Abstract: In a waveguide grating router, a predetermined composite transmission spectrum output is achieved by eliminating loss imbalances through the use of variable loss elements. The variable loss elements are introduced to the waveguide grating router's waveguide ports, such that the loss of a transmitted signal is independent of wavelength. The waveguide grating router includes at least one input waveguide and a plurality of output waveguides. The variable loss element is introduced to a predetermined group of output waveguides to produce a predetermined composite amplitude spectrum of the output signals. To provide a predetermined composite amplitude output spectrum, the variable loss elements may be implemented in a variety of ways, including a method of varying the cross-sectional areas of the router's waveguide ports to introduce more loss.

Abstract: Optical devices, such as wavelength routers, having a plurality of waveguides of differing lengths, with improved independence to temperature fluctuations. Improved temperature independence is achieved by varying the cross-section of the device waveguides. Cross-section variation can be implemented in one or more of the following ways: selectively applying a temperature-compensating material (e.g., a polymer) over portions of the waveguides, and/or varying the dimensions and/or compositions of the materials used in the waveguides, either along each waveguide or between waveguides or both. By carefully designing the devices, the temperature effects resulting from the different lengths of the different waveguides can be compensated to produce a relatively temperature-independent device.

Abstract: A wavelength selective resonant grating exhibits transmission resonances when a single gap between two sections of a split gratings is used to provide a phase shift which is not a quarter wavelength in length or .pi./2 in phase. When the phase is changed to non - .pi./2 values (or the gap differs from a quarter wave), the transmission resonance moves from the center of the stop band. Appropriate adjustments of the phase over a .pi. interval allow tuning of the resonance across the entire stop band. The resonant optical wavelength grating can, illustratively, be used as wavelength filter, wavelength monitor, or as part of an Add/Drop arrangement.

Abstract: Two or more wavelength routers are cascaded together to form a passband filter with low levels of crosstalk between different channels of a wavelength division multiplexing (WDM) stream. Cascading wavelength routers is a technique that can be used to efficiently realize wide and flat passbands, but high levels of cross-talk may result from multi-path interference caused by grating lobes, which produce unwanted transmission paths between the two routers. Spatial filtering can be applied to inhibit the propagation of light-energy along the unwanted paths, and it can be implemented using any suitable techniques including pinholes, reflectors, waveguides, and multi-mode interferometers (MMIs). The resulting passband filter can be designed to generate levels of crosstalk similar to those of conventional passband filters that rely on a single waveguide router.

Abstract: A signal router includes a free space region with input and output sides. A number of input and output waveguide arms extend from the respective input and output sides of the free space region. At least a subset of the input or output waveguide arms are configured such that a signal applied to one of the waveguide arms excites multiple modes of that waveguide arm. Coupling between the multiple modes of the various waveguide arms is used to shape a multi-channel output radiation pattern of the router. The excitation of multiple modes may be provided by configuring a given waveguide arm to include a first portion and a second portion, with the second portion arranged between the first portion and a side of the free space region and having a width which is greater than a width of the first portion. Alternatively, the excitation of multiple modes may be provided by including one or more auxiliary waveguide arms between a given pair of main input or output waveguide arms.