Theoretical analysis of pattern effect suppression in semiconductor optical amplifier utilizing optical delay interferometer

The ability of an optical delay interferometer (ODI) to suppress the pattern effect that is inherently present in a straightforward, solitary semiconductor optical amplifier (SOA) whose dynamic response is slower than the period of its driving high-speed return-to-zero (RZ) data signal is theoretically investigated. For this purpose an existing comprehensive model that simulates and links the operation of these two elements is methodically applied to their concatenated configuration. In this manner an extensive set of curves is numerically obtained, which allow to analyze and assess the impact of the input pulse energy and width as well as of the SOA carrier lifetime, line-width enhancement factor and small signal gain on the amplitude modulation of the transmitted sequence at the output of each one of these block units. Their thorough study and interpretation reveals that the employment of the ODI can significantly reduce the value of this quality metric resulting from a single SOA only. The main offered benefit, however, is that any technical restrictions regarding the involved critical parameters can be considerably relaxed while at the same time their useful operational range can be extended. These important findings highlight the necessity of placing this passive device after the SOA and exploiting it in order to effectively alleviate the detrimental pattern-dependent degradation, This fact in conjunction with its overall practicality renders it a promising candidate for enhancing, within the frame of the proposed scheme, the performance of SOAs that are employed as pure amplification elements in fiber-optic communication systems and networking applications. (C) 2008 Elsevier B.V. All rights reserved.