Theory of parabolic pulse generation in tapered fiber

We examine similarities and differences between high-power parabolic pulse generation in an active medium and in tapered fiber with decreasing normal dispersion. Using a realistic tapered fiber design, we demonstrate the possibility of parabolic pulse generation without an external pump and determine the limitations of this approach. © 2007 Optical Society of America.

Fiber Bragg gratings inscribed using 800nm femtosecond laser and a phase mask in singleand multi-core mid-IR glass fibers

For the first time, Fiber Bragg grating (FBG) structures have been inscribed in single-core passive germanate and three-core passive and active tellurite glass fibers using 800 nm femtosecond (fs) laser and phase mask technique. With fs peak power intensity in the order of 10(11)W/cm(2), the FBG spectra with 2nd and 3rd order resonances at 1540 and 1033 nm in the germanate glass fiber and 2nd order resonances at approximately 1694 and approximately 1677 nm with strengths up to 14 dB in all three cores in the tellurite fiber were observed. Thermal responsivities of the FBGs made in these mid-IR glass fibers were characterized, showing average temperature responsivity approximately 20 pm/ degrees C. Strain responsivities of the FBGs in germanate glass fiber were measured to be 1.219 pm/microepsilon.

Novel design of FBG-based composite double notch VSB filter for DWDM systems

This paper proposes a novel design of optical filters based on a cascade of tailored fiber Bragg gratings (FBGs) operating in the transmission regime. As an example of the application of the proposed general technique, ultranarrow optical vestigial sideband (VSB) filtering based on two FBGs operating in the transmission regime was examined. This design can be easily implemented by writing FBG-based filters for each wavelengthdivision-multiplexing channel before multiplexing. © 2006 IEEE.

Catalytic systems based on carbon fiber materials for the low-temperature oxidation of carbon monoxide

New heterogenized catalytic systems for the low-temperature oxidation of CO were synthesized by supporting solutions of Pd, Cu, and Fe salts on carbon fibrous materials (carbopon and busofit). The carbon supports were studied by elemental analysis, SEM, TGA, and TPD. The effects of the nature of the support, the concentration and composition of the active component, and the conditions of preparation on the efficiency of the catalytic system were studied. It was ascertained that attenuation of hydrophilic properties of the support led to the decrease in system activity. The investigation of the catalysts by XPS showed that sample treatment in the reaction medium results in redistribution of the components of the active phase in the near-surface layer of the catalyst. The catalytic system based on carbon fibrous material carbopon prepared by supporting active components (Pd, Cu, and Fe salts) in three stages with intermediate activation in the reaction medium ensures 95% conversion of CO under respiratory conditions, and is promising for the design of the main element of breathing masks on its basis.

Surface modification of natural fibers using bacteria:depositing bacterial cellulose onto natural fibers to create hierarchical fiber reinforced nanocomposites

Triggered biodegradable composites made entirely from renewable resources are urgently sought after to improve material recyclability or be able to divert materials from waste streams. Many biobased polymers and natural fibers usually display poor interfacial adhesion when combined in a composite material. Here we propose a way to modify the surfaces of natural fibers by utilizing bacteria (Acetobacter xylinum) to deposit nanosized bacterial cellulose around natural fibers, which enhances their adhesion to renewable polymers. This paper describes the process of modifying large quantities of natural fibers with bacterial cellulose through their use as substrates for bacteria during fermentation. The modified fibers were characterized by scanning electron microscopy, single fiber tensile tests, X-ray photoelectron spectroscopy, and inverse gas chromatography to determine their surface and mechanical properties. The practical adhesion between the modified fibers and the renewable polymers cellulose acetate butyrate and poly(L-lactic acid) was quantified using the single fiber pullout test. © 2008 American Chemical Society.

Raman fiber source for the 1.6–1.75 μm spectral region

We propose and experimentally realize a composite Raman converter based on P-doped and Gedoped fibers. The converter has an emission wavelength of 1.649 μm and an output power of 1.2 W. Numerical simulation of the configuration suggested was performed. A similar converter scheme can be used to build sources with any emission wavelength in the range from 1.6 to 1.75 μm.

How optical spectrum of random fiber laser is formed

We experimentally and theoretically describe formation of random fiber laser's optical spectrum. We propose a new concept of active cycled wave kinetics from which we derive first ever nonlinear kinetic theory describing laser spectrum. © OSA 2015.

Super-high temperature sensitivity of long-period gratings in B/Ge co-doped fiber

Long period fiber grating (LPFG) can be used as active gain controlling device in EDFA. However, LPFGs fabricated in the standard telecom fiber only have a typical temperature sensitivity of 3-10nm/100°C, which may not be sufficient for implementing tuneable filters capable of wide tuning range and high tuning efficiency. In this paper, we report a theoretical and experimental investigation of thermal properties of LPFGs fabricated in B/Ge co-doped optical fiber. We have found that the temperature sensitivity of the LPFGs in the B/Ge fiber is considerably increased compared with those produced in the standard fiber. The LPFGs written in the B/Ge fiber have achieved, on average, one order of magnitude higher sensitivity than that of the LPFGs produced in the standard telecom fiber. We have also identified that the thermal response of LPFG is strongly dependent on the order of the coupled resonant cladding mode. The maximum sensitivity of 1.75nm/°C achieved by the 10th cladding mode of the 240μm LPFG is nearly 24 times that of the minimum value (0.075nm/C) exhibited by the 30th mode of the 34μm LPFG. Such devices may lead to high-efficiency and low-cost thermal/electrical tunable loss filters or sensors with extremely high temperature resolution.

Resonant cavity time-division-multiplexed fiber Bragg grating sensor interrogator

The first resonant-cavity time-division-multiplexed (TDM) fiber Bragg grating sensor interrogation system is reported. This novel design uses a pulsed semiconductor optical amplifier in a cyclic manner to function as the optical source, amplifier, and modulator. Compatible with a range of standard wavelength detection techniques, this optically gated TDM system allows interrogation of low reflectivity "commodity" sensors spaced just 2 m apart, using a single active component. Results demonstrate an exceptional optical signal-to-noise ratio of 36 dB, a peak signal power of over +7 dBm, and no measurable crosstalk between sensors. Temperature tuning shows that the system is fully stable with a highly linear response. © 2004 IEEE.

Impact of the order of cavity elements in all-normal dispersion ring fiber lasers

Nonlinearity plays a critical role in the intra-cavity dynamics of high-pulse energy fiber lasers. Management of the intra-cavity nonlinear dynamics is the key to increase the output pulse energy in such laser systems. Here, we examine the impact of the order of the intra-cavity elements on the energy of generated pulses in the all-normal dispersion mode-locked ring fiber laser cavity. In mathematical terms, the nonlinear light dynamics in resonator makes operators corresponding to the action of laser elements (active and passive fiber, out-coupler, saturable absorber) non-commuting and the order of their appearance in a cavity important. For the simple design of all-normal dispersion ring fiber laser with varying cavity length, we found the order of the cavity elements, leading to maximum output pulse energy.

Optical loading sensor based on single polarization fiber laser incorporating an intra-cavity 45°-TFG

We have experimentally demonstrated an active loading sensor system based on a fiber ring laser with single-polarization output using an intra-cavity 45°-tilted fiber grating (45°-TFG). When the laser cavity fiber subjected to loading, the laser output is encoded with the load and can be measured and monitored by a power metre. A loading sensitivity as high as 0.033/ (kg·m-1) has been achieved using this laser. The experiment results clearly show that single polarization fiber laser may be developed to a low-cost high-sensitivity loading sensor system. © 2014 SPIE.

Fiber optically integrated cost-effective spectrometer for optical coherence tomography

A tilted fiber Bragg grating (TFBG) was integrated as the dispersive element in a high performance biomedical imaging system. The spectrum emitted by the 23 mm long active region of the fiber is projected through custom designed optics consisting of a cylindrical lens for vertical beam collimation and successively by an achromatic doublet onto a linear detector array. High resolution tomograms of biomedical samples were successfully acquired by the frequency domain OCT-system. Tomograms of ophthalmic and dermal samples obtained by the frequency domain OCT-system were obtained achieving 2.84 μm axial and 10.2 μm lateral resolution. The miniaturization reduces costs and has the potential to further extend the field of application for OCT-systems in biology, medicine and technology. © 2014 SPIE.

Cost-effective optical coherence tomography spectrometer based on a tilted fiber Bragg grating

A compact, fiber-based spectrometer for biomedical application utilizing a tilted fiber Bragg grating (TFBG) as integrated dispersive element is demonstrated. Based on a 45° UV-written PS750 TFBG a refractive spectrometer with 2.06 radiant/μm dispersion and a numerical aperture of 0.1 was set up and tested as integrated detector for an optical coherence tomography (OCT) system. Featuring a 23 mm long active region at the fiber the spectrum is projected via a cylindrical lens for vertical beam collimation and focused by an achromatic doublet onto the detector array. Covering 740 nm to 860 nm the spectrometer was optically connected to a broadband white light interferometer and a wide field scan head and electronically to an acquisition and control computer. Tomograms of ophthalmic and dermal samples obtained by the frequency domain OCT-system were obtained achieving 2.84 μm axial and 7.6 μm lateral resolution. © 2014 SPIE.

InP-based active and passive components for communication systems at 2 μm

Progress on advanced active and passive photonic components that are required for high-speed optical communications over hollow-core photonic bandgap fiber at wavelengths around 2 μm is described in this paper. Single-frequency lasers capable of operating at 10 Gb/s and covering a wide spectral range are realized. A comparison is made between waveguide and surface normal photodiodes with the latter showing good sensitivity up to 15 Gb/s. Passive waveguides, 90° optical hybrids, and arrayed waveguide grating with 100-GHz channel spacing are demonstrated on a large spot-size waveguide platform. Finally, a strong electro-optic effect using the quantum confined Stark effect in strain-balanced multiple quantum wells is demonstrated and used in a Mach-Zehnder modulator capable of operating at 10 Gb/s.

Optical loading sensor based on ring-cavity fiber laser incorporating a 45°-tilted fiber polarizing grating

We have experimentally demonstrated an active loading sensor system based on a fiber ring laser with singlepolarization output using an intra-cavity 45°-tilted fiber grating. When the laser cavity fiber is subjected to loading, the laser output is encoded with the loading information that can be measured and monitored by a standard power meter. The achieved loading sensitivity is 0.033/kg • m-1 and 0.042/kg • m-1 for two different interaction lengths. The experimental results clearly show that such a single-polarization fiber laser may be commercially developed into a low-cost, high-sensitivity loading sensor system.