Wavelength locking filter

Patent metadata

Field	Value
Publication number	US-2016282640-A1
Application number	US-201615079590-A
Country	US
Kind code	A1
Filing date	Mar 24, 2016
Priority date	Mar 25, 2015
Publication date	Sep 29, 2016
Grant date	—

Abstract

An optical system can automatically lock an adjustable spectral filter to a first wavelength of an incoming light signal, and can automatically filter an additional incoming light signal at the first wavelength. A tunable filter can have a filtering spectrum with an adjustable peak wavelength and increasing attenuation at wavelengths away from the adjustable peak wavelength. The tunable filter can receive first input light, having a first wavelength, and can spectrally filter the first input light to form first output light. A detector can detect at least a fraction of the first output light. Circuitry coupled to the detector and the tunable filter can tune the tunable filter to maximize a signal from the detector and thereby adjust the peak wavelength to match the first wavelength. The tunable filter further can receive second input light and spectrally filter the second input light at the first wavelength.

First claim

What is claimed is:

1 . An optical system, comprising:
a tunable filter having a filtering spectrum with an adjustable peak wavelength and increasing attenuation at wavelengths away from the adjustable peak wavelength, the tunable filter configured to receive first input light, having a first wavelength, and spectrally filter the first input light to form first output light; a detector configured to detect at least a fraction of the first output light; and circuitry coupled to the detector and the tunable filter, the circuitry being configured to tune the tunable filter to maximize a signal from the detector and adjust the peak wavelength to match the first wavelength, the tunable filter further configured to receive second input light and spectrally filter the second input light to form second output light, the second output light being spectrally filtered with a peak at the first wavelength and increasing attenuation at wavelengths away from the first wavelength.

2 . The optical system of claim 1 , wherein the tunable filter comprises:
an optical ring resonator formed from at least one waveguide arranged in a closed path.

3 . The optical system of claim 2 , wherein the optical ring resonator is configured to propagate light in a first direction around the closed path and a second direction, opposite the first direction, around the closed path.

4 . The optical system of claim 3 , further comprising:
a first input waveguide configured to inject the first input light, having a first wavelength, into the optical ring resonator in the first direction; a first output waveguide configured to extract the first output light from the optical ring resonator in the first direction;

5 . The optical system of claim 4 , further comprising:
a second input waveguide configured to inject the second input light into the optical ring resonator in the second direction; a second output waveguide configured to extract the second output light from the optical ring resonator in the second direction.

6 . The optical system of claim 5 , wherein the tunable filter further comprises:
a material having a temperature-dependent refractive index disposed in an optical path of the optical ring resonator; and a heater configured to controllably heat at least a portion of the material, and thereby change an optical path length around the optical ring resonator and thereby change a resonant wavelength of the optical ring resonator, wherein the circuitry is further configured to tune the tunable filter by heating the portion of the material.

7 . The optical system of claim 5 , wherein the tunable filter further comprises:
a material having a current-dependent refractive index via free-carrier absorption disposed in an optical path of the optical ring resonator; and a forward-biased PIN diode configured to controllably inject current into at least a portion of the material, and thereby change an optical path length around the optical ring resonator and thereby change a resonant wavelength of the optical ring resonator, wherein the circuitry is further configured to tune the tunable filter by injecting the current into the portion of the material.

8 . The optical system of claim 5 , wherein a top silicon layer of a silicon-on-insulator wafer is shaped to define the optical ring resonator, the first and second input waveguides, and the first and second output waveguides.

9 . The optical system of claim 2 , wherein the optical ring resonator has a free spectral range greater than a specified range of wavelengths for the first input light.

10 . The optical system of claim 1 , wherein the tunable filter comprises:
a plurality of optical ring resonators, each of the plurality of optical ring resonators being formed from at least one waveguide arranged in a respective closed path.

11 . The optical system of claim 1 , wherein the tunable filter is further configured to receive third input light and spectrally filter the third input light to form third output light, the third output light being spectrally filtered with a peak at the first wavelength and increasing attenuation at wavelengths away from the first wavelength.

12 . The optical system of claim 1 , further comprising:
a first input multiplexer configured to multiplex a plurality of inputs into the first input; and a first output demultiplexer configured to demultiplex a plurality of outputs from the first output light.

13 . The optical system of claim 1 , further comprising:
a second input multiplexer configured to multiplex a plurality of inputs into the second input light; and a second output demultiplexer configured to demultiplex a plurality of outputs from the second output light.

14 . The optical system of claim 1 , further comprising:
a tunable optical source configured to produce the second input light; a second detector configured to detect at least a fraction of the second output light; and wavelength-tuning circuitry coupled to the second detector and the tunable optical source, the wavelength-tuning circuitry being configured to tune the tunable optical source to maximize a signal from the second detector and adjust a wavelength of the second input light to match the peak wavelength and thereby match the first wavelength.

15 . A method, comprising:
receiving first input light, having a first wavelength, at a tunable filter, the tunable filter having a filtering spectrum with an adjustable peak wavelength and increasing attenuation at wavelengths away from the adjustable peak wavelength; spectrally filtering the first input light with the tunable filter to form first output light; detecting a fraction of the first output light; tuning the tunable filter to maximize the detected fraction of the first output light, thereby adjusting the peak wavelength to match the first wavelength; receiving second input light at the tunable filter; and spectrally filtering the second input light to form second output light, the second output light being spectrally filtered with a peak at the first wavelength and increasing attenuation at wavelengths away from the first wavelength.

16 . The method of claim 15 , wherein tuning the tunable filter to maximize the detected fraction of the first output light comprises:
heating at least a portion of a material having a temperature-dependent refractive index and positioned in an optical path of an optical ring resonator.

17 . The method of claim 15 , wherein tuning the tunable filter to maximize the detected fraction of the first output light comprises:
injecting carrier current into at least a portion of a material having a current-dependent refractive index and positioned in an optical path of an optical ring resonator.

18 . The method of claim 15 , further comprising:
multiplexing a plurality of inputs into the first input light; demultiplexing a plurality of outputs from the first output light; multiplexing a plurality of inputs into the second input light; and demultiplexing a plurality of outputs from the second output light.

19 . The method of claim 15 , further comprising:
producing the second input light with a tunable optical source; detecting a fraction of the second output light; tuning the tunable optical source to maximize the detected fraction of the second output light, thereby adjusting a wavelength of the second input light to match the first wavelength.

20 . An optical system, comprising:
an optical ring resonator formed from at least one wavegui

Assignees

• Aurrion Inc

Inventors

• Guzzon Robert Silvio

Classifications

• G02F1/025 Primary

  in an optical waveguide structure (G02F1/017, {G02F1/2257} take precedence) · CPC title

• G02F1/0121

  Operation of devices; Circuit arrangements, not otherwise provided for in this subclass · CPC title

• G02B6/29341

  Loop resonators operating in a whispering gallery mode evanescently coupled to a light guide, e.g. sphere or disk or cylinder (evanescent coupling for sensing fluorescence G01N21/648) · CPC title

• G02F1/0147

  based on thermo-optic effects (G02F1/132 takes precedence) · CPC title

• G02B6/29383

  Adding and dropping · CPC title