No abstract

No abstract

No abstract

In this paper, theory and experimental results for wavelength-division-multiplexing (WDM) channel generation, formed by multi-line optical injection locking, is presented. A small-signal model to deal with wide-spectral-band optical injection problems has been developed. Based on this model, the crosstalk noise of an injection-locked laser in a coherent WDM system is assessed analytically. Experimental results on locking range, stability, and crosstalk noise confirms the modeling results, which indicate that stable and low-noise channels can be generated by this approach. Index Terms-Optical injection locking, optical transmitters, wavelength-division multiplexing (WDM). I. INTRODUCTION M OST current commercial dense wavelength-division multiplex (DWDM) systems operate with 2.5-or 10-Gb/s channel capacity. Due to a number of optical fiber and optical device impairments, the narrowest channel spacing used is currently 50 GHz. These figures lead to commercial spectral efficiencies limited to 0.2 b/s/Hz. One option to increase spectral efficiency is to increase the individual channel capacity to 40 Gb/s. The technology involves utilization of high-complexity components, with technological and physical impairments regarding group velocity and polarization mode dispersion in fiber, leading to limitations on the achievable transmission distance [1]. Another option is to reduce channel spacing. Apart from nonlinear interactions between the modulated optical carriers and the fiber-optic transmission medium, limitations here arise also from DWDM components. When reducing channel spacing to 25 GHz or less in a 10-Gb/s system, strict tolerances for center wavelength drift of components and lasers over operating temperature, aging, and measurement uncertainties apply.