersion compensation fiber (DCF). The oscillating frequency shift of the OEO is determined by the overall time delay, which is affected by the wavelength change of the sensing FBG. Thus, the wavelength change of the sensing FBG can be converted into the oscillating frequency shift of the OEO. Furthermore, due to the length difference between the two optical beams, an obvious Vernier effect has been generated in the frequency response of the OEO. By detecting the frequency shift of the envelope peak of the frequency response curve, the sensitivity of the sensing interrogation can be enhanced greatly. A proof-of-concept OEO-based FBG sensor for axial strain sensing experiment is performed. The experimental results show that the sensitivity is about 0.31 KHz/μϵ for a single-loop OEO. By employing Vernier effect, the sensitivity can be improved to -11 KHz/μϵ, which is 35 times higher than that of the single-loop OEO.

A Fabry-Perot interferometer (FPI) temperature sensor was proposed by splicing a self-made hollow core anti-resonance fiber (HC-ARF) between two single mode fibers (SMFs). The HC-ARF was 2 mm long and one SMF was 20 mm in length. The SMF end face was coated with an Au film. When temperature varied from 45 °C to 85 °C, a sensitivity of 81.1 pm/°C was obtained at the waveband of 1550 nm∼1555 nm. When temperature varied from 35 °C to 95 °C, a sensitivity of 138.8 pm/°C was obtained at the waveband of 1571 nm∼1581 nm. Theoretical analysis suggested that the sensitivity of this proposed sensor can be easily adjusted by varying the length of the Au-coated SMF via the Vernier effect, which was confirmed by a subsequent experiment where the SMF length was varied from 20 mm to 170 mm. This work offers a simple sensitivity control method, and the proposed sensor is easy to manufacture, compact in structure, and convenient in performance control, which can be applied for a wide range of biological and chemical applications.

As bit rates of optical interconnects increase, a large amount of complicated signal conditioning is needed to compensate for the insufficient bandwidth of current modulators. In this paper, we evaluate the reduced equalization requirements of high-bandwidth plasmonic modulators in short-reach transmission experiments. It is shown that transmission of 100 Gbit/s non-return-to-zero (NRZ) and 112 Gbit/s pulse-amplitude modulation-4 over 1 km and 2 km distance is possible without any receiver equalization. At higher bit-rates, such as 120 Gbit/s NRZ, data transmission is demonstrated over 500 m with reduced receiver equalization requirements. Transmission up to 200 Gbit/s over 1 km is also shown with more complex receiver equalization. The reduced complexity of the receiver digital signal processing is attributed to a flat frequency response of at least 108 GHz of the plasmonic modulators. All single wavelength transmissions have been performed at 1540 nm in standard single mode fiber.

This present work is about simulating and analysing a Vertical Cavity Surface Emitting Laser (VCSEL) structure used in optical fibre communication systems. In this paper a VCSEL structure made of seven Quantum Wells of Indium Gallium Arsenide Phosphide (InGaAsP) emitting at 1550 nm is simulated. The device is analysed looking at the following characteristics: Direct current current and voltage (IV) characteristics, light power against electrical bias, optical gain against electrical bias, light distribution over the structure, output power and threshold current. Specification of material characteristics, ordinary physical models settings, initial VCSEL biasing, mesh declarations, declaration of laser physical models, their optical and electrical parameters were defined using Atlas syntax. Mirror ratings and quantum wells are the two main parameters that were studied and analysed to come up with structure trends. By determining important device parameters such as proper selection of the emission wavelength and choice of material; a VCSEL with an output power of 9.5 mW was simulated and compared with other structures.

We propose and demonstrate a fiber optic multi-point bending measurement system that uses Bragg gratings inscribed along a multi-core fiber (MCF) and a silicon avalanche photodiode (Si-APD) that produces two-photon absorption (TPA) photocurrent for 1.55- $\mu \text{m}$ light. Because the TPA photocurrent from the Si-APD is proportional to the mean square of the optical intensity, the intensity correlation between 1.55- $\mu \text{m}$ probe and reference beams is measured from it without using complex electrical circuits. The proposed system has different lengths of optical fibers between each core of MCF and input/output ends of a single mode fiber optic system, which makes different the correlation signal between the reference beam and the probe beam reflected from different Bragg gratings in MCF. That enables the reflection spectra of all the Bragg gratings in MCF to be separately measured even when they are overlapped in the wavelength domain. As a result, the bending radius and its direction are measured without using multiple detectors or optical switching devices. We conducted proof-of-concept experiments by using a 7-core MCF with almost the same Bragg gratings inscribed in each core at three points along the fiber. We also demonstrated an example of application to shape measurement.

