Telecommunications optical processor
A demultiplexer for use in a wavelength-division multiplexed optical system including a first positive lens group, a negative lens group, and a second positive lens group in order from a dispersive element and a reflective element. In some embodiments the reflective element is a light modulator, such as an actuatable diffraction grating. In some embodiments the demultiplexer is a part of a dynamic channel equalizer. In embodiments having a light modulator, the modulation may occur during both a first pass and a second pass.
1. A double-pass optical processor to process a plurality of optical carriers of a WDM signal, comprising:
a dispersive optical element to angularly separate the plurality of optical carriers;
a lens system optically coupled to the dispersive element to receive the plurality of optical carriers from the dispersive element;
a modulator optically coupled to the lens system having a reflective surface with a normal, to process the plurality of optical carriers, and configured and arranged such that the plurality of optical carriers are projected onto the reflective surface by the lens system other than along the normal; and
a reflector configured to receive the plurality of optical carriers from the modulator and to reflect the plurality of optical carrier back onto the reflective surface, whereby the processor is configured such that the plurality of optical carriers are is processed by the modulator during both a first pass and a second pass onto the reflective surface.
2. The double-pass optical processor of claim 1 , wherein the reflective surface is configured and arranged such that the plurality of optical carriers are projected at a 45-degree angle to the normal of the reflective surface.
3. The double-pass optical processor of claim 1 , wherein the lens system is comprised of, in order from the dispersive element, a first positive lens group, a negative lens group, and a second positive lens group.
4. The double-pass optical processor of claim 1 , wherein the modulator is electrostatically-actuatable, diffractive device.
5. The double-pass optical processor of claim 1 , wherein the reflector is comprised of a spherical reflective surface.
6. The double-pass optical processor of claim 1 , wherein the reflector is comprised of a plurality of planar, reflective elements, each reflective element being arranged to reflect a corresponding at least one of the plurality of optical carriers.
7. The double-pass optical processor of claim 1 , further comprising a beam steering device having a first steering surface and a second steering surface, wherein the lens system has an optical axis and the reflective surface of the modulator is arranged to be parallel to the optical axis, and wherein the first steering surface is arranged to project the plurality of optical carriers onto the reflective surface at 45 degrees to the normal, and the second steering surface is arranged to form a 135-degree angle relative to the first steering surface and to project the plurality of optical carriers along the optical axis.
8. A method of processing a plurality of optical carriers of an optical signal, comprising:
spatially separating the plurality of optical carriers;
projecting the plurality of optical carriers onto a reflective optical modulator
a first step of modulating and reflecting the plurality of optical carriers using the reflective optical modulator;
reflecting the plurality of optical carriers back to the reflective optical modulator; and
a second step of modulating and reflecting the plurality of optical carriers using, the reflective optical modulator, whereby the plurality of optical carriers are modulated twice by the reflective optical modulator.
9. The method of processing in claim 8 , further comprising collimating the signal prior to the step of spatially separating.
10. The method of processing in claim 8 , wherein the step of projecting includes applying a first positive power to the plurality of optical carriers, applying a negative power to the plurality of optical carriers, and applying a second positive power to the plurality of optical carriers.
11. The method of processing in claim 8 , further comprising a step of focusing the optical carriers, such that the first step of modulating and reflecting is performed on the optical carriers when they are focused.
12. The method of processing in claim 11 , wherein the step of modulating and reflecting is achieved by a surface of a diffractive, reflective optical modulator.
13. The method of processing in claim 8 , further comprising a step of transmitting the carriers through a quarter-wave plate intermediate the first step of modulating and reflecting, and the step of reflecting the plurality of optical carriers back to the reflective optical modulator.
14. The double-pass optical processor of claim 1 , further comprising a quarter-wave plate disposed intermediate the modulator and the reflector.