An in-fibre temperature sensor based on a novel dual-mode fibre is proposed and experimentally characterized. The sensor head uses an in-fibre Mach-Zehnder(MZ) structure to sense the surrounding temperature, which depends on the interference spectrums. The concentric multilayer-core fibre (CMCF), in which only two modes could be propagated, would be easier to fabricate an in-fibre MZI with clean spectrum than many fibres, such as multimode fibres, thin-core fibres, PCFs and et al. And low-loss high-strength splice between CMCF and conventional single-mode fibre can be implemented with a commercial fusion splicer. Both the propagation characteristics and operation principle of such a sensor are demonstrated in detail. A sensitivity of ~50.13 pm/°C within temperature range of 30–70 ℃ are experimentally achieved, respectively.
A stable and low costless tunable erbium doped fiber ring laser was proposed and demonstrated. By using the fiber Bragg grating-assisted add-drop filter as a wavelength selector and a wavelength changer at the same time, a stable laser output was obtained with a 4nm tuning range. The power fluctuation, full-width at half maximum and SMSR were measured to be less than 0.50dB, smaller than 0.015nm and better than 55dB in this tuning range.
A novel temperature-insensitive sensor probe is proposed and experimentally characterized. The sensor probe uses an etching cladding Few Mode Fiber Bragg Grating (FM-FBG) to sense the surrounding refractive indexes (SRI), which depends on the reflection peaks. To compensate for the temperature effect in SRI sensing, various guides modes in FM-FBG that have the different sensing behaviors are used for implementation. Both the propagation characteristics and operation principle of such a sensor are demonstrated in detail. A sensitivity of ~2 nm per refractive index unit (RIU) are obtained within the SRI range of 1.333–1.373. This sensor is temperature independent due to the temperature-insensitive nature of wavelength differential Δλ between the two reflection peaks of the etching cladding FM-FBG.
KEYWORDS: Extremely high frequency, Modulation, Radio optics, Single mode fibers, Eye, Fiber Bragg gratings, Modulators, Radio over Fiber, Tunable lasers, Light sources
We propose and demonstrate a radio-over-fiber system to generate an optical millimeter wave (MMW) and realize wavelength reuse for an uplink connection. A tunable optical comb generated by a single Fabry–Perot laser serves as the optical source. The central carrier is separated by an optical circulator cascaded with a fiber Bragg grating. For the downlink, the unmodulated central carrier is coupled with one subcarrier, which has been modulated with 2.5-Gb/s data. Then, different MMWs can be generated by choosing different subcarriers. While for the uplink, the same central carrier is reused for an uplink connection with 1.25-Gb/s data. In the scheme, a 60-GHz MMW is obtained and the bidirectional data are simultaneously transmitted over 60-km transmission with <0.5-dB power penalty. This system shows a simple cost-efficient configuration and good performance over long-distance delivery.
A simple and effective switchable triple-wavelength Er3+-doped fiber laser with narrow-line-width oscillating output is proposed and demonstrated. Only using an arrayed-waveguide grating (AWG) as the comber filter and FBGs as narrow band reflectors of each F-P cavity, a stable simultaneous triple-wavelength oscillation is achieved at room temperature. The output can be switched between single- and triple-wavelength by controlling the LD pump respectively. The side mode suppression ratio and the 3-dB bandwidth of the laser’s outputs are measured to be more than 55dB and less than 10pm. Moreover, the output power stability of the laser has also been measured and analyzed.
The unified coupled-mode formalism derived from Maxwell's equation is employed to analyze the add/drop filters using
a Bragg grating assisted mismatched coupler. An add/drop filter using a Bragg grating-assisted mismatched coupler is
fabricated and tested. The maximum reflectivity, 3dB bandwidth, insert loss at the drop port and reflective loss at the
input port of the filter are measured to be about 12 dB, 0.2 nm, 3.91 dB and - 7.39 dB, respectively.
The unified coupled-mode formalism derived from Maxwell's equation is employed to analyze the add/drop filters using
a Bragg grating assisted mismatched coupler. By writing a linearly chirped Bragg grating over the uniform coupling
region of the coupler, a filter with maximum reflectivity and 3dB bandwidth at the drop port about 20 dB and 0.8 nm,
respectively, is obtained. The experimentally measured results are in good agreement with the numerical calculations. A
broadband add/drop filter using a Bragg grating-assisted mismatched coupler can be obtained by writing a linearly
chirped Bragg grating over the uniform coupling region of the coupler.
Double-grating coupler based on two fiber Bragg gratings(FBGs) has the advantages of compact structure and enhanced
filtering efficiency. The influences of different gratings' position in the coupling region and grating length on the
filtering spectra were investigated based on the unified coupled-mode theory. The results show that, the coupling region
on the left of the graing mostly affects the drop channel characteristic;the length of the grating mostly affects the drop
efficiency;the transmission characteristic is best with the whole length of the coupling region Lc integral multiple of
coupling lengthπ /(2Kf ) .A coupler with uniform coupling region making of two photoconductive fibers was fabricated
by improved fused taper technology,then two Bragg gratings were written in the coupling region with 248nm ultraviolet
laser, and a grating reflecton coupler with maximum drop reflectivity 20dB and bandwidth 0.8nm was achieved.
The growth of long period fiber grating written in H2-loaded fiber within one hour immediately after fabrication was
measured and analyzed. Fast deepen on difference of refraction index was obviously observed in all the experiments,
but the peak wavelength to time and cross-coupling coefficient to time curves are fitted better in exponential decay
function than power function, and suggest a same variation pattern in difference of refraction index.
KEYWORDS: Signal processing, Wavelets, Digital filtering, Filtering (signal processing), Electronic filtering, Digital signal processing, Linear filtering, Silicon, Lithium, Electrical engineering
Anti-jamming techniques were studied in dynamic stress test on bogie structure form the hardware and software. The paper sums up the hardware techniques like compound protection technique and anti-radiation jamming technique; and mainly introduces the software techniques such as zero drift signal processing, digital signal filtering processing, and wavelet signal processing. Additionally, an algorithm 'three-peak-valley stress value compare' is proposed in the wavelet signal processing. The results in application prove these measurements help to provide valid and reliable stress-time history signals for programming the bogie stress spectrum.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.