Multiport tunable optical filters
A tunable multiport optical filter includes various types of arrays of optical ports. The tunable filter also includes a light dispersion element (e.g., a grating) and a reflective beam steering element (e.g., a tilting mirror). An optical signal exits an optical (input) port, is dispersed by the light dispersion element, reflects off the reflective beam steering element back to the light dispersion element, and on to another optical (output) port. The reflective beam steering element can be steered such that a wavelength portion of the dispersed optical signal can be coupled to the optical output port. For example, the input optical signal may be a wavelength division multiplexed signal carrying multiple channels on different wavelengths, and the tunable multiport optical filter directs one of the channels to the output optical port. Additionally, the tunable filter may be incorporated into a device act as a wavelength reference.
1. A tunable multiport optical filter comprising:
a linear array of optical ports extending along an x-direction, with adjacent optical ports separated by an integral number of pitches along the x-direction;
an optical output port positioned collinearly with the optical ports and separated therefrom by a non-integer number of pitches;
a light dispersion element positioned to receive an optical signal from one of the linear array of optical ports and to disperse the received optical signal along a y-direction that is not parallel to the x-direction, the received optical signal dispersed into a plurality of separate wavelength components; and
a reflective beam steering element positioned to receive the plurality of separate wavelength components dispersed by the light dispersion element and to reflect the dispersed optical signal back through the light dispersion element, the reflective beam steering element controllable such that any one wavelength component of the dispersed optical signal from any optical port of the linear array of optical ports can be redirected through the light dispersion element to couple to the optical output port.
2. The tunable multipart optical filter of claim 1 , wherein the linear array of optical ports is disposed in a symmetric arrangement with respect to the optical output port, a first portion of the linear array disposed above the optical output port and a second portion of the linear array disposed below the optical output port.
3. The tunable multiport optical filter of claim 1 , wherein the optical output port is positioned along the x-direction beyond the linear array of optical ports.
4. The tunable multiport optical filter of claim 1 , wherein the reflective beam steering element is further controllable to optically couple ones of the linear array of optical ports to others of said linear array of optical ports.
5. The tunable multiport optical filter of claim 1 , wherein the optical signal is a wavelength-division multiplexed signal containing multiple channels at different wavelengths, and the reflective beam steering element is controllable such that any channel of the dispersed optical signal can be redirected through the light dispersion element to couple to the optical output port.
6. The tunable multiport optical filter of claim 5 , further comprising:
a photodetector and analog to digital converter coupled to the optical output port and configured to convert the received optical signal to a digital electrical signal; and
a signal processor configured to apply a deconvolution process to the digital electrical signal to generate enhanced signal resolution of each individual channel in the received wavelength-division multiplexed optical signal.
7. The tunable multiport optical filter of claim 5 , wherein the wavelength-division multiplexed signal complies with an ITU grid.