Jitter-free, dual-wavelength, ultrashort-pulse, energetic fiber sources using soliton self-mode conversion.

We demonstrate an energetic dual-wavelength ultrashort pulsed source by exploiting the inherent features of the newly discovered process of soliton self-mode conversion (SSMC) in a multimode fiber. The generated pulses are at wavelengths of 1205 nm and 1273 nm, respectively, and the pulse energies are approximately 30 nJ. The natural group-velocity-locking feature of SSMC ensures minimal relative timing jitter, hence highlighting the utility of exploiting the new degrees of freedom afforded by field of multimode nonlinear fiber optics. The relative timing jitter is evaluated by measuring the power fluctuations of generated sum-frequency signals. When compared to a conventional fiber based dual-wavelength source based on traditional frequency-shifted solitons, the relative timing jitter is found to be reduced by greater than 11 dB. Since this process is wavelength-agnostic within the transparency window of optical fibers, our source provides an attractive means of achieving integrated multi-color ultrashort pulse sources for a variety of applications.

Long period grating assistant photonic crystal fiber modal interferometer.

A novel in-fiber modal interferometer based on a long period grating (LPG) inscribed in a two-mode all-solid photonic bandgap fiber (AS-PBGF) is presented. After inserting a small piece of the AS-PBGF into two sections of standard single-mode fiber (SMF) via being spliced slight core offset, LPG is inscribed in the AS-PBGF. The LPG is especially designed to realize the coupling between two core modes of LP01 and LP11 in the AS-PBGF. Two core modes LP01 and LP11 of the AS-PBGF are excited firstly at the input spliced point and actualized energy exchange when they pass through the LPG. Then the two beams will interfere at the output spliced point to form a high-contrast in-fiber modal interferometer. The proposed interferometer has some advantages such as configuration compact, high interference contrast and the wavelength spacing well controlled by changing the position of the LPG without changing the total length of AS-PBGF.

High order resonances between core mode and cladding supermodes in long period fiber gratings inscribed in photonic bandgap fibers.

High order resonances between fundamental core mode and cladding LP(01) supermodes are demonstrated in long period fiber gratings (LPFGs) inscribed in all-solid photonic bandgap fibers for the first time to our knowledge. The resonance wavelengths of the LPFGs calculated by way of photonic bandgap theory agree with the experimental results. The temperature responses of these resonance peaks have been theoretically and experimentally investigated. In addition, the mechanism of LPFG formation has been researched deeply through coupled-mode theory (CMT) and the cutback experiments.

Avoided-crossing-based ultrasensitive photonic crystal fiber refractive index sensor.

We propose and demonstrate an ultrasensitive photonic crystal fiber refractive index sensor by introducing the avoided-crossing effect in a bent-controlled fluid-filled photonic-bandgap fiber (FF-PBGF). By controlling the bend radius of the FF-PBGF, resonant couplings between the fundamental core mode and the cladding modes are realized and transmission notches are observed in the transmission band of the FF-PBGF. By changing the refractive index or temperature of the bent FF-PBGF, a sensitivity of 32,400 nm per refractive index unit (or 13.1 nm/degrees C) is achieved, which is the highest for a fiber device to date, to our best knowledge.

Simultaneous force and temperature measurement using long-period grating written on the joint of a microstructured optical fiber and a single mode fiber.

A novel approach to simultaneous force and temperature measurement is proposed and demonstrated in this paper. The sensing element is based on a single long-period grating (LPG) formed by irradiating the joint of a microstructured optical fiber (MOF) and standard single mode fiber (SMF) with CO(2) laser pulses. The grating exhibits two groups of attenuation bands with distinctly different responses to temperature and force: the resonant notches in the MOF involving couplings between fundamental mode and core LP(11) modes are almost temperature insensitive but highly sensitive to force, while resonant notches in the SMF coming out of couplings between fundamental mode and cladding modes show high sensitivity to temperature but marginal sensitivity to force. Based on the LPG, a simple and efficient dual-parameter sensor simultaneously measuring temperature and force with a sensitivity of approximately 0.086 nm/degrees C and approximately -2.18 nm/N, respectively, is achieved. Furthermore, we propose a simple sensing configuration for simultaneous strain and temperature measurement.