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Optics & Laser Technology

Color image security system using chaos-based cyclic shift and multiple-order discrete fractional cosine transform

Tue, 2013-03-05 17:01 — Guest

September 2013
Publication year: 2013
Source:Optics & Laser Technology, Volume 50

In this paper, a color image encryption algorithm is designed by use of chaos-based cyclic shift and multiple-order discrete fractional cosine transform (MODFrCT). The RGB components of the color image are vertically combined and then simultaneously scrambled by chaos-based cyclic shift to make these three components affect each other. The scrambled RGB components are separately transformed with the MODFrCT, whose orders are determined by the Chirikov standard chaotic map. Based on chaotic inherent properties, the corresponding keys are highly sensitive. At the same time, the transmission of the cipher image is very fast since the DFrCT is a reality preserving transform. Simulation results proved the validity of the proposed algorithm.

Second-order moments of a multi-Gaussian Schell-model beam in a turbulent atmosphere

Tue, 2013-03-05 17:01 — Guest

September 2013
Publication year: 2013
Source:Optics & Laser Technology, Volume 50

The multi-Gaussian Schell-model (MGSM) beam was introduced recently [Opt. Lett. 37, 2970 (2012); J. Opt. Soc. Am. A 29, 2159 (2012)]. In this paper, we derive analytical expressions for the second-order moments of the Wigner distribution function of a MGSM beam in a turbulent atmosphere based on the extended Huygens–Fresnel integral. With the help of the derived formulae, the evolution properties of the propagation factor and the effective radius of curvature of a MGSM beam in a turbulent atmosphere are studied in detail. Our results show that a MGSM beam is affected less by the atmospheric turbulence than a GSM beam, which will be useful in long-distance free-space optical communications.

Closed-form expressions for the optimization of high speed electro-optical modulators

Wed, 2013-02-27 05:55 — Guest

July 2013
Publication year: 2013
Source:Optics & Laser Technology, Volume 49

Compact closed-form mathematical expressions for the propagation parameters (characteristic impedance, effective permittivity and attenuation) of coplanar waveguides (CPW) are presented. The formulas take into account asymmetric structures, thick electrodes and two-layered substrates, and thus are perfectly tailored for the optimization of electro-optical modulators. Excellent agreements, within a range of frequencies up to 100GHz, are found with full-wave finite elements results from commercial software (HFSS) and with measures reported in the literature, for material and geometrical CPW parameters of practical relevance for the design of electro-optical modulators.

The radio-on-fiber-wavelength-division-multiplexed-passive-optical network (WDM-RoF-PON) for wireless and wire layout with linearly-polarized dual-wavelength fiber laser and carrier reusing

Wed, 2013-02-27 05:55 — Guest

July 2013
Publication year: 2013
Source:Optics & Laser Technology, Volume 49

In this paper, we design a WDM-RoF-PON based on linearly-polarized dual-wavelength fiber laser and CSRZ-DPSK, which can achieve wire-line and wireless access synchronously. With the CSRZ-DPSK modulation, the wireless access in ONU can save RF source and the frequency of radio carrier can be controlled by OLT. The dual-wavelength fiber laser is the union light source of WDM-PON with polarization multiplexing. By the RSOA and downstream light source reusing, the ONU can save omit laser source and makes the WDM-PON to be colorless. The networking has the credible transmission property, including wireless access and fiber transmission. The networking also has excellent covering range.

Porphyrin thin films on fiber optic probes through UV-light induced deposition

Wed, 2013-02-27 05:55 — Guest

July 2013
Publication year: 2013
Source:Optics & Laser Technology, Volume 49

The integration of a tetrakis(4-sulfonatophenyl)porphyrin (TPPS) thin film with optical fiber technology is obtained via a non-conventional procedure consisting in a UV-light induced deposition. This leads to the growth of TPPS thin films right at the core region of the fiber end. The simplicity and cost effectiveness of this procedure, as well as the potential of porphyrins as functional materials, enable the design of novel active and passive in-fiber devices. Here, the presence of intense, narrow bands in the reflected spectra is successfully exploited to detect corrosive or toxic vapors, such as strong volatile acids and bases, at room temperature.

Low repetition rate broadband high energy and peak power nanosecond pulsed Yb-doped fiber amplifier

Wed, 2013-02-27 05:55 — Guest

July 2013
Publication year: 2013
Source:Optics & Laser Technology, Volume 49

We demonstrate a broadband fiber amplifier system emitting 10nm pulses with 33mJ pulse energy at repetition rates between 1 and 20Hz. In combination with a pulse width of 10ns, a corresponding peak output power over than 3MW was achieved. This record performance was enabled by fiber with core diameter of 200μm. Furthermore, in order to suppress amplified spontaneous emission (ASE), multi-stage pulse pump technology was applied and different pumping characteristics had been measured. Finally, 15% extraction efficiency was obtained when output energy reached 33mJ. Output capability of the amplifier was not limited by SBS and ASE but the pump peak power.

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