Process variation-tolerant cascaded tapered optical ring resonators

A wavelength division multiplexing (WMD) optical system comprising:

• cascaded ring resonators configured to selectively filter different wavelengths of optical signals received from an optical channel, each of the cascaded ring resonators including:
• a first ring having a varying waveguide width along its length configured to form a first waveguide width portion and a second waveguide width portion, the first waveguide width portion having a greater width than the second waveguide width portion;
• and
• a second ring having a varying waveguide width along its length configured to form a third waveguide width portion and a fourth waveguide width portion, the fourth waveguide width portion having a greater width than the third waveguide width portion;
• wherein the second waveguide width portion of the first ring and the third waveguide width portion of the second ring are positioned to face one another to form a first coupling region in which both first and second rings have narrowed waveguide widths;
• and
• receivers configured to be connected to respective cascaded ring resonators, each of the receivers having a photodetector configured to differentiate between the optical signals.

A method comprising:

• selectively filtering different wavelengths of optical signals received from an optical channel using cascaded ring resonators, each of the cascaded ring resonators including:
• a first ring having a varying waveguide width along its length configured to form a first waveguide width portion and a second waveguide width portion, the first waveguide width portion having a greater width than the second waveguide width portion;
• and
• a second ring having a varying waveguide width along its length configured to form a third waveguide width portion and a fourth waveguide width portion, the fourth waveguide width portion having a greater width than the third waveguide width portion;
• wherein the second waveguide width portion of the first ring and the third waveguide width portion of the second ring are positioned to face one another to form a first coupling region in which both first and second rings have narrowed waveguide widths;
• and
• connecting receivers to respective cascaded ring resonators, each of the receivers having a photodetector configured to differentiate between the optical signals.