Abstract

I. INTRODUCTION In wavelength division multiplexing (WDM) networks, tunable lasers are employed as the light sources [1]. For tunable lasers, the requirement for fast wavelength switching is becoming more and more important recently. In the event of an outage in a WDM system, one of the ways for restoration is optical path switching with wavelength conversion, which is in general required to be completed within 100 ms. For fast wavelength switching, a distributed Bragg reflector laser diode (DBR LD) or an external cavity laser diode (ECLD) is often employed [2][3]. However, these LDs tend to suffer from wavelength jumping due to mode-hopping. A distributed feedback laser diode (DFB LD) has high stability and reliability, and is widely employed as a light source in a WDM system. However, its switching speed is relatively low because of the slow response of a thermoelectric cooler (TEC). In the previous works, we proposed and demonstrated fast wavelength switching technology with a DFB LD [4][5]. In this paper, we propose a tunable light source with a DFB LD that provides a wide tuning range as well as fast wavelength switching.

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