Mode division multiplexing (MDM) has attracted great attention in recent years to increase the network capacity. To apply MDM in data center applications, a low-cost and low power consumption system is desired. In this letter, we utilize 850-nm single-mode VCSEL as the laser source and report mode division multiplexed transmission over a standard single-mode fiber, which is two-mode at 850 nm. Due to the small spot size and low numerical aperture, single-mode VCSEL can be coupled into single-mode fibers with low loss. The mode multiplexer and de-multiplexer devices are designed and fabricated based on fiber mode selective couplers using Hi780 fiber as the 850-nm single-mode launch and receiving fiber and standard single-mode fiber as the few-mode transmission fiber. The MDM system supports two channels, corresponding to the LP01 and LP11 mode in the few-mode transmission fiber. Detailed characterizations of the multiplexer and de-multiplexer are conducted including the insertion loss and crosstalk measurements. System transmission at 25 Gb/s shows error free performance over 1-km standard single- mode fiber for both channels. The utilization of VCSEL and standard single-mode fiber can potentially provide a low-cost solution for MDM systems in data center applications.

Multi-carrier optical communication schemes are attractive for high-speed mobile fronthaul networks, edge cloud computing and passive optical networks. Compared with conventional orthogonal frequency-division multiplexing (OFDM), universal filter multi-carrier (UFMC) can shape the spectrum of the transmitted signal by introducing universal filter banks. Meanwhile, probabilistic shaping (PS) can make full use of achieved signal-to-noise ratio (SNR) to adaptively adjust the entropy loading according to the measured SNR of each subchannel. However, the significant amount of required distribution matcher (DM) is challenging in the practical implementation. In this work, we experimentally demonstrated 12.5-GBd and 25-GBd PS-UFMC transmissions with approximate 10-GHz bandwidth-limited system over 30-km standard single mode fiber. Due to the sharp cutoff frequency-response of filters, the effect of the frequency decaying in the 25-GBd OFDM system has been eliminated in the UFMC system. Consequently, each subband has similar SNR and therefore the number of required DMs is reduced. Moreover, considering the receiver complexity constraints, the improved bit error ratio performance was achieved by optimizing the allocation of data subbands to mitigate inter symbol interference caused by the dispersion of transmitted fiber.

[EN]In general, a sensor is used to monitor a single parameter only, and in many cases, a reference sensor is necessary to compensate the effect of temperature. Here, we demonstrate that a single supermode interferometer is capable of monitoring two parameters simultaneously. Said interferometer was fabricated with a segment of strongly coupled multicore fiber fusion spliced at the end of a standard single mode fiber. The free end of the multicore fiber was flat, thus, it behaved as a low reflectivity mirror whose reflection depended on the external refractive index. The reflection spectrum of our supermode interferometer consisted of well-defined periodic maxima and minima whose values and position varied when the interferometer was exposed to refractive index and temperature changes. In the Fourier domain, the changes of the interference pattern can be decoded easily. We demonstrate that the supermode interferometer here proposed can be useful to measure the thermo-optic coefficient of a sample. An important advantage of the device reported here is that the length of the multicore fiber is not determinant on the performance of the sensor. In addition, the device can be reused multiple times. This work was supported in part by the Ministerio de Economia y Competitividad (Spain) and the European Regional Development Fund under Grants PGC2018-101997-B-I00 and RTI2018-094669-B-C31, and in part by the Departamento de Educacion del GobiernoVasco, underGrant IT933-16.

This paper investigates shortcomings that limit the performance of optical code division multiple access (OCDMA) systems including the low cardinality and data rate as well as the high power at reception. The main drawback for such systems known as multiple access interference accompanying by phase induced intensity noise is also investigated to effeciencly propose a novel two dimensional cyclic shift (2D-CS) code to be implemented in non-coherent OCDMA systems. The developed code is based on a one dimensional cyclic shift (1D-CS) code previously provided by research works processing spectral amplitude coding for optical code division multiple access (SAC-OCDMA) systems. Numerical results obtained by this study are therefore compared to previous studies employing different codes like two dimensional extended double weight (2D-EDW), two dimensional flexible cross correlation/modified double weight (2D-FCC/MDW), two dimensional perfect difference (2D-PD), two dimensional diluted perfect difference (2D-DPD), two dimensional multi service (2D-MS) and two dimensional zero cross correlation/multi diagonal (2D-ZCC/MD) codes. Accordingly, it is demonstrated that the proposed 2D-CS code outperforms all codes given previously in terms of system capacity where the small increasing percentage is about 40% compared to 2D-ZCC/MD and 2D-MS. Systems using 2D-CS code can support until 203 simultaneous users with a total code length equal to 171. System performance investigation leads to a BER and Q-Factor closely to1.0E−12 and 1.0E−27, and 6.6 dB and 10.6 dB at 20 km of single mode fiber length using white light source and Laser, respectively. Furthermore, such a code can be easily adopted by OCDMA systems for a long distance up to approximately 55 and 100 km.

We proposed and experimentally demonstrated a vector bending sensor based on a core-offset long period fiber grating (CO-LPFG). The CO-LPFG is configured by CO2 laser polishing on three mutually orthogonal planes of a single mode fiber (SMF) to different depths and then heating it by the electrical arc-discharge of a fusion splicer. The asymmetrical cladding structure leads to an uneven density distribution of the fiber in the molten state. Under the effects of releasing the residual stress and fiber surface tension, the fiber core deviates toward the polished deeper directions to form a core-offset structure in two dimensions. The experimental results demonstrate that the bending sensitivities of CO-LPFG reach 37.06 nm/m −1 −5.85 nm/m−1-14.59 nm/m−1 and −12.45 nm/m−1 for four bending directions within the range of 1.12-2.10 m−1 The temperature sensitivity of CO-LPFG is 57.90 pm/°C in the range of 40-160°C.

An optical wave microphone, which is well designed based on Fraunhofer diffraction of a laser beam, is expected to be applied to various acoustic fields where conventional microphones cannot be used due to strong electric and/or magnetic field. The authors have developed this technique and applied it to detect discharge sounds emitted from plasmas such as micro plasma, gliding arc plasma and plasma jet. An improved optical wave microphone with regard to signal-to-noise ratio uses single mode optical fibers for laser transformation. In this study, detailed characteristics of the fiber-type optical wave microphone were evaluated according to the theory of the optical wave microphone. Furthermore, the fiber-type optical wave microphone was combined with computer tomography (CT). The fiber-type optical wave microphone CT succeeded to visualize and quantify 2-D acoustic field generated by an ultrasonic transducer, and the obtained sound pressure distribution showed good similarity to that measured with a condenser microphone. Furthermore, the technique was applied to surface barrier discharge with different applied voltage frequencies and the distribution of acoustic waves above the discharge was quantified.

Stable output and beam profile at high power laser operation is a prime requirement for precision high-end manufacturing. The stability of laser charateristics during power scaling in a single-oscillator is limited by several unavoidable non-linear effects. Hence, kW-level power scaling through multiple amplification stages or using signal combination are feasible solutions. In a master oscillator power amplifier (MOPA) architecture, pump-signal combiner with high pump coupling efficiency and low loss signal transmission maintaining seed beam quality during coupling from a single mode fiber into a large mode area fiber, is an important component. In this respect, an effective method of fabricating mode-field matched pump-signal combiner has been presented employing a section of intermediate fiber, having adiabatically tapered core and uniform cladding, along with a conventional signal fiber (termed hybrid signal fiber) inside the input fiber bundle to obtain effective mode-field matching of signal light in between the input fiber bundle and the output fiber. Additionally a taper-less signal combiner design has been proposed for scaling laser power through incoherent combination. The reduced-clad signal fiber with low loss core guidance supports bundling of the input fibers inside an economic low-OH silica tube to obtain good transmission efficiency and beam profile.

This research demonstrates how low loss commercially available multi-mode (MM), perfluorinated polymer optical fibers (POFs) can be used for robust and reliable fiber Bragg grating (FBG) based sensing. A single peak FBG reflection spectrum is achieved by tapering the fiber to a diameter just small enough to make the fiber effectively single-moded and then inscribing the FBG in the waist section of the taper. Here we use plane-by-plane, direct writing inscription with a femtosecond laser. In particular we used the GigaPOF-50SR MM fiber and tapered it by a factor of 0.24, which was found to be the critical ratio that provided a single grating reflection peak. The GigaPOF-50SR fiber was chosen because it allows operation at 1550 nm and has a suitable small 50 μm core diameter, which minimizes the required taper ratio and thus the insertion loss of the taper. The FBG sensor was found to have a strain and relative humidity sensitivity of 20 nm/%strain and ∼ 6.7 pm/%RH, respectively. The grating proved to be largely insensitive to temperature. This approach to single-mode POF sensor fabrication will enable multi-point strain sensing at 1550 nm over 50 m long fiber. It combines the main advantages of single mode POFs (robust FBG sensing) and MM POFs (low transmission loss) and demonstrates that tapered MM POFs constitute an efficient solution for the development of robust and reliable long distance POF FBG sensor networks.

Optical multi-band (OMB) systems exploit the low-loss spectrum of the single mode fiber (SMF) and are key enablers to increase the transportation capacity and node connectivity of already deployed systems. The realization of OMB systems is mainly based on the technological advances on the component and system level, and for this purpose, a broad gamut of various structural elements, such as transceivers, amplifiers, filters, etc. have been commercialized already or are close to commercialization. This wide range of options, which aid in unlocking the concurrent transmission in all amplification bands, is reviewed here for the first time, whilst their pros and cons as well as their limitations are discussed. Furthermore, the needs for additional components in order to fully exploit the ≈390 nm low-loss wavelength range of SMF, which spans from 1260 to 1650 nm, are highlighted. Finally, based on a physical layer formalism, which incorporates the impact of the most important physical layer constraints for an OMB system, the attainable capacity and transparent reach of each amplification band are quantified.

The uniaxial compressive strength (UCS) test is crucial in determining the strength and stiffness behavior of intact rock and is frequently utilized by industry to determine project site characteristics. A fundamental procedure of UCS testing is strain response measurement. Conventionally, discrete strain measuring devices such as extensometers and/or electric foil strain gauges are used to measure the strain response at the mid-height of a specimen. However, this ultimately limits the ability to capture full-field strain of UCS test specimens. This has led to a gap in knowledge in terms of the complexities of UCS test strain responses caused by factors such as specimen heterogeneity and the influence of platen friction. Within this context, a novel distributed optical strain sensing (DOS) technology has been integrated with UCS testing (DOS-UCS technique). Unlike conventional discrete strain measurement methods, the optical technique captures a distributed strain profile along the length of standard, low-cost single mode optical fiber with a spatial sampling resolution of 0.65 mm. By wrapping an optical strain sensor around a UCS specimen, continuous full-field strain profiles along the length and circumference of UCS specimens can be realized. This paper presents a laboratory investigation that illustrates the potential of this technology to provide an in-depth look into the strain response of heterogeneous nodular limestone during UCS testing.

Recent progress in designing optimized microstructured optical fiber spreads an application scenario of optical fiber sensing. In this letter, we demonstrate a novel three-core microstructured optical fiber (TMOF) spliced with single mode fibers (SMFs). Due to low crosstalk and different effective refractive index between three cores in TMOF, multi-beam interference is achieved and verified based on both of experiments and theoretical analysis. In addition, the bending response could also be recorded by the transmission spectrum of TMOF because of the asymmetry of three core effective refractive index. Owing to the consistency of cores responding to temperature changes, the TMOF can effectively suppress the influence of temperature. Theses excellent sensing characteristics indicate the TMOF splicing with SMFs is promising in the field of bending, integrated Mach Zehnder devices and multi-parameter sensing measurement under different temperature.

We study the QSLT of the two-level system coupling to a single mode cavity which is driven by a laser field under the feedback control, and focus on the effect of the Rabi frequency and two types of the feedback on the QSLT. The results show that the QSLT is always less than the driving time, that is, the evolution speed of the two-level system can be accelerated. Whatever types of feedback we use, the QSLT varies with the initial time parameter, both the feedback and the classical field can change the acceleration in the evolution process.