Influence of the Nonuniform FM Response of DFB Lasers on CPFSK Lightwave Systems with Noncoherent Detection

Abstract

Emerging applications of lightwave technology will utilize wavelength division multiplexing (WDM) to transmit a multiple number of optical signals at distinct wavelengths over an optical fibre, with channel selection at the receiver being performed in the optical domain using either an optical filter or optical frequency discriminator (noncoherent detection). Research in this area is based on the fibre bandwidth being more easily accessed in the wavelength domain than the time domain, and the use of multiwavelength technology to perform network functions such as routing, switching and service segregation. The continuous phase frequency shift keyed (CPFSK) modulation format is attractive for these applications because of the ability to generate CPFSK signals by direct modulation of distributed feedback (DFB) lasers, the tolerance of noncoherent receivers to laser phase noise, and the compact spectrum of the modulated signal allows efficient WDM.