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Hybrid technique based on chirp effect and phase shifts for spectral Talbot effect in sampled fiber Bragg gratings (FBGs)

100%

Deng G. , Pan W.

Optica Applicata

2011

tom Vol. 41, nr 1

225--233

To implement the spectral Talbot effect in sampled fiber Bragg gratings (SFBGs), a hybrid technique based on a chirp effect and phase shifts is proposed. Firstly, the general phase condition is derived as the principle of this hybrid technique, and it also can be used to demonstrate other reported techniques, including the linear chirp, the periodical chirp, and the multiple phase shift technique. According to the general phase condition and the equivalent chirp coefficient in the Talbot effect, multi-channel dispersion compensators are designed with different arrangements of chirp coefficient and phase shifts. Moreover, the dispersion value can be tuned in these devices by dynamically adjusting the phase shifts of the hybrid technique. Numerical simulations are carried out to confirm the performance of such devices realized by using the hybrid technique.

Amplifier Noise Based Optical Steganography with Coherent Detection

100%

Wu B. , Chang M. P. , Caldwell N. R. , Caldwell M. E. , Prucnal P. R.

Coherent Phenomena

2014

tom 2

nr 1

We summarize the principle and experimental setup of optical steganography based on amplified spontaneous emission (ASE) noise. Using ASE noise as the signal carrier, optical steganography effectively hides a stealth channel in both the time domain and the frequency domain. Coherent detection is used at the receiver of the stealth channel. Because ASE noise has short coherence length and random phase, it only interferes with itself within a very short range. Coherent detection requires the stealth transmitter and stealth receiver to precisely match the optical delay,which generates a large key space for the stealth channel. Several methods to further improve optical steganography, signal to noise ratio, compatibility with the public channel, and applications of the stealth channel are also summarized in this review paper.

Package for fiber Bragg gratings (FBG) and a comparative study on their polarization mode dispersion (PMD) at varying temperature

88%

Ning T. , Pei L. , Liu Y. , Tan Z. , Wang Q. , Zheng J. , Jian S.

Optica Applicata

2005

tom Vol. 35, nr 2

277-282

A temperature-compensated material of fiber Bragg grating (FBG), which has negative thermal -expansion coefficient has been presented. The temperature coefficient of FBGs' center wavelength is less than 0.0005 nm/°C after three-layer-structure temperature-compensated package under tension. For the first time, PMD of FBG with and without temperature compensation has been detailedly studied and measured from -20 to 60°C. The measured result shows that the PMD changes a little at varying temperature, which means that the package did not affect the PMD characteristic of FBG.