A 42-channel demultiplexer using a volume holographic grating formed in photopolymer medium for dense wavelength division multiplexing (DWDM) applications is experimentally demonstrated for the first time. A 3dB bandwidth of 0.18nm and channel crosstalk of -20dB for a 50GHz channel spacing, is reported.
In this paper, Gaussian apodization technique applied to a transmission volume hologram for holographic demultiplexer is proposed. The Gaussian apodized grating of 15 mm x 11 mmsize, 38 μm thickness and 3.2 mm horizontal standard deviation of the modulating index profile was fabricated. A 22-channel demultiplexer based on that grating has been optically demonstrated. The channel spacing, the interchannel cross-talk level and the channel uniformity of 0.8 nm, -30 dB and 1.5 dB, respectively, were obtained.
Wavelength-selective optical device comprising an optimal phase delay layer (PDL) and two polarization-sensitive gratings has been reported and experimentally demonstrated. In our method, two incident wavelengths have orthogonal polarization states after through PDL and have diffracted by different gratings, independently. From the experimental results, the intensity ratios at 660 nm are 1.171 and 0.0072 for p- and s-polarization, meanwhile, the ratios at 780 nm are 1.980 for s-polarization and 0.084 for p-polarization state, respectively
We has described and demonstrated a new holographic optical tunable filter, which was tuned by the control of the windows in a LCD panel. This method can be a simple and effective way of photorefractive wavelength selective filter.
The independent characteristic of the angular selectivity for the writing conditions was presented in photorefractive grating. In general, the incident angle of writing beam and the interaction length determine the angular selectivity of the grating. When the focused probe beam is incident on the grating, we obtain a new relation that the angular selectivity of the photorefractive grating depends on the probe beam incident conditions and is independent of the writing conditions such as writing beam incident angle, wavelength, and interaction length. These characteristics are experimentally investigated as a function of the following parameters; writing beam incident angle, probe beam width and lens focal length. In the experimental results, it has demonstrated that the control parameters are not the incident angles of writing beam but the probe beam width and focal length of the convex lens. Another property of this configuration is to have same value within large angular range that is also determined by the readout conditions.
A new tuning scheme of the photorefractive filter is presented using LiNbO3 crystal doped with 0.015Wt.% Fe. Analyzing the filter bandwidth property from the geometrical method, a new wavelength selectivity theory is derived. The center wavelength can be tuned by the real-time received beam angle control using the spatial light modulator. As tuning time depends on the response time of the spatia light modulator, it has high tuning speed. The use of thermally fixed single grating makes the uniform diffraction property over all filtering range. Designed tunable filter consists of the three channel with 4 nm bandwidth and 10 nm spacing. From the optical experiment, we get the real-time tunable filter which has 4.5 nm, 4.25 nm, 4 nm bandwidth and 1530.5 nm, 1540.5 nm, 1549.5 nm center wavelength, respectively. Demonstrated filter has a switching time of several tens milli-second and a full tuning range of 20 nm.
In this paper, the implementation of Gaussian apodized volume grating for a demultiplexer is presented. A 42-channel demultiplexer based on that grating is optically demonstrated. By using the Gaussian apodized grating, the crosstalk level between two channels is reduced down to -35dB. The bandwidth of a channel is 0.18 nm. The two adjacent fibers are seperated by 122.5-μm horizontal distance providing the wavelength spacing between each channel of 0.4 nm. Besides, for all 42 channels, the interchannel uniformity of 1.5 dB has been obtained.
A new approach to design the binary phase holograms, which is of less computation time and equal efficiency compared with the genetic algorithm method is proposed. Synthesized holograms having diffraction efficiency of 75.8% and uniformity of 5.8% are proven in computer simulation and experimentally demonstrated.
We propose an experimental demonstration for the phase-only optical decryption based on kinogram encoding. Only one spatial light modulator is used to simultaneously display the encrypted information and the decrypting key for decryption. We investigate the effect of binary and multiphase keys on the security level of the encrypted information. The accepted displacement of the decryption key within the system is also determined. The free misalignment of the Fourier lens is experimentally demonstrated.
A 42 channel demultiplexer for dense wavelength division multiplexing(WDM) using photopoly-mer volumetric diffraction grating that has excellent optical properties and low cost capability, has been designed and optically demonstrated. From the experimental results, we have obtained the 3 dB bandwidth of 0.18 nm, crosstalk suppression of 20 dB and channel uniformity of 1.6 dB for 50 GHB channel spacing.
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