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InGaN-based orange-red resonant cavity light-emitting diodes (RCLEDs), were fabricated by using an AlN current-confinement aperture and double dielectric distributed Bragg reflectors (DBRs). For realizing the structure of device, a substrate transfer technique was employed in process of fabrication. The device exhibited optical resonant effect, a high Q factor (∼3010), and a narrow emission linewidth (FMHW ∼0.2 nm), indicating low optical loss in the resonant cavity. Additionally, due to the three-dimensional (3D) optical confinement effect, the discrete modes of red emission were clearly observed in the far field via an angular resolved measurement system. And then, the energies of the photon states of a red RCLED consists generally with the simulation results based on a circular waveguide model. The saturated emission intensity of the orange-red RCLED was proportional to the area of current injection. This work demonstrated the feasibility of InGaN-based electrically injected orange-red RCLEDs that are useful for the development of displays and communication systems. [ABSTRACT FROM AUTHOR]

To capture vibration waveforms whose frequencies exceed the limitation set by sensing fiber length in Φ–OTDR distributed vibration sensing (DVS), we propose a sampling rate enhancement technique based on frequency-division-multiplexing (FDM). Our proposal, unlike conventional FDM-based sampling rate enhancement methods, directly eliminates inherent distortion by using complementary frequency concept with new probe pulse sequence. The proposed method can suppress the distortion of arbitrary waveforms in regular fiber without prior knowledge of the vibration. The proposal can accurately measure vibration waveforms and fully characterize the vibration on a standard single-mode fiber; it determines not only the frequency but also the correct amplitude and the exact shape of the vibration. Furthermore, our distortion compensation scheme incorporates a state-of-the-art FDM-based fading suppression technique, yielding high sampling rates and high sensitivity simultaneously. We demonstrate the validity of the proposal by proof-of-concept experiments in which the number of multiplexed frequencies is set to three for both sampling rate enhancement and fading suppression. In creating the experimental setup, we take the great care with the optical pulse shape and the carrier frequencies to avoid crosstalk. We successfully measure vibration waveforms with frequencies ranging from 1 kHz to 9 kHz on a sensing fiber with length of about 12 km. [ABSTRACT FROM AUTHOR]

Distributed vibration sensing (DVS) utilizes an optical fiber as an array of virtual strain sensors. It can reveal dynamic strain distributions such as seismic events and car traffic, thus giving a new function to existing optical communication fibers. In this work, we use optical frequency domain reflectometry (OFDR) to investigate the dynamic strain distribution along an optical fiber implemented in a deployed aerial optical fiber cable that vibrates with the wind. The OFDR setup is customized for distant location interrogation with a high repetition rate of the probe light and overcomes the OFDR drawbacks of short measurement range and low repetition rate, thus enabling application to the investigation of dynamic strain along a range of telecommunications outside a plant. Sub-1-m spatial resolution measurements revealed that dynamic strain along the optical fiber in an aerial cable depends on the deployment condition. It also provides the deployed optical telecommunication fiber with a function for visualizing the deployment conditions of the telecommunications outside plants. [ABSTRACT FROM AUTHOR]

To suppress coherent fading in Φ-OTDR distributed vibration sensing (DVS) with frequency-division-multiplexing (FDM), we propose an efficient methodology named the double averaging approach that processes complex vectors of Rayleigh scattered light on IQ plane. The double averaging approach rotates and averages complex vectors across the time domain as well as the optical frequency domain; this yields the final phase representing the vibration with less phase noise than the conventional method. This allows the proposal to prevent the phase unwrapping failures caused by the noise and improve the vibration detection sensitivity without incurring penalties in detection bandwidth or system complexity. The proposal is also effective in suppressing the vibration waveform distortion permitted by the conventional method. We confirm the effectiveness of the proposal through experiments in which we apply nϵ-level vibrations to an over 5 km sensing fiber and perform Φ-OTDR DVS by using FDM pulses composed of three optical frequencies. [ABSTRACT FROM AUTHOR]

We demonstrated amber InGaN $47\times 47\,\,\mu \text{m}^{{2}}$ micro-light-emitting diodes ($\mu $ LEDs) with the peak wavelength of 606 nm and full-width at maximum (FWHM) of 50 nm at 20 A/cm2. The amber $\mu $ LEDs exhibited a 33-nm blue-shift of the peak wavelength and obtain broader FWHMs to approximately 56 nm at 5 to 100 A/cm2. The peak on-wafer external quantum efficiency was 0.56% at 20 A/cm2. The characteristic temperature was 50–80 K at 20 to 60 A/cm2 but increased to 120–140 K at 80 to 100 A/cm2. The strong increase in the characteristic temperature from 60 to 80 A/cm2 could mainly be attributed to the saturation of the Shockley-Read-Hall non-radiative recombination at high current densities. [ABSTRACT FROM AUTHOR]

The spot size at which the electric field distribution for higher-order modes in few-mode fibers (FMFs) is approximated by a higher-order Gaussian profile is a promising parameter for estimating various transmission characteristics. To establish a technique for measuring the mode field diameter (MFD) corresponding to higher-order Gaussian spot size for any-order mode in FMFs, we investigate the relation between the higher-order Gaussian spot size and the values yielded by conventional MFD definitions. We then present formulas that output the MFD values corresponding to higher-order Gaussian spot size. Some examples of the MFD values for typical few-mode fibers determined experimentally and numerically are also shown. [ABSTRACT FROM AUTHOR]

We investigate the impact of the frequency modulation induced by vibration occurring at a preceding distance in distributed acoustic sensing (DAS) based on optical frequency domain reflectometry (OFDR), which analyzes a vibration waveform by calculating the spectrum shift of Rayleigh backscattered light in the same manner as a fiber Bragg grating. When the measurement time of a beat signal is shorter than the period of the vibration at the preceding distance, the vibration-induced frequency modulation can be treated as a frequency offset for the backscattered light. The frequency offset becomes a distance offset through the distance - beat frequency allocation of OFDR, and the distance offset forces us to interrogate the Rayleigh backscattered light spectra at unintentional distances for each measurement since the distance offset is time-varying. Since the spectra at unintentional distances are uncorrelated, the spectrum shift calculated with an uncorrelated spectrum results in a spurious vibration, which is a measured waveform that is different from the actual vibration waveform and that constitutes a measurement error in a DAS measurement. We propose a technique to compensate for the spurious vibration. The technique estimates the vibration-induced distance offset by calculating the cross-correlation between Rayleigh backscattered light waveforms and shifts the spectrum analysis range by the estimated offset in order to track the consistent spectrum. We perform a DAS measurement on a sensing fiber that experiences simultaneous vibrations at different distances and confirm the validity of the proposed technique. [ABSTRACT FROM AUTHOR]

This paper presents impulse response measurements of few-mode optical fibers and transmission lines that were obtained by using coherence-recovered linear optical sampling or a two-comb interferometer. When performing a measurement, the probe pulse source and the sampling pulse source may be far from each other, particularly when the fibers are installed in the field, and the fiber length may exceed several tens kilometers. In this paper, by modifying a previously proposed referencing technique, the coherence between two pulse lasers is equivalently maintained by canceling out the phase noise caused both by the light sources and perturbations in the fiber. Hence, the amplitude averaging is used to enhance the signal-to-noise ratio. As a result, we can measure the impulse responses of multimode fibers with a dynamic range of 80 dB and a time resolution of a few picoseconds, over tens nanoseconds of differential mode delay. [ABSTRACT FROM PUBLISHER]