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 acting as a wavelength reference.
1. A tunable multiport optical filter comprising:
a two-dimensional array of optical ports, including both optical input ports and corresponding optical output ports, the two-dimensional array extending along both an x-direction and a y-direction that is not parallel to the x-direction;
a light dispersion element positioned to receive optical signals from the optical input ports and to disperse the optical signals along the y-direction, each received optical signal dispersed into a plurality of separate wavelength components; and
a reflective beam steering element positioned to receive the multiple pluralities of separate wavelengths components dispersed by the light dispersion element and to reflect the dispersed optical signal back to the light dispersion element, the reflective beam steering element controllable for redirecting any selected wavelength components of the dispersed optical signals through the light dispersion element to couple to the corresponding optical output ports without significant coupling to other optical ports.
2. The tunable multiport optical filter of claim 1 , wherein the two-dimensional array of optical ports comprises at least two one-dimensional subarrays of optical ports, each of the two one-dimensional subarrays extending along the x-direction and characterized by a pitch, wherein the two one-dimensional subarrays are offset in the x-direction by a fraction of the pitch.
3. The tunable multiport optical filter of claim 2 , wherein there are two one-dimensional subarrays and the two subarrays are offset in the x-direction by one-half of the pitch.
4. The tunable multiport optical filter of claim 2 , wherein there are 2m one-dimensional subarrays with m being an integer≧1, and the subarrays are offset in the x-direction by (1/2m) times the pitch.
5. The tunable multiport optical filter of claim 1 , wherein the two-dimensional array of optical ports is symmetric about an (x,y) origin, and optical ports location at (x,y) and (−x, −y) form pairs of an optical input port and a corresponding optical output port.
6. The tunable multiport optical filter of claim 1 , wherein the optical signal is a wavelength-division multiplexed signal containing multiple channels at different wavelength components, and the reflective beam steering element is controllable for redirecting any selected channel of the dispersed optical signal through the light dispersion element for coupling to the optical output port.
7. The tunable multiport filter of claim 6 , wherein the wavelength-division multiplexed signal complies with an ITU grid.