Wavelength conversion by four-wave mixing in a folded-path, self-pumped semiconductor optical amplifier

Abstract

Wavelength conversion is recognized as a key function for the implementation of complex WDM communication systems. Of the approaches demonstrated so far, only four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is fully transparent to modulation format and bit rate while providing arbitrary wavelength mapping. Recent demonstrations have shown that the performance of FWM converters can be made technologically competitive. We present a novel wavelength conversion scheme that offers additional advantages while significantly reducing the complexity of the device. The converter consists of an external-cavity semiconductor laser, with a high-reflection coating on one facet, and a fiber Bragg grating pigtailed to the other facet (anti-reflection coated). The pump wave is provided by the lasing mode at the Bragg frequency (self-pumping). The input signal (with frequency outside the Bragg reflection bandwidth) is modulated with a 2.5-Gbit/s pseudo-random binary sequence of nonreturn to zero amplitude-shift keying data and is injected into the cavity through the Bragg grating via a bi-directional coupler; the converted signal is collected from the other input arm.

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