Optical narrow band filter without resonance's

2008

PIER B

Abstract-In this paper, effects of the different apodization and chirp functions in one-dimensional nonlinear Bragg grating on switching characteristics are studied. It is shown that with increasing the Gaussian width in the case of Gaussian apodization, slope of transfer function is increased. The situation is same in the case of raised cosine apodization function too. Also, in the case of quadratic apodization with decreasing the apodization parameter the slope of the transfer function is improved. Using the chirp different functions the switching threshold can be controlled. So, the presented structure as optical switch can be designed for optimum slope and threshold of switching using desired apodization and chirp functions. So, the presented material in this paper shows that there are possibilities for management of all-optical switching using suitable apodization and chirp functions.

Section: Introductionmentioning

confidence: 99%

Analysis and Design of All-Optical Switching in Apodized and Chirped Bragg Gratings

Moghimi¹,

Ghafoorifard²,

2008

PIER B

“…This is the promise of optical switching. Some of the most popular applications of optical switches consist of optical cross-connects [1], optical Add/Drop multiplexing [2], optical signal monitoring [3], optical signal processing tasks [4][5][6]. Many schemes have been suggested for all optical switching, for example by using nonlinear loop mirror [7], nonlinear directional coupler [8], Liquid-crystal optical switches [9,10], Semiconductor Optical Amplifier Switches (SOAs) [1,11] and nonlinear grating [12].…”

Section: Introductionmentioning

confidence: 99%

Multi-Wavelengths Optical Switching and Tunable Filters Using Dynamic Superimposed Photorefractive Bragg Grating

Moghimi¹,

Ghafoorifard²,

2008

PIER C

We present a new scheme for all optical multi-wavelengths switching and filtering using photorefractive materials to route optical signals without converting to electronic state. For this purpose the photorefractive effect which is a nonlinear optical effect seen in certain crystals and other materials that respond to light by altering their refractive index is used. When a photorefractive material is illuminated by patterned command light of intensity I(x), a dynamic superimposed Bragg grating can be obtained which is used for optical multi-wavelength switching and filtering purposes.

“…These functions can be realized with passive components, which there are interesting and currently used for optical signal processing. In optical passive devices the Bragg Gratings is widely used, discussed in literature and applied for optical signal processing tasks [1][2][3]. Usually, these devices can be implemented using Bragg Gratings.…”

Section: Introductionmentioning

confidence: 99%

Linear and Nonlinear Superimposed Bragg Grating: A Novel Proposal for All-Optical Multi-Wavelength Filtering and Switching

Ghafoorifard¹,

Moghimi²,

2007

PIER

Abstract-In this paper, the linear and nonlinear applications including optical filtering and switching of superimposed Bragg grating are presented. For realization of superimposed Bragg grating electrooptic effect is used. The introduced system acts as an optical chip. The induced superimposed index of refractions due to sampled electric potentials applied through metallic strips on electro-optically active core-cladding are investigated analytically and simulated numerically using the Transfer Matrix Method (TMM). It is shown that the applied electric field induces superimposed refractive index grating, which can be controlled using amplitudes and frequency contents of potential samples as well as optical waveguide parameters. Our proposed structure is analog programmable device for realization of many interesting optical signal conditioners such as optical filters, optical beam splitters, and many other special transfer functions in linear case. The proposed device is tunable and can be controlled using the applied potential parameters (samples) and easily satisfy dense wavelength division multiplexing (DWDM) system demand specifications. The electro-optic Pockels effect for generation of the superimposed gratings in this building block will be used. Then we propose an optical chip for performing the introduced functions. In practical cases, for realization of DWDM demands, we need very large number of potential samples approximately 3 to 4 orders of magnitudes. So, this type of block 244 Ghafoori-Fard, Moghimi, and Rostami as optical controllable chip really from practical point of views is impossible and illegal. In this paper, we will present a simple approach for decreasing the number of efficient control samples from outside for managing the proposed tasks. Our calculations in this paper shows that with less than approximately 200 control pins, we can realize all of proposed practical ideas with acceptable precision. Also, with 3 samples per period, our design will cover 215 individual DWDM channels theoretically from 1.55 um towards lower wavelengths and 325 channels for 4 samples per period case, which is infinity from practical point of views. All of transfer functions corresponding to these channels can be manipulated using applied potential samples.Also, as nonlinear applications of the superimposed Bragg grating multi-wavelength optical switching is presented. For this purpose the switching operation is illustrated first and then switching thresholds in the case of three predefined wavelengths are shown. Thus we illustrate numerical results for demonstration of the ability of the proposed structure. At the same time, we investigate effects of the parameters of the proposed structure such as the nonlinear refractive index and the grating length (number of layers) on switching performance including threshold intensity and slope of transition function. The proposed structure can be used as multi-wavelength switching applicable to DWDM and multi wavelength communication systems.