Abstract: An integrated multi-wavelength transmitter, particularly useful in a wavelength-division multiplexed optical communications system. An arrayed waveguide grating has feedback channels between two coupling regions and is constructed such that, at each coupling region, one port carries all the optical signals of differing wavelengths while a set of other ports carry wavelength-separated signals. The multi-wavelength signal from a first coupling region is reflected from a mirrored surface back into the first coupling region and the arrayed waveguide grating, the mirrored surface thus forming one end of an optical cavity. Similar elements are arranged between corresponding single-wavelength ports of the two regions. The channel from the second coupling region is split into two parts. One part is passed through an optical gain region and is reflected back from the mirrored surface through the power splitter, now acting as a combiner.

Abstract: An optical filter, such as a wavelength-division multiplexer, demultiplexer, or optical router, in which several single-mode waveguides are coupled to the sides of an optical interaction region containing a wavelength dispersive element that collects light from one or more input waveguides inputting light to the interaction region and disperses it according to wavelength to one or more output waveguides outputting wavelength-separated light. According to the invention, a multi-moded waveguide is interposed between one or more of the single-moded waveguides and the optical interaction region. It has a predetermined length to create at one end a multiply peaked image of a singly peaked profile presented to it at the other end, thus being a multi-mode interference (MMI) filter that presents a flatter filter profile at the interface between the MMI and the optical interaction region and affords reduced filter sensitivity to wavelength drift of an optical signal.

Abstract: An integrated, multi-wavelength laser having formed on a substrate (12) a plurality of active, individually selectable waveguides (14), a passive output waveguide (16), and a diffraction grating (18) formed in a Rowland-circle spectrometer geometry. The frequency of the lasing light is determined by-the geometrical relationship of the selected active waveguide, the diffraction grating, and the output waveguide. The active waveguides are positioned such that lasing light cannot diffract between two active waveguides. Little crosstalk occurs because no carrier depletion occurs in the output waveguide.