Abstract

The need for reconfigurability in optical networks and the desire to simplify inventories of fixed wavelength lasers has created a substantial need for a low cost and reliable tunable laser. Ideally, this laser should have the same performance and similar cost to that of a conventional DFB, but also be tunable over the entire communication band. To date, there have been numerous approaches to address this need, from sampled grating DBRs¹ to external cavity with MEMS² to array based approaches.^3,4 Each technology has strengths and weaknesses, making each particularly suited to a different set of requirements. The advantages of DFB array based methods include the immunity to mode hops, proven long term reliability, and widely accepted spectral characteristics. Generally, the larger the number of elements and the closer the spacing, the easier the fiber coupling and the less the real-estate and potentially the cost. Recently, arrays of 4 lasers with at a 10 micron pitch were described by NEC that could cover 8 nm with 2 nm temperature tuning per laser.³ In this paper we describe a 12 element multi-wavelength array chip at the same 10 micron pitch with a 2.7 nm wavelength tuning per element that can span the 32 nm wide c-band, once again using laser selection for coarse tuning and temperature for fine tuning. The chip is designed to be low cost and high yield, requiring a small real-estate (0.5 mm × 1 mm) and uses a robust quarter-wave shifted structure with nearly unity wavelength yield. The processing is similar to that of fixed wavelength DFBs. The chip has been packaged into a module with a low loss external combiner and electronic control to deliver high optical power tunable over the c-band.

© 2002 Optical Society of America