The proposed scheme was successful to design and verify optical AND gate based on the cascade of Electro Absorption Modulator and Four Wave Mixing effects in a nonlinear fiber. The logical bit sequences were carried by 1550 nm pump laser at 0.3 mW. The gate was designed with 0.01km optical fiber. The scheme was able to analyze the optical logic states for different combinations in terms of narrow and wideband pulses respectively logic ‘0’ and logic ‘1’. Also the generated logic states represented it in terms of power which exceeds or below the threshold power level.

Analysis of All- Optical AND Logic Gate Based on the Cascade of Electro Absorption Modulator and Highly Nonlinear Fibe

An InGaAs-InAlAs multiple-quantum-well (MQW) electroabsorption (EA) waveguide modulator fabricated on a GaAs substrate has been designed and characterized at 1.3- m wavelength for microwave signal transmission on an analog fiber- optic link. The modulator structure with a lattice constant 2.5% larger than that of GaAs is grown upon a 0.7- m-thick three- stage compositionally step-graded In Al As relaxed buffer. The waveguide modulator exhibits a high-electrooptic slope effi- ciency of 0.56 V , a 3-dB electrical bandwidth of 20 GHz, and a large optical saturation intensity in excess of 17 mW. These high- speed optoelectronic modulators could potentially be integrated with on-chip GaAs electronic driver circuits. HE 1.3- m spectral window is desirable for fiber-optic communications because the standard single-mode sil- ica optical fiber exhibits a low-loss chromatic dispersion minimum at wavelengths between 1301 and 1321 nm. Op- toelectronic devices operating at 1.3 m can take advantage of not only the second-generation fiber-optic telecommunica- tion networks deployed but also the commercially available high-power, low-RIN-noise solid-state lasers. The latter is important for analog fiber-optic links since the optical carrier power directly determines the RF link gain, noise figure, and spurious-free dynamic range. Optoelectronic devices on GaAs substrates offer the potential for monolithic integration with GaAs MMIC's. Implementation of 1.3- m vertical-cavity electroabsorption (EA) modulators on GaAs substrates has been demonstrated by growing the InGaAs multiple-quantum wells (MQW's) on top of a thick buffer (2.3 4.6 m) in which the composition is linearly-graded (1)-(3). Recently, we have reported that a novel step-graded InAlAs strain-relief buffer as thin as only 0.3 m can also effectively confine the misfit dislocations for subsequent growth of high-quality 1.3- m MQW's (4). The simple structure has been modi- fied to incorporate quaternary InGaAlAs waveguide layers to implement a high-speed GaAs-based electroabsorption wave- guide modulator. This letter describes the performance of the waveguide modulator for analog fiber-optic link applications. The schematic of the p-i(MQW)-n ridge waveguide modu- lator structure on an n GaAs substrate is illustrated in Fig. 1.

http://ieeexplore.ieee.org/iel3/68/13461/00618487.pdf

W. S. C. Chang

Papers

Electroabsorption Waveguide Modulators