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We investigate N ×1 pump coupler theoretically and experimentally. Firstly the influence of lengths of the transitional region and the waist region of tapered fiber bundle on the efficiency of a 7×1 pump combiner is numerically analyzed. The results suggest that there is a minimum length for the transitional region in order to achieve high efficiency; meanwhile, the waist region should be as short as possible. Then a 7×1 pump combiner is fabricated. The transmission efficiencies of all 7 ports are higher than 98% and the final total output power is as high as 3.81 kW with 98.4% transmission efficiency. This is the highest output power reported to date and improvement further is possible by better cleaving, splicing and using LD with higher power. The experimental result verifies the simulation which can be applied in the fabrication of N ×1 pump combiners. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a trapped yeast cell being launched away from the fiber tip with a certain speed to a certain position without moving the optical fiber in a single fiber optical trapping apparatus. We excite both LP 01 and LP 11 mode beams in a same normal communication fiber core to generate the optical launching force and trapping force by molding the fiber tip into a special tapered-tip shape. A yeast cell of 6 μm diameter is trapped and then being launched away. We construct the optical trapping and launching potential wells by controlling the power of two mode beams. Besides that, we also build a physical model to analyze the micro-particle dynamic behavior characteristics during the launching process. This micro-particle directional launching function expands new features of fiber optical tweezers based on the normal communication fiber, providing for the possibility of more practical applications in the biomedical research fields. [ABSTRACT FROM AUTHOR]

Abstract: We present a novel mode filter operating for the 1060-nm band, which selectively removes the power of the high-order mode (HOM) from a conventional single-mode fiber (C-SMF) that supports two modes at the short-wavelength band. Our mode filter is fabricated very easily by fusion-splicing a short section of short-wavelength single-mode fiber in the middle of the C-SMF link. By using our spliced-fiber mode filter (SF-MF), a high HOM suppression performance of >18dB has been achieved with a low insertion loss of <0.3dB over the full band of optical communications from 1050nm to 1650nm. We have also developed a new mode power measurement scheme that takes advantage of the bending sensitivity of the HOM guidance. This measurement scheme enabled us to evaluate accurately the performance factors of the fabricated mode filter. [ABSTRACT FROM AUTHOR]

Abstract: The temporal Radon–Wigner transform (RWT), which is the squared modulus of the fractional Fourier transform (FRT) for a varying fractional order p, is here employed as a tool for pulse compression applications. To synthesize the compressed pulse, a selected FRT irradiance is optically produced employing a photonic device that combines phase modulation and dispersive transmission. For analysis purposes, the complete numerical generation of the RWT with 0< p <1 is proposed to select the value of p required for pulse compression. To this end, the amplitude and phase of the signal to be processed should be known. In order to obtain this information we use a method based on the recording of two different FRT irradiances of the pulse. The amplitude and phase errors of the recovered signal, which are inherent to the recording process, are discussed in connection with the RWT production. Numerical simulations were performed to illustrate the implementation of the proposed method. The technique is applied to compress signals commonly found in fiber optic transmission systems, such as chirped gaussian pulses, pulses distorted by second and third-order dispersion and nonlinear self-modulated pulses. [Copyright &y& Elsevier]

A novel graphene-enabled electrically tunable optical filter (ETOF) was reported in this work with high voltage response, low power consumption, and wide working bandwidth. A fiber Bragg grating (FBG) was etched in a microfiber using a femtosecond laser, and porous graphene film was coated on the surface of a tapered fiber. Metal electrodes were fabricated using which a voltage was applied to the graphene film to heat the fiber. The wavelength shift of the ETOF has a linear relationship with the applied voltage. The devices illustrated good repeatability and the voltage sensitivity was calculated as 50.36 pm/V. A maximum voltage of 30 V was applied to the devices and a 1.62-nm wavelength shift was observed. The 3-dB bandwidth of the FBG was approximately 0.38 nm, which corresponds to a power consumption of 5.76 μ W in the device. The rising and falling times of the device were measured as 44.2 and 26.7 ms, respectively. [ABSTRACT FROM AUTHOR]

Abstract: This communication reports a simple configuration for the implementation of a compact and all-fiber based width-tunable pulse generator using four-wave mixing (FWM) effect in only 1.9-m of bismuth oxide based highly nonlinear fiber (Bi-HNLF). The width- tunable pulses are generated at repetition rates of 5 and 10GHz. In the performed experiment, the pulsewidth of a 5GHz repetition rate pulse train is tuned from 83 to 23ps whereas the pulsewidth of a 10GHz repetition rate pulse train is continuously tuned from 32 to 18ps. An analytical model is presented for width-tunable pulse generation and the results agree well with the experimental findings. The effects of pump source timing jitter and intensity fluctuation on pulse generation are discussed. [Copyright &y& Elsevier]

An all-fiber dynamic gain slope compensator is demonstrated, based on Mach–Zehnder interferometer design. Low voltage and electrical power are used to tune the attenuation slope via thermo-optic effect. A constant average insertion loss mode is demonstrated. [Copyright &y& Elsevier]

A simple, accurate and fast method for synthesizing the physical parameters of a fiber Bragg grating (FBG) structure from its reflectivity is proposed and demonstrated. The method is based on a simulated annealing (SA) optimization algorithm and can be applied over uniform and nonuniform (apodized, chirped) FBGs. The SA technique is specially suited for the complete characterization (including phase characterization) of FBG structures from reflectivity measurements. As an example, the proposed technique is successfully applied to synthesize and characterize an experimental linearly chirped FBG from its measured reflectivity. [Copyright &y& Elsevier]

We present a new method of compensating linear birefringence always present in mechanically induced long-period fiber gratings (MLPFGs). With the proposed compensation method the MLPFGs became polarization insensitive and the polarization mode dispersion of the MLPFGs was substantially reduced. [Copyright &y& Elsevier]

Experimental realization of a high-power and highly uniform multiwavelength cw erbium-doped fiber ring laser with an intra-cavity frequency shifter and line spacing of 100 GHz is presented. The extremely flat response is achieved by optimizing the laser cavity losses, pump power and length of the active fiber. A simple method of shifting the laser emitting spectral region, which preserves the spectral output flatness, is demonstrated. The laser may be easily switched between two spectral regions of 1538–1548 and 1543–1559 nm. In both ranges, the power uniformity is better than 3 dB. [Copyright &y& Elsevier]

Novel fiber microprobe comprising a nanostructured gradient index optical vortex phase mask and single-mode fiber was investigated numerically and experimentally. The mask which, consists of spatially distributed sub-wavelength nanorods, was fabricated via the modified stack-and-draw fiber drawing technique. The mask has flat input and output surfaces and transverse dimensions of a standard single-mode fiber. The microprobe allows efficient generation of high-quality optical vortex beams in different environments such as air and water. • Novel fiber microprobe for the generation of the optical vortex beam. • The probe comprising a nanostructured gradient index vortex mask. • The optical performance of the probe is confirmed by optical experiments. • Ideal vortex generator for optofluidic applications is presented. • The probe facilitate optical trapping, and high power vortex beam micromachining. [ABSTRACT FROM AUTHOR]