Abstract

1. Introduction There are two main categories of needed WDM sources: those that output one wavelength at a time onto which data is usually externally modulated; and those that output several wavelengths simultaneously, onto each of which data is usually directly modulated. The first category is generally employed for long transmission distances because of the low chirp, while the second category is generally employed for medium and short transmission distances because of the low cost per wavelength. Here we present an ideal source for the second category. Early sources for the second category consisted of a collection of discrete fiber-coupled distributed feedback (DFB) lasers, one for each wavelength¹¹¹. More recently, to be more cost- effective, arrays of DFB lasers have been integrated with star couplers onto single chips^[2,31. However, DFB arrays do not have an intrinsically controlled channel spacing, and the combing loss in the star coupler increases linearly with channel number. To insure the channel spacing accuracy necessary for WDM networks, it is advantageous to have all the channels in the source locked to the same filter element. The first semiconductor laser operating on this principle was the Multistripe Array Grating Integrated Cavity (MAGIC) laser[4] based on a reflective grating. Since then, significant progress has been achieved on a semiconductor laser based on a transmissive grating, the waveguide grating router multiffequency laser (MFL)^[51. Here, we present the MFL's recent results.

© 1997 Optical Society of America