Optical fiber tag based on ultra-low-loss encoded fiber cladding grating arrays.

Optical fibers are commonly employed in telecommunications for transmitting data. However, it is difficult to distinguish optical conduits from one another when servicing data transmission cables due to the large number of optical fibers and optical cables. Conventional methods of physically marking fibers are cumbersome, and the label information is accessible to any potential user.

High-spatial-resolution 2D shape sensing based on OFDR using adaptive spectrum method with narrow sweep range.

What we believe to be a novel wavelength shift demodulation method for optical frequency domain reflectometry (OFDR), i.e., adaptive spectrum method (ASM), was proposed and demonstrated to achieve high-spatial-resolution two-dimensional (2D) shape sensing with a narrow sweep range.

High-spatial-resolution quasi-distributed acoustic sensing with phase noise suppression based on φ-OFDR.

A quasi-distributed acoustic sensor with high-spatial-resolution based on phase-sensitive optical frequency domain reflectometry (φ-OFDR) was demonstrated. The source of noise that affects the accuracy of phase demodulation was analyzed. Two low noise linear frequency sweeps (LFSs) with different sweep ranges obtained by injection-locking method were used to achieve high-spatial-resolution and long-distance sensing.

Length-extended 3D shape sensor using wavelength/space-division multiplexing grating arrays in a multicore fiber.

Limited by the multiplexing number of fiber Bragg grating (FBG), further improvement in the length of 3D shape sensing based on FBG technology is challenging. In this Letter, a wavelength-division and space-division multiplexing multicore fiber grating method is proposed, which extends the sensing length. Employing the femtosecond-laser point-by-point technology, we inscribed WDM grating arrays in six outer cores of a seven-core fiber, respectively.

OFDR shape sensor based on a femtosecond-laser-inscribed weak fiber Bragg grating array in a multicore fiber.

An optical frequency domain reflectometry (OFDR) shape sensor was demonstrated based on a femtosecond-laser-inscribed weak fiber Bragg grating (WFBG) array in a multicore fiber (MCF). A WFBG array consisting of 60 identical WFBGs was successfully inscribed in each core along a 60 cm long MCF using the femtosecond-laser point-by-point technology, where the length and space of each WFBG were 2 and 8 mm, respectively. The strain distribution of each core in two-dimensional (2D) and three-dimensional (3D) shape sensing was successfully demodulated using the traditional cross correlation algorithm, attributed to the accurate localization of each WFBG.

1.2 W single-frequency Tm/Ho co-doped fiber oscillator at 2050 nm.

In this Letter, a watt-level single-frequency fiber oscillator at 2050 nm was demonstrated for the first time, to the best of our knowlegde, in a linear laser cavity with a piece of an un-pumped Tm/Ho co-doped fiber serving as a saturable absorber. With delicate optimization of mode filtering effect of the dynamic gratings formed in the saturable absorber, a maximum single-frequency laser output power of 1.2 W was achieved under a total bidirectional pump power of 5.

Wide-range OFDR strain sensor based on the femtosecond-laser-inscribed weak fiber Bragg grating array.

A wide-range OFDR strain sensor was demonstrated based on femtosecond-laser-inscribed weak fiber Bragg grating (WFBG) array in standard SMF. A WFBG array consisting of 110 identical WFBGs was successfully fabricated along a 56 cm-long SMF. Compared with SMF, the cross-correlation coefficient of WFBG array was improved to 0.

Ultra-linear broadband optical frequency sweep for a long-range and centimeter-spatial-resolution OFDR.

We demonstrated a long-range and centimeter-spatial-resolution optical frequency domain reflectometry (OFDR) system based on an ultra-linear broadband optical frequency sweep. The high nonlinear sweeping effect of the distributed feedback (DFB) diode laser was suppressed by a pre-distortion method, ensuring that the injection-locking process remained stable during fast tuning over a large span. An optical linear frequency sweep (LFS) with a sweep range and sweep rate of up to 60 GHz and 15 THz/s, respectively, was ultimately obtained by optimizing the injection-locking system.

Submillimeter-spatial-resolution φ-OFDR strain sensor using femtosecond laser induced permanent scatters.

A φ-optical frequency domain reflectometry (OFDR) strain sensor with a submillimeter-spatial-resolution of 233 µm is demonstrated by using femtosecond laser induced permanent scatters (PSs) in a standard single-mode fiber (SMF). The PSs-inscribed SMF, i.e.

Distributed Refractive Index Sensing Based on Etched Ge-Doped SMF in Optical Frequency Domain Reflectometry.

A distributed optical fiber refractive index sensor based on etched Ge-doped SMF in optical frequency domain reflection (OFDR) was proposed and demonstrated. The etched Ge-doped SMF was obtained by only using wet-etching, i.e.

Nonparaxial propagation and the radiation forces of the chirped circular Airy derivative beams.

In this paper, we investigate the nonparaxial propagation dynamics of the chirped circular Airy derivative beams (CCADBs) based on vector angular spectrum method. In the case of nonparaxial propagation, the CCADBs still maintains excellent autofocusing performances. Derivative order and chirp factor are two important physical quantities of the CCADBs to regulate the nonparaxial propagation characteristics, such as focal length, focal depth and K-value.

High-Spatial-Resolution OFDR Distributed Temperature Sensor Based on Step-by-Step and Image Wavelet Denoising Methods.

A high-spatial-resolution OFDR distributed temperature sensor based on Au-SMF was experimentally demonstrated by using step-by-step and image wavelet denoising methods (IWDM). The measured temperature between 50 and 600 °C could be successfully demodulated by using SM-IWDM at a spatial resolution of 3.2 mm.

High-Temperature-Resistant Fiber Laser Vector Accelerometer Based on a Self-Compensated Multicore Fiber Bragg Grating.

We propose and demonstrate a novel high-temperature-resistant vector accelerometer, consisting of a ring cavity laser and sensing probe (i.e., fiber Bragg gratings (FBGs)) inscribed in a seven-core fiber (SCF) by using the femtosecond laser direct writing technique.

High-quality fiber Bragg grating inscribed in ZBLAN fiber using femtosecond laser point-by-point technology.

We demonstrate for the first time, to the best of our knowledge, the fabrication of a high-quality fiber Bragg grating (FBG) in ZBLAN fiber by using an efficient femtosecond laser point-by-point technology. Two types of FBG, e.g.

Quasi-Distributed Temperature and Strain Sensors Based on Series-Integrated Fiber Bragg Gratings.

Two types of series-integrated fiber Bragg gratings (SI-FBGs), i.e., strong and weak SI-FBGs, were inscribed in a standard single-mode fiber (SMF) using the femtosecond laser point-by-point technology.

Orbital Angular Momentum Mode Sensing Technology Based on Intensity Interrogation.

A novel optical fiber sensing technology based on intensity distribution change in orbital angular momentum (OAM) mode is proposed and implemented herein. The technology utilizes a chiral long-period fiber grating (CLPFG) to directly excite the 1st-order OAM (OAM) mode. The intensity changes in the coherent superposition state between the fundamental mode and the OAM mode at the non-resonant wavelength of the CLPFG is tracked in order to sense the external parameters applied to the grating area.

A Nondestructive Measurement Method of Optical Fiber Young's Modulus Based on OFDR.

A nondestructive measurement method based on an Optical frequency domain reflectometry (OFDR) was demonstrated to achieve Young's modulus of an optical fiber. Such a method can be used to measure, not only the averaged Young's modulus within the measured fiber length, but also Young's modulus distribution along the optical fiber axis. Moreover, the standard deviation of the measured Young's modulus is calculated to analyze the measurement error.

Distributed high-temperature sensing based on optical frequency domain reflectometry with a standard single-mode fiber.

Distributed temperature sensing up to 600°C at a fiber length of 100.75 m based on optical frequency domain reflectometry (OFDR) was demonstrated using a standard single-mode fiber (SMF) without any treatment. The spatial resolution was 2.

Femtosecond laser auto-positioning direct writing of a multicore fiber Bragg grating array for shape sensing.

A multicore fiber Bragg grating (MC-FBG) array shape sensor is a powerful tool for a variety of applications. However, the efficient fabrication of high-quality MC-FBG arrays remains a problem. Here, we report for the first time, to the best of our knowledge, a new method of directly writing FBG arrays in a seven-core fiber (SCF) through the protective coating using femtosecond laser auto-positioning point-by-point technology, which is accomplished by image recognition and micro-displacement compensation.

Excitation of high order orbital angular momentum modes in ultra-short chiral long period fiber gratings.

A class of ultra-short chiral long period fiber gratings (CLPFGs) are prepared by writing a spiral curve on the surface of a six-mode fiber. The CLPFGs are applied to excite ±2- and ±3-order orbital angular momentum (OAM) modes. The coupling efficiency of the CLPFG in these modes can be as high as 99%, when the length is only 0.

Automated lens design for optical systems consisting of stock lenses.

The design of lens systems requires advanced knowledge and the mastery of highly specialized software tools. Furthermore, for the realization of the designed lens systems often custom-made lenses are needed, which are expensive and have lead times of several weeks compared to stock lenses with several days. To shorten realization time, a new approach for the automated design of lens systems consisting of stock lenses is developed.

Femtosecond laser point-by-point inscription of an ultra-weak fiber Bragg grating array for distributed high-temperature sensing.

Ultra-weak fiber Bragg grating (UWFBG) arrays are key elements for constructing large-scale quasi-distributed sensing networks for structural health monitoring. Conventional methods for creating UWFBG arrays are based on in-line UV exposure during fiber drawing. However, the UV-induced UWFBG arrays cannot withstand a high temperature above 450 °C.

Ultra-dense perfect optical orbital angular momentum multiplexed holography.

Optical orbital angular momentum (OAM) has been recently implemented in holography technologies as an independent degree of freedom for boosting information capacity. However, the holography capacity and fidelity suffer from the limited space-bandwidth product (SBP) and the channel crosstalk, albeit the OAM mode set exploited as multiplexing channels is theoretically unbounded. Here, we propose the ultra-dense perfect OAM holography, in which the OAM modes are discriminated both radially and angularly.