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This letter presents an experimental method to compensate for the differential group delay between the core modes in a multi-core fiber. Optical fiber sections are sequentially spliced with azimuthal offsets such that light initially launched to any cores can propagate through the combination of the same lengths of different cores, resulting in ideally uniform group delay. The differential group delays before and after the compensation are measured by wavelength-domain Mach-Zehnder interferometry through multi-core fiber sections. The experimental results show that the group delay compensation is practically limited by non-uniformity of the multi-core fiber. [ABSTRACT FROM PUBLISHER]

We demonstrate a highly efficient acoustooptic mode converter for selective excitation of the higher-order modes in a four-mode fiber which guides the LP01, LP11, LP21, and LP02 modes at telecommunication wavelengths. The coupling efficiency and the mode extinction ratio are measured by analyzing the output far-field patterns. The acoustic resonance frequencies and the operating bandwidths are compared with the theoretical results, by which the modal characteristics, the core diameter, and the core-cladding index difference are estimated. [ABSTRACT FROM PUBLISHER]

This paper describes a novel non-contact laser-ultrasound system which is compact and has a high level of immunity to ambient vibration, based on the use of an optical fibre Fabry–Perot interferometer as an acoustic detector. The new optical acoustic detector was employed for measuring a high-frequency acoustic wave of small amplitude generated by a relatively low output power source using an erbium-doped fibre amplifier. Together with the characteristics of the proposed detector, the preliminary results of 80 MHz laser-ultrasound experiments on an aluminium film are described. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate a novel all-fiber wavelength-tunable acoustooptic switch utilizing intermodal coupling in a two-mode fiber (TMF). Its all-fiber configuration consisting of a fiber acoustooptic tunable filter and a mode-selective coupler results in the low loss (<2 dB) operation. The operating bandwidth >50 nm, the switching time of 40 μsec, and the crosstalk of 20 dB were achieved. By controlling the design parameters of the two-mode fiber, the 3-dB bandwidth of the switched signal was varied from 2.5 nm to >35 nm. A novel all-fiber dynamic optical add-drop multiplexer is also demonstrated using two acoustooptic switches in series. [ABSTRACT FROM PUBLISHER]

We propose and experimentally demonstrate a novel configuration for an acoustooptic tunable bandpass filter based on intermodal coupling in a two-mode fiber. The double-pass scheme provides zero frequency-shift, bandwidth narrowing, and enhanced extinction ratio. A 3-dB bandwidth of 2.0 nm, insertion loss of 5.6 dB, and sidelobe suppression ratio of 14 dB were achieved. The wavelength tuning range was greater than 90 nm for the transmission dynamic range larger than 20 dB. Multiwavelength operation of a single device is achieved by simply applying multifrequency electrical signal. Unwanted intensity modulation of the multiwavelength filter is also investigated [ABSTRACT FROM PUBLISHER]

We demonstrate a narrow-bandwidth acoustooptic tunable filter with very low polarization-sensitivity using a dispersion-compensating fiber that has a large group index difference between the core and the cladding modes with a specific stress distribution. The 3-dB bandwidth of the filter is 0.8 nm with the interaction length of 10 cm, and the polarization-dependent center-wavelength splitting is 0.04 nm at the wavelength around 1550 nm. The origin of the low polarization-dependence is successfully explained through the analysis on the stress field in the fiber. [ABSTRACT FROM PUBLISHER]

We demonstrate a novel tunable narrow-bandwidth optical filter based on an acoustically modulated fiber Bragg grating (FBG). A flexural acoustic wave applied to an off-centered core FBG modulates the period of the grating, producing sidebands tunable both in wavelength and magnitude. [ABSTRACT FROM PUBLISHER]

We demonstrate a novel optical frequency-domain reflectometry system with compactness and short measurement time based on the use of a wavelength-swept mode-locked fiber laser. The optical source uses an intracavity tunable Fabry-Perot filter as a tuning element. The fiber laser sweeps 20 nm in less than 10 ms. Spatial resolution of 100 μm and total measurement range of several centimeters are demonstrated. [ABSTRACT FROM PUBLISHER]

We demonstrate a novel all-fiber add-drop multiplexer by using a tilted Bragg grating written on a two-mode fiber and a mode-selective coupler. The device can be made potentially with low loss and low cost, useful for add-drop of a small number of channels in wavelength-division-multiplexing (WDM) communication systems [ABSTRACT FROM PUBLISHER]