Fiber Bragg grating has embraced the area of fiber optics since the early days of its discovery, and most fiber optic sensor systems today make use of fiber Bragg grating technology Researchers have gained enormous attention in the field of fiber Bragg grating (FBG)-based sensing due to its inherent advantages, such as small size, fast response, distributed sensing, and immunity to the electromagnetic field Fiber Bragg grating technology is popularly used in measurements of various physical parameters, such as pressure, temperature, and strain for civil engineering, industrial engineering, military, maritime, and aerospace applications Nowadays, strong emphasis is given to structure health monitoring of various engineering and civil structures, which can be easily achieved with FBG-based sensors Depending on the type of grating, FBG can be uniform, long, chirped, tilted or phase shifted having periodic perturbation of refractive index inside core of the optical fiber Basic fundamentals of FBG and recent progress of fiber Bragg grating-based sensors used in various applications for temperature, pressure, liquid level, strain, and refractive index sensing have been reviewed A major problem of temperature cross sensitivity that occurs in FBG-based sensing requires temperature compensation technique that has also been discussed in this paper

https://www.spiedigitallibrary.org/journals/optical-engineering/volume-59/issue-6/060901/Fiber-Bragg-grating-sensors-for-monitoring-of-physical-parameters/10.1117/1.OE.59.6.060901.pdf

Fiber Bragg grating sensors for monitoring of physical parameters: a comprehensive review

Continuous-wave silica-based erbium-doped fibre lasers

A multiwavelength fiber ring laser obtained by use of a semiconductor optical amplifier (SOA) with a simple laser cavity configuration is reported. A Fabry-Perot filter was used in the fiber laser ring cavity to achieve more than 50 simultaneous wavelength lasing oscillations with a frequency separation of 50 GHz. The resulting stable broadband multiwavelength lasing operation was attributed to broadband and flat gain of the SOA, which has a gain flatness of 0.8 dB for more than 20 nm. The laser has a total output power of -3 dBm and a signal-to-spontaneous-noise ratio of 30 dB.

Multiwavelength fiber ring lasing by use of a semiconductor optical amplifier

By controlling the output coupling ratio, we demonstrate a novel wavelength-tunable L-band Erbium-doped fiber laser (EDFL) with a maximum tuning range up to 58 nm (from 1567 to 1625 nm) by controlling its output coupling ratio between 1% and 99%. The L-band EDFL is configured by using a bi-directionally dual-wavelength pumped EDFA in close-loop with an output coupler of tunable coupling ratio and an air-gap inserted FC/PC connector pair. Such an EDFL exhibits a quantum efficiency of 42% and an ultra-high power conversion efficiency of 37% under optimized pumping scheme, providing the small-signal gain and output power of ~34 dB and 91 mW, respectively. Low variation of <1.2 dB on channel power, power fluctuation of 0.04% and a narrow linewidth of 0.03 nm are obtained.

https://ir.nctu.edu.tw:443/bitstream/11536/11673/1/000241517400022.pdf

L-band Erbium-doped fiber laser with coupling-ratio controlled wavelength tunability

Switchable multi-wavelength fiber ring laser with an in-fiber Mach-Zehnder interferometer incorporated into the ring cavity serving as wavelength-selective filter at room temperature is demonstrated. The filter is formed by splicing a section of few-mode photonic crystal fiber (PCF) and two segments of single mode fiber (SMF) with the air-holes on the both sides of PCF intentionally collapsed in the vicinity of the splices. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-, dual- and triple-wavelength lasing operations by exploiting polarization hole burning (PHB) effect.

Switchable multi-wavelength fiber ring laser based on a compact in-fiber Mach-Zehnder interferometer with photonic crystal fiber

Efficient multi-wavelength fiber laser operating in L-band

We report a dual-wavelength actively mode-locked erbium doped fiber laser constructed using one amplitude modulator as mode locker, two fiber Bragg gratings (FBGs) as wavelength filters and two separate parts of gain mediums in order to minimize gain cross-saturation effects. Dual-wavelength pulses with a wavelength spacing of 0.8nm, 1.6nm, 2.4nm and 3.2nm were simultaneously obtained when the modulation frequency was about 2.5GHz in the experiment, respectively. By adjusting the cavity length of one wavelength with a delay line, the repetition rate of this channel can be changed to as two times as the other channel without changing the modulation frequency.

Dual-wavelength actively mode-locked erbium-doped fiber laser using FBGs

We introduce a novel electric current sensor, which is based on a fiber Bragg grating covered by a uniform coat of aluminium thin film which was deposited on the FBG by a simple evaporation method. The Bragg wavelength of thefiber grating shifts when the current flowing through the film varies due to the Joule heat generated by the current. Therelationship between the square of the current intensity and the wavelength shift is basically linear. In the experiment,the maximum current can be measured was 43 . imA with the wavelength shift of about 4nm and the current sensitivitywas about 2.31 X iO nm/(mA)2.Key words: fiber Bragg grating, electric current, thin film 1. INTRODUCTION In recent years, fiber Bragg grating (FBG) sensors havc attracted considerable interest because they are capable ofmeasuring a wide range of parameters and have a number of distinguishing features, such as immunity from electromagnetic interference, suitability for remote measurement, small size, and high resolution 1,2

Electric current measurement with high resolution using FBG covered by aluminium thin film

We introduce a novel simple current sensor, which is based on a fiber Bragg grating covered by a uniform coat of aluminum thin film. The Bragg wavelength of the fiber grating will shift when the current flowing through the film varies due to the Joule heat generated by the current. The relationship between the square of the current intensity and the wavelength shift is basically linear. In the experiment, we got a current sensitivity of about 2.31x10 MIN3 nm(mA) 2 .

Electric current measurement using fiber Bragg grating covered by aluminum thin film

A novel method, which utilizes amplified spontaneous emission (ASE) as a secondary pump source, is presented for implanting a linear cavity erbium-doped fiber laser operating in L-Band. The output wavelength tuned from 1583nm to 1600nm, about 17nm tuning range, was obtained in the experiment and the stability of the laser is very good.

Shiquan Yang

Papers

Efficient multi-wavelength fiber laser operating in L-band

Dual-wavelength actively mode-locked erbium-doped fiber laser using FBGs

Electric current measurement with high resolution using FBG covered by aluminium thin film

Electric current measurement using fiber Bragg grating covered by aluminum thin film

Wavelength tunable linear cavity Er-doped fiber laser operating in L-band