Patent ID: 9553689
Date: 2017-01-24
CPC Classifications: G02B,H04B,H04J

Claim:
1. A temperature-insensitive DEMUX/MUX device for WDM applications comprising: a delay-line interferometer including a first MMI coupler configured to receive a first input light bearing multiple wavelengths and split into two branches of light to respectively transmit through two waveguides with a phase delay, a second MMI coupler configured to combine the two branches of light to form a first output light with an intensity peak position in an exit plane of the second MMI coupler, the exit plane being perpendicular to the first output light at a first distance away from a focus point of the two branches of light; a heater locally attached with one of the two waveguides of the delay-line interferometer; a first free-space coupler with an input plane attached with the exit plane of the second MMI coupler to receive the first output light as a second input light bearing the same multiple wavelengths, one or more optical fibers or waveguides for grating the second input light spatially based on the multiple wavelengths, and a second free space coupler configured to refocus the spatially grated light to form multiple second output lights respectively at multiple output channels each carrying an individual wavelength of the multiple wavelengths; wherein the intensity peak position of the second input light at the exit plane is shifted a second distance within the exit plane away from a perpendicularly projected position of the focus point of the two branches of light, the second distance is tunable by the heater to make each of the second output lights with corresponding individual wavelength being substantially free from any spatial shift off the corresponding output channel at any environmental temperature; wherein the multiple wavelengths comprise a plurality of wavelengths at ITU grids as DWDM channels including at least a first wavelength and a second wavelength respectively for two neighboring channels; wherein the delay-line interferometer comprises a single silicon-on-insulator substrate used for forming the two waveguides; and wherein the heater is configured to change temperature of the one of the two waveguides for tuning the phase delay so to change the second distance within the exit plane for adjusting the intensity peak position of the first output light and subsequently to align the multiple second output lights at multiple output channels respectively